document resume ed 129 585 se 021 157 · document resume. ed 129 585 se 021 157. title introduction...

DOCUMENT RESUME

ED 129 585 SE 021 157

TITLE Introduction to Sonar, Naval Education and Irainin(;Command. Revised Edition.

INSTITUTION Naval Education and Training Command, Pensacola,Fla.

REPORT NO NAVEDTRA-10130-CPUB DATE 76NOTE 223p.; Photographs and shaded figures may not

reproduce wellAVAILABLE FROM Superintendent of Documents, U.S. Government Printing

Office, Washington, D.C. 20402 (Stock Number0502-LP-050-6510; No price quoted)

EDRS PRICEDESCRIPTORS

IDENTIFIERS

ABSTRACT

MF-$0.83 HC-$12.71 Plus Postage.Acoustics; *Inservice Education; *InLicructionalNi..terials; *Marine Technicians; Military Personnel;Military Training; *Physics; Science Education;*Technical Education; Textbooks*Navy; *Sonar

This Rate Training Manual (FTM) and NonresidentCareer Course form a self-study package for those U.S. Navy personnelwho are seeking advancement in the Sonar Technician Rating. Among therequirements of the rating are the abilities to obtain and interpretunderwater data, operate and maintain upkeep of sonar equipment, andinterpret target and oceonographic data. Designed for individualstudy and not formal classroom instruction, this book providessubject matter that relates directly to the occupationalqualifications of the Sonar Technician Rating. Included in the bookare chapters on the physics of sound, the bathythermograph,principles of sonar, basic fire control, test equipment and methods,and security. (Author/MH)

***********************************************************************Documents acquired by ERIC include many informal unpublished

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N AND TRAINING COMMAND. ,

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TRAINING MANUAL

SIDENT CAREER COURSE

EDTRA 10130-C

1.

7.

PREFACE

This Rate Training Manual and Nonresident Career Course (RTM/NRCC)form a self-study package for those personnel who are seeking advancementin the Sonar Technician Rating. This package will enable these personnel tohelp themselves fulfill the requirements of the rating. Among theserequirements are the abilities to obtain and interpret underwater data foroperational use; operate and maintain upkeep of sonar equipment; performas a member of an antisubmarine (A/S) attack team; interpret target andoceanogaphic data; perform intermediate maintenance on sonar and alliedequipment; and to work with records and reports associated with sonaroperations.

Designed for individual study and not formal classroom instruction, theRTM provides subject matter that relates directly to the occupationalqualifications of the Sonar Technician Rating.

The NRCC provides the usual way of satisfying the requirements forcompleting the RTM. The set of assignments in the NRCC includes learningobjectives and supporting items designed to lead students through the RTM.

This training manual and nonresident career course was prepared by theNaval Education and Training Program Development Center, Pensacola,Florida, for the Chief of Naval Education and Training. Technical assistancewas provided by Fleet Antisubmarine Warfare Training Center Pacific, SanDiego, California; Naval Submarine School, Groton, Connecticut; NavalUnderwater Sound Lab, New London, Connecticut; and Naval IntelligenceSupport Center, Washington, D.C.

Revised 1976 Stock Ordering No.0502-LP-050-6510

Published byNAVAL EDUCATION AND TRAINING SUPPORT COMMAND

UNITED STATESGOVERNMENT PRINTING OFFICE

WASHINGTON, D.C.: 1976

3

THE UNITED STATES NAVY

GUARDIAN OF OUR COUNTRYThe United States Navy is responsible for maintaining control of the seaand is a ready force on watch at home and overseas, capable of strongaction to preserve the peace or of instant offensive action to win in war.

It is upon the maintenance of this control that our country's gloriousfuture depends; the United States Navy exists to make it so.

WE SERVE WITH HONOR

Tradition, valor, and victory are the Navy's heritage from the past. Tothese may be added dedication, disciphne, and vigilance as the watchwordsof the present and the future.

At home or on distant stations we serve with pride, confident in the respectof our country, our shipmates, and our families.

Our responsibilities sober us; our adversities strengthen us.

Service to God and Country is our special privilege. We serve with honor.

THE FUTURE OF THE NAVY

The Navy will always employ new weapons, new techniques, andgreater power to protect and defend the United States on the sea, underthe sea, and in the air.

Now and in the future, control of the sea gives the United States hergreatest advantage for the maintenance of peace and for victory in war.

Mobility, surprise, dispersal, and offensive power are the keynotes ofthe new Navy. The roots of the Navy lie in a strong belief in thefuture, in continued dedication to our tasks, and in reflection on ourheritage from the past.

Never have our opportunities and our responsibilities been greater.

li

CONTENTS

CHAPTER Page

The Sonar Technician1

2. History and Development of ASW 15

3. Physics of Sound 35

4. Bathythermograph 58

5. Bearings and Motion 71

6. Principles of Sonar 85

7. Basic Fire Control 109

8. Con .munications 127

9. Test Equipment; Test Methods; Maintenance 141

10. Security 162

APPENDIX

1. Glossary 173

1NDEX 178

Occupational Standards 185

Nol.c.esident Career Course Follows Occupational Standards

5

III

CHAPTER 1

THE SONAR TECHNICIAN

A substantial force of conventional indnuclear-powered submarines, many of themcapable of launching nuclear missiles, representsa potential threat to our country's security and acontinuing challenge to our Navy'santisubmarine forces.

To meet this challenge. U.S. Navy ships andsubmarines continually conduct exercises inantisub marine warfare (ASW ) operations,revising tactics and evaluating new methods andequipment used for detecting and destroyingenemy underwater craft. Destroyers. frigates,and cruisers are our main antisubmarine (A/S)surface vessels. They provide protection againstsubmarines for major surface ships by forming asonar screen around the ship. Upon detection ofa submarine trying to penetrate the screen. theA/S vessel initiates an attack, and the main bodyturns away from the contact area. Our ownsubmarinesparticularly nuclear-powered typeswith t heir generally superior detectionequipmentplay an equally important role isASW. They are capable of selecting the depththat provides the best underwater detectionco nd i t io ns. Additionally. they have theendurance to conduct surveillance operationsover wide ocean areas.

The Sonar Technicianwhether on asubmarine or a surface shipis an indispensablecontributor to our nation's defense. The primarytask of all sonar personnel is to provideunderwater data for operational use.

In relation to that task. severalresponsibilities are applicable to all branches ofthe rating. All Sonar Technicians must be able tooperate the sonar equipment installed on theirparticular ships. This responsibility includesmanipulation and interpretation of data derivedfrom sonar equipment. fire control equipment

6

(as applicable), and associated gear. They musialso be able to perform both operational andpreventive maintenance on the equipment theyoperate. This training manual is designed to heiryou meet the professional qualifications foradvancement to Third Class Sonar Technician.The most sensible approach to your studies is tofirst understand the general makeup of the text.This book is a self-study manual written to helpyou become a Sonar Technician with the leastpossible outside assistance. To aid you in thisrespect, chapters with related subject matter aregrouped together to make studying easier.

Even though there always is the temptationto skip the front matter of a book and gct onwith studying the text, this practice is a costlyshortcut and should be avoided. If you skimmedthrough the front matter of this training manualto get on to chapter I . go back, now read thatmaterial.

The table of contents gives you an overallpicture of the subject matter covered in thismanual. By using it, you can locate a generalsubject, such as underwater sound equipmentfor submarine detection and navigation. Thepreface tells you the purpose of the manual,who wrote it, and who provided technicalassistance.

While you are studying this manual, you willfind the index at the back of the book atime-saving reference. By checking the index,you can locate specific data about a particularsonar set or piece of sonar equipment. It isactually an alphabetical list of the importantpoints or keywords in this book, along with thepage(s) where each subject is discussed.

Each chapter has been prepared to satisfythe latest change in the Manual of Nary EnlistedManpower and Persomzel Classifications and

INTRODUCTION TO SONAR

Occvnational Standards, NAVPERS 18008-D,.and covers only the occupational (professional)qualifications, not the military requirements.

The remainder of this chapter gives

information calculated to help you in workingfor advancement. It is highly recommended that

you study this chapter carefully before youbegin intensive study ot' the remainder of the

manual.

ENLISTED RATING STRUCTURE

Within the enlisted rating structure, twotypes of ratingsgeneral and serviceare ofconcern to you. These ratings are applicable to

both the Regular Navy and Naval Reserve.GENERAL RATINGS identify broad

occupational fields of related duties and

functions. Some general ratings include serviceratings; others do not.

SERVICE RATINGS identify subdivisionsor specialities within a general rating. Althoughservice ratings can exist at any petty officer

level, they are most common at the P03 andP02 levels. As of I

March 1975, the ST ratingwas split into service ratings up through E-8.

SONAR TECHNICIAN RATING

Navy ratings are divided into 12 groups, withthe ratings in each group being occupationallyrelated. Sonar Technician is a general rating ingroup I. called the deck group. Following is an

outline of the tasks applicable to the divisions of

the Sonar Technician rating at the second andthird class levels.

Surface Sonar Technician (STG)

The Surface Sonar Technician operates

installed sonar equipment. He must be able tomanipulate, control. evaluate, and interpret dataderived from surface passive and active sonarequipment, oceanographic equipment,associated surface auxiliary sonar equipment,

and surface fire control equipment. He also must

be able to perform organizational and

intermediate maintenance on surface sonar and

allied equipments. As STG 3 or 2. your billets in

Inust cases will be limited to the sonar gang ()t-

an operating surface ASW ship such as a

destroyer.

Submarine Sonar Technician (STS)

'Fire Submarine Sonar Technician operatesinstalled sonar equipment. He must be able tomanipulate, control, evaluate. and interpret dataderived from submarine passive and active sonar

equipment, oceanographic equipment, and

associated submarine auxiliary sonar equipment.He also must be able to perform organizationaland intermediate maintenance on submarine

sonar and allied equipments. As STS 3 or 2,

your billets in most cases will be limited to thesonar gang of an operating submarine.

REWARDS AND RESPONSIBILITIESOF ADVANCEMENT

Advancement brings both increased

responsibilities and increased rewards. You

should start looking alitad and considering theresponsibilities and rewards right now while you

are preparing for advancement.By now, you should be aware of many of

the advantages of advancement: higher pay,greater prestige, more interesting and challengingwork, and the satisfaction of getting ahead inyour chosen career. You will also discover thatone of the most enduring rewards of

advancement is the personal satisfaction youfind in developing your skills and increasingyour knowledge.

The Navy also benefits by your advancementsince highly trained personnel are essential tothe functioning of the Navy. Each advancementincreases your value to the Navy in two ways.First. you become more valuable as a technicalspecialist in your own rating. Second, youbecome more valuable as a man who cansupervise, lead, and train others and thus makefar-reaching and long-lasting contributions to the

Navy.

LEADERSHIP RESPONSIBILITIES

The extent of your contribution to the Navydepends, in large measure, upon your willingness

7

Chapter I 111k SONAR TrCIINICIAN

and ability to accept increasing responsibilitiesas you advance. When you assume your POduties, you must accept a certain amount ofresponsibility for military matters as wen as foroccupational requirements of the ST rating.

Military Leadership

Your military leadership responsibilities areabout the same as those of petty officrs inother ratings since every petty officer is amilitary person before becoming a technicalspecialist. Your responsibilities will extend bothupward and downward. Senior petty officersand junior enlisted personnel alike will expectyou to translate general orders into detailed,practical, on-the-job language that can beunderstood and executed by even relativelyinexperienced personnel. In dealing with yourjuniors, it is up to you to see that they performtheir work properly. At the same time, you mustbe able to explain to your leading PO anyimportant needs or problems of these men.

Although some broad aspects of militaryleadership are included in this text, the trainingmanual is not designed to give you extensiveinformation on military requirements foradvancement to petty officer third or second.Material covering these requirements is found inM i I itary Require/news for PO 3 & 2 ,NAVEDTRA 10056 (current edition), andshould be studied carefully.

Technical Leadership

Your responsibilities for technical leadershipare special to your rating and are directly relatedto the nature of your work. The dual role ofoperating and maintaining the ship's sonarsystems is a job of vital importance. It requiresan exceptional kind of leadership ability thatLun be developed only by personnel who have ahigh degree of technical competence and a deepsense of personal responsibility. Even if you arefortunate enough to be serving with highlyskilled and well-trained sonar personnel, you willfind that training is -till necessary. In thisrespect. you will be expected to assist in thetraining of lower rated men for advancement.Also, if some of the skilled men are transferred,

3

8

inexperienced or poorly trained men may heassigned to replace them. In such a

circumstance, your skill and ex pe rien cc must heused to help bring these men up to the standardof those they replaced.

KEEPING UP WITHNEW DEVELOPMENTS

You are responsible for keeping up with newdevelopments within the Navy. Practicallyve rythi in the Navy is subject to

changepolici es , p ro cedures, cquipmen t,publications, systems, and so on. As third classand even more as second class, you must makeevery effort to keep yourself informed of allchanges and new developments that might affectyour rating or your work.

Some changes will be called directly to yourattention, but you must look for others. Try todevelop a special kind of ;lertness for newinformation. Above all, keep an open mind onthe subjcet of new sonars and associatedequ i pm e n t. Openmindedness is especialiyimportant in the Sonar Technician rating becausethe Navy, in an effort to keep up with modernmodern advances in submarine development, isexperimenting constantly with new detection,fire control, and weapons systems.

WORKING WITH OTHERS

As you advance to third class and then tost,:ond class, you will be taking a greater part inplanning for the training of ASW personnel onyour ship. At times, this training will affect alarge number of personnel not in your divisionor even your department. It becomesincreasingly important, therefore, to understandthe duties and responsibilities of personnel inother ratings. The more you know about relatedratings, the more complete and comprehensivewill be your training plansespecially those thatrequire an interdivisional effort to achieve theirgoals.

Communicating Effectively

As your rcsponsibilities for planning withothers increase, so also must your ability tocommunicate clearly and effectively. The bas':.:

IN TRODUC HON TO SONAR

requirement tor criCCtiVC C01111111111liattollkn OW ledge of your own language. Uscappropriate language in speaking and in writing.Remember that the basic purpose of ;ill

communication is understanding. To lead .supervise, and train other men. you must be ableto speak and write in such a wa, that they canunderstand exactly what you mean.

A second requirement for effectivecommunication in the Navy is a soundknowledge of the "Navy way- of saying things.Some Navy terms have been standardized for thepurdose of ensuring efficient communication.When a situation calls for standard Navyterminology, use it.

Still another requirement for effectivecommunication is precision in the :Ise oftechnical terms. A command of the technicallanguage of the Sonar Technician rating willenable you to receive and convey irformationaccurately and to exchange ideas with others.Proper use of technical terms is particularlyimportant when you are dealing with lowerrated mencarelessly used technical terms willconfuse an inexperienced man. A person who(loos not understand the precise meaning ofterms used in connection with the work of hisown rating is handicapped when he tries to readofficial publications related to his work. He isalso at a disadvantage when he takes the writtenexaminations for advancement.

Increasing Retention

Have you ever wondered why we have to gointo a port and starboard sonar watch, duringoperating periods, or why our sea duty tours areso long? Let's face facts: Naval operations arenot going to change very much in the nearfuture. In fact, due to budget cuts, we willprobably be doing the same job with fewer men.Therefore, retention of the lower rated SonarTechnician has become a critical factor and wemust direct our attention toward this very realproblem.

The Navy recognizes the problem and hasinstituted many new "People Program:-designed to humanize the Navy effort,highlighting the individual within the group.

4

I hese prolh.ainS Mt.' designed to increase moraleott ;i large scale with increased retention as thelogical by-product.

The Navy has taken great strides in improvingits living standards. The food is better and eventhe pay has become reasonable. These factorsfulfill a man's basic survival and security needs,but we must use other motivating factors also topromote retention. By learning to recognizepositive motivation factors and to use themcorrectly, we will obtain better job performanceand our subordinates will realiz.2 moresatisfaction from their jobs. Wt.. are all capable ofperforming if motivated properly.

No one has all of the answers to effectivemanagement. However. the highest degree ofe Ile c t iveness is realized when leadershiptechniques are based upon the following list ofassumptions:

I. People a re not by nature lazy,indifferent. uncooperative, or uncreative. Workis ;is natural as play or rest.

2. Tight controls and threats of punishmentare not the only means of getting men to work.Men will exercise self-direction and self-controltoward objectives to which they are committed.

3. Every man must have a meaningful job.Without meaningful work he is bored anduseless.

4. Man is a growing, learning animal whocraves recognition.

5. Most men learn to accept and to seekresponsibility.

6. The avciage man's intellectual potentialsare only partially utilized. Most are capable of ahir4h degree of imagination, ingenuity, andcreativity.

7. Man by his nature is gregarious. One ofhis basic urges is his desire to be an integral partof some group. He must feel that he is animportant, contributing member of the group.

Do we, as leaders, really consider the needsand desires of our subordinates'? Most of us havepreconceived ideas of what a person's needs are.We try to compare a subordinate's reactions tovarious management techniques, and to what wethink our own reactions would be under similarcircumstances. Thus, we set up a modelsubordinate, usually based upon ourselves, and

9

( haith I I III ti( )N \l I I ( IINI( I 1N

decide to maikige ,iccordinu IL) our moulersdesiies, treating everyone the same. kilt this isentirely the wrong iipproach since no tW0individuals are alike, We each re,ki differently todi! ferent situations, Therefore. a good leadermust know and understand his men and beflexible enough to zidjust Ins mangementtechn iques according to each uI i \ id

Flexibility is a kev .0 StIcicsSrul le;RIcrship.

Job assignments should he planned tochallenge the ability of each Mdividual. Whcllman masters one task. make his next one just alittle more difficult. ke.7ping in mind that. formotivating purposes. succeeding is better thansuccess. For e\arllple. turn-..ounting is a greatchallen12e to a new ST striker: liud. once hebecom -7,Ticient. Ids joh must be changed, Ifnot. lit ., become bored and Ins efficiencv willdrop. If it's not possible to change his job rightaway. then encourage competition among thewatehstanders. Use any challenge you can thinkof to keep him interested, and his highperformance should continue until Ilk job canbe changed.

Each subordinate must be assignedresponsibility no matter how large or small theresponsibility. We could Illake many c,uanges inthis area. For example. in most compartments. acard is posted on the bulkhead designating theman responsible for that comparment.Normally. the designated man is a son,or pettyofficer. Let's change that. Assign theresponsibility for the appearance of thecompartment to the compartment cleanerhimself. When he realizes that he, and not hissenior petty officer, will have to answer for thecompartment if it is not ship-shape. he will takemore interest and will do a better job. He willalso work harder for another reason: he knowsthat when he does a good job, he will receive the"well done- himself'.

Many of the factors used to motivate anin(Iividual can also be used to motivate a group.Certainly, a good attack team must function as agroup. Some sonar controls are manned bygroups and others are manned by "bunches ofindividuals.- To be effective, all of the efforts ofyour team must be group efforts for theaccomplishment of goup goals. Competition

10

within thc group should be encouraged. :111

operator rai s great pride in the tact that he \v;1.1IrsI iL detect ;I distant target. Likewise.

competition \\ ith ot her groups can he stimulating.m)11.1r gang can 1.1",!ll re the solution to ally

111.111cll\criv board problem quicker than anyQuartermaster in thc

Whenever po:sible. group &visions shouldbe en CO ii rdgcil. For example. Jur* a

pre-exercise briefing. why not ask the group foropinions? -How do you think we should handlet Ids part of t he exercise. JoIles? Listen to yourmen and respect their opinions. -I hey may conicup with a good idea that you hadn't thought of.L.\ery man will naturally work harder toward anuhjcctic if lue takes part in making the decisionbecause he now has a personal interest in thetask.

-Fhese are some of the ideas that can beemployed to improve individual and groupperformance. Certainly. there are many others.-Flue important thing is that we. as leaders. mustconsider morale and retention. which gohand-in-hand. two of our most importantresponsibilities. We should occasionally examineour leadership techniques aid keep an openmind for new and useful methods. -Flue newNavy management trend i toward a softera pproiuc h . re co gn izi ng individual needs.However. the strong, stern approach is stillavHlable for use when necessary. The next fewye;,rs are going to be very challenging to all of usin the naval service. C'hallenge is our lifeblood,the driving force that keeps us going. AdmiralHake- once said--"Ther: are no great men.Great men are just normal men who are forcedto the meet the greatest challenge.-

STUDYING FOR THE TEST

-Flue Sonar Technician, like hiscontemporaries in other ratings. normally hasaccess to every publication used as referencematerial for the questions contained on Insadvancement-in-rating examination.

Trying to read aud study every manual orpublication on sonar is a waste of time andeffort. We each have a saturation point wiehmost certainly would be exceeded if we tried to

IN I RoD1( 1ION 0) SoNAR

st OTF,111illr. I h )1VC1 CI. a pamphletprod need which indlcates exactly whichreference material is used in writing the exam.This p,itilphlet, fOr AdvancementStmly, N AV I'DTRA I 0052 (current edition), kavailable at your Information ;Ind EducationOffice.

The liibli(wraphy is an important referencewhen preparing for :tdvanl....enient. It is based onthe Manual of Nary baistra manpowerPerswinel (kcsilicatimis and OccupationalStandards, NAVPERS I 8068 (current edi(ion),nid lists the training manuals and otherpublications prescribed for use by all personnelconcerned with advancement-in-rate training andwith advancement examination writing. Thus.the Bibliogra[hy provides a working list ofmaterial for enlisted personnel to study inpreparation for advancement examinations, andit's the same list used by the item writers at theNaval Educa tion and Training ProgramDevelopment Center.

The first few pages of the pamphlet showthe military requirements references whichapply to all ratings. This part of theBibliography is of special importance at theE4/E5 levels itecause separate examinations onmilitary subjects are given locally at those ratelevels. The remainder of the booklet containsreference listings by ratings, using tlycfive-columr, format shown in figure I-I.

Column ( 1) Ratings. The names andabbreviations of both service and generalratings are contained. All of the referencesfor Sonar Technician are grouped togetheron one list covering one or more pages.

Column (2) Publication Titles. Titles andapplicable parts of Rate Training Manualsand other publications are shown in thiscolumn. Notice that, when only certain partsof a book apply as references for a particularrate. just those parts (paratuaphs ofchapters) arc listed. (See fig. I-I.)

Column (3) Text Identification Numbers.This column identifies the references morespecifically. The publication and

6

N VP11:8 NAVI'D I KA inunhci, !Hied .tlethe most lecent edittons and 111,l \ II,uch N:\\A mill A editIon.

C01111111' ( ) NoIll.e!,1(1(.11 I CarATidentification Numbers.NAVPERS/NAVED IRA number(s) of thecourses covering subject matter of anyprescribed text(s) described iii columns 2and 3 are listed. In LI few cases. compietionof the collrtie is mandatory.

Column (5) APPlicabl'-' Rat' L'vds. Fs"'ntfor training manuals that are mandatory. thelowest rate level for which a publication isapplicable is listed in this column. If apublication is mandatory'. then AI a the ratelevels for which it is mandatory are shown.Note that, as pointed out in the Manual ofVa IT Enlisted Manpower and PersonmlClassdications and Occupational ,Ytandards,NAVPERS 18068. all higher pay grades maybe held responsible for the materialcontained in publications listed ('or lowerrates in their paths of advancement.Asterisks which appear throughout thelistings indicate the Rate Training Manualsor Nonresident Career Courses whosemandatory completion is specified by theAdvancement Manual.

The rate training manuals are based on theprofessional and military quals from the Manualof Navy Enlisted Manpower and PersonnelClassifications and Occupational Standards. Witha few exceptions, sufficient information ispresented in these manuals to cover every qual.Obviously a qual like "encode and decodetactical signals" cannot be realistically covered.Nor can a Secret qual be covered in aConfidential or unclassified manual. For thesetypes of quals you have to go to otherpublications for the information. TheBibliography tells you where to look.

This rate training manual plus either theSTG or STS manual and Military Requirementsfor PO 3 & 2 cover the majority of E4 and ESST quals. Bibliography (NAVEDTRA 10052.current edition) references cover those qualsthatcannot be adequately covered by these twomanuals.

I

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7

1 2


N AVEDT RA PUBLIC AT ION S

Some of the NAVEDTRA publications thatyou will need to study or refer to as you preparefor advancement have been discussed earlier inthis chapter. Some additional publications thatyou will find useful are listed here.

Tools and Their Uses, NAVEDTRA 10085(current edition)

Basic Electricity, NAVEDTRA 10086(current edition)

Basic Electronics, Vols. 1 and 2,NAVEDTRA 10087 (current edition)

Servicing Techniques for Trans' torized andPrinted Circuits, NAVEM RA 38001(current edition)

NAVSEA (FORMERLY NAVSHIPS )PUBLICATIONS

Several publications issued by the Naval SeaSystems Command will be of interest to you.Although you do not need to know everythingthat is given in the publications mentioned here,you should have a general idea of where to findinformation in NAVSEA publications.

NAVSEA Technical Manual

The Naval Ships Technical Manual (nowNA VSEA Technical Manual), NAVSHIPS0901-000-0000, is the basic doctrine publicationof former Naval Ship Systems Command. Themanual is kept up to date by means of quarterlychanges. All copies of the manual should have allciianges made in them as soon as possible afterthe changes are received.

Naval Sea Systems Co mmand Jo urnal(formerly, Technical News)

The NSSC Journal, a monthly technicalpubli ca t i on, contains current unclassifiedinformation on all aspects of shipboard problems.The magazine is particularly useful because itpresents information that supplements andclarifies articles in the NAVSEA Technical

8

1 3

Manual and because it contains data on newequipment, policies, and procedures.

MANUFACTURER'STECHNICAL MANUAL

When new sonar equipment is purchased bythe Navy, the company manufacturing thatequipment is normally tasked with providing amanufacturer's technical manual (instructionbook). These instruction books are then assignedNAVSEA numbers by the Navy. For example:Sonar communication set AN/BQC-I B, IC wasapproved by the Navy in September 1964. TheDYN A-EMPIRE, INC. submitted amanufacturer's technical manual and it wasassigned the NAVSHIPS number 95728. A largechange was made to the manual in March 1968,and the manual was reassigned NAVSHIPSnumber 0967-932-2011. These manuals provideall of the technical information for a given pieceof sonar equipment and are indispensable to theSonar Technicain maintaining that equipment.

EIBs AND EIMBs

The Electronics Information Bulletin (EIB)is a b i we ekly au thoritative publicationcon taining advance information on fieldchanges, installation techniques, maintenancenotes, beneficial suggestions, and technicalmanual distribution. Articles of lasting interestare later transcribed into the ElectronicsInstallation and Maintenance Book (E IM B),except for field changes and corrections topublications, which subsequently are reproducedand stocked at NPFC, Philadelphia. These twopublications are essential beczuse of the advanceinformation and the reference informationavailable to the sonar maintenance technician.

PUBLICATIONS PROMULGATEDBY CNO

The following publications series aresponsored by CNO.

COMTAC Series

The term COMTAC is a label assigned tothat group of nonregistered communication and

Chapter 1THE SONAR TECHNICIAN

tactical publications which CNO has designatedto be part of every command's allowance ofrequired publications. The followingpublications are included in the COMTAC series.

Naval Warfare Publications (NWPs)

Naval Warfare Information ,tions(NWIPs)

Fleet Exercise Publications (EXPs)

Allied Tactical Publications (ATPs)

Allied Exercise Publications (AXPs)

USN Addenda to Allied Publications

Miscellaneous Allied Publications

Registered Publications Series

A few of the publications sponsored by CNOare distributed through the RegisteredPublications System (RPS), These publicationsmust be accounted for, safeguarded, extracted,and destroyed in accordance with applicableinstructions and directives published by RPS,supplemented where necessary by individualletters of promulgation. Tactical publications inthe RPS are as follows:

ATP-6 Allied Doctrine of MineCountermeasures

ATP-24 Tactical Instructions for Conduct ofMine Countermeasures

AMP-5 Mine Identification and DisposalManual

AXP-5 NATO Experimental Tactics andAmplifying Tactical Instructions

PUBLICATIONS PROMULGATEDBY COMNAVCOMM

The following publications are within thecognizance of Commander NavalCommunications (COM NAVCOMM):

Allied Communication: Publications (ACPs)

U.S. Naval Communications Instructions(DNCs)

Joint Publications (JANAPs) 1 1

9

U.S. NAVY TACTICALDOCTRINE PUBLICATIONS

The titles of all publications and thedescriptive paragraphs appearing here and undersubsequent headings in this section areuncla ssi fied . The classification of eachpublication is indicated at the end of thedescriptive paragraph. Those publicationsmarked with an asterisk are of particular interestto the STS.

NWP 0 TACTICAL DOCTRINEPUBLICATIONS GUIDE includes the periodicreview program and procedures, publicationprocurement, a general summary of eachpublication, and guidance for the operation of aCOMTAC publication library. (Unclassified)

NWIP 1-4 EXPERIMENTAL TACTICScontains experimental tactics and proceduresand assigns their evaluation. If accepted by fleetevaluation, the material is transferred to theappropriate publication in the NWP series.(Confidential)

NWIP 11 -20 MISSIONS ANDCHARACTERISTICS OF U.S. NAVY SHIPSAND AIRCRAFT contains information on U.S.Navy and Coast Guard ships and aircraft, andillustrations of representative types. It includesthe missions, characteristics, armament, andendurance of the various ship classes, andperformance data of aircraft currently in service.(Confidential)

NWP 1 6 BASIC OPERATIONALCOMMUNICATIONS DOCTRINE establishesthe basic doctrine, policies, and principlesgoverning operational communications.

*USN ADDENDUM TO ATP 28(REPLACES NWP 24 SERIES) presents thebasic concepts and principles of ASW operationsand amplifies the ASW chapters in ATP 1, Vol.I. (Confidential)

*NWP 3 3 ELECTRONIC WARFAREprovides doctrine and procedures for electronicwarfare and includes information on electronic


countermeasures, counter-countermeasures, andacoustic warfare. It also provides information ontypes of electronic equipment and guidance foremployment of electronic warfare in navaloperations. (Secret)

NWP 37 NATIONAL SEARCH ANDRESCUE MANUAL is a joint publicationcoordinated by the U.S. Coast Guard. Itprovides the various military forces and civilianagencies with a standard procedure for searchand rescue. (Joint service publication) (Sponsor:Coast Guard) (Unclassified)

USN ADDENDUM TO NWP 37,SUBMARINE DISASTER SEARCH ANDRESCUE OPERATIONS, outlines proceduresparticularly applicable to the search phase ofpeacetime submarine disaster search and rescueDperat ions. (Unclassified )

*FXP 1 SUBMARINE ANDANTISUBMARINE EXERCISES establishes:actics and procedures for conducting submarine;xercises with criteria for evaluating results.:Confidential)

FXP 3 SHIP EXERCISES provides exercises'or all types of surface ships and guidance toxercise observers in evaluatin2 the exercises.Confidential)

J.S. COMMUNICATIONS'UBLICATION

JANAP 119 JOINT VOICE CALL SIGN300K contains the voice call signs of all U.S.ctivities. (Confidential)

4ATO/ALLIED TACTICAL)0CTRINE PUBLICATIONS

ATP 1 (VOL. I) ALLIED MARITIME'ACTICAL PROCEDURES contains basicianeuvering instructions, tactics, and doctrineDr all Allied navies. (Custodian: United States)7onfidential)

ATP 1 (VOL. II) ALLIED NAVAL SIGNAL,OOK contains standard maneuvering.

1 0

5

operating, and the more common administrativesignals. (Custodian: United States)(Confidential)

USN ADDENDUM TO ATP I (VOL. II),U.S. NAVAL SIGNAL BOOK, providesadditional basic material, supplementing and/ormodifying ATP 1, Vol. II, for intraservice use bythe U.S. Navy when operating separately fromthe other Allied navies. (Confidential)

ATP 3 ANTISUBMARINE EVASIVESTEERING covers evasive steering byformations, convoys, an-I ships to avoid attackby submarines. It is intended for use by Alliednavies. (Custodian: United States) (Confidential)

SUPPLEMENT TO ATP 3, ZIGZAG PLANS10, 14, 15, and 17. (Confidential)

ATP 10 SEARCH AND RESCUE containsdoctrine concerning search and rescue and is theAllied version of NWP 37. An appendix containsAnnex 12 to the Convention of InternationalCivil Aviation and presents internationalstandards and recommended practices for searchand rescue. (Custodian: United Kingdom)(Confidential)

*AXP I ALLIED SUBMARINE ANDANTISUBMARINE EXERCISE MANUALestablishes tactics and procedures for evaluatingthe exercises. (Custodian: Canada)(Confidential)

AXP 2 ALLIED TACTICAL EXERCISEMANUAL contains standard seamanship,gunnery, torpedo, and miscellaneous exercisesfor use by Allied navies in training their forcesfor participation in Allied Operations.(Custodian: United States) (Confidential)

ALLIED COMMUNICATIONPUBLICATIONS

A C P 1 2 5 COMMUNICATIONSINSTRUCTION RADIOTELEPHONEPROCEDURE prescribes the basicradiotelephone procedure that shall be used forradiotelephone communications. (Custodian:United States) (Unclassified)


ACP 1 65 OPERATIONAL BREVITYcontains code words or phrases that are used forstandardization and abbreviation. The codewords are designed for speed and conciseness oftra nsmissio n . (Custodian : United Sta tes)(Confidential)

THE ADVANCEMENT EXAMINATION

All of the ST advancement examinations arewritten by an item writer at the Naval Educationand Training Program Development Center,Ellyson, Pensacola, Florida. The item writer isresponsible for constructing the 150-question STexaminations. The writer has a bank of manyitems that have been used on previousexaminations, and he will use many of the itemsfrom his bank when he comtructs anexamination. He will also write new items.

The examination questions are grouped bysubject matter into categories, or sections. The.emay be from 5 to 12 sections on a particuiartest. Each item is carefully checked andrechecked to make sure it is a valid item.

Unfortun;-:' !. tliere is an unavoidable delaybuilt into th, :unation system since theBibliography is 1....ited and distributed aboutone year in advance. For example, theBibliography for the 1974 exams was printed inthe spring of 1973. As soon as the Bibliographyis made available to him. the item writer atNETPDC begins writing the ST exams for thefollowing yeai. During this pericd of time, manychanges may be made to the referencepublications listed in the Bibliography. Thesechanges may invalidate some of the examquestions.

Ho wever, this will not affect yourexamination grade. On the day that you take theadvancement exam, the item writer at NETPDCalso takes that same test. For your benefit, hethoroughly checks every item on theexamination to make sure none are outdated.Any outdated questions that he finds will not beconsidered when the test is graded. This has thesame affect as counting all four answers correctbecause any answer you pick for an outdatedquestion is correct. Thus, you do not have toworry about test items that contain supersededinformat ion.

1 6 11

Two important restrictions are placed uponthe item writer: First, his examination mustcover all of the quals, as indicated by the Manualof Navy Enlisted Manpower and PersonnelClassifications and Occupational Standards,NAVPERS 18068 (current edition), for theparticular rate. Second, his references arerestricted to those listed in the Bibliography forA d va n cemen t Study,, NAVEDTRA 10052(current edition), or the secondary referencescontained in the references in the Bibliography.Let's say for example, that somewhere in theSTS 3 & 2 Rate Training Manual, which is listedin the Bibliography, a reference is made to apublication which is not listed in theBibliography; then that publication is also fairgame for test question material.

Many of us are led to believe that we must atleast pass each section of the test. Not so. Nonumerical grade is even assigned to each section.For profile sheet purposes, a letter is assigned toeach section to point out weak areas. Thisenables you to better prepare for the next exam.Of course, if you miss most of the questions inone section of the exam, it may pull your overallgrade down below the passing score; but it isyour overall grade that determines whether Youpass or fail, not your performance on eachindividual section of the test. Thus, your testgrade is determined by the total number ofquestions that you answer correctly and yourrelative standing among your peersnothingelse.

HOW TO QUALIFYFOR ADVANCEMENT

What must you do to qualify foradvancement? The requirements may changefrom time to time, but usually you must satisfythe following:

1. Have a certain amount of time in yourpresent grade.

2. Complete the required military and ra tingmanuals.

3. Demonstrate your ability to perform allthe PRACTICAL requirements for advancementby completing the Record of Practical Factors,NAVEDTRA 1414/1.


REQUIREMENTS ' El to E2 E2 to E.1 # E3to E

-E4to E5

E5

to E6f E6

to E7t E7

to E8f E8

to E9

SERVICE

4 mos.service-

orcomple-tion ofRecruitTraining.

b mos.as L- 2.

6 mos.as E-3.2 yearstime inservice.

12 mos.as E-4.3 yearstime inservice,

24 mos.as E-5.6 yearstime inservice.

36 mosas E-6.9 yearstime inservice.

36 mos.as E-7.8 of 12

36 mos.as E-8.10 of 15yearstime inservicemust beenlisted.SCHOOL

RecruitTraining.(C.O.,may ad-vance upto 10%of gradu-atingclass.) ..

Class Afor Pin .

DT3,PT3,

. A ME 3,

:IINI 3,

. PN 3,, FTB 3,

MT 3

......

.:. .

. .:.

.

.

-

Navy. School.

mix,. MNC.tt

yearstime inservicemust beenlisted.

PRA CTIC A LFACTORS

Locallypremredchcck-offs.

Record of Practical Factors, NavEdTra 1414/1, must becompleted for E-3 and all PO advancements.

PERFORMANCETEST . . ..

. . .

... .

:

...,,,,,_:,,

SpecifiA ratings must completeapplicable performance tests be-

fore taking examinations.ENLISTED

PERFORMANCEEVA LUAT1ON

As used by COwhen approvingadvancement.

Counts toward performance factor credit in ad-vancement multiple.

EXA MINATIONS **Locally

preparedtests.

Seebelow .

Navy-wide examinationsrequired for all POadvancements.

Navy-wide selection board.

RATE TRAININGMANUAL (INCLUD-ING MILITARYREQUIREMENTS)

.. .

.::. .:.... ..... .'.'. .. .

...

;.:.

. .

Required for E-3 and all PO advancementsunless waived because of school comple-tion, but need not he repeated if identicalcourse has already been completed. See

NavEdTra 10052 (current edition).

Nonresident careercourses andrecommendedreading. SeeNavEdTra 10052(current edition).

AUTHORIZATION CommandingOfficer NAV EDTRA PRODEVCEN

*All advancements require commanding officer's recommendation.t 3 years obligated service required for E-7, E-8, and E-9.# Military leadership exam required for E-4 and E-5.

** For E-2 to E-3, NAVEDTRAPRODEVCEN exams or locally prepared tests may be used.t t Waived for qualified LOD personnel.

Figure 1-2.Active duty advancement requirements.

1 2 1 7


REQUIREMENTS* El toE2

E2 toE3

E3 toE4

E4 toE5

E5 toEG

Et; tori

E8' E9

TOT MEAL TIIN GRADE 4 nms. 8 mos. 0 mos. 12 mos. 24 inos.

30 mos.W i thtotal8 yrsservice

30 mos.withtotal11 yrsservice

24 mos.withtotal13 yrsservice

TOTAL TRAININGDUTY IN GRADEI 14 days 14 days 14 days 14 days 28 days 42 days 42 thiys 28 days

PERFORMANCETESTS

Specified intings must completePerformance tests before taking

applie:Wleexamination.

drill unit

ust

DRILLPARTICIR\ 'HON

Recordbe completed

Satisfactoryin accordance

fo Practicalfor

Exam

participation as a memberwith BUPERSINST 5.101).42

Factors. Na vEd'Fra 1114/1.all advancements.

of applicable course or coursesin service record.

Standard Examrequired for all Pt)advancements.Also passMilitary Leadership Examfor E-4 and E-5.

of aseries.

mPRACTICA L FACTORS(INCLUDING MILITARY

REQUIREMENTS)

RATE TRAININGMANUAL (INCLUDINGMILITARY REQUIR E-

MENTS)

Completion must be entered

Standard Exain.Selection Board.

-

EXAMINATION Standard

AUTIIORIZATION CornmandingOfficer NA V EDTHA PROD Evc EN

*Recommendation by commanding officer required for all advancemerns.4 Active duty periods may be substituted for training duty.

Figure 1-3.--Inactive duty advancement requirements.

1 8


4. Be recommended by your commandingofficer after the petty officers and officerssupervising your work have indicated that theyconsider you capable of performing the duties ofthe next higher rate.

5. Demonstrate your KNOWLEDGE bypassing written examinations on theoccupational and military qualificationstandards for advancement.

Some of these general requirements may bemodified in certain ways. Figure 1-2 gives amore detailed view of the requirements foradvancement of active duty personnel; figure 1-3gives this information for inactive dutypersonnel. Remember that the qualifications foradvancement can change. Check with yourdivision officer or training officer to be sure thatyou know the most recent qualifications.

Advancement is not automa tic. Even thoughyou have met all the requirements, includingpassing the v :n examinations, you may notbe able to "s:.

. on the crow" or "add a stripe."The number of men in each rate and rating iscontrolled on a Navywide basis. Therefore, thenumber of men who may be advanced is limitedby the number of vacancies that exist. When thenumber of men passing the examination exceedsthe number of vacancies, another system mustbe used to determine which men may beadvanced and which may not. The system usedis the "final multiple" and is a combination ofthree types of advancement systems.

Merit rating systemPersonnel testing systemLongevity, or seniority, system

The Navy's system provides credit forperformance, knowledge, and seniority; and,while it cannot guarantee that any one personwill be advanced, it does guarantee that all menwithin a particular rating will have equaladvancement opportunity.

A change in promotion policy, starting withthe August 1974 examinations, changed thepassed-but-not-advanced (PNA) factor to the highquality bonus point (HQP) factor. Under thispolicy, a man that passed the examination, butwas not advanced, can gain points towardpromotion in his next attempt. Up to threemultiple points can be gained in a singlepromotion period. The points can then beaccumulated over six promotion periods up to amaximum of 15. The addition of the HQPfactor, with its 15-point maximum, raises thenumber of points possible on an examinationmultiple from 185 to 200. This gives theexaminee added incentive to keep trying forpromotion in spite of repeated failure to gain astripe because ot' quota limitations.

All of the above information (except theexamination score and the HOP factor) issubmitted with your examination answer sheet.After grading, the examination scores for thosepassing and the HQP points are added to theother factors to arrive at the final multiple. Aprecedence list which is based on final multiples,is then prepared for each pay grade within eachrating. Advancement authorizations are thenissued, beginning at the top of the list, for thenumber of men needed to fill the existingvacancies.

METRIC SYSTEM

The Metric System Single-Subject Training Manual and its associatedOCC-ECC form a self-study package (NAVEDTRA 475-01-00-75) to train Navypersonnel in conversion from the U. S. Customary System to theInternational System. Order the SSTM by stock number 0507-LP-475-0000from NPFC, Philadelphia, and the OCC-ECC by NAVEDTRA 475-01-00-75 fromthe NAVEDTRAPRODEVCEN, Ellyson, Pensacola, Florida.

1 9

14

CHAPTER 2

HISTORY AND DEVELOPMENT OF ASW

During World War II, submarines sentmillions of tons of shipping to the bottom. Earlyin the war, England's lifelines were nearlystrangled by German .-,ubmarines. Americansubmarines played a large role in the defeat ofJapan by sinking nearly all her merchant marine.Obviously, the submarine is a potent weapon,requiring equally effective countermeasures. TheUnited States and Great Britain were uccessfulin developing equipment, weapons, and tacticsthat enabled the destruction of the Germansubmarine force. Japan, however, never was ableto develop an effective defense against oursubmarines.

Since World War II the submerged enduranceof the submarine has become sufficient to causedifficulty in locating it. The problem increases asthe submarine goes constantly faster, deeper,and stays down longer. To cope with themodern submarine, we now have betterdetection devices, more modern weapons, andnewer ships; but the battle for supremacy is anever-ending one.

THE SUBMARINE

All Sonar Technicians are concerned withthe hunt for and destruction of enemysubmarines. It is especially important, therefore,that you know the capabilities of enemysubmarines, and know them well. Innumerablequestions will come to you over a period of timeor after a course of events in antisubmarinewarfare (ASW) operations: How fast can asubmarine dive or turn? How does thesubmarine use depth? What is the submarine'stop speed when submerged? Because this text isunclassified, many of the answers are of a

15

2 0

tzeneral nature. In your studies, though, you willlearn many details about submarinecharacteristics and tactics. Such knowledgemakes it easier for you to detect submarines andhold contact after detection. Mr-,t of this textconcerns our own submarines, but foreign naviesusually have submarines of comparable ability.

HISTORY AND DEVELOPMENT

The first successful submarine was built in1620 by Cornelius Van Drebel, a Dutchphysician. During repeated trials in the ThamesRiver, he maneuvered his craft successfully atdepths of 12 to 15 feet beneath the surface.

Various other European designers of thattime constructed submersible craft also, butthey failed to arouse the interest of any navy inan age when the potentialities of submarinewarfare were inconceivable.

Most of the early craft were wooden frames,covered with greased leather or similar material,and propelled by oars. Different methods ofsubmerging were thought of and some were eventried. One inventor's design consisted of anumber of goatskin bags built into the hull, eachconnected to an aperture in the bottom. Heplanned to submerge the craft by filling theskins with water and to surface it by forcing thewater out of the skins with a "twisting rod."Although his vessel was never built, it seems thatthis design was the first approach to the modernballast tan k. Another inventor actuallysubmerged his craft by reducing its volume as aresult ot' contracting the sides through the use ofhand vises.

Ideas were plentiful. Some of them werefanciful and grotesque, but some containedelements capable of practical application. Lack


of full understanding of the physical andmechanical principles involved, coupled with thealmost universal conviction that underwaternavigation was impossible and of no practicalvalue, kept postponing the attempt to utilize asubmarine in naval warfare during the earlyperiod.

A submarine was first used as an offensiveweapon during the American RevolutionaryWar. The TURTLE, a one-mar submersibledesigned by an American inventor named DavidBushnell and hand operated by a screwpropeller, attempted to sink a British man-o-warin New York Harbor. The plan was to attach acharv,e of gunpowder to the ship's bottom withscrews and to explode it with a time fuze. Afterrepeated failures to force the screws through thecopper sheathing of the hull of HMS EAGLE,the submarine gave up and withdrew, explodingits powder a short distance from the EAGLE.Although the attack was unsuccessful, it causedthe British to move their blockading ships fromthe harbor to the outer bay.

On 17 February 1864. a Confederate craft, ahand-propelled submersible, carrying a crew ofeight men. sank a Federal corvette that was

.

blockading Charleston Harbor. The hit wasaccomplished by a torpedo suspended ahead ofthe Confederate 11UNLEY as she rammed theUnion frigate HOUSATONIC, and is the firstrecorded instance of a submarine sinking awarsh ip.

The submarine first became a majorcomponent in naval warfare during World War I,when Germany demonstrated its fullpotentialities. Wholesale sinking of Alliedshipping by the German U-boats ahnost swungthe war in favor of the Central Powers. Then, asnow. the submarine's greatest advantage wasthat it could operate beneath the ocean surfacewhere detection was difficult. Sinking asubmarine was comparatively easy, once it wasfound: but finding it before it could attack wasanother matter.

During the closing months of World War I,the Allied Submarine Devices InvestigationCommittee was formed to obtain from scienceand technology more effective underwaterdetection equipment. The committee developeda reasonably accurate device for locating asubmerged submarine. This device was atrainable hvdrophone_ which was attached to

SO.

Figure 2-1.Guppy submarine.

16

71.1-346

Chapter 2HISTORY AND DEVELOPMENT OF ASW

the bottom of the ASW ship and used to detectscrew noises and other sounds that came from asubmarine. Although the committee disbandeda ft er World War I, the British madeimprovements on the locating device, during theinterval between then and World War II, andnamed it ASDIC after the committee.

American scientists further improved on thedevice, calling it sonar, a name derived from theunderlined initials of the words sound navigationand ranging.

At the end of World War II, the UnitedStates improved the snorkel (a device forbringing air to the crew and engines whenoperating submerged on (liesels) and developedthe Guppy (short for greater underwaterpropulsion power), a conversion of thefleet-type submarine of World War II fame. AGuppy submarine is shown in figure 2-1. Thesuperstructure was changed by reducing thesurface area, streamlining every protrudingobject, and enclosing the periscope shears in astreamlined metal fairing. Performance increasedgreatly with improved electronic equipment,additional battery capacity, and the addition ofthe snorkel.

The world's pioneer nuclear-poweredsubmarine is the USS NAUTILUS (SSN 571).(See fig. 2-2.) The NA UTILUS, commissioned inSeptember 1954, is 320 feet in length, with astandard surface displacement (SSD) of 3180tons, ard is designed for traveling faster underthe water than on the surface.

One of our fastest submarines is the USSSKIPJACK (SSN 585), figure 2-3, whose hull isa radical departure from the conventional ideaof submarine hulls. Her diving planes are on thesail, resulting in increased maneuverability.

An intensive building program for nuclearsubmarines has been in effect for several years,and many new ships have joined the fleet. TheUSS GEORGE WASHINGTON (SSBN 598) wasthe first submarine designed to launch, whilesubmerged, the POLARIS missile.

GENERAL DESCRIPTION

A submarine ranges in length from about 50feet to more than 400 feet. Diving isaccomplished by controlled flooding of ballast

2 2

71.1-571Figure 2-2.USS NAUTILUS (SSN 571).

17


Figure 2-3.USS SKIPJACK (SSN 585).

tanks. To surface the submarine. compressed airexpels the water from the tanks.

Probably the smallest submarines in theworld belomt to the ex-German SEAHOUNDclass (now in Russian possession). They are 49feet long and displace only 15 tons. Somewhatheavier, but still in the midget submarine class,are the U.S. Navy's X-I and the British SHRIMPclass. The X-1 is less than 50 feet long anddisplaces 25 tons. Boats of the SHRIMP class areslightly longer and displace 30 to 35 tons.

At the other extreme are the bulk of theU.S. Navy's submarines, including the fatestnuclear-powered submarines. Some of theseships are over 400 feet long and displace morethan 7000 tons (SSD). Others, designed forspeed and maneuverability, ar ,! not quite as longand displace less tonnage.

Some submarines can cruise in ,!xcess of 20knots submerged. A type of dies,,1 submarineused by the Germans in World War IL which is apart of the Russian fleet. can dive at a rate of

71.1-585

1-1/2 feet per second and can turn 900 in a littleover I minute, using full rudder and 5 knots ofspeed.

Propulsion

Diesel electric submarines use diesel enginesfor propulsion. when surfaced. and ftitterieswhen submerged. Nuclear-powered submarinesget their propulsion from atomic reactors.

NUCLEAR SUBMARINES.Atomic powerhas brought close to reality the dream of havinga true submarine; that is. one of unlimitedsubmerged endurance and range. The;V:1UTILUS refueled for the first time over I

year after she commenced operating. TheTRITON circumnavigated the world completelysubmerged. The .VA UTILUS an d SK:17'Epioneered exploration of the north polar seasbeneath the 1(ecap, all made possible only byii u c le r enerfty. The human factor and thequantity of' supplies that can be carried are the

18

9,3


main limitations to the endurance of modernsubmarines.

FLEET BALLISTICMISSILE SUBMARINES (SSBN)

The basic purpose for the creation of aweapons system such as the FBM (fig. 2-4) is toact as a nuclear deterrent to a general war. TheFBM is perhaps the most sophisticated andcostly weapons system in existence and iscapable of wreaking havoc on a potential enemy.

These ships are capable of high speeds, greatdepths, and prolonged submergence. Asformidable as these ships appear to be, effectivecountermeasures have been developed whichmake the FBM vulnerable to detection anddestruction. For an FBM to remain a deterrent,it must cloak itself in nearly absolute silence. Itmust patrol a given area without being detectedand must maintain the capability of detectingenemy ships over great distances.

ATTACK SUBMARINES (SSN)

The FBM is primarily designed as a threat toa nation's land areas. On the other hand,consider the dangers which the modern attacksubmarines (SSN) fhwre 2-5, pose on a nation'ssurface fleet. History has amply demonstratedthe strategic importance of the attacksubmarin. The combination of new hull designand nuclear power have made the SSN greatlysuperior to its predecessor. This superiority is sogreat that most nations have been forced todevelop newer and more effective ASWprograms to maintain the balance of power.Moreover, the primary mission of the attacksubmarine is ASW.

SUBMARINE ARMAMENT

Armament of a submarine depends on itsdesign and niission. USN attack submarines

71.1-629Figure 2-4.Ballistic missile submarine (SSBN).

2 4 19


normally carry only torpedoes and SUBROC,but they may be employed as minelayers. Fleetballistic missile submarines, depending, on type,carry 16 POLARIS or 16 POSEIDON missiles, inaddition to torpedoes. In the case of the newand larger TRIDENT submarines, the missilecomplement is 24 TRIDENT missiles. FBMs arealso equipped with torpedo tubes forself-defense.

TORPEDOES

The torpedo is a self-propelled underwaterweapon having either a high-explosive or anuclear warhead. Conventional warheads are

7410

loaded with up to 1000 pounds of IIBXexplosive.

Underwater explosion of the torpedowarhead increases its destructive effect. When aprojectile explodes, a part of its force isa bsorbed by the surrounding air. Uponexplosion of the torpedo warhead, the watertransfers ilmost the full force of the explosionto the hull of the target ship.

Guppy submarines (now in possession offorei,2n allies) are fitted with 10 tubes, 6 in thebow and 4 in the stern. Spare torpedoes arecarried in ready racks rlear the tubes. On warpatrol, a submarine of th:s type usually puts tosea with a load of 28 torp2does aboard.

Figure 2-5.Attack submarine (SSN).

20

.0"

71.128

Chapter 2-- HISTORY AND DEVELOPMENT OF ASW

Torpedoes are propelled by gas turbines orelectric motors. Turbine types have maximumspeeds of 30 to 45 knots. with an effective rangeof as much as 7-1/2 miles. Electric torpedoesusually have less speed and range than turbinetypes: but, from the submariner's point of view,they have the advantage of leaving no visiblewa ke.

Torpedoes are of the straight-running.acoustic-homing, or wire-ganded types. Thestraight-running torpedo has automatic controldevices tlmt hold it on a preset course at a presetdepth, whereas the acoustic-homing type cansteer itself toward its target. It may be eitheractive or passive. The acti ve acoustic torpedosends out pulses of sound and homes on theechoes that return from the target. Passive typeshome on the noises emanated by thc target. Thewire-guided type of torpedo is directed to thetarget by signals sent through the wire from thelaunching submarine.

Mk 37 Torpedo

The Mk 37 torpedo is an electricallycontrolled and propelled two-speed torpedowith an active-passive acoustic homing system.This torpedo, launched from submarines iseffective against either surface or submarinetargets. Some mods are wire-guided. makingthem invulnerable to several enemycountermeasures.

Mk 48 Torpedo

The Mk 48 torpedo is a high-speed.deep-running. long-range, submarine-launchedweapon used against submarines and surfaceships. Both acoustic and nonacoustic operatingmodes are available. Acou.,tic modes are active.passive, or combination. The torpedo may beoperated in the acoustic mode when used againstsurface or 'merged targets. Nonacousticoperation may be used against surface targetsonly.

Command guidance (wire link) may be usedfor both acoustic and nonacoustic shots. Thisallows the launch vessel's on-board computer toapdate torpedo guidance and control logic with

21

,the latest tactical information, thereby providingthe weapon with maximum adaptability. Thetorpedo guidance and control circuitry receiveinitial run plan instructions (preset) from thefire control system. And, after each launch, firecontrol may update initial instructions byonnmand guidance.

MINES

Navy mines are thin-cased underwaterweapons with a heavy load of high explosives.They may be laid by both aircraft and surfacecraft. but submarines are employed forminelaying when secrecy is required or when thearea to be mined is beyond the range of aircraft.Mines may be of the bottom or moored typo.Bottom mines rest on the ocean floor and arehighly effective in shallow water. Moored minesare positively buoyant. A cable, attached to ananchor on the sea bottom, holds the mine at apredetermined depth beneath the surface. Minesmay be actuated by contact with a vessel, by avessel's magnetic field, by noise, or by pressuredifferences created when a vessel passes over themine. Acoustic-, pressure-, andmagnetic-influenced mines may be set to permitthe passage of several ships, then explode underthe next one to pass over.

FLEET BALLISTICMISSILE SYSTEM

The fleet ballistic missile is a two-stageunderwater-to-surface inertiaily-guided ballisticmissile. It has undergone several evolutionarystages since 1960. The first unit, the POLARISA-I, has a range of 1200 nautical miles. The A-2model, first test-fired in 1961, reached a targetat 1500 NM. Next came the A-3 (2500 NM),first successfully fired by the USS ANDREWJACKSON (SSBN 619) in 1963. Currently thePOSEIDON (C-3) is being used in the FBM fleetin addition to the POLARIS A-3. The nextgeneration is the TRIDENT missile of which 24are carried on board the new TRIDENT classsu bum rine.

The first version is planned to have a rangeof 4000 NM. With such a range, the launchingsubmarine could hide in any ocean and send ainksile to any major city in the world.

2 6


ENGINE ROOM

MISSILECOMPARTMENT

MISSILECONTROLCENTERTUNNEL

-111

OFFICER& WARDROOMCPO QUARTERS

NAVIGATION CENTERCONTROL ROOMATTACK CENTER

CREW'S QUARTERS

OFFICERSQUARTERS TORPEDO ROOM

111111111 gra:-ligrinettrj3111 ,ft

RE ATORCOMPARTMENT

AUXILIARYMACH NERY

SPACE

GYRO ROOM

CREWS CREW'SWASHROOM QUARTERS

BATTERY

Figure 2-6.SSBN class submarine; interior arrangement.

The FBM (fig. 2-6) is designed to belaunched from a submarine cniising (orstationary) below the ocean's surface. The twopowerful solid-propellant rocket motors arecapable of lifting the warhead high above therange of any known antimissile missile, at aspeed exceeding ten times that of sound, and ofplacing it into a free fall trajectory which willcarry it to its target with deadly accuracy. Eachwarhead of the POLARIS or POSEIDON is acompact and powerful nuclear device. Theexplosive power in one shipload of sixteenmissiles exceeds the total amount of explosivepower expended by all of the participatingcountries in World War II, INCLUDING theatomic bombs dropped on Japan.

11

2 7

CREW'S MESS

71.1

After launch, ignition of the first stagerocket takes place shortly after the missilebreaks the surface of the sea (fig. 2-7). This isthe beginning of powered flight and the inertialguidance portion of the trajectory. The firststage propels the missile far into the atmosphere.The first stage then separates and the secondstage rocket motor continues to propel themissile to a point above the earth's atmosphere.When the missile has reached the proper velocityand -,oint on the trajectory, the reentry body.en. ites and the warhead follows a ballistictr. ,..ory to the target. MIRV warheads can be

,-ately targeted. The time of reentry body..,.ation determines the range which the

,vurrid will span. The range can ba


varied in this way from about 575 to about2500 nautical miles.

Since there are no external control surfaceson POLARIS or POSEIDON, changes in thetrajectory are accomplished by deflecting the jetstream from its motors. A pre-comput idealtrajectory is preset into the missile. The presetinformation takes into account the movementsof the target, of the launching point, and of themissile with respect to inertial space during thetime of flight. The warhead release velocitywhich the missile must attain along its trajectoryon the basis of a fixed time-of-flight is alsopreset. The launching submarine accuratelydetermines its launching position by use of aninertiai navigation system, and the position ofthe target on the earth surface is a known factor.While in the power stage of flight, the missilecontinuously measures its linear accelerations onthe basis of its inertial system and alters itstrajectory to offset the outside forces causingunwanted accelerations. When the missile is on aproper trajectory and a correct velocity has beenattained, the warheads are released and proceedtoward the target with no further correctionpossible.

POWEREDFLIGHT

( INERTIALGUIDANCE

ONLY )

TERMINATION

Each warhead dives on its target at a steepangle and at several times the speed of sound.The materials for the outer surface of thewarhead have been specially developed to resistthe high temperatures generated by friction withthe atmosphere at reentry speeds, and suitableinsulation is provided between the outer skinand the internal components to prevent damageto the warhead.

The SSBN provides a mobile launchingplatform which is extremely difficult to detect.It can remain submerged for very long periods oftime and cruise to almost any position withinthe oceans of the world. By use of its inertialnavigation system, it can provide the precise lirecontrol data required to place each warhead ontarget.

SUBROC MISSILE SYSTEM

S )(' is an underwater-to-air-to-unck:.watcv lissile designed to destroy enemysubmar. ;it long range. The missile consistsessentiall () a nuclear depth bomb and a rocketmotor joined together. The launching submarinecai-ries the equipment for detecting and trackingt he enemy submarine, the fire control

BALLISTIC FLIGHT

2ND STAGE IGNITION1ST STAGE SEPARATION

ST STAGE IGNITION

1

33.269Figure 2-7.POLAR I S trajectory (not to scale).

23

2 8


equipment for computing the target informationand providing the necessary pre-launch missileinformation, and the equipment for launchingthe missile. The missile is designed to belaunched (fig. 2-8) from a standard submarinetorpedo tube, using conventional ejectionmethods. Upon being launched, the rocketmotor is ignited at a safe distance from the firingship. The missile's flight through the air is

controlled by an inertial guidance system whichfunctions in accordance with the fire controlinfcrmation set-in prior to launch. In addition toproviding the propulsive force for the missile,the rocket motor furnishes power for controllingthe thrust vectoring mechanism, during theboost phase, and the thrust reversal necessary toaccomplish rocket motor separation At theproper point in its trajectory, the rocket motorseparates and the missile continues in a free-fallflight. At the time of separation, the control of

the missile is switched from the thrust vectoringmechanism to aerolins. During the ballisticportion of the flight, the aerofins control themissile in roll and azimuth. Pitch guidance isinitiated at or near the zenith of the trajectoryto direct the missile to the desired point ofimpact on the water surface. Guidance is

terminated at a predetermined height above thewater, and the last portion of its above-watertrajectory is free fall. At water impact, a timermechanism starts and causes the warhead todetonate at the proper time.

More detailed information on SUBROC,POSEIDON, and POLARIS can be found in theappropriate classified publications.

ANTISUBMARINE UNITS

The appearance of new equipment andweapons and the modification of their older

2 9Figrue 2-8,Artist's view o ic trajectory of SUBROC.

24

42.227

Chapter 2-HISTORY AND DEVELOPMENT OF ASW

counterparts have resulted in the demand formore modern versions of ASW units. These maybe brand new units or highly modified ships orsubmarines of our ASW forces. Some examplesof ASW units follow.

AIRCRAFT CARRIER (CV)

One of the missions of the (CV) is tosupport and operate aircraft for antisubmarinewarfare operations in addition to its normalmission as an actual carrier.

DESTROYER (DD)

All destroyer-type ships are named fordeceased members of the Navy, Marine Corps,and Coast Guard, and Secretaries of the Navy.Destroyers (fig. 2-9) are multipurpose shipsuseful in ahnost any kind of naval operation.They are fast ships with a variety' of armamentbut little or no armor. For portection, theydepend on their speed and mobility.

The principal function of destroyers is tooperate offensively and defensively againstsubmarines and surface ships, and to defendagainst air attack. They also provide gunfiresupport for amphibious assaults and performpatrol, search, and rescue missions.

Armament consists of 5-inch and 3-inchguns, and a variety of antisubmarine weapons,such as torpedoes and ASROC (antisubmarinerocket).

Displacement varies from about 3000 tonsto over 7000 tons. The newest type of destroyerin the fleet (fig. 2-10), the DD 963 (Spruance)class, has a displacement of approximately 780-tons, a length of 560 feet, and a beam of over 50feet. Armament consists of two5-inch/54-caliber guns, ASROC, torpedoes,surface-to-surface missiles, and two ASWhelicopters. This destroyer is driven by an all-gasturbine propulsion system and two controllablepitch propellers.

GUIDED-MISSILE DESTROYER (DDG)

The DDGs of the Charles F. Adams classhave a displacement of about 4500 tons. Theirarmament consists of two 5-inch/54-calibersingle-gun mounts (one fore and one aft) and atwin TARTAR missile launcher aft (some have asingle launcher aft). All have an ASROClauncher amidships (fig. 2-11). Several of thepostwar FORREST SHERMAN class (fig. 2-12)have been converted t^ DDGs by replacing thenumber 2 ,2,un mount with a TARTAR missilelauncher.

3 0

71.129Figure 2-9.USS WILLIAM M. WOOD (DD 715).

25

INTRODUCTION TO SONAR'FRIGATE (FF)

--7771-7 -413R

aI 74-t-

-"91

Figure 2-10.DD 963 (SPRUANCE) class.

Frigates (fig. 2-13) resemble destroyers inappearance; but they are slower, having only asingle propeller, and carry less armament. Themission of FFs is to screen support forces andconvoys and to operate offensively againstsubmarines. They also may be used for shorebombardment. Frigates, formerly destroyerescorts, have grown in size from about 1500

71.130

tons in World War H to over 4000 tons in theKNOX (FF 1052) class. Their armament variesfrom class to class; that of the KNOX consists ofa single 5-inch/54-caliber gun, ASROC, LAMPS,and antisubmarine torpedoes.

GUIDED-MISSILE FRIGATE (FFG)

Guided-missile frigates are basically the sameas frigates with the addition of single TARTARmissile launcher. (See fig. 2-14.)

33.272

Figure 2-11.ASROC launch from USS HENRY B. WILSON (DDG 7).

Chapter 2-- III sTo RY AND DEVI:L.0PM kW 01: A SW

Figure 2-12.FORREST SHERMAN class destroyer (DD).

--:" - - -

^ .-....

:17,

-%

7*" -,

,

Figure 2-13.USS ALYWIN (FF 1081) firing ASROC.

17

3 1

3.76

134.87-1081

iNTRODIA TION TO SONA R

Figure 2-14.USS RAMSEY FFG-2 (BROOKE class).

SI1

....!...,

--: --e,----s. IF-I .: 0,.. .. 7,. . , -,..

,,........,..., -... .. .!. .4,

..

N.,,.. -4 .

Figure 2-15A.USS GRIDLEY (CG 21),

3 .3

71.131

134.84

Chapter 2 HISTORY AND DEVE LOPM EN I' OF ASW

GUIDED-MISSILECRUISER (CG ) (CGN )

Guided-missile cruisers are al several classes,differing from each other mainly in type andplacement of their armament, although some aresmaller than others. The USS I3ELKNAP (CG26), for instance, displaces 6700 tons. She has atwin launcher forward that can fire bothTERRIER missiles and ASROC, a single5-inch/54-caliber gun aft, and two 3-inch gunsamidships. The USS LEAHY (CG 16) displaces5600 tons. has a twin TERRIER launcher foreand aft, four 3-inch guns, and an ASROClauncher amidships. The nuclear-powered USSBAINBRIDGE (CGN 25) is about 1000 tonsheavier than the BELKNAP, with essentially thesame armament. A guided-missile cruiser isshown in figure 2-15A. Figure 2-1513 shows the

;mull

-

444 .

newer nuclear-powered guided-missile cal iser,USS SOUTH CAROLINA (CGN 37). She has anoverall length of 596 feet. a beam of 61 feet,and a speed in excess of 30 knots. She isequipped with the most advanced sonar andantisubmarine weapons.

ANTISUBMARINE ARMAMENT

One factor is responsible for effectivecountermeasures against submarines: that is. thesound the submarine itself generates. As ASWprograms have been developed, a vast array ofacoustic weapons have been produced. Theseweapons operate by using sound detectingmethods and feature active sonar, passive sonarand a combination of both. Suchcountermeasures. of course, become less

-

14.

*"/

Figure 2-15B.Underway view of USS SOUTH CAROLINA (GN 37).

29

71.132


effective as submarines are designed to generateless noise.

ASROC

The ASROC, whose launcher is shown infigure 2-16, is a subsonic, shipboard-launched,solid-fuel, rocket-propelled antisubmarine

LEFT REAR

RIGHT FRONT

Figure 2-16.ASROC launcher.

ballistic projectile. The missile has twoconfigurationsone with a depth charge and onewith a torpedo.

The goal achieved by ASROC is thedestruction of submarines at long ranges. Thisobjective is achieved by delivery of a torpedo ornuclear depth charge through the air to a pointin the water from which it can either attackunder the most favorable circumstances or havethe submarine within its lethal radius (fig. 2-17).The payload is a part of an unguided missilewhich is propelled by a rocket motor andstabilized by an airframe throughout its poweredflight. Separation timers jettison the airframeand motor after a preset time. From separationto water entry, different methods ofstabilization are employed, depending on thepayload. The depth charge descent is stabilizedby a fin network during the entire drop. Thetorpedo also has such a network; but it employs,in addition, paLcnute staeilization. Besidesstabilizing the torpedo descent, the parachutealso decelerates it to a safe water entry velocityto avoid damaging the highly sensitive electroniccomponents.

Before the missile is launched, the submarineis located by sonar; and the range, bearing, andother pertinent data are transmitted to the firecontrol system. The fire control systemautomatically computes the anticipated targetposition, sets the rocket motor thnist cutoffvelocity and the time to airframe separationinto an ignition and separation assembly, locatedwithin the airframe, on the desired water entrypoint. In this way, the missile can be fired at willby simply closing the firing circuit.

TORPEDOES

There are four principal ways to launch atorpedo: by letting it swim out of the tube, byfiring it from a tube, by dropping it from a rack,or by propelling it part of the way to its targetas a rocket payload.

Aircraft drop torpedoes from launchingracks. Usually, an aircraft carries two torpedoes;

15.106 a helicopter can carry one or two torpedoes forASW work.

30

3 5


Figure 2-17.ASROC.

The Navy's older destroyers, as well asFRAM destroyers. DDGs, and CGs, carrytorpedoes in the 3-barrel Mk 32 launcher (fig.2-18).

Twin mounts can fire from either side. Theycan be trained through a wide arc so thattorpedoes may be fired through a wide range ofbearings. Compressed air expels the torpedoesfrom the tube with enough force to clear theship.

Mk 44 Torpedo

The Mk 44 torpedo (being phased out) is anelectrically controlled and electrically propelledantisubmarine weapon with an active acoustic

31

CCt... TRU,. <

15.114

JUNCTION BOX

1PAIN.NG RANDLE TRAINI%G GEAR( ARM ASsi:MBLY ) BREECH MECHANISM

Figure 2-18.Mk 32 torpedo tube.3.129


Figure 2-19.P-3 ORION, land-based long-range patrol craft.

homing system. The torpedo can be launchedfrom surface ships or aircraft and is one of thetorpedo payloads for ASROC.

The torpedo is designed to attack submergedsubmarines traveling at moderate speeds. Afterenabling, the torpedo searches for a target byactive acoustic means while maneuvering in adepth varying helical path. Echoes from thetarget cause the torpedo to steer toward thetarget until contact is made. If the torpedo losesthe target, it searches for a short time in thegeneral direction in which it is traveling and, ifunsuccessful in relocating the target, resumes ahelical search.

The acoustic homing system of the torpedoalso has a passive feature that allows the torpedoto respond to an acoustic noise source whosefrequr-Acy level is within the sensitivity range ofthe receiver. During the torpedo's normal searchpattern, passive homing on a target noise sourceaids in target acquisition, increasing the attackcapabilities of the weapon.

Mk 46 Torpedo

The Mk 46 torpedo is the successor to theMk 44. The principal difference between thetwo is the improved propulsive power of the Mk

134.95

46, which gives it gTeater speed, range, anddepth capabilities.

AIRCRAFT

The use of aircraft in conjunction with shipsand submarines adds greater capability andversatility to ASW. Areas of surveillance can beenlarged; ranges can be extended for detectionand attack; and diversified weapons can be used.Two types of aircraft are used in ASW: thehelicopter for close ranges and the fixed-wingaircraft for long ranges. The helicopter uses adippin sonar; that is, one that may be loweredfrom the aircraft for searching and retracted forflight. Both helicopters and fixed-wing aircraftuse magnetic anomaly detection (MAD)equipment whereby they detect the submarineby variations in the Earth's magnetic lines offorce.

Aircraft also use other devices for detectingthe presence of submarines. One of these devicesis thc sonobuoy, which is dropped into thewater by the aircraft and then monitored byradio. Sonobuoys arc described in chapter 6.

The aircraft also can be used as a tacticalvehicle to launch a weapon at the submarine.

323 7

Chapta 2IIISTORY AND DEVELOPMENT OF ASW

Figure 2-20.S-3A VIKING A/S search and attack aircraft.

ElleAttL

Figure 2-21.LAMPS helicopter (SH-2F).

33

71.133

71.134

INTRODUCTION "F0 SONAR

Among the weapons that can he launched froman aircraft are the homing torpedo and thenuclear depth charge.

PATROL PLANE

Patrol planes are land-based, long-range,mult ngine aircraft used for detecting,tracking, and attacking enemy shipping andsubmarines.

The P-3 ORION (fig. 2-19) is the Navy'sprincipal patrol plane. To carry out its primarymission of locating and attacking submarines, ithas a variety of sensors, including radar,sonobuoys, magnetic anomaly detector (MAI)),and electromagnetic intercept (ISM) equipment.ORION's armament includes torpedoes, rockets,depth bombs, air-to-surface missiles, andconventional bombs. It also can be used foraerial mining.

ANTISUBMARINE AIRCRAFT

Shipboard aircraft used for antisubmarine( A SW ) m issions are the S-3A VIKING

3 9

34

fixed-wing aircraft and the Sil-2E SEASPRITE,the Light Airborne Multi-Purpose System( LAMPS) helicopter. Both are integral parts ofASW search-attack units.

The S-3A VIKING (fig. 2-20) is a

carrier-based jet-powered A/S search atul attackaircraft Detection equipment includes radar,ESM receivers, sonobuoys, and MAD gear.0 rd na n cc. eq uipment includes torpedoes,rockets, and depth bombs.

The SI-I-2F (LAMPS) (fig. 2-21) helicoptersare found aboard a variety of ASW ships. Theyprovide the ship with an extended antishipmissile defense and ASW system. Detectionequipment includes active and passivesonobuoys, magnetic anomaly gear, and radar.Secondary functions include ali-weather searchand rescue, plane guard duties, gunfireobservation, personnel transfer, and verticalreplenishment. Weapons include torpedoes anddepth bombs.

CHAPTER 3

PHYSICS OF SOUND

Sonar is an electronic device that uses soundenergy to locate submerged objects such assubmari .es. Sonar equipment may be eitheractive or passive. Active sonar transmits soundenergy into the water and depends on thereturning echoes bouncing off the target toprovide bearing and range information. Passivesonar uses sounds originated by the target (suchas screw cavitation, machinery noises, etc.) todetermine bearing information. This chapterdeals with sound and its behavior in seawater.

Sound travels in the form of waves whichmay be classified as transverse or longitudinal. Atransverse wave is one in which the particles ofthe medium through which the wave is passingmove at right angles vertically to the wave'sdirection. In a longitudinal wave, the particlesmove back and forth along the wave's directionof travel, resulting in compression andrarefaction of the wave.

An example of a transverse wave is a waterwave. Throw a stone into a pool. A series ofcircular waves travels away from thedisturbance. In figure 3-1, such waves are

71.19

Figure 3-1.Elements of a wave.

35

diagramed as though seen in cross section.Observe that the waves are a succession of crestsand troughs. The wavelength (I cycle) is thedistance from the crest of one wave to the crestof the next wave. The amplitude of a transversewave is half the distance, measured verticallyfr:)m crest to trough, and serves to indicate theintensity of the wave motion.

Sound waves vary in length according totheir frequency. A sound having a longwavelength is heard at a low pitch; one with ashort wavelength is heard at a high pitch. Acomplete wavelength is called a cycle, and thenumber of cycles per second is the sound'sfrequency.

Frequencies are now measured in the Hertzsystem, 1 hertz (Hz) being equal to 1 cycle persecond. Frequencies of 1000 cps or more aremeasured in kilohertz (kHz). Normally, soundsbelow 20 Hz or above 15 kHz are beyond thehuman hearing range. Between these twofrequencies is the average human audible range.In short, sound is the physical cause of yoursensation of hearing; anything that you hear is asou nd .

REQUIREMENTS FOR SOUND

Before sound can be produced, three basicelements must be present. These elements are asource of sound, a medium to transmit thesound, and a detector to hear it. In the absenceof any one element, there can be no sound.

You may recall the experiment in which abell was placed inside a jar containing a vacuum.You could see the bell striking, but you couldhear nothing because there was no medium totransmit sound from the bell to you. What about


71.18Figure 3-2.The three elements of sound.

the third element, the detector? You may see asource (such as an explosion) apparentlyproducing a sound, and you know the medium(air) is present, but you are too far away to hearthe noise. So far as you are concerned, there wasno detector and, therefore, no sound. Forpurposes of this text, we must assume thatsound can exist only when an auditory vibrationis caused by a source, is transmitted through amedium, and is heard by a detector. Figure 3-2illustrates this assumption. The bell vibrates onbeing struck, thus acting as a sound source. Thevibrating bell moves the particles of airthemediumin contact with it. And the soundwaves travel to the ear, which acts as thedetector.

Source

Any object that moves rapidly to and fro, orvibrates, and thus disturbs the medium around itmay become a sound source. Bells, radioloudspeaker diaphragms, and stringedinstruments are familiar sound sources.

Medium

Sound waves are passed along by thematerial through which they travel. The densityof the medium determines the ease, distance,and speed of sound transmiion. The greater thedensity, the greater the speed of sound. Thespeed of sound through water is about fourtimes that through air and through steel it isabou:. 15 times greater than through air.

Detector

The detector acts as the receiver of thesound wave. Because it doesn't surround thesource of the sound wave, the detector absorbsonly part of the wave's energy and requires anamplifier to boost the signal's energy to permitreception of weak signals.

THE EAR AS A SOUND DETECTOR.Thelimits of human hearing are determined by twointeracting physical variables, frequency andintensity, and several other conditions that aredependent on the individual variables (includingage, state of health, attention, and priorexposure). The limits of hearing, however, arenormally between 20 Hz and 20 kHz for young,healthy persons, provided the upper and lowerfrequencies are sufficiently intense. For healthy,middle-aged persons, however, the upper limitmay lie between 12 and 16 kHz, thelow-frequency Lhreshold remaining about 20 Hz.For purposes of this text, sounds capable ofbeing heard are called sonics. Sounds below 20Hz are called subsonics, and those above 15 kHzare known as ultrasonics or supersonics. Theterm "ultrasonic" inerely refers to acousticphenomena above the level of human hearing. A15-kHz vibration might be "ultrasonic" for theaverage 60-year-old person.

Early active sonar equipments transmittedultrasonic sounds through the water. Along withother sounds, they received echoes of theseultrasonic sounds and converted them intoaudible ones. Modern active sonars transmitsounds within the audible range. Because thesetransmissions are very high tones, however, theequipment converts them into lower ones bettersuited for listening.

The human ear is a good sound detector. Itcan detect a wide range of frequencies but doesnot respond equally well to all of them. Figure3-3 illustrates the variation in the amount ofpower that is barely audible to the average ear atdifferent frequencies. It is evident from thischart that the ear is most sensitive to frequenciesin the range from about 1000 Hz to 2000 Hz.The average person finds an 800-Hz note arather pleasant one tu listen to for long periods

4 iof time. In underwater echo ranging equipment,

36

Chapter 3PHYSICS OF SOUND

RELATIVE POWER FOR AUDIBLE SOUNDS

AVERAGE

FREQUENCY

SENSITIVITY

OF HUMAN EAR

100 1000 10000FREQUENCY HERTZ

100,CCA.:

10,000

1000

00

10

71.46Figure 3-3.Frequency sensitivity of the human

ear.

the echo frequency commonly is converted toan 800-Hz note.

Never turn up the volume on sonarequipment so that echo sounds are louder thannecessary. One reason is that the ear is not asensitive detector of relative changes in soundintensity. An increase or decrease of aboutone-fourth of the total power must take placebefore the ear notices any difference.

An intensely loud sound slightly paralyzesthe ear, reducing its ability to hear low-intensitysounds that follow immediately. This effect issimilar to one you probably have experiencedwith light. If you look into a very strong light,your eyes are blinded momentarily.

The ear is a sensitive detector of change inpitch. An average person can tell when soundsdiffer a few hertz in pitch, even though theycannot detect the change in intensity. Thisfaculty is known as pitch discrimination. It is agreat help in selecting from a background ofreverberations a submarine echo of slightlydifferent pitch, that is, one with doppler.

Here's a summary of your ear'scharacteristics:

I. Your ear does not readily detect smallrelative changes in sound intensity. It is notsensitive to high and low audible frequencies.

2. Your ear is sensitive to the 800-Hz notefor which sonar equipment is designed. Your ear

IL

37

4 2

temporarily is paralyzed by very loud signals sothat you may not hear the weaker signals thatfollow.

3. Your ear has the property of pitchdiscrimination. This characteristic will aid you inselecting an echo from the background of noiseand reverberation.

Heavy gunfire may cause permanentdeafness or other injury to your ears. Use earprotectors or cotton when near gunfire, and takeevery possible precaution to protect yourhearing. As a Sonar Technician, you are essentialto the successful mission of your ship. Yourability to operate the sonar depends on theeffectiveness of your hearing.

SOUND WAVES

Sound waves are longitudiral or compressionwaves, set up by some vibrating object such as asonar transducer. In its forward movement, thevibrating transducer pushes the water particleslying against it, producing an area of highpressure, or compression.

On the backward movement of thetransducer, the water particles return to the areafrom which they were displaced duringcompression and travel beyond, producing anarea of low pressure, or a rarefaction. Thecompression moves outward by pushing thewater particles immediately in front of thecompressed particles. The rarefaction followstit: compression, transferring the pull producedby the backward movement to the particlesimmediately ahead. The next forward movementof the transducer produces another compressionand so on. In figure 3-4 the compressions arerepresented by dark rings. As the sound wavesspread out, their energy simultaneously spreadsthrough an increasingly large area. Thus thewave energy becomes weaker as distanceincreases.

Another way of representing the actions of asound wave is illustrated in figure 3-5.Compressions are shown as hills above thereference line, and rarefactions as valleys belowit. The wavelength is the distance from onepoint on a wave to the next point of similar


RAREFACTION

COMPRESSION IP

TRANSDUCER

WAVE LENGTH

4.221Figure 3-4,Longitudinal waves.

co m p r essi on. The change occurring incompression and rarefaction in the space of 1

wavelength is called a cycle.

Frequency

The frequency of a sound wave is thenumber of vibrations per second produced bythe sound source. A sonar transducer, forexample, may transmit on a frequency of 5 kHz,or 5000 vibrations per second. Mdtion isimparted to the sound wave by theback-and-forth movement of the particles of themedium, in effect passing the wave along,although the particles themselves have very littleactual movement. The wave, however, maytravel great distances at a high rate of speed.

38

Density

Perhaps you've heard people speak of aheavy fog as being "thick as pea soup." Thismurky condition would be a dense fog causedby the atmosphere being filled with smallparticles of water called vapor condensation. Afog-filled atmosphere is heavier (because of theweight of the water particles in it) than a clearatmosphere. The measure for this "thickness" ofa substance is called density, and is defined as"weight per unit volume." In the study ofgeneral physics, density of any substance is acomparison of its weight to the weight of anequal volume of pure water. Because of the saltcontent (salinity) of seawater, it has a densitygreater than that of freshwater.

Density is also an indication of the soundtransmission characteristics of a substance, ormedium. When a sound wave passes through amedium, it is transmitted from particle toparticle. If the particles are loosely packed (asthey are in freshwater as compared withseawater), they have a greater distance to moveto transmit the sound energy. During themovement, time is consumed, and the overallresult is a slower speed of sound in a less densemedium.

Density and elasticity are the basic factorsthat determine sound velocity. The formula fordetermining velocity is:

C

where C equals velocity, E equals the medium'selasticity, and p equals the medium's density.Variations in the basic velocity of sound in thesea are caused by changes in water temperature,pressure, and density, as will be seen in thesection on sound propagation. In freshwater of65° F. sound velocity is approximately 4790feet per second (fps). In seawater, velocitydepends on pressure and temperature in additionto salinity. For all practical purposes, you canassume that sound travels at a speed of 4800 fpsin seawater of 39° F.

4 3


-a-WAVELENGTH

&AMPLITUDE

COMPRESSION RAREFACTION

Figure 3-5.The sound wave.

Wavelength

the tone of a sound. With the propercombination of characteristics, the tone ispleasant. With the wrong combination, thesound quality degenerates into noise.

Pitch

An object that vibrates many times persecond produces a sound with a high pitch, as inthe instance of a whistle. The slower vibrationsof the heavier wires within a piano cause alow-pitched sound. Thus, the frequency of

71.21 vibration determines pitch. When the frequencyis low, sound waves are long: when it is high, thewaves are short.

If a sonar transducer vibrates at the rate of25,000 vibrations per second and if thetemperature is 39°F, the first wave will be 4800feet away at the end of the first second.Between the transducer and the front of thiswave there will be 25,000 compressions. Thus,the wavelength (that is, the distance betweenpoints of similar compression) must be 480025,000, or 0.192 foot, because there are 25,000compressions extending through a distance of4800 feet. The wavelength always can be foundif the frequency and the velocity are known.Formula:

Velocity.Wavelength Frequency

Suppose the wavelength is 0.4 foot and thefrequency is 12 kHz. What is the velocity?

Velocity.0.4 12,000

Expressed another way, velocity = 0.4 x 12,000= 4800 fps. If the wavelength and velocity areknown, the frequency can be found in a similarmanner.

0.4 = 4800.Frequency

Or, frequency = 4800 0.4 = 12 kHz.

CHARACTERISTICS OF SOUND

Sound has three basic characteristics: pitch,intensity, and quality. Together they make up

4 4 39

Intensity

Intensity and loudness often are mistakenlyinterpreted as having the same meaningAlthough they are related, they are not thesame. Intensity is a measure of a sound's energy.Loudness is the effect of intensity on anindividual in the same manner that pitch is theeffect of frequency. Increasing the intensitycauses an increase in loudness but not in a directproportion. To double the loudness of a soundrequires about a tenfold increase in the sound'sintensity.

Quality

The quality of a sound depends on thecomplexity of its sound waves. Most soundsconsist of a fundamental frequency (called thefirst harmonic) plus several other frequenciesthat are exact multiples of the fundamental. Thefundamental is the lowest frequency componentof the sound wave. By combining differentfundamentals in suitable proportions, a tone canbe built up to a desired quality. Musical tonesare produced by regular vibrations of the source;when the source vibrates irregularly, the sound iscalled noise. By sounding together the properorgan pipes, the tone of any vowel sound can beimitated. On the other hand, drawing afingernail across a blackboard only creates anoise.


MEASUREMENT OF SOUND

Throughout your Navy career as a SonarTechnician, you will be using decibels as anindicator of equipment performance. Poweroutput and reception sensitivity of a sonarequipment are measured in decibels, which areused to express large power ratios.

In the decibel system, the reference level iszero decibel (0-db), which is the threshold ofhearing. The pressure level, or signal strength, ofunderwater sounds is compared to the 0-db leveland is given either a positive or a negative value.Sonar receivers are capable of detecting soundshaving a signal strength below the 0-db level. Insuch instances, the signal is given a minus dbvalue.

The reason for using the decibel systemwhen expressing signal strength may be seen intable 3-1. It is much easier to say that a sourcelevel has increased 50 db, for example, than it isto say the power output has increased 100,000times. The amount of power increase or decreasefrom a reference level is the determiningfactornot the reference level itself. Whetherpower output is increased from I watt to 100

Table 3-1.Decibel Power Ratio Equivalents

Source Level (db) Power Ratio

1 . 1.33 = 2.05 = 3.26 . 4.07 . 5.010 . 1020 = 10030 = 100040 = 10,00050 = 100,00060 = 1,000,000=10'70 = 10,000,000=107100 = 101D110 = 10"140 = 10"

40

watts, or from 1000 watts to 100,000 watts, itstill is a 20-db increase.

Examine table 3-1 again, and take particularnote of the power ratios for source levels of 3 dband 6 db (also 7 and 10 db). It can be seen thatto increase a sonar's source level by 3 db, it isnecessary to double the output power. As atypical example, if the sonar source level dropsfrom 140 db to 137 db, the sonar has lost halfits power. Any 3-db loss, no matter what thesource level, means loss of half the formerpower.

Now let's see what is required to increase asonar's range. To double the range of a sonarrequires a source level increase of approximately27 db. This power increase is equivalent toabout 500 times, which obviously is impractical.By another method, such as increasing receiversensitivity, the rani4e can be increased fairlyeasily, although it may not be doubled.

So far we have discussed the decibel mainlyin relation to power output, but the decibel alsois used to determine receiver sensitivity.Receiver sensitivity is measured in minusnumbers, which represent the number ofdecibels below a reference level that signal canbe detected by the receiver. The larger thenegative number, the better the sensitivity.Although the range would not be doubled, it ismore practical, for instance, to increase areceiver's sensitivity from 112 db to 115 db thanit is to double the output power of the sonartransmitter. Also, it is not always necessary toincrease the sensitivity of the receiver itself. Aneffective increase of several decibels may beachieved if local noise levels can be reduced insuch sources as machinery, flow noise, crewnoise, etc.

NOISE

The most complex sound wave is one inwhich the sound consists of numerousfrequencies across a wide band. Such a form ofsound is called noise because it has no tonalquality. The source of several types of noisesmay be identified easily, however, because ofthe standard sound patterns of the noises. Shipnoise, for instance, consists of many different


ISELF

BACKGROUNDNOISE

AMBIENT

EQUIPMENT I 1 BIOLOGICAL

CREW

FLOW

MACHINERY

ISEA

1 MISCELL A NEOUS-H

1 UNIDENTIFIED

PROPULSION

AUXILIARY

Figure 3-6.Noise sources.71.116

sounds mixed together. You may be unable todistinguish a particular sound but, on the whole,you can recognize the sound source as a ship.Some noise sources are shown in figure 3-6. Thesources of many noises detected by sonar havenot yet been identified. Explanations of soniekinds of noises that have an adverse effect on asonar operator follow.

AMBIENT NOISE

Ambient noise is background noise in the seathat is due to natural causes. Differentphenomena contribute to the ambientbackground noise. Many of the sources areknown and their effects are predictable, butmany are still unknown. From this unwantedbackground noise, the sonar operator must beable to separate weak or intermittent targetnoises. In general, the average operator requiresa target signal strength of 4 db abovebackground noise.

THERMAL NOISE.The absolute minimumnoise in the ocean is called thermal noise. As the

41

4 6

name implies, it is a function of temperature.This noise is created by the motion of themolecules of the liquid itself and is difficult tomeasure.

SURFACE AGITATION.For a sizableregion above the residual minimum noise, theambient noise levels appear to be related to thesurface agitation. Usually, agitation of thesurface of the sea is measured as sea state.Surface windspeed, however, ordinarily is amore reliable measure of expected ambient noisethan sea state. As the wind rises, the surfacebecomes more and more agitated, causing theambient noise level to rise. Normally noise levelsin this region are associated with what is calledsea noise to distinguish them from other noiseswhich really arc not caused by the sea itseP. Aheavy rain, for instance, will add greatly to theambient noise.

Flow Noise

As an object moves through water, there is arelative flow between the object and themedium. This flow is easiest to understand byassuming that the object is stationary and thatthe water is moving past the object. If the objectis reasonably streamlined, its surface is smooth,and if it is moving very slowly, a flow patternknown as laminar flow is set up. Such a patternis shown in view A in figure 3-7, where the lines

71.22Figure 3-7.Patterns of flow noise: Alaminar

flow; Bturbulent flow.


represent the paths followed by the water as itflows around the object. If the flow is laminar,all lines are smooth. Although laminar flowproduces little, if any, noise, it occurs only atvery low speedsperhaps less than I or 2 knots.

If the speed of the water is increased, whorlsand eddies begin to appear in the flow pattern,as seen in part B in figure 3-7, and thephenomenon is called turbulent flow. Withinthese eddies occur points where the pressure iswidely different from the static pressure in themedium. Thus we have, in effect, a noise field. Ifa hydrophone is placed in such a region, violentfluctuations of pressure will occur on its face,and flow noise will be observed in the system.

As pressures fluctuate violently at any onepoint within the eddy, they also fluctuateviolently from point to point inside the eddy.Moreover, at any given instant, the averagepressure of the eddy as a whole differs butslightly from the static pressure. Thus, very littlenoise is radiated outside the area of turbulence.Hence, although a ship-mounted hydrophonemay be in an intense flow noise field, anotherhydrophone at some distance from the ship maybe unable to detect the noise at all. Flow noise,then, is almost exclusively a self-noise problem.

Actually, not much information is knownabout flow noise, but general statements may bemade about its effect on a shipbornehydrophone: (1) It is a function of speed with asharp threshold. At very low speeds there is noobservable flow noise. A slight increase in speedchanges the flow pattern from laminar toturbulent, and strong flow noise is observedimmediately. Further increases in speed step upthe intensity of the noise. (2) It is essentially alow-frequency noise. (3) It has very high levelswithin the area of turbulence but low levels inthe radiated field. In general, the noise field isstrongest at the surface of the moving body,decreasing rapidly as you move away from thesurface.

As the speed of the ship or object isincreased still further, the local pressure dropslow enough at some points to allow theformation of gas bubbles. This decrease inpressure represents the onset of cavitation. Thenoise associated with this phenomenon differsfrom flow noise.

4 742

WATER FLOW

Figure 3-8.Blade tip cavitation.

Cavitation

71.23

Cavitation is produced whenever a solidobject moves through the water at a speed greatenough to create air bubbles. After a short life,most of the bubbles collapse. The suddencollapse of the bubbles causes the acoustic signalknown as cavitation noise. Each bubble, as itcollapses, produces a sharp noise signal.

Because the onset of cavitation is related tothe speed of the object, it is logical thatcavitation first appears at the tips of thepropeller blades, inasmuch as the speed of theblade tips is considerably greater than _ _ speedof the propeller hub. This phenomenon knownas blade tip cavitation is illustrated in figure 3-8.

As the propeller speed increases, a greaterportion of the propeller's surface is moving fastenough to cause cavitation, and the cavitatingarea begins to move down the trailing edge ofthe blade. As the speed increases further, theentire back face of the blade commencescavitating, producing what is known as sheetcavitation. This form of cavitation is shown infigure 3-9. Cavitation noise is referred to ashydrophone effects. The amplitude andfrequency of cavitation noise are affectedconsiderably by changing speeds. Cavitationnoise versus speed at a constant depth isdiagramed in figure 3-10. The curves shown areidealized; they do not represent any particular


submarine. Note the great difference in noiselevel caused by the addition of only 20 turns,from 90 rpm to 110 rpm. At 90 rpm there is nocavitation; the noise level is due to flow noiseand background noise. At 110 rpm cavitationhas started, and the noise level has gone upmany decibels, with a peak amplitude at about400 Hz. As speed is increased further, theamplitude peak tends to move toward the lowerfrequencies. The amplitude increases at a lesserrate, but covers a broader frequency band. Thecurves are also characteristic of a submarine onthe surface and of surface warships although theamplitude levels may be different.

Cavitation noise versus depth at a constantspeed (170 rpm) is shown in figure 3-11. Theupper curve is the same as the upper curve infigure 3-10. As the submarine goes deeper, thecavitation noise decreases and moves to thehigher frequency end of the spectrum in muchthe same manner as though speed had beendecreased. This decrease in noise is caused bythe increased pressure with depth, which tendsto compress cavitation noise. The curves are notexactly the same as those shown in figure 3-10,but the similarity is readily apparent.

Machinery Noises

Machinery noise is produced aboard ship bythe main propulsion machinery and by any or allof a large number of auxiliary machines thatmay or may not be connected with the mainpropulsion system. Machinery noise usually isproduced by rotating or reciprocating machines.Most noise of this type is generated by dynamicimbalance of the rotating portion of themachinery that causes a vibration within themachine. Such a vibration may then betransmitted through the machine mounts to thehull from where it is radiated into the water asacoustic energy.

Shipboard Noise

In addition to the machinery discussed so far,there are many other shipboard noise sourcesover which you probably will not have anycontrol. Some of the noise sources are fire andflushing pumps, air compressors, refrigeration

43

60

WATE R FLOW 3,

Figure 3-9.Sheet cavitation.

1,EQUENCY (HERT Z1

500 )000 5000 10 COO

OEPTR.55FT

Figure 3-10.Speed effect on cavitation noise.

FREQUENCY (HERTZ)

100 500 1000 5000 10,00060

'53 90

0M-1

04 20

4

35.50

Rill :170 RPM

,

10424.

,

NIMItiminft/IIN/agnraja

gigure3-11.Depth effect on cavitation noise.

170 RPM150 RPM.30 RPM11ORPM

90 RPM

71.24

55 FT,100 FT200 FT

300 FT.

35.51


machinery, air conditioning systems. dieselgenerators, gasoline pumps, blower motors, andportable power tools. Any (or all) of theaforementioned equipment may be operating atany one time, adding greatly to the noiseradiated by the ship and therefore entering thesonar receiver. If the combination of thesenoises becomes too great for effective sonarsearch. ask your watch supervisor to request theOOD to secure all nonessential equipment.Another noise source is circuit noise, generatedwithin the sonar equipment itself, This noisemay be in the form of' a 60-hertz hum, staticlikenoises from electric cables due to improper cableshielding, or leakage currents from other sourcesentering the receiver stages. Unlike ambientnoise, however, this type of' generated noise maybe controlled.

Marine Life

A sonar operator may hear many strangesounds during his time on watch. He may haveto listen to (and try to identify) the source ofw h is tles, shrieks, buzzes, pings, knocks.cracklings, and other strange noises notordinarily associated with the sea. Most of thesenoises probably come from different species offish, but only a few have been identifiedpositively. Following are descriptions of a fewmarine life noises.

Porpoises give out a whistling sound andsometimes a sound like a chuckle. Thesemammals are found in all ocean areas of theworld. (Submarine hydroplanes and rudderssometimes also give off a whistling sound.)

Snapping shrimp are common around theworld between latitudes 45°N and 45°S, usuallyin waters less than 30 fathoms deep. As youapproach a bed of snapping shrimp, you hear abuzzing sound. As you go closer, the soundresembles fat sizzling on a fire, then becomessimilar to that given off by burning brush.

Whales, which are found in all oceans, giveoff a variety of sounds. including knocks.groans, pings. and one resembling a swingingrusty gate. The knocking sound of the spermwhale resembles the noise of hammering. Spermwhales and other large species seldom are heardin waters shallower than 1 00 fathoms. Blackfish.

44

which are similar to whales, emit a whistlingsound like a porpoise but cIearer in tone.

The preceding examples of marine life noisesare just a few that you will encounter. Do notlet the strange sounds mislead or distract you. Avalid target may be just beyond the whale youare listening to. Available tapes and filmsdescribe many biologic noises. AB SonarTechnicians should review these tapes and filmsperiodically to maintain proficiency in theirrecognition of sounds.

Torpedo Noise

Torpedo noise is distinct from all others.When a torpedo is fired from a submarine, thefirst indication might be the sound of escapingair, quickly followed by a propellerlike noise.The rhythm is too rapid for the beats to becounted (as you can count those of a ship'spropeller), and it increases swiftly in intensity asit approaches, resembling the whine of a jetengine, but not as high pitched.

UNDERWATER SOUND PULSE

Now that you know something of the theoryof sound, you are ready to take a closer look atwhat happens to an underwater sound pulse.

To gain the full benefit of echo rangingsonar equipment, you must be able to transmitan underwater sound pulse and recognize thereturning echo from a target. Detection of theecho depends on its quality and relativestrength. compared with the strength andcharacter of other sounds that tend to mask it.

Sonar Technicians must know (I) what canweaken sound as it travels through water, (2)what conditions in the sea determine the pathand speed of sound. and (3) what objects affectthe strength and character of the echo.

TRANSMISSION LOSSES

As a sound pulse travels outward from itssource, it becomes weaker and weaker. Much ofits energy is lost because of sea conditions anddistance. Three factors directly related to soundtransmission losses aye divergence, absorption,and scattering. The latter two are referred to as

Chapter 3PHYSCIS OF SOUND

atten uation loss and are dependent ontransmission frequency. Divergence loss isindependent of frequency.

Divergence

When a sound wave is projected from a pointsource, it assumes a spherical shape, spreadingequally in all directions. This spreading is calleddivergence; and the further the wave travels, themore energy it loses. The energy lost by a soundwave due to spherical divergence is inverselyproportional to the square of the distance fromits source, or 6 db each time it doubles.

In shallow water areas, the surface andbottom are boundaries that limit the verticaldivergence of the sound wave. Consequently, theexpanding wavefront is cylindrical, rather thanspherical, in shape. Cylindrical spreading loss isonly half that of a sphere, or 3 db each time thedistance is doubled. Spreading loss at close rangeis very high, but beyond about 2000 yardsthe loss becomes less significant.

Absorption

In the topic on sound waves, you learnedhow a sound pulse moves through water. Therepeated compressions and rarefactions of thesound wave causes the water molecules to moveback and forth, thus passing the sound wavealong. An old saying goes: "You can't getsomething for nothing." In our illustrative case.energy is lost (in the form of heat) by the soundpulse in its efforts to compress the water.Energy lost to the medium in this manner iscalled absorption loss.

Scattering

Besides losses caused by divergence andabsorption, a sound wave loses energy due to thecomposition of the medium through which itpasses. Composition of the sea naturally variesfrom ,place to place and from time to time. Ingeneral, however, seawater contains largeamounts of minute particles of foreign matterand many kinds of marine life of all shapes andsizes. Each time the sound wave meets one ofthese particles, a small amount of the sound is

45

So

reflected away from its direction of movementand is lost. The reflection losses to the water areknown as scattering losses. Some of thescattered energy is reflected back to the sonarreceiver and is then called volume reverberation(discussed later in this section).

REFLECTIONS

When a sound wave strikes the boundarybetween two mediums of different densities, thewave will be reflected, just as light is reflectedby a mirror. Some of the energy will be lost, butmost of it will be reflected at an angle equal tothe angle of incidence. The angle of incidence isthe angle, with respect to the perpendicular, atwhich the wave strikes the boundary. Accordingto the physics law of regular reflection(reflection from a smooth surface), the angle ofreflection equals the angle of incidence.

Reflection takes place whenever the soundhits the boundary between sea and air (seasurface) and between sea and bottom, and whenit hits a solid object, such as a submarine. Theamount of energy reflected depends on theobject's density, size, shape, and aspect. Moreenergy is reflected by a submarine broadside tothe sound beam than by one that is bow on.

Surface Effect

Because the density of water is severalhundred times that of air, practically all of asound wave is reflected downward when itstrikes the surface boundary. This effect is trueonly when the surface is quite smooth, however.When the surface is roug.h, scattering takes place.

Bottom Effect

The bottom of the sea reflects sound waves,too. In deep water, this aspect need not beconsidered; but, in waters of less than 100fathoms, the sound may be unwantedlyreflected from the bottom. Other considerationsbeing equal, transmission loss is least over softmud. Over rough and rock,' bottoms. the soundis scattered, resulting in strong bottomreverberations.


REVERBERATIONS

You probably are acquainted with the effectin an empty room where your voice seems toecho all around you as you talk. After you stoptalking, the sound continues to bounce aroundthe room from wall to wall until it finally isabsorbed by the walls and the air. The soundlevel in the room while you are talking is higherthan normal because of the reverberationeffects. The same effects can also be observed inthe ocean. Reverberation in the ocean usually isdivided into three categories. They arereverberations from the mass of water, from thesurface, and from the bottom.

The following discussion on reverberationsmay seem like a repetition of the topic onreflections, but the two phenomena are not thesame. Although reverberations are reflections, allreflections do not become reverberations. Allthe processes contributing to reverberation arerandom in nature, with the result thatreverberation amplitudes vary over wide limits.Moreover, reverberation level is proportional tosource level and to pulse length. Another pointto remember is that, when you are in companywith another ship, you may hear reverberationeffects from her sonar in addition to your own.

Volume Reverberation

Reverberation from the mass of water iscalled volume reverberation, which wasmentioned in the discussion on scattering.Suppose a short pulse of sound is sent out froma stationary underwater source, which isimmediately replaced by a listening hydrophone.As the pulse of sound travels through the water,it encounters various particles that reflect andscatter the sound. Because almost all of theseparticles are much smaller than a wavelength ofthe sound, they do not reflect the sound as a flatmirror reflects light. Instead, they absorb energyfrom the sound wave and reradiate this enerey inall directions. Some reradiated energy from eachparticle returns to the hydrophone at the sourcelocation and is heard as a gradually fadine toneat the same frequency as the source.

Surface Reverberation

Some of the sound energy from the sourcestrikes the surface, the point of impineement

moving farther and farther from the source asthe sound travels. If the surface were perfectlyflat, this sound energy would be reflected asthough from a mirror, and would bounce awayfrom the source in accordance with the laws ofreflection. But the surface is not perfectlysmooth, and each wavelet tends to reflect thesound in all directions. Some reflected soundreturns to the hydrophone, adding to thereverberation.

Bottom Reverberation

In general, reverberation effects from boththe mass of water and the surface are smallcompared to bottom reverberation. The bottomis usually much rougher than the surface. Thus,more of the sound is reflected in otherdirections than those expected of a reflectingmirror. If the water is fairly deep, no bottomreverberation occurs for quite some time afterthe pulse, because the sound must be given timeto reach the bottom and be reflected. Normally,a sharp rise eventually occurs in thereverberation level after the sourc s ic -it off,

REFRACTION

If there were no temperature differences inthe sea, a sound wave would travelapproximately in a straight line because thespeed of sound would be roughly the same at alldepths. As indicated in figure 3-12, the soundwould spread and become weakened byattenuation at a relatively constant rate.

Unfortunately, however, the speed of soundis not the same at all depths. The velocity ofsound in seawater increases from 4700 feet persecond to 5300 feet per second as thetemperature increases from 30° to 85° F. As willbe seen later in the chapter, salinity and pressurealso affect sound speed, but their effects usuallyare small in relation to the large effectscommonly produced by temperature changes.Because of the varyine temperature differencesin the sea, the sound does not travel in a straightline. Instead, it follows curved paths, resulting inbending, splitting, and distortion of the soundbeam.

46 5 1


MAXIMUM ECHO RANGE

71.26Figure 3-12.- Sound travel in water of constant

temperature.

When a beam of sound passes from onemedium in which its speed is high (such as warmwater) into one in which its speed is low (such ascool water), the beam is refracted (bent). Asound beam bends away from levels of hightemperatures and hid sound velocity, and bendstoward levels of low temperature and low soundvelocity. Figure 3-13 illustrates the refraction ofa sound beam. As a result of refraction, therange at which a submarine can be detected bysound may be reduced to less than 1000 yards.This range may change sharply with changingsubmarine depth.

QUENCHING

In strong winds and heavy seas, the roll andpitch of the echo ranging ship make it difficultto keep the sound directed on the target.Additionally, the turbulence produces airbubbles in the water, weakening the soundwaves. Occasionally this envelope of air bubblesblankets the sound emitted by the transducer.Sonar operators can tell, by a dull thuddingsound, when the sound beam is being sent outinto air. This action is known as quenching,

PROPAGATION OF SOUND IN THE SEA

We have discussed the various basicphenomena that cause power loss in transmitting

47

or 2

HIGH TEMPERATURE

71.27Figure 3-13.A refracted sound beam.

sound: divergence, attenuation (absorption, andscattering). reflections, reverberations,refraction, and quenching. Now, we mustconsider the structure of the sea as an acousticmedium and learn the effects of this structureon the transmission of sound.

STRUCTURAL CONDITIONS

The speed of sound wave travel through thewater is controlled by three conditions of thesea: ( I ) temperature, which takes the form ofslopes and gradients; (2) pressure, caused byincreased depth; and (3) salinity, or the saltcontent of the water.

Temperature

With presently operational sonars,temperature is by far the most important of thefactors affecting the speed of sound in water.Depending on the temperature, the speed ofsound increases with increasing temperature atthe rate of 4 to 8 feet per second per degree ofchange. Inasmuch as the temperature of the seavaries from freezing in the polar seas to morethan 85°F in the tropics, and may decrease bymore than 30°F from the surface to depth of450 feet, it is clear that temperature has a greateffect on the speed of sound. Remember: Thespeed of sound increases when the temperatureof water increases.


PRESSURE SAL1NiTY(PSI) (0 00)

0 2500 5000 33 34 35

2000

) 4000u_la 6000LU0

8000

10,000

TEMPERATURE( F)

30 45 60

0 90 180 42 146 150 297 404.5VELOCITY CHANGE

(FT SEC)

COmPOSITE

512 4800 4900 5000vELOCITY(FT SEC)

35.5Figure 3-14.Nomal curves for pressure, salinity, and temperature.

Pressure

Sound travels faster in water under pressure.Pressure increases as depth increases, so thedeeper a sound wave travels, the faster it travels.Pressure effect on transmitted sound, althoughrather small in comparison to temperatureeffects, cannot be neglected. The speed of soundincreases about 2 feet per second each 100 feetof depth.

Salinity

Seawater has a high mineral content. Saltcontent is spoken of as the salinity of the water.The weight of the higher density seawater isabout 64 pounds per cubic foot: that offreshwater is about 62.4 pounds per cubic foot.This variation is the result of the salt content inthe seawater.

The overall effect of increasing the salinityof water is to increase the speed of the sound,which means that, when sound passes throughwater that varies in salinity, it travels faster inthe saltier water. In the open ocean, the valuesof salinity normally lie between 30 and 35 partsper thousand. In the region of rivers and otherfreshwater sources, the salinity values may fallto levels approaching zero. The speed of soundincreases about 4 feet per second for each partper thousand increase in salinity. Salinity has alesser effect on the speed of sound than doestemperature, but its effect is greater than that ofpressure. 5 3

48

Composite

Figure 3-14 shows reasonably normal curvesfor temperature, salinity, and pressure as afunction of depth in the Pacific Ocean and alsothe resulting velocity structure. It should benoted that the salinity variation plays a minorpart in the form of the depth velocity curve.This effect is almost entirely evident in the first500 feet below the surface. The temperaturecurve also shows wide variations in the top 500feet. From 2000 feet, downward, thetemperature is nearly uniform as the waterapproaches the maximum density point at about40°F. The pressure effect is represented by astraight line as thevelocity increases linearlywith depth.

On the composite curve, it easily can be seenthat the velocity in the top 2000 feet is asomewhat skewed replica of the temperaturecurve. Below 2000 feet it follows closely thestraight line gradient of the pressure curve.

Depth/Temperature Effect

Except at the mouths of great rivers, wheresalinity may be a determinant, the path followedby sound is governed by the water temperatureand the pressure effect of depth.

The pressure effect is always present andalways acts in the same manner, tending to bendthe sound upward. Figure 3 15 illustrates thesituation when the temperature does not change

Chapter 3PHYS1CS OF SOUND

LOW PRESSURE

71.29Figure 3-15.Pressure tends to bend the sound

beam upward.

with depth. Even though the temperature doesnot change, the speed of sound increases withdepth, due entirely to the effect of pressure, andthe sound bends upward.

Figure 3-16 shows what happens whentemperature increases steadily with depth. Whenthe surface of the sea is cooler than layers

71.30Figure 3-16.Positive thermal gradient tends to

bend the sound wave upward.5 449

beneath it, the water has a positive thermalgradient. Although this condition is unusual, itdoes happen and causes the sound to berefracted sharply upward. In certain areas of theRed Sea, bet ween Africa and Arabia,temperatures of well over 100°F have beenrecorded in depths exceeding 1 mile. Moreover,the salinity of the water in those areasapproaches 30%, compared to between 3% and4% in most ocean areas.

When the sea grows cooler as the depthincreases, the water is said to have a negativethermal gradient. Here the effect of temperaturegreatly outweighs the effect of depth, and thesound is refracted downward. This commoncondition is illustrated in figure 3-17.

If the temperature is the same throughoutthe water, the temperature gradient is isothermal(uniform temperature). In figure 3-18 the upperlayer of water is isothermal: beneath this layerthe temperature decreases with depth. Thistemperature change causes the transmittedsound to split and bend upward in theisothermal layer and downward below it.

Don't forget: When no temperaturedifference exists, the sound beam bends upward.When the temperature changes with depth, thesound beam bends away from the warmer water.

71.31Figure 3-17.Negative thermal gradient tends to

bend sound downward.


ISOTHERMAL

71.32Figure 3-18.Sound wave splits when temperature

is uniform at surface and cool at bottom.

Unde7 ordinary conditions the sea has atemperatrfe ;*.ructure similar to that in figure3-19. '11fis temperature structure consists ofthree rats: A surface layer of varying thickness.with uniform temperature (isothermal) or arelatively slight temperature gradient: thethermocline. a region of relatively rapid decreasein temperature: and the rest of the ocean, withslowly decreasing temperature down to thebottom. If this structure changes. the path of abeam of sound through thc water also changes.

LAYER DEPTH.Layer depth is the depthfrom the surface to the top of a sharp negativegradient. Under positive gradient conditions, thelayer depth is at the depth of maximumtemperature. Above layer depth. thetemperature may be uniform. If it is notuniform, a positive or weak negative gradientmay be present.

LAYER EFFECT.-- Layer effect is thepartial protection from echo ranging andlistening detection a submarine gains when itsubmerges below layer depth. Sometimes asubmarine, diving through a sharp thermoclinewhile taking evasive action, loses the screwnoises of the enemy ASW ship. Although usuallythe pinging can still be heard. it is as a low

50

intensity signal. On the ASW ship, ranges onsubmarines are reduced greatly when thesubmarine dives below a sharp thermocline.Often, the echoes received are weak and mushy.

SHALLOW WATER EFFECT.Echoranging is difficult in shallow water because thesound is reflected from the bottom. When theship is in shallow water and the ocean floor issmooth, the sound bends down from the surfaceto the bottom then back up to the surface, andagain down to the bottom. When thetransmitted sound acts in this manner, there arespaces empty of sonar coverage into which asubmarine can pass and be undetected. In figure3-20 you will notice how a sonar contact on asubmarine can be lost when the submarineenters the shaded area.

The shaded spaces in figure 3-20 are calledshadow zones. Contact is regained when thesubmarine enters the wave path again. As shownin the illustration. contact is made at long range(point A). is lost (point 13). and is regained atshort range (point C). Note however that,without the reflection, the maximum rangewould have been the short range at which thecontact was regained (point C).

The reason for the loss of contact at shortrange is shown at point D where the submarine

SEA SURFACE

TEMPERATURE UNIFORM ORCHANGING SLIGHTLY

WITH DEPTH

SURFACE LAYERISOTHERMAL OR"MIXED LAYER"

WHEN TEMPERATUREUNIFORM

TEMPERATUREDECREASINGRAPIDLY

THERMOCLINE

TEMPERATUREDECREASINGSLOWLY

REGION BELOW THETHERMOCLINE

r oFigure 3-19.Typical layers of the sea.

71.33


SURFA

BOTTOM

a

,-e,

A

1r, ,

\\

I

,...

'

71.28Figure 3-20.Shallow water effect on transmitted

sound.

passes beneath the sound. The distance at whichcontact is lost at short range depends on thedepth of the submarine. Here is a rule of thumbfor estimating a submarine's depth:

The range in yards at loss of contact isroughly equal to the depth of thesubmarine in feet. A contact lost at 300yards would thus be presumed to beabout 300 feet deep.

Once the behavior of sound in seawater isknown, it is possible to predict sound conditionsin the sea. From the temperature gradient of thewater, an experienced person can judge themaximum range to expect. A new SonarTechnician is not expected to know how topredict sound conditions, but he shouldunderstand why results are poor one day andgood another day. He should know what ismeant by shadow zones, and the reasons whysound does not travel in a straight line. He alsoshould be able to distinguish between pooreq uipmen t adjustment and poor soundconditions.

Following are some general conditions forhearing echoes.

I. Usually poor near coasts (50 miles) ascompared to sea conditions farther out.

51

Conditions for hearing are particularly poor atthe mouths of rivers.

2. Better in winter than in summer.3. Better at night than in the middle of the

day, especially in spring and summer.4. Better in morning than in the afternoon,

in spring and summer, but little change ifwhitecaps are present. In many localities,however, conditions are better in the afternoonthan in the morning because of the effect ofprevailing wii;(1s that freshen in the afternoon.

DEEP WATERSOUND Pz,DPAGATION

From the preceding discussions, it can beconcluded that the behavior of the sound waveis influenced considerably by the structure ofthe sea. Most of our discussion so far haspointed out the adverse effects on a sound beamin comparatively shallow watersay 100fathoms or less. Now, let's examine some of thephenomena that take place in very deep water.

Direct Path

Theoretically, if the sound waves were notaffected by velocity gradients, all the soundwaves would be straight lines and would travel ina direct path at whatever angle they left thesource. In actual practice, however, the soundbeam follows a path, or paths, as determined bythe sea condition at the time.

Sound Channel

Figure 3-21 illustrates a combination of twogadients of equal slope, one nega tive and one

VELOCITY 0-

}O-W

5 6

RANGE

71.34Figure 3-21.Strong negative and strong positive

gradients forming a sound channel.


positive. Their junction is a point of minimumvelocity. If a sound source transmits at thisdepth of minimum velocity, all of the sound --"---beams that start in an upward direction will bebent back down, and those that start downwardwill be bent back up. When such a conditionoccurs, we have a sound channel. The depth ofminimum velocity is the axis of the channel. Inthis symmetrical situation, a beam that startsout downward will rise as high above thechannel axis as it Ixent below it, and then will bebent downward again. Sound will remain in thechannel, as far as the channel exists, and willsuffer very little loss as it progresses through thechannel.

datiffike, _

Although sound channels are a rarity inshallow water (under 100 fathoms), they arealways present in the deep water areas of theworld. The depth of the axis of the channel isabout 350 fathoms in the central Pacific andsomewhat over 500 fathoms in the Atlantic. Inthe polar regions. where the surface water ismaterially colder, the axis of the channel liesnearer the surface.

Convergence Zone

Another effect that is closely related to thedeep sound channel is the convergence zoneeffect. The convergence zone effect, nowapplied to long-range active sonar, has long beenused by submarine sonar operators. If the soundsource iS placed near the surface instead of nearthe axis of the sound channel, the path followedby the sound beam looks somewhat like that infigure 3-11.

VEL0CITY-1 RANGE*-- 30 MILES

Figure 3-22.Convergence zone.51.8

525 7

51.7Figure 3-23.Bottom bounce effect.

Sound energy from a shallow source travelsdownward in deep water. At a depth of severalthousand feet, the signal is refracted, due topressure, and returns to the surface at a range ofabout 30 miles. The surface zone is from 3 to 5miles wide.

The sound that reaches the surface in thefirst convergence zone is reflected or refracted atthe surface and goes through the same patternagain. It produces a zone approximately 6 mileswide at 60 miles, and another 9 miles wide atabout 90 miles. Experienced Sonar Techniciansare familiar with this convergence zone effect.Often they have picked up strong noise signalsfrom targets that appear suddenly. show upstrongly for a few minutes, and then disappear.

A surface or near-surface contact detected inthe first convergence zone will have about thesame signal strength as a target detected at 3miles when no zone is present. Minimum depthrequired along the path of the sound 1,,.7m isabout 1000 fathoms. The usual requirc t is2000 fathoms for conducting convergence zonesearches. The minimum depth required is relatedto the surface velocity of the sound andincreases as the velocity increases.

Bottom Bounce

For long-range search in water depths over1000 fathoms, newer sonar equipment inayoperate in a bottom bounce mode. Thetransducer is tilted downward at an angle so thatthe sound beam strikes the bottom and isreflected back to the surface, as shown in figure3-23.


LOW

If( III 11((( ((« u«,,

HIGH

oil III 111 1111 1111 1111 III

Figure 3-24.Doppler effect.71.37

Because of the depression angle (150 to450 ). the sound beam is affected less by velocitychanges than are sound pulses transmitted in thenormal mode. At great depths (2500 fathomsand greater) however, the sound beam usuallywill be refracted before reaching the bottom,thus producing a convergence zone effect.

DOPPLER EFFECT

You probably are familiar with the changingpitch of a train whistle as the train passes nearyou at high speed. As the train approaches. thewhistle has a high frequency. As the train :Wesby. the frequency drops abruptly and becomes along, drawn-out sound. The apparent change infrequency of a signal resulting from relativemotion between the source and the receiver isknown as doppler effect. Figure 3-24 illustratesdoppler effect.

Each sound wave produced by the whistle isgiven an extra "push- by the motion of thetrain. As the train comes toward you, theresultant effect is an increase in pitch, caused bycompression of the waves. As the train movesaway from you, the sound waves are spreadfarther apart. resulting in lower pitch.

Although a stationary receiver was used forillustrative purposes, the same effects can beobserved if the receiver is moving toward astationary source.

Because doppler effect varies inversely withthe velocity of sound. the effect is much lessmarked in the sea than it is in the air. Dopplercan, however, be noted by the Sonar Technicianif he listens carefully.

DOPPLER ANDREVERBERATIONS

Earlier in this chapter you learned that, as asound pulse moves through the water, it losessonic of its energy to the water particles. Theparticles reradiate the energy in all directions.Part of the reradiated sound is returned to thesonar receiver, and the effect known asreverberation is heard. The water particlesbecome sound sources and, as your ship movesthrough the water. doppler effect is noticed. Thefollowing example should help clarify dopplereffect for you.

Your ship is underway at a speed of 15knots: sound velocity is 4800 feet per second:sound frequency is 14 kHz. The sonar is keyed,and I second later it is keyed again. During the1-second interval, the first pulse travels 4800feet. When the second pulse is transmitted, it isonly 4775 feet from the first one because theship has traveled 25 feet. Using the formulasgiven in onnection with wavelength, you caneasily determine that the apparent frequency ofthe reverberations from ahead of you isapproximately 14.1 Idly, whereas those frombehind your ship have a frequency of about 13.9kHz. Reverberations from the beam will havethe same frequency as the transmitted pulsebecause the ship is neither going toward theparticles nor away from them. The dopplereffect of reverberations is illustrated in figure3-25. To determine echo doppler. the SonarTechnician compares the tone of a target echoto the tone of the reverberations.

No Doppler

Consider the echo from a submarine that isneither going away from nor toward the soundbeam. It either is stopped or is crossing thesound beam at a right angle. If the submarine isin either of these situations, it reflects the samesound as the particles in the water, and its echohas exactly the same pitch as the reverberations,which means the submarine echo has nodoppler. Therefore, whenever the pitch of thesubmarine echo is the same as the pitch of thereverberations. you know that the submarine isstopped or that you are echoing off its beam.

53

0r 8


and you would report "No doppler." Figure3-26 illustrates a "No doppler" situation.

Doppler Up

Suppose the submarine is coming toward theecho ranging ship. In this situation, it is asthough the submarine were a train approaching acar at a crossing. The sound transmissionreflected from the approaching submarine isheard at a higher pitch than the reverberations.When the echo from the oncoming submarine ishigher than the reverberations, report "Dopplerup." When making this report, you are tellingthe conning officer that the submarine isheading toward your ship and making waythrough the water. This form of doppler isillustrated in figure 3-27. Notice in theillustration that the echo frequency of thesubmarine on the ship's starboard quarter is thesame as the ship's sonar frequency, yet it has updoppler. Remember, doppler is determined bycomparing the tone of the target echo and thetone of the reverberations.

Doppler Down

Just as the tone of a train's whistle decreasesin pitch as the train moves away from you, sodoes the doppler of a submarine moving awayfrom your ship. No matter where the submarineis located in relation to your ship, if he isheading aw,1! from you, the tone of hisreturning echo will be lower in pitch than thetone of the reverberations. Fimire 3-28illustrates two situations when you would report"Doppler down" to the conning officer.

DOPPLER REPORTS

To summarize what you have just learnedabout doppler: Doppler is the difference in pitchbetween the reverberations and the echo. Whenthe echo is higher than the reverberations, youwill sing out "Doppler up." If it's the same asthe reverberations, report "No doppler. If theecho is lower than the reverberations. s:."Doppler down."

----._

__.____---------- REVERBOATIONS THE SAME 14 0 kHzi -------cr--------,*\.,,N 's/ /----------1-1 \/ ----- --

.Z---_-_--.\

/ 7 ----=------.-REVERBERATIONS HIGH i4 1MHZ

I®

REVERBERTIONS,LOW 13 911Hz

"1)1...B111111111

HI) 1)11))11))ONE (((( (((( ((((

(1(? EMONE

PARTICLE +UNDERWAY PARTICLEOUTGOING PING 14 0 mHz

Figure 3-25.Illustration of doppler.

SUB ECHO - 14 1 MHZ

REVERBERATION- 14

71.39

SUB ECHO- IS 9*HzREVERBERATION-13 9 MHz

T-1G ;NO PE IR J4GA y

Figure 3-26.No doppler.

REvE 49E94 TJO% -14 -:ECB7 - 3K,

5 954

gi7,ERRELo....7ON.i3 9Sufi 0

Figure 3-27.Doppler up.

r 4 0 k

71.40

71,41


,...-, ...-

...

::.....-.........,......

/,'/' .........:-.......

/ .:-.................../ .......\:-.........:, N..

REVERBERATION- t4.1SUB ECHO- 14 OkHz "..."'-.'--------...,

EVERBERATioN-13.9,HzSUB ECHO -13 8 loit

DOPPLER DOWN DOPPLER DOWN

-4 UNDERWAYOUTGOING PING-

71.42Figure 3-28.Doppler down.

When you become a really skilled operator,you will be able to give the degree of doppler,that is, how high or low it is. For instance, asubmarine coming directly toward your ship at 6knots returns a higher echo than a submarine

2 KNOTSSLISHT UP

I4 KNOTSSLIGH1-4UP

16 KNOTSSLIGHT UP

KNOTS\ NO DOPPLER

NN\

\\\.4 KNOTS \HO DOPPLER\\

"'...N* 2 KNOTSNO DOPPLER

\ /..s\-

/\\\\ Ns, ''''13 KNOTS

m

'4'l 2 KNOTS0D RATE ,....\ SLIGHT UP

4sK*.N\j ,s'S DOWN' MODERATE DOWN ,...7, \ \ 71Ik N1,07D.;; T1/EHU/ P

2 KNOTS\ \ \ , \;\... -*Z."- .

/2,16.-; 6 KNOTS..00,. SLIGHT DOWN 7." "Nlk:. OR ABOVE\' MARKED UP

Figure 3-29.Dopp:er conditions.71.43

55

GO

coming directly toward the ship at 2 knots.Also, a submarine coming directly toward theship at 6 knots returns a higher echo than a6-knot submarine that is heading only slightlytoward the ship.

The importance of prompt and accuratereports cannot be overemphasized. Two detailscount: How much speed the submarine ismaking, pius how much it is heading t.oward oraway from the ship. The combination of thesetwo considerations is spoken of as thecomponent ot' the submarine's speed toward oraway from the ship. If the submarine's speedcomponent is more than 6 knots, report"Doppler marked, up (or down)." When it is 3to 6 knots, inclusive, report "Doppler moderate,up (or down)." If less than 3 knots. then call it"Doppler slight, up (or down)." (See figure3-29.)

You now realize how important it is to givean accurate report of doppler to the conningofficer. It tells whether the submarine is comingtoward or going away from your ship, and givesthe component of the submarine's motion.Remember that any contact that does havecb,ppler must be moving in the water: if it is nota surface ship, chances are that it is a submarineor a large ish. Figure 3-30 gives an idea of thevalue of' doppier.

INTERPRETING ECHOES

Sonar Technicians learn to recognize oneecho from another by listening to recordings ofreverberations and echoes and by practicing withthe sonar aboard ship. The following remarksmay be helpful: however, they cannot substitutefor actual practice.

DOPPLER/NO DOPPLER

As we said previously, an echo with doppleris probably a submarine or a large fish ormammal. A %vhale, for instance. may have echocharacteristics closely resembling those of asubmarine. A strong current or tide will cause anecho to have a doppler effect, but such anoccurrence is unusual.


from dead astern of the target is hardest for anoperator to identify, it can be done with a littleperserverance.

ECHOES FROM FALSE TARGETSNO DOPPLER

Echoes may be heard not only from whalesbut from large fish, such as blackfish. Schools ofherring or other small fish sometimes are large

, enough to reflect a strong echo./ 1414

If the water is shallow and the bottom ishard, rocky, or covered with coral heads, soundwaves are reflected strongly. Often thesereflections return as loud and clear as echoesfrom a target, but they have no doppler. Also, inshallow water as along the Continental Shelf onthe eastern coast of the United States, hulls oflong-sunken ships may return a very convincingecho. Because Nazi U-boats were so effective inthis area during World War II the shelf is litteredwith dead ships capable of hoaxing the

DOPPLER DOWN

71.44Figure 3-30.Value of doppler.

If an echo has no doppler, it may be from asubmarine's beam or wake, from a stoppedsubmarine, or other large, solid surface. Suchlarge reflecting surfaces produce sharp, clearechoes; the larger the area of the target, thegreater the strength of the echo. A weak, mushyecho, without doppler, is heard from suchobjects as riptides, kelp beds, schools of smallfish, and wakes that are breaking up. Thenumerous small reflections combine in randomfashion to form in irregular echo wave.

ECHO STRENGTH

The strength of the echo depends on thepower of the incoming wave. This powerdepends on the sound output of the transducer;the size, position, and movement of the target;and the cc:lclitions of sound transmission in thesea.

Often, you will receive the worst type ofechoes from the stern of a submarine. The targetarea is small and is broicen into multiple surfacesby the screws, the wake, and such, so that thereis a combination of reduced power andinterference. Don't dismiss weak, poor-soundingechoes as nonsubmarinc. Experienced sonaroperators will tell you that, although an echo

56

REPORT

S'JREACE VESSEL

E dERYTHING

JMPINF5UBMEP;ED

Figure 3-31.Report everything you hear.71.45

Chapter 3PHYS1CS OF SOUND

unsuspecting sonar operator into believing hiscontact is actually a submarine.

REPORT EVERYTHING YOU HEAROne of' the Sonar Technician's most

important tasks is to distinguish the targetechoes from other noises that tend to maskthem. Sonar operators hear many kinds ofechoes. Rocks, shoals, buoys. mines, surfacecraft, whales, schools of fish, wakes of surfacecraft and submarines. as well as the submarinesthemselves, can reflect sound.

Report every sound you hear, regardless ofwhether you can identify the echo. Figure 3-31illustrates a few of the many objects that mayreturn an echo or emit a sound. Do not delaymaking your report while you try to determinewhat you have detected. By the time you decideit's a submarine, it may be too late. Don't beafraid to make a report that may turn out to benonsubmarine. The safety of your ship and thelives of your shipmates are worth more than thetime spent or the ordnance expended on a falsecontact.

6 2

57

CHAPTER 4

BATHYTHERMOGRAPH

The travel of sound waves in the sea wasdiscussed in the preceding chapter. The factorsthat affect sound travel in water, alsomentioned earlier, are pressure, salinity, andtemperature. Sonar Technicians must have athorough knowledge of these factors to interpretcorrectly the information displayed by sonarequipment.

Increases in pressure speed up the velocity ofsound, making the speed of sound higher atextreme depths. An increase in salinity alsoincreases the velocity of sound. The effects ofpressure and salinity are not nearly as great.however, as the effects of temperaturechangesparticularly abrupt changes.

Information about the ocean ternperature ata given time can be used to predict what willhappen to transmitted sound as it travelsthrough the water. Because thermal conditionsof the sea are of the utmost importance to SonarTechnicians, a device, the bathythermograph(PT), is available for measuring watertemperature at various depths. From suchmeasurements, we can arrive at fairly accurateconclusions regarding the maximum range atwhich a submarine may be detected, as well asthe most favorable depth for the submarine toavoid detection. These two fundamentals areimportant considerations in antisubmarinewarfare. They influence the types of screensused and aid in determining the spacing of shipsin the screen.

Much of the data used in conjunction withBT information for determining sonar detectionranges cannot be included in this text because ofthe classified nature of the subject matter. Sonar

58

6 3

range prediction methods are presented in otherpublications, such as Sonar Technician G 3 & 2,NAV EDTRA 10131 and Sonar Technician S 3 &2, NAVEDTRA 10132.

EFFECTS OF TEMPERATURE

The speed of sound through water increasesat the rate of between 4 and 8 feet per secondfor each 1°F rise in temperature. This 4- to 8-fpschange depends on the temperature range of thewater. At water temperatures in the 30° range,for instance, a I' rise increases the rate of traveldifferently than does a 1° rise in the 70° range.

Ships and submarines of the U.S. Navyoperate in all sea temperaturesfrom nearfreezing in the polar regions to the upper 80s inthe tropics. To provide accurate range data,sonar equipment must be adjusted to thechanges in sound velocity.

Under some conditions. a pulse transmittedby sonar equipment may travel easily throughwater that varies greatly in temperature. Underdifferent conditions. the pulse transmitted maybe unable to penetrate a 5° temperature changelayer at all because it is reflected and scatteredinstead.

TEMPERATURE LAYERS

A pulse of acoustical power may providesonar reception out to several thousand yards ofrange. The same pulse, if transmitted into a layerof water (such as a sound channel that tends tokeep the pulse confined within it), may be ableto provide sonar data on contacts many milesdistant.

Chapter 4 BAT! IYTI I I'. RMOG RAPI I

Sound has a natural tendency to seek pathstoward the cooler layers of the sea. Because thetemperature of the sea normally decreases withdepth, the path of a transmitted pulse of soundis usually in a downward direction.

If a cross section or a profile of the sea'stemperatures were taken, a nornial conditionmight show a layer of water of uniformtemperature (less than 1/20 temperature change)from the surface to varying depths. Thiscondition is called isothermal. Next, there wouldbe a region of' water in which the temperaturedecreased rapidly with depth. Such an area isknown as a thermocline. Finally, for theremainder of the measured depth, thetemperature would decrease only slightly withdepth.

Thermoclines

The thermocline can play havoc with a pulseof acoustical energy. As the transmitted soundpulse reaches the thermocline, one of twoeffects is apparent.

First, the thermocline can prevent passage ofthe pulse, reflectine it back to the surface.Targets beneath the thermocline may beundetected. This possibility is one of the reasonssubmarine commanding officers seek the coverof such thermoclines, hoping to evade detectionby surface ships or aircraft.

Second, the thermocline can allow passage ofthe sound pulse but alter its directionconsiderably in so doing. This effect is calledrefraction. If a sound pulse enters a thermoclineat, for instance, a 300 angle from the sea'ssurface, it is possible for the allele to be alteredto 700 or more while traveling through thethermocline, and change again as it emerges. Theresult of this refraction can be a distorted pathof sound travel that affects the accuracy oftarget presentation at the sonar console.

SUBMARINEBATHYTHERMOGRAPH SYSTEMS

More information is required from asubmarine BT than from its surface ship

59

6 4

counterpart. Because salini:y, temperature, andpressure affect the ability of a submarine tomaintain desired operating depth, knowledge ofthese conditions and their effect on buoyancy isnecessary so that the divine. officer can maintaintrim of the submarine.

The AN/BQII-I A and the SSXBT( su b Ina r i ne expendable bat hyt h ermogra ph)provide the necessary data.

DEPTH-SOUND SPEEDMEASURING SET AN/BQH-1A

The AN/BQII-1 A is a completelytransistorited device used to provide accurateinformation concerning sound rangingconditions in t he su rrou nd i ig wa ter andbuoyancy during diving operations.

The equipment is capable of measuringsound velocity in seawater over a range of' 4600to 5100 fps. Accurate depth measurement isprovided by a depth element and its associatedcircuitry. Velocity of sound and depth of thesensing element which measures this velocity aredisplayed on a two-channel (pen and drum)servomechanism recorder (fig. 4-1).

Maintaining the trim of a moving submarineis aided greatly by indicating on the recorderchart a series of isoballast lines. These lines areprecalculated for various classes of submarines.Charts must he selected with isohallast linesprinted for that particular class of' submarine. Inindicating a trace that crosses the isohallast lines,action of the pen and drum gives the amount ofwater to pump or flood to maintain thesubmarine's trim.

Buoyancy changes, indicated by crossings ofisoballast lines, may be related to submarinedepth and also to velocity of sound in water.Both submarine buoyancy (upon which trimdepends) and velocity of sound in water aredefinite functions of salinity, temperature, andpressure. Inasmuch as a moving submarineencounters changine conditions of salinity,temperature, and pressure, the AN/BQH-1Arecording equipment must measure thesechanges in terms of' absolute values of velocityof sound in water. Sensitivity of thevelocity-measuring portion of this equipment is


4.1

0-.800FEET

1-1J1:4

PRESS TO SET4800 F10'SEC

RECOROERILLUIA

ON

SPARE

35.156

Figure 4-1.Depth-sound speed measuring set AN/BQH-1A.

sufficient to indicate changes in sound velocityof 1 fps when passing through a thermalgradient. Equipment pressure circuits arecapable of' indicating changes in depth ofapproximately 1 foot. This measurementrepresents the minimum readable definition ofthe recorder chart's pressure portion.

Isoballast curves are calculated in such a waythat individual curves pass throueh all pointswhere a loss in buoyancy with depth exactlyequals any eain in buoyancy resulting from adecrease in water temperature or increase ofsalinity. 6 5

60

Funct io nal Operation

To measure sound velocity and to ascertainvelocity gradients in the surrounding water, twot ra nsdu cer assemblies (sound heads) areprovide cl w i t 11 each depth-sound speedmeasuring equipment. One assembly is mountedon the upper (or sail) portion of' a ship. Theother device is mounted at the keel.

To obtain accurate information concerningchanging gradients and subsequent effects onbuoyancy during diving operations, it isadvisable to use the lower sound head whilediving, and the upper sound head while

Chapter 4 BATHYTHER MOG RAPH

ascending. By following this pattern, radiatedheat from the skin of the ship will wash awayfrom t he sound head. Radiated heat,consequently, will not interfere withmeasurements of gradients and indicatioir ofcorresponding buoyancy changes.

Sound velocity in water is measured in thefollowing manner: The AN/BQI-I-1A transmitsinto the water a pulse or acoustic energy. Thispulse travels from a transmitting transducerthrough the water and is received by a secondreceiving transducer. The time required for apulse to travel from transmitter to receiver ismeasured by means of electronic timing circuits.Thus, a direct measurement of sound velocity ismade. This method of direct measurementciiminates the need for correlating variousfactors of the ocean: salt content, density, andtemperature. plus pressure corresponding todepth at which velocity is measured.

Description of Controls

Operating controls of the AN/BQH-I Adepth-sound speed measuring set are describedfor the recorder and repeater. (Refer to fig. 4-1.)

RECORDER. Following are the majoroperating control switches on the recorder.

I. Power onloff recorder illuminationcontrol: This controi applies 400-hertz primarypower to the re.:ordcr. Ii varies the brightness ofthe internal chart 'omination.

2. Sound lie. d scH A two-positionswitch that perhnt 1 ,,..rator to select eitherthe upper or Ii mild head for displayingsound velocity on the recorder drum.

3. Depth scale select: A two-positionswitch that permits an operator to select eitherof two overlapping depth scales. One depth scaleis 0 to 800 feet: the other. 700 to 1500 feet.

4. Press-to-set 4800 fps: A spring-loadedswitcU, that, when depressed. applies a

calibrating signal internally generated in theparticular sound head in use. The switch acts asa system check of performance and accuracy ofsound velocity indication. It also assists inproper positioning of new recorder charts.

61

6 6

REPEATE R. The repeater unit is identicalto the recorder unit, but the repeater has nooperational controls. The only control on therepeater is the power on/off illumination switch.The repeater cannot be operated unless therecorder is also operating.

Operating Procedures

tieciu.:- the AN/BQH-I A and its associatedsound heads circuitry are completelytransistorized, no warmup time is required forproper operation. Following is the normaloperating procedure recommended for the set.

I. After lighting off the equipment andselecting the desired sound head, the recorderillumination control is adjusted to prr videsufficient light to clearly view the chart. (NOTE:When surfaced. the upper sound head is notimmersed. Care nrist bc taken to avoidenergizing this hcad until the submarinecompletely submerge,' 1

2. The depth scale select switch is set to thedesired depth setting (0-800 feet or 700-1500feet). The equipment is now ready for normaloperation.

3. The press-to-sct 4800 fps switch isdepressed and held until the velocity indicating'rum reaches a steady position. Indicatedelocity position should be 4800 Ups. (NOTE:

Cor each sound head the absolute value of the4800-foot calibrate velocity varies slightly. Testdata sheets supplied for the sound head in useshoulr' be consulted for exact calibratedreadings.)

4. In the preceding step, when the drumsteadies, the press-to-set switch is released. Thedrum should rotate and indicate the soundvelocity in the water at the sound head in use.

5. When both sound heads are immersed .

the sound head select switch may he rotated toselect first one, then the other, sound head.Each time the select switch is changed. the drumshould rotate to a position that shows thevelocity of sound at the sound head selected.When shifting from one head to the other. therecorder also indicates the difference in depthbetween the two sound heads.

6. The press-to-set 4800 fps switch isdepressed. When the drum rotates to a velocity


reading or 4800 fps, the switch is released. Thedrum then will rotate and begin to give acontinuous record of velocity and depth for thesound head in use.

Checks and Adjustments

Minimum front panel controls and adjustingknobs are contained on the AN/BQH.IA.Periodically, the operator should depress thepress-to-set switch and verify that the initialcalibration accuracy of the equipment ismaintained throughout an operating period.

Emergency Use

Because the velocity display and depthdisplay on the AN/BQH-1A are independent ofeach other, the recorder is capable of emergencyoperation on either independent channel. Iffailure of the depth circuitry occurs, an operatormay continue to supply useful velocityinformation by manually positioning the depthpen to a readable portion of the chart. In theevent of failure in the sound heads or drumcircuitry, depth information may still besupplied independently.

SUBMARINE EXPENDABLEBATHYTHERMOGRAPH (SSXBT)

The SSXBT automatically obtains andrecords ocean temperature data without thenecessity of changing the submarine's depth.The SSXBT is launched from the left signalejector of a submarine and provides a completetemperature profile from the surface of theocean down to 2500 feet. All of this isaccomplished in less than four minutes.

The submarine bathythermograph consistsof a ballistically-shaped BT probe contained in afloat assembly. The float assembly also containsa lifting body. When the assembly is launchedfrom the signal ejector, the lifting bodyseparates from the float assembly and isattached to the submarine by an insulated steelcable and a signal cable. The lifting body floatsin suspension behind the submarine and paysout a fine two-conducter cable as required. Thefloat assembly rises to the surface dereeling thesame fine cable as required by the ascent rate.

62

6 7

When the float assembly reaches the surface,atmospheric pressure actuates a pressure releasemechanism and the probe is released for its tripto the bottom, trailing the fine wire behind it.The wire relays back to the submarine thetemperature information until the probe reachesthe bottom or 2500 feet. At this time, the entireunit is deta -hed from the ship and sinks to thebo ttom.

SURFACE SHIP EXPENDABLEBATHYTHERMOGRAPH SYSTEM

The surface ship expendablebathythermograph system (fig. 4-2) has a sensorprobe, a cannister, a launch mechanism, and atemperature-depth recorder. The expendableportion of the system, consisting of thecannister and the probe, is seen in figure 4-3 andfigure 4-4. The probe weighs about 1 pound and

Canister Loading Brooch

Canister Wire Spool

Launcher RecorderCable (4-wireshielded)

OptionalEquipment',

TerminalBoard

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Alternating-Current PowerCable (3-wire)

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Figure 4-2.Expendable BT system.71.126

Chaptcr 4 BATIIYTIIIKRMOGRAPII

Figure 4-3.Expendable BT probe in its cannister.

.02$711P 414r.

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Figure 4-4.Expendable components and launcher.

63

6 8

71.118

71.127


is spin stabilized. It contains a thermistor, whichsenses temperature changes, and a reel of speci-alwire. The cannister also contains a reel of wire,and holds the probe. The launcher is essentially atube for holdinv, the cannister. It can be installedto proVide through-the-hull launching of theprobe, eliminating the necessity for sonarpersonnel to be on deck in rough weather. Therecorder (fig. 4-5) plots a track on a strip chartof temperature versus depth in real time. Thestrip chart is synchronized to the probe's rate ofdescent.

OPERATION

When you place the cannister in the launchtube, a waterththt electrical connection isformed between the probe and the recorder,causing the recorder to run for 2 seconds. Thisaction sets the automatic starting circuits, whichare activated when the probe hits the water. Theprobe is held in position by a pin protrudingfrom the launcher. Pulling the pin permits theprobe tc "all free of the cannister, into the

71.119F. lure 4-5.BT recorder.

water. (The cannister remins in the launcher.)As the probe starts its free fall, the wirecommences unreeling from the probe and fromthe cannister. This double unreeling actionallows the probe to sink straight down andpermits the ship to proceed unhindered.

When the probe strikes the water, anelectrode triggers the recorder. The thermistortransmits temperature changes to the recorderwhere they are plotted on the strip chart by astylus. At a depth of 1500 feet, :he probe's wireis exhausted and the recorder stops. A completereadout is obtained in 90 seconds from time oflaunch. Temperature range of the probe is 28°F10 96°F, with an accuracy of 0.4°F. Depthaccuracy is 2 percent or 15 feet, whichever isgreater.

Figure 4-6 shows a representativetemperature-depth profile. Only 6 inches of'chart paper are needed for each 1500-foot drop.

READING XBTRECORDER TRACES

The XBT, as already pointed out, provides acontinuous visual record of the temperaturesfrom the surface o: the sea to a depth of either1 500 feet, 2500 feet, or a point at which thewire breaks. The temperatures of various oceandepths recorded on the chart are represented asa graph of temperature against depth.

Fr 0111 the temperature curve, one candiscover the sound pattern of the sea at the timeof the hathythermoosaph observation. It is fromthe sound pattern that an estimate of maximumsonar range can be made.

'Fle variation of temperature with depth cancomplica ted. Many different conditions

h:. represented by the different types oftrace,;.

It is convenient to consider the water aslayers. In each layer the tempefature can changefrom top to bottom. Create a mental picture ofthe location or these layers from the appearanceof the chart. Visualize, too, how the

64

6 9

Chapter 4BATHYTHERMOGRAPH

Figure 4-6.Recorder chart.

temperature is changing. Study the followineexamples until each kind of layer can heidentified easily.

NEGATIVE GRADIENT

A negative gradient condition exists whenthe temperature of the water deereases withdepth. An \ HT, lowered through a negativegradient, produces a graph with the trace slopingto the left as depth increases. Figure 4-7represents a ;lace showing a negative gradient.This illustratioii depicts a particularly sharpgradient. which is quite common. Negative

71.120

gradients spell trouble for sonar operatorsbecause they result in short sonar ranges.

POSITIVE GRADIENT

Sometimes. layers are found in which thetemperature increases with depth. The traceslopes to the right. Althouuh usually observed incoastal waters, this condition may be foundanywhere. In figure 4-S a positive gradient isshown to exist down to a certain depth. beyond

aegative is firmed. Dependingor nepth of the start (1(.1)1 of the negativeg:.1-.ent. such a trace also me,,n trouble for


the Sonar Technician. As a result of thiscondition, the shipboard sonar operator observesunusually long ranges to targets near the surface.Little of the pulse's power penetrates thenegative gradient, however. The reason is thatthe higher temperatures in the lower part of thepositive gradient bend the pulse back up towardthe surface of the sea from which it is reflecteddownward again, and so on, forming a surfacechannel.

Any enere.y of the pulse that ,.!oes passthrough the negative gradient is reduced u,reatly,and the sound beam is bent sharply downward.Submarines operating 50 feet or more beneath

the top of the negative gradient are difficulttargets to detect. The shipboard SonarTechnician may get extremely long ranges on asubmerged tari4et near the surface (such as theunderwater section of the hull of anotherscreening ship), but he may be Linable to detecta submarine just a few thousand yards away.Should the submarine enter the positivegradient, however, it probably would bedetected.

ISOTHERMAL LAYER

An isothermal layer of water is one offo rm or nearly uniform tempera ture

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Figure 4-7.--Negative gradient.

66

Chapter 4BATHYTHERMOGRAPH

throughout. This condition is not confinednecessarily near the surface of the sea, but oftenis found between layers or gradients of markedlydifferent temperatures. An isothermal conditioncan be caused by waters of two diffen.ntt emperatures mixing. In this respect, itsometimes is referred to as a mixed layer.Isothermal layers are of importance in predictingthe path the sound pulse will follow. For thisreason Sonar Technicians must be able to readaccurately the top and bottom depths of such alayer. You are shown an isothermal condition infigure 4-9. Now look at figure 4-10 to see howisothermal layers sometimes are located in a

remperature profile of the sea. Notice that everytime a straight, vertical BT trace is recorded, thelayer of water between its limits is known to beisothermal.

DAILY HEATING

Daily heating of the surface water layer has amarked effect on sonar ranges. It produces acondition ASW men call afternoon effect.

When the surface is heated by the summersun, and the winds are not strong enough tokeep the surface water well mixed, the water

7 2

71.129Figure 4-8.Positive gradient.

67


Figure 4-9.Isothermal layer.

'1E

71.130

71.89 71.90Figure 4-10.Temperature profiles. Figure 4-11.Effect of daily heating.

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close to the surface may be several degreeswarmer than the water 20 to 30 feet down. Thiseffect is maximum in the late afternoon, andusually disappears at night as the surface coolsoff and water continues to mix. Figure 4-11 is asimplified illustration showing how traces mayindicate daily heating or cooling near thesurface.

An isothermal layer is seen at 0600 (localtime) on a calm, clear (lay. From 0600 to 1600the surface is shown gaining heat from the sunfaster than it can dissipate the heat back into theatmosphere. The surface temperature increases,and a negative gradient layer, represented by thecrossed lines, is established. This layer deepensas the heat penetrates, and diffuses downwardby conduction during the time the surface isgaining heat.

After 1600 the surface cools off byevaporation faster than it receives heat from thedeclining sun. The cooler and denser surfacewater mixes and may destroy the negativegradient layer. Sufficient cooling may occurduring the night to reestablish a singleisothermal layer, as shown at 0400.

(BT TRACE MARKING

The graph of each XBT drop must bemnotated to have any meaning. The readings)btained from a drop are not used only on yourhip; the information is also used to make upange prediction vehicles such as SHARPSShip/Helicopter Acoustic Range Prediction;ystern). If the time, date, location, etc., wereot known, the information would be useless for,ost d'op purposes.

iow to Mark the.B.T Recorder Chart

The m,trking of the XBT recorder chart has2en standardized, and the proper method is(plained below.

Enter on the face of each XBT recorderiart the information listed below in the samequence. If the format for this information is)t preprinted on the XBT recorder chart, writein.

70

Record N or S and E or W after latitude andlongitude, respectively. Record time and dateaccording to GMT. DO NOT OBSCURE THETEMPERATURE TRACE.

ShipCruiseLatitudeLongitudeTime (GMT)Da/Mo/YrObservation #Bottom Depth*

*optional entry.

BATHYTHERMOGRAPH LOGS

The BT Log, OCEANAV 3167/1(6-72),figure 4-12, is designed to meet two basic needs:(1) provide a message format for radiotransmission of synoptic BT data foroceanouaphic forecasting, and (2) provide theNational Oceanographic Data Center (NODC)with information required for BT analog anddigital processing. This radio message formatsupersedes all other formats previously used forshipboard or aircraft BT message reporting.

The instructions provided with the log sheetdescribe (1) how and where to mail log sheetsand recorder charts; (2) how to obtainadditional log sheets; (3) how to address radiomessages; (4) how to mark the XBT recorderchart after the observation is taken; (5) theprocedures for filling in the "REFERENCEINFORMATION," "OPTIONALENVIRONMENTAL INFORMATION," and"RADIO MESSAGE INFORMATION" portionsof the log sheet; (6) the required interpretationof the temperature-depth trace, and (7) specialinstructions for Navy use.

These instructions also serve to amplify thefollowing directives, the latest editions of whichare applicable and should be rigidly followed:

1. OCEANAVINST 3160.92. COMSCINST P3121.33. COMSCINST P3120.2

.._ 4. COMDT USCG INST 3161.15. NAVWEASERVCOMINST 3 140.1.

CHAPTER 5

BEARINGS AND MOTION

In studying bearings and motion, you mustremember that they are of two types. The twotypes of bearings are true bearing, which usestrue north as a reference, and relative bearing,which uses ship's head as a reference. Truemotion is the movement of an object across theEarth. Relative motion is the movement of oneobject in relation to another object.

This chapter discusses both types of' bearingsand both types of motion. It shows how theyare applied in determining the location andmovement of an underwater target, such as asubmarine.

With modern sonar, it is possible to locateand track a submarine with dependableaccuracy. To make full use of precisionequipment, it is necessary to evaluate bearingsand motion correctly and thus avoid settingerroneous values into the equipment computers.

REQUIREMENTS FOR LOCATINGSUBMARINES

Many landmarks and familiar objects on landcan be utilized for establishing a position anddetermining the location of a particular point. Incivilian life we were accustomed to suchdescriptive terms as "The third house on theright," or "Just a mile down the highway at thebig signboard." At sea, though, we must adjustourselves to doing without the convenience offamiliar objects and use other means at ourdisposal for locating a target. Targets visible onthe surface or in the air can be pointed out, butan unseen underwater object must be located ina manner that is both clear and accurate. Thismethod of location is accomplished by usingsonar to determine the objecrs direction and

71

distance from the sound transmitting ship. Inchapter 3 you read about the numerrsiis variablesaffecting the travel of sound bea in water.These variables greatly affect the precision withwhich the exact location of an underwater targetcan be determined. With present-day equipmentwe are able to compensate for many of thevariables and obtain exact positioninginformation. Electromechanical computers areutilized in solving many of the problems oftarget bearing and motion. It must be borne inmind, however, that direction and distance mustbe obtained first. then reported by the operatorMore the :oinputer can be set up to produce acorrect solution. Thus, the ability to determineand rep)rt the correct bearing and range asspeedily as possible is ot' the utmost importanceto the entire attack problem.

SONAR INFORMATION

Sonar provides the two items ofinformation --direction and distancefromwhich we derive all subsequent data. Directionand distance are referred to as bearing and range.Correct interpretation and transmittal of bearingand range information are deciding factors insuccessfully conducting any attack.

Bearing

The direction of the echo from the soundtransmission source is called the bearing. Bearingis measured clockwise in degrees ot' azimuth inthree figures from 0000 through 3600. Azimuthis defined as a horizontal arc of measurement ofthe horizon in degrees. One quarter of a circle is0900 and a full circle is 360°.


Until a few years ago, an allowance of 2-1/2°for error in bearing was considered within limitsof tolerance in antisubmarine attacks. Today,this standard of tolerance has been reduced toapproximately 1°. A bearing error of 2-1/2° at100 yards amounts to a position error of 4.36yards; at 2000 yards this error is 87.2 yards.With a bearing error of 1°, we are off target only1.75 yards at 100 yards, and 35 yards off at2000 yards. As you can see, modern equipmenthas provided geater bearing accuracy. No doubtfuture sonars will give even better accuracy, butremember that the finest equipment will alwaysneed a competent operator.

Range

The distance from the sound source to thetarget is called range. In sonar, range alv vs isexpressed in yards. With modern sonarequipment, range detection varies from less than100 yards to thousands of yards. Ranges can bemeasured to an accuracy of 1% of the rangescale in use. To achieve this accuracy, you musthave up-to-date knowledge of water conditionsand be able to make adjustments to theequipment to compensate for variations in thevelocity of sound.

Range is reported in thousands and hundredsof yards. Some sample ranges and the manner inwhich they are reported are listed here for yourinformation.

3000-"Range three thousand, closing."2500-"Range two five hundred."1750-"Range one seven five zero."1100-"Range one one hundred."1000 -"Range one thousand."800-"Range eight hundred."

"Kringe six six zero."-"RE. -ige one five zero."

i.)0-"Range four hundred, opening."

It should be noted that the word "yards" islever included in a report because ranges alwaysire given in yards.

One range report by itself is insufficient to.onduct an attack although such information asvhether the range is opening, closing, or

72

SONAR CONIAC1, BEARING ,30'

SONAR CONTAcT bEARINC 045

SONAh CCN7AC REARTNO 2 C

71.3Figure 5-1.True bearings are independent of

ship's head.

constant is of vital significance. A succession ofboth bearing and range reports is required todetermine target and location and motion.

BEARINGS

In establishing a bearing, we invariably musthave a reference point to ensure that thedirection is always the same. True bearing isreferenced to true north regardless of thedirection or motion of the ship. Relative bearingis always referenced to the ship's bow. In all

7 7

Chapter 5BEARINGS AND MOTION

instances, bearings are reported in degrees andare read clockwise.

Sonar bearings are reported in three figures,and you say "zero" instead of "oh.'' A sonarcontact due east of your ship is reported as

a.ir contact, bearing zero niner zero." If theconiaet were due west, it would be reported as"Sonar contact. bearing two seven zero."

Notice in the foregoing examples that theword "true" is not used. Unless statedotherwise, always assume that bearings arereported as true bearings. If a gyro failureoccurs, relative bearings must be used, and thesonar operator will add the word "relative" tohis bearing report. II he wishes, the operator canavoid saying "relative" after each report bystating "All bearings will be relative until furthernotice."

TRUE BEARINGS

To illustrate that true bearings areindypendent of the ship's heading. figure 5-1shows three different bearings. The ship and the

contact have been drawn in to show that,although the ship has a different course, the truebearing of the contact remains the same. In theillustration, compare the examples on the leftwith the examples on the right.

All shipboard and submarine sonar setsutilize a gyrocompass input to provide truetarget bearing by reading the sonar bearingmarker against the dial. Figure 5-2 shows thisdial as it is in a standard shipboard sonar set.The section enclosed within the dotted lines isthe area visible to the sonar operator throughthe glass window. The marker at the top, whichcan be seen through the transparent bearing dial,indicates the bearing to which the operator hastrained the cursor on the scope. Because thecursor normally is positioned in the middle ofthe target presentation, the dial marker indicatesthe center bearing of the contact.

RELATIVE BEARINGS

True bearings are the ones of principalconcern to Sonar Technicians because standard

45.29AFigure 5-2.Bearing dial assembly.

73

7 8


operating procedures are based on true bearings.You need to understand relative bearings,however, inasmuch as casualties to thegyrocompass necessitate shifting to relativebearing procedures.

Relative bearings are read in degreesclockwise from the ship's bow, which is always0000. If a contact is broad on your ship's portquarter, the relative bearing is 225°. If a contactis on your starboard beam, the relative bearing is090°. Figure 5-3 diagrams these two examples,illustrating how relative bearings are determined.

When the ship changes course, the relativebearing of a target changes. In figure 5-4 the shipchanges course 60° to the right. This coursechange causes the relative bearing of the targetto change from 090° relative to 0300 relative.

Relative bearings can be read on the sonarconsole from the same dial that 6ves truebearings, although not at the same time. If acomplete gyro failure should oceur, this dialautomatically indicates relative bearing.Occasionally, the gyro may act erratically for afew moments, causing the picture on the scopeto jump, making it difficult for the operator totrack the target. To obtain a presentation with

0 YOUR SHIPDE4O ALWOYL IS 900'

A RELATIVE.000.'

PORT 5T'EfDBOW, BOW

LL BEARINGS 0 .MEASURED 7/3,CLOCfMSE

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Figure 5-3.Relative bearings.

more stability, the operator can control theequipment so that a relative picture is presentedon the scope, the dial indicating relative bearing.

Figure 5-5 typifies a bearing indicator fromwhich true and relative bearings may be readsimultaneously. This type of indicator, used inearlier sonars, is a good example for showing thecomparr,on of true and relative bearings.

The outer dial, which is fixed, indicatesrelative bearing. The inner dial is free to rotate.When connected electrically to the ship's mastergyrocompass, it acts as a gyro repeater andshows ship's course and true bearing. Thediamond-shaped poiniel between the two dialsindicates the direction in which the soundreceiver is trained. Both relative bearing and truebearing are read by observing the position of thepointer.

True course is read on the inner dialopposite 0000 relative on the outer dial. Asshown in figure 5-5, ship's course is 045°, and acontact broad on the starboard bow (045°R) hasa true bearing of 090°.

STERN LINE INDICATOR

With modern scanning sonars the sonaroperator has an ideal picture of antisubmarine

(

45.298

7 9

74

0300 RELATIVE

0900 RELATIVE

Figure 5-4.Relative bearing change.45.29C


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45.29KFigure 5-5.Bearing and course indicator.

action. He not only receives the audio responsebut is aided by a video presentation 3600 inazimuth. The presentation is a true picture ofthe area surrounding the ship, and (withexceptions ioted later in the text) it does notchange with alterations in ship's course.

Although t he video presentation isindependent of ship's heading, the SonarTechnician needs to be constantly aware of theship's course for purposes of conducting searcharcs, performing control manipulations, andreporting sonar information. Ship's courseinformation is provided in the form of a sternline on the face of the scope. The stern line,illustrated in figure 5-6, is presented as anilluminated broken line, which, as its nameimplies, indicates the direction of the ship'sstern. If this line indicated the bow of the ship,it would be much easier to interpret ship'scourse. Because most sonar information comesfrom forward, however, the addition of the sternline indicator in that direction would tend toclutter the scope unnecessarily.

Normally, with the ship's gyro operating,own ship's movement does not appreciably alter

75n

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350 0 ®10

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45.29JFigure 5-6.Stern line indicator.

the presentation on the scope. Only the sternline indicator shows when the ship is turning orif a course change has occurred. When turningright, the stern line moves clockwise; whent u rn i ng left, it moves counterclockwise.Movement of the stern line alerts the operator tocourse changes so that he then can be preparedto make adjustments to keep the bearing cursoron target.

When looking at the scope it is best topicture the ship as in the center of a smallsegment of the ocean, with the ocean alwaysoriented to true north at the top of the scope.The ship turns in the center, and its direction isshown by the stern line to indicate thereciprocal of the true course.

GYRO FAILURE

When the gyro is operating, the top of thescope is north (000°T). When the gyro is


270 BEARING

CURSOR

TRUE PICTURE

000

Figure 5-7.Effect of gyro failure.

noperative, the top of the scope is 0000 relative'ship's head).

The first indication of a gyro casualty is theTratic movement of the stern line or theIlurnination of the red GYRO OFF light on theonar console. Any failure of gyro input to theonar causes the stern line to swing to 180°elative, where it remains as long as the gyroiputs are cut off. If the ship is headed for aarget when the gyro fails, the target echo moves) 0000 relative. Thus, the ship may be heading)1- a target bearing 090° true, but the target:ho is presented at the tOp of the scope.

The effect of gyro failure is illustrated ingure 5-7: Part A shows the scope with normaltro input. The submarine is located to the right7 center. The stern line is at 2700 and indicatesLat the ship is on course 090° true and headed,r the contact.

876

180

RELATIVE PICTURE

71.4

With a gyro casualty, the stern line willswing 90° counterclockwise. The entire videopresentation will change a like amount in thesame direction as shown in part B of theillustration. To remain on target, the bearingcursor must also be trained 90°counterclockwise. The dials below the scopes inthe illustration indicate the direction in whichthe bearing cursor is trained to maintain contact.CONVERTING TRUEAND RELATIVE BEARING7

Even though you lo gyro input to thesonar, you can easily determine the true bearingof the target if you know your ship's course andthe relative bearing of the target. If the relativebearing is 029° and the s p's course is 027°true, as in figure 5-8, you can see that truebearing of the target is 056°. The true bearing is


obtained by adding the ship's course and thetarget's relative bearing. Thus, by the formulawe have:

027°T + 029°R = 056°T

Now examine figure 5-9. The ship is on acourse of 180° true, and the target is at 251.°relative. Again, it is easy to determine true targetbearing by applying the formula as before:

180°T + 251°R = 431°T

This time the bearing is greater than 360°. Whenthe answer exceeds, 360°, you must subtractthis figure to obtain the correct answer. Thus:

I80°T + 251°R = 431°T 360°T = 071°T

Rules for Conversion

Certain rules are established for convertingtrue and relative bearings. After each rule isstated, the mathematical formula representing

4

SHIP'S HEAD

029° RELATIVE

'TARGET

056°

071°

251°/RELATIVE

4SHIP'SHEAD

180°

Figure 5-9.Target at 071 ° true.

41)TARGET

45.29G.2

the rule is given. The formulas are expressed infire control symbols. By means of thesesymbols, we avoid detailed explanations of thevalues or measurements. Following are the firecontrol symbols used in these formulas.

ByTrue target bearingBRelative target bearing

CoOwn ship's course

True target bearing equals relative targetbearing plus own ship's course. In formula, thisrule is expressed thus:

By = B + Co

If the true bearing, as computed, is greaterthan 360°, that value must be subtracted fromthe total. Our rule now is: True target bearingequals relative target bearing plus own ship'scourse minus 360°.

By = B + Co 360°

45.29F.2 If you know your course and the true targetFigure 5-8.Target at 056° true. bearing, the formula may be worked in reverse

779


to obtain the relative target bearing. Relativetarget bearing equals true target bearing niinusown ship's course.

B = By Co

If the true bearing is less than the ship's course,360° must be added to the true bearing beforesubtracting ship's course. Relative target bearingequals true target bearing plus 3600 minus ownship's course.

B T. By 4- 360° Co

If the true target bearing is 045° true andship's course is 270° true, for example, we findthe target's relative bearing thus:

045°T + 360° = 4050 270° = l35R

MOTION

As mentioned at the beginning of thischapter, the two types of motion are true andrelative. The Sonar Technician must have athorough understanding of both types of motionto interpret target movement correc'!v and toOve assistance in making an attack.

TRUE MOTION

True motion is the movement of an objectacross the Earth, using true (geographic) northas the reference point.

RELATIVE MOTION

Relative motion is the apparent tr7wementof an object in relation to another obje,:t. Donot confuse the concept of relative motion withrelative bearing. Relative motion is measured asapparent movement with respect to own ship.

You may have been unaware at the time, buton many occasions you have witnessed thesolution of relative movement problems. When abaseball player races to catch a high fly ball orwhen a football quarterback throws downfieldto a receiver, the players are estimating relative

8 378

movement. As an example, assume your ship ison a course of 000° .at a speed of 20 knots. Youare overtaking and will pass close aboard a shipthat is also on course 0000 but whose speed isonly 10 knots. As you close the ship, thebearings to him draw aft Eventually you passhim and he falls further and further behind. Hisrelative movement from you is approximately180°, but his true movement is 000c.

Following are three rules pertaining torelative r lotion that you must remember whenmaking an attack on a submarine. Figure 5-10illustrates these relative motion situations.

1. If range is closing and the bearings aredrawing toward the bow, your ship will passastern of the submarine.

2. If range is closing and the bearingremains steady, the ship will pass directly overtilt: submarine. (If the submarine were on thesurface, a collision would result.)

3. If range is closing and the bearings aredrawing aft, the ship will pass ahead of thesubmarine.

ADVANCE AND TRANSFER

When a ship changes course to lied for anew hca,ing, she does not me ve as a car does onland. Water is a fluid substance, and it does notallow tlie ship the advantage of go(1 traction.As rudder is applied to a ship, a shortensues before the rudder takes hold in the water.During the turn, the stern of the ship actuallyslides through the water. As it slides, the shiptends to advance in the same direction of heroriginal course. The distance the Jiip moves inthe original direction until she is on the newcourse is called advance. The amount of a6vancedepends on ship's speed, amount of turn, andamount of rudder angle applied.

During the change in course, the ship alsomoves at right anglos to the original course. Thedistance the ship moves at right angles to theoriginal course during the turn is called transfer.The amount of transfer, as with advance,depends on the amount of turn, ship's speed,and amount of rudder angle.

Advance and transfer vary with each type ofship and even with ships of the same type. Eachship, therefore, makes l7ce own advance and

314

SUB

.!;..pter 5BEARINGS AND MOTION

SHIP

al BEARINGS DRAWING TOWARD THE BOW.SHIP WILL PASS T ER N OF SUBMARINE.

SHIP

2 BEARING REMAINS STEADY.COLLISION COURSE.

270

280

290.

SUB

SHIP

c3 BEARINGS DRAWING AFT.ShIP WILL PASS AHEAD OF SUBMARINE.

71.5Figure 5-10.Relative motion shuations.

8 I

79


000T

TARGET

71.6Figure 5-11.Effect of advance and transfer

on bearing.

transfer tables for various rudder angles and atdifferent speeds.

As you can imagine, advance and transferwill affect target bearings during a turn. Allpossible situations cannot be explained herebecause therr are almost unlimited combinationsof target and attacker telative mcvements. If thetarget is on your port beam, for example, andhas the same course and speed you have, whenyou turn left to head for him, his bearing willchange to the right. Figure 5-11 illustrates theeffect of , vance and transfer on bearing whenthe target is stationary or nearly so.

BEARING DRIFT

When the sonar operator detects anunderwater target, he reports the bearing andrange. The conning officer then turns the ship tohead for thc reported target. As :he ship turns,the bearing cursor is trained back and forthacross the target to check for bearing width, andthe target is classified. The operator then placesthe cursor in the center of the target pip. Thecursor shows direction of sound reception. Itslength indicates range when the cursor line isadjusted to touch the target echo. With the shipheaded for the target on a steady course and at aconstant speed, with the cursor bisecting theecho, any change in target bearing results fromtarget movement. If the target moves to theright, the operator must train his cursor to theright to remain on target, reporting "Bearingdrift right." If the target moves to the left, hetrains his cursor to the left, to remain on target,and reports "Bearing drift left."

In an attempt to evade the attiking ship,the submarine will maneuver. The attackingship, in turn, changes course as necessary toreach optimum weapon firing position whilemaintaining sonar contact. Regardless of thenumber of course changes of the ship ormaneuvers by the submarine, the job of theoperator is to keep the cursor on the target.Correct bearings, ranges, audio response, andother target data can be obtained only when thecursor is kept positioned puoperly on the targetecho.

DOPPLER ANDTARGET ASPECT

Wlren contact is made on an underwaterobject, these questions require answers: (I)What is it? (2) Is it moving? (3) In whichdirection is it moving?

Classification steps, when executed properly,give the answer to the first question. Dopplerhelps to answer all questions. Doppler, anacoustic phenomenon was explained fully inchapter 3. Remember that doppler up means thetarget is headed toward you; dopplerdown means the target is headed away fromyou: and no dopplcr means the target is eitherbroadside to you and neither coming towardyou nor headed away, or it is stationary. Assumethat you have contact with a submarine. It hasdoppler, so it must he moving but in whichdirection? By this time the ship has turned tohead tor the target, enabling you to arrive at theanswer to the third question. 11 doppler is up,:.he target is moving toward the ship. If doppleris down, the target is moving away from theship.

The operator's job is to determine thedirection of target movement and report it. Ifthe submarine is headed directly at the ship, thetarget aspect will be direct bow and doppler willbe up. If you are headed at the target and thetarget has bearing drift the right with nodoppler, the target aspect is starboard beau'.Figure 5-12 shows the five bask- target aspectsanti their associated doppler. The degree ofdoppler is dependent on target speed. Forexample: Doppler of a direct bow target with ahigh closing speed would be r,_sported as

8 5"marked up."

Chapter 5 -BEARINGS AND MOTION

Target aspect is best described as the relativeposition of the submarine with respect to thesound bealn. Perhaps the easiest way a deciding,which aspect the submarine is presenting is tovisualize it in the center of four quadrants and.hy the process of elimination, solve for theproper quadrant. This procedure gives a roughaspect, and doppler and bearing drift will furtherdefine the exact aspect. Look at figure 5-13 tosee how this solution is accomplished. Assumethat your ship is headed for the target and thatinitially you have a steady bearing with high updoppler. which indicates that the ship and thesubmarine are headed directly for each other.N...xt, you detect a hearing drift to the right.with slight up doppler. Quadrants A and B areeliminated because a target in either quadrantwould have down doppler. A target in quadrantC will have up iloppler. but the bearing drift willbe to the le Therefore. you would report-Starboard bow aspect.-

As the ship attacks, she makes minor courseand speed changes. but these changes have little

or no effect on target aspect of doppler. If theship circles the submarine, however, or if thesubmarine makes a change in course. targetaspect will change. A change in doppler is thefirst indication that the submarine is changingcourse, and this change must be reportedimmediately. As soon as the new aspect can bedetermined, it also must be reported. During anantisubmarine attack (or series of attacks),aspect changes often. 'Me swiar olvrator's job isto detect, evaluay. and re;-.ort each change as itoccurs.

COMPUTING TARGET ANGLE

Target angle, which is a relative bearing.gives more precise information on the course ofa ship or submarine than does target aspect, buttarget angle is more difficult to obtain than istr.rget aspect. In considering a destroyer makingan attack on a submari;h' taxget angle is therelative bearnig Ii 1..:,royer from the

SUBMARINE

,

s

ASPECT DIRECTBOW

STBD PORT

B w

sTBp BEAM

-

PORT BEAM

PORT

OTR

BEARINGDRIFT NONE RIGHT LEFT

1

[ .TIR

: EFT

.10

-1-

LEFT

mop EDO\

DOPpLER uP MODERATEUP

Figure 5-12.--Ta(get aspect.

81 S

STBDoTr:

ATE'

"cRN

NONE

^OWN

71 7


DOPPLER DOWN

A

BEARING DRIFT LEF-T

NO DOPPLER

BEARING DRIFT LEFT

DOPPLER UP

c,e-sN''

DOPPLER DOWN

BEARING DRIFT RIGHT

NO DOPPLER

BEARING DRIFT RIGHT

DOPPLER UP

OWN SHIP

Figure 5-13.Solving target aspect.

Imagine that you are on board a submarinelooking at an approaching destroyer. Therelative bearing of the destroyer is 090°, whichindicates it is approaching on the submarine'sstarboard beam. As viewed prom the destroyer,ti.2 submarine's target angle is 0900 becausetarget angle is the relative bearing of the shipfrom the tIrget. measured in the horizontalplane from the bow of the tarnt clockwise from

8782

71.8

000° to 3600. Lik farget aspect. target angledepends on the 's heading. When thesubmarine changes target angle changesaccordingly.

Figure 5-14 illustraws several target angles.Also shown are angles on the bow (discussedlater) and related doppler. Notice that no matterwhich direction the ship is heading, the courseof the submarine governs target angle.


You may be curious as to why target aspectis ix) important when target angle pro Je., oioreaccurate information. Aspect is giv,m :Is ageneral indication and can be reported after onlyfour or five transmissions, based on doppler andthe first indication of beiring drift. Target angle,on the other hand, is derived from more precisedata. It is necessary to know the submarine'scourse, which can be determined only bytracking the submarine for several minutes. Inmany attacks, it is difficult to report an accuratetarget angle because of radical maneuvers by thesubmarine or because of insufficient time todetermine targe: Igle. In such instances, targetaspect information necessarily must suffice forthe conning officer to estimate the target angleand adjust own ships course accordingly.

In antisubmarine warfare, there is little timebetween detection and attaci.. Target aspect

RELLT,VE EEaR,`,-;'0

/4ZIE22DZ'''?

6E:.v33 390

STEPP4

Sr4kBGA=.:

Figure 5-14.Target angle.

,05

DC,..LER

DOWN

DOWNrpom

SL,C,w'r

C';

thus affords a means of reporting reliableinformation quickly.

Aboard a submarine, target angle is derivedby a method known as angle on the bow (Ab).Where:as the ship uses 360° for ,:omputing targetangle, the submarine uses only 1800, specifyingport or starboard side. To illustrate, a destroyerhas a submarine bearing 070° relative. Aboardthe submarine, the target angle would bereported as "Angle on the bow. starboard 70.A relative bearing of 345° front ship to target isreported on the submarine as "Angle on thebow. port 15.- Figure 5-14 illustrates someangles on the bow.

Target angle is not all guesswork. It can hecomputed accurately by using this formula:target angle equals true hearing plus 180' minustarget course. Oxpressed in lire control s:,..mhols.the formula r2ads: Bts By + 180° where

ByCt

= target angle= true bearing= target course.

Assume that you are on a ship and tracking asubmarine bearing 270°. course 135. Find thetarget angle by appIying the preeediag formula.Thus:

Bts = 270' + 180° 1 35'Bts 4500 1350Bts = 315°

An example of computing this target angle isseen in figure 5-15. In effect. the +1800 in theformula allows the viewer tf ,,laces Sothat he may see his ownthe target. Compare tiie reli c. in' I ;hedestroyer from the suhinariicomputed for target ar' e.

If the product o. By is less thantarget course. 360° be added to icequation before subtracting target course.Example: ,\ target is on course 2700. bearing0100.

Bt.,; = 010° + 180'Bts = 190 + 300°Bts = 550' 270°Bts = 280

71.9 Angle on the how (Ab) may he ,:omputed inthe same manner as target ac, e. with one

83


o

os

TARGET

......--

'6.?°C

.,' a*.'46

,k'.0' % °L, -k

g'....e? BtsCI.. N

g56- 2

'4./.,, S'. *-.

pe. o0 \0\''''' ';''''' o°'..1/44,61/Tifinirdola\t',\°"* C'

o

TRUE BEARING CIRCLESSHIP

w11111111M1111100,,,I

f=4-e A b

y

/1/

cs<,01,

RELATIVE BEARING CIRCLES

Figure 5-15.Computing target angle.

exception. Because the answer is in dep-ees ofrelative bearing, it must be converted to degreesport or starboard. Referring again to figure 5-15.you see that the destroyer bears 0900 true and is

course 2400 .

Ab = 0900 + 1800 240cAb = 270° 240°Ab = 0300 or starboard 30

84

o

g

B yoc:

0,

*',11,1 ii1;y1t

45.29H

If the answer is greater than 180°, subtract theanswer from 360° to obtain angle on the bow toport.

Target course c,an be determined by theformula Ct = 13y -tr. (180 ALA If Ab is to port,the resultant of the figures in parentheses issubtracte(i from By. Conversely. if Ab is tostarboard, the solution within parentheses isadded to true bearing.

CHAPTER 6

PRINCIPLES OF SONAR

The earliest sonar equipment was a passivedevice, a simple hydrophone lowered into thewater and used to listen for noise created by asubmarine. The only indication of a target wasan audio tone. Bearing accuracy was doubtful,and ranges were strictly guesswork.

Today's sonar equipments provide highlyaccurate ranges and bearings. They presentinformation both visually and aurally. Bothactive and passive types of equipment are used.

Alt hough specific sonars and relatederliipments are not covered if, this chapter, basicprincipl..s of operations given herein areapplic.Jole to all sonar equipments.

SONAR SYSTEMS

Two general types of scuar systems areemployed for the detection of targets. They arerefer..-.:d to as active and passive sonars.

Active sonars are capable of transmittingunderwater sound pulses i-hat sta.e targets andare returned in the form ot echoes. Echoesreturned indicate the range ann bcarinc; of thetarget.

Passive sonars do not transmit sound. Theymerely listen for sounds produced by the targetto obtain accurate bearing and estim,!!:d rangei-ifortnation.

Active sonar systems norm:Jlly ar2 assocated.-vith surface ships, whereas passive systemsIsnally are associated with submarin-s. Newerauface ships, however ,arate passive

systems in addition to their activ sonars.Submarines, although still relying primarily onpassive systems, aiso employ active sonars.

ACTIVE SONAR

A simplified active sonar system is shown infigure 6-1.

Active sonar systems are used to detect thepresence of ships, analyze shoreline and bottomcharacteristics, and determine bottom depths.The basic system consists of a transmitter, oneor more transducers, a receiver, id displays andcontrols of various sorts. The transmitter has asource of power and a r'.2ans for modulating thebasic power in a m..iner suitable for theparticular application. In general, the basictransmitted power is frequency modulated assingle pulses at a pulse repetition frequency (prf)dependent on the system range.

The transmitter power is converted fromelectrical to ac,:istic energy by means of thetransducer for tiansmission of the sonar signalinto the water. Received signals or echoes arereconverted by the same transducer (or by ad;fferent transducer in some sonar systems)from acoustic back to electrical energy. Thereceived signal from the transducer is processedin a receiver. whcrc various amplification,demodation. and comparison operations areperformed. The output of the receiver, in theform for proper presentation of target data. isfed to display and control units. The dkplaysinclude aural types. such as loudspea :. andearphones, and visual types, hugoscilloscopes. (CRT) cathode ray tut-w:- iucrecorders. and indicator lamps.


REFLECTED, ECHOES

ellTRANSDUCER

TRArISMITTEDF ON A R

S.GNALS

Searchli2ht Sonar (Directional)

AMPLIFIER

DEMODULATOR' 1

COMPARATOR

TRANSMITTER

POWERMODULATOR

POWERSOURCE

Figure 61.--Simplified active sonar system.

Early active sonars utilized the searchlightprinciple for transmitting sounds. Like thesearchlight, the transducer had to be trained to aparticular bearing to transmit sound on thatbearing. The sound beam was narrow in bearingwidth (about 5°). consequently the echoes werereceived from only a small sector of thesurrounding sea. An arrangement of this typewas necessary at that time because sufficientpower for omnidirectional transmission couldnot be generated. The scanning sonars inwidespread use today develop tremendouspowerenough to be transmitted 360° inazimuth simultanously.

Late modifications to active sonars all°, theselection of directionally transmitted sonicpulses. somewhat related in orinciple to `_he

earlier searchlight sonars. This feature. calledrotating directional transmission, is discussedlater.

The main disadvantage of the searchlighttype of sonar was the length of time required toscan the area around the ship. Search procedurescalled for the operator to transmit. listen forechoes, train the transducer to a new bearing.transmit, Ikten. and so on. first on one side

86

71.135

the ship, then the other. It was possible for asubmarine to slip by undetected on the port

example, while the operator wason the starboard side. Moreover,

side, forsearchingmaintaining contact with a target that had arapidly changing Laring required a high degreeof proficiency on the part of the operator.An ot her disauvan tage was that searchlightequipment had only an audio presentation,whereas today's scanning sonars provide both avideo and an audio presentation.

Scanning Sonar

Modern submarines Lind ASW ships areequipped with scanning sonar, which transmitssound pulses of high energy in all directionssimuitaneously. One of the features of scanningsonar is a cathode ray tube (CRT) display of allunderwater objects detected in :he areasurrounding the ship. Target ec:ines appear asbright spots On the CRT. similar to the displayof a radar's PPI.

Some of the data that you may learn fromthc CRT presentation are as follows:

I. The size of the target may be estimatedfrom the size of the echo. Don't rely too heavily

Chapter 6 PRINCIPLFS OF SONAR

on this fea ture. though. because echoappearance depends on such factors as targetaspect, range. and equipment perlormance.

2. The distance of the echo front the centerof the CRT represents range to the object fromyour ship when the CRT is used in the shipcenter display (SCD) mode.

3. True bearing of the object can bedetermined directly OH the scope.

4. Targe t movement can be determinedfrom its scope presentation. Fixed objects suchas reels and sunken ships will move in adirection parallel to your ship's movement andin the opposite direction. Nloving objects mayhave motion in any direction with respect toown ship.

5. The wake of a submarine often can 1),..

seen. By examining the wake. you may be ableto establish a submarine's heading even heforeits movement he determined by tracking.

6. Subm,d -!es that are too far away tordetection by ecno ranging may yet L'init enoughnoise to be detected. Under these conditions, asmall segment of the scope appears to be filledwith a rippling pattern. The general direction olthe noise source can he ascertained y takingbearing to the center of the noise pattern.

TRANSDUCERS

Knowledge of the design and function of thetransducer is the key to understanding theprinciples of sonar, whether of the scanning orthe searchlight type.

A device for converting onc form of energyto another is a transducer. In sonar the acousticenergy of the sti.md waves is converted tomechanical energy in the form of oscidation ofthe molecules of the medium through which thesound travels. These oscillations cause asynchronous variation in pressure of themedium. The sig,ials generated or received by"lie electronic circuits in sonar equipm,snt are inthe form of electrical energy. The sonartransducer acts as the link between the waterand the electronic eireuits of the sonarequipn.:nt and converts the electrical energy toacoustical energy and vice versa.

87

9 2

There are physical phenomena which exhibitthe ability to change electrical to mechanic.ilenergy and mechanical to electrical energy. and\vhich are emoloyed in sonar tiansdueers. Theseare the eleetiostrictive. the piezoelectric and themagnetostrictive effects. Materials ex hibitingelectrostrietive and piezoelectric properties aregenerally of crystal:ine or ceramic nature. Theychange dimensions \viten subjected to an electricfield and develop a voltage potential bet \veentwo opposite faces when mechanically stressed.Materials exhibiting the magnetostrictive effectchange dimensions when subjected to a magneticfield and change magnetic permeability whensubjected to mecharical Llmlge in

rmeabilitv chang:s 'ity of anymagnet(,.: field in the pre ,c material.

Variation in the strength of the electric ormagnetic neld at a frequency ii the acousticspectrum will cause acoustic waves to begenerated by such material. When thetransducers are placed in wat:H, such acousticwaves can (hen be propagated from the materialbi ate:. V. nen nind wa,'es impinge uponsucii mdterial after propagation from the water,the mechanical stress resulting from thepressure variations will cause variations in thefield strength (electric or magnetic) which inturn generate electric signals in suitable circuits,

Magnetostrictive Process

Magnetostriction is a process wherebychanges occur in metals when they are subjectedto a magnetic field. Depending on the materialand the strength of the magnetic field. somematerials will expand and. :Mlle will contract,hut independently of ,:te direction of theapplied field. Nickel is the most :iommonly usedmaterial in magnetostrictive it:HISC.:U.cers bQL'aitSC

xhibits a very large magre',-(...trictive effect.NILL1 contracts in a magnetic held to an extentlargely proportional to the intensity of the field.

The nickel elements in transducers aregenerally one-half wavelength long and aresupported at the :Lentral node so that themaximuni amplitude of vibration takes place atthe ends. In one type 1 tri!nsducer. theelements are niAel tubes. In incwase tiw area01" the active race in contact with the water in


this design, a series of tubes or rods are attachedto a diaphragm. The diaphi.agin becomes theactive face of the transdncel .1-he dimension ofthe tubes and the diaphragm plate is designed tomake the transducer mechanically resonant att lie opera ting frequency for maximumefficiency.

Because the nickel contracts for eitherdirection of magnetic field, an applied ax.sinusoidal field will cause the nickel to con traclfor each half of the a.c. cycle, resulting in afrequency of induced vibration twice that of theapplied Field. In a transducer, the sinusoidalmagnetic field is obtained by winding coilsaround nickel rods, tubes, or stamped elements(stamped and stacked in various shapes), andimpressing a current at the desired sonar signalfrequency through the coil.

It is generally desired that the vibration andthe resulting acoustic signal bc of the samefrequency as the electric signal applied to thecoils. This is accomplished by superimposing alarge d.c. polarizing magnetic field on the nickelelements by means of a d.c. polarizing currentthrough the coil or directly by permanentmagnets. If the d.c. field is larger than the a.c.signal field, then the resulting magnetic field willalways be in one direction, with its magnitudevarying with the a.c. signal. The change in nickelelement length will thus be synchronous withthe a.c. signal.

A d.c. polarizing field is ako needed forapplication of the converse magnetostrictiveeffect. If the nickel element is subjected tovarying longitudinal mechanical forces (acousticpressure waves), the resulting stresses change themagnetic permeability of the nickel. If a d.c.magnetic field is present, the permeabilitychanges will cause corresponding changes in themagnetic field intensity. These field changes willin tern induce a varying volt:..,e in the coilwound around the nici,el clement which willvary proportionally with tfw impinging acousticwaves. Without the ambient d.c. polarizing field.no voltages will be induced in the coils.

In the searchlight or directional type oftransducer, several hundred nickel tubes arearranged in a circle and mounted on one side of

9 3 88

,

71.48Figure 6-2.Scarchlightii,lgnetostrictivc V.ansducer.

a metal plate called a diaphragm. hach tube iswrapped with a coil of wire to preventfrequency doubling. When an alternating currentis applied to the coil, the tubes shorten andlengthen at the rate of the all.:raatingEach tube is polarized by a constant magneticfield, usually supplied by a permanent magnet.During one half cycic of the applied signal. thea.c. voltage and the polarizing field add: duringthe next half cycle. th:v oppose each other, andthe magnetic field is always in only onedirection. ftc contractions of the tubes thus arefix d to the a.c. frequency.

As the tubes contract and expand. thediaphragm vibrat.., and produces an acousticsignal of the same frequency as the appliedalternating current. A magnetostrictivetransducer used in searchlight sonars is :hown infigure 6-2_

Transducers employed with solll,* scanningsonars also operate on the principle ofmaiiiictostrict ion. Instead of nickel tubes,

Chapter 6 PRINCIPLFS OF SONAR

however, the transducer elements have nickellaminations pressed in a therinoplastie material.Rich clement contains a permanent magnet forpolarizing the nickel. Several elements ;Iremounted vertically to form I stave, and 45vertical staves are arranged circularly to Corm thetransducer. A scanning transducer is shown infigure 6-3. An exploded view 01 a portion of astave is seen in figure 6 4.

Many types of o,ieration.il scanning sonartransducers are mag ictostrictive. kxcept forvitiriations 1 *111COSi. ii, they are similar indesign. i type shown in figure 6-3 is acylindrical unit approximately 19 inches indiameter and 2 7 inches long. and has anoperating frequency of 20 kilz.

i.49Figure 6-1Scanning magnetostrictive transducer.

8 9

D4

Flectrically, the magnetostrictive scanningsonar unit acts as two independent transducershoused in a eonimon container. One of theindependent units is the search section. Theother is !he maintenance of close contact MC( ')section, located above the search elements.

The search section is made up of -Is verticalstaves. Filch stave consists of nickel 1..alillatiOnsand a polarizing magnet. llectrieall . hi. stavesare independent 01 one another.

As its name implies, the MCC scion is usedto maintain contact on a close-in submarine. TheMCC elements transmit ill a delayed sequencefrom the top down, cansing a phase delay 01 thesound beam, which results in the top of thebeam bending down toward the delayed portionof the beam. The effect resembles refraction.'Transmission is at a down v. iird angle ofapproximately 30'.

Because the elements are so placed that theycan cover a 3 60' area, there is no need to rotatethe transducer in scanning sonar. Such ana rra ngcnient provides video coveragesimultaneously on all bearings. Audio overageis afforded by training a cursor to the desir.bearing. Most present-da. magnetostrictivetransducers arc built along the sa Me generallines. Physical chmensions vary according to theoperating frequency and power output desired.

Piezoelectric Process

Thc piezoelectric effect. which is a Corm of,.trostrietion, is the electric polarization

produced i-)y mechanical strain in certain classesof erystais. The polarization and the electricpotential induced by it is proportional to thestrain and changes sign with it. In the cot:versepiezoelectric etct. an electric potential acrosst he crystal face produces a mechanicaldeformation proportional to the induced electricpolariz..tiHi: nd of the :;:line sign. Picmagnitna,. H this effect varies for crystals ofdifferent materials .. for the clifferent axes ofthe crystal.

Matcriak most commonly used for sonartransducers have included quartz, ti,Rochelle salt (sodium potassium idrtralc I.ammonium thhydrogen phosph.

INTROD1V HON TO SONAR

lithium sulphate. Suitahle largc t tiar.z crystalsare difricult ohlain. \lost crstal transducep,use Rochelle ...III :Ind ADP hCC:IIISC C

a strong piezoelectric effect and are easih. grownto the desired S. liecatINC Rocncdc salt

cannot tolerate high temperatures to which j

may he exposed during use or storage tit willdisintegrate rroin internalk generated heal it

used t(1 transmit Ingh power I'm ;Inv Icn:Ithtime), it has generally heen displaced hv ADI):ind lithium sulphate. Because Rochelle has

the strongest piezoclectrk: elfect, it is still II'Nedtr,111SLIIIC,r: and for low-po\cr

;ipplications. I urtnaline is used hi. calihrationtransduccis het..ausc it is rclativcly oi;:...!Tsirov tolemperatule changes.

A crystal transducer Is constructed hycementing or mounting a stack of quarter-wavecrystals to i heavy steel hacking resonator platca I so on e -quarter wave-length thick. Theassenthly is mechanically resonant :it theoperdlinr. IrcquenCy with .1 notlit :it tilt.' ifficifaccol (he phito and cry,;tals, and ma \ inium;implitude at tlic free end of the cryst;i1s.

Since hoth Rochelle salt and Al)l' aresoluhle in water. the crystal ;isseml,k using !hes,.

!s 5

f POLARIZINGMAGNET

PRESSURERELEASESTRIP

- I .4 hilr4,- IIONS

Figure 6-4.Exploded softy; of one s- !ning ser transduc,:r stave.

90

71.50

Chaplet Ii PR INC111 ( S( )N,A

materials is a sealed enclosm.', 1.0 pemnit soundpropagation, the elk-10,111e imist be Idled %).iththoroughly dehydrated liquid. Castor ,,!1 iscommonly used beeause the Lelocity ot sound illit is almost the same ;is that II seawater. tiounklpropagation from the castor oil 10 I lie seil %vat ciis via a thin metal diaphragm forming the lace oithe transducer assembly, shown in figurethrough a diaphragin ti ltho4 nibherrubber which has a "c resistance equalto that of the \valet 1.

When used for the mil \quoinelectric signal is produced by the cryst,il if thefrequency of the received sound is tlw same .1".the resonant frequency or the

Electrostri, t' ocess

Whet,dielec."phenol

Het:1.11C fi,..1)1 is ljtc across ;1

deform:J. I hischange in diiiiensions is callcd

nIAPHRAGM

CASTOR OIL

CRYSTALS

BACKING PLATE

CP TAL. TRANSDUCER

Figure 6-5.Crystal

electiostiactioll and Is independent of thednection (sign I ot the electric held andpropoi tional to the squaw oi IiHd intensify,III the cr% slat traiNluceis, the electrostrictivemeet is present but linit.:11 .maller than thepiezoelectric effect and is ignored. However,w i t h F 1 1 1 1 1 1 I i t It., :C. :1 I:Cr:Inuit:, I IR'cicknodrictiVe t,'I ct is Lir!'e in compalison withhe piezoelectric et feet .

Cerainie fon transduceis has the advantagetoo..1- cr), stals in that the ceramic can be moldedto ;my desired shape. This property isp.micularly desuabl, for making c lindrical5oj,I1111111!! Or 011111idirt.*:11011:11 llantithiCers. Thecon% er,,L. ekctrostriction, the Chanr.e in electricrottmlials %Own the material is stressed. Likesplac.' only when :1 constant polarizationpot, nti:11 is prcsent. The a.c sonar signal is thussupernnposed on the larger d.e. polarization, andthe material dimension will vary directly withthe magnitude of the resultant potential. Thepolarization 01 cloctro'drictive materials is thus,malogims to the magnetic polarization requiredf or magnetostrictive materials. Without thelarizatiOn, mechanical .tresses will not

oduce lii ele, try potenti.H.

all !nsducers now being built arc ofthe c, Ceramic: compounds have highsensith ,ty, ruth taH:H.y with changingtemperature and pi ssure, relativHy lowcosts.

MODERN ACTIVESONR THEORY

Hue thcory or modern active sonar operationbest be understood by breaking it downinto three basic functions: transmission,

reception, and presentation. A block diagram of3 representative sonar system is seen ill figure6-6. The diagram shows only the system's majorunits and ntain signal p.aths.

Transmission

-Transmission of the sound poly,: is initiatedin the control-indicator, which is comprised of

71.136 the receiver. audio and video ch-lonels. controlcircuit,;. and keying circuits. Puise length is also

91

(.;;


EC-0NTR-07 A-1-/37 1 E

Z-SPEAKES

RECEIVERAUDIO

CHANNEL

RECEIVERVIDEO

CHANNEL

RECEIVER / SCANNE R

VIDEOSCANNING

SWITCH

CONTROLCIRCUITS

KEYINGCIRCUiTS

lo.LSWEEP

GENERATOR

1 1

AUDIOSCANNING

SWITCH

41

PREAMPLIFIER

SCANNINGTRANSDUCER

Figure 6-6.Basic active sonar system block diagram.

determined at the control-indicator by the sonaroperator. The keying pulse from thec on t rol n d icator triggers the transmitteroscillator in the receiver-scanning systemassembly and actuates the transmit-receiveswitch in the audiofrequency (af) amplifier. Inthe receiver-scanner the pulse is modulated tothe equipment operating frequency, amplified,and delivered to the sonar transmitter where it isfurther amplified to the power level required fortransmission.

The output of the sonar transmitter is fed tothe transmit-receive switch in the af amplifier,then to the transducer transfer switch whereselection is made between NORMAL or MCCoperation. The signal then goes to the transducerwhere it is converted to acoustical energy andpropagated into the water. The shape of thetransmitted signal resembles that of a hollow

9",

9 7

71.137

cylinder (or sphere, depending on the shape cfthe transducer), which expands in diameter as ittravels outward. The thickness of the cylinderwalls depends on the puise length selected bythe operator. (See fig. 6-7.)

Reception

If the transmitted sound wave strikes anobject having sufficient reflective characteristics,a small portion of the signal is returned to thetransducer. In the transducer, the acoustic signalis converted to an electrical signal by thepiezoelectric effect of the receiving staves. Eachof the 48 staves has its own preamplifier, locatedin the af amplifier. After preamplification, thesignal is sent to the video and audio-scanningswitches in the receiver-scanning switchassembly.

Chapter 6- PRINCIPLES OF SONAR

The video-scanning switch rotatescontinuously, thereby sampling noise signals andechoes from ail bearings. The audio-scanningswitch is positioned to any bearing selected bythe sonar operator. Signals from the scanningswitches are fed to the receiver section of thereceiver-scanner where they are converted tosuitable frequencies and amplified forpresentation.

Presentation

For the returning echo to be of any value, itmust be presented in such a manner that thesonar operator can interpret ithe information itrepresents. The echo is presented to the operatorboth visibly and audibly.

The manually positioned audio-scanningswitch feeds the signal to the audio portion ofthe receiver, which is of the superheterodynetype. Incorporated in the receiver audio circuitsis a control for eliminating the effect of ownship's speed on the reverberation pitch. Thiscontrol is called the own doppler nullifier(ODN). It removes own ship's doppler effectfrom target echoes, ueatly aiding the operatorin target classification. From the receiver theaudio signal is sent to a headset position at thecontrol-indicator and can also be fed toloudspeakers.

After the output of the video-scanningswitch is processed in the video portion of thereceiver, it is dis2layed at the control-indicatoron a cathode-ray tube. The sweep on the CRT isa spiral scan, which is synchronized with thevideo scanning switch. (See fig. 6-8.)

One method of obtaining a spiral scan is torotate the field of the deflection coils aroundthe CRT, simultaneously applying a sawtoothvoltage to the coils to cause displacement of thesweep with each succeeding rotation of the coil.For clarity of explanation, the coil yoke ismechanically connected to the video-scanningswitch. As the video.scanner and deflection coilrotate, the sawtooth voltage causc the sweep tospiral outward from the center of the scope at alinear rate. On reaching the scope's outer edge,

full deflection is achieved and the sweep is thencut off.

Rotation of the ss:anner is at such a speedtnat you don't see a spiral sweep hut whatappears to be an expanding circular sweep. Anecho is seen on the scope as a brightening of thesweep at a distance from the scope center and ina direction corresponding to the target's rangeand bearing.

During the interval between the , nd of onesweep and the beginning of the next, the cursoris electronically produced on the scope. Becauseof the persistency of the CRT, the target echoremains visible for a short time, allowing theoperator to determine accurately the target'srange and bearing. Bisecting the echo with thecursor gives the bearing of the target. Byadjusting the length of the cursor so that its tiptouches the echo, the target's range isdetermined.

Also located on the sonar control-indicatorare various switches and controls. Their purposeis to give a better target presentation. Theseswitches and controls, together with completeoperating procedures, are explained in themanufacturer's technical manual supplied witheach sonar system.

Rotating Directional Transmission

Convention il scanning sonars formerly wereof the type j.c._,t discussed: that is, only

93

f) 8

PULSE LENGTH

SOUND CYLINDER

71.52Figure 6-7.Pulse length determines thickness nf

sound cylinder.


o in n idirec.ional transmission was possible.Modern sonars have an operating feature calledrotating directional transmission (RDT), whichoperates on a principle similar to the searchlighttype of transmission. The RDT provides greatert ransmitted power than the conventionalscanning type, affordine improved sensitivityand detection range.

At any instant of RDT, the sn2.nal is theresultant of phased excitation of several adjacenttransducer staves, resulting in a source levelimprovement that is characteristic of directionaltransmission. Excitation of the transducer stavesis caused by the output of a transmit scanner,which operates much like the video-scanningswitch of a conventional scanning sonar.Trans.nission is accomplished in a sector (up to3000 wide) which is centered on the bow or on a

A STEP-BY-STEP GENERATION OP SPIRAL SCAN

selected bearing, depending on the type ofoperation chosen by the operator at the controlunit.

PASSIVE SONAR

Passive sonar, as its name implies, dependsentirely on the target's noise as the sound sourceinstead of the returned echoes of a transmittedsignal. Target detection is achieved at greatranges through the use of highly sensitivehydrophones.

Although passive sonar is usually associatedwith submarines, many surface ships now have apassive system that utilizes their active sonartransducers. During the interval between soundpulse transmissions, the transducer acts as a

hydrophone, allowing the sonar operator tomonitor a broader frequency spectrum than

B SYNCHRONIZING THE SWEEP WITH THESUNNING SWITCH

71.121

Figure 6-8.Generation of spiral scan.

94

9 9

Chapter 6--PRINCIPLES OF SONAR

normally is possible. Passive reception does notinterfere with the reception of pulse echoes.During transmission, however, the passivefeature is interrupted.

Hyth-ophones

A hydrophone is a device used to listen forunderwater sounds. In operation it is similar to

SOUND SOURCE

SOUND SOURCE

SOUND SOuRCE

Figure 6-9.Operation of the BDI.

the transducer of active sonar equipment whenconverting sound energy to electrical energy.Two general types of hydrophones may beemployedelectrostrictive and magnetostrictive.Modern hydrophones are of the electrostrictivetype, consisting of ceramic elements thatoperate on the piezoelectric principle. When theelements are struck by a sound wave, thevibrations set up are converted to an electricalsignal, amplified, and displayed at the operatingconsole.

SINGL E- LINE HYDROPHONE.--Knowl-edge of the single-line type of hydrophone,although it is not in general us ..! today, willaid you in understanding how modernhydro phones operate.

A typical early type uses the mag-netostrictive effect for sound detection. Thehydrophone, which is trainable through 3600, isa line type whose nickel tubes are arrangedhorizontally in a line. It is divided electricallyinto right and left halves.

Weak signals from the hydrophone are fed toan audio amplifier, then to bandpass filters thatremove undesired frequencies from the detectedsound.

Accurate bearing is determined by trainingthe hydrophone back and forth across thedirection of thc sound source. Outputs of theright and left halves of the hydrophone are fedto a bearing deviation indicator (BDI). Anyphase difference between the right and leftsignals causes the meter to deflect.

Operation of the BIN is diagramed in figure6-9. In part A of the illustration, thehydrophone is on target. Signals in both halves(right and left) produce a phase difference equalto zero. No deflection is indicated by the meterneedle. In part B, the hydrophone is trained offthe target to the right, and the meter needle isdeflected in the "train left" direction. Thebearing deviation indication (BDI) of the meterinforms the operator that he must train (pushthe needle to the left) left to obtain a phasedifference of zero. The hydrophonc in part C is

71.54 trained to a position left of the target. A righttrain is necessary to obtain the desired bearing.

100 95


The majority of passive sonar systems areequipped with the automatic target follower(ATF) feature. With the ATI' feature, right andleft sipals are fed back into the training system,causing the hydrophone to follow the targetautomatically.

HYDROPHONE ARRAY.Modern passivesonars utilize a hydrophone array, which isinstalled in many configurations. The conformalarray is curved around the submarine's hull, withan open end aft. The circular array consists of anumber of hydrophones arranged vertically in acircle and mounted in or under the submarine'sbow. The line array consists of severalhydrophones mounted along the horizontal axisof the submarine. Some of the newer passivesonars utilize a spherical array and in somc casesa towed array. For more information on arrays,refer to Sonar Technician S 3 & 2, NAVEDTRA10132, current series.

MODERN PASSIVESONAR THEORY

The theory of modern passive sonar consistsof two basic steps: reception and presentation.Figure 6-10 is a simplified block diagram of anarray type of pasive sonar. The array cannot betrained physicai!y. Instead, a compensatorswitch is added that, in effect, trains the systemelectronically.

Reception

Signals received ki an array type of passivesonar system are coswerted to electrical energy

LAG

LINES

AUDIO

M PIND

71.55Figure 6-10.Block diagram of an array-type passive

sonar.0 1

96

and then are fed to a preamplifier to beamplified to a usable level. There is onepreamplifier for each hydrophone in the array.The output frOnl each preamplifier is connectedto a slipring in the compensator switch. Theslipring cmiples the preamplifier output to arotor plate.

One side or the rotor plate consists of anequal number of brushes and sliprings, eachbrush riding on a slipring. On the other side ofthe rotor plate, a set of brushes is arranged in ascale inodel of the hydrophone array. Theselatter brushes couple the rotor plate output tothe stator plate. The stator plate has two sets ofbars inlaid on the plate, one set on each half ofthe plate. Brushes on the rotor facing the statorplate make contact with the bars as the rotor istrained, and the signals present on the brushesare picked off by the bars. Half of the brusheson the rotor plate arc always in contact with thestator plate, thereby utilizing half of the array atany given time. The center of the stator plate,being the reference point, makes it possible todetermine the exact bearing of' the target.

The arrangement of the hydrophones causesthe signals to be out of phase with each other atthe output of the preamplifiers. For the signalsto be usable, they must be placed in phase witheach other; hence, it is necessary to delay thesignal. Each bar in the stator plate is connectedto lag lines. The purpose of lag lines is to delaythe first received signals a proportional amountuntil the last received signals can catch up.

Once the signals arc in phase with eachother, they are additive. As a result we have astrong signal to feed to the audio amplifier.There the signal is amplified and then is fed toan indicator.

Presentation

The console illustrated in figure 6-11 isrepresertative of the indicators used with sometypes of array sonars. Target indications arepresented continuously on a paper recorder anda CRT. They also arc given audibly. The CRT isnot located on the console itself, but is a part ofa separate unitan azimuth indicator (fig. 6-12).

Chapter- PRINCIPI 1.S ()I S()NAl;

35.9Figure 6-11.Console of an array-type passive

sonar.

The paper recorder (on the upper portion ofthe console) plots the bearing of all noise.Operating in synchronization with the paperrecorder is the CRT. It indicates the location ofall noise-produeing targets by inward deflectionsof the circular sweep. An audio channel.provided with each azimuth indicator, permitslistening (with the aid of an external speaker) tothis continuously scanning beam.

97

1 (I

DIVLAySELECTOR

35.10Figure 6-12.Azimuth indicator of an array-type

passive sonar.

More detailed information on passive SO11,11.

systems is contained in Sonar n'chnician2. NAVEDTRA 10132. Also consult themanufacturer's technical manual supplied witheach equipment.

VARIABLE DEPTH SONAR (VDS)

As you recall from chapter 3 of this manual,oceanographic conditions frequently are suchthat there arc layers of water with widelyvarying temperatures. Where these layers meet(layer depth). much of a transmitted soundbeam is either reflected or sharply bent(refracted). Submarines operating beneath thelayer depth may escape detection because thesound does not reach them or because thereturning echo is greatly weakened or mushy.The VDS overcomes this disadvantage because itcan be lowered beneath the layer depth, thusimproving detection capabilities previouslylimited by the fixed, hull-mounted sonar.

Older VDS sets consist of a towedtransducer operating in conjunction with ashipboard-installed, hull-mounted sonar set. Theunion is accomplished by providing a transducerwithin a hydrodynamic towed vehicle, plus acrane-type hoist for lowering. towing, andraising the vehicle (fig. 6-13). The towed

"'RODI I( H( )N SON A R

transducer is connected electrically to the shipthrough a cable e\ midnig. through the center oithe tow cable. A switching inechainsin in thesonar set permits rise of either the hull-mountedtransducer or the towed-transducer, or bothsimultaneously.

A later type or VDS (not shown) is a s,)11:11.set complete within itself. Because it call hemade to operate independently of other sonarsystems, it is known ;Is the independent variabledepth sonar (IVDS).

DIPPING SONAR

Sonar equipment called dipping sonar canbe used by rotary-wing aircraft (helicopters) todetect submerged submarines. Because it isn'tpractical to drag sonar equipment through thewater at the minimum Hying speeds offixed-wing aircraft, only aircrn.t that can hoveror move Lit low speeds are suited for sonardetection.

liecallt. of the limited weight-cnrying andpower-producing characteristics of aircraft,Ingh-powered a/imutli-type sonar is not carriedby aircraft. The equipment is of the"searchlight type which pings on one bearing ata time, must he trained to the required bearingto detect a target, and presents only an audibleecho without video presentation. In spite ofthese limitations, airborne sonar gear is capableof excellent results because it can be transportedfrom one location to another at a much higherspeed than that of any surface vessel andbecause, although such aircraft as helicopters arenoisy, they produce little water-conductednoise. (Most dipping sonar presently used inhelicopters is capable of scanning 3600 and alsoof narrowMg the search to a selected bearing.)

In a helicopter, the dip or dunking sonarequipment, except for a hall-shaped transducerhousing tire 500-foot cable from which it issuspended, is located in the helicopter fuselage.When the helicopter has reached a locationwhere the presence of a submarine is suspected,

1 0 3Figure 6-13.VDS towed vehicle ready for lowering.

98

51.63

napier o ll'Llti ()I )NAR

it descends to It) to 21) tcel above the water, .indthe sonar hall is koAcred to ;ihout 401) feetbelow the surface. After searching, thehelicopter hauls In the cable. After the eahle hasbeen retracted, the helicopter can go to ;motherlocation. When the submarine is detected annlocated, the hehcoptcr can "vector in" otheraircraft and ASW vessels for the attack or canitself attack it' properly armed.

l'he search procedure can he completed in afew minutes (especially if the search doesn'tencompass the full 360 in azimuth), and thehelicopter can be up and away. Present types ofsubmarines have no effective countermeasuresagainst helicopters. This search technique ismuch more difficult in heavy weather althoughimprovements in thk respect are being made

continually. 1:01rt: hd 4 shows a hc11,:(Ipier withsimar cuhmerg.ed. sealchim).

SON0131.1ON'S

Radio so;lobiloys are small expendahlehydropII,)ne units ,VhOse olllput is

radio-broadcast by a slltall Irulsmit ler in thesonohuoy. They zlle generally dropped to the seasurface hy fixed-wing ;nrcrat't in thk ;trea whereenemy submarines are expected to be. Usuallymore than one is dropped at a tillte, in a L'IrCuldrpattern around the contact area (as (ieterminedby other detection data). An experiencedoperator, hy com)aring its pitch (for (ioppler) asreceived by each sonohuoy, can estimate thepresent location and direction of movement ofthe target. After two to lour hours, a solubleplug in the sonobuoy dissolves and allows the

HF1NAV Y "7:

--- ...r.,?, . ...----f.7-_-;:--....-7f-t-:.,1----.-:

'-'' -----7.- ':" 7 7j St ... '' 14 #: .2 : .. . 4 .. 2 ' ... 4: , . ; . .I. 2:....... . .:0.,'Jr7,41.M. ' .."..*4 ..... ... -..,/....t., .." ..,..,,,E. ye, ...

7 :.....:.;r7: 7" '

;74,a

g *Irt

Figure 6-14.Dip sonar in use by helicopter.

99

104

3.115


LAY TWO BUOYS AT rHEAPPARENT ORIGIN AND ATHIRD IN THE PROBABLE

SLICK DIRECTION OF SUBMARINEMOVEMENT

110.106Figure 6-15.Radio sonobuoys used to locatc submerged

submarines.

unit to sink. While afloat, the sonobuoyindicates its position visually (by releasing reddye into the water or by keeping a lamp lit) andby radar.

Figure 6-15 shows diagrammatically howone type of sonobuoy pattern is initiated by anaircraft in response to surface indication of thepresence of a submerged submarine (in this case,the oil slick from a subma7ine that has beendamaged). The buoys are planted where theywin continue to pick up the submarine's soundas it proceeds underwater. A frequent pattern isa circle of buoys about the area (called thedatum) in which the submarine contact isexpected.

DEPTH SOUNDER(FATHOMETER)

The use of sound is a common method ofmeasuring .water depth. A sound pulse, directedtoward the bottom, is transmitted, and its echeis received. The time between pulse transmissionand echo reception is measured and, based on

the speed of sound in water, the depth isthereby determined. Such an echo soundingdevice is known as a sonar sounding set called afat hometer or a depth sounder. Basically thefathometer is a navigational instrument: but,because it operates on the sonar principle, itusually is given to the Sonar Technician forupkeep.

One type depth sounder used aboard shipsand. submarines is the AN/UQN-1 sonarsounding set, shown in figure 6- I 6. Severalmodels of the set are in use.

The AN/UQN-1 depth sounder employs thehot stylus and sensitized paper method ofrecording depths. It also has a visual scopepresentation for shallow depths. This depthsounder is a compact unit, capable of giving

RECEIVER -TRANSMITTER

TRANSDUCER

Figure 6-16.Depth sounding equipment.

100

1 6 5

62.9

Chapter 6 1S OF St)N,AR

- 560

lop°

1500

TRANSMITTED PULSE TRACESrc\O

15.1

260 200a tit 200

250

300

450

500

vl

TRACES MADE ON2*0 6000 FATHOM "

SCALE3000

3500

4000

-100

5600

6000

300

350

400 \ ,tcoo .lioTRACES MADE ON TRACES MADE ON

450 600 FATHOM ,-1.), 600 FOOT

I

SCALE SCALE r!:000 /

i

1 i",tOr

I

t,(*i

-51:0

Figure 6-17.Depth recording showing a steady decrease in depth.

accurate readings at a wide range ofdepthsfroni about 5 feet to 6000 fathoms.Three recorder ranges are provided on theAN/LIQN-1. They are 0 to 600 feet. 0 to 600fathorns. and 0 to 6000 fathoms. The CRTranges are 0 to 100 feet and 0 to 100 fathoms.The equipment may be keyed manually orautomatically. (NOTE: All depths are measuredfrom the ship's keel, not the water's surface.)

Two styluses are used, hut they are spacedso that only ono stylus records at a time. Whenthe depth sounder records, a stylus starts downthe recorder chart simultaneously with thetransmission pulse. The stylus moves at aconstant velocity and marks the papertwiceonce at the top of the chart, when thepulse is transmitted. and again on the depthindication when the echo returns. A depthrecording made by a depth sounder of thk t pcis seen in figure 6-17.

6 101

62.10

The recording illustrjted waS 111,1L rrolll aship sa hng over a sk2:1 with steadily decreasingdepth. The first part of the trace was recordedon the 6000-fathom scale. Inasmut.h :is thepaper mov..s from right to lett. you can see inthe section of the pryer shown that the depthdecreased from 4000 to 600 fathoms. ( Eaterdepth information is to the right o) the paper.)When rdepth was about 600 fat'Jams, the scalewas shifted to the 600-fathom setting. (See howshifitrig makes use again of the entire width orthe paper.) Because depth decreased still further.the scale was shifted to the 600-foot settingwhen a depth of about 100 rathows W srecorded.

The marking on the paper is downward(stylus !notion is downwa.t1) in alternate rowsprinted from 0 to 600 and 0 to 6000. Ntarkingthe chart paper in this mariner rillows the Salliepaper to he used for all recorder set(ings. You

IN1101)1V1.1(1N in

HMS( 111101 ,,C;1 le the equipment is111:1he 11hctlicr the marking

is in thousands ot fathoms, hundreds otfathoms, or hundieds of feet.

BC sk.*:11(' ii Ike K ,,reatcr (Linthe water depth. Otherwke, a false depthindication (Or no indication will result,depending on the position of the styluses at thetnne of echo return, If water depth actually is120 feet, for instance, imd you have selected the100-foot range scale, a depth of 20 feet will heindicated.

Other fake indications are multiple echoesand reverherations, both of which usually arecaused by too high a gain setting. Multipleechoes are the result of the transmitted pulsebeing reflected back and forth several timesbetween the hot tont and the ship's keel. Inshallow water a solid line may he recorded,making it impossible to read the depth. Bothmultiple echoes and reverberation effects can hereduced by decreasing the gain.

Visual im.hcation is supplied by a circularsweep on the face of a Transmitted pulseand returning echo mark the sweep traceradially. The visual indicator, pointing to adepth of 82 feet or fathoms (depending on thescale setting f is shown in figure 6-18.

Operational Procedure

Following is a brief discussion on normaloperation. security operation. and shutdownprocedures, Refer to figure 6-19 while readingthis description.

NORMAL OPERATION. -Eor simplicity, itmay be assumed that there is only one normalway of operating the depth sounder, Deviationsmay be considered as expedients for conservingelectrical energy, time, or paper, or formaintaining sonar security.

I. Move power switch to STANDBY. waitabout 30 seconds, then ihrow the switch to ON.This proc,..dure prolongs the life of the keyertube by allowing the filament to heat heforeapplying plate voltage.

0 7102

0

:

.-s`N

limmuiLLli'/hi

71.57Figure 6-18.--Visual depth indicator.

2. On the range switch, select the properrange scale. On the indicator the scale is either100 feet or 100 fathoms. On the recorder thescale is 600 feet. 600 fathoms, or 6000 fathoms.

3. Set the ping switch to AUTOMATIC.4. Turn the gain control clockwise until a

suitable echo mark is obtained.

5. Observe that both styluses attached tothe revolving hell mark the paper from the zeroline to 5 feet.

6. Check to see that the proper rangemarking is indicated on the top of the paper.

7. Dep:-ess marker hutton. Observe that astraight line is drawn down the full length of thepaper. This line should be straight from top tobottom. otherwise the stylus is out ofmhustment.

SECURITY OPERATION.-- If it is notdesired . to place linked energy in the waterperiodically, the depth sounder may be operatedIS lor normal operation, except that the ping

switch is triggered down \\lard to SINGLE PING.then is released. The circuitry is arranged to

(li,uptt' H 12k1NC11211S 01 St

pulse the first link' the ke iw, contaA: Operate I Ill pwation ftentei I. 1 his ;Rtion I kconnockafter trirgerinr and then to release ininickh,ikl. both ,,ikIes t)I Ihe 1 I -)-\HI, h0 Il. \ripply tromThe ping switch way he held down as long, a, the c,unpinent (e \cep) thc ,,cl% lc,. mullet I.

desired without damage. The result is e\actlsthe same as ii thk switch w'erc in the Rtmtine MaintenanceAUTOMATIC position.

SHUTDOWN. Put the pinr switch in the()IT position. Throw the power switHi to the

7. H',' 1 i) ON AruD VvAl 1 30 '..:,F,CYNOS,Ok 7,100W ro SI'ANDHY IF IN': rAN.TANEOJE.OPFRATLN MAY RE RK::WIRED IMMINENTL`T'

SELECT INDICATOR OR RECORDER ANDPROPER DEPTH RANGE

Pontine iimintLmank:e use1 lick' applies toknictions. hesides opciation. that should heperrorined h the operator, \VIftn the operator

:70 :.,ELECi Ail 1-,)%1A TIC OH SINGLEPV.:G

ADJUS I GAIN CONT ROL TO GETA GOOD ECHO

.." "-

1Q FArHONIS FATriv,e,:-P

POWER i00 5000 HEADPHONE NiAPI. FRFEET / FATHC.:

ON \\14[JF:imAFIC

(*1 °C1 l'ING K11) i OFF, ,......."

STANDf3vri

S.NGLE PING:NOE

ILLUMINATION GAIN

S0 2 .151 4,-, 150, 2 IS 5 n ,0 ) Di. c voc vac .nt

ci

5 6

ADJUST ILLUMINATIONCONTROL TO SUITSURROUNDINGS

USE TO MARK VERTICAL LINE ONRECORDER CHART FOR TIMEIDENTIFICATION

Figure 6-19.--Depth sounder control panel.

71.58


checks out depth sounder equipment before arun, he should be prepared (if necessary) tomake minor adjustments and replace lamps,tubes, styluses, or paper. Moreover, he should besatisfied that the equipment will rendercontinuous satisfactory performance during theanticipated operating interval.

The manufacturer's technical manual thataccompanies the particular depth sounderaboard your ship lists a step-by-step procedurefor accomplishing minor adjustments, replacingparts, and satisfying preventive maintenancerequirements.

TAPE RECORDER

Sonar Technicians, particularly aboardsubmarines, must be able to make rec. -rdings ofsonar echoes and of other sounds detected bythe transducer or hydrophone. Such recordingsare valuable aids in classifying sounds (determin-ing the nature and/or source). All ships andsubmarines are supplied with the necessaryequipment to make such recordings. The mostcommon inst al lation is the AN/UNQ-7recorder-reproducer sound set, familiarly knownas a tape recorder.

The AN/UNQ-7 tape recorder is moresophisticated than many commercial types. It isa two-track recorder and reproducer, and isresponsive to all frequencies in the audiblerange. Both tracks may be recorded eithersimultaneously or independently. Normally,track B is used to record signals directly fromthe sonar equipment. Track A is used forrecording voice information.

When a recording reproduced by theequipment is played back, both tracks can beheard, or only one track, each channel having itsown volume control. In short, the AN/UNQ-7acts as a combination of two separate recordersthat are capable of being coupled to allowsuperimposing two audio information channelsupon each other. Figure 6-20 shows the frontpanel of the recorder. Later models, namely the-7B, -7C, -7D, and -7E are transistorized andhave a somewhat different appearance, but their3perating characteristics are the same as the)asic model.

Originally the AN/UNQ-7 had recordingspeeds of 3-3/4 and 7-1/2 inches per second(ips). Field changes permitted an additionalspeed of 15 ips. All subsequent models,beginning with the AN/UNQ-7A, have the 15 ipsfeature built in. In general, the faster therecording speed, the more faithful is the soundreproduction.

The standard reel is 7 inches in diameter,holding 1200 feet of 1/4-inch tape. At arecording speed of 15 ips, 1200 feet of tape willlast about 15 minutes.

Operating Principles

Magnetic tape consists of finely groundiron-oxide particles deposited upon a plasticbacking (tape). The particles, too small to beseen with the naked eye, are deposited in such away that they are allowed to mapetically moveor line up in an orderly fashion as a result ofsome force applied to them. The force having

109

104

Figure 6-20.--Tape recorder AN/UNQ-7.7.54

Chapter 6PRINCIPLES OF SONAR

such an effect on the iron-oxide particles is amagnetic field. This magnetic field can be causedby a common magnet or by a temporaryelectromagnetic field. It results from passingan electrical current through a coil of wire.

Magnetic Heads

A microphone contains a magnetic devicethat is capable of producing electrical energyrepresentative of the sounds spoken into it. In at a pe recorder, the microphone-producedelectrical pattern is fed to a wire coil, causing amagnetic field which represents the pattern. Thecoil is wound on a core that has a gap in oneside. Because the magnetic field is most intenseat the gap, that is where the signal is placed onthe tape. The narrower the gap and the sharperthe gap edees, the better is the high-frequencyresponse. Figure 6-21 shows a typical maenetichead. The magnetic tape passes over the head,and the electrical pattern is reproduced upon thetape in the form of regular patterns ofiron-oxide particles that magnetically line up inaccordance with the signal passed through thecoil.

GAP

Figure 6-21.Typical magnetic head.

The recorder has three heads. The device inthe recorder about which the magnetic field isproduced by the microphone is called therecording head. Another head, called the erasehead, eliminates the magnetic pattern from theparticles on the tape. A third head is forplayback of the recorded signal and is called thereproduction head. The three heads arecontained in a single housing.

RECORDING HEAD.The recording headis composed of a highly permeable material,which means that the core is easily magnetizedand just as easily demagnetized, by a currentpassing through the coil. High permeability is anecessity for the magnetic field to follow thefluctuations of the signal to be impressed on thetape.

In reality, the signal cannot be put "as is"directly onto the tape. It must be mixed withanother signal for strength and linearity; that is,for consistent form throughout the signal band.The bias signal with which the original signal ismixed is of very high frequencytoo high to beheard. Electrically, it has unchanging,steady-strength characteristics. The a.c. biasassures better acceptance by the tape of thesignal to be recorded and helps reduce distortionof strong signals.

ERASE HEAD.Tape passes from the erasehead to the recording head, and then to thereproduction head (in that order). The erasehead demaanetizes both channelssimultaneously. It is unnecessary to erase a tapeindividually before it is re-recorded because,when a tape is being used for recording, theerase head is energized so that a new recordingcannot be ruined by superimposing it over anolder one. Thus, tapes having recordings that nolonger are needed t'or retention can be useddirectly. The machine simply is set to record;the old tape is put on; and, after it passes theerase head, it is "cleaned" of the earlierrecording. It next passes the recording head,which puts a new magnetic pattern on it.

REPRODUCTION HEAD.Thereproduction head, which is next in line, is

71.122 similar to the recording head in construction.That is, it has a broken ring of permeable

105

INTRODIJCTION TO SONAR

material wound with wire coils. When therecorded tape passes over the gap, the permeablematerial is affected by changes in the tape'smagnetic field, and an electric current is inducedin the coils surrounding the ring. The inducedsignal is amplified and fed to phone jacks foraudible presentation.

Operating the Equipment

The top half' of the tape recorder, as seen infigure 6-20. is the . actual recorder andreproducer. The lower portion is the amplifiersection. It includes controls and indicators thatdirectly affect the recording and playback of thetapes.

Each recording track has a separate channel.On the equipment they are labeled channels Aand B. Channel A is used for voice recording andreproduction; channel B, for sonar information.Both channels have separate controls forrecording and reproduction. The recording:ontrols are to the left of the amplifier section.Playback controls are at the right of' theimplifier section.

THREADING TAPE.The roll of magnetic'ape to be used for recording purposes is placed)n the left reel-hold assembly on the upperection of the recorder. It is placed in such avay that, when the equipment is in operationrecording or reproducing), the reel rotates in a'ounterclockwise direction, and the magneticape leaves the reel from the bottom.

Other parts are on the upper section to guidehe tape and to pull it through the head device./hen the tape unwinds from the left reel, it is[-treaded around the guiding assemblies, fed'irough the head assembly, around the capstanmhich actually pulls the tape through), andien it is taken up by the ridit reel. A pictorialiagram of the path followed by the tape from!el to reel is printed on the face of the head;sembly. By adhering to the diagram. you willwe no difficulty threading the equipmentroperly.

RECORDINGAfter the tape is threaded,le tape recorder is energized by turning themer switch to the ON position. You must wait

a short warmup period.

106

Next, select the speed at which recording isdesired. As mentioned earlier, there is a choiceof 3-3/4, 7-1/2, or 15 inches per second. Selectthe faster speed for critical recordings duringwhich the pitch of the echo may have animportant part in later evaluation. A recordingmade at a higher speed can be studied morecompletely by reproducing it at the lower speed.(An 800-Hz tone, recorded at 7-1/2 inches persecond, is heard at 400 Hz when reproduced at3-3/4 inches per second.) Hence, recordings thatmay require later analysis should be made at thehigher speed. The disadvantage of the higherrecording speed is that the tape is used twice asfast as when operating at the next slower speed.Information on speeds to use for recording andplayback are contained in the technical manualsupplied with each recorder.

Although the higher speed provides thehighest quality reproduction. differences inrecordings made at each speed are not detectedeasily. Only when a critical analysis of therecording is made does the faster speed prove itsworth over the slower one.

The recording level is selected next, and eachchannel's level must be adjusted individually. Anindicator on the amplifier assembly is labeledRECORD LEVEL INDICAT3R. Directly belowit is a two-position toggle switch labeledCHANNEL SELECTOR. The positions of theswitch are marked A and B, each representing achannel. Set.the toggle switch to either channel,and observe the vertical amplitude on the face ofthe indicator. The record level controls, belowthe CHANNEL SELECTOR switch, are markedfor channels A and B. Adjust the level controlfor the channel chosen until the signal peaks(shown in the level indicator) occupy the spacebetween the upper and lower horizontal lines.Next, select the other position on the switch andmake the same adjustments for the otherchannel. The equipment is now ready to recordon both channels.

To start the recording process, an unlabeledbutton to the right of the record level indicatoris held to the left, and the tape recorder control(record section) is moved up to the No. 1

position. A ligbt (indicator No. 1) glows as theequipment begins to record.

11 1

Chapter 6PRINCIPLES OF SONAR

The unlabeled button is called the recordsafety interlock switch. Its function is to preventaccidental or inadvertent recording. To record,you must place the record switch in the No. I

position and simultaneously turn the recordsafety interlock switch to the left.

To stop recording, set the record switch tothe neutral (middle) position. To start recordingagain, move the safety interlock once more tothe left as the record switch is returned to theNo. I position.

Another position of the record switch islabeled AUX (for auxiliary). This position isprovided for use if an auxiliaryrecorder-reproducer is added to the system.

RECORDING FROM REMOTELOCATION.A device that allows somecontrol of the assembly from remote locations isincluded with the tape recorder. singleoperating control and two indicating lamps(labeled STANDBY and RECORD) are on theremote control unit. The single operatingcontrol is a two-position to,mle switch thatparallels the recnrd switch on the amplifiersection. Prelimin. :Itstments, such as tapethreading and levt: -,trol, must be set beforeusing the remote control unit. The standby lightindicates that power has been applied and thattape is threaded. It does not signify selection ofthe proper speed nor adjustment of the levelcontrols. It does not light when no power isapplied, when the tape is threaded improperly,nor when the equipment is used to reproduce apreviously recorded tape.

The positions of the toggle switch areSTANDBY and RECORD. The standby positioncorresponds to the neutral position of the recordswitch on the recorder proper. The recordposition takes precedence at both locations,meaning that, if RECORD is selected on theremote control unit, the equipment will recordeven though the record switch on the equipmentproper is in neutral. If RECORD is selected onthe instrument proper but STANDBY is set onthe remote control unit, the equipment willrecord again. Thus, a tape being reproduced onthe recorder proper can be ruined (by the

automatic erasure process during recording) ifthe switch at the remote control unit is set tothe record position during playback.Consequently, the switch on the remote controlunit must never be moved from the standbyposition unless the standby light is glowing.

When the machine is recording, theRECORD light on the remote control unitglows. When approximately 5 minutes ofrecording time, at 71/2 ips, remains on the tape,the RECORD lamp flashes to warn that the endof the reel is approaching. If the recorder cutsout (this feature is automatic when the tape reelis exhausted), the RECORD light goes out. Whenthe tape recorder returns to a standby condition,the STANDBY light glows again.

REPRODUCING.To play a recording,-thread the tape, turn on the power switch, allowfor warmup, and chose the tape speed.

Next. place the REPRODUCE switch in theNo. I position (it has the same positions as theRECORD switch). This setting actuates tapemotion, and both channels are reproducedsimultaneously.

Finally, adjust the reproduce level controlsfor both channels to the desired output of eachof the headphones (if used) or the loudspeaker.

To stop the playback, simply return thereproduce switch to the neutral (middle)position. This stoppage may occur at willthroughout the run of the reel. The equipmentreturns to the standby condition whenever theneutral position is selected. As in the recordingmode, the tape motion stops automaticallywhen the end of the reel is reached.

Remember that the switch on the remotecontrol unit must not be set to record during therepioduction mode of operation. Otherwise, therecording will be ruined.

Other Uses

The tape recorder allows simultaneousrecording and reproducing of sounds. By this


means, you can monitor what is being recordedas it is recorded. Steps to set the equipment tothis mode of operation are included in theequipment iniruction book, Technical Manual,Recorder-Reproducer Set, Sound, AN/UNQ-7,NAVSHIPS 365-2471.

A switch on the upper section of theinstniment allows rapid rewind and fast forwardoperation. Instructions and procedures for usingthe switch, as well as those for erasing andsplicing the tape, are also included in theinstruction book.

11 3

108

CHAPTER 7

BASIC FIRE CONTROL

Although the overall objective of all SonarTechnicians is to aid in destroying enemysubmarines, the manner in which the task isaccomplished varies with the individual branchof the rating. The shipboard Sonar Technician,for example, tries to maintain continuouscontact and aggressively enters thesubmarine/ship duel, using every available meansto hold contact. The submariner has a tendencyto sneak up on the target, gathering attackinformation from the noises produced by thetarget itself, perhaps making one sonartransmission just before firing. In each instance,the ultimate goal of the antisubmarine unit isdestruction of the enemy submarine. The systemby which information is collected and translatedinto weapon firing data (including positioning ofweapon launchers) is called fire control.

UNDERWATER FIRE CONTROL

Fire control is defined as the technique bywhich weapons are directed to a selected target.It consists of the material, personnel, methods,communications, and organization necessary todestroy the enemy. Underwater fire controlincludes all of the foregoing components, withthe added difficulty that the selected target is asubmarine, capable of moving in threedimensionsin range, bearing, and depth.

REPRESENTATIVE UNDERWATERFIRE CONTROL SYSTEM

Because many operational aspects of specificfire control systems are classified, this sectiondescribes in general terms the functions of whatmay be considered a representative underwater

FCS. The discussion following does not applyspecifically to all FCSs on all ships: the aim is todescribe the main elements of most systems sothat you will understand their functions andhow they work together.

The basic fire control attack problemconsists of analyzing target motion from sensorinputs, determining future target position,selecting the optimum weapon, and generatinglaunching orders to deliver the weapon anddestroy the target. Weapon selection isdetermined from target data and the computedtire control solution. Various units of the FCSare: ) a position indicator to allow forcommand control of weapon selection andtiring, (2) a stabilization computer to stabilizelauncher and sonar during the attack problem,(3) one or more position indicators to allowtesting, setting and monitoring of a selectedweapon and to act as a compatibility linkbetween gun fire control radar and the attackconsole, and (4) the attack console, the centraldata processing center of the FCS.

Attack Console

The attack console is a computer in the dataprocessing center of the FCS. In addition toreceiving target data from sonar, it may be ableto act on target bearing and range from missileor gun FC radars.

The console receives information such as (1)own ship's course and speed, and (2) targetrange, relative bearing, depth, course, and speed.There may be other inputs, depending upon thetype of weapon to be launched; most inputs aregenerated electronically, while others may beinserted manually. The console displays the


attack problem on the console geographicplotter section, combining tamt data withballistic's and own ship's motion to provide(depending on the weapon to be employed)--

G:erated data for sonar tracking andposition keeping.

?. Launcher train and elevation orders.

3. Missile or torpedo set-in orders.

4. Range and bearing for torpedo attacks.5. Director designation for in-flight

tracking.

From received target motion quantities, theconsole computes aided sonar bearing, and rangetracking information and sends it to sonar. Ifsonar loses contact, the operator places theconsole in the position-keeping mode, andattack problem computations continue from thelast observed t- t range, bearing, course, andspeed values y entered into the computer.

Depending on what the inputs to thecomputer are and the weapon(s) to becontrolled, the console solves the attackproblem and transmits to the weapon the firingsignal and the stabilized weapon train angle. ltalso transmits to the bridge the course to steerfor the attack. (More precisely, it puts outcorrections to own ship's course.)

Stabilization Computer

The stabilization computer receives roll andpitch data from the ship's gyrocompass, targetbearing from sonar, and apparent depressionangle from the attack console. From thesequantities the computer generates stabilizedsonar train and depression orders and transmitsthem to sonar. Input and output stabilizationdata are displayed on dial indicators on the frontpanel of the computer.

Position Indicator

A position indicator on the bridge providescommand with an indication of the source of'contact (sonar or radar); a continuous display ofown ship, target, and weapon tactical

information; an indication of firing readiness;and for some weapons a control by which thecommanding officer approves the payloadselection. For the last, unless command activatesthe "approved" control, the attack consolecannot generate a firing command.

Relay Transmitters

In general, relay transmitters receive inputdata at a particular Irequency, then convert it toa different frequency (operating voltage) fortransmission to other equipments. There aremany types of relay transmitters, depending onthe purpose for which utilized. This briefdiscussion, of course, is concerned only withFCS relay transmitters.

One type of relay transmitter tests,programs, and monitors the ignition andseparation assembly data of a selected missile.After the missile is selected, the transmitter teststhe power supply, thrust cutoff velocity timechannel, and airframe separation time channel toensure missile readiness for firing. missilecheck results are unsatisfactory, another missilemust be selected.

A second type makes the attack consolecompatible with gun or missile FCSs andweapon direction equipment. This transmitter isused during (I ) missile or target tracking and (2)missile designation. For the former, thetransmitter converts single-speed synchro targetor missile bearing data into two-speed synchrosignals for transmission to the attack console.When the transmitter is utilized for missiledesignation, water entry point quantities andairframe separation time are received by synchrotransmissions from the attack console.Designated missile elevation is set in manually atthe relay transmitter.

WEAPONS

Some of the antisubmarine (A/S) weaponscontrolled by underwater fire control equipmentand used by ships and submarines against enemysubmarines are described in the topics thatfollow. The discussion also points out some ofthe problems that must be overcome by the

Ho 115

Chapter 7BASIC FIRE CONTROL

underwater fire control system to realizesuccess. Since these weapons were presented inchapter 2 of this manual, the discussion is brief.Not all weapons are discussed because of thenature of their classification.

SURFACE A/S WEAPONS

Aboard ship, several kinds of antisubmarineweapons arc available. The principal one is theASROC utilizing torpedo or depth chargepayload. Also included are one of two types ofabove water torpedo tubesthe Mk 32 triplemount (see fig. 7-1), or the Mk 32superstructure-mounted doub!f: moant (see fig.7-2).

Homing torpedoes are of two typesactiveand passive. The active type transmits soundpulses and homes on the echoes reflected fromthe target. The passive type is guided to thetarget by noise emanating from the target itself.

Early antisubmarine torpedoes had two;erious drawbacks. First, the endurance or activeJeriod was relatively shorta matter of minutes.'Second, their speed capability, compared with

speeds of many modern submarines, was slow,and they could be outrun by submarines. Thesedrawbacks have been eliminated for the mostpart in modern high-speed torpedoes. The newertorpedo also is quite maneuverable, in contrastto the submarine, and has a tighter turningcircle. Except for attempting to delude thetorpedo with a decoy-type device, one of thebest defenses the submarine skipper can provideagainst a modern antisubmarine torpedo is tocall for all available power in an effort to clearthe area at maximum speed. Even then, moderntorpedoes are normally faster than thesubmarine. But, inasmuch as the primarymission of an A/S escort vessel is to prevent thesubmarine from making an attack, causing thesubmarine to evade a torpedo and rur from thearea would accomplish the escort's mission.

When conducting an antisubmarine torpedoattack the ship must maneuver into a favorablelaunching position. A typical homing torpedoruns in helical patterns while seeking asubmarine. Once contact with the submarine isachieved, the torpedo steers toward the target. If-contact is lost, the torpedo searches for a shorttime in the general direction in which it isrunning, then resumes a helical search pattern if

Figure 7-1.Mk 32 torpedo tube.

retti.

3.129


contact is not regained. Some types have apassive capability in conjunction with theiractive feature which enables them to detect asubmarine that is beyond their active acousticrange.

The shipboard antisubmarine rocket, knownas ASROC, was discussed in chapter 2 of thismanual.

SUBMARINE A/S WEAPONS

Today's submarine has a choice of manytypes of torpedoes, each designed for a specificpurpose. The three main classes of torpedoes arestraight-running, acoustic-horning, andwire-guided.

Although the straight-running contacttorpedoes are useful in certain tacticalsituations, they are not considered effective asantisubmarine weapons. These torpedoes areused chiefly against surface targets at fairly shortranges. They are noisy and thus are detectedeasily, but they are difficult to counter becauseof their high speed.

Acoustic-homing torpedoes available tosubnwrines have features for homing passively oractively, and for combining the two.

Wire-guided torpedoes are a variation of theacoustic-horning torpedo. They are guided to thetarget submarine's vicinity by signals sent overthe wire by the launching submarine. After thetarget is acquired by the torpedo, it homes on

73.129

Figure 7-2.View of Mk 32 Mod 9 surface vessel torpedo.

112


the target without further guidance from thelaunching submarine.

The submarine also has a rocket-propelledweapon, containing a nuclear warhead calledSUBROC, which was described in chapter 2.

DETECTION-TO-DESTRUCTION PHASES

Theoretically, the fire control problembegins when a target is detected and ends withits destruction. In practice, though, the firecontrol problem starts well after initialdetection. It commences after the initialclassification and when target tracking isordered.

Like all other fire control systems(antiaircraft, surface-to-surface, and the like),the antisubmarine fire control system solves theproblem in the following stages: (1) tracking thetarget (2) analyzing target motion and (3)computing ballistic solution.

Detecting a submarine is no easy matter.Neither is it a simple task, once a submarinecontact is established, to carry out the successivephases mentioned here. Although fire controlsystems are capable of performing complicatedtasks, such as predicting future positions,submarine hunting is subject to errors caused byhuman judgment. Training in proper operationof the equipment for maximum ASWeffectiveness is a must for Sonar Technicians.

Because the same equipment often is used indetexting a submarine as in tracking it, detectionis considered as a phase even though, in thestrictest sense, it may not be a part of theproblem.

DETECTION PHASE

A submarine may be detected in severalways, the most positive being visual sighting. Ifthe submarine is seen to dive, classification isevident; there is no question about the positivenature of the contact.

Detection also can be made by radar. If aradar contact suddenly disappears, there is agood chance that the echo was the return from a

113

surfaced submarine and that the disappearancewas caused by diving. If sonar contact also isheld, it can be assumed the contact is asubmarine. Most surface-search radars canreceive a radar indication from a periscope.Hence, it ic possible to track a submarine that isoperating completely submerged except for itsperiscope. The radar method goes hand in handwith visual detection because radar frequentlyprovides the first indication, directing eyes tothe location of the periscope, snorkel, sail, orhull of the submarine.

The sonar equipment aboard your ship orsubmarine is designed to detect and track thesubmarine and feed computing devices withtactical data to achieve the destruction phase ofthe problem.

TRACKING PHASE

After detection, the contact must betracked. Aboard a submarine, a graphic displayof target bearings is made during this phase.From information furnished by this display,target motion is established. Normally, thesubmarine uses only passive sonar for trackingbecause active sonar may disclose the presenceand even the location of the tracker.

Shipboard Sonar Technicians track thetarget with both active and passive sonars,including LAMPS employing sonobuoys, anddepend lareely upon the strength and quality ofthe echo of the transmitted pulse for targetinformation. An t isubma rine ships have firecontrol systems that incorporate automatictracking features. Once the contact is establishedfirmly, the automatic devices keep the sonar onthe target and compute the course to be steeredso that the ship will arrive at the best firingposition for the weapons selected for use.

Basically, establishment of relative rates oftarget motion is all that is desired from thetracking phase of the problem. The trackingphase sets up the pattern for the nextphasetarget motion analysis. It is from therelative rates that actual target motion isdetermined.


TARGET MOTIONANALYSIS PHASE

The target motion analysis phase is adynamic problem because both the attackingunit and the target usually are in motioncontinuously, and n11 related factors changeconstantly. As a result of the target motionanalysis phase, we can establish the true motioncomponents of the target (course and speed).There are several ways of arriving at a course andspeed solution.

The target's true course and speed can beestablished on the NC-2 plotter maintained inCIC by Operations Specialists from informationsupplied by automatic inputs from sonar. TheNC-2 utilizes own ship's course and speed inputsto cause a lighted "bug" to follow own ship'smovements. Sonar target true bearing and rangeinput cause a different colored "bug" to moveto the indicated position. Target course andspeed are then determined by the NC-2 plotter.The NC-2 plot aids the CIC officer in conningthe ship. when CIC has ccntrol of the attack,and supplies search arcs to the sonar operatorswhenever contact is lost.

The target's true course and speed can alsobe established on the dead-reckoning tracer(DRT) plot maintained in CIC by OSs frominformation supplied by the sonar operatorsover sound-powered telephone circuits. TheDRT utilizes own ship's course and speed inputsto cause a lighted "bug" to follow own ship'smovements. Sonar target ranges and truebearings are plotted from the bug, thusestablishing the submarine's position. Courseand speed are then determined by the DRTplotter.

Target true course and speed also can beread from dials on the attack console.

On the surface ships the underwater firecontrol systems usually have to compute ahorizontal sonar range from the measured slantranee and estimated target depth information.This computation is necessary Y.ecause the firecontrol system solves for target course and speedin the horizontal plane on the surfact in whichthe ship operates. Slant range is transmitted tothe attack console from the sonar console.Depth is set manually into the fire controlsystem.

114

119

The attacking submarine may use differentmethods to determine true direction of targetmotion. One method is by direct observation,when mrsible, of the angles on the bow. Angleon the bow was discussed in chapter 5.

BALLISTIC SOLUTION PHASE

It is difficult to say when one phase ofsolving a fire control problem ends and anotherbegins. One phase usually overlaps another;often they are concurrent. The start of theballistic solution phase, for example, practicallycoincides with that of the tracking phase. Anantiaircraft fire control system presently in useprovides a solution in only 2 seconds once thetarget is acquired by radar. Yet, during thattime, the target is tracked, its motion is

analyzed, and the ballistic solution is computed.Most underwater fire control systems, however,take longer to develop a solution. The reason isthat certain inaccuracies in target informationare inherent in underwater sound. Additionally,range limitations of the weapons require theattacking unic to be within a specific distance tolaunch nontrainable weapons, and within aspecific area to fire its trainable weapons.

After determining the target's course, speed,and estimated depth, two items must beconsidered to complete the problem. One iswhether or not we need to close the target. Theother is when to fire.

If the target needs to be closed, keep inmind that you don't want to alert the submarineif at all possible. Also remember that the fartheryou stay away from an enemy submarine, theless chance he has to shoot at you.

The second considerationwhen to fireis adecision made by the commanding officer afterthe fire control computer has reached a solution.Many factors are included in the FCS solution.Due to the classification of many of thesefactors, they are not discussed in this manual.More detailed information may be found in STS3 & 2, NET 10132-C, and STG 3 & 2, NET10131-D.

DESTRUCTION PHASE

Destruction of the target is the ultimate goalof the submarine hunter. During this phase the


computed ballistic solution is used so that theordnance may effectively be fired on the target.Although the surface ship's primary A/S weaponis the homing torpedo, whether fired from atube or ASROC, the methods of submarinedestruction by surface ships are many andvaried. Included are ramming, hull-rupturing,near misses by torpedoes, complete destructionby atomic depth charge, or any action whichforces the submarine to the surface where it canbe sunk by surface gunfire. Submarines, ofcourse, use their A/S torpedoes on theirsubmarine targets. In short, the destructivephase includes action on the part of theattacking unit that leads to a killdirectly orindirectly.

FUNDAMENTAL PROBLEM

The fundamental problem of fire control isto deliver fire on the selected target. A direct hitis not required with some weapons. An atomicdepth charge, for example, can cause thedestruction of a submarine if the chargeexplodes close enough to it. All attacks are madewith the intention of hitting the target but, withsome weapons, a near-miss is good enough.

Solving the fundamental problem is no easymattir. The difficulty is due to such factors astainet speed, maneuvers, and range and speed ofth e. weapon, all of which play important roles indelivering fire on the selected target. Thesolution to the problem varies greatly with givensituations. A duck hunter, for example, "leads"the duck along the path of flight. If the hunteraimed directly at the duck as he fired, the shotwould pass through the area at which he aimed:but, because the duck is moving, it no longerwould be at that spot when the shot reachedthere. Consequently, the hunter makes anestimate of the future position of the duck, aimsfor that spot, and fires his gun. If he estimatescorrectly, both the shot and the duck will arrivesimultaneously at the predicted position. Thefire control problem is similar to the duckhunter's problem but on a much larger scale.

REFERENCE PLANES

Assume that a gun, rigidly fixed to a ship'sdeck, fires, while the deck is level, and its

1 1 5

71.123Figure 7-3.Reference planes.

projectile hits th,.! target. The same gun, if firedat a time other than when the deck is level, willmiss the target. If the gun is free to train (rotate)and elevate, however, compensation can bemacie for the ship's roll and pitch. The gun thenwill remain reasonably steady, thus improvingthe chances of hitting the target, regardless ofthe ship's motion. A fire control system, inconjunction with a stable element, attempts tomake the necessary adjustments to keep theweapon steady.

Deviations from the level attitude aremeasured by a gyromechanism (the stableelement), which transmits to a computer in thefire control system signals that indicate variationof the position of the deck with respect to thehorizontal.

Based on signals from the stable element, thefire control system computes values of train andelevation for the weapons launchers tocompensate for deviation from the levelattitude. The various attitudes are measuredwith reference to flat, two-dimensional surfacescalled planes. (See fig. 7-3.) An underwater firecontrol system computes solutions in thehorizontal, deck, and vertical planes.

Horizontal Plane

A horizontal plane is tangent to the surfaceof the Earth. Visualize this condition by laying a

1 2


playing card or an orange. The card representsthe horizontal plane: the orange symbolizes theEarth: and the point of contact between the twois the point of tanEtency. Every plane parallel tothe horizontal plane is likewise a horizontalplane.

Deck Plane

The deck plane represents the level of theship's gun mounts. (References to guns includesimilar weapons systems.) When the ship is level,the horizontal and deck planes coincide: but,when the ship rolls and pitches, the deck planedeviates from the horizontal. The stable elementmeasures the amount of angular deviation andtransmits the information to the fire controlsystem. The fire control computer compensatesfor deck tilt by computing a solution in thehorizontal plane, then makes train and elevationcorrections. In effect, the system brings the deckplane back to the horizontal.

Vertical Plane

A vertical plane is perpendicular to thehorizontal plane and is the reference from whichbearings are measured. Relative bearing, forexample, is measured in the horizontal planeclockwise from the vertical plane through ownship's centerliri to the vertical plane throughthe line of sight.

The system of planes makes possible thedesign and construction of mechanical andelectronic equipment to solve the fire controlproblem. These lines and planes are imalMlaryextensions of some characteristic of the ship ortarget.

FIRE CONTROL NOMENCLATURE

Fire control nomenclature provides a briefand accurate means of expressing quantities thatotherwise would require extended descriptions.Although all underwater fire control systems usebasically the same fire control symbols, eachsystem has a few symbols that are unique. Theentire nomenclature is too lengthy and detailedfor inclusion in this text, but a brief explanation

116

of the basic system is provided so that you maybetter understand the meaning and purpose ofthe fire control quantities and their symbols.

Ordnance pamphlet OP 1700 has establishedand standardized the nomenclature used indescribing fire control problems and theirsolutions for the control of guns, underwaterweapons, and missiles. Volume 1 contains thenomenclature for the quantities applicable tosolutions of the gun fire control problem.Volume 2 covers the nomenclature forunderwater related quantities. Volume 3 has thestandard nomenclature for missile relatedquantities.

The geometrical quantities used in naval firecontrol are those quantities involved in themathematical solution of the general fire controlproblem. Hence, the geometrical quantities fallinto certain main classes of quantities. Each ofthe main classes of quantities is represented by aclass name. In each class, other geometricalquantities, besides the basic quantity, areexpressed by applying modifiers to the basicquantity. The modifiers express the way inwhich the quantity is measured.

To illustrate, a class of quantities forexpressing present target position is lineardistance between own ship and the target. Thisclass of quantities is called ranges. The basicgeometrical quantity in this class is the lineardistance between own ship and the target,measured along the line of sight. It is expressedby the capital letter R. Another quantity in thisclass is the linear distance between own ship andthe target, measured in the deck plane. Thisquantity is symbolized by applying the modifierd (meaning measured in the deck plane) to thebasic range quantity R, forming quantity Rd.

The nomenclature assigned to represent thebasic geometrical quantity in each class and theletters and numerals used as modifiers are listed(as mentioned previously) in the three volumesof OP 1700. Extracts of Volume 2 of OP 1700(Underwater Fire Control Nomenclature) arecontained in Sonar Technician G 3 & 2.

SONAR POSITION QUANTITIES

When a target echo is received by a sonartransducer, the target actually is not at theposition indicated on the sonarscope but at

Chapter 7 BASIC FIRE CONTROL

some other location. This difference in targetpositions is due to curvature of the sound beamand to target movement durina echo returntime.

The determination of actual target positionrequires the application of corrections to thesonar measurements. These corrections. whiLliare computed in the underwater tire controlsystem, consist of two position quantities:apparent tamet position and past target position.(Target course and speed are basicali: producedby this information.) Sonar position quantitiesare illustrated in figure 7-4.

Two class quantities. range (R) and bearing(B), are shown, togeth,.1- with the modifiersnecessary to express the appropriatemeasurement. Quantities related to apparenttarget position are represented by the lowercaseletter a: those related to past target position usethe letter p. The modifier h rn,..sans themeasurement is in the horizontal plane: themodifier v refers to the vertical plane.

Apparent Target Position

Apparent target position is the point fromwhich the sonar echo appears to come. It differs

r'7

!Rya/SouND BEAM \ I

PRESENTTARGET

POSITION

TARGET TRAVEL DuRiNGTIME OF SOUND PuLSE

TRAVEL FROM

PASTTARGETPOSITION

APPARENTTARGETPosiTION

Figure 1-4 . Sonar position quantities.

1 17

i 2

TARGET TO SHIp

71.124


from present target position because ofrefraction of the sound beam and because oftarget travel during the time required for theecho to return to own ship. The dotted lines infigure 7-4 represent apparent positionmeasurements. The quantity Ba is apparenttarget relative bearing, and Rha is apparenttarget range measured in the horizontal plane.

Past Target Position

Past target position is the location of thetarget when struck by the sound beam. In otherwords, it is the position from which the sonarecho actually comes. Past target position differsfrom apparent target position because ofrefraction of the sound beam. It differs frompresent target position because of targetmovement during the time it takes the soundpulse to return to own ship.

Present Target Position

Present target position is where the targetactually is located when the sonar echo reachesown ship. It represents the distance traveled bythe target during the time it takes the soundpulse to return to own ship from the target. Asshown in figure 7-4, quantity B is the target'srelative bearing at the time the echo is received.

CAP

BUSHING

HOUSING

ELECTROMAGNET

BEARING RETAINING RING

\ SPRINGWASHER

SHIM WASHER

SHAFT

Figure 7-5.Magnetic brakeexploded view.

Target depth (Rvua) and slant range (Ra) arecombined to give horizontal range to past targetposition (Rhp). Ra is computed with otherquantities to give present target position (c(Ra)for use in the weapons system.

EQUIPMENT

An underwater fire control system usually isdesigned to operate with a particular weaponsystem although efforts are made to make thesystem compatible with future weapons. Onemodern fire control system may be used withseveral weapon types. Regardless of the system,it serves only one purpose: the destruction ofenemy submarines.

After target position is determined, the basicproblem for the system is to predict futuretarget position, calculate the required attackcourse and firing time, and transmit the data toweapons and control stations.

Because most underwater FCSs are of aclassified nature, they cannot be included in thistext. Certain concepts are discussed, however, togive you some basic knowledge of how a FCSoperates.

Electromechanical Devices

Electromechanical devices combine twod i fie re n t types of action electrical and

RETAINING RING

FRICTION PLATE ELECTROMAGNETASSEMBLY

ASSEMBLY

SPRINGWASHER

SHIMWASHER

BUSHING

---- HOUSING

sdo

S'HAFT

2 Magnetic clutchexploded view.1

71.60


mechanical. These devices, such as the magneticbrake and magnetic clutch, have wide usage andapplication in fire control computingcomponen ts.

The magnetic brake can stop and hold ashaft at a given value when certain conditionsare met. The magnetic brake is used to prevent aline of gearing from turning. When the current isoff, no magnetic action takes place. In figure7-5, (an exploded view of a magnetic brake),notice that the spring washer holds the cap awayfrom the electromagnet, thus allowing the shaftto turn freely. When the current is turned on,the electromagnet exerts a force great enough toovercome the effect of the spring washer andpulls the cap tight against the electromagnet,thereby locking the shaft in place.

An electromagnetic clutch is used to engageand disengage a line of gearing. An explodedview of a magnetic clutch is shown in figure 7-6.When current is fed to the electromagnet, thefriction plate assembly and cap assembly are incontact with each other, and the output linetransmits input rotation. When current to theelectromagnet is cut off, the friction plateassembly and cap assembly separate by springaction, losing contact with each other. Theoutput line does not rotate or transmit anyinput to the clutch when these components areseparated.

Electrical Resolver

Another device that should be consideredhere (although it is an electrical assemblynotelectromechanical) is the electrical resolver. Theresolver is a computing device and functionsmuch like a transformer. It is capable ofseparating an electrical input vector into two EXCITATION Eright angle components. The resolver has a statorand a rotor, each part consisting of two separatecoils wound at right angles to each other.Voltages induced on the stator coils byexcitation of the rotor coils depend upon thedisplacement of the rotor with respect to theelectrical zero reference axis of the resolver. Insolving for a single vector, only one of the statorcoils is connected electrically and represented on

a schematic. Figure 7-7 shows the schematicsymbol of an electrical resolver.

When the resolver is zeroed electrically, therotor coil clamped to the stator coil is called thecosine coil. The other rotor coil, at right anglesto it, is calied the sine coil. As the rotor rotatesfrom 0° to 3600, the voltage induced across thecosine coil follows the cosine function of theexcitation voltage. Similarly, the voltage inducedacross the sine coil follows the sine function ofthe excitation voltage.

SCHEMATIC IDENTIFICATIONOF SYSTEM COMPONENTS

In the maintenance publications for firecontrol systems, the devices described in thissection are identified by standardized symbols.The identifying symbols and their abbreviationsfor system components are reproduced in figure7-8. Usa;o of me of the component symbols ina sectiorH ,!i,q:7-am may be seen in figure 7-9.

UNDERWATER FIRECONTROL SYSTEMS

A modern fire control system is tailored tothe requirements of a particular weapon system.Aboard submarines, the weapon is either atorpedo or the SUBROC. Aboard surface ships,the weapon is either a torpedo or the ASROC.Regardless of the type of FCS used, each onehas the same purposeto direct the weapon tothe target.

STATORCOIL

E sin 0

E cos 0

ROTORCOILS

12.105Figure 7-7.Electrical resolverschematic symbol.


COS

StN

CAM

-LDFl-

COSINE MECHAN,m

SINE MECHAN,SM

NECHANICAL CANf OACTION GENERATING)

St..ErRACTNE LEVER0*.,-RENTiAL

.R.

r+1

IPA MECHANICAL INTEGRATOR

D GEAR DIFFERENTIAL

LJL LEVER MULTIPLIER

°ADDatvE LEvERDIFFERENT,AL

MECHANICAL COMPUTING SYMBOLS

(0.0,

r-L,)

If01).`

rgrp_t_i

MS SERVOMOTOR

R RESISHOR

H THTHITE RESISTOR

Sw THERMAL SWYCH

Sw mICROSwITCH

ROTART SviiTCH

RH RHEOSTAT

T THANSFoRmiR

OP DAMPING REACTOR

V VACUUM TUBE

-r F FUSE

L LAMP

Hi

rqm-,

C 1,APUCIT0R

C 'L'eN.T.HRO CaPAC.TGH

.0 REC T1FIER

SC T 50501150 CONTROLTRANSFORMER

MECHANICAL CONNECTIONIN AN ELECTRICAL SCHEMATIC)

ELECTRICAL CONNECTION

ELECTRICAL SYMBOLS

CO CAM MECHANICAL Cam

OF FRICTION DRP.E

uto St. Lima STOP

fm:di c MECHANICAL

0 DL DIAL

DL DIAL GROUP

COUNT E R

MC HANDCRANK OR KNOB

FRICTION TO FRAME

C7:3OL LINEAR OVERRIDE

C:=3

(5) OR ROTARY OVERDRIVE

ELECTRICAL CONNECTION(IN A MECHANICAL SCHEMATICI

MECHANICAL CONNECTION

MECHANICAL NONCOMPUTING SYMBOLS

-

-C>

L

A

SO

SOG

INDICATOR LAMP

AMPLIFIER

SYNCHRO DIFFERENTIAL mCFOR

SINCHRO DIFFERENTIALTRANSMITTER

CE

T

MAGNETIC CLUTCH ORMAGNETIC BRAKE

TIME MOTOR

SERVOMOTOR5

SCT SYNCHRO CONTROLTRANSFORMER

SW MICROSWITCH

SM SINCHRO MOTTR

SG SYNCHRO TRANSMITTER

SW CAM-ACTUATEDMICROSvoTCH

ELECTROMECHANICAL SYMBOLS

Figure 7-8.Identifying symbols and their abbreviations.

Surface Ship System

A shipboard underwater fire control system(the Mk 114 UBFCS) is illustrated in figure7-10. The system performs the followingfunctions:

I. Integrates associated fire controlequipment with own ship's components.

2. Receives target position informationfrom sonar or radar and combines it with ownship's and ballistic's data to produce weaponorders.

3. Provides aided tracking andposition-keeping information back to the sonar.

1 2 51 ?0

13.5

A detailed discussion of the complete Mk 114UBFCS is contained in Sonar Technician G 3 & 2,NET 10131-D. It is recommended that you referto the STG publication after completing thismanual.

Submarine System

When a submarine is on the surface, the firecontrol problem is essentially the same as asurface ship's. However, when the submarine isbelow the surface the tire control problembecomes much more complicated. Figure 7-11shows a representative submarine fire control

t_!ni (the Mk 113 FCS).


Rh5

B4 d(Rm)

HIGH SPEED

LOW.SPEED d(Rm)By5

d(Bmy))

HIGHSPEED

LOW.SPEED

VERY-LOW-SPEED

!CROSSOVERAMPLIFIER

k_

d(Rm) = IR/15

RATIOf_GEAR

Rh5

MG1

I

l''I

I ICROSSOVER

1

I AMPLIFIER

d(Brny)

MG1

d(Rm) SIN d(Bmy)= d(Rmx)

d(Rm)COSd(Bmy)=d(Rmx)

R3 I R2

d(Rm) SINE.COSINE

d(Rm) SIN d(Bmy)=d(Rms)

d(Rm)COSd(Bmy)=d(Rmy)

1

PRESET AT 60,000 YARDS

Rh5 SERVO MODULE1 .-1 dOmy) SERvO MODULE IL......

Rh5 SIN d(Bmy)=Rh5x

Figure 7-9.Rhs and d(Bmy) schematic diagram relay transmitter Mk44.71.131


POSITIONINDICATOR

MK 78 t

PERMISSION TO FIRE

PAYLOAD SELECTED, READY INDICATION,MISSILE OR WATER ENTRY POINT RANGE ANDTARGET RANGE, BEARING, AND ANGLE, ANDTRAIN ORDER

BEARING.LAUNCHER

ATTACKCONSOLE

MK 53

LAUNCHERCAPTAIN'SCONTROL

PANELMK 199

LAUNCHERAND MISSILESIMULATOR

MK 6

MISSILE AND RAIL SELECTION ORDERS;MISSILE VELOCITY, TIME TO SEPARATION. AND TORPEDO SETTINGS,STABILIZED LAUNCHER TRAIN AND ELEVATION ORDERS, ANDSTANDBY AND FIRE ORDERS

LAUNCHER AND MISSILE INTERLOCKS AND INDICATIONS

MISSILEVELOCITY

AND TIME TOSEPARATION

SETTINGS

LAUNCHER AND MISSILE INTERLOCKS AND INLICATIONS

MISSILE AND RAIL SELECTION CRDERS;TORPEDO SETTINGS; STABILIZED LAUNCHERTRAIN AND ELEVATION ORDERS; AND STANDB,AND FIRE ORDERS

RELAYTRANSMITTER

UK 43

ASROCMISSILE

LAUNCHERMK 112

MISSILE VELOCITY AND TIME TO SEPARATION SETTINGS

ISA CHECKS

Figure 7-10.Mk 114 underwater ballistics fire control system.

The Mk 113 FCS provides solutions forlaunchina the SUBROC missile and manydifferent mods of torpedoes. Due to theclassification of this subject, it will not bediscussed any further in this manual: the Mk 113FCS is discussed in detail in Sonar Technician S'3 & 2. NET I 0132-C.

FIRE CONTROL SYSTEM TESTS

Certain transmission. computing, and ratetests must be performed to ascertain that thefire control solution is correct and that valuesarc received correctly at remote stations. Also,

71.132

frequent operation of a system exercisesservosystems, power drives, and computingnetworks, thereby bringing attention to anyexisting trouble.

Transmission Tests

Transmission tests are held to cheek theaccuracy of automatically controlled devices atremote stations and to check their response tochanging signals. When running these tests, thefirst step is to establish voice communicationsbetween stations. Next, the man at thetransmitting station must read the exact output

122 127

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173


value of the quantity being checked. In turn, theman at the receiving station must adjust thereceiver to correspond to the reading from thetransmitting station.

Computing Tests

As sonar tracks a moving target, constantlychanging inputs are fed to the computer.Instantaneous values of these inputs are used bythe computer to solve ballistic computations andpredict future target positions. The computer'ssolution is, therefore, based on an infinitenumber of static (still) problems. As relativemotion rates are integrated with time togenerate computer changes in target position,the problem becomes dynamic. To test thecomputer's accuracy, consequently, both staticand dynamic tests are run.

(BMISSLEEARING

I

STATIC TESTSStatic tests check theoverall operation of the computing system in astandstill condition. In this type of test,appropriate test values are inserted manually,and the problem is stopped at a fixed point.Input test quantities are thus of a constant valueand produce fixed answers which do not changewith time. These fixed answers indicate whetherthe static portion of the fire control equipmentis performing properly.

DYNAMIC TESTS.Dynamic tests are runto check the computer's generation of bearingand range for specified time intervals against amathematical solution whose answer containscorrect amounts of change in quantities for likeconditions. During the test. fixed values areassigned to relative motion rates by manuallysetting inputs to the relative motion group. Thetime system of the computer is then moved,

TARGET

WATER)21,ENTRY

POINTc0\ts

/ \O\O

\,..,\ \,.5>

N00 \\ \

Bts 305°

c ( B 5) r- 313 °

C. 9

OWNSHIP

Figure 7-12.Missile and target dial and counter functions.

124

TARGET ANGLELINE OF SOUND

Elfs

5_ 1 o 1001TARGET RANGE

Ra

71.133


either manually or by the time motor, anamount equal to the test interval. Readings arethen taken to ensure correctness of the solution,

Rate Tests

Rate control tests check the functioning ofthe rate control system. Mechanisms of thissystem correct values, such as target angle andtarget speed, so that computer target motionrates agree with actual rates of the target. Inother words, this test dt termines the timerequired for the computer to arrive at correctrelative motion rates. Time required must besmall, but smoothness of tracking must also beconsidered. The rate control system is acompromise between these two factors.

Rate control tests consist of tracking ahy pot he t ical motionless target with thecomputer set for a selected sensitivity of rateerror detection. Sensitivity is controlled by thetime constant input to the rate control system.Initially a large error is introduced and the timemotor is started. Time required to reduce theerror by a preselected percentage is timed by astopwatch. This stopwatch reading is a measureof the actual time constant or sensitivity of thesystem. It is compared against the theoreticalvalue for the test.

Each fire control system is provided with aset of tests to determine the operating accuracy.Some are daily tests, some are weekly tests, andsome are monthly tests. Refer to the specific 01)or OP for each individual fire control systemtest,

INTERPRETING DIAL READINGS

Sonar Technicians must be able to interpretand sometimes interpolate sonar and fire controlequipment dial settings. Information to be readfrom these dials includes such values as range,target angle, true bearing, relative bearing, andmany other fire control values. Normally twotypes of dials are used: disc dials and ring dials.

A disc dial is simply a flat, circular platesecured to a shaft and inscribed with values oft he function it serves. A ring dial iscircular-shaped also, but has a hollow center topermit placing a disc dial within it. An exampleof the use of these dials is shown in figure 7-12.

125

130

Bdg LAUNCHER LINE OF SOUNDTRAIN ORDER

DIAL

\AILINSION,

ByaAPPARENT

TRUE TARGETBEARING DIAL

TARGET

_111late ,Ba

APPARENTRELATIVE

TARGETBEARING DIAL

LINE OFSOUND

340°Co:355°

71.134Figure 7-13.Own ship dial group functions.


The dial group on the telt shows the relativewater entry point bearing c(B5) of an ASROCmissile. The dial is read on the inner dial againstthe line index on the missile of the outer dial.The c(B.5) shown in this case is approximately313°.

The dial on the right shows the target angle(Bts) of the target being tracked. Target angle isread against the line or sound index. The Btsshown in this case is 305°.

Figure 7-13 shows the more complex ownship's dial goup. This group includes threeconcentrically mounted dials: an inner dial, anintermediate dial, and an outer dial. The innerdial displays apparent relative target beaiing Bawhen read with relerence to the LINE OFSOUND index. The inner dial is gaduated in 5°increments and is numbered in 30') incrementsfrom 0° to 360°. The Ba value is 3450 . Areasindicating bearings where own shipsuperstructure 1Nould interfere with missile firingare indicated on the inner dial as UNSAFE. Ownship's outline is also inscribed on the inner dial.

The intermediate dial of own ship's dialgoup contains a diamond index which indicateslauncher train order Bdg values when readagainst the inner dial. The Bdg value is 310°.The Bdg index, when read with reference to theinner dial, indicates launcher train order withrespect to own ship's bow. The intermediate dial

126

also indicates whether the selected weapon willclear the superstructure when lired.

The outer dial of own ship's dial groupdisplays apparent true target bearing Bya valueswhen read with reference to the LINE OFSOUND index. The outer dial is graduated in 5°increments and is numbered in 30° incrementslrom 0° to 360°. Own ship's course (notreceived as an input) can be interpreted by theposition of the bow or own ship inscribed on theinner dial against the graduations on the outerdial. This interpretation is possible because theequation for Co is: Co = Bya Ba. The Covalue shown in figure 7-13 is 355°.

The dials just discussed are only a few of themany that you must be able to interpret. Ofparticular importance is the ability tointerpolate (to "read between the lines-) and tonote direction of change of dial readings. Ourdiscussion of the fire control problem, and ofthe equipment used to solve the problem, wasnecessarily restricted to lundamentals.Co m put er mechanisms lire controlnomenclature, and antisubmarine weapons wereonly briefly covered, serving to acquaint youwith the problems involved in making attacks onenemy submarines. You need to study manytechnical manuals and other training courses tofully comprehend the duties of a SonarTechnician.

CHAPTER 8

COMMUNICATIONS

The essential factor in communicationbetween two persons is that the language theyuse be understandable to both. Not only mustone person be able to express himself clearly,but the other person must be able tocomprehend what is communicated.

Realizing that many problems areencountered in communications, the Navy hasadopted standard methods and practices tominimize errors and misunderstandings inmessage transmittal and reception. Many ofthese standard procedures are used by otherallied services. They are invaluable in conductingjoint international operations. The phoneticalphabet has been adopted by all allied forcesfor combined operations.

In this chapter you will become acquaintedwith some of the internal and externalcommunication systems used aboard ship.Additionally, you will learn correct operatingprocedures for radiotelephone and underwatertele phone communications. Because thephonetic alphabet and sound-powered (S/P)telephone procedures are covered in BasicMilitary Requironents, NAVEDTRA 10054.they are not included in this text.

INTERNAL COMMUNICATIONS

Most Navy personnel, regardless of rate, arefamiliar with internal communications. SonarTechnicians, especially, have occasion to useseveral ty pes of systems available fortransmitting sonar information. It is almostimpossible to conduct attacks on enemysubmarines or ships without some method ofinternal communications. On a destroyer, sonarcontrol may be located below decks, on the

127

bridge level, or in some other section of the ship(depending on the type and class of ship).Because it is remote from the bridge, sonicmeans of communication must be establishedbetween the bridge and sonar control. Thisrequisite is accomplished by utilizing one ormore of the internal communication systems.Shipboard circuits include MC (loudspeakers)circuits, sound-powered phones, and automaticdevices. These devices are remote indicators andare used to transmit bearing and rangeinformation, weapon status, and many othertypes of data needed by other stations.

When sonar contact is made, the bridgeusually is informed over an MC system. By thismethod, all stations concerned are alerted, andsound-powered phones are then manned toeliminate excessive noise levels caused by theconstant use of loudspeakers. The ASW officer isdirected to make the attack. Although most ofthe information flow is conducted on thesound-powered phones, the information isbacked up by automatic electromechanicaldevices so all stations are awaue of the progressof the attack.

SOUND-POWERED PHONES

The shipboard voice communication systemused most extensively is the S/P telephonenetwork. It consists of primary battle circuits JAto JZ, with auxiliary and supplemental circuitsfor use if a primary circuit is damaged. Thedegree to which these circuits are manned varies.Few circuits are used under normal peacetimecruising conditions. During general quarters,when all battle stations are manned, all circuitsmay be used.

132


Of primaiy concern to the Sonar Technicianare the JA, JP, and .IS circuits. The JA, thecaptain's battle circuit, is used for transmittingorders to key control stations and forexchanging vital information with those stations.Weapons control information is passed over the8JP circuit. The other S/P circuit you willprobably man is the 61.1S. It normally is used asa one-way system to provide contact range andbearing and other data to UB plot, CIC, and thebridge. The 1J S circuit is the mainantisubmarine attack team control circuit. Itconnects the bridge, CIC, and sonar control, andis used primarily for conning orders when sonaror CIC has control of an attack. Normally, the1JS is manned by officers in charge of thevarious stations.

Circuit discipline must be maintained at alltimes when you are wearing phones. Personalconversations with friends on the same circuitmay cause a delay in the transmission of vitalinformation, resulting in a delayed or missedattack. With the high speeds of modernsubmarines, such a delay could result in the lossof your ship or the ship you are trying toprotect.

MC SYSTEMS

Although sound-powered phones are themost common means of internalcommunications, there are other methods, oneof which is the MC (shipboard announcing)system. The MC system is an electronicspeaker-type system, similar to anoffice-to-office intercommunication system, andis designed to provide amplified voicecommunication.

Sonar and CIC underway watch stationsusually are not fully manned under normalcruismg conditions aboard ASW ships. When asonar contact is gained, the 29MC (sonar controland information) is used to alert CIC, UB plot,and the bridge. Contact information (such asranges, bearings, and doppler reports) is passedover this circuit until the contact is classified asnonsubmarine or until ASW stations can be fullymanned. Submarines utilize the 27MC (sonarand radar control) system.

Another communication system foundaboard most ships and submarines is the 21MC(captain's command system). It is a two-waysystem, with each intercommunicating unitcapable of calling either 10 or 20 stations,depending on the type of ship in which it isinstalled. The essential components are a

reproducer, amplifier, and controls necessary foroperation. The reproducer acts as a microphonein the calling unit and as a loudspeaker in theunit called. Amplification takes place in thecalling unit. The controls consist of the talkswitch, pushlnitton assembly, busy light, calllight, volume and dimmer controls, and amicrophone or handset jackbox.

To operate the 2IMC, depress thepushbutton of the station desired. If the stationis busy, the red BUSY light will flash. If theBUSY light does not flash, depress the TALKswitch and speak directly into the speaker grill.Release the TALK switch to listen. When yourconversation is completed, depress the releasebutton at the far left end of the row of' stationbuttons to remove your intercom unit from thecircuit. When you are called, the CALL lightilluminates. It is unnecessary to depress thebutton of the station calling: merely use theTALK switch as described herein.

Despite its many advantages, when the MCsystem is used, the noise level is increasedgreatly. This condition occurs because of itsspeaker-type output and the fact that it picks upbackground noise from the transmitting station.Because of the high noise level generated byoperating the 21MC, it should be used onlywhen absolutely necessary.

REMOTE INDICATORS

T h e fastest means of communicatinginformation is to transfer it electrically. Throughthe use of electromechanical and electronicrepeaters, sonar information is displayed atremote locations aboard ships and submarineswithout delay.

One ty pe of display, an electronicazimuth-range indicator, shows bearing andrange ot' a contact on a cathode ray tube. Itduplicates audio and video information presentat the sonar operator's console.

128

133

Chapter 8 COMMUNICATIONS

Another type of remote indicator displayssonar information electromechanically. Contactrange and bearing are shown by counters similarto an automobile's mileage indicator. There aremany other electromechanical transmitters usedto display sonar information. 'The mostcommonly used are the Mk 78 position indicatorand the Mk 44 relay transmitter used with theASROC weapon system.

As you can see, electrical/eieetronicrepeaters reduce the time required to transmitinformation, eliminate noise-producingtransnnssions, and reduce the volume of trafficover S/I' telephone circuits.

EXTERNAL COMMUNICATIONS

During antisubmarine operations (and, lorthat matter, all operations, it is iinperative thatconmumications between ASW units, such asships and aircraft, be conducted smoothly andefficiently, and he free of coniusion insofar aspracticable. If a faulty microphone switch of asound-powered phone frequently cuts out, thiscommon failure can prevent vital informationfrom getting through just as effectively as it" itwere not reported at all.

Poorly trained or .naen..Ve operators cancause confusion, delay, and mistakes, and mayeven create a dangerous situation.

RADIOTELEPHONE

Radiotelephone VD, commonly calledvoice radio, is a rapid means or exchanginginformation between ships, aircraft, andsubmarines. Voice radio usually is amplitudemodulated. A continuous-wave radiofrequencycarrier has an audio signal impressed upon it,varying its amplitude in accordance with theaudio variations. A handset or a carbonmicrophone is used to key the transmitter.

Although voice radio is a fast means ofcommunication, speed without accuracy is morethan worthlessit can be dangerous. When shipsare operating together at high speeds and inclose formation. a mistake or a delay incommunications can cause a collision.

119

In antisubmarine operations, voice radio isused to exchange contact and tacticalinformation het \Veen the CICs and bridges of theships participatir,g in the operation. The eaptainor the 001) mans the bridge radio circuit, usedprimarily to exchange tactical iniormation. TheCIC oilicer and the Operation Specialist handlethe combat information (('I) net to exchangecon t act in form at ion bet ween CICs. Contactinformation between (lc's is evaluated by tileCIC evaluator, and pertinent information isrelayed to the captain and 001) on the bridgeby use of sound-powered phones.

Because radiotelephone procedures are usedwith the underwater telephone and becauseSonar Technicians may be assigned CIC watchesduring normal cruising conditions, it is necessaryfor y ou to be fa III liar with properradiotelephone procedures.

RADIOTELEPHONE PROCEDURES

When you use a radiotelephone, your speechmust be clear and slow. Speak the message bynatural phrases not in stilted, word-IV-wordfashion. Use a normal tone: don't shout.Pronounce word clearly and distinctly.pausing at intervals. Think about what you aregoing to say, then say it. Keep the message asbrief as possible.

Heading

The basic format oi a military messageconsists of the heading, text. and ending. Themessage form is in plaindress, abbreviatedplaindress, or codress. Codress is an encryptedmessage, with which a Sonar Techniciannormally is not concerned. Plaindress is used forradiotelegraph and teletype communications. aswell as for radiotelephome administrativemessages. A plaindress message usually has acomplex heading, consisting of call. transmissioninstructions, precedence. date-time group.address. and other elements. The type ofradiotelephone message you will use most .however, is the abbreviated plaindress. in whichthe b iding includes only the station called andthe station calling. In some instances, ;titercommunications are established, the heading

1 24-


contains only the station calling. An example ofa typical heading is: BR ASSPLATE --THIS ISESKIMO.

Text

The text of' the message is the basic thoughtor idea the originator wishes to comniunicate. Itfollows the heading, and is separated from it bythe word BREAK. Quite often radiotelephonemessages, particularly those of a tactical nature,are coded. There are several reasons for codingmessages. The first is obvious: so that the enemywill not know your intentions. Ii, f'or instance,you were ordered in plain language tocommence a sonar listening sweep and themessage was intercepted by an enemysubmarine, he could rig for silent running toreduce his noise output to a minimum, makingyour job all the more difficult. If the message issent in code, however, chances of interpretationby the enemy are reduced even though heshould intercept it. Another purpose is brevity.The less time on the air, the better (for bothsecurity and practical reasons).

Signal codes are contained incommunication publications known as signalbooks (of which there are several), each having aparticular application. One signal book consistsof two letters, or a combination of letters andnumerals, that usually are used for tacticalsignals. (Members of NATO use this book, aswell as the standard phonetic alphabet, forcombined operations.) As an example, a certaintwo-letter and a numeral signal tells all ships tomake oil fog and smoke. From his signal book.the captain of an Italian ship can read andunderstand the meaning of the signal as quicklyas the captain of a U.S. Navy destroyer. Twoletters and a numeral thus overcome thelanguage barrier and make a brief message aswell.

Another means of reducing transmissiontime and providing a degee of security is

through the use of brevity code words. Ingeneral, these code words are used to conveycontact and related information.Communications publication ACP 165 containsthe operational brevity code.

At the end of the text, the word BREAK isused again to separate the text from the ending.

130

135

Ending

The ending or a radiotelephone messageconsists or one of two wordsOVER or OUT.When OVER is used, the :;ender is telling thereceiver to go ahead and transmit, or "This is theend of my transmission to you and a response isnecessary." With the use or OUT, the sender ineffect is telling the receiver: "This is the end ofmy transmission to you and no response isrequired." In motion pictures and televisionproductions, you are likely to see militarypersonnel say "Over and out," hut there is nevera need for their combined use in this manner.

CALL SIGNS

In radiotelephone procedure, ships have callsigns that are common, easily pronounced wordsor expressions. The radiotelephone call sign of'one ship, for example, is BLUE STAR: anotheris BEANSTALK; still another is EL TORO. AllU.S. Navy ships are assigned a voice call sign. Ifyou need to know the voice call sign of anyNavy ship, you can find it in the communicationpublication JANAP 119.

PROWOR DS

Radiotelephone procedure also requires theuse of standard procedural words calledprowords. Although prowords are not codewords as such, they say a geat deal with theutmost brevity. The words OVER and OUT,mentioned earlier, are prowords. Besides OVERand OUT, two other prowords that are neverused together are ROGER and WILCO. ROGERis used as a receipt. It merely means that youhave received the messagenot that youunderstand it or will carry out any orderscontained in it. WILCO is the answer to theproword ACKNOWLEDGE and means that youwill comply with any instructions or orderscontained in the message. For this reason, theproword WILCO must never be used withoutspecific permission from a person having theauthority to grant such permission. This personis usually the commanding officer of your ship.

Following is a list of the more commonprowords, the meaning and usage of which you

Chapter 8COMMUNICATIONS

should memorize. This list is not as complete asthe lists in communication publications. ltconsists mainly of the prowords you are mostlikely to hear and use on the underwatertelephone. Should you be interested in seeing amore complete list of prowords, check NTP-4 orACP 125.

Proworii Meaning

ALL AFTER All after.

ALL BEFORE . . . All before.

BREAK The text is separate atthis point. Do notconfuse the separatedportions.

CORRECTION . An error in mytransmission has beenmade. I now correct it.

DISREGARD This entire transmissionTHIS is in error. Disregard it.TRANSMISSION

FIGURES Figu res or numeralsfollow.

FROM This message isoriginated by

I SAY AGAIN I re peat the entiretransmission (orportions indicated).

I SPELL I shall spell the nextword with the standardphonetic alphabet.

OUT This is the end of mytransmission. No receiptis required.

OVER Go ahead with yourtransmission at thistime. (Or, this is the endof my transmission forwnich a response isrequired.)

Ersav_ad

ROGER

Mqaailig

I have received your lastt ransmissionsatisfactorily.

SAY AGAIN

THATISCORRECT

THIS IS

TIME

TO

Repeat all (or portionsindicated) of yourmessage.

You have repeated mymessage or have giveninformation correctly.

This message is from.

What follows is the timeor date-time group ofthis message.

This message is foraction by and isdirected to

WAIT I must pause ror a fewseconds.

WAIT OUT I must pause for longerthan a few seconds.

WILCO I have received andunderstood yourmessage, and you havethe assurance of thecommand that it will becomplied with. (Thistype of answer requiresCO's permission.)

WORD AFTER . . . .

(word)

WORD BEFORE(word)

WRONG

i '3 6

131

The word after (word)is

The word before (word)is

Your last transmissionwas incorrect. Thecorrect version follows.


INTERNATIONAL MORSE CODE

The international Morse code is a telegraphicalphabet, which is another way of saying that itis a dot and dash communication system. Thecode is pronounced by saying "dit" and "dah,"not "dot" and "dash," so forget about dots anddashes and think only in terms of dits and dahs.The group of dits and dahs representing eachcharacter must be made as one unit, with a clearbreak between each dit and dah, and a muchmore distinct break between character.

Never try to identify a character by countingdits and dahs. Don't let yourself get into thishabit. It's a temptation at first, but you won'tbe able to count fast enough when the codespeed picks up. Learn sound patterns instead. Tounderstand what this requirement means, rapout the pattern beginning "Shave and a haircut."You recopize this ditty from its characteristicrhythm, not because it has a certain number ofbeats in it. You must learn code the same way.Each character has its own distinctive soundpattern. With study and drill, you will learn torecognize each pattern as fast as you nowrecognize "Shave and a haircut." The accentalways falls or. dahs, and you should pronounceeach rhythmical combination with that rule inmind. Go through the alphabet several times toget the feel of the sound of the dit-dahcombinations.

THE CODE

In the pronunciation guide for the sounds ofthe characters in the accompanying list, thesounds are written out phonetically insofar aspossible. The short sound "dit" actually takeson the sound "di." The "i" is very short and the"t" is dropped.

Letter Pronunciation

A di-DAH

DAH-di-di-dit

DAH-di-DAH-dit

DAH-di-dit

13?

137

Letter Pronunciation

dit

di-di-DAH-dit

DAH-DAH-dit

di-di-di-dit

di-dit

J di-DAH-DAH-DAH

DAH-di-DAH

di-DAH-di-dit

DAH-DAH

DAH-dit

0 DAH-DAH-DAII

di-DAH-DAH-dit

DAH-DAH-di-DAH

di-DAH-dit

di-di-dit

DAH

di-di-DAH

V di-di-di-DAH

di-DAH-DAH

X DAH-di-di-DAH

DAH-di-DAH-DAH

*Z DAH-DAH-di-dit

*ZULU is written as -Z- to avoid confusion withthe number 2.


Number

2

3

4

5

6

7

8

**0

Pronunciation

di-DAH-DAH-DAH-DAH

di-di-DAH-DAH-DAH

di-di-di-DAH-DAH

di-di-di-di-DAH

DAH-di-di-di-dit

DAH-DAH-di-di-dit

DAH-DAH-DAH-di-dit

DAH-DAH-DAH-DAH-dit

DAH-DAH-DAH-DAH-DAII-

Study and Practice

If you have any trouble learning code, thefollowing method may be helpful. Go throughthe three groupings of short, medium, and longsounds with their accompanying practice words.Make up words of your own if you wish furtherpractice. Speak the practice words in code. Say"TEE: DAH dit dit: MINE DAH-DAH-di-ditDAH-dit dit."

Short Sounds

T DAH

A di-DAH

I di-dit

NI DAH-DAH

N DAH-Dit

Medium Sounds

D DAH-di-dit

G DAH-DAH-dit

K DAH-di-DAH

O DAH-DAH-DAH

P. di-DAH-ditIf you can speak words rapidly and

distinctly in code, you'll have an easy time of it,when you learn to receive code, because the S

spoken code and transmitted code sounds aresimilar. Practice the figures in even gr oups: 11,22, 33, 44, 55, 66, 77, 88, 99, etc. Learn eachletter by overall sound. Never count the dits anddahs.

Short Sounds Practice Words

E dit TEE, ATE, EAT. TEA.MEAT. MEET

U di-di-DAH

W di-DAH-DAH

Long Sounds

**Zero is written as 0 to avoid confusion with B DAH-di-di-dit8the letter 0.

133

Practice Words

MINE, TIME, MAINE,TEAM

AIM, NITE, TAME,TEA, MATE

TAME, NAME, MITE,MIAMI

MAMA, MEAN, MAN,MAT. EMIT

MINT, MANE, TAN,ITEM, TINT

Practice Words

MUST. SAME. MAMA,SUIT. AUTO

MUSS. OUST, MUSE,MUTE, ATOM

TAUT. MASS. MAST,SUET. SAM. WIND

SEA, TUM. SAW,OAT. SUE, SAT.WED

SUM. MUD. IOU,USE. SEMI, DARK

GEORGE, DOWN,KIND, SORT,MASK

WORK, GROW,URGE, TUG, PULL

WIGS. WORN. WET.WAKE, WALL

Practice tVords

BAT. BALL. BEAT,GLIB. GAB, JAB


Long Sounds

C DAH-di-DAH-dit

F di-di-DAH-dit

H di-di-di-dit

J di-DAH-DAH-DAH

L di-DAH-di-dit

P di-DAH-DAH-dit

Q DAH-DAH-di-DAH

V di-di-di-DAH

K DAH-di-di-DAH

( DAH-di-DAH-DAH

DAH-DAH-di-dit

Practice Words

CUT, CAM, COAT,CODE, CALF

FIVE, FAT, FUSS,FEET, EFFECT

ACHE, HUSH, HAVE.HOLD, HOT

JERK, JIM, JAR,JAM, JAB

LIKE, LAG, JELLY,LOVE, LATE

PUSH, PAIR, POLE.PART, HAPPY

QUAY. QUEBEC.QUEEN. QUIZ,QUIT

VIM, VERY. VETCH,VAT, EVE

WAX, XRAY, LYNX.SIX, EXAM

YOUNG, YOKE,YAK, JERKY,YAM

ZERO, BUZZ.FIZZLE. QUILL,LYNX

handkey. The ship or station to which you areattached has a practice handkey you can use.

Find a Radioman who will key code groupsto you to help you in your training. The soundproduced by keying an oscillator resembles thesound of code from the sonar transmitter.

After you learn the sound of each characterat a slow rate of speed, it is not difficult toreduce the time between characters and thus tocopy at a much faster speed. But don't strive forspeed before accuracy. Be a competent operator.Ma ke eve ry t ransmission and receptionaccurately. Accuracy is much easier if you learnthe fundamentals well. Some code practiceexercises that will help you are included foryour convenience.

2.

4.The only way to learn code is by

racticecontinual practice. The value ofractice cannot be overemphasized as you willarn when you test yourself, with the help ofDur shipmates. to find out how well you haveweloped your skill through practicing by 5.)urself.

If you have carried out thecommendations made up to this point, you aready to receive code transmitted to you on a

CODE PRACTICE

EEE TTT AAA 0110 I I I OSS 11110 PRP

VI.M.M 000 SSE

OSS 1 1 1 1 0 MM.M RRR 000 EES TTT I I I

TTT SEE TTT I II NON SSS 000 AAA

NON SEE AAA NON

1100 VVV DDD BBB SHE CCC WWW JJJPPP 0110 VVV ODD BBB XXX CCC WWW

JJJ PPP VVV DUO BBB CCC EKE< 111,:W

DDD ERR BBB CCC LWW DUO VVV JJJCCC WWW SKS PPP

RRP LI. L REF GGG Z Z Z XXX YYY QQ0

PRO LLL EFF

7.1QQ GGG 222 DLL YYY REP OFF LLD

QQO RRR MXX 222 YYY LLL GGG

LLL QQ1L":'/Y

111 222 333 444 555 666 777 888999 000 111 222 333 444 555 666

000 123 456 789 000113 344 225 577 668 800 992 220

TTT AAA NON I I SSS

TTT 000 I II SSS

DOD VVV JJJ L'UU

DOG QQ0 222 Yr/ 555

DUO Z Z Z XXX RRR LLD

77 888 999

123 456 789 012 345 678 905 599

VUIY Q 2 CX 0p0555) 11

Z X V E I 14

C I X 21. 0 RV 1:F.V5:WSXEDCRFOTGB:4 I

S LEJPOSZPIFCVBEBVPSTDOTMEG

II 11 0 A E: ': V A 0 V/ r.; 0 11

134 139

P'./ A XEDCRFVT


CODE PRACTICE

6. EBY 7 B 5X1S 0 Z 2A 3C 5S 4 12 Fu 1 F

5 D 8Q 4 T 6 U 9 Q EOS 5U1 YG 2 J 4 S 3

E5T7Z8K6M9RIA2P.S7W8E982A3 Z 3 X 6 C 8 13 7 C 6 TE 8 V 7E35 yOF 1W 4

F 1 A 7 1588541N6C2K 3A92326027. WI AN TY SX EC LV OD 01 SP TZ EC NU VA EH LM DQ

BM ZS CD QA IU SC PQ OW IE UR VT LA KS JO HF GM

ZN X0 CV QZ WM EC RV TB YN UM IL OP AE SR DT FY

HU 21 KO LO ZS MD CF VG BH NJ MK SW ME CR VT BY

NU MI LO PS DO FI GY BU IN 211 HA MR TV TV YB NU

8. DE FT BY 72 VA 54 98 IM BT BT 11 34 66 CV VF TG

62 84 QA WS RP 54 20 BY 77 GY AA YF UH IJ VD BE

K 99 25 56 83 25 LA KS JD CY BU IN EB QV QV ZZ

22 00 TT 75 44 VY 53 VS CW MC WH 66 FS SS ER FE

26 CG PL IA LE FG QY 85 RI 39 NE JE SI 25 37 AP

9. WNT AGR DTS ELY BFC NZX REH KCE HIJ ACE RNG TCV

EPL ZSW QAB SHL GBT VRT GUM GYO DCM MSD ZAU YER

DLN APG VNB EDX BWS UTA PHI KTZ HBY ALE RDC TOC

ESN IUP PKJ NYH GHT DPP VED SWN VBT XFZ RDA FUO

NYH OLX RWH MKY ATA NM; RGE SKZ KDG OKL OIX GLM

11.

OLVHM

MSHTY

BZWCN

KFREO

DEHLY

NWZIH

ADXFR

XVHRW

(T)t."(

VXH7G

PROSIGNS

CODE PRACTICEYBLUR

VI ZNT

JNICDU

LMXMV

HEMP

ZXCKA

3IQCA

CJ.MNJ

RGBNS

MOHIZ

EFILMQ

TLZKL

NHEM2

OVICT

ABLBE

ABDEF

RNVUT

AZCWI ZYSKQ

LinTGW WNLIP

UTHAV

FSTRO

VCXTP

2219Y TX356

NCE1P.P

TNBLU

2TUBD

T148P

FINXC

JNCYZ

ZVNEW

KNXFC

IQAWM

WBEOX

DREDC

JHKNI

CGFH5

BTOZX

Procedural signals, called prosigns, are usedby radiotelegraph operators for the same reasonthat prowords are used by radiotelephonetalkers. Most prowords have an equivalentprosign, which, in several instances, is anabbreviation of the proword. You will notice inthe accompanyimY, list of prosigns that some ofthem are overscored. Overscoring means that theletters are to be sent as one character; that is,without the normal pause between letters.

Prosign Proword Meaning

AA ALL AFTER All afterAB ALL BEFORE All beforeWA WORD AFTER Word afterWB WORD BEFORE Word before

OVER Go ahead andtransmit.

AR OUT End of trans-mission; noreply expectedor desired.

AS WAIT I must pause fora few seconds.

AS AR WAIT OUT I must pause longerthan a few seconds.

Remarks

Used to identifyportions of atransmission whenrequesting arepetition.

Every transmissionends with one orthe other of theseprosigns.

BT BREAK Long break Separates text ofmessage from head-ing and ending.

135


Prosign Proword Meaning RemarksII

Separative Used for all otherseparations inmessages. Write itas a short dash.DE FROM From

EEEEEEEEE...CORRECTiON I just made Corrected versionan error. is sent immediately.

EEEEEEE

IMI SAY AGAIN Repeat

AR DISREGARD THIS TRANSMISSION

ROGER I have received allof your last trans-mission.

Sending

Your ability to send code depends mainly ontwo considerations. First, you must know thecorrect sound of the character you areattempting to transmit. Second, you must knowthe correct method for keying. Practicing thecode aloud, as well as receiving it by oscillator,should give you a good knowledge of codesound. The proper method for keying is yournext concern.

Probably the first key you'll encounter is theunshielded telegraph key, normally used onpractice oscillators on shipboard and on stationcircuits. The key must be adjusted properlybefore you can transmit clear-cut characters. Ahandkey, with parts labeled, is shown in figure8-1.

A spring tension screw, behind the keybutton, c, .1trols the amount of upward tensionon the key. The tension desired varies withoperators. Too much tension forces the keybutton up before the dahs are completelyformed; spacing between characters is irregular,and dits are not clearly defined. If the springtension is very weak, characters run together andthe space between characters is too short.

The gap between the contacts, regulated byhe space adjusting screw at the back of the key,hould be set at 1/16 for beginners. This

136141

measurement does not apply to every key andoperator; it is a matter of personal preference.Some operators like a closed key, others an openkey. "Closed" and "open" are terms for a shortand long gap. As the student progresses, furthergap adjustment may be made to suit his sendingspeed. Contacts that are too close have an effectsimilar to weak spring tension. Contacts that arespaced too far have the same effect as too muchspring tension.

The final adjustment of the key is thesidewise alignment of the contact points. Thisalignment is controlled by the trunnion screwsat either side of the key. If they are too tight,the key lever binds. If they are too loose, thecontacts have sidewise play. Usually, when thesidewise alignment is correct, no furtheradjustment is required.

From the beginning you should learn thecorrect way to grasp the key. The followinginstructions, in the order listed, constitute theproper procedure for becoming a proficientoperator: Do not hold the key tightly, but letyour fingers rest lightly on the key knob. Yourthumb rests against the side; your forefingerrests on top of the key: your third finger is bentand relaxed with the remaining two fingers.

Speed and accuracy of transmission depend,to a large extent, on acquiring the propermovements of your wrist and hand while


operating the key. To close the key, your wristmoves upward and your hand rocks downwardtoward your fingertips. To open the key, thesetwo movements are reversedyour wrist comesdown and your hand rocks back. A dah shouldbe about three times as long as a clit.

Conditions of the water have a bearing onthe speed at which you will be able to transmit.At times you can transmit rapidly and yoursignals will be clearly audible. Other times youmay have to go very slowly, otherwise your ditsand dahs cannot be distimzuished by thereceiving operator.

UNDERWATER COMM UN ICATIONS

For many reasons it is necessary for a shipand a submerged submarine to communicatewith each other. Of paramount importance isthe safety of the submarine and its crew. Duringexercise periods, the ship can advise thesubmarine when it is safe to surface. Should anemergency arise aboard the submarine, the shipcan be so informed. Exercises can be started andstopped, or one in progress can be modified, byusing the underwater telephone. Attackaccuracy can be signaled by the submarine tothe attacking ship. Sonar Technicians must be

SPACE ADJUSTINGSCREW

LOCI< NUT

BINDINGPOST

T RUNNIONSCREW

1

BINDINGPOST

LATERALBLOCK

TRUNNION SCREW

SPRING TENSIONSCREW

LOCK NUT

KEY LEVER

LOCI< NUT

LATERAL BLOCK TENSION SPRING

\ ,

(..,;::\i...T .,...___ _4/<,..._..---_-,-,--

----------------____ -,-,,,,.:. .,.,..i,s.:____-rr.,," \1

....... \1 \ ,-..._ ..__. \

KEY BUTTON

,--- CONTACTS

Figure 8-1.Handkey.76.8A

142 137

proficient in radiotelephone procedures becausethose techniques are used for underwater voicecommunication. When CW (radiotelegraph) isused, you must be able to send and receiveM orse code wi thout Causing delay ormisunderstanding.

The most widely used underwater telephoneinstallation is the AN/WQC-2 (and modification)sonar set, commonly called SEATALK.Although intended for use by sonar controlpersonnel, some installations provide remotevoice operation from the bridge. The WQC-2operates at frequencies that are compatible withall other existing underwater telephone units.Figure 8-2 shows the front panel controls of theAN/WQC-2. As can be seen in figure 8-2, theAN/WQC-2 has all of the capabilities of theolder AN/UQC-1 (fig. 8-3), with manymodifications for better transmission andreception.

The range of transmission varies with waterconditions, local noise level, and reverberatione ffects. Under normal sonar conditions,however, communication between ships shouldbe possible at ranges comparable to those of theUQC-1. Under the same conditions, submarinesachieve a greater range. If the submarines areoperating in a sound channel, thecommunication range may be many milesueater than that achieved by surface ships.

Local noise, caused by ship's movementthrough the water, machinery, screws, etc., canreduce the range to less than half the normalrange. Severe reverberation effects may alsocause a reduction in range, but you canovercome them by speaking slowly, pausingafter each word to let the echoes die out. Atvery short ranges, it may be impossible to reducethe receivimz gain to a comfortable speakeroutput level. Then, you must speak softly,holding the microphone away from your lips.

VOICE PROCEDURE

As mentioned earlier, you will use the smilevoice procedures for underwater voicecommunication as for radiotelephonetransmissions. In other words, you call thestation for which you have a message, identifyyourself, send your message, and end thetransmission with either OVER or OUT.


Calling and Answering

Here is an example of a call from asubmarine (call sign COPY CAT) to an ASW ship(call sign SHARK FIN). Dashes shown are notactually sent but indicate pauses the operatormakes so that his transmission can beunderstood more easily.

SHARK FINTHIS IS COPY CATOVER.

COPY CATTHIS IS SHARK FINOVER.

LISTENSWITCH

VOLUMEHIGH

CONTROL

MODESELECTOR

SWITCH

With communication established, COPY CATsends his message:

SHARK FINTHISIS COPY CATBREAKAM AT EXERCISE DEPTH.READY FOR COMEXBREAK--OVER.

SH ARK FIN gives a receipt, using anabbreviated call:

THIS IS SHARK FINROGEROUT.

XM ITSELECTSWITCH

POWERLEVELSWITCH

VOLUMELOW

CONTROL

DIMMERCONTROL

Figure 8-2.--AIWINGIC-2 front panel controls.

138

1 A '1

CW KEY

POWERXMITINDICATORLIGHT

POWERONINDICATORLIGHT

XDCRON-OFF SWITCHSWITCH

141.296


Following is an example of a related series ofmessages between ships conducting an ASWexercise.

S EA POW E R THIS IS TOP HATBREAKSTANDBY MY "BASSET"PORT-2 MIN.BREAKOVER.

TOP HATTHIS IS SEA POWERBREAKROGERWILL REMAINCLEAR OF YOU UNTILCOMPLETION YOUR ATTACKOVER.

THIS IS TOP HAT.ROGEROUT.

Correcting an Error

If you make an error in transmission, sendthe proword CORRECTION immediately. Goback to the last correctly sent word, repeat it,and continue with the correct version. Example:

CuPY CATTHIS IS SHARK FINBREAKROGER YOUR YFILOWALL HERECORRECTIGNALLCLEAR TO COME TO PERISCOPEDEPTHBREAKOVER.

Figure 8-3.AN/UQC-1 control unit.

Waits

When an operator finds it necessary to delaytransmission momentarily, he sends the prowordWAIT. If the delay is for longer than a fewmoments, the transmission is WAIT OUT. A newcall is made when communication is resumed.

Repetitions

The request for a repetition is SAY AGAIN,not "Repeat." Used alone, SAY AGAIN means"Repeat all of your last transmission." Followedby identification data, it means "Repeat theindicated portion of your transmission." Theanswer to SAY AGAIN is I SAY AGAIN,followed by the repetition requested. Forexample, COPY CAT asks SHARK FIN torepeat all of his last transmission and SHARKFIN complies.

THIS IS COPY CATSAY AGA1NOVER.

THIS IS SHARK FINI SAYAGAINBREAKROGER YOURYELLOWALL CLEAR TO COME TOPERISCOPE DEPTHBREAKOVER.

If COPY CAT missed only the word DEPTHS,he would frame his request as follows:

THIS IS COPY CATSAY AGAINWORDAFTER PERISCOPEBREAKOVER.

When COPY CAT has the complete message, hesends a receipt.

Cancelin, a '...r3ssage

To cancel a message in prowess, ceasesending immediately and transmit the prowordDISREGARD THIS TRANSMISSION.Example: SHARK. FIN'S operator bminsmessage, then is ordered to delay it.

COPY CATTHIS IS SHARK FINBREAKTAKE STATION MY PORT-

71.71 DISREGARD THIS TRANSMISSIONBREAKOVER.

141 139


Once a message is receipted for, it cannot becanceled by means of the prowordDISREGARD THIS TRANSMISSION. Instead,a new message must be sent.

SUBMARINE COMMUNICATION1IETHODS

The AN/WQC underwater telephone is the;ubmerged submarine's primary means of:ommunicating with surface ships. For thiseason, during exercise periods, ships areequired to man the WQC continuously. Intddition to its required use for safety purposes,he WQC is used throughout an exercise by ships.nd submarines for sending attack signals,)btaining range checks, transmitting sonar shortignals, and for several other purposes. Subjecto equipment limitations, keyed sonar is theacondary means of underwater communica-ions. Many submarine sonars do not haveV capability.

Emergency communication equipmentarried by a submarine include a radio and a,tlephone. The radio is battery-powered andoats to the surface upon release through theignal ejector. Once on the surface, itutomatically transmits on emergencyidio frequencies.

The emergency telephone, designated.N/BQC-1A,B,C, is also battery-powered and isDrtable. It has the same voice frequencylaracteristics as SEATALK, with a range of)out 5000 yards. The usual installation7ovides one set in the forward escapemipartment and one set in the aft escape)m pa rt ment. In addition to its voice

145140

transmission capability, the AN/BQC can emit a24.26 kHz continuous tone for homingpurposes. The AN/BQC-1B and C also provide a9.58 kHz tone for homing.

Submarine rescue vessels have equipmentcapable of detecting and homing on the tone.With all batteries in good condition, 72 hours ofcontinuous tone transmission are possible.Range of the homing signal is 2000 to 5000yards.

Colored flares and smoke signals affordanother means of communication. Black orgreen signals are used by the submarine toindicate the simulated firing of torpedoes and tomark her position. A yellow flare or smokesignifies the submarine intends to surface. Shipsmust then clear the area and keep other shippingaway. A designated ship notifies the submarinethat the siLmal was sighted and informs himwhen it is safe to surface. A red flare denotestrouble. It means the submarine is carrying outemergency surfacing procedures. If the flares arerepeated or if the submarine fails to surfacewithin a reasonable length of time, it can beassemed he is disabled and requires immediateassistance. You must make every effort tomaintain sonar contact and establishcommunications by any means possible, butpreferably by voice.

Detailed pyrotechnic, sonar, and explosivesignal information is contained in FXP 1. AllSonar Technicians must become familiar withthe signals in that publication. The rescue of adisabled submarine's crew could depend on yourability to establish and maintain reliablecommunications.

CHAPTER 9

TEST EQUIPMENT; TEST METHODS; MAINTENANCE

Sonar Technicians must assist in the upkeepand repair of the sonar equipment aboard theirship or station. Consequently, you must becomefamiliar with the types of test equipment, testmethods, and safety precautions to be observedwhen using or working on electronic equipment.Naturally, a knowledge of electronics is requiredalso. Information related to the electronics fieldcan be found in Basic Electricity, NAVEDTRA10086, and Basic Electronics, Vol. I and II,NAVEDTRA 10087. Information on theselection, care, and use of hand and portablepower tools is contained in Tools and TheirUses, NAVEDTRA 10085.

SAFETY

Maintaining electrical and electronicequipment is a dangerous business. Every year,lives are lost aboard ship due to electric shock;and, in most instances, death could have beenavoided by observing appropriate safetyprecautions.

Most people treat with extreme caution acircuit containing serveral thousand volts, butact with indifference toward the commonhousehold current. Yet, 115 volts a.c. is theprime cause of death from electric shock. Caseshave been recorded of fatal shocks from suchNuipment as portable drills and grinders, fans,;movie projectors, and even coffee pots. Youmust continually be alert when working with:lectricity, and you must follow strictly all)ertinent safety precautions.

Although some safety practices are given in:his chapter, you should become familiar with:he safety instructions contained in the'ollowing publications: Nil VSE/1 Technical

141

146

Manual, Chapter 9670; Handbook of TestMethods and Practices, NAVSHIPS0967-000-0130; Safety Precautions .Thr ShoreActivities, NAVSO P-2455; and Nary SafetyPrecautions for Forces -Afloat, OPNAVINST5100.19.

GENERAL SAFETYPRECAUTIONS

Whenever possible, deenergize the mainpower input to any equipment before you workon it. Remember, though, that there still may bepower in the equipment from such externalsources as synchros, remote indicator circuits,and instrument heater elements. When you openthe switch in the main supply (or any otherpower switch), indicate the switch is open byattaching to it a tag reading "THIS CIRCUITWAS ORDERED OPEN FOR REPAIRS ANDSHALL NOT BE CLOSED EXCEPT BYDIRECT ORDER OF (your name, or name ofperson in charge of repairs)."

If you must work on an energized circuit,observe the following safety precautions.

I. Never work alone. Have another man,qualified in first aid for electric shock, present atall times. He should also be instructed in how tosecure the power.

2. Use insulating rubber matting. Thematting must be kept clean and dry. Wearrubber gloves, if possible, and use insulatedtools. Remove rings and watches.

3. Use only one hand whenever possible.Keep the other hand behind you or in yourpocket.

4. Do not indiscriminately stick your handinto an enclosure.


5. Have ample illumination.6. Never short out, tamper with, or bypass

an interlock.

Before working on a deenergizedcomponent, discharge all capacitors in the unit.A capacitor is a device for temporarily storingelectrical energy. Successive small charges arebuilt up in the capacitor for later release. Sonartransmitting equipments utilize this feature bybuilding up electrical energy in the equipment'scapacitor bank between each ping. A triggerpulse then releases the energy in a singlehigh-powered pulse. Nearly all types ofelectronic equipment use capacitors of varyingsizes and types. Normally, the larger thecapacitor, the higher the electrical charge it willhold for a greater length of time. On manyelectronic equipments, charges upwards of14,000 volts are present. Usually, such largecharges are discharged by mechanical meanswhen the equipment is opened. Many othercapacitors, however, must be dischargedmanually by the man working on the circuit.

To drain capacitor charges, the device youwill use is the shorting bar, shown in figure 9-1.The shorting bar usually consists of a copper rodwhich has an insulated tulip on one end. A heavybraided cable is soldered to the rod near thegrip. On the free end of the cable is a batteryclip. When using the shorting bqr, first securepower to the equipment, clamp the cable clipfirmly to the frame or other good ground, thendischarge each capacitor by holding theinsulated handgrip and touching the terminals ofthe capacitors with the copper rod. Alwaysground the capacitor at least twice because thecapacitor's charge may not be completelydrained by one application of the shorting bar.

Practically all electronic equipments have ametal grounding strap connecting the equipmentchassis to the ship's hull. The purpose of thegrounding strap is to place the equipment'sframe and the hull at the same electricalpotential, thus permitting personnel to touchthe equipment without danger of receiving anelectric shock. As you know, a difference inpotential is what causes current to flow. If acomponent should develop a short to thechassis, the short-circuited power will bleed ot'fto round through the strap. If there is a faulty

147 142

,L'InR)SpLDER

GROUNDINGCABLE

GROUNDINGCLIP

1.1

Figure 9-1.Shorting bar.

or open ground strap connection, however, apotential difference is established. Should youthen come in contact with the equipment, youbecome the ground strap. In other words, thecurrent passes from the equipment through youto ground, resulting in an electricshockpossibly a fatal one. You must ensure,therefore, that all ground connections are tightand free of foreign matter, such as dirt, grease,or paint, that might interfere with the requiredmetal-to-metal contact at the ground connectionpoints.

Fuses are another source of potel....,to the careless Sonar Technician. The purpose ofa fuse is to protect electric circuits andcomponents. A fuse blows because more currentthan the fuse can handle tries to pass through it.The cause of the current overload may be amomentary surge in ship's power, or it may be ashort circuit. Whatever the cause, twoprecautions must be observed when replacingfuses. First, use a fuse puller, even if power issecured. (Although it is desirable to securepower to the affected circuit, it is not alwaysnecessary or practical to do so.) If you use ascrewdriver, pliers, or your bare fingers, youmay receive a severe electric shock if youcontact adjacent live circuits. Second, alwaysreplace a fuse with one having the same rating.Substituting a higher rated fuse may causeserious damage to the equipment. If the chcuitdoes not burn out, dangerous potentials mayexist that normally would not be present, thusendangering servicingpersonnel.

Cathode ray tubes (CRTs) are used in allsonar equipment. They are of rugged

Chapter 9--TEST EQUIPMENT: TEST METHODS: MAINTENANCE

construction and normally have a long life. Theydo require replacement from time to time,however, and a few precautions must beobserved in handling them. A CRT must behandled gently to prevent breaking it and toavoid displacing its internal elements. Alwaysplace a CRT face down on cushioning material.If the tube is broken, don't handle the alass withbare hands because the tube's inner surfar, iscoated with a toxic material. Gloves and specialface masks are available to personnel handlingCRTs.

SAFETY WITHPOWER TOOLS

Hazards associated with the use of portableelectric power tools include electric shock,bruises, cuts, falls, particles in the eyes.explosions, and the like. All Sonar Techniciansshould become familiar with the safety practicescontained in .V/1 VSEA Technical Manual,Chapter 9600. Section H. Following are some ofthe general safety precautions you shouldobserve when working with power tools.

1. Ensure that the tools arc grounded inaccordance with articles 60-25 through 60-27and 60-29 of the .V/1 VSE/1 Technical Manual.

2. Avoid. if possible. using spliced cables.3. Carefully inspect the cord and plug. If

the cord is frayed or the plug, appears damaged.replace them.

4. If an extension cord is used, connect thecord of the power tool into the extension cord.then connect the extension cord into the powerreceptacle. When your work is finished, unplugthe extension cord from the power receptacle,then unplug the cord of the power tool.

5. Wear safety goggles for protectionagainst particles that might strike your eyes.

6. Make sure the cables do not present atripping hazard.

GROUNDING TESTEQUIPMENT

Equipment that measures electrical values ofcomponent parts must never assume a groundlevel different from that of the chassis of the

143

148

component. One reason is that measurement ofan electrical value of a component. hy anequipment having its own rzroun d level value,could reflect the difference in potential betweenthe component and the test equipment. Anotherreason is that, if the ground level of the testequipment differs from that of the componentbeing measured, a condition of electrical hazardmay result, and maintenance personnel may beshocked.

Externally powered equipment. such as atube tester, is grounded to the frame of the shipthrough a standard three-wire electrical cord andplug. A firm connection to the power receptacleis all that is needed to ground such equipment sothat it will be safe to the touch. Otherequipment perhaps older or repaired testequipmentmay not be equipped with thethree-wire cord. If it is not so equipped, the testequipment should be grounded, with a separatecable running from its chassis or housing to theframe. Always check to see that the groundconnection is firm and that it is sufficient totake any electrical load supplied to it.

ELECTRIC SHOCK

Electric shock is a jarring, shaking sensation.You may feel as though someone hit you with asledge hammer. Although usually associatedwith high voltage, fatal shocks often are receivedfrom 115 volts or less. If your skin resistance(which varies) becomes low enough, a current of100 milliamperes (.100 ampere) at 115 volts.sustained for only a couple of seconds, issufficient to cause death.

Symptoms and Effects

The victim of an electric shock is very pale:his skin is cold and clammy. His breathing (if heis breathing) is irregular, shallow, and rapid. Hemay sweat profusely, and his eye pupils will bedilated. In some cases he will be unconsciousand have an extremely weak pulse. or no pulse.In severe cases he will have no heartheat. Vitalorgans in the path of the current may hedamaged (usually due to heat) and nervesparalyzed.


Rescue and Treatment

The first thing to do for a victim of electricshock is to remove him from contact with thecircuit. The best method is to open the switch ifyou can chi so without too much delay. If an axis handy and the power cable is accessible, thecable can be cut, assuming that it would taketoo long to find the proper switch. If there areno ready means for cutting the power, use anydry nonconducting material to pull the manfree; a belt, clothing, a piece of line, a woodenstick, or a sound-powered phone cord. Beextremely careful that you don't become avictim yourself.

The treatment to give a shock victimdepends on his conditionwhether he isbreathing or not. The following care isprescribed when the man is breathing.

I. Lay victim on his back, with his headlower than his feet. Loosen the clothing abouthis neck and abdomen so he can breathe freely.Keep him warm, but not hot. SUMMONMEDICAL AID.

2. Keep the man still. Electric shockweakens the heart, and any muscular activity onhis part may cause the heart to stop functioning.

3. Normally, no liquids should be given.Never give stimulants nor sedatives.

4. If the necessary materials are available,apply a small amount of Vasoline to his burns,r.nd cover them with a sterile dressing to preventinfection.

Resuscitation

If the shock victim is not breathing,immediate efforts must be made to revive himeven though he may appear to be dead. (Victimsof severe electric shock sometimes appear asthough rigor mortis has set in.) The effort mustbe continued until medical personnel can takeover or until a competent person declares thevictim to be dead. Speed in beginning artificialrespiration is of the utmost importance. Figure9-2 shows that the victim's best chance ofsurvival depends on beginning resuscitationwithin 5 minutes.

IS 9144

The mouth-to-mouth method of artificialrespiration is preferred. Next in preference is theback-pressure , arin-lift method. Detailedinformation on administering artificialrespiration can be found in Standard First AidTraining Course, NAVEDTRA 10081.Whichever method you use, the importantobjective is to start immediately.

TEST EQUIPMENT

Electrical equipment is designed to operateat certain efficiency levels. Technical instructionbooks, and sheets containing optimumper fo rm a n ce datasuch as voltages andresistancesare prepared for each Navyequipment. The instructions are intended to aidthe technician in maintaining the equipment.

As a Sonar Technicain, you will work withmany different types of test equipment. Thischapter discusses some of the basic equipmentssuch as multimeter, oscilloscope, signalgenerator, frequency counter, and transistortester. If these test equipments do not soundbasic to you, keep in mind that as sonartechnology becomes more complicated, sonarequipment becomes more sophisticated. Itfollows, then, that test equipment used tomaintain the sonar equipment must becomemore sophisticated also.

CURVEPLOTTED

1

SHOWINGAGAINST

START

I

POSSIBIUTYELAPSED

OF RESUSCITATION

I

OF SUCCESSTIME BEFORE

I

NM-wwin.

5 10 15

TIME IN MINUTES

20 5

71.101Figure 9-2.Importance of speed in commencing

artificial respiration.

Chapter 9--TEST EQUIPMENT; TEST METHODS; MAINTENANCE

MULTIMETER

The multimeter is a multipurpose meter thatcan measure resistanees. a.c. and d.c. voltages.and d.c. milliamps. Its versatility and portabilityelminate the need for carrying several meters fortest purposes. The usual precautions must beobserved when making resistance and voltagemeasurements. When measuring d.c. voltage.proper polarity must be observed. The face ofthe instrument has separate graduated scales toindicate the three values that can be measured.Be sure you read the proper scale. Figure 9-3shows the front view of one of the mostcommon multimeters used in today's Navy, theA N/PS M-4 D. Figure 9-4 shows another

4.133Figure 9-3.Multimeter AN/FSM-4D front view.

145150

multimeter used in the Navy today, theelectronic multimeter ME-(1)/U. .,1s a SonarTeelmician. you will become familiar with thesemeters.

OSCILLOSCOPE

The oscilloscope is one of the most valuablepieces of test equipment available to the SonarTechnician. With the oscilloscope you candetermine a signal's frequency, pulse width, andamplitude; measure voltages and phase relations;and observe signal waveforms. The latter use isparticularly helpful since many technicalmanuals include (in their servicing blockdiagrams) waveforms at various test points.

4.133Figure 9-4.Electronic rnultirneter ME-6D/U.


Figure 9-5.Typical oscilloscope, AN/USM-281.

The oscilloscope (fig. 9-5) consists of acathode ray tube, vertical and horizontal beamdeflecting circuits, sawtooth voltage sweepcircuits, and necessary power supplies. Thesignal to be observed (a sine wave, for instance)is applied to the vertical deflection plates. If thatwere the only signal applied, all you would seeon the scope would be a straight. vertical line.To have the sweep conform to the sine wavevoltage on the vertical deflection plates, asawtooth (linearly increasing) voltage is appliedsimultaneously to the horizontal deflectionplates. The result is that the sweep moves acrossthe scope at a uniform rate, following thefluctuations of the signal applied to the verticalplates. When the sawtooth signal reaches itscutoff point, the sweep returns rapidly to itsstarting point to await the next sawtooth signal.The measurement of frequency, calibration, andother special situations requires the use of asynchroscope. which is an oscilloscope withspecial circuits added, such as sweep triggers andmarker generators. The sweep commences onlywhen a signal is received.

SIGNAL GENERATORS

In the maintenance of electronic equipment.it is often necessary to employ standard sources

5 i 146

71.130

of a.c. energy. both audiarequency and radiofrequency. These sources are called signalgenerators. They are used in testing and aligningtransmitters, receivers, and amplifiers: they arealso used when troubleshooting variouselectronic devices and sometimes whenmeasuring frequency.

The principal function of a signal generatoris the production of an alternating voltage of thedesired frequency and amplitude which has then e ess a ry m od u I anon for the te.st ormeasurement concerned. It is very importantthat the amplitude of the generated signal becorrect. In many generators, output meters areincluded in the equipment so that the outputmay be adjusted and maintained at a standardlevel over a wide range of frequencies.

When using the generator, the output testsignal is coupled into the circuit being tested,and its progress through the equipment is tracedby the use of high-impedance indicatinr devicessuch as vacuum tube voltmeters or oscilloscopes.In many sigmil generators, calibrated networksof resistors. called attenuators, arc provided.These are used to regulate the voltage of theoutput signal and also provide correctimpedance values for matching the inputimpedance of the circuit under test. Accurately

Chapter 9TEST EQUIPMENT: 'FEST METHODS: MAINTENANCE

71.131Figure 9-6.Signal Generator.

calibrated attenuators are used since the signalstrength must be regulated to avoid overloadingthe circuit receiving the signal. Figure 9-6 is atypical signal generator.

FREQUENCY COUNTER

The AN/USM-207 11'ig. 9-7) is a portable,solid-state electronic counter fol preciselymeasuring and displaying on an 8-digit numericalreadout the frequency and period of a cyclicelectrical signal, the frequency ratio of twosignals, the time interval between two points onthe same or different signals. and the totalnumber of electrical impulses (totalizing). Thecounter also provides the following types ofoutput signals:

I. Standard signals from 0.1 Ilz to 10 MIltin decade steps derived from a I MI Iz frequencystandard, frequency dividers, and a frequencymultiplier.

2. laput signals divided in frequency hyfactors from 10 to 10 by a frequency divider.

3. Digital data of the measuremen t info u r-li nt binary-coded-decimal form wi t hdecimid point and control signals for operationof printers, data recorders, or control devices.

147

TRANSISTOR TESTER

Laboratory transistor test sets are used inexperimental work to test all characteristics oft Ni nsistors. For main tenance and repair,however, it is not necessary to check all of thetransistor parameters. A check of two or threeperformance characteristics is usually sufficientto determine whether a transistor needs to bereplaced. 'kV() of the most important parametersused for transistor testing are the transistorcurrent gain (Beta) and the collector leakage orreverse current (leo). These are discussed in13asie EhTtronics, Vol. 1, NAVEDTRA I 0087-C.

Semiconductor test set AN/USM-206A9-81 is a rugged field type tester designed to testtransistors and semiconductor diodes. The setwill measure the Beta of a transistor, theresistance appearing at the electrodes and thereverse current of a transistor Or semiconductordiode, a shorted or open condition of a diode,the forward trans-conductance of a field effecttransistor. and the condition of' its ownbatteries.

TEST METHODS

When a piece of sonar equipment breaksdown, it may he your job to locate the trouble


and restore the faulty circuit to its properoperating condi6on. The means by which youfind the faulty component is calledtroubleshooting, which consists of logical restingmethods. Troubleshooting aids includetroubleshooting charts, servicing diagra ins, andvoltage and resistance charts.

Troubleshooting charts list variousequipment malfunctions, the probable cause ofeach. and the necessary corrective action.Servicing diagsams show test points, desiredwaveforms, proper voltages and other re ht edservicing Mformation. Voltage and resistancecharts show the normal voltage and resistancevalues at the pins of connectors and tubesockets.

.Althoud much of the equipment you arerequired to maintain is quite compl,:, the job is

PANEL PROTECTOR

RADIO FREQUENCYOSCILLATOR0-I267/USM-207(HIDDEN)

much easier if broken into successive, logicalst cps. Fignre 9-9 shows a generaltroubleshooting procedure. Steps I through 5are followed in locating the trouble. Steps 6 and7 are carried out in making repairs. Sometimessteps 2,3.4, and 5 may be elinhnated, but neversteps Cu and 7.

TERMINAL DESIGNATIONS

When carrying out your troubleshootingprocedures. you will find that many test pointsarc located on ternnnal boards. Wiring diagrams,which aid you in tracing a circuit from one unitto another, indicate the terminal connections ofeach circuit in each unit. You must understand,therefore. the system used for marking terminalboards and conductors as set forth in Dictionary

ELEc IRONICFREQUENCYCONVERTERCV -1921 USM -207

I PANEL PROT ECTOR

DIGITAL READOUTELECTRONIC COUNTERCP-814/USm -207

POWER LIGHT CONNECTOR

RE CABLE ADAPTERUG-274 B/u

COUNTER COVERCW-BOI/USm-207

CONNECTORADAPTERUG- 273

POWER CABLE

RE CABLE

DIGITAL READOUTELECTRONIC COUNTERAN/USM -207

PRINTED CIRCUITBOARD EXTRACTOR

RFTED PCUI IBCt.RD EiT ENDER

RE CABLE

CONNECTORADAPTERUG -255/U

Figure 9-7.Digital readout electronic counter AN/USM-207.

153 148

CONNECTORADAPTERUG-I035/U

162.7

Chapter 9TEST EQUIPMENT; TEST METHODS; MAINTENANCE

of S tan da rd Terminal Designations fin.Electronic Equiinnent, NAVSEA 900,186.

Terminal Boards

Terminal boards are marked with a three- orfour-digit number preceded by the letters TB.The first one or two digits of the TB numberrepresent the unit number in the equipment.This number is assigned in a logical order. Thelast two digits represent the terminal boardnumber in a unit, starting with 01, 02, 03, etc.Thus, terminal board TB 1003 indicates the 3rd

FE T.BATTtH E-B

BAT.2 00 T-eo

s

us --

BAT. 1. C-E - ROLARITyICO. ICES ZERO

;CESREAD

E B

DIODEIN/CKT

es BETA PN:

-IcEZSEPO-

RANGE

2 5 A P

0 OviER COARSE F INC

Figure 9-8.Semiconductor test setAN/USM-206A.

42-W

TRY TO LOCATE THE TROUBLE BY OBSERVING THECIRCUIT'S FAULTY OPERATION

TRY TO LOCATE THE TROUBLE BY USING EYES AND NOSE

LOCALIZE THE TROUBLE AT THE FAULTY SECTION BYTESTING TECHNIQUES

i2

LOCALIZE THE TROUBLE AT THE FAULTY STAGE BYTESTING TECHNIOUES

LOCALIZE THE TROUBLE AT THE FAULTY C RCUIT OP PARTBY TESTING TECHNIQUES

.....::)

REPLACE OR REPAIR THE DEFECTIVE PART16

5

LEST THE CIRCUIT'S OPERATIONREADJUST THE C,RCUIT )7

12.259Figure 9-9.Troubleshooting procedure.

terminal board in the 10th unit of theequipment.

Terminal Markings

Markings of termimlis on terminal boardsindicate a specific function for the followingcircuits: (1) common primary power circuits, (2)ground terminals, , common servo and synchrocircuits, (4) video circuits. (5) trigiter circuits,and (6) audio circuits. The breakdown of thesecategories into specific functions, with theterminal designation of each, is listed inNAVSEA 900,186. They are called rigidlyassigned designations..

Terminals wlic)se functions do not Call unclerthe categ,ories listed are assigned desiunatic)lis illaccordance with NAVSEA 900,186. Onlyterminals that are connected together externallyhave exactly the sanie designation within anygiven equipment.

Conductor Marking

()II the conchictor lead, at the end near the162.121 point of connection to a ternlinal post, spalJletti

sleeving is usecl as a marKing material andinsulatc)r. The slec\ing is engrawd with indelible

1 5149


ink or branded with identifying numbers andletters by a varitype machine, and slid over theconductor.

The order of marking is such that the firstappearing set of numbers and letters, readingfrom left to right, is the designationcorresponding to the terminal to which that endof the wire is connected. Following the terminaldesignation is a dash and then the number(without TB) of the terminal board to which theother end of the conductor is attached. There isanother dash and the designation of' theparticular terminal to which the other end of thewire is connected.

Figure 9-10 shows how terminal boards,terminals, and conductors arc marked. Thelower portion of the illustration, for example,shows a conductor running from terminal 2A onTB101 to terminal 7B on TB401. The spaghettisleeve on the conductor attached to TB101 ismarked 2A-401-7B, indicating the other endof the conductor is attached to terminal 713 onTB40 I. The sleeve at terminal 713 of T13401 ismarked 7B-101-2A, indicating the other -ridof the conductor is attached to terminal 2A onTBI01. If you must remove a conductor from aterminal, the first set of letters and numbers tellsyou to which terminal it must be reconnected.

TE74111.41.L,N!T A SpGr E

10)

4 ;-x-I

TE; NAL

NO" ;

t lh :C

C5:

Figure 9-10.Conductor and terminal markings.

150

155

Cable Marking

When doing maintenance or repair work,you may have to trace a cable from one sectionof the ship to another, examining the cable fordamage that might be the cause of equipmentbreakdown. Cables are identifieJ by metal tagsthat give information on the cable's use. Tags areattached to the cable as close as practicable toeach terminal connection, on both sides of decksand bulkheads, and at intervals of about 50 feet.Formerly, colored tags were used to classify thenecessity of' the cable, and you may still seesome of them. Red indicates a vital circuit,yellow :1 semivital circuit, and gray a nonvitalcircuit.

'Me cable designation information is acombination of letters and numbers, consistingof a service letter, circuit letters, and cablenumbers. A typical cable designation is RSK3.The service letter ( R ) means the cable supplieselectronic equipment: the circuit letters (SK)denote scanning sonar; and the number (3)means it is the third cable in the scanning sonarcircuit. A complete list of cable designationsmay be found in chapter 9600 of NA VSE4Technical :Vanual.

RESISTORS

A resistor is a device used to limit currentflow. It is of either the fixed or variable type.Resistors are tested with an ohmmeter after theresistor is disconnected from the circuit. Thisaction prevents damage to the meter fromcircuit voltage and ensures that only the resistorbeim; tested gives a reading on the meter. Beforeconducting the test, set the meter to the properscale, touch the ends of the meter test leadstogether, and adjust the meter to obtain a zeroreading.

Fixed Resistors

Fixed resistors may be made of wire, woundori a core and coated with ceramic, or they maylc madc of carbon. They have either axial or:.adial leads, and a wattage rating according tothe amount of heat they dissipate. in general,

Chapter 9TEST EQUIPMENT; TEST METIIODS; MAINTENANCE

carbon resistors are rated 1/2 to 2 watts.Wire-wound resistors usually are rated above 2watts.

Resistance value is indicated by coloredmarkings on the resistor. The standard color

Table 9-1.Standard Color Code for Resistors

ColorSignificantfigure or

number ofzeros

Decimalmultiplier

Resistancetolerance

Black. . Percent ±Brown . . 1

Red 2Orange . . 3Yellow . 4Green . . 5Blue 6Violet . . 7Gray . 8White . . . 9Gold

. 0.1 5;J)*SAver 10(K)*No color. 20(M) *

*Symbol ciesignation alternatp for

A 8 C

axialhads

color.

20.373

code given in table 9-1 is used to interpret theresistor markings. You can easily memorize thecolor code.

A resistor always has three (sometimes four)resistance value indicators. Two methods arcused to color code fixed resistors. In figure 9-11,the axial-lead type is shown to the left; theradial-lead type is shown on the right. Resistancevalue is determined as follows: Color A iodicatesthe first significant figure; color B indicates thesecond significant figure; color C gives themultiplier (number of zeros): and color D is thepercentage of tolerance. If there is no fmirthcolor, the tolerance is 20',;;. Assume that anaxial-lead and a radial-lead resistor each have thefollowing color code marking: Ared, B--green,Corange, and Dgold. Referring to table 9-1,you find that the first significant figure is 2, thesecond significant figure is 5, and the multiplieris 1000 (three zeros). The resistance value is25,000 ohms, or 25K as it sometimes is markedon a schematic diagram. The tolerance is 5%.

A fixed resistor is tested by placing anohmmeter lead on each resistor lead. For ther.2sistor used in our example. a reading of 24K to26K ,vould be acceptable.

ow-power, \vire-wound resistors have axialleads and are color coded similar to the regularaxial-lead resistor, except that band A is doublewidth.

color

C A B

radialkads

Bond A indicates first s gnificant 11; ;re of resistance value in ohms.

Band B indicates second 5 gnificant flgore

Body A

End B

B,nd C indicates decimal multiplier. Band C or dotBand D if any, indicates tolerance in pecent about nominal resistarice

value. if no color appears in this position. tolerarzce is 20%.wS, urn color coded,,,, A

Band D

20.374Figure 9- 11.Color code for axiai-lead and radial-lead fixed resistors.

151


RESISTANCEELEMENT

TERMINAL-1

WIPER

TERMINAL2

TERMINAL 1

W IPE R ( TERMINAL 2 )

71,94F igu re 91 2. R heostat.

Variable Resistors

Variable resistors are or 1.Vt.k) general types:may be rheostats or potentiometers.

A rheostat normally is used to adjust thecurrent in a circuit without opening the circuit.Some rheostats. however, arc so construetedthat the circuit inay be opened also. In general, arheostat has two terminals. One terminal isconnected to one end of the resistance element:the other, to the sliding contact. .\s seen infigure Q-12. the resistance element is circular inshape and is made of resistance wire woundaround an insulating form that usually is of aceramic material. The resistance is decreased byrotating the wiper toward terminal 1.

"fo test a rheostat. you first must disconnectit from circuit. An ohmmeter is used tomeasure ti. resistance between terminals 1 and2 (refer to 1.H. 9-12). with the wiper rotated allthe way to terminal 2. This action gives totalresistance. Moving the wiper slowly back towardterminal 1 shows an ever-decreasing resistanceuntil a reading of zero is obtained. If a rcadh-,gof maximum shows on the meter during thkphase of rotating the wiper toward terminal 1. itmeans the %viper is not making proper contact atthat point.

152

5%7

WIPER RESISTANCEELEMENT

TERMINAL I

TERMINAL 1

TERMINAL 2

TERMINAL 3

WIPER (TERMINAL 3)

TERMINAL 21

33.75F igure 9-13. Potentiorneter.

The potentiometer (often called a "pot") isa control instrument used for varying theamount of voltage applied to an electricaldevice. The term "potentiometer" customarilyrefers to any adjustable resistor having threeterminals, two of which are connected to theends of the resistance element and the third tothe wiper contact. The potentiometer isillustrated in figure 9-13. By positioning thesliding contact, any desired voltage within therange of the potentiometer may be selected andused where needed. As a rule. potentiometersarc constructed to carry smaller currents thanrheostats.

Potentiometers are measured in much thes.une way as rheostats. When disconnected fromthe circuit, they may be tested with anohmmeter by measuring for total resistancebetween terminal- 1 and 2. Applying one lead toterminal 3 and the other Icad to either terminalI or 2 and moving the wiper results in asmoothly increasing or decreasing variation inresist:nice.


CAPACITORS

Many capacitors have their value printed onthem, but some types use a color code system toindicate their value. The color code used is thesame as that used for resistors, but the methodsof marking the capacitors vary greatly. Themethod used for fixed mica capacitors is shownin figure 9-14.

A black dot in the upper left corner signifiesthat the capacitor has a mica dielectric. Thecenter dot in the upper row indicates the firstsignificant figure, and the upper right dotindicates the second significant figure of thecapacitance value in micromicrofaradsThe right dot in the lower row indicates thedecimal multiplier that determines the numberof zeros to be added to the right of the twosignificant figures. The center dot (lower row)specifies the tolerance, which is the possibledeviation of the actual capacitor value from thatgiven by its dot markings. The left (lot on thelower row deals with temperature coefficientsand applications.

By way of explanation, a capacitor withLIpper-row dots colored black, red, and ilreen"reading from left to right, :).ccording to theiirectional indicator) would mean a mica;apacitor with the significant figures 2 and 5.

The lower row of dots (reading from right toleft) are brown, red, and red. The brown dotrequires the addition of one zero to the value25, giving the result as 250 ppf. The red centerdot indicates that the actual capacitor value maybc p-eater or smaller than the 250 ppf by plus orminus 2 percent. The left red dot means it is abypass or silver mica capacitor. Some micacapacitors have only three dots, indicating thefirst and second significant figures and themultiplier. Their tolerance is 20 percent, andthey have a 500-volt rating. Try reading some ofthe values of the mica capacitors you see inelectronic equipment when they are exposed toview. Learning to read capacitor values is amatter of practice, much like reading resistorvahies.

Electrolytic Capacitors

Electrolytic capacitors are used where a largeamount of capacitance is required. As the nameimplies, electrolytic capacitors contain anelectrolyte. This electrolyte can be in the formof either a liquid (wet electrolytic capacitor) ora paste (dry electrolytic capacitor). Wetelectrolytic capacitors are no longer in popularuse due to the care needed to prevent spilling ofthe electrolyte.

Dry electrolytic capacitors consist essentiallyof two metal plates between which is placed the

COLOR

CAPACITANCE

TOLERANCE CHARACTER-ISTIC

BLACK DOT IDENTIFIESDIRECTIONALMICA CAPACITORINDICATORS

SIGNIFICANTFIGURE

DECIMALMULTIPLIER SIGNIFICANT

FIGURES OFCAPACITANCE2NDIN f

DECIMAL MULTIPLIER

PARTS- MILLION,C)

MILLION, C)MILLION,C)

C)

BLACKBROWNREDORANGEYELLOWGREENBLUEVIOLETGRAYWHITEGOLDSILVER

0

1

2

3

4

5

6

7

8

9

1

10

100

1,000

0.10.01

20 PERCENT

2 PERCENT

5 PERCENT10 PERCENT

.

A

B

C

D

E

F

G

CHARACTERISTIC

CAPACITANCE TOLERANCE

CHARACT ERISTICSA - ORDINARY MICA BYPASSB SAME AS A-LOW LOSS CASEC - BYPASS OR SILVER MICA ( 2000 - SILVER MICA ( * SOO PARTS MILLION-C)E - SILVER MICA (0 TO .100 PARTSF - SILVER MICA (0 TO 50 PARTSG - SILVER MICA (0 TO -50 PARTSMILLION.

20.376Figure 9-14.Color code for fixed mica capacitors.

153

158


ALUMINUM FOIL

PAPER ANDELECTROLYTE

PAPER

OXIDE FILM

236.216Figure 9-15.Construction of an electrolytic

capacitor.

electrolyte. In most cases the capacitor is housedin a cylindrical aluminum container which actsas the negative terminal of the capacitor (fig.9-15). The positive terminal (or terminals if thecapacitor is of the multisection type) is in theform of a lug on the bottom end of thecontainer. The size and voltage rating of thecapacitor is generally printed on the side of theail!rninum case.

Capacitance measurements are usuallyaccomplished by either a bridge-type or areactance-type capacitance meter. For accuracy,the former equipment is comparable to theresistance bridge, and the latter instrument iscomparable to the ohmmeter. Capacitancetolerances vary even more widely than resistancetolerances, being dependent upon the type ofcapacitor, the value of the capacitance, and thevoltage rating. The results of capacitance testsmust be evaluated to determine whether aparticular capacitor will fulfill the requirementsof the circuit in which it is used. The powerfactor of a capacitor is important because it is anindication of the various losses attributable tothe dielectric, such as current leakage and

154

1 5 9

dielectrical absorption. Current leakage is ofconsiderable importance, especially inelectrolytic capacitors. The measurement ofcapacitance is very simple; however, you mustmake the important decision of whether toreject or continue to use a certain capacitor alterit has been tested. A common test equipmentused for testing capacitors, the -Z.M-11A/U, isshown in figure 9-16.

MAINTENANCE

Any piece of machinery or precisionequipment requires some type of care to keep itrunning efficiently. Proper upkeep of anautomobile, for example, includes charwing theoil at certain mileage intervals. The windshieldmust be kept clean; headlights and brakes mustbe adjusted now and then; and an occasionalengine tuneup must be obtained. Sonarequipment also requires periodic upkeep, but inmore detail and at more regular intervals thandoes an automobile. Aboard your ship orsubmarine, you will assist in carrying outscheduled maintenance on the equipment towhich you aie assigned.

Various publications are available to assistyou in carrying out a maintenancc program. Themanufacturer's technical manual for each pieceof equipment is an invaluable aid. These booksdescribe the components or the equipment,operating standards, and required maintenance.Other publications include the NAVSEATechnical Manual and Electronic InformationBulletins (EIBs).

TYPES OF MAINTENANCE

Maintenance is divided into three categories,according to complexity and purpose. The threetypes of maintenance are operational,preventive, and corrective.

At first glance it may seem that preventiveand operational maintenance are synonymous,but there is a good deal pf difference betweenthe two. Operational maintenance is confined totasks that can be performed by an operatorwhile he is on watch, and usually is furtherconfined to one component, such as the sonar

Chapter 9 --TEST EQUIPMENT; TEST METHODS; MAINTENANCE

FUNCTIONSWITCH

BALANCEINDICATOR

VOLTAGE CONTROL

C CP465000M

10000

CAPDUAL

CAPOUAL

FUNCTIONtoOSCILLATOR

ADJUST

RANGE

CALIBRATEINS TEST

METER OSCILLATOR

MULTIPLY RANGESETTING

BY

QUALITYTEST

POWER

1.68Figure 9-16.Capacitance-inductance-resistance bridge ZM-11A/U.

onsole. Preventive maintenance is a systematic)rogram covering the entire sonar system and.equires several men to carry out.

The Naiy's operational and preventivenaintenance program formerly was called)0MSEE. Ships and stations today, however.itilize a program known as the Standard Navy4aintenance and Material Management Systc:n.nore familiarly called the 3-M System, which

be discussed later in the chapter.

Operational Maintenance

Operational maintenance is the elementaryupkeep performed by the operator to keep hisequipment in good operating condition. Itconsists mainly or proper operation of theequipment, such as starting, stopping,calibrating, and manipulating controls in theprescribed manner. At times, operationalmaintenance may also include inspection,

1 55

130

INTRODUCTION To SONAR

cleaning, and lubrication of equipment, andreplacement of minor parts, such as indicatorlamps.

Preventive Maintenance

Preventive maintenance is intende(l toforestall equipment failure. Besides testing,discussed previously, this chapter comprisesinspection, cleaning, and lubrication. If' no highdegree of' technical skill or internal alignment isrequired, it also includes minor adjustments andreplacement of minor deteriorated parts which,if left uncorrected, might lead to equipmentmalfunction or part failure.

INSPECTION.All electronic equipmentshould be inspected daily for such defects asbroken meter glasses, loose control knobs,burned-out indicator lights, loose cableconnections, and the many small items that maybe checked with or without the equipmentactually being energized. On units that utilizeventilation for cooling, the intake and outletareas should be inspected to see that they arefree of obstructions.

Many items should be inspected daily,weekly, and monthly to help maintain theequipment in serviceable condition. In sonicinstances these routine checks include electricalmeasurements to cheek individual units formalfunctioning circuitry. Technical manualsfurnished by the manufacturer include lists ofchecks to be conducted at regular intervals andthe desired reading or measurement required forpeak performance of the specific equipment.

CLEANING.Cleaning is an important partof preventive maintenance. External surfaces ofelectronic units and the surrounding spacesshould be cleaned daily. This daily routinereduces the amount of dirt and dust that entersthe equipment through circulating air blowerintakes. Some dust and dirt naturally will worktheir way in: hence, the interiors of units shouldbe cleaned carefully, at least once a week, with a,r)ft cloth. If possible, a vacuum cleaner should

used. Avoid using blowers, bellows, ora.aning m)lvents, because they tend to push orwash dirt into inaccessible corners. Air filtersshould be cleaned at least once a week. Climate

156

and operating conditions may required cleanimmore often. Overheating due to clogged airfilters often is a prime cause of equipmentfailure. Neglect in cleaning filters is, thereforeinexcusable.

Gene rat ors must be given a carefulcleanliness check while the equipment is

inoperative. Brushes and commutators should becleaned frequently. Be careful not to blow orbrush carbon dust and other foreign matter intothe windings or bearings. When cleaninggenerators, ensure that the brushes slide freely intheir holder and exert proper pressure on theslipring or commutator surface.

LUBRICATIONFlectronic gear has manypartssuch as motors, hoists, gears, andspringsthat require regular lubrication. Themanufacturer's technical manual should befollowed to ascertain where, how often, andhow much lubrication is needed. Use cautionwhen lubricating the parts of' any piece ofequipment, and follow the instructions in thebook pertaining to the individual type ofequipment. Too much lubrication can be just asharmful as too little.

Corrective Maintenance

Corrective maintenance, another name forrepair, is necessary only after equipment failure.Co rr cc five main tenance usually calls forreplacement of internal parts or alignment ofelectronic components requiring technicallytrained personnel. Some of this work isperformed by operating personnel while assistingthe technician. As you advance in rate, you willperform more highly technical maintenance onyour Own.

MAINTENANCE ANDMATERIAL MANAGEMENT SYSTEM

Reliability of electronic equ:pment dependson the quality of the preventive and operationalmaintenance received by the equipment. Asequipment becomes more complex, themaintenance problem becomes ever greater.

In the past, many programs evolved thatoften were uncoordinated and sometimes


unworkable. The lack of well-trainedtechnicians, together with the large number ofreports required by some programs, seriouslyhampered the maintenance effort. Overloadedsystems commands, moreover, could nutproperly correlate the mass of information inthe reports.

To alleviate these conditions, the StandardNavy Maintenance and Material Management

M) System wcs implemented. The 3-MS),stem replaces all othec maintenance programs.It prescribes standard maintenance procedures,provides .a feedback report system that enablesthe progxam to be updated,'and corrects errorsand deficiencies.

Procedures for managing and reporting themaintenance progxam are contained in Ship'sMaintenance and Alaterial Management ($-M)Manual, OPNAVINST 4790.4.

Basic elements of the 3-M System are thePlanned Maintenance Subsystem (PMS) and theMaintenance Data Collection Subsystem(MDCS). The PMS provides a uniform system ofplanned preventive maintenance. The MDCSprovides a means of collectim; necessart;maintenance and supply data, in a form suitablefor machine processing. A man-hour accountingsystem also is aboard repair ships andtenders in conjun,:tion with the MDCS. As athird class petty officer, you will be concernedwith the Planned Maintenance Subsystem andcertain portions of the Maintenance DataCollection Subsysten The degree of equipmentreadiness, effectiveness. :Ind 'ability dependson how well perfnrm the requiredmaintenance.

Planned Maintenance Subsystem

Preventive mainienance, when properlycarried out, reduces casualties and associatedcosts and equipment downtime, required formajor repairs. The PMS is designed to simplifymaintenance procedures (insofar as possible) bydefining the maintenance required, schedulingits performance, describing the tools andmethods to be used, and providing for thede tec ti on and prevention of impendingcasualties.

162 157

In establishing minimum equipmentmain tenance requirements, the NAVSEATechnical Manual, manufacturers' technicalmanuals, and other applicable publications arereviewed critically. If planned maintenancerequirements are found to be unrealistic orunclear, they are modified or completely revisedbefore incorporation into the PMS.

It is possible that the planned maintenancespecified in the PMS may differ from thatprescribed in other documents. Should somevariance become apparent, remember that,insofar as preventive maintenance is concerned,the PMS supersedes and takes precedence overex' ing requirements set forth in variouste,.anical publications.

PLANNED MAINTENANCE SUBSYSTEMMANUAL.A master Planned Maintenance'Subsystem Manual (OPNAV 43P1) is tailored toeach ship. It contains minimum plannedmaintenance requirements for each maintainablecomponent installed in that particular ship.Normally, appropriate sections (engineering,electronics, weapons, etc.) of the master manualare kept in the office of the departmentconcerned. Respective sections are used byelonartment heads in planning and scheduling all

itenance requirements in their departments.-The departmental PMS manual contains a

section for each division or maintenance groupwithin a department. Each divisional sectionincludes a table of contents and a maintenanceindex pan (MIP) for each system, sub3ystem, orcomponent. Applicable portions of the PMSmanual are kept in the working space for theequipment to which they pertain. Theseportions serve as a ready reference to therequired planned maintenance. Each MIPcontains a brief description of maintenancerequirements and the frequency with which theyare to be effected.

The frequency code is: Ddaily. Wweekly,M monthly, Qquarterly, Ssemiannually,.Aannually. Coverhaul cycle, and Rsituationrequirement. Frequency codes for daily, weekly,monthly. quarterly, semiannual, and annualplanned maintenance actions areself-explanatory. Code C designates certainplanned maintenance actions performed in a


AMIN:MEW51!;11 I N.4 1111 COSPI'ONI NI

Main Circulating Pump

11111111W:1. IIIJIILICAIIONS DAILl Juno 19 (I

C.^0 I ,11'. I lit NANCI 5115)5 SM. 411111 MU & TO IN w))1C). Ill( I Ill.1.0,5151). III IN

syscomlimncCONTROLNO. MAINTENANCE REQUIREMENT

84 5078 W 1. Sample and inspect lube oil.Lubricate the speed limitinggovernor.Turn pump several revolutions byhand; if steam is available,turn by steam.

66 5075 m 1. Test speed limiting governor.

25 7598 0 1. Clean pump and renew oil.'. Clean lube oil filter.

68 P778 Q Test spring-loaded cxl, ,ius t valveby steam.

A4 4830 0 1. Inspect reduction gears.

65 4075 0 1. Renew stuffing box packing.

84 50R2 A 1. Souud and tighten foundationbolts.

2. Inspect and clean steam strainer.

85 5083 C 1. Inspect internal water lubricatedbearing and journal for condi-tion. Measure bearing and pro-peller clearances.

95 D045 C 1. Inspect carbon packing for wear.

16 5510 C 1. Clean, 11-1!;pect, and preserve

exterior of turbine casing.

MAINEF ANCE INDEX PAGEOPNAV FORM 4/00 3 IAI (REV 4 II)

DICITYCODE

W-I

SKILL MANLEVEL HOURS

RELATEDMAINTE

RM3 0.5 N011e

1-I-1 9M1 0.2 Non,'

RN 0.2

0- 1 2-121 I 0 . 1 NoneRN 1.5

Q-2 2-12-12 0.2FN 0.2

0-1 mrn 1) .5 None

0-4 MM) 1.0 None

5-1 92-13 1.0 None

C-1 2-011 12.0 Q..4

21'N 24.0

(- 1-012 2.0 N0nuRN 2.0

I C-3 2-12-12 1.0 C-2FN 1.0

SYSCOM AWCONTHOLNUMBERF-5/76-68

98.176Figure 9-17.Example of a hull mechanical or electrical equipment MIP.

158

Chapter 9---TEST EQUIPMENT; TEST MIM-IODS; MAINTENANCE

specified quarter (i.e., once) (luring theoperational cycle between shipyard overhauls.Code R identifies planned maintenance actionsthat are to be performed before gettingunderway, after a specified number of hours ofoperation, or to meet other requirements thatarise only during specific situations.

Figure 9-17 shows a typical maintenanceindex page. Information entered on the MIPincludes the system or component, a shortdescription of each maintenance requirement,maintenance frequency code plus a consecutivenumber starting with numeral 1 for eachfrequency code assigned, rate(s) recommendedto perform the maintenance, average timerequired to perform the maintenance, andrelated maintenance requirements. Relatedmaintenance represents additional plannedmaintenance that can be cornpleted before, inconjunction with, or immediately after ascheduled maintenance.

Shipboard application of the PMS variesslightly from one ship to another. Clarification isrequired, therefore, of information found onMIPs regarding rates recommended to performmaintenance and the average time required forthe task. Actually, maintenance tasks areperformed by personnel available and capable,regardless of the rate listed on the MW. As listedon the MIP, average time required does notconsider time required to assemble necessarytools and materials, to obtain permission tosecure equipment, nor to clean the area and putaway tools upon conclusion of a task. Alwaysremember, however, that no maintenance iscomplete until all tools and equipment are putaway and the area is cleaned.

SCHEDULING PLANNEDMAINTENANCE.For each division ormaintenance group, a cycle schedule thatprovides a visual display of planned maintenancerequirements (based on the operational cycle ofthe ship between shipyard overhauls) isexhibited in the departmental office.Information supplied on a cycle schedule forany particular division or maintenance groupincludes the MIP number from the PMS manual.a listing of all equipment within that particulargroup for which planned maintenance is

159

required, and the specific quarter in which thesemiannual, annual, and overhaul cycle plannedmaintenance actions are to be performed. Acycle schedule also lists quarterly and situationrequirement planned maintenance actions thatmust be scheduled, as well as monthly plannedmaintenance requirement.

Cycle schedules are utilized by departmentheads, in conjunction with their division officersand leading petty officers, to prepare quarterlyplanned maintenance schedules. A quarterlyschedule is displayed in a holder, known as themaintenance control board, adjacent to thecycle schedule to which it pertains. A quarterlyschedule gives a visual display of the ship'se m ploy men t s c hedule and the plannedmaintenance to be performed during thatparticular quarter. A quarterly schedule has 13columns, 1 for each week in the quarter, forscheduling maintenance throughout a 3-monthperiod.

At the end of each week, the leading pettyofficer of a division or maintenance groupupdates the quarterly schedule by crossing out(with an X) the preventive maintenanceperformed. If a planned maintenance action isnot completed during the week it is scheduled,the leading petty officer circles the action on thequarterly schedule. Uncompleted maintenance isthen rescheduled for another week within thesame quarter.

At the close of each quarter, the applicablequarterly schedule is removed from its holderand retained on board as a record of the plannedmaintenance completed. This record may bediscarded at the beginning of the second quarteralter the next shipyard overhaul.

A quarterly schedule also is used by aleading petty officer to arrange a weeklyplanned maintenance schedule for posting in anappropriate workspace. The weekly schedule ofplanned maintenance should not he consideredas the total of all work for a given week. Thisweekly work covers only scheduled plannedmaintenance and is in addition to other routinework, upkeep, and corrective maintenance to beaccomplished. The weekly schedule provides alist of components in the working area,appropriate page number of the PMS manual,


and spaces for the leading PO to use in assigningpla nned ma intenance tasks to specifiedpersonnel. Daily and weekly plannedmaintenance actions are preprinted on theforms, and the other maintenance actions arewritten in by the leading PO as required. Whenthe leading PO is assured that a maintenancetask is completed, he crosses out themaintenance requirement number on the weeklyschedule. If for some reason a task cannot becompleted on the day scheduled, the leadingpetty officer circles the maintenancerequirement number and reschedules it foranother day. Current status of scheduledmaintenance is readily available by looking atthe weekly scheJule.

MAINTENANCE REQUIREMENTCA RD. A maintenance requirement card(MRC) is a 5 by 8 inch card on which a plannedmaintenance task is defined sufficiently toenable assigned personnel to perform the task.(See fig. 9-18.) A master set of MRCs ismaintained in the departmental office. Cardsapplicable to the equipment for which SonarTechnicial:. are responsible are maintained inthe workspace. If a card in the workspacebecomes lost or mutilated, a new card may bemade from the master set and can be used untila feedback report is sent in and a new cardobtain 1.

A maintenance requirement card is one ofthe principal components of the PMS withwhich Sonar Technicians are concerned.Suppose that on a Monday morning anindividual looks at the weekly schedule andfinds that he is assigned the maintenance actionidentified as M-14. The weekly scheduleindicates that this particular maintenance actionis listed on page S0-9 of the PMS manual. TheMRC that describes the task assigned isidentified by the number combination S0-9,M-14 in the upper right corner. In preparationfor performing the assigned task, MRC numberS0-9, M-14 is selected from the set of cards inthe workspace. An MRC identifies eachcomponent; gives the rate and time required top rform the maintenance; gives a briefdescription of maintenance required; cites safetyprecautions to be observed: and lists tools, parts,and materials rwded to accomplish the task.

5,51,S1

t

41

.tant14,1.41, In IhrIll' 4411i

I

11 Pan, f/010.1., 11,1 itIl.

I LArt

r, LOVE

NAT,

Amommsenoseil

98.176Figure 9-18.--MRC card.

This information is given to enable personnel tobe completely ready to perform all prescribedmain tenance before actually working onequipment authorized. The procedure described

MRC is standardized and is the bestkvov.1 method of performing that particulartask. For purposes of time conservation, anyrelated maintenance requirement included onthe MRC should be done at the same time or inconjunction with the assined task.

FEEDBACK REPORT.A PMS feedbackreport, OPNAV FORM 4790/7B (fig. 9-19) is

160

165


Cq,'CM, OPSAt .1 PIO

SEE INSTRUCTIONS ON BACK OF GREEN PAGEFR-OM ISH-IP NAME AND HULL NUMBE RI

011BROOKE (DEG-1)

Ll August 1972

NAVY MAINTENANCE MANAGEMENT TIELD OFFICE IC...7w,, Al

ETYPE CoMMANDER IC.I.ge BI

SUBJFET, PL.Z;NED MAINTENANCE SUBSYSTEM FEEDBACK REPORTS,c00 Sub SS`,c (.0,ontlM1k, C.. A, ,t) MOO

Compensating SystemCO,r.OL ...+C

F -37/1 -CB

CATEGINiv A

1 08 8776 (1

DESCRIPTIOlyrOFc.STECOlIV

..11PIMRCIEGI. REPLACEMENT TECHNICAL

Ej EQUIPMENT ADDITION 0 TYCOM ASSISTANCE

0 EQUIPMENT DELETION OTHER ISPec.NI

0 CHANGE TO EQUIPMENT

REMARKS

Before testing setting on relief valve, ye needcalibration steps for Leslie-liatic controller. Thisstep in procedure is not contained on the present HRC.11,s ship does not have any pub or Tecn Manual as tothe steps that should be taken in checking the Leslie-Katic controller fur accuracy.

. 671 E,,AnTsAi,T "CAC

i-I. A.;

TYCOM 2CoNcuoE1J ..1:ST'O-Z 0"

CC

kr jj1.1.-e-eL /r1 7 2-OPNAI., AlTO 71316 lE ACTION COPY POC,C -

98.176Figure 9-19.PMS feedback report.

desigied for reporting any discrepancies orsuggested improvements in the PMS as installedaboard ship. This report is to be filled out by theman who discovers a dis.7repancy or suggests animprovement. It is sig1e,_1 by a designee of thecommanding officer and is mailed via the typecommander to an appropriate field office listedon the reverse side of the originator's copy ofthe form.

When submitting a feedback report, be sorcit is idled OW completely and legibly. If the

161

purpose of submitting a feedback report is tocorrect a discrepancy, for example, on amaintenance requirement card, be sure thediscrepancy is clearly identified and therecommended change is correct and readilyunderstood. Instructions for preparing thereport are listed on the back of the form.

Maintenance DataCollection Subsystem

The Maintenance Data Collection Subsystemis intended to provide a means of recordingmaintenance actions in substantial detail so thata variety of information may be collectedconcerning maintenance actions andperformance of equipment. In addition to theforegoing information, MDCS furnishes data oninitial discovery of a malfunction, howequipment malfunctioned, how many man-hourswere expended on its repair, equipmentinvolved, repair parts and materials used, delaysincurred, reasons for delay, and the technicalspeciality or work center that performed themaintenance.

In recording maintenance actions, codesmust be used to convert information to alanguage that can be read by automatic dataprocessing machines. Codes are listed in theequipment identification code (EIC) manual.Third class petty officers are required to preparenumerous maintenance forms, using appropriateEICs. These forms are sent to a data processingcenter where coded information is punched ontocards, which then are machine processed .toproduce various reports for use in maintenanceand material management.

Reports coming from the autoMatic dataprocessing machines are accurate and useful onlyif information is entered clearly and correctly onmaintenance forms. All codes supplied on theforms must therefore be accurate and clearlywritten.

The MDCS requires that coded entries bemade on OPNAV Form 4790/2k, Ship'sMaintenance Action Form. Detailed descriptionsand instructions for this form are contained inVolum..' II of the 3-NI manual, OPNAVINST4791. -7, .

CHAPTER 10

SECURITY

The security of the United States in generaland of naval operations in particular dependsgreatly upon the success attained in safeguardingclassified information. It is of paramountimportance that everyone responsible for thesecurity of classified information preserve abalanced and comrnonsense outlook toward thesubject.

As a Sonar Technician you will hear a greatdeal about the security of classified materialbecause you will have access to and utilizeclassified information every day. For this reason,all a c tivities brief newly arrived SonarTechnicians in security and require them to signa statement attesting to the fact that they havereceived the briefing and understand thecontent. Further, as a part of each command'ssecurity program, you will be required to readand indicate your understanding of several oft he most important national laws andregulations related to security.

Ma intaining the security of classifiedmaterial, however, requires more than a briefing,a regulation, or a law. Security will only be aseffective as you make it; there is no one towhom you can transfer your responsibility forprotecting this information. The security ofclassified material is not an extra job: it is a basicpart of your assignment just as is operatingclectronic equipment. You must be securityconscious to the point that you automaticallyexercise proper discretion in the discharge ofyour duties and do not think of security ofinformation as something separate and apartfrom other matters. In this way, security ofclassified information becomes a natural elemento: every task and not an additionally imposedburden.

Security is more than a matter of beingcareful: it requires both study and practice.

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Thorough understanding of this chapter will notprovide full knowledge of all the finer pointsconcerning security, but it will provide you witha good fundamental background upon whichsecurity is built.

PURPOSE OFTHE SECURITY PROGRAM

The security program deals basically withthe safeguarding of' information that could, inthe hands of unauthorized personnel, be used tothe detriment of the United States. Classifiedinformation may be compromised throughcareless talk, improper handling, and variousother ways. Some of the ways in which militarypersonnel may accidentally give away vitalinformation are discussed in Basic MilitaryRequirements, NAVEDTRA 10054 (currentseries).

'3ECURITY PRINCIPLES

The Department of Defense security formulais based on the premise of circulation control;i.e., the contro1 of dissemination of classifiedinformation. According to this policy,knowledge or possession of classified defenseinformation is permitted only to persons whoseofficial duties require access in the interest ofpromoting national defense and only if they aredetermined to be trustworthy.

DEFINITIONS

The following definitions are taken fromDepartment of the Nary Infnrmation SecurityProgram Regulation, OPNA VINST 5510.1 E.

Chapter 10SECURITY

ACCESS

The ability and opportunity to obtainknowledge or possession of classifiedinformation.

ALIEN

Any person not a citizen or a national of theUnited States.

CLASSIFICATION

The determination that official informationrequires, in the interest of national security, aspecific degree of protection againstunauthorized disclosure, coupled with adesignation signifying that such a determinationhas been made.

CLASSIFICATION GUIDE

An instruction indicating the classification,downgrading, and declassification guidance thatmay be assigned to subjects within a specificarea of defense activity.

CLASSIFIED INFORMATION

Official information which has beendetermined to require, in the interest of nationalsec uri t y , protection against unauthorizeddisclosure and which has been so designated.

CLASSIFIED MATERIAL

Any matter, document, product, orsubstance on or in which classified informationis recorded or embodied.

CLASSIFIER

An individual who does either of thefollowing:

1. Determine that official information, notknown by him to be already classified, currentlyrequires, in the interest of national security, aspecific degree of protection againstu na utho rized disclosure and, having theauthority to do so, designates that official

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information as Top Secret, Secret, orConfidential.

2. Determines that official information is insubstance the same as information known byhim to be already classified by the governmentas Top Secret, Secret, or Confidential anddesignates it accord: n

CLEARANCE

An administrative determination bycompetent authority that an individual is eligiblefor access to classifiA information of a specificclassification cat..)1y.

COW TENT AUTHORITYCOMMANDING OFFICER

For the purposes of this chapter, the terms"competent authority" and "commandingofficer" are synonymous. These terms areintended to include "commander," "officer incharge," "naval representative," "director,""inspector," and any other title assigned to anindividual, military or civilian, who, throughcommand status, position, or administrativejurisdiction, is qualified to assume responsibilityand to render a decision with regard to a specificquestion under consideration.

COMPROMISE

The known or suspected exposure ofclassified information or material to anunauthorized person.

Compromise, when evaluated for reportingpurposes, shall be described as follows:

I. Confirmedcompromise is consideredconfirmed when conclusive evidence exists thatclassified material was compromised.

2. Suspectedcompromise is suspectedwhen evidence exists beyond a reasonabledoubt that classified material has beensubjected to compromise.

3. Re mote co mpromise is consideredremote when, after the conduct of an initialinquiry, there exists strong evidence indicatingthere was minimal risk of the material gettinginto the public domain or minimal risk that the


circumstances of the unauthorized disclosurecould reasonably be expected to damage thenational security.

CUSTODIAN

An individual who has possession of or isotherwise charged with the responsibility forsafeguarding and accounting for classifiedinformation.

DECLASSIFICATION

The determination that classifiedinformation no longer requires, in the interest ofnational security, any degree of protectionagainst unauthorized disclosure, coupled with aremoval or cancellation of the classificationdesignation.

DOCUMENT

Any recorded information, regardless of itsphysical form or characteristics, including,without limitation, written or printed material;data processing cards and tapes; maps andcharts; paintings; drawings; engravings; sketches;working notes and papers; reproductions of suchthings by any means or process; and sounci.voice, or electronic recordings in any form.

DOWNGRADE

To determine that classified informationrequires, in the interest of national security, alower degree of protection against unauthorizeddisclosure than currently provided, coupled witha changing of the classification designation toreflect such lower degree.

FORMERLY RESTRICTED DATA

Information removed from the RestrictedData category upon determination jointly by theAtomic Energy Commission and Department ofDefense that such information relates primarilyto the military utilization of atomic weaponsand that such information can be adequatelysafeguarded as classified defense information.Such information is, however, treated the sameas Restricted Data for purposes of foreigndissemination.

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MARKING

Thy physical act of indicating on classifiedmaterial the assigned classification, changes inclassification, downgrading and declassificationinstructions, and any limitations on the usethereof.

NEED m KNOW

The necessity for access to, or knowledge orpossession of classified information to carry outofficial military or other governmental duties.Responsibility for determining whether aperson's duties require that he possess or haveaccess to classified information and whether heis authorized to receive it rests upon thepossessor of the classified information and notupon the prospective recipient.

RESTRICTED DATA

All data (information) covering (1) design,manufacture, or utilization of atomic weapons;(2) the production of special nuclear material; or(3) the use of special nuclear material in theproduction of energy, but not to include datadeclassified or removed from the RestrictedData category pursuant to Section 142 of theAtomic Energy Act. (See Section I 1 y, AtomicEnergy. Act of 1954, as amended, and"Formerly Restricted Data.")

SECURITY

A protected condition of classifiedinformation which prevents unauthorizedpersons from obtaining information of direct orindirect military value. This condition resultsfrom the establishment and maintenance ofprotective measures which ensure a state ofinviolability from hostile acts or influence.

UPGRADE

To determine that certain classifiedinformation requires, in the interest of nationalsecurity, a higher degree of protection againstunauthorized disclosure than currently provided,coupled with a changing of the classificationdesignation to reflect such higher degree.

Chapter 10SECURITY

CLASSIFICATION ATEGORIES

Official information_11:Lt requires protectionin the interest of national defense is placed ir.toone of three categories: Top Secret, Secret, orConfidential. Following are examples anddefin: Lions or each category.

TOP SECRET

The Top Secret classification is limited todefense information or material requiring thehighest degree of protect:on. It is applied onlyto information or material the defense aspec.t ofwhich is paramount, and the unauthorizeddisclosure of which could reasonably beexpected to cause EXCEPTIONALLY GRAVEDAMAGE to the Nation, such as-

1. A war, an armed attack against theUnited States or her allies, or a break indiplomatic relations that would affect thedefense of the United States.

2. The unauthorized disclosure of militaryor defense plans, intelligence operations, orscientific or technolo0.cal developments vital tothe national defense.

SECRET

The Secret classification is limited to defenseinformation or material the unauthorizeddisclosure of which could reasonably beexpected to cause SERIOUS DAMAGE to theNation, such as

I. Jeopardizing the internationalrelationships of the United States.

2. Endangering the effectiveness of a

program or policy of vital importance to thenational defense.

3. Compromising important military ordefense plans, or scientific developmentsimportant to national defense.

4. Revealing important intelligenceoperations.

CONFIDENTIAL

unautho rized disclosure of which couldreasonably be expected to cause damage to theNational security, such as-

1. Operational and battle reports thatcontain information of value to the enemy.

2. Intelligence reports.3. Military radiofrequency and call sign

allocations that are especially important or arechanged frequently for security reasons.

4. De v i ces and material relating tocommunication security.

5. Information that reveals strength of ourland, air, or naval forces in the United States andoverseas areas, identity or composition of units,or detailed information relatimz to theirequipment.

6. Documents and manuals containingtechni ca 1 information used for training,maintenance, and inspection of classifiedmunitions of war.

7. Operational and tactical doctrine.8. Research, development, production, and

procurement of munitions of war.9. Mobilization plans.

10. Personnel security investigations Lind

other investigations, such as courts of inquiry,which require protection against unauthorizeddisslosure.

11. Matters and documents of a personal ordisciplinary nature which, if disclosed, could beprejudicial to the discipline and morale of thearmed forces.

12. Documents used in connection withprocurement. selection, or promotion ofmilitary personnel, the disclosure of which couldviolate the inteuity of the competitive system.

NOTE: Official information of the typedescribed in paragraphs 10, 11, and 12 above isclassified Confidcntiai oniy if its unauthorizeddisclosure could be orejudicial to the defenseinterests of the Nati,m. If such information doesnot relate strictly to defense, it must besafeguarded by other means than theConfidential classification.

The use of the Confidential classification is Alimited to defense information or material the Secret

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1' 0

ACCOUNTABILITY

continuous chain of receipts for Topmaterial is maintained. In addition. a


disclosure record form is attached to eachdocument that circulates within a command oractivity, and each person having knowledge ofits contents signs the form.

Each command establishes administrativeprocedures for recording Secret materialoriginated and received, and maintains areceipting system for Secret matter distributedor routed within the command.

Each command also maintains a system thatensures accountability for all Confidentialmaterial originated or received.

PHYSICAL SECURITY

Physical security has to do with safeguardingclassified information by physical means. Itincludes the designation of security areas,stowage, custody, accountability, transmission,dissemination, and ultimate disposition ordestruction. In other words, here we areconcerned with methods of preventingunauthorized persons from obtaining physicalcustody of classified material.

SECURITY AREAS

Spaces containing classified matter areknown as security areas. These security (orsensitive) areas have varying degrees of securityinterest, depending upon the purpose and thenature of the work and information or materialsconcerned. Consequently, the restrictions,controls, and protective measures required varyaccording to the degree of security importance.To nie.F.q different levels of security sensitivity,her th :. three types of security areas; all areas

are cleariy marked by signs reading "SECURITYA REAKEEP OUT. AUTHORIZEDRSONN EL ONLY."

Exclusion Area

Spaces requiring the strictest control ofaccess are designated exclusion areas. Theycontain classified matter of such nature that, forall practical purposes, admittance to the areapermits access to the material.

An exclusion area is fully enclosed by aperimeter barrier of solid constructici. Exitsand entrances are guarded, or secured and alarmprotected; and only those persons whose dutiesrequire access and who possess appropriatesecurity clearances are authorized to enter.

Limited Area

A limited area is one in which theuncontrolled movement of personnel permitsaccess to the classified information therein.Within the area, access may be prevented byescort and other internal controls.

The area is enclosed by a clearly definedperimeter barrier. Entrances and exits are eitherguarded, controlled by attendants to checkpersonal iden tification, or under alarmprotection.

Operating and maintenance personnel whorequire freedom of movement within a limitedarea must have a proper security clearance. Thecommanding officer may, however, authorizeentrance of persons who do not have clearances.In such instances, escorts or attendants, andother security precautions must be used toprevent access to classified information locatedwithin the area. Sonar is designated as a limitedarea.

Controlled Area

A controlled area does not contain classifiedinformation. It serves as a buffer zone to providegeater administrative control and protection forthe limited or exclusion areas. Thus,passageways or spaces surrounding or adjacentto limited or exclusion areas may be designatedcontrolled areas.

Controlled areas require personnelidentification and control systems adequate tolimit admittance to those having bona fide needfor access to the area.

STOWAGE

Stowage refers to the manner in whichclassified material is protected by physicaland/or mechanical means. The degree of

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Chapter 10SECURITY

protection necessary depends on theclassification, quantity, and scope of thematerial.

A numerical evaluation system has beendeveloped for determining the relationshipbetween the security interest and level ofprotection required. The system is outlined inchapter 5 and appendix H of OPNAVINST5510.1 E.

The keys or combinations to safes andlockers containing classified material arc madeavailable only to persons whose duties requireaccess to them. The keys or eombinations mustbe changed at least every 12 months. They alsomust be changed when any person havingknowledge of them is transferred from theorganization, and when the keys orcombinations are suspected of beingcompromised.

Any time you find a safe or cabinetcontaining classified material unlocked andumqtended by assigned persons, be sure toreport the condition immediately to the watchofficer. Do not touch the container or contents,but guard them until the officer arrives. Thewatch officer then issumes responsibility forsuch further ictions as locking the safe, recallingthe responsible persons, and reporting thesecurity violation to the commanding officer.

PROPER HANDLING

Each individual in sonar must take everyprecaution to prevent intentional or casualaccess to classified information by unauthorizedpersons. When classified publications areremoved from storage for working purposes,they must be covered or placed face down whennot in use. If sonar must be vacated, all classifiedmaterial must be properly protected. Roughdrafts, carbon paper, worksheets, and similaritems containing classified information shouldbe placed in a burn bag after each has served itspurpose.

At the end of each watch, all classifiedmaterial that must be passed from watch towatch is inventoried properly and custody istransferred to the relieving watch officer andwatch supervisor. All other classified mattermust be locked up. Wastebaskets should bechecked to ensure no classified trash has

172 167

mistakenly been placed in the wastebaskets.Classified trash must be placed in burn bags andthe bags must be properly stowed untildestroyed according to your command's policy.

Vaults, safes, or lockers used for stowage ofclassified matter must always be kept lockedwhen not under the supervison of authorizedpersonnel. Always rotate the dial of allcombination locks at least four complete turnswhen securing safes, files, and cabinets. If thedial is only given a quick twist, it may bepossible to open the lock merely by turning thedial in the opposite direction. Always make surethat all drawers of safes and file ca' -ets areheld firmly in the locked position. rior toremoval of any furniture from a security area,always check closely for classified material inhidden areas of each desk, safe, or cabinet.

SECURITY CLEARANCES

PERSONNEL CONTROL

An important element of' physical security ispersonnel control. No person is permitted accessto classifil material unless he previously hasbeen granied a security clearance by hiscommanding officer. Every clearance aboveConfidential is based on a national agency check( NAC), a background investigation (B1), or both.

An NAC consists of the investigation of filesand records of a number of agencies includingthe FBI. ONI, and BUPERS. A backgroundinvestigation, which includes an NAC, inquiresinto the loyalty, integrity, and reputation of theperson being investigated.

A personnel security clearance is anadministrative determination that an individualis eligible, from a security standpoint, for accessto classified information of the same or lowercategory as the clearance being granted. Acertificate of clearance does not in itselfconstitute authority for access to classifiedinformation. It is merely a determination ofeligibility for access. Classified information ismade available to appropriately cleared personsonly when it is necessary in the interest otnational defense, when the individual requiresthe information to carry out his assigned duties,when there is no other source of the s5rne


classified information available to him, andwhen he is capable both physically and mentallyof providing the degxee of protection that theinformation requires.

The following is a list of personal acts ot'varying de,grees of seriousness which, it'committed in the past or present, can cause thedenial or revocation of a personal securityclearance.

I. Commission of any act of sabotage,espionage, treason, or sedition; conspiring withor aiding or abetting another to commit orattempt to commit any act of sabotage,espionage, treason, or sedition.

2. Establishment or continuation of asympathetic association with a saboteur, spy,traitor, seditionist, anarchist, revolutionist,espionage or other secret agent or representativeof a foreign nation, or any representathe of aforeign nation whose interests are inimical to theillterests of the United States.

3. Advocacy ot' use of force of violence tooverthrow the government of the United States,or the alteration of the form of government ofthe United States by unconstitutional means.

4. Membership in or affiliation orsympathetic association with any foreign ordomestic organization, association, movement,group, or combination of persons which istotalitarian, Fascist, Communist, subversive, orwhich has adopted a policy of advocating orapproving the commission of acts of force orviolence to deny other persons their rights underthe Constitution of the United States.

5. Actions which serve the interests ot'another government in preference to theinterests of the United States.

6. Failure or refusal to sign a loyaltycertificate, pleading protection of the FifthAmen' t or of Article 31 Uniform Code ofMil;" or refusal to completely answerqu. )ns co:.cained in required security formsor pe:rsonal history statements.

7. Any deliberate misrepresentation,falsification, or omission of material fact.

8. Participation in the activities of anorganization established as a "front" for anorganization referred to above, when one'spersonal views were sympathetic to thesubversive purposes of such organization.

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9. Participation in the activities of anorganization, with knowledge that it had beeninfiltrated by members of subversive groups.

1 O. Sympathetic interest in totalitarian,Fascist, Communist, or similar subversivemovements.

11. Currently maintaining a close,continuing association with a person who hasengaged in activities or associations of the typesreferred to above.

12. The uncovering of any facts whichfurnish reason to believe that the individual maybe subjected to coercion, influence, or pressurewhich may cause him to act contrary to the bestinterests of national security.

13. Willful violation or disregard of securityregulations.

14. Intentional unauthorized, disclosure ofclassified information to any person.

15. A ny criminal, in famous, dishonest,immoral, or notoriously disgraceful conduct-,habitual use of intoxicants to excess; drugaddiction; or sexual perversion.

16. Acts of a reckless, irresponsible orwanton nature which indicate poor judgmentand instability.

17. Any excessive indebtedness, recurringfinancial difficulties, unexplained affluence, orrepetitive absences without leave.

18. Al 1 o t her behavior, activities, orassociations which tend to show that the personis not reliable or trustworthy..

19. Any illness, including any mental'condition, of' a nature which, in the opinion ofcompetent medical authority, may causesignificant defect in the judgment or reliabilityof the individual.

COMPROMISE

No one in the Navy is authorized to handleany classified material except that required inthe performance of duty. All other persons areunauthorized, regardless of rank, duties, orclearance.

If it is known--or even suspectedthatclassified material is lost or passed into thehands of some unauthorized person. the matteris said to be compromised. The seriousness ofthe compromise depends on the nature of' the

i

Chapter 10SECURITY

material and the extent to which theunauthorized person may divulge or make use ofwhat he learns. Never fail to report acompromise that comes to your attention.

DISCIPLINARY ACTIONFOR SECURITY VIOLATIONS

Any person who is found to be responsiblefor the loss, unauthorized disclosure, or possiblecompromise of classified information, and anyperson who violates security regulations shall bepromptly and adequately disciplined, regardlessof rank or rate, or position. Disciplinary actionmay include trial by court-martial. Personsfound guilty of loss of classified materialthrough gross neglect may be fined $10,000 c -imprisoned for not more than 10 years or both.

PERSONAL CENSORSHIP

Personal censorship is the most difficult partof security. Each individual, through indiscreetor boastful conversation, personal letters, anddiscussions of classified information innonsecure spaces, is capable of doing gravedamage to the security of our country. Personaldiscussion of official affairs with families orfriends, or even careless talk, while on duty inthe presence of persons not authorized toreceive certain information, is dangerous andmust be avoided. There is only one safe policyfor you to follow when off dutydon't discussclassified matters with anyone, not even familyor close friends. Usually the desire to impressothers with the importance of one's job is quitestrong. Divulging classified information is anunwise way of trying to impress anyone,particularly when by doing so a man may beendangering his country and many lives.

Loose talk in public places is even moredangerous. Conversation in restaurants, hotellobbies, airports, elevators, taverns, and otherpublic places can be overheard easily. Foreignagents are trained scientifically to collect fromsuch conversations particles of seeminglyharmless information. Once pieced together andanalyzed, these "innocent" bits of talk

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sometimes reveal military information ofincalculable value.

Mail likewise is subject to interception by anenemy. The following topics must not bementioned in personal correspondence:

I. Location, identity, or movement of shipsor aircraft.

Forces, weapons, military installations,or plans of the United States or herallies.

3. Casualties to personnel or material byenemy action.

4. Employment of any naval or militaryunit of the United States or her allies.

5. Criticism of equipment or morale of theUnited States or her allies.

Pe rsonal censorship also extends totelephone conversations. Telephone wires can betapped, and conversations can be overheard at theswitchboard and other points along the circuit.Never discuss classified information over atelephone. A guide to personal conduct ispresented at the end of this chapter.

RESTRAINT ON REPRODUCTION

Those portions of documents and materialswhich contain Top Secret information shall notbe reproduced without the consent of theoriginating activity or higher authority. All otherclassified material shall be reproduced sparinglyin the minimum number of copies; and anystated prohibition against reproduction shall bestrictly observed. The following restrictivemeasures apply to reproduction equipment andto the reproduction of classified material:

I. The number of copies of documentscontaining classified information shall be kept toa minimum to decrease the risk of compromiseand reduce storage costs.

2. Officials, by position title, authorized toapprove the reproduction of Top Secret andSecret material shall be designated. Thesedesignated officials will carefully review the


need for reproductions with a view towardminimizing classified reproductions consistentwith operational requirements and reproductionprohibitions imposed by the material originatoror higher authority.

3. Specific reproduction equipment shall bedesignated for the reproduction of classifiedmaterial; reproduction of classified material shallbe restricted to equipment so designated. Rules,to minimize human error inherent in thereproduction of classified material, will beposted on or near the designated equipment.

4. Appropriate warning notices prohibitingreproduction of classified material shall beposted on equipment used only for thereproduction of unclassified material.

5. If the designated equipment involvesreproduction processes usine extremely sensitivereproduction paper, such paper shall be usedand stored in a manner to preclude imagetransfer of classified information.

a. When thermal copy paper is used toreproduce documents upon which classifiedinformation has been recorded, only Type 1(back coated) thermal copy paper shall beused.

b. When slip sheets are placed betweenthe diazo process film sheets in thereproduction process of classifiedinformation, the slip sheets should behandled as ciassified waste.

6. All copies of classified documentsreproduced for any purpose, including thoseincorporated in a working paper, are subject tothe same controls prescribed for the documentfrom which the reproduction is made.

7. Samples, waste, or overruns resultingfrom the reproduction process shall besafeguarded according to the classification of theinformation involved and shall be destroyedpromptly as classified waste.

8. When classified material is reproduced,the reproduced material shall be marked withthe classification and other special markingswhich appear on the original material fromwhich copies are reproduced. 1 r-

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DISSEMINATION POLICY

Components shall establish procedures forthe dissemination of classified materialoriginated or received by them, subject tospecific rules established by higher authority andby OPNAVINST 5510.1 series. As a furtherlimit on dissemination, the originating official oractivity may prescribe specific restrictions on aclassified document or on its text when securityconsiderations make them necessary.

A General Guide

It is not possible to provide each individualwith a complete list of do's and don'ts as far assecurity is concerned. There are, however, tworules of thumb which will usually help inanswering the questions "Should 1 do this?" or"Should I say this?"

1. Could spies or traitors possibly learnanything from this?

2. Could this possibly help spies or traitorsverify something that they already haveideas about or have guessed?

If there is the slightest possibility that theanswer to either of these two questions might be"Yes," "Probably," or even "Possibly," theaction should not be taken or the statementshould not be made. One of the personalrestrictions that working with classified materialrequires of an individual is that conduct andspeech must always be guarded. The goal of thesecurity program is to train military and civilianpersonnel to the point that whenever andhowever a topic comes up which has even themost remote bearing on classified information,the employees will automatically become alert,watchful, and on their guard against securityslips.

The following list may be used as a generalguide to answering the many questions that maybe asked concerning security information.

1. You may disclose the command youwork for by simply stating that you work forthe Department of the Navy at the address towhich you are assigned. Using utmost discretion,

Chapter 10SECURITY

you may give the official address of yourcommand, your eneral job title, your uade andsalary, and length of service, if required. If anyfurther information is desired by persons orfirms with whom you may be dealing, instructthem o request such information by letteraddressed to your commanding officer.

2. When replying to questions by anyone(including your immediate family), concernimzthe nature of your assignment, you should statethat your work is classified and that the lawprevents you from revealing the type of work inwhich you are engaged.

3. Caution your family nut to discuss yourassignment with others. They should simplystate that they do not know what your dutiesare. Remember, the less your family knowsabout your job, the less likely they are tounwittingly reveal information of value toforeiczn intelligence.

4. If a complete stranger is overly persistentin questionina you about your job, simplyinform him that you do not care to discuss thesubject further. Quiz him as to his name,address, and purpose of his inquiry. Fle willprobably drop the subject. You may leave hispresence, if circumstances permit, or change thesubject. In all cases, report the facts andcircumstances to your commanding officer.

5. Classified matters may only be discussed,outside your assigned ship or station, in othersecure government spaces and then only if it is

necessary to effect official business. Firstdetermine the clearance status of the other partyand his need to know in conjunction with thatbusiness. The information will be limited to thatwhich is necessary to carry on official business.

6. You may associate with non-citizens ona close social basis. However, any contact otherthan official with personnel fromCommunist-controlled countries should bereported to your commanding officerimmediately. Meetings with other foreignnationals need not be reported.

7. There may be restrictions on goingoverseas after leaving your present assignment,either for a new assignment or privately. Thespecific restrictions are dependent upon the typeof classified information to which you may havehad access and the area of the world to whichyou wish to go. The length of time the

restriction is imposed depends upon theassignment that you held. Certain otherrestrictions are imposed on private overseastravel by the State Department. When leavingyour present assignment, you will be informedas to what restrictions apply, if any.

8. There are also security requirementsconcerning vacation or business travel abroad.Your commanding officer will assure that youare given a defensive security briefing to alertyou to be on guard against exploitation byothers whose interests may be inimical to thoseof the United States, prior to travel under thefollowing conditions.

a. Travel to or throuhCommunist-controlled countries for anypurposes.

b. Attendance at international,scientific, technical, engineering, or otherprofessional meetings in any country outsidethe United States where it can be anticipatedthat Communist-controlled representativeswill participate or be in attendance.

9. Generally speaking, nothing may bewritten or said for public consumption aboutthe status, mission, composition, organization,or function of the command that you arepresently assigned to or the results that itobtains. Of course, certain information may beprinted for public consumption, but only thecommanding officer or his designatedrepresentative may release such information.

10. Upon learning of what appears to be asecurity violation by the press. radio, television,or any other means normally available to thepublic, bring it to the attention of your securityofficer or commanding officer. State the facts:what, when, where, how, and by whom. If it isprinted material, submit a copy or an actualclipping of the material. Include theidentification of the periodical, the fiuthor,and/or the photographer.

II. From time to time you may wonder whyyou are required to be so security consciouswhen the news media seems to he tellingeverything. This is understandable. However,always remember that just because certain itemsappear in periodicals, newspapers, or On the air,it does not necessarily mean that theirpublication was authorized nor does it mean

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1 7 6


that the information is factual. Frequently, suchreleases are the educated guesses of the author.Do not deny, affirm, or comment on suchmaterial; it will only aid in establishing as factthat which, before, was only suspected.

12. When separated from the Navy, youmust continue to be security conscious,especially when applying for a job. During yourjob interview, you may state that you wereassigned to a particular command, along withyour general job title. Under no circumstancesmay you include Department of Defenseclassified information. It is recommended that.prior to your separation, you write a completejob description of your duties andresponsibilities. Take your resume to yourdivision officer for his advice, assistance, andclearance.

As a Sonar Technician you will have accessto large amounts of classified material, whichsometimes makes life aboard ship very tedious.The majority of your shipmates do not havesecurity clearances or even a need to know. Youcan not. of course, give them any classified

information. Be ever mindful of where you are,even when you are talking to other SonarTechnicians. Security information can only bediscussed in sonar or the few other secure spacesaboard ship. Discussion of security informationis forbidden in any of the other spaces aboardship, such as the mess hall or your berthingcompartment.

The above list does not cover everycircumstance which may arise. Should asituation arise which is not covered in thischapter, no statement should be made. Reportthe situation to your superior and an appropriateanswer will be given for future guidance.

You alone are responsible for any violationoF security that you may deliberately orunintentionally commit. You are urged tobecome fully acquainted with the contents ofthe Department of the Navy InformationSecurity Program Regulation, OPNAVINST5510.1E. Moreover, you must always vigilantlyguard against violating the trust which has beenplaced in you. To relax security, even for amoment, may invite disaster.

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APPENDIX I

GLOSSARY

ABSORPTION: Loss of energy that is turnedinto heat.

ACOUSTIC: Pertaining to sound or the studyof sound.

ACTIVE SONAR: An apparatus that radiatesand receives information from returning echoes.

ADVANCE: After rudder is applied, thedistance continued along original course until onthe new course.

AFTERNOON EFFECT: The daytime heatingof the surface water which results in a reductionof sonar ranges usually in the afternoon.

AMBIENT NOISE: The naturally occurringnoise in the sea and the noise resulting fromman's activity but excluding self-noise andreverberation.

AOB (Angle on the Bow): The angle formedbetween an imaginary line drawn from a target'sstern through its bow and outward, and a secondline between the target and own ship. Angle ismeasured from 0000 to 180° both port andstarboard. Clockwise down starboard side andcounterclockwise down port side.

ARRAY: A group of hydrophones arranged toprovide the desired directional characteristics.

ASROC: Antisubmarine rocket.

ASW (Antisubmarine Warfare): Operationsconducted against submarines, their supportingforces and bases.

BA THYTHERMOGRAPH: A device thatautomatically plots a graph showingtermperature as a function of depth whenlowered into the sea.

BEARING: The direction of an object from anobserver, measured clockwise from a referencepoint.

BEARING DRIFT: Bearing cursor is trainedback and forth across the target to check for thebearing width, and the target is classified. Theoperator then places the cursor in the center ofthe target pip. The cursor shows direction ofsound reception. Its length indicates range whenthe cursor line is adjusted to touch the targetecho. With the ship headed for the target on asteady course, and at a constant speed, with thecursor bisecting the echo, any change in targetbearing results from target movement. If thetarget moves to the right, the operator musttrain his cursor to the right in order to remainon target, reporting "Bearing drift right." If thetarget moves to the left, he must train his cursorto the left to remain on target, and reports"Bearing drift left."

BOTTOM BOUNCE: That form of soundtransmission in which sound rays strike thebottom, in deep water, at relatively steep angles,and are reflected toward the surface.

CAVITATION: The formation of local cavities(bubbles) in a liquid as a result of the reductionof total pressure. This pressure reduction mayresult from a negative pressure produced byrarefaction or from the reduction of pressure byhydrodynamic flow such as is produced by highspeed movement of an underwater propeller.

173

178


CIC (Combat Information Center): The tacticalcommand center of the ship.

COMPRESSION: In wave motion, the forcingtogether of the medium's molecules. SeeRAREFACTION.

COUNTERMEASURES: Devices and/ortechniques intended to impair the operationaleffectiveness of enemy activity.

CRT: Cathode ray tube.

CW (Continuous Wave): The on-off keying of acarrier frequency of a transmitter in such a wayas to form a code that can be translated into areadable intelligence.

db (dB): Abbreviation for decibel.

DECIBEL: A value that expresses hecomparison of sounds of two differe;..intensities. This value is defined as 10 tit= iecommon logarithm of the ratio of the two soundintensities.

DECK PLANE: The deck plane represents thelevel of the ship's gun mounts. (references toguns include similar weapons systems.) When theship is level, the horizontal and dec. planescoinc e, but when the ship rolls and pitches,the deck plane deviates from the horizontal. Thestable element measures the amount of angulardeviation and transmits the information to thefire control system. The fire control computercompensates for deck tilt by computing asolution in the horizontal plane, then makestraiii and elevation corrections. What the systemdoes, in effect, is bring the deck plane back tothe horizontal.

DENSITY: The mass per unit voiume.Example: salt water-30 parts/1000.

DIPPING SONAR: Used by helicopters.Lowered from the helicopter for searching andretracted for flight.

DIRECT PATH: Sound waves that travel indirect paths at whatever angle they left thesource.

174

1. 7 9

DI VE RGENCE: Energy loss caused byspreading in all directions.

DOPPLER EFFECT: If there is a relativemovement between a wave source and areflecting surface, the frequency of the wavesreturning to the source will differ from that usedin the original emission. This is known asdoppler effect. In active sonar sets, th:! effect ofsource movement is allowed for automaticallyand so the change in frequency indicates relativemovemen t of the reflector alorqg thesource/reflector line.

DYNAMIC TESTS: Dynamic tests are rn tocheck the computer's generation of bearing andrange for specified time intervals against amathematical solution whose answer contains.2orrect amounts of change in quantities for likeconditions. During the test, fixed values areassigned to relative motion rates by manuallysetting inputs to the relative motion group. Thetime system of the computer .is then moved,either manually or by thz time motor, anamount equal to the test :nterval. Readings arethen taken to ensure correctness of the solution.

ECHO: That portion of the energy reflected tothe receiver from the target.

ELECTROSTRICTIVE: A mechanicaldeformation caused by the application of anelectric field.

ESM (Electronic Warfare Support Measures):Concerns electronic emissions andcountermeasures.

FATHOMETER: A direct reading device fordetermining water depth by reflecting sonic orultrasonic waves from the ocean bottom.

F BM: Fleet Ballistic Missile Submarine.(SSBN)

FCS. Fire Control System.

FIRE CONTROL: The technique for deliveringfire on a selected target.

Appendix IGLOSSARY

FLOW NOiSE: The rit-7:A: produced ci watermovement past th,:' tran!,ducer, hydrophonearray housing, or the hti of a moving ship orsubmarine, or by t"e vrtical movement of asonobuoy in the sea.

FREQUENCY: Rate of vibration of a soundsource. Determines the pitch of a sound.

GRADIENT, NEGA IN nen thetemperature of the wa ses with depth,it has a negative temper ient.

GRADIENT. POSI L: When thetemperature of the water increases with depth, ithas a positive temperature gradient.

HERTZ: A unit of frequency equal to onecycle per second.

HORIZONTAL PLANE: A horizontal plane istangent to the suirface of the earth. Visualize thiscondition by laying a playing card on an orange.The card represents the horizontal plane, theorange symbolizes the earth, and the point ofcontact between the two is the point oftangency. Every plane parallel to the horizontalplane is likewise a horizontal plane.

HORIZONTAL RANGE: Range from own shipto target measured in the horizontal plane.

ISOBALLAST CURVES (Lines): Precalculatedlines appearing on recorder charts. Indicatesbuoyancy (used on submarines).

ISOTHERMAL LAYER: A layer of water inwhich there is no appreciable change oftemperature with derqh.

ISOVELOCITY LAYER: A layer of water inwhich there is no appreciable change of soundvelocity with depth.

kHz (Kilohertz): A prefix representing 103 or1000.

LAYER DEPTH: The depth from the surfaceof the sea to the top of the first significantnegative thermocline.

Q75

LAYER EFFECT: Partial protection fromecho ranging and listening detection wliee belowlayer depth.

MAD (Magnetic Anomalous Detectors): Equip-ment capable of detecting slight distortionsin the earth's magnetic field. In the U.S. Navy,used exclusively by aircraft.

M AG NE TO ST R I CTI VE (ION) PROCESS:Changes in metal caused by being subjected to amagietic field.

M C: Shipboard announcing andintercommunications system circuit.

MDCS: Maintenance Data CollectionSubsystem.

mHz (Megahertz): Prefix denoting 106 or1,000,000.

MICROPASCAL: The standard unit of' measurein all sonar computations for sonar soundpressure level. Replaces the microbar.

M1P: Maintenance Index Page (3-.1 system).

MRC: Maintenance Requirement Card (3-Msystem).

MULTIMETER: Several instruments orinstrument circuits combined in a singleenclosure and used in measuring two or moreelectrical quantitiec in a circuit.

OCEANOGRAPI IY or OCEANOGRAPIBranch of science dealing with the Ocean:pertain;ng to the ocean.

PASSIVE SONAR: An appnatus that receivesenergy generated from another source.

PIEZOELECTRIC: The property of certaincrystals which produce voltage when subjectedto a mechanical stress.

PMS: Planned Maintenance Subsystem.

QUENCHING: The reduction in underwatersound transmission or reception resulting from


absorption art, scattering of sound energy by airbubbles entrapped around the 3onar dome.

RANGE: The distance an object from anobserver.

RAREFACTION: In ,,Tve motion, when thevibration is inward, a racefacion or region ofreduced pressure is produced.

RATE TESTS: Tests of own ship and targetrate mechanisms by having certain componentsgenerate movement for a certain time frame.

RDT: Rotating dliectional transmission.

REFLECTION, SOUND: S o und raystransmitted in the sea eventually reach either thesurface or the bottom. Since these boundariesare abrupt and very different in soundtransmitting properties from the water, soundenergy along a ray path striking tl s. boundarieswill be returned (reflected) to the water.

REFRACTION, SOUND: The bending orcurving of ,,und ray that results when the raypasses from a re0on of one sound velocity to aregion of a different velocity. The amount of raybending depends on the amount of differencebetween sound velocities.

RELATIVE BEARING: The angle betweenships head and an object measured in aclockwise direction.

RELATIVE MOTION: The apparentmovement of an object in relation to anotherobject.

REVERBERATION: The combined sound ofmany small echoes returned to the hydrophoneby reflection from the surface, at the bottom,and particles in the water.

R/T: Radio Telephone.

SCANNING SONAR: Sonar that transmitssound pulses in all directions simultaneously.

SCATTERING: R eflection losses fromparticles suspended in the water.

S 1176

SONAR: Acronym for SOund Navigation AndRanOng. Apparatus or technique of obtainingi n formation reguarding objects or eventsunderwater.

SONIC: Within the audible range of the humanear.

SONOBUOY: Small floating buoy with anattached hydrophone and a radio transmitterthat relays underwater sounds picked up by thehydrophone to ASW units.

SOUND CHANNEL: Condition when twolayers of water with near equal temperaturesproduce a sound channel. Sound between thetwo layers is refracted !ly the layers, staysbetween them, and travels for great distances.

S / P : Sound powered. Example:Sound-powered phones. Shipboard system usingvoice to activate circuits. (No batteries orexternal power.)

SSXBT (Submarine Expendable BT): Tempera-ture versus depth plot to 2500 feet.

STATIC TEST: A st using fixed inputs withthe problem stopped at a fixed point. Outputs(or answers) are also fixed.

SUBROC: Submarine-installed weapon systemde sig d as de fense against high-speednuclear-powered submarines.

SUBSONIC (Infrasonic): A frequency belowthe audio ranw..

TARGET ANGLE: The relative bearing of thesurface ship from the target.

TARGET ASPECT: The relative position ofthe submarine with respect to the sound beam.

THERMAL NOISE: A very !ow level nois,_.produced by molecular movement in the sea.

THERMISTER: A solid state, szifiti-conductingdevice whose resistance varies with temperature.

THERMOCLINE: A region of relatively rapiddecrease in temperature.

Appendix I--GLOSSARY

3-M SYSTEM: Maintenance and Material Man-agement system.

TRANSDUCER: A device used to convertelectrical energy to mechanical energy.

TRANSFER: After rudder is applied, thedistance moved at right angles to the originalcourse during the turn.

TRUE BEARING: The angle from north to theline of sight, measured clockwise through 3600 .

TRUE MOTION: The movement of an objectacross the earth, using true (geographic) north asthe reference point.

TURN COUNTING: Counting revolutions of acontact's propelkers to determine its speed or thetype of ship.

UB PLOT: Underwater Battery Plot. Firecontrol equipment installed here.

UBFCS (UBWCS): Underwater I3attery FireControl System. Example: Mk 114 FCS.

ULTRASONIC: Having a frequency above theaudible sound.

VARIABLE DEPTH SONAR (VDS): The termis normally used to describe sonar whosetransducer is towed beneath its parent ship withthe object of improving sonar deteion ranges.Helicopter and submarine sonars, though

177

variable depth, are not usually included iu thiscategory.

VELOCITY: A vector quantuy that includesboth magnitude (speed) and direction bi relationto a given frame of reference.

VERTICAL PLANE: A vertical plane isperpendicular to the horizontal plane, zind is thereference from which berings art_ measured.Relative bearing, for exampie, is measured in thehorizontal phine clockwise from the verticalplane through own ship's centerline to thevertical plane through the line of sight. Thesystem of planes makes possible the deisgn andconstruction of mechanical and electronicequipment to solve the fire control problem.These lines and planes are imaginary extensionsof some characteristic of the ship or target, or ofthe relation in space betv.een

WAVELENGTH: The d't c.. between pointscorrespon(li p!' two conseeut ive

cycles.

WIRE-GUI1Yr.:1) r0.10. . Tolpedo liaked tothe ship by a wire tigungh wbr..h sHp czni

insmir guich.nce and Lonlnan iis to th2iornedo and the torrcdo car tcansirit s,atussignals tc, the ship.

BT 1a4.hvtl,crh1c1aph):uce -that ,iutomarir__Oly ploTs a graph showingtemperature as a of depth whenlov.-2red into the sea.

A

2

A

Access, 163Accountability, 165Active sonar, 85-87Advancement examination, 11Advancement, how to qualify for, 11-14Aircraft, 32-34

antisubmarir :craft, 34patrol pla

Aircraft, antif ,N ine, 34Aircraft c- ';V), 25Alien, 16,Allied cornmt -cation publications, 10Ambient noise, 11-44Antisubmarine i',:..craft, 34Antisubmarine armanent, 29-32

ASROC, 30torpedoes, 30-32

Antisubmarine units, 24-29aircraf' L.wier (CV), 25destroyer (DD), 25frigate (FF), 26guided-missile cruiser (CG) (CGN), 29guided-missile destroyer (DDG), 25guided-missile frigate (FFG), 26-29

Appendix IGlossary, 173-177Armament, antisubmarine, 29-32Armament, submarine, 19-24ASROC, 30ASW, history and development of, 15-34Attack submarines (SSN), 19

Ballistic solution phase, 114Basic fire control, 109-126Bathythermogaph, 58-70Bathythermograph logs, 70

INDEX

18 3178

Bathytherrnograph (SSBXT) submarineexpendabk.,, 62

Bathythermogaph system surface shipexpendable, 62-64

Bathythermograph systems submarine. 59-62Bearing drift, 80Bearings, 72-78

converting true and relative bearings,76-78

gyro failure, 75relative bearings, 73stern line indicator, 74true bearings, 73

Bearings and motion, 71-84Bearings relative, 73Bearings, true, 73

Call signs, 130Capacitors, i 53Ca,-rier, aircraft (CV), 25Categories, classific:Ition, 165Censorship. person.d, 169Characteristics of sound, 39Classification, 163Classification categories, 165

confidential, 165secret, 165top secret, 165

Classification guide,Classified informatiol., 163Classifier, 163Clearance, 163Clearances, security, 167Code, 132-134Code practice, 134-137

prosigns, 135-137

INDEX

Communications, 127-140Communications, external, 129-132Communications, internal, 1 27-1 29Communications, underwater, 137-140Competent authoritycommanding officer, 163Compromise, 163, 168Computing target angle, F!.1-84Confidential, 165Control, personnel, 167Converting true and relativt. bearings, 76-78Cruiser, guided-missile, (CG) (CGN), 29Custodian, 164

Daily heating, 65-70Data, restricted, 164Declassifk tion,Deep water sound propagation, 51-53Definitions, 162-165

access, 163alien, 163classification, 163cicissification guide, 163classified information, 163classified material, 163classifier, 163clearance, 163competent authority--commanding officer,

163compromise, 163custodian, 164declassification, 164document, 164downgrade, 164formerly restricted data, 164marking, 164need to know, 164restricted data, 164security, 164upgrade, 164

Depth sow der (fathometer) 100-104Depth-Fo.ind speed measuring set AN/BQH-1A,

59-62Designation, terminal, 148-150Destroyer, (DD), 25Destroyer, guided-missile (DDG), 25Destruction phase, 114Detecti(7r. phase, 113 1 , 4

179

Detection-to-destruction phases, 113-115ballistic solution phase, 114destruction phase, 114detection phase, 113target motion analysis pha, 114tracking phase, 113

Development and history of ASW, 15-34Dipping sonar, 98Disciplinary action for security violations, 169Dissemination policy, 170-172Document, 164Doppler and reverberations, 53Doppler and target aspect, 80Doppler effect, 53-55

doppler and reverberations. 53doppler reports, 54

Doppler/no doppler, 55Doppler reports, 54Downgrade, 164

Echo strength, 56Echoes from false targets, 56Echoes, interpreting, 55-57Effects of temperature, 58

temperature layers, 58EIBs and EIMBs, 8EIMBs and EIBs, 8Electric shock, 143Enlisted rating structure, 2

. sonar technician rating, 2Equipment, 118Equipment, test, 144-147Examination, advancemeni I !

External communications, Icall signs, 130prowords, 130-13'7radiotelephone, 11Jradiotelephone proced.,,res, 12)

Fire control, basic, 109-126Fire control nomenclature, 116Fire control system, representative underwa ter,

109Fire control system tests, 122-125Fire control systems, underwater. 1 ' 9-122


Fire control, underwater, 109Fleet ballistic missile submarines (SSBN), 19Fleet Ballistic missile system, 21-23Formerly restricted data, 164Frequency counter, 147Frigate (FF), 26Frigate, guided-missile (FFG), 26-29Fundamental problem, 115-126

equipment, I 18fire control nomenclature, 116fire control system tests, 1 22-1 25interpreting dial readings, 125reference planes, 115schematic identification of system

components, 119sonar position quantities, 116-118underwater fire control systc ins, 119-122

General safety precautions, 141-143Generators, signal, 146Glossary, Appendix I, 173-177Gradient, negative, 65Gradient, positive, 65Grounding test equipment, 143Guided-missile cruiser (CG) (CGN), 29Guided-missile destroyer (DDG). 2SGuided-missile frigate (FFG), 26-2°Gyro failure, 75

History and development of ASW,How to qualify bor adv -,:ement, 11-14

Indicator stern line, 74Indicators remote, 128Information, classified, 163Information sonar, 71Internal communications, 127-129

MC systems, 128remote indicators, 128sound-powered phones, 127

International morse code, 132-134the code, 132-134

1 (0 5

180

Interpreting dial readings, 125Interpreting echoes, 55-57

doppler/no doppler. 55echo strength, 56echoes from falk.. targets, 56

Isothermal layer, 66

Keeping up with new developments, 3

Leadership responsibilities, 2Logs, bathythermograph, 70

ri

Maintena nce, 1 54-1 61maii,:nance and material management

system, 156-161types of maintenance, 154-156

Maintenance and material management system,156-161

Maintenance; test equipment; test methods,141-161

Maintenance, types of, 154-156Management system maintenance and material,

1 56-1 61Manufacturer's technical manual, 8Marking, 164Material and maintenance management system,

156-161MC systems, 128Measurement of sound, 40Methods, submarine communication, 140Methods, test, 147-154Mines, 21Missile system, fleet ballistic, 21-23Missile system, SUBROC, 23Modern active sonar theory, 9 1-94Modern passive sonar theory, 96Morse code, international, 132-134Motion, 78

advance and transfer, 78-80bearing drift, 80doppler and target aspect, 80relative motion, 78true motion, 78

INDEX

Motion and bearings, 71-84Motion, relative, 78Motion, true, 78Multimeter, 145

NATO/Allied tactical doctrine publications, 10NAVEDTRA publications, 8NAVSEA (formerly NAVSHIPS) publications, 8Negative gradient, 65Noise, 40Noise, ambient, 41-44Nomenclature, fire conrtol, 116

0Operation, 64Oscilloscope, 145

Passive sonar, 94-96Patrol plane, 34Pelsonal censorship, 169Personnel control, 167Phase, ballistic solution, 114Phase, destruction, 114Phase, detection, 113Phase, target motion analysis, 114Phase, tracking, 113Phases, detection-to-destructior 11-1 15Phones, sound-powered, 127Physi Jal security, 166

proper handling, 167security areas, 166stowage , 166

Physics of sound, 35-57ambient noise, 41-44characteristics of s ind, 39measurement of sou.,,i z1Cnoise, 40quenching, 47reflections, 45refraction, 46(equiremnts for sound, 35-37reverberations, 46sound waves, 37-39transmission losses, 44underwater sound

Planes, reference, 115Policy dissemination, 170-172Positive gradient, 65Power tools, safety with, 143Practice, code, 134-137Principles of sonar, 85-108Principles, security, 162Problem, fundamental, 115-126Procedure, voice, 137-140Procedures, radiotelephone, 129Propagation of sound in the sea, 47-53

deep water sound propagation, 51-53structural conditions, 47

Proper handling, 167Prosigns, 135-137Prowords, 130-132Publications, allied communication, 10Publications, NATO/Allied tactical doctrine, 10Publications, NAVEDTRA, 8Publications, NAVSEA (formerly NAVSHIPS),

8

Publications promulgated by CNO, 8Publications promulgated by COMNAVCOMM,

9Publications, U.S. Communication, 10Publication. U.S. Navy tactical dnctrine, 9Purpose or the security program, 62

Quenching, 47

Radiotelephone, I 2.vRadiotelephone procedures, 129Rating, sonar technician, 2Rating structure, enlisted, 2Reading XBT recorder traces. 64-70

daily heating, 67-70isothermal layer. -.)6

nc,;!ative gradient, 65positive gradi,mt, 65XBT trace marking, 70

Reference planes. 115Reflections, 45Refraction, 46Relative bearings, 73Relative motion, 78


Remote indicators, 12SReport everything you hear, 57Representative underwater fire control

system, 109Reproduction or restraint, 169Requirements for locating submarines, 71

sonar information, 71Requirements for sound, 35-37Resistors, 150-153Responsibilities and rewards of advancement,

2-5Responsibilities, leadership, 2Restraint on reproduction, 169Restricted data, 164Restricted data, formerly, 164Reverberations, 46Reverberations and doppler, 53Rewards and responsibilities of advancement,

keeping up with new developments, 3leadership responsibilities, 2working with others, 3-5

Safety, 141-144electric shock, 143general safety precautions, 141-143gounding test equipment, 143safety with power tools, 143

Safety precautions, general, 141-143Safety with power tools, 143Schematic identification of system components,

119Secret, 165Security, 162-172Security areas, 166Security clearances, 167

personnel control. 167Security, physical, 166Security principles, 162Security program, purpose of, 162Security violations, disciplinary action for,

169Shock, electric, 143Signal generators, 146Sonar, active, 85-87Sonar dipping, 98Sonar information, 71Sonar, passive, 94-96

Sonar position quantities, 116-118Sonar, principles of, 85-108Sonar systems, 85-108

active sonar, 85-87depih sounder (fathometer), 100-104dipping sonar, 98modern active sonar theory, 91-94modern passive sonar theory, 96passive sr nar, 94-96sonobuoys, 99tape recorder, 104-108transducers, 87-91,ariable depth sonar (VDS), 97

Sonar technician, 1-14Sonar technician rating, 2Sonar theory, modern active, 91-94Sonar theory, modern passive, 96Sonar variable depth (VDS), 97Sonobuoys, 99Sound, characteristics of, 39Sound in the sea, propagation of, 47-53Sound, measurement of, 40Sound, physics of, 35-57Sound propagation, deep water, 5 1-53Sound pulse, underwater, 44Sound, requirements for, 35-37Sound A,aves, 37-39Sound-powered phones, 127Stern line indicator. 74Stowage, 166Structural conditions, 47Studying for the test, 5-11

Allied communication publications, 10EIBs and EIMBs, 8manufacturer's technical manual, 8NATO/Allied tactical doctrine publications,

10NAVEDTRA publications, 8NAVSEA (formerly NAVSHIPS)

publications, 8publications promulgated by CNO, 8publications promulgated by

COMNAVCOMM, 9U.S. communications publication, 10U.S. Navy tactical doctrine publications, 9

Sul:, -arine, 15-19attack subma.:.-Ics (SSN), 19fleet ballistic missile submarines

(SSBN), 19general description, 17-19his,ory .nd development, 15-1717

182

INDEX

Submarine armament, 19-24fleet ballistic missile system, 21-23mines, 21SUBROC missile system, 23torpedoes, 20

Submarine A/S weapons, 112

Submarine bathythermograph systems, 59-62depth-sound speed measuring set

AN/BQH-1A, 59-62submarine expendable bathythermogaph

(SSXBT), 62

Submarine communication methods, 140

Submarine expendable bathythermograph(SSXBT), 62

Submarines, requirements for locating, 71Submarines (SSBN), fleet ballistic missile, 19Submarines (SSN), attack, 19SUBROC missile system, 23Surface A/S weapons, 111

Surface ship ex7,-- ,i.able bathythermouaphsystem, 62-6,1

operation, o-T

System, bathythermograph surface shipexpendable, 62-64

System components, schematic identifHation of,119-122

System tests, fire control, 122-125Systems, MC, 128Systems, sonar, 85-108Systems, underwater Fre control, 119-11'

T

Tape recorder, 104-108Target and doppler aspect, 80Target ande, computing, 81-84Target motion analysis phase, 114Technical manual, manufacturer's, 8Technician, sonar, 1-14Thrnperature, effects of, 58

mp er atur e layers, 58Terminal designations, 148-150Test equipment, 144-147

freouency counter, i 47muitimeter, 145

Test equipment (Continued)oscilloscope, 145signal generators, 146transistor tester, 147

Test equipmeni grounding, 143

Test equipment; test methods; maintenance,141-161

Test methods, 1 47-1 54capacitors, 153resistors, 150-153terminal designations, 148-150

Test methods; test eq,npment; maintenance,141-161

Test, studying for, 5-1:Tester, transistor, 147Top secret, 165Torpedoes, 20, 30-32.1-acking phase, 113

Transducers, 87-91Transistor tester, 147Transmission losses, 44True and r2lative 1:.earinf!s. convening. 76-78

1,-/:::fmgs. 73True :notion, 78Type,' of maintenance, 15 -156

Underwater communications, 137-140submarine communications methods, 140voice procedure, 137-140

Underwater fire control, 109representative underwater rire control

system, 109

Und.:'rwater fire control systems, 119-122Underwater sound pulse, 44Units, antisubmarine, 24-29UpE-; ade, 164U.S. communication publication, 10U.S. Navy tactical doctrine publications, 9

V

Variable depth sonar (VDS),Voice procedure: 137-140

183

1S8


Waves, sound, 37-39Weapons, 110-113

submarine A/S weapons, 112surface A/S weapons, III

Weapons, sublinrinc A/S, 112

Weapons, surface A/S, illWorking with others, 3-5

XBT recorder traces, reading, 64-70XBT trace marking, 70

IJ)9

184

OCCUPATIONAL STANDARDS

Sonar Technician Third Class (Surface) & (Subn..irine)

Covered in Assignment orBibliography

STG STS

14 ELECTRONICS MAIN IENANCE

14617 Identify underwater fire control symbols 4

14676 Identify standard electronic component color coding 5 5system

14963 Perform op:rational tests and make external adjustments NT 10131 NT 10132on equipment

1.8 Ti.ST EQUIPMENT

18133 Operate general purpose test equipment

22 SENSOR OPERATIONS

22232 Identify sounds pi-oc!uced by surface ships, 1, pedoes.submarines, evasion devices, sonar transmissions, marnelife, and natural phenomena

5 5

22233 Interpret passive/active sonar recorder traces NT 1 0131 NT 1013::

22234 Identify LOFAR contacts NS 0967 NS 0967340-".020 3404020

22235 Operate !;onar sensors for de'-ction and classification of 4 4sonar contacts

22238 Distinguish the characteristics, fun,:tions and effects of NT 10131 NT 10132cc:-.trolled jamming and evasive &vices on sonar operations

22240 Determine range predictions1 0 2

185

Sonar Technician Third Class (Surface) & (Submarine)

22 SENSOR OPERATIONS (Continued)

22241 Prepare and interpret sonar messages

Covered in Assignment orBibliography

STG STS

22141 Interpret acoustic conditions to determine bestsubmarine conditions to avoid detection

11243 Classify and record contacts NT 10131

21144 Determine: 3A. True and relative bearingsB. Range actionsC. Target angle, target aspect and DopplerD. True and relative motion and target course

22156 Construct and interpret the following sonar plots:A. Time bearing (Barnard) plmB. Relative motion (Lynch) plotC. Sonar navigational (Strip) plotD. Time/Range plot

-

NT 10132

3

NT 10132

21160 Locate primary/secondary and casualty power circuits NT 10131 NT 10132

21263 Recognize major equipment malfunctions during sensor NT 10131 NT 10132operations

22802 Operate tape recorder 6 6

22804 Operate bathy thermograph 4 4

22806 Operate the underwater fire control system including NT 10131dizd readbig and positioning operational controls topredetermined values

24 ELECTRICAL MAINTENANCE

24526 Inspect and clean commutators and slipring assemblies: 5 5inspect and replace brushes

24571 Inspect, clean, and tighten or replace stylus

28 TECHNICAL DRAWINGS

NS 0967WO 0130

NS 0967000 0130

28080 Identify electronic components on schematics :ind trace NT 10087 NT 10087major signal flow

Sonar Technician Third Oass (Surface) & (Submarine)

51 MAINTENANCE PLANNING AND QUALITY ASSURANCE

Covered in Assignment OrIinriIPhV

STt; STS

51011 Complete maintenance data forms for: OPNAV OPNAVA. Completed maintenance actions (NIAE) INsT INSTB. Deferred maintenance action-. 4790.4 4790.4C. Work requests

51026 Use maintenance reqnirement cards (MR0 ()kNAV OPNAVINST INST4790.4 4790,4

86 COM \!!

8608 .Jperate Inderwater tHophone5 5

860-- iiterior communications facilities associated with 4 4.,or operations

;ATION &ND TACTWAL SUPP(H,T

8722 i Oprate fathometer

t.ROMECHANICAL MAINTENANCE

L091 Inspect, clean and lubricate electromechanical equipment

94 MECHANICAL MAINTENANCE

3

NS 096-000 0130

NS 0967000 0130

94764 Use and maintain handtools and portable power tools 5 5

11,2

187

INTRODUCTION TO SONARNAVEDTRA 10130-C

Prepared by the Naval Education and Training Program DevelopmentCenter, Pensacola, Florida

Your NRCC contains a set of assign-ments and self-scoring answer sheets(packaged separately) . The Rate Training.Manual, Introduction to Sonar,NAVEDTRA 10130-C , is your textbook forthe NRCC. If an errata sheet comes withthe NRCC, make all indicated changes orcorrections. Do not change or correctthe textbook ..)1" assignments in any otherway.

HOW TO COMPLETE THIS COURSE SUCCESSFULLY

Study the textbook pages given atthe beginning of each assignment beforetrying to answer the items. Pay attentionto tables and illustrations as theycontain a lot of information. Making yoUrown drawings can help you understand thesubject matter. Also, read the learningobjectives that precede the sets of items.The learning objectives and items arebased on the subject matter or studymaterial in the textbook. The objectivr..stell you what you should be Able to doby studying assigned textual materialand answering the items.

At this point you should be readyto answer the items in the assignment.Read each item carefully. Select theBEST ANSWER for each item, consultingyour textbook when necessary. Be sureto select the BEST ANSWER from thesubject matter in the textbook. You maydiscuss difficult points in the coursewith others. However, the answer youselect must be your own. Use only theself-scoring answer sheet designatedfor your assignment. Follow the scoringdirections given on the answer sheetitself and elsewhere in this course.

Your NRCC will be administered byyou:: command or, in the case of smallcommands, by the Naval Education andTraining Program Development Center.No matter who administers your courseyou can complete it successfully byearning grades that average 3.2 or

higher. If you are on active duty, theaverage of your grades in all assign-ments must be at least 3.2. If you areNOT on active duty, the average of yourgrades in all assignments of eachcreditable unit must be at least 3.2.The unit breakdown of the course, Ifany, is shown later under Naval ReserveRetirement Credit.

WHEN YOUR COURSE IS ADMINISTEREDBY LOCAL COMMAND

As soon as you have finished anassignment, submit the completed self-scoring answer sheet to the officerdesignated to administer it. He willcheck the accuracy of your score anddiscuss with you the items that you donot understand. You may wish to recordyour 3core on the assignment itself sincethe self-scoring answer sheet is notreturned.

If you are completing this NRCC tobecome eligible to take the fleetwideadvancement examination, follow aschedule that will enable you to completeall assignments in time. Your scheduleshould call for the completion of atleast one assignment per month.

Although you complete the coursesuccessfully, the Naval Education andTraining Program Development Center willnot issue you a letter of satisfactorycompletion. Your command will make a nr,tein your service record, giving you creditfor your work.

WHEN YOUR COURSE IS ADMININTEREDBY THE NAVAL EDUCATION AND TRAININGPROGRAM DEVELOPMENT CENTER

After finishing an assignment, goon to the next. Retain each completedself-scoring answer sheet until youfinish all the assignments in a unit (orin the course if it is not divided intounits) . Using the envelopes provided,

1 5 3

mail your self-scored answer sheets to theNaval Education and Training ProgramDevelopment Center where the scores willbe verified and recorded. Make sure allblanks at the top of each answer sheetare filled in. Unless you furnish all theinformation required, it will beimpossible to give you credit for yourwork. You may.wish to record your scoreson the assignments since the self-scoringanswer sheets are not returned.

The Naval Education and TrainingProgram Development Center will issue aletter of satisfactory completion tocertify successful completion of thecourse (or a creditable unit of thecourse). To receive a course-completionletter, follow the directions liven oathe course-completion form in the backof this NRCC.

You may keep the textbook andassignments for this course. Return themonly_ in the event you disenroll from thecourse or otherwise fail to complete thecourse. Directions for returning thetextbook and assignments are given on thebook-return form in the back of thisNRCC.

PREPARING FOR YOUR ADVANCEMENTEXAMINATION

Your examination for advancement isbased on the Manual of Navy Enlisted Man-power and Personnel Classification andOccupational Standards (NAVPERS 18068-D).The sources of questions in this examina-tion Fre given in the Bibliography for Ad-vancement Study (NAVEDTRA 10052). Sinceyour NRCC and textbook are among thesources listed in this bibliography, besure to study both in prepating to takeyour advancement examination. The stand-ards for your rating may have changedsince your course and textbook wereprinted, so refer to the latest editionsof NAVPERS 18068-D and NAVEDTRA 10052.

NAVAL RESERVE RETIREMENT CREDIT

The course is evaluated at 10 NavalReserve retirement points, which will becredited upon satisfactory completion ofthe entire course. These points arecreditable to personnel eligible to receivethem under current directives governing theretirement of Naval Reserve personnel.Credit cannot be given again for thiscourse if the student has previouslyreceived credit tor completing anotherIntroduction to Sonar NRCC or ECC.

COURSE OBJECTIVE

While completing this course, thestudent will demonstrate his understandingof the course materials by correctlyanswering items on the following: proceduresfor advancement to the petty officer leveland the duties and responsibilities of theSTG and STS 3&2; major sound propagationfactors and terms used; types of ASW attacks,stations and communications; on board methodsand components, and functions, of passiveand active sonars; operational capabilitiesand characteristics of auxiliary sonarequipment; duties and qualities of a sonarwatchstander; basic introduction tointegrated fire control systems; evaluationand classification of sonar targets;identification of evasive maneuvers andcountermeasures devices; maintenance,tes*ing, and calibration methods andprocedures; and personnel responsibilityfor security of classified 1,:aterial.

While working on this nonresidentcareer course, you may refer freely tothe text. You may seek advice and instruc-tion from others on problems arising inthe course, but the solutions submittedmust be the result of four own worx anddecisions. You are pro-ibited from re-ferring to or copying the solutions ofothers, or giving completed solutions toanyone else taking the same course.

ii

Naval nonresident career courses may include a variety of items -- multiple-choice, true-falsematching, etc. The items are not grouped by type; regardless of type, they are presented in the sargeneral sequence as the textbook material upon which they are based. This presentation is designedto preserve continuity of thought, permitting step-by-step development of ideas. Some courses usemany types of items, others only a few. The student can readily identify the type of each item (onethe action required of him) through inspection of the samples given below.

MULTIPLE-CHOICE ITEMSEach item contains several alternatives, one of which provides the best answer to the item.

Select the best alternative and erase the appropriate box on the answer sheet.

SAMPLEs-1. The first person to be appointed SecretarTOTTefense

under the National Security Act of 1947 was1. George Marshall2. James Forrestal3. Chester Nimitz4. William Halsey

The erasure of a correct answer is in-dicated in this way on the answer sheet

1.. 3 4

5-1 C I

TRUE-FALSE ITEMSDetermine if the statement is true or false. If any part of the statement is false the state-

ment is to be considered false. Erase the appropriate box on the answer sheet as indicated below.

The erasure of a correct answer is alsoindicated in this way on the answersheet:

SAMPLEs-2. Any naval officer is authorized to corresi51570--

officially with a bureau of the Navy Departmentwithout his commanding officer's endorsement.

MATCHING ITEMSEach set of items consists of two columns, each listing wor

is to select the item in column B which is the best match for the item in column A that is beingconsidered. Specific instructions are given with each set of items. Select the numbers identifyingthe answers and erase the appropriate boxes on the answer sheet.

1

TIFI2 3 4

I

.

s-2

SAMPLETn items s-3 through s-6, match the name of the shipboard officer in column A by selecting from

column B the name of the department in which the officer functions.

A. Officers B. Departments

s-3. Damage Control Assistant 1. Operations Department

s-4. CIC Officer 2. Engineering Department

s-5. Assistant for Disbursing 3. Supply Department

s-6. Communications Officer

The erasure of a correct answer is in-dicated in this way on the answer sheet

1

T2

F

C

3

FM11=1 C

s-5s-6 C

How To Score Your Immediate Knowledge of Results (IKOR) Answer Sheets

1

T4

1

2

I

1

C 9

1211CC

bottom of EACH

Total the number of in-correct erasures (thosethat show page numbers)

>4. for each item and placein the blank space atthe end of each item.

Sample only

Number of boxeserased incorrectly 0-2 3-7

Your score 4.0 3.9

Now TOTAL the column(s) of incorrect erasures and find your score in the Table at theanswer sheet.

NOTICE: If, on erasing, a page number appears, review text (starting on that page) and erase againuntil "C", "CC", or "CCC" 4pears. For courses administered by the Center, the maximumnumber of points (or incorrect erasures) will be deducted from each item which does NOT havea "C", "CC", or "CCC" uncovered (i.e., 3 pts: for four choice items, 2 pts. for three choiceitems, and 1 pt. for T/F items).

Assignment 1

The Sonar Technician; History and Develcpment: Physics of Sound

Textbook, NAVEDTRA 10130-C: Pages 1 thru 40

In this course yoU will demonstrate that learning has taken place by correctly answeringtraining itPms. The mere physical act of indicating a choice on an answer sheet is not in itselfimportant; it is the mental achievement, in whatever form it may take, prior to the physical actthat is important and toward which nonresident career course learning objectives are directed.The selection of the correct choice for a course training item indicates that you have fulfilled,at least in part, the stated objective(s).

The accomplishment of certain objectives, for example, a physical act such as drafting amemo, cannot readily be determined by means of objective type course items; however, you candemonstrate by means of answers to training items that you have acquired the requisite knowledgeto perform the physical act. The accomplishment of certain other learning objectives, forexample, the mental acts of comparing, recognizing, evaluating, choosing, selecting, etc., maybe readily demonstrated in a course by indicating the correct answers to training items.

The comprehensive objective for this course has already been given. It states the purposeof the course in term3 of what you will be able to do as you complete the course.

The detailed objectives in each assignment state what you should accomplish as you progressthrough the course. They may appear-singly or in clusters of closely related objectives, asappropriate; they are followed by items which will enable you to indicate your accomplishment.

A11 objectives in this course are learning objectives and items are teaching items. Theypoint out important things, they assist in learning, and they should enable you to do a betterjob for the Navy.

This self-study course is only one part of the total Navy training program; by its verynature it can take you only part of the way to a training goal. Practical experience, schools,selected reading, and the desire to accomplish are also necessary to round out a fully meaningfultraining program.

Learning Objective: Acquaintthe new ST with the basics ofthe ST rating.

1-1. How does the U. S. prepare itselfto meet a potantial submarinethreat?1. Conducts antisubmarine walfare

(ASW) exercise.2. Revises ASW tactics.3. Evaluates new equipment.4. Does all of the above.

1-2. Nuclear submarines are advantageousin ASW operations because they can1. screen the area for surface ships2. select the best depth for opera-

tions3. conduct operations over wide

ocean areas4. accomplish either 2 or 3 above

1

1-3 Which of the following would beconsidered a general rating?1. STG22. STS33. STSC4. STCM

1-4 Which of the following equipmentsis not normally maintained by anSTS?1. Fire control2. Active sonar3. Passive sonar4. Oceanographic

196

Learning Objective: Explain therewards of being an ST, themethods of advancement, and thesources of information for study.

1-5. What type of ship would an STGmost likely be sent aboard afterhe attends "A" school?1. Destroyer tender2. Destroyer3. Minesweeper4. Submarine

1-6. Which of the following are con-sidered advantages of advancement?1. Higher pay2. Greater prestige3. Getting ahead in chosen career4. All the above

1-7. Which of the following publica-tions should you use when study-ing the Military Requirementsfor Advancement to P03?1. NAVEDTRA 100522. NAVEDTRA 100613. NAVEDTRA 100564. WAVEDTRA 10130

1-8. You can keep abreast of new devel-opments that affect you, your work,and the Navy by being able to1. find up-to-date information

and check that which pertains toyour specialty

2. collect 1D-rsona1 copies ofappropriate technical manuals

3. complete all correspondencecourses that pertain to yourrating

4. complete all correspondencecourses that pertain to thedeck group

1-9. Which of the following is thebasic purpose of all communication?1. Knowledge of own language2. Understanding3. Effective leadership4. All of the above

Use the followng alternativesfor items 1-10 and 1-11.1. NAVEDTRA 1414/12. NAVEDTRA 100523. NAVEDTRA 100614. NAVPERS 8068

1-10. Which publication 7ontains a listof study material 1:or advancementexaminations?

1-11. In what publication will you findan up-to-date list of the quali-fications for advancement?

1-12. Which of the following publica-tions come under cognizance ofCOMNAVCOMM?1. ACPs2. DNCs3. JANAPs4. All of the above

Use the following alternativesfor items 1-13 thru 1-16.1. NWP 02. NWIP 1-43. NWIP 11-204. NWP 16

1-13. Which publication establishesthe basic operational communica-tions doctrine?

1-14. Which publication provides guid-ance for the operation of a COMTAClibrary?

1-15. Which publication lists the mis-sions and characteristics of U.S.Navy ships?

1-16. Which publication contains exper-imental tactics and procedures?

Use the following alternativesfor items 1-17 thru 1-20.1. ATP 12. FXP 13. ATP 28 (USN ADDENDUM)4. AXP 1

1-17. Which publication establishestactics and procedures for con-ducting submarine exercises?

1-18. Which publication contains thebasic concepts and principals ofASW operations?

1-19. Which publication establishestact;.cs and procedures for eval-uating Allied antisubmarineexercises?

1-20. Which publication contains basicmaneuvering instructions?

5 72

1-21. Which of the following actions,if any, is taken when an outdatedquestion is found on an advance-ment examination?1. The old correct answer is

counted.2. All four answers are counted

correct.3. All four answers are counted

wrong.4. None of the above are done.

1-22. What is the purpose of the pro-file sheet?1. To verify your advancement2. To compare overall examination

performance3. To point out weak areas4. To assign a numerical grade

for each section

1-23. How many months must an activeduty STGSN serve to be eligiblefor STG3?1. 42. 6

3. 124. 18

1-24. In what grade does an inactiveduty Sonar Technician requireselection board approval foradvancement?1. E-42. E-53. E-64. E-7

1-25. After you pass the written exami-nation, what other factor willlimit advancement?1. Rating quotas2. Time in grade3. Practical factors4. Duty stations

Learning Objective: Providethe new ST with the backgroundof ASW and submarine.

1-26. It is necessary for a SonarTechnician to be thoroughlyfamiliar with the capabilitiesof enemy submarines in order to1. detect them easier2. hold contact after detection3. aid in hunt and destroy

operations4. do all of the above

3

1-27. A submarine was first used as anoffensive weapon during what war?1. Spanish-American War2. American Revolutionary War3. WW I4. WW II

1-28. The submarine's greatest advan-tage is that1. it is very difficult to sink2. it has more potent weapons3. its crew is smaller than a

surface ship's4. it can operate beneath the sur-

face of the ocean where detec-tion is difficult

1-29. Which of the following statementscorrectly describes the originsof sonar?1. A device called ASDIC was first

developed by America and waslater improved by Britain andrenamed sonar.

2. A device called a sound fathom-eter was first developed byBritain and was designed forA/S use by America and renamedsonar.

3. A device called ASDIC was firstdeveloped by Britain and waslater improved by America andrenamed sonar.

4. A device called a sound fathom-eter was first developed byAmerica and was redesigned forA/S use by Britain and renamedsonar.

1-30. The Skipjack differs from othernuclear submarines primarily inits1. hull design2. ability to carry ballistic

missiles3. type of propulsion plant4. cruising range

1-31. Which of the following groups ofsubmarine classes is arranged inorder of increasing displacement?1. X-1, Seahound, Shrimp2. Shrimp, X-1, Seahound3. X-1, Shrimp, Seahound4. Seahound, X-1, Shrimp

1-32. Which of the following is themain limitation to a modernsubmarine's ability to staysubmerged at sea?1. Fuel shortage2. Equipr.ent failures3. Navigation errors4. Human endurance and supply

space

1 f) 8

1-33 Which of the following submarineswas created to act as a nucleardeterrent to a general war?1. Guppy II2. SSBN3. SSN fast attack (conventional

hull)4. SSN fast attack (albacore hull)

Learning Objective: Aquaint thenew ST with the different typesof missiles used in the Navy andthe types of launching platformsused.

1-41.1-34. The primary mission of the attack

submarine is1. ASW2. barrier patrol3. avoiding detection4. launching missiles

Learning Objective: Provide thenew ST with knowledge of thedifferent types of torpedoesand mines.

Use the following alternativesfor items 1-35 thru 1-38:1. Wire-guided2. Straight-running3. Active acoustic4. Passive acoustic

1-35. Which torpedo sends out pulsesof sound and homes on echoesthat return from the target?

1-36. Which torpedo may be guidedthroughout its run by signalsfrom the launching ship?

1-37. Which torpedo uses preset valuesto Lntercept a target?

1-38. Which torpedo depends upon tar-get noise for guidance?

1-39. When secrecy is required forlaying mines, what deliverymeans is used?1. Aircraft2. Surface craft3. Submarines4. Minelayers

1-40 All of the following mines maybe programed to allow severalships to pass before explodingexcept1. acoustic2. magnetic3. pressure4. contact

4

1 9

Which missile will contain mul-tiple warheads?1. Point defense2. Polaris A33. ASROC4. SUBROC

1-42. The SUBROC is which of the fol-lowing types of missiles?1. Underwater-to-surface2. Surface-to-surface3. Surface-to-air4. Underwater-to-air-to-under-

water

1-43. Which submarine-launched ASWweapon uses an inertial guidancesystem?1. Mk 45 torpedo2. ASTOR3. SUBROC4. ASROC

1-44. At what point is guidance to theSUBROC missile terminated?1. 30 seconds after launch2. When the guidance wire breaks3. At a predetermined height4. At a preset depth

1-45. Which of the following is/arethe principal function/functionsof the destroyer?1. Operating offensively against

surface ships2. Operating defensively against

submarines3. Defending against air attack4. All of the above

1-46. Several postwar Foriest Shermanclass destroyers have been con-verted to DDGs by1. replacing the #2 gun mount

with a TARTAR missile launcher2. replacing the #1 gun mount

with a TARTAR missile launcher3. replacing the after TARTER

missile launcher with a REGU-LAS missile launcher

4. replacing the ASROC launcherwith a SPARROW missilelauncher

1-47. The USS BELKNAP (CG26) displaceshow many tons?1. 22002. 47003. 54004. 6700

1-48. The ASROC missile can deliverwhich of the following payloads?1. Depth charge2. Torpedo3. Either 1 or 2 above4. Wire-guided torpedo

Judge questions 1-49 thru 1-51True or False.

The SUBROC missile with a torpedopayload uses parachute stabili-zation.

1-50. The SUBROC missile with a depthcharge payload uses either para-chute stabilization or fin stabil-ization.

1-51. There are five principal ways tolaunch a torpedo.

1-52. Which of the following is anadvantage of the Mk 46 torpedoover the Mk 44 torpedo?1. Improved propulsive power2. Greater cargo3. Greater speed4. All of the above

1-53. How does MAD (magnetic anomalydetection) equipment detect sub-marines?1. By measuring exhaust trail

gases2. By measuring variations in the

Earth's magnetic lines offorce

3. By active sonar transmission4. By measuring total magnetism

of the submarine

1-54. The Navy's newest fixed-wing ASWaircraft is the1. S2-F2. P-33. SH-2F4. S-3A

5

Learning Objective: Define theelements of and the requirementsfor sound.

1-55. Whether a wave is transverse orlongitudinal depends on the wave's1. components of motion2. frequency3. amplitude4. wavelength

1-56. Sound waves vary in lengthaccording to their1. amplitude2. intensity3. frequency4. strength

1-57. The upper limit of sound vibrationthat can be detected by the aver-age ear is about1. 10,000 vibrations per second2. 15,000 vibrations per second3. 25,000 vibrations per second4. 40,000 vibrations per second

1-58. Sound waves cannot travel througha

1. gas2. liquid3. solid4. vacuum

1-59. The sounds transmittedmodern sonar equipment1970's fall within thedesignated1. sonic2. subsonic3. ultrasonic4. supersonic

by theof therange

1-60. Sonar equipment is designed toconvert returning echoes to a basefrequency of 800 Hz because an800-Hz note1. can be reproduced easily2. is louder than other audible

sounds3. travels farther than other

audible sounds4. is the most pleasing to the

average human ear over longperiods

200

1-61 How much of an increase ordecrease in sound intensityor total power must take placebefore it can be detected bythe human ear?1. 1/42. 1/33. 1/24. 3/4

1-62 Which of the following functionsis best performed by the humanear?1. Discrimination between sounds

of changing intensity2. Detecting changes at low

frequency3. Detecting changes at high

frequency4. Discriminating between sounds

of varying pitch

Judge items 1-63 thru 1-65 True/False.

1-63. The backward movement of a trans-ducer causes an area of low pres-sure or a compression.

1-64. A wavelength is the distance fromone point on a wave to the nextpoint of similar compression.

1-65. A sound wave may travel greatdistances at a high rate ofspeed; however, the particleswithin the medium move very little.

1-66. Why does sound travel fasterthrough water than through air?1. Because air is denser than

water2. Because water offers less

resistance to waves than air3. Because the particles in water

are closer together than theparticles in air

4. Because the particles in waterare farther apart than theparticles in air

1-67. If your sonar equipment has anoperating frequency of kHz, ithas a wavelength in 39°F seawaterof1. 0.37 ft2. 0.,45 ft3. 0.76 ft4. 0.96 ft

1-68. The pitch of sound may be raisedby1. increasing the amplitude of

the vibrations2. decreasing the amplitude of

the vibrations3. decreasing the rate of vibra-

tions4. inpreasing the rate of

vibrations

Learning Objective: Explainthe mathematical principles ofsound measurement.

1-69. What is the third harmonic ofa 1600-Hz tone?1. 3200 Hz2. 4800 Hz3. 6400 Hz4. 8000 Hz

1-70. Your sonar equipment has suffereda loss of 9 decibels in sourcelevel. How much of the originalpower does your equipment haveleft?1. 12.5%2. 15.0%3. 25.0%4. 50.0%

1-71. Which method is most practicalto use for increasing the rangeof your sonar equipment?1. Increasing the source level2. Increasing the receiver sen-

sitivity3. Reducing the local noise4. Reducing the source level

2 0 1

6

Assignment 2

Physics of Sound (continued); Bathythermograph


Learning Objective: Define thevarious noise sources and the typesof noise they emit.

2-1. The foll,,wing three sources ofnoise _;r ::,mr--molecular motion,wind on sea's surface, andsea lift--.re types of1. flow noise2. ambient noise3. thermal noise4. surface agitation noise

2-2. Which of the following noises isthe result of molecular motionin the medium caused by tempera-ture?1. Thermal2. Biological3. Flow4. Propulsion

2-3. Which o- the following is a morereliable measure of expectedambient noise?1. Windspeed2. Sea state3. Surface temperature4. Time of day

2-4. Which of the following noisesthat may be produced in a surfaceship decreases the ability of thesurface ship to detect underwatertargets but, because it is notradiated appreciably, has littleeffect on the ability of thetarget to detect the surfaceship?1. Flow noise2. Cavitation noise3. Main propulsion noise4. The rat-a-tat-tat of a chipping

hammer

2-5. How does a change in flow noisefrom laminar to turbulent affectnoise intensity?1. Increases sharply2. Increases gradually3. Remains the same4. Decreases

2-6. Flow noise and cavitation noiseare both produced by the move-ment of an object through water.One way they differ is that cavi-tation noise occurs1. as soon as the object starts to

move2. before flow noise occurs3. when the pressure around the

moving object fluctuates4. when air bubbles form around

the moving object

2-7. As a propeller rotates in water,it will at different speeds ofrotation produce (A) sheet cavi-tation, (B) flow noise, and (C)tip cwitation. In what sequencewill tnese three types of noisebe produced?1. B, ,r C2. B, C, A3. C, A, B4, C, B, A

2-8. Your submarine commences cavitatingat a depth of 100 feet when thespeed exceeds 6 knots. What hap-pens to the amplitude and fre-quency of the noise when the depthis increased to 200 feet and thespeed remains the same?1. Amplitude increases, frequency

decreases2. Amplitude increases, frequency

increases3. Amplitude decreases, frequency

increases4. Amplitude decreases, frequency

decreases

7

202

2-9. How does dynamic imbalance inmachinery become a sonar noiseproblem?1. Leakage currents are creatud.2. Static noises are fed into

the receiver.3. Vibration is changed to

acoustic energy.4. The imbalance causes flow

noise.

2-10. What type of noise is made whenthe anchor windlass is used?1. Surface agitation2. Thermal noise3. Ambient noise4. Self-noise

2-11. Which of the follwing is themost probable cause of a 60-Hznoise generated within thesonar equipment itself?1. A badly balanced shaft2. Improperly shielded cable3. Portable power tools4. The fire and flushing pumps

2-12. Which types of marine lifecould be mistaken for hydro-plane noise?1. Whale2. Porpoise3. Seal4. Shrimp

2-13. When you hear a noise made bymarine life that sounds similarto burning brush, the depthof the mirine life is1. less than 30 fathoms2. 100 fathoms or more3. 300 fathoms4. 1000 fathoms

2-14. Which of the following marinelife produce a sound similarto that of someone hammering?1. Porpoises2. Snapping shrimp3. Sperm whales4. Blackfish

Learning Objective: Define anddiscuss the controlling factorsof sound, their effects on thetransmission of sound, and methodsof recognizing the factors.

2-15 Which of the following trans-mission losses is independentof frequency?1. Attenuation2. Absorption3. Scattering4. Divergence

2-16. The attenuation (decreasein strength) of a sound beam iscaused by the combined effectsof1. absorption and scattering2. absorption and reflection3. reflection and refraction4. refraction and scattering

2-17. Reflection of sound energy occursanytime the sound medium changesin1. thickness2. shape3. density4. temperature

2-18. What happens to sound energythat is transmitted from anunderwater source when the soundreaches the surface of the water?1. Most of it continues on into

the air.2. All of it continues on into

the air.3. Most of it is reflected down-

ward into the water.4. All of it is reflected down-

ward into the water.

2-19. In general, what kind of shallowbottom causes the least trans-mission loss?1. Smooth sand2. Rough gravel3. Soft mud4. Rough rocks

2-20. When you transmit sound energyinto the water, the many echoesyou receive from sources suchas the water mass, the surface,and the bottom of the sea, arecalled1. reverberations2. refractions3. absorptions4. diversions

2038

2-21. What causes volume reverberations:1. Sound energy reradiated by

small particles2. Surface and bottom reflections3. Marine life4. All of the above

2-22. Which of the following conditionswill cause the highest reverbera-tion levels?1. Flat surface and deep water2. Flat surface and smooth bottom3. Rough surface and rocky bottom4. Rough surface and smooth bottom

2-23. Two things that happen to thesound beam when sound is trans-mitted into water are: (A) itscross sectional area becomeslarger as the sound moves outfrom the source, and (B) itsdirection is affected by waterpressure, salinity, and changesin temperature. What are eachof these two effects called?1. (A) scattering, (B) refraction2. (A) divergence, (B) refraction3. (A) scattering, (B) reflection4. (A) divergence, (B) reflection

2-24. When a beam of sound passes fromone medium of high temperatureinto a medium of low temperature,the sound beam is1. reflected2. refracted3. absorbed4. scattered

2-25. Which of the following soundsindicates that a sonar beam isbeing quenched?1. Hollow booming2. Sharp pinging3. Shrill screech4- Dull thudding

2-26. What is the most important factoraffecting the speed of sound inwater?1. Temperature2. Pressure3. Salinity4. Chemical composition

2-27. How is the speed of a sound wavetraveling through water affectedby water temperature and pressure?1. Its speed increases when tem-

perature increases and alsowhen pressure increases.

2. Its speed decreases when tem-perature increases and alsowhen pressure increases.

3. Its speed increases when tem-perature increases anddecreases when pressureincreases.

4. Its speed decreases when tem-perature increases and increaselwhen pressure increases.

2-28. Which factor controlling the speedof sound varies in direct pro-portion to the water depth?1. Salinity2. Pressure3. Temperature4. Density

2-29. Which figure in the textbook showsthe behavior of a sonar beamwhen it is influenced by waterpressure only?1. 3-152. 3-263. 3-174. 3-18

2-30. Which figure in the textbookrectly shows the behavior ofsonar beam in water that hascontinuous negative thermalgradient?1. 3-152. 3-163. 3-174. 3-18

cor-aa

2-31. A submarine using the layer effectfor protection will find themost protection under conditionssimilar to those represented inthe text book by figure1. 3-152. 3-163. 3-174. 3-18

2-32. Which, if any, of the followingthermal gradients will producelayer depth at the depth of max-imum temperature?1. Positive2. Negative3. Isovelocity4. None of the above

2049

2-33. Echo ranging in shallow wateris difficult due to the soundbeing1. scattered2. absorbed3. reflected4. refracted

2-34. What is the approximate depthof a submarine if it passes undera sonar beam so that contact islost at 100 yards?1. 100 ft2. 200 ft3. 300 ft4. 400 ft

2-35. In a layer of water that providesa sound channel, what is therelationship between the watertemperatures at (A) the upperlimit of the layer, (B) thelower limit of the layer, and(C) the axis of the layer?1. A and B are the same, C is

cooler than A and P.2. A and B are the same, C is

warmer than A and B3. A and C are the same, B is

cooler than A and C4. A and C are the same, B is

warmer than A and C

2-36. What condition must exist inorder to have a convergencezone effect?1. A negative gradient at the

surface2. A sound channel axis between

350 fathoms and 500 fathoms3. A sound source in the sound

channel axis4. A water depth of approximately

2000 fathoms

2-37. The principle by which an object'smotion changes the pitch of asound that comes from theobject is called the1. bounce principle2. frequency shift principle3. convergence principle4. doppler

10

2-38 Earlier in this assignment, therelationship between a sound'sfrequency, its velocity, and itswavelength was discussed. Oneversion of their relationship(F = V) applies very closely

A

to the discussion on the effectsof motion on sound. Compressingthe sound wave is the same asshortening the sound's wavelength.What effect has an object's motionon the wavelength, and thu onthe frequency of a sound that iscoming from the'object, if theobject is moving away from you?1. The wavelength increases and

the frequency goes up.2. The wavelength increases and

the frequency goes down.3. The wavelength decreases and

the frequency goes up.4. The wavelength decreases and

the frequency goes down.2-39. Assume that you pick up a target

on your sonar equipment. Whatmay you decide about the targetif the pitch of the echo is lowerthan the pitch of the reverbera-tions?1. The target is approaching your

ship.2. The target is moving away from

your ship.3. The target is maintaining the

same position relative to yourship.

4. The target is moving at con-stant speed.

2-40. A report of "Doppler moderate,up," indicates that a targetis approaching your ship with aspeed component of about1. 2 knots2. 3 to 6 knots3. 7 to 9 knots4. 10 knots

2-41. Which of the following may givea sharp echo with doppler?1. Kelp bed2. Fresh submarine ,.ake3. Whale4. Riptide

2-42. A poor quality echo is reflectedfrom a stern aspect targetbecause1. the target area is small2. the echo comes from multiple

sources3. wake interference reduces the

signal4. of all of the above factors

205

2-43. What action should you take whenyou hear unusual sounds while onwatch?1. Identify the sound, then

report it.2. Report every unusual sound

immediately.3. Report it only if it is a

submarine.4. After a reasonable period for

identification, make yourreport.

Learning Objective: Explain theeffect of varying oceanographicconditions on the transmissionof sound.

2-44 What single factor has the mostpronounced effect on the speed ofsound wave travel through water?1. Depth of water2. Salinity of water3. Water temperature4. water pressure

Learning Objective: Explainthe bathythermographs currentlyused in the Navy, includingtheir operational characteristics.

2-48. What is the sound velocity rangeof the AN/BQH-1A?1. 4000 - 4800 fps2. 4200 - 5100 fps3. 4600 - 5100 fps4. 4800 - 5100 fps

2-49. A series of lines on the recorderchart of the AN/BQH-1A depth-sound speed measuring set aida moving submarine in maintain-ing its trim. What are theselines called?1. Isothermal2. Isometric3. Isoballast4. Isodynamic

2-50. Sensitivity of the velocity-measuring portion of theAN/BQH-1A is sufficient toindicate change-. in sound velocityof1. 0.1 fps2. 1 fps3. 3 fps4. 5 fps

2-45. How will an increase in the watertemperature from 73°F to 74°Faffect the speed of sound passingthrough the water?1. The speed of sound will increase

approximately 6 feet per second.2. The speed of sound will increase

approximately 2 feet per second. 2-51.3. The speed of sound will

decrease approximately 4 feetper second.

4. The speed of sound willdecrease approximately 12 feetper second.

2-46. What would be the relationshipof temperature verses depth ina thermocline?1. The temperature remains constant

with depth.2. The temperature decreases with

depth.3. The temperature varies errati-

cally within the thermoclineas depth increases.

4. The temperature remains constantabove and below the thermocline.

2-47. What are the two effects a ther-mocline has on sound energy thatcause a sound beam's direction tobe distorted?1. Reflection and reverberations2. Convergence and refraction3. Convergence and reverberations4. Reflection and refraction

11

Two sound heads, one mounted onthe keel and the other on thesail of a submarine, are usedto get accurate informationconcerning changing thermalgradients affecting buoyancyduring diving operations.Which sound head is used whenthe submarine is (A) ascendingand (B) diving?1. Both A and B, upper2. Both A and B, lower3. A lower, g, upper4. A uPPer, B lower

2-52. The AN/BQH-1A sonar set measuresthe velocity of sound in waterby1. correlating the several known

factors2. timing a transmitted pulse

between a transmitter anda receiver

3. timing a transmitted pulsefrom another submarine

4. determining echo intensityfrom a transmission

206

The depth scale of the AN/BQH-1A 2-59.depth-sound speed measuring set iscalibrated for a maximum depth of1. 700 ft2. 800 ft3. 1500 ft4. 4800 ft

2-54. One precaution you take when youoperate the BQH-1A depth-speedmeasuring set is to avoid1. using the recorder unit2. energizing the lower sound

head before the submarine iscompletely submerged

3. energizing the upper sound headbefore the submarine is com-pletely submerged

4. selecting an overlapping depthscale

2-55 When you shift from one 'ound headof the BQH-1A depth-sound speedmeasuring set to another head,what information do you receivein addition to the velocity ofsound?1. Depth under the keel2. Distance to the surface3. Amount of radiated heat at the

sound head in use4. Difference in depth between

the two sound heads

2-56. One emergency feature of theAN/BQH-1A is that the1. depth may be read if the sound

neads fail2. sound velocity is always shown3. depth reading is always shown4. depth and velocity circuitry

are combined

2-57 What is the maximum operatingdepth of the SSXBT?1. 1000 ft2. 1500 ft3. 2000 ft4. 2500 ft

What actuates the release mecha-nism on the SSXBT, causing theprobe to descend?1. Atmospheric pressure2. Water pressure3. Commands from the launching

ship4. A preset timer

2-60. What component of the surface shipexpendable BT senses the changingtemperatures?1. Thermometer2. Sound head3. Thermistor4. Bourdon tube

2-61. The surface ship expendable BTrecorder begins marking tempera-ture when the1. cannister is loaded into

the launcher2. probe strikes the water3. wire unreels from the probe4. wire unreels from the cannister

2-62. What feature of the surface shipexpendable BT allows a verticaldescent of the probe?1. Simultaneous unreelinc of the

wire from the cannistar probe2. Spin stabilization of the

probe3. The weight of the probe4. The speed of the probe

2-63. What is the maximum operatingdepth of the surface ship expend-able BT?1. 1000 ft2. 1500 ft3. 2000 ft4. 2500 ft

2-58. Approximately how much time isrequired to complete a temperature 2-64profile after launching the SSXBTdown to its maximum operatingdepth?1. 1 min2. 2 min3. 3 min4. 4 min

2 07

12

Learning Objective: Discusshow information derived fromthe BT may be used in ASW work.

Which of the following tempera-ture gradients will usually resultin short target ranges?1. Negative2. Positive3. Isothermal4. Mixed

2-65. Which of the following thermalgradients is usually observedin coastal waters?1. Negative2. Positive3. Isothermal4. Mixed

2-66. What causes the phenomenon knownas afternoon effect?1. Tides2. The sun3. Tradewinds4. Waves

13

2-67. What will usually happen to thetemperature of the water nearthe surface after the sun sets?1. Positive gradients will become

isothermal.2. Negative gradients will become

isothermal.3. Negative gradients will become

positive.4. Positive gradients will become

negative.

208

Assignment 3

Bearings and Motion; Principles of Sonar


Learning Objective: Providethe new ST with the basicmechanics of bearings andranges.

3-1. Which of the following is used asa reference for computing truebearings?1. North-south axis2. True north3. Geographic north4. Magnetic north

3-2. What information do you need tolocate accurately an underwaterobject in relation to your ship?1. The direction of true north2. A geographical reference point3. The object's direction and

distance4. The depth of the water

3-3. Which of the following results maybe obtained from a speedy determi-nation of correct bearing andrange?1. A correct solution from the

computer2. The exact target location3. A successful attack4. All of the above

3-4. How should you report a range of2350 yards?1. Range two thousand three hundred

and fifty2. Range twenty three fifty3. Range two three five oh4. Range two three five zero

14

209

3-5. A comparison of the uses of trueand relative bearings in sonaroperating procedure reveals that1. relative bearings are used as

long as the ship's gyrocompassis operating properly

2. relative bearings are used onlywhen the ship's gyrocompassfails

3. true bearings are used onlywhen the ship's gyrocompassfails

4. true bearings are used at alltimes, regardless of the con-dition of the ship's gyrocompass

['OURSHIF

A TARGET

V B

Figure 3A.--Bearings.

TARGET

A

3-6. What is the true bearing of targetA in figure 3A?1. 000°2. 090°3. 180°4. 270°

3-7. What is the true bearing of targetB in figure 3A?1. 000°2. 090°3. 180°4. 270°

3-8. The relative bearing of target Ain figure 3A is1. 000°2. 090°3. 180°4. 270°

3-9. The relative bearing of target Bin figure 3A is1. 000°2. 090°3. 180°4. 270°

Learning Objective: Famil-iarize the new ST with typesof bearing and range indica-tors.

Information for items 3-10 and"F 3-11: Bearing indicators like

th,1 one in figure 5-5 in your text-book are used to provide remotestations with true and relative sonarbearings. In these two items, thetwo dials on the indicator that moveare referred to as dial A and dial B,dial A being the one that has thediamond indicator, and B being theinner dial--the one labeled Gyro-Compass Repeater.

3-10. How will the positions of thedials in figure 5-5 change toindicate that your ship is oncourse 045° and that yoursonar is trained on the portbeam?1. Both A and B will move clock-

wise 90°.2. Both A and B will move counter-

clockwise 90°.3. A will move counterclockwise

135° and B will remain in itspresent position.

4. B will move clockwise 90° and Awill remain in its presentposition.

15

3-11. How will the positions of the dialsin figure 5-5 change to indicatethat your ship is on course 315°and that your sonar is trained onyour starboard beam?1. B will move clockwise 90° and

A will move clockwise 045°.2. Both A and B will move counter-

clockwise 90°.3. A will move counterclockwise

90° and B will remain in itspresent position.

4. B will move clockwise 90° andA will remain in its presentposition.

Learning Objective: Acquaintthe new ST with the manipula-tion of bearings.

3-12. If your ship is ontrue when you makeat 180° true, whatbearing reading online indicator?1. 000°2. 090°3. 180°4. 270°

course 090°sonar contactis the trueyour stern

3-13. Your ship is on a heading of 180°true and alters course right to270° true. What change occurs tothe stern line indicator?1. Rotates clockwise and stops on

270°2. Rotates counterclockwise and

stops on 090°3. Rotates clockwise and stops

on 090°4. No change

3-14. If your ship's stern is 090° truewhen she suffers a gyrocompasscasualty, what is the stern lineindicator reading after thecasualty?1. 000° relative2. 090° true3. 180° relative4. 270° true

3-15. If you are headed for a sonarcontact at 135° true when a gyro-compass failure occurs, what mustyou do with the console cursor toremain on target?1. Turn it left 45°.2. Turn it left 135°.3. Turn it right 45°.4. Turn it right 135°.

210

3-16. What is the true bearing of atarget if your ship is headed2700 true and the target bearingis 270° relative?1. 000°2. 090°3. 180°4. 270°

3-17. Assume that a target is movingdue east and that your destroyeris approaching it from the south.At a range of 700 yards, the targetis due north of your ship and theconning officer orders a course of045° to take a lead on the target.After the change in course, thecursor will be moved to show arelative bearing of the target ofabout1. 000°2. 045°3. 180°4. 310°

3-18. Your ship is on course 253° trueand the target bears 1090 relative.What is the true target bearing?1. 002°2. 107°3. 144°4. 182°

3-19. Your ship is on course 035° trueand the target bears 334° true.What is the target's relativebearing?1. 009°2. 119°3. 154°4. 299°

3-20. The relative motion of a targetis the motion the target appearsto have if you consider your shipas being1. stopped (dead in the water)2. on course 00003. on course 18004. on course 090° or 270°

3-21. Your ship is on course 170° andyou have the following bearingand range information on a sub-marine:

Time0010001500200025

Bearing220°215°209°200°

Range8000675057004800

What will your ship do in relationto the target?1. Pass ahead2. Pass astern3. Pass over4. Pass parallel

Learning Objective: Acquaintthe new ST with advance andtransfer.

3-22. What is the distance along the oldcourse that a ship covers betweenthe time that right rudder isapplied and the time that the shipis steadied in its new course?1. Drag2. Cover3. Transfer4. Advance

3-23. The distance your ship moves atright angles to the originalcourse after rudder is appliedis called1. transfer2. advance3. drift4. set

3-24. The bearing drift of a targetindicates the direction of targetmovement if your ship is on asteady course at a constant speedand the relative bearing to thetarget is approximately1. 000°2. 045°3. 090°4. 315°

2

16

Learning Objective: Pointout to the new ST therelationship betweenbearings and doppler.

Figure 3B.--Aspect and Doppler.

In figure 3B the submarine is inthe center on course 000°, speed

four knots.

3-25. What is the doppler and targetaspect when your ship is atposition "A"?1. Up doppler, port bow aspect2. No doppler, port bow aspect3. Down doppler, starboard bow

aspect4. No doppler, port beam aspect

3-26. What is the doppler and targetaspect when your ship is stoppedat position "B"?1. Up doppler, starboard beam

aspect2. Down doppler, starboard beam

aspect3. No doppler, aspect undetermined4. No doppler, starboard quarter

aspect

3-27. What is the sequence of dopplerwhen your ship has circled thetarget clockwise from position "A"to "B" and has arrived at position"C"?1. No, up, down2. Up, no, up3. No, no, down4. Up, no, down

17

212

3-28. Your ship is headed directlytoward a target that has rightbearing drift and up doppler.What is target aspect?1. Port bow2. Starboard bow3. Direct bow4. Port beam

3-29. If you use the quadrant method ofdetermining target aspect as showl,in figure 5-13 of your Lextbook,a dotted line representing a portbow aspect will be located inquadrant1. A2. B3. C4. D

3-30. Your ship is on course 195° true,the submarine bears 187° true, andthe bearing is steady with LE. dop-pler. What maneuver has the sub-marine performed if the dopplerchanges to down and the bearingdrifts left?1. Turned right2. Turned left3. Turned right and stopped4. Turned left and backed down

3-31. To determine target angle, youmust effectively put yourself onthe target. You perform thisoperation in the target angleformula by applying 180° to1. the target's true bearing2. the target's relative bearing3. own ship's course4. the target aspect

3-32. You are on a surface ship headed000° and a submarine on your star-board beam is also headed 000°.How will you report target angle,and how will the submarine sonaroperator report angle on the bow?1. 090°, port 902. 090°, starboard 903. 270°, port 904. 270°, starboard 90

3-33. Your contact is on course 275°true, bearing 176° true. Whatis the target angle?1. 081°2. 099°3. 261°4. 289°

3-34. Your target is on course 334° andthe target bearing is 135°. Whatis the target angle?1. 161°2. 315°3. 341°4. 351°

3-35. Your submarine has a contactbearing 260° true on course 300°true. What is the angle on thebow?1. 180°, starboard2. 160°, port3. 140°, port4. 140°, starboard

Learning Objective: Explainthe basic principles ofsonar, both active andpassive.

3-36. What target information can beexpected from passive sonarsystems?1. Estimated bearing and accurate

range2. Accurate bearing and estimated

range3. Accurate bearing and range4. Estimated bearing and range

3-37. What device is used to convertsound energy into electricalenergy?1. Transmitter2. Transducer3. Receiver4. Loudspeaker

3-38. The main function of modern sonarreceivers is to provide signalsfor the1. loudspeaker and for the video

indicators2. microphone

speaker3. transducer

indicators4. transducer

phone

and for the

and for the

and for the

loud-

video

micro-

3-39. What advantage does modern activesonar have over searchlight sonar?1. The ability to maintain contact

on a maneuvering target2. The ability to search quickly

all around the ship3. The ability to see a 360° video

presentation4. All of the above advantages

000°

180°

Figure 3C.--Sonar CRT display.

Refer to figure 3C and use thefollowing alternatives for items

3-40 thru 3-42.1. Target motion2. Target distance3. Target bearing4. Target size

3-40. What target information is deter-mined by dimension A?

3-41. What target information is repre-sented by dimension B?

3-42. What target characteristic do youestimate from dimension C?

21318

Learning Objective: Describetransducers and hydrophonesand their functions.

3-43. The magnetostrictive process ofsignal conversion is caused by1. changes in the dimension of

metals placed in a magneticfield

2. changes in the dimension ofcrystals placed in a magneticfield

3. polarization of crystals4. polarization of ceramics

3-44. What is used to prevent frequencydoubling in a magnetostrictivetransducer?1. Mica insulation2. Wire coils3. Castor oil4. Metal laminations

3-45. Magnetostrictive transducerelements used in scanning sonarare composed of1. nickel tubes2. nickel laminations3. ammonium dihydrogen phosphate4. barium titanate

3-46. The maintenance of the close con-tact feature of the sonar unitcauses the sound beam to1. bend upward2. bend downward3. increase in power4. expand horizontally

3-47. What type of material is used ina piezoelectric transducer?1. Magnets2. Nickel laminations3. Wire coils4. Crystals

3-48. Which of the following crystals isrelatively insensitive to tempera-ture changes?1. ADP2. Rochelle salt3. Tourmaline4. Lithium sulphate

3-49. Electrostrictive transducerelements are composed of1. nickel tubes2. nickel laminations3. ADP crystals4. ceramics

3-50. Electrostrictive transducer ele-ments are polarized by using1. permanent magnets2. laminated elements3. wire coils4. high voltage

Learning Objective: Discussthe modern active sonartheory, including transmis-sion, reception, and preeen-tation.

Use the following alternatives foritems 3-51 thru 3-53:1. Control-indicator2. Receiver-scanner3. Transmitter4. Audiofrequency amplifier

3-51. What unit contains the circuitrythat initiates and determines thelength of the transmitted pulse?

3-52. In what unit is the transmittedpulse modulated to the operatingfrequency?

3-53. In which unit is the incoming echosignal strength increased beforeit reaches the scanning switches?

Reverberations are used as thepitch reference for echo doppler

discrimination. When your ship is mov-ing, the change in wavelength caused bythe ship's motion causes the reverbera-tion pitch to be higher from the bowthan from the beam or stern. The ownship's doppler nullifier (ODN) circuitryuses own ship's speed and sonar bearinginputs to correct this difference. Whenin use, the ODN circuitry causes thereverberations received by a ship inmotion to be of the same pitch as thosereceived by a rThip that is drifting.

3-54. When your sonar equipment has ODNcircuits, how will the frequencyof an echo from a stopped submarine. .y if you gain contact on yourbow.and pass it astern?1. Change from high to low2. Change from low to high3. Increase steadily4. Remain the same

19

214

3-55. When a target echo shows at extreme 3-57.range on the cathode ray tube ofyour sonar, what is the relativevalue of the sawtooth voltage?1. Maximum2. Three-fourths3. One-half4. Minimum

3-56. When, during the sweep cycle, isthe cursor produced on the scope?1. During the first half2. During the second half3. Between sweeps4. Continuously

OWN SHIP'SCOURSE

\\\

\

AUDIOAMPUFIER

BAND PASSFl LTER

TRAININGMECHANISM

AUTOMATICTARGET

FOLLOWER

BEARINGDEVIATIONINDICATOR

B D

SOUNDSOURCE

Figure 3D.--Single-line hydrophonesystem.

The sonar system shown in figure3D is capable of accurately deter-mining the sound source's1. aspect2. range3. speed4. bearing

3-58. Which of the following items ofinformation will be given by thebearing deviation indicator (BDI)of the sonar system in figure 3D?1. Own ship's course must be

changed to starboard for maxi-mum signal reception.

2. Hydrophone must be trainedright for minimum phase differ-ence.

3. Hydrophone must be trainedright for maximum phase differ-ence.

4. Hydrophone must be trainedleft for minumum phase differ-ence.

3-59. In figure 3D, the automatic targetfollower (ATF) serves to relay1. training signals to the RLI2. training signals to the train-

ing mechanism3. audible frequency target signals

to the audio amplifier4. audible frequency target signals

to the filter

3-60. What type of sonar is illustratedin figure 6-10 of the textbook?1. Conformal passive array2. Circular passive array3. Cylindrical hydrophone array4. Single-line hydrophone

3-61. The compensator switch in an arraytype of passive sonar system pro-vides a function most similar tothat provided by a single-linehydrophone system's1. RL1 meter2. audio amplifier3. band pass filter4. training mechanism

3-62. What reference point is used inpassive array sonar to determinetarget bearing?1. Center of the rotor plate2. Center of the stator plate3. Center of the compensator

switch4. Center transducer element

21520

3-63. The purpose of the lag linesthe array sonar described intextbook is to1. delay the signal from the

hydrophones farthest from thesound source

2. speed up the signal from thehydrophones farthest from thesound source

3. delay the signal from the hydro-phones nearest to the soundsource

4. speed up the signal from thehydrophones nearest to thesound source

inyour

3-64. The audio amplifier input signalis strongest when the1. output of the lag lines is in

phase2. output of the lag lines is not

in phase3. stator plate is centered4. preamplifier output is not in

phase

3-65. Which of the following advantagesdo you have with variable depthsonar that you do not have withhull-mounted transducers':1. Generally longer ranges2. More accurate classification3. Faster search speeds4. The ability to get below

thermal layers

Learning Objective: Discussthn depth sounder, includingits use and operationalcharacteristics.

3-66. For what purprse is the AN/UQN-1designed, ane, what operatingprinciple does it use?1. To determine target depth by

solving a right triangle formula,using slant range and depressionangle

2. To determine depth of the seaby bouncing sound pulses off thebottom of the sea

3. To determine target bearing bymonitoring target noise

4. To record target range bymarking chemically treatedpaper

21

216

3-67. On which of the five range scaleson the AN/UQN-1 does the scopeprovide a visual presentation?1. The 100 ft scale only2. The 100 ft and 100 fathom

scales only3. The 100 fathom and 600 fathom

scales only4. On all five scales

3-68. What depth is indicated by thelast trace mark on the chart infigure 6-17 in your textbook?1. 400 feet2. 430 feet3. 4000 feet4. 4300 feet

3-69. You are facing the chart on anAN/UQN-1 depth sounder. In whatdirections do the stylus and thepaper travel?

Stylus Paper1. Up right2. Up left3. Down right4. Down left

3-70. Which of the following can becontrolled by reducing the gainon the AN/UQN-1 depth sounder?1. Solid line in shallow water2. Reverberations3. Multiple echoes4. All of the above

3-71. Before you place the AN/UQN-1depth sounder in a transmittingmode of operation, you shouldallow it to warm up in standbyfor a minimum period of1. 10 seconds2. 20 seconds3. 30 seconds4. 60 seconds

3-72. Depressing the mark button on theAN/UQN-1 depth sounder causes a1. single pulse of sound energy

to be transmitted2. bright spot to appear on the

scope3. solid circle to appear around

the scope's edge4. solid line to appear on the

chart for record purposes

3-73. What are the two modes of soundtransmission (keying) provided bythe AN/UQN-1?1. AUTOMATIC and SINGLE PING2. MARK and RECORD3. AUTOMATIC and MARK4. RECORD and SINGLE PING

Assignment 4

Principles of Sonar (continued); Basic Fire Control; Communications


Learning Objective: Discussthe tape recorder, includingits use and operational charac-teristics.

4-1. What are the sound inputs to each ofthe tracks of the AN/UNQ-7?1. Both tracks are fed underwater

sound information.2. One track is connected to the

sonar equipment; the otherrecords sound from the sonaroperator's station.

3. Both tracks are fed informationdirectly from the sonar equip-ment.

4. Both tracks record sound from thesonar operator's station.

4-2. The purpose of the microphone in theAN/UNQ-7 tape recorder is to1. transfer the electrical sound

signals onto the tape2. convert the magnetic sound energy

on the tape to electrical soundenergy

3. convert sound waves in the air toelectrical sound energy

4. increase the strength of themagnetic field on the tape

4-4. In what sequence does the magnetictape in the AN/UNQ-7 pass the threemagnetic heads during the RECORDmode of operation?1. Erase, record, reproduce2. Erase, reproduce, record3. Reproduce, record, erase4. Reproduce, erase, record

4-5. What happens to the tape when theerase head of an AN/UNQ-7 recorderis energized?1. The top track is erased and upon

rewinding the 1-ottom track iserased.

2. Either the top or bottom trackmay be erased as selected.

3. Either top or bottom or bothtracks may be erased as selected.

4. Both tracks are.always erasedsimultaneously.

4-4;. What is one reason that you shouldrecord critical sonar informationat 15 inches per second when youare recording with the AN/UNQ-7?1. To use as little tape as possible2. To permit later analysis at lower

speeds3. To decrease the number of

unwanted noises recorded4. To permit later analysis at

higher speed4-3. What is a material called that is

capable of being made easily magnetic 4-7.and is also able to lose its magnet-ism easily?1. Antimagnetic2. Diffusible3. Permeable4. Sensitive

21722

What tape speed should be used fora high-quality recording?1. 3 3/42. 7 1/23. 154. Any of the above

4-8. The record safety interlock switchon the AN/UNQ-7 prevents1. obtaining an electrical shock

while working on the recorder2. obtaining an electrical shock

while threading the recorder3. accidental recording from the

remote control unit4. accidental recording at the

main unit

4-9. While you are playing a tape on theAN/UNQ-7 tape recorder, someoneplaces the toggle switch on theremote control unit to RECORD.What will happen and why?1. The tape will continue to play

back because the record inter-lock is not engaged.

2. The tape will continue to playback because reproduce takesprecedence over record.

3. The tape will be erased becausethe record interlock is engaged.

4. The tape will be erased becauserecord takes precedence overreproduce.

4-10. How is the operator at a remotecontrol unit warned when there are5 minutes or less of recordingtime remaining on the tape on theAN/UNQ-7 recorder?1. The RECORD lamp goes out.2. The RECORD lamp flashes.3. The STANDBY lamp goes out.4. The STANDBY lamp flashes.

Learning Objective: Describethe major elements of a typicalunderwater fire control system.

4-12. Which of the following main ele-ments of a fire control systemreceives target data from sonar?1. Stabilization computer2. Attack console3. Positive indicator4. Relay transmitter

4-13. Which of the following puts outcorrections to own ship's course?1. Attack console2. Positive indicator3. Relay transmitter4. Stabilization computer

4-14. Which piece of equipment allowsthe commanding officer to approvethe payload selection?1. Attack console2. Position indicator3. Relay transmitter4. Stabilization computer

Learning Objective: Identifythe ASW weapons used againstsubmarines in today's Navy.

4-15. What is the main shipboard weaponcurrently used for action againstsubmarines?1. Stern dropped depth charge2. ASROC torpedo3. Mk 32 time launched torpedo4. Lamps delivered depth charge

4-16. Modern antisubmarine torpedoes arebetter than early models becausethe newer torpedoes1. go faster2. go farther3. are more maneuverable4. have all of the above advantages

4-11. Fire control systems are used to1. maintain target contact by using 4-17.

echo ranging sonar equipment2. evaluate target-generated noise

to maintain sonar contact3. maintain contact by use of

active and passive sonar equip-me:it

4. collect and translate informa-tion into weapon firing data

23

218

A typical torpedo runs in whattype of pattern?1. Circle right2. Circle left3. Helical4. Straight-running

4-18. All of the following torpedoes aresuitable for antisubmarine workexcept1. straight-running contact2. active acoustic-homing3. passive acoustic-homing4. wire-guided

Learning Objective: Describethe various phases used duringthe conduct of ASW.

4-19. Which of the following steps in thedestruction of a target is notordinarily considered a part ofthe fire control problem?1. Target detection2. Target tracking3. Target movement analysis4. Ballistic computation

4-20. Both initial detection and trackingof a completely submerged submarineare commonly accomplished by1. visual sighting2. search radar3. sonar equipment4. fire control computing equipment

4-21. Which of the following devices ismost likely to be used by a sub-marine in tracking a surfacetarget?1. Sonobuoys2. Passive sonar3. Active sonar4. Magnetic equipment

4-22. The goal of the tracking phase ofthe fire control problem is toaccurately determine the target's1. rate of relative motion2. rate of descent3. course4. speed

4-23. A submarine's true course and speedis plotted on the dead-reckoningtracer by using information from1. own ship's course2. own ship's speed3. sonar range and bearing4. all of the above sources

4-24. In analyzing target motion, thesurface sonar fire control systemmust first combine sonar slantrange with the target's known orestimated depth. By combiningthese two quantities, the systemdetermines the1. vertical range to the target2. horizontal range to the target3. target's course4. target's speed

4-25. Why is it desirable to stay as faraway from an enemy submarine aspossible and still maintain con-tact?1. To obtain more accurate sonar

information2. To obtain more accurate fire

control solution3. To keep away from your own

weapons4. To keep the enemy from shooting

at you

4-26. Which of the following actionswould be considered part of thedestruction phase of an ASW attack?1. Any indirect action forcing a

submarine to surface2. The launching of an ASROC

missile3. Use of the computed ballistic

solution4. All of the above actions

Learning Objective: Point outthe variables and fire controlsymbols used by fire controlsystems.

4-27. Which of the following variableswould most likely cause a missduring an ASW attack?1. Own ship's course and speed

change2. Target course and speed change3. Own ship's roll and pitch4. Target's roll and pitch

4-28. The stable element is used infire control to correct variationintroduced by1. changes in own ship's speed2. changes in own ship's heading3. own ship's roll and pitch4. changes in target bearing

21924

4-29. In which of the following planesdoes the FC computer computesolutions?1. Horizontal2. Vertical3. Deck4. All of the above

4-30. Which of the following referencesis used to measure the number ofdegrees between two verticalplanes?1. Relative bearing2. Roll3. Pitch4. Target depth

4-31. Detailed information on the newsystem for underwater fire controlnomenclature is found in OP 1700,Volume1. 1

2. 2

3. 3

4. 4

4-32. Which FC symbol represents theunmodified (basic) range from yourship to the target?1. Rp2. Rv3. Rh4. R

4-33. What quantity is the result ofcorrecting sonar measurements?1. Apparent target position2. Past target position3. Actual target position4. Future target position

4-34. The difference between past taretposition and apparent target posi-tion is caused by1. sound beam refraction2. target movement3. parallax4. all of the above

4-35. After target course, position, andspeed have been detarmined, whichof the following functions must beperformed by the fire controlsystem?1. Estimating where the target will

be when the weapon is delivered2. Calculating what course to take

and when to fire3. Sending all the required infor-

mation to the control and weaponstations

4. Performing all of the abovefunctions

25

4-36. A magnetic brake uses electricalenergy to1. arrest or prevent movement of

a rotating shaft2. resolve electrical vectors into

line as components3. link two or more rotating shafts4. transform rotation speeds

between shafts

4-37. Which of the following devices arebasically similar in their designand construction but different infunction?1. Magnetic clutch and electrical

resolver2. Magnetic brake and magnetic

clutch3. Electrical resolver and magnetic

brake4. Electrical resolver and mechani-

cal integrator

4-38. Which trigonometric functionsdescribe the output voltages pro-duced by an electrical resolver asthe rotor is turned?1. Sine and cosine2. Tangent and cotangent3. Secant and cosecant4. Cosine and cotangent

Learning Objective: Describethe types of tests used tomaintain a modern FC computer.

Use the following alternativesfor items 4-39 thru 4-42:1. Transmission test2. Static test3. Dynamic test4. Rate test

4-39. What fire control system test isused to check the accuracy of aremote target angle indicator?

4-40. In what test would you manuallyinsert target bearing and courseto find target angle as a fixedvalue?

4-41. What test is used to check theaccuracy of a computer time system?

4-42. What systems test is used to checkthe ability of a computer tocorrect an introduced error in agiven time?

220

4-43. In figure 4-13 of your textbook,the diamond index on the inter-mediate ring dial of own ship'sdial group indicates1. own ship's course2. relative target bearing3. true target bearing4. launcher train order

4-44. By what method of internal com-munication do the bridge personnelreceive initial sonar contactinformation?1. Sound-powered phones2. Automatic indicator3. Voice tube4. MC system

0. Use the following alternativesfor items 4-45 thru 4-47:1. 29MC2. 61JS3. 21MC4. 1JS

4-45. What is the designation of theantisubmarine attack team con-trol circuit?

4-46. Which circuit is used to send con-tact information until ASW stationsare fully manned?

4-47. What is the designation of thecaptain's command system?

4-48. Which of the following soundpowered circuits is usually oneway from sonar?1. JA2. JP3. 1JS4. 61JS

4-49. What feature on some MC units canthe operator make use of to avoidinterfering with a circuit thatis in use?1. Cutout relay2. Flashing light signals3. Busy signal buzzers4. Monitor headsets

4-50. Compared to sound-powered circuits,MC circuits have the disadvantageof1. providing fewer separate circuit,72. increasing the general noise

level3. permitting only one-way opera-

tion4. requiring central operator con-

trol

26

4-51. Target infornation for antisub-marine attacks is transmittedquickest by1. sound-powered phones2. repeaters3. MC circuits4. voice tube

4-52. Video sonar information is dis-played at a remote station byusing1. electro-mechanical repeaters2. dial display groups3. electronic azimuth-range indi-

cators4. MC circuits

4-53. The main advantage of radiotele-phone over other types of externalcommunications is its greater1. accuracy2. reliability3. security4. speed

4-54. Which of the following messageforms is most used by SonarTechnicians?1. Plaindress2. Abbreviated plaindress3. Codress4. Abbreviated codress

4-55. What element of a message followsthe call?1. Heading2. Text3. Ending4. Reply

4-56. C,)ded tactical signals are usedto1. overcome language barriers2. reduce chances of enemy

interpretation3. use less time in transmission4. accomplish all of the above

4-57. What brevity code word is used toconvey the meaning "This is theend of my message; no response isrequired"?1. OVER2. BREAK3. OUT4. OVER and OUT

221

Learning Objective: Under-stand and make use of theInternational Morse Code.

4-58. You should learn the Morse codeusing "dit" and "dah" soundsinstead of "dot" and "dash" soundsbecause using "dits" and "dahs",makes it easier for you to1. separate each individual sound2. learn the sound patterns of each

letter3. count the number of dits in each

character4. count the beats in each charac-

ter

4-59 Where does the accent usually fallin Morse code letters?1. On the dit2. On the dah3. On the first sound4. On the last sound

4-60. Which of the following practicesmay help a student to memorizeMorse code?1. Writing the alphabet2. Speaking words in code3. Visualizing the dits and dahs4. Counting the dits and dahs

individually

4-61. The Morse code sound is in theshort sound group for all of thefollowing letters except1. S2. E3. N4. M

4-62. Which time interval should youdecrease to increase your codepractice speed?1. Between characters2. For each character3. Between words4. For each word

Learning Objective: Under-stand the use of prosignsand proper radiotelegraphprocedures.

27

4-63. The word "PROSIGN" stands for1. the first sign2. procedure sign3. provisional signature4. promissory signature

4-64. What prosign is used to separatethe message text from the ending?1. AR2. BT3. II4. TR

4-65. What prosign is used to indicatethe word "from"?1. AB2. BT3. DE4. WA

Information for items 4-66 thru4-70. Suppose your ship (NTLY)

operating with her sister (NMTE) duringan independent ship exercise (ISE)period. You have received permissionto conduct a CW communication exercisewith the sister ship over Gertrude.First you establish communication to seif the Sonar Technicians on the othership are interested. These items referto some of the messages you mighttransmit.

4-66. What is the first transmissionyou make?1. NMTE DE NTLY K2. NMTE DE NTLY BT K3. NTLY DE NMTE K4. NTLY DE NMTE BT K

4-67. After you establish communication,your second message asking themif they are interested will be1. NTLY DE DO YOU WISH COM DRILL

THIS NET BT K2. DE NTLY BT DO YOU WISH COM DRIL

THIS NET K3. NMTE NTLY DC YOU WISH COM DRILL

THIS NET OVER4. DE NTLY BT DO YOU WISH COM DRIL]

THIS NET BT K

4-68. Which of the following is a correclreply from your sister ship?1. DE NMTE NT AFFIRMATIVE UT K2. NMTE DE NT AFFIRMATIVE UT K3. NTLY NMTE BT AFFIRMATIVE BT K4. NTLY NMTE BT AFFIRMATIVE OVER

222

4-69. If, during the drill, you wished topause for a few seconds to make anadjustment what prosign would youuse?

4-70. Later, to conclude the drill,which of the following messagesdo yod send if you expect noreply?

1. AR 1. NMTE BT THANKS FOR DRILL OUT2. IMI 2. NMTE BT THANKS FOR DRILL AR3. BT 3. DE NTLY BT THANKS FOR DRILL4. AS BT K

4. DE NTLY BT THANKS FOR DRILLBT AR

G 44

28

Assignment

Communications (continued); Maintenance and Safety; Security


Learning Objective: Recognizeprosigns and correct radio-telephone procedures.

5-1. The adjusting screws on the sidesof an unshielded telegraph key areadjusted to1. prevent the key's movement

sideways2. prevent the key's movement

up and down3. provide correct spring tension4. provide correct spacing between

the contacts

5-2. All of the following are correctprocedures for using a telegraphkey except1. grasping the key tightly2. resting your fingers lightly

on the key knob3. placing your thumb against the

side of the knob4. placing your forefinger on the

key top

5-3. What communication procedure shouldyou use when operating the under-water telephone?1. Sound-powered phone procedure2. MC communication procedure3. Radiotelephone procedure4. Any of the preceding three

procedures

5-4. Which of the following calls andendings illustrate proper radio-telephone calling procedure?1. BLUEBIRD CALLING WALRUS - GO

AHEAD WALRUS2. WALRUS - THIS IS BLUEBIRD - OVER3. WALRUS DE BLUEBIRD - KAY4. WALRUS - BLUEBIRD CALLING - OVER

5-5. You have received and understoodWALRUS' last transmission. Toacknowledge receipt, you shouldreply1. ROGER - OVER2. ROGER WALRUS - OVER AND OUT3. OK WALRUS - BLUEBIRD IS OFF

AND CLEAR4. THIS IS BLUEBIRD - ROGER - OUT

5-6. If you make an error in transmit-ting a message, you should identifthe correct version with1. SAY AGAIN2. CORRECTION3. BREAK4. DISREGARD THIS TRANSMISSION

5-7. Which of the following prowordsshould you send if a substantialdelay is necessary during commu-nication with another radio-telephone station?1. WAIT2. STANDBY3. QRX4. WAIT OUT

5-8. You have just received a longmessage, the last few words ofwhich were obscured by interfer-ence. Which of the followingreplies that you might use conformsto standard procedure?1. ROGER - BUT REPEAT LAST TEN WORE2. CORRECTION - SAY AGAIN3. SAY AGAIN - ALL AFTER AIRBORNE4. ROGER - REPEAT BACK LAST TEN

WORDS

29

224

5-9. Which of the following submarineequipments is used for emergencyunderwater communications?1. AN/HQC-12. AN/WQC-13. AN/UQC-14. Radiotelephone

Learning Objective: Identifythe various flares used forcommunications.

Use the following alternativesfor items 5-10 thru 5-12.1. Green2. White3. Red4. Yellow

5-10. What color of flare is used toindicate the submarine hassimulated firing?

5-11. If a submarine intends to surface,he should fire what color of flare?

5-12. What color flare would NOT be usedunder normal conditions?

5-13. Which of the following publicationscontains detailed information aboutpyrotechnic signals?1. ATP-12. NWIP 1-43. AXP-14. FXP-1

Learning Objective: Describethe safety precautions to beobserved when using or workingon electrical or electronicequipment.

5-14. Which of the following voltagesoften is treated with indifferenceand is, therefore, the principalcause of electrical fatalities?1. 6002. 4403. 2204. 115

5-15. An index of Navy safety precautionsapplicable to the operating forcesafloat is contained in1. NAVSEA Technical Manual2. NAVSEA 0967-000-01303. NAVSO P-24554. OPNAV NOTICE 5100.19

30

5-16. When you have disconnected andtagged the sonar equipment mainpower switch, which of the follow-ing circuits may still beenergized?1. Remote indicators2. Heater elements3. Synchros4. All of the above circuits

5-17. When you go to close a switch youhave previously tagged and findanother OPEN tag on it, whatshould you do?1. Close the switch, and remove

your tag only.2. Close the switch, and remove

both tags.3. Leave the switch open, but

remove your tag.4. Leave the switch open, and

remove both tag:,

5-18- When two people in the same spaceare working on energized circuits,which of the following qualifica-tions should each have?1. Ability to secure the power2. Ability to give artificial

respiration3. Ability to perform first aid

for shock4. All of the above qualifications

5-19. Which of the following devicesgenerally are used to dischargecapacitors in deenergized equip-ment?1. Grounding straps2. Interlocks3. Rubber gloves4. Shorting bars

5-20. Electrical potential between equip-ment frames and the ship's hull isprevented by using1. ground straps2. shock mountings3. interlocks4. shorting bars

5-21. When replacing blown fuses, observethe following safety precaution(s)1. Secure power when practical2. Use only proper fuse puller3. Replace fuse with one of same

rating4. All the above

225

5-22. What do you do to damaged powertool cords to make them safe?1. Wrap with rubber tape.2. Wrap with friction tape.3. Shorten to remove the damaged

section.4. Replace the cord.

5-23. Test equipment should be at thesame ground level as the equipmentbeing measured to prevent erro-neous readings and1. electrical hazards2. damage to test equipment3. damage to equipment being tested4. capacitive reactance

5-24. Tube testers and other portable,externally-powered test equipmentare grounded to the ship's hullby the use of1. grounding straps2. three wire electrical cords and

connectors3. shorting bars4. probes

5-25. While you and STG3 Smith are workingon the equipment, Smith makescontact with an electrical circuitand cannot let go. Nearby, apeacoat is lying on an aluminumchair and you are wearing a webbelt. Which of these three articlesmight you use to remove Smith fromthe circuit if you could not easilysecure main power?1. The chair or the peacoat2. The chair or your web belt3. The peacoat or your web belt4. Any of the three articles

5-26. In the process of treating a personwho is not breathing as a resultof electrical shock, you mightperform all the following actsexcept to1. loosen his collar2. give him morphine3. give him artificial respiration4. cover him with a blanket

5-27. The most important factor when youadminister artificial respirationis to1. use the mouth-to-mouth method2. use the back pressure, arm lift

method3. begin treatment immediately4. call a corpsman

31

Learning Objective: Explainthe operation of the testequipment used in testing andtroubleshooting sonar equipment.

5-28. What general purpose instrumentmay you use to avoid carryingseveral others?1. Megohmeter2. Multimeter3. Ohmmeter4. Voltmeter

5-29. Which of the following instrumontsmay be used to measure frequency?1. Multimeter2. Voltmeter3. Oscilloscope4. Megohmeter

5-30. Transistors and diodes can bethoroughly checked by which of thefollowing?1. AN/URM-1272. AN/USM-2063. AN/USM-2074. AN/PSM-4D

Learning Objective: Describethe testing and troubleshootingprocedures necessary for logicaland accurate test and repair ofsonar equipment.

5-31. At what step in the troubleshootingprocedure in figure 9-9 of thetextbook would you first use amultimeter?1. One2. Two3. Three4. Four

5-32. Which of the following terminalboard markings indicate the secondboard in the fourth unit of theequipment?1. TB 14022. TB 14203. TB 4024. TB 420

226

5-33. What markings do you use on eachend of a conductor that connectsterminal E6 of board TB 802 toterminal C8 of board TB 202?

5-40. The principal use of a potentio-meter in a circuit is to1. vary voltage2. vary current

1. E6-202-C8/C8-802-E6 3. open and close the circuit2. C8-202-E6/E6-802-C8 4. control motor speed3. C8-202-E6jE6-202-C84. C8-802-E6/E6-802-C8

5-34. Where do you attach cable identi-cation tags?1. Close to each terminal

connection BLACK VIOLET GREEN2. On the cable at 50 foot

intervals3. On either side of decks and

bulkheads0

BLUE BLACK RED4. At all of the above locations

5-35. Where do you find a complete listof cable designations?1. Manufacturer's Technical Manuals Figure 5A.-Fixed capacitor.2. Handbook of Test Methods and

Practices Refer to figure 9-14 in your text-3. Dictionary of Standard Terminal book and figure 5A in this course

Designations for Electronic for items 5-41 thru 5-43.Equipment

4. NAVSEA Technical Manual; 5-41. What is the value in micro-Chapter 9600 microfarads of the capacitor shown

in figure 5A?5-36. A 100 ohm resistor with a silver 1. 500

band may vary in resistance within 2. 600minimum and maximum values of 3. 7501. 95 and 105 ohms 4. 7,5002. 90 and 110 ohms3. 85 and 115 ohms 5-42. What is the minimum and maximum4. 80 and 120 ohms capacitance, in micromicrofarads,

allowed for the capacitor shown5-37. What function does a rheostat in figure 5A?

normally perform in a circuit? 1. 600 to 9001. Voltage variation 2. 750 to 7752. Current adjustment 3. 6,000 to 7,5003. Open the circuit 4. 6,000 to 9,0004. Close the circuit

5-43. What dielectric is used in the5-38. A variable resistor intended for capacitor shown in figure 5A?

use as a rheostat may frequently 1. Airbe distinguished from one intended 2. Clayfor use as a potentiometer by the 3. Mica1. number of terminals 4. Graphite2. color code marking3. type of knob 5-44. What tolerance is allowed for a4. length of the resistor element capacitor that has three dot

code markings?5-39. The continuity of rheostats and 1. 2%

potentiometers is usually tested 2. 5%by using a/an 3. 10%1. ammeter 4. 20%.2. voltmeter3. ohmmeter4. wattmeter

2 732

Learning Objective: Explainthe types of maintenance andhow each is used to keep sonarequipment operational.

5-45. Which of the following publicationsconcerning equipment operatingstandards are used to assist incarrying out a maintenance 111-ogram?1. Manufacturer's Technical Manuals2. NAVSEA Technical Manual3. Electronic Information Bulletin4. 3-M Manual

In items 5-46 thru 5-49, select fromcolumn B the type of maintenancedescribed in column A.

A..Work B. Type ofPerformed Maintenance

5-46. The Sonar 1. OperationalTechnician onwatch replaces 2. Preventivean indicatorlamp. 3. Corrective

5-47. The sonar watch 4. Operationalsection cleans or Preventivethe air filterswhile the sonargear is in astandby situation.

5-48. A weak vacuumtube is replacedduring a systemcheck.

5-49. The senior SonarTechnician adjustsa relay that hascaused an equipmentfailure.

5-50. The Standard Navy Maintenance andMaterial Management (3-M) Systemdoes which of the following?1. Prescribes standard maintenance

procedures2. Provides feedback for program

updating3. Replaces all other maintenance

programs4. All the above

5-51. A means of collecting maintenanceand supply data in a form suitablefor machine processing is providedby1. PMS2. MDCS3. MIP4. OPNAVINST 4790.4

5-52. The MIP frequency code whichidentifies actions that arise onlyduring specific situations is1. A2. C3. R4. S

5-53. Who is responsible for updatingthe quarterly schedule?1. Department head2. Division officer3. Leading petty officer4. 3-M coordinator

5-54. An MRC does NOT list which of thefollowing?1. Tools, parts and materials2. Brief description of maintenance

required3. Safety precautions to be

observed4. Location of equipment

5-55. Which form is designed forreporting discrepancies orsuggested improvements in PMS?1. OPNAV 4790/7B2. OPNAV 4790/2K3. OPNAVINST 4790.44. All the above

Learning Objective: Befamiliar with the definitionsof the major elements ofsecurity.

5-56. What attitude should guide navalpersonnel in safeguarding classi-fied information?1. All personnel should refrain

from disseminating informationabout security requirements.

2. All personnel should makesecurity of classified infor-mation a natural element inall tasks.

3. All personnel should think ofsecurity as a function separatefrom their daily tasks.

4. Only personnel with securityclearances should concernthemselves with security

33 requirements.

228

5-57. An instruction indicating theclassification, downgrading, anddeclassification guidance that maybe assigned to subjects within aspecific area of defense activityis defined as1. classified information2. classification3. classification guide4. classified material

5-63. What classification is assigned tomobilization plans of the UnitedStates?

5-64. What classification is given toinformation which if disclosedcould lead to a break in diplo-matic relation affecting thedefense of the United States?

5-65. Which classification is assigned

5-58. An individual who determines that to devices and material related to

official information is in sub- communication security?

stance the same as informationknown by him to be already classi- 5-66. Which classification is assigned

fied by the government as Top to materials having a nature such

Secret, Secret, or Confidential that its unauthorized disclosureand designates it accordingly is could be prejudicial to the defense

known as a/an interests of the United States?

1. competent authority2. commanding officer 5-67. According to the text, which of

3. custodianthe following pieces of information

4. classifier is most likely to be classifiedas Secret?

5-59. Formerly Restricted Data is so 1. Documents concerning disci-designated by which of the plinary action, the knowledge

following? of which is to be safeguarded

1. Atomic Energy Commission 2. Frequency and call sign

2. Department of Defense allocations

3. Both 1 and 2 above 3. An important intelligence4. Secretary of the Navy operation

4. Security investigations of

5-60. Into which of the following naval officerscategories is classified infor-mation divided?1. Secret, Confidential, and Learning Objective: Define

Restricted Data the different types of security

2. Top Secret, Secret, and For areas.

Official Use Only3. Confidential, Secret, and Top

Secret 5-68. Which of the following has to do

4. Confidential, For Official Use with "Physical Security"?Only, and Secret 1. Transmission

2. DestructionThe following alternatives are for 3. Custodyitems 5-61 thru 5-66. 4. All the above

1. Secret2. Top Secret 5-69. An area which permits uncontrolled

3. Confidential movement of personnel is known as

4. Restricted Data 1. a limited area2. an exclusion area

5-61. What classification is assigned to 3. a controlled areamatrrial the unauthorized disclosure 4. any of the above

of which could result in excep-tionally grave damage to theUnited States?

5-62. Which classification is applied tomaterial of such a nature that itsunauthorized disclosure coulddamage the Nation?

22934

Learning Objective: Statethe requirements of maintainingsecurity of keys and combina-tions.

5-70. When must the keys or combinationsto safes or locks be changed?1. Every 12 months2. When a person with knowledge of

them is transferred3. When a compromise is suspected4. When any of the above occur

5-71. How many complete turns of a lockis required to secure a safe?1. At least two2. At least three3. At least four4. At least five

Learning Objective: Befamiliar with the parametersof "Personal Security."

5-72. Those persons who are entitled tohave or know about classifiedmaterial are those who have1. the proper clearance2. achieved the rank of lieutenant3. a "need to know"4. both 1 and 3 above

S GOVERNMENT PRINTINGOFFICE 1976- 641.277 29

35

230

5-73. Who, if anyone, in the Navy isallowed access tn classifiedinformation by virtue of his rank?1. Admirals2. Captains3. Both 1 and 2 above4. None

5-74. Which of the following topics mustnot be mentioned in personalletters?1. Casualties to personnel or

material by enemy action2. Location, identification, or

movement of ships or aircraft3. Criticism of equipment or morale

of the United States or herallies

4. All of the above topics

5-75. When using thermal copy paper toreproduce classified information,what type thermal copy is used?1. Front coated2. Back coated3. Uncoated4. Any of the above

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