A SERVICE PUBLICATION OFLOCKHEED-GEORGIA COMPANYA DIVISION OFLOCKHEED CORPORATION

EditorCharles I. Gale

Associate EditorsDoug BrashearJames A. LoftinVera A. Taylor

Art Direction & ProductionTeri I.. Mohr

Vol. 12, No. 2, April - June 1985

CONTENTS2

3

7

8

11

13

Focal PointPaul FrechPresident, Lockheed-Georgia Company

Hercules Flight Training CenterThe new Hercules Flight TrainingCenter offers the best in Hercules air-craft flight training.

Engine Performance Calculator KitAn easier and more accurate method ofchecking engine performance.

Solid State Oil Quantity TransmittersHow they work, and how to interpretthe indications.

Lockheed Introduces AVWASHA clean aircraft in less time, at lowercost.

A Quick Fix for a Hanging DoorA Simple Remedy often cures cargodoor in-flight operation problems.

Cover: A typical approach display on the Image II visual system at the Hercules FlightTraining Center.Back: A KC~l30H flown by the U.S. Marinesperforms an aerial refueling demonstrationfor Colombian Air Force A-375.

Published by Lockheed-Georgia Company, a Divisio n of

Lockheed Corporation. In format ion contained in this issue

is considered by Lockheed-Georgia Company to be accurate

and authoritative; it should not be assumed, however, that

this material has received approval from any governmental

agency or military service unless it is specificall y noted. This

publication is for planning and information purposes only,

and it is o r to be construed as authority f o r making changes

on aircraft or equipment or as superseding a ) established

operat ional or maintenance procedures or policies. The

following marks are registered an d owned by Lockheed

Corporation: . Hercules: and

Written permission must be obtained from L o c k h e e d -

Georgia Company before republishing any material in this

periodical. Address al l communications to Editor, Service

News, Department 64-31, Zone 278, Lockheed-Georgia

Company, Marierta, G e o r g i a . 30063. C o p y r i g h t 1 9 8 5

Lockheed Corporation.

PAUL FRECH

Partners for Progress

We at Lockheed have a proud traditionof partnership. Almost 70 years ago twobrothers, Allan and Malcolm Loughead,pooled their talents and their resources toform what won would become known asthe Lockheed Aircraft Company. Sixteenyears later another partnership, this timeheaded by Robert E. Gross, restructured thecompany and brought into being theorganization that is today s LockheedCorporation.

In the pioneer days of aircraft manufac-turing, partnership offered both thestrength of mutual enterprise and a w a y toshare the risks, financial and otherwise, that

were a constant threat to the future of the fledgling industry. Today, aerospace has maturedinto a vast and highly sophisticated giant, and the concept of partnership has evolved to playa new and enhanced role. Cooperative ef for t s have emerged as an efficient and productiveway of bringing together the unique expertise of selected organizations within the industryto achieve a common goal. What that goal is can be summed up in one word: value Thepurpose i s to provide the aerospace customer with the best in state-of-the-art products andservices at the lowest possible cost.

There is no other industry where the demonstrated potential for advancement throughcooperative effort holds so much promise as it does in the aerospace industry, and I can thinkof no better example of what this kind of partnership can yield in practical terms than thenew Hercules Flight Training Center described in this issue of Service News.

In building this remarkable new facility, Singer s Link Flight Simulation Division and theLockheed-Georgia Company have established an ultra~modern training center which can offerboth military and civi l ian Hercules aircraft operators the ideal way oi meeting their flight trainingrequirements. The capabilities of the center and its staff are second to none in quality. yethighly cost-effective at the same time.

We are very proud oi the Hercules Flight Training Center and of the kind of cooperativeendeavor that it represents. The building is new. and thr technology its simulator representsis the latest and the best. But I take particular satisfaction in the knowledge that this facilityalso contains a full measure of something that is not news the Lockheed tradition of providingour customers with the greatest possible v a l u e for every investment in our products and services.

Paul FrechPresident

M. M. HODNETT DIRECTOR

CUSTOMER INTEGRATED

SERVICE LOGISTICS SUPPORT

A. H. McCRUM J. L. THURMOND

DlRECTOR DIRECTOR

CUSTOMER

SUPPLY

H. T. NISSLEY

DIRECTOR

New at Lockheed-Georgia

One of the first large-scale uses of flight simulationwas in World War II. The Link trainer, named after itsinventor and by today’s standards a relatively simpledevice, was used in pilot ground school for training insimulated instrument flight conditions and radio naviga-tion. Flight simulators have evolved over the years intoreplicas of flight decks or cockpits based on individualaircraft types with specific handling characteristics built-in.

Modern flight simulators satisfy a definite need inthe field of flight training because they allow flight train-ing to take place with no risk to an aircraft or person-nel. The cost is also lower than if all training were con-ducted in an aircraft, although actual flight time in theaircraft cannot be dispensed with altogether,

To provide the benefits of state-of-the-art flightsimulator training for crews of C-130H, C-130H-30, andL-lOO-30 aircraft, Lockheed-Georgia Company has

Lockheed SERVICE NEWS V12N2

teamed up with the Singer Company’s Link FlightSimulation Division in the construction and operationof a new Hercules Flight Training Center. The best, mostcomprehensive Hercules aircraft aircrew trainingavailable in the world will be conducted in this newfacility.

The simulator is built in Binghamton, N.Y. by theLink Simulator Division of the Singer Company. Itfeatures the first microprocessor-driven visual system:IMAGE II, built in England by Link-Miles. The IMAGEII system presents quite a realistic visual display and haswon approval for the simulator by the Federal AviationAdministration as a “visual simulator”.

The trainee crew aboard the simulator sees adusk/night presentation of computer-generated colorscenes representing the view from the cockpit insimulated taxi, cross-country, circling approach, andlanding procedures. During simulated flight in the

3

vicinity of the airport, the view includes:

l The whole airport area and all significant features.

l The area surrounding the airport (depending onvisibility and aircraft altitude).

l Ground and airborne traffic, both static andmoving.

l The horizon, under clear conditions.

l Environmental surfaces, runway markings, land-marks, etc.

l Runway and approach lighting.

l Weather conditions that vary from clear tocompletely obscured.

Away from the airport area, urban lights and othernavigational features may be seen.

The Hercules aircraft’s flight station is duplicatedin detail on the simulator. Flight conditions such as

4 Lockheed SERVICE NEWS V12N2

pitch, roll and yaw rotation as well as surge, heave, andsway are simulated by a six-degree of freedom motionsystem. This feature provides the physical sensations ofthe various flight maneuvers for the flight crew.

The characteristics or “feel” of the aircraft’s controlsare duplicated to enhance the effectiveness of the train-ing. Changes in the amount of movement and force onthe controls as a function of aircraft acceleration, velo-city, configuration, center of gravity, and weight giverealistic feedback to the pilot.

Flight crews can practice maneuvers in the Herculessimulator which may present certain risks whenaccomplished improperly in the airplane, such as:

l Flight with flight control boost off.

l Stalls.

l Rejected takeoffs.

l Three-engine takeoffs.

l Two-engine landings.

l Engine failure at takeoff.

Lockheed SERVICE NEWS V12N2 5

l Maximum effort takeoff and landings.

l Limited visibility approaches.

Certain hydraulic, electrical, and other systemfailures that cannot be effectively demonstrated in theaircraft can be demonstrated in the simulator under avariety of simulated weather conditions. If the studentencounters a problem with a particular maneuver or pro-cedure, the situation may be frozen at that point, andthe solution and alternatives explained without flyingback into position to start the maneuver again.Turbulence, icing conditions, high crosswinds, instru-ment and night flying conditions are realisticallysimulated and are practiced as required by the scheduleor as student need dictates. Simulator flight trainingallows more efficient use of instruction time becausethere are no weather delays, maintenance delays, refuel-ing of the aircraft, preflight inspection, air traffic con-trol delays, or ground operation delays.

Simulator flight training is not only a more efficientform of training but it is a more economical form oftraining as well. The students require less flight time inthe simulator to perfect the same sequence of maneuversand the cost per hour for operating the simulator issignificantly less than what it costs to operate theaircraft.

For the instructors, there are two compact panelsequipped with three CRTs and two keyboards that allow

complete control of all aspects of the training situation.The onboard location of the instructor stations allowsan over-the-shoulder view of the pilot and flight engineeractions and cockpit instruments. The instructors haveover four hundred discrete and variable malfunctionsavailable for their use in simulating failures of aircraftsystems. Initial positioning of the simulator with thedesired environmental conditions, fuel and cargo loads,pre-programmed malfunctions and performancemonitoring is selected by the instructor. It is possibleto record and play back selected maneuvers in thesimulator to allow student scrutinization of their ownactions and enhance learning. In addition, the instruc-tor may select specific data relative to the simulatortraining session that may be printed on a computerprintout for use as a training aid and as a means ofevaluating the trainees’ progress.

For complete information on the new Hercules FlightTraining Center, contract:

ManagerHercules Flight Training Center605 Franklin RoadMarietta, Georgia 30067, USATELEX: 42642 LOCKHEED MARATelephone: (404) 424-3646

6 Lockheed SERVICE NEWS Vl2N2

Engine Performance Checks Made Easier

CARD READER‘.-P/N 82104A

A new method of engine performance measurementhas been developed by Allison Gas Turbine Division foruse with the Series III turboprop engines such as the501-D22A, T56-A-15, and T56-A-15 LFE engines. Thisnew method involves the use of a hand-held calculatorfor determining engine performance on the groundinstead of using one of the published engine perfor-mance charts, which are often difficult to read and sub-ject to miscalculation. The new method is easier to per-form and much more accurate. DIGITAL

THEAOMETERThe new method developed by Allison uses aMODEL 450.AKT

Hewlett-Packard model 41CV programmable calcu-lator equipped with a P/N 82104A card reader, anda set of magnetic cards, part numbers 23006772-1,23006772-2, and 23002987, on which engineparameter curves have been recorded. To do anengine performance check using the calculator,the operator enters the outside ambient THERMOCOUPLE

temperature near the engine, the pressurealtitude where the check is being done,and engine power either in inch-pounds oftorque or in degrees Celsius TIT, andthe calculator will display the engineperformance percentage.

Allison does not specify a par-ticular interval for engine performancechecks, but they do suggest that a perfor-mance check be accomplished and recorded after instal-lation of a new or newly overhauled engine. This willestablish a baseline to which subsequent checks can becompared, and allow engine operating trends to berecognized. The use of the hand-held calculator willgreatly facilitate setting up a series of accurate perfor-mance checks.

of this kit is 3403157. The kit will be listed in the nextrevision of the Illustrated Tool and Equipment Manual,SMP 515E.

Lockheed has assembled a kit which contains all theitems necessary to accomplish an engine performancecheck by this method. Besides the 41CV calculator,82lC4A card reader, and magnetic cards mentionedearlier, the kit contains a model 450-AKT digital ther-mometer, and a part number HPS-AP-K-316E-IZSMPthermocouple probe unit (see figure), both manufac-tured by Omega Engineering Incorporated, and a set ofinstructions, part number 3403157-l. The part number

For quotations or purchase of the kit, contact:

Lockheed-Georgia CompanySupply Sales and Contracts Dept.Department 65-11, Zone 451Marietta, Georgia 30063Telephone (404) 424-4214TELEX 542642

Lockheed SERVICE NEWS V12N2 7

The Hercules aircraft has been updated with manytechnological improvements over the years, a fact whichhas helped maintain this remarkable airplane as theworld’s most versatile airlifter. One such improvementis the use of solid-state microprocessors to provideengine oil quantity level signals to the engine oil quan-tity indicators.

Dataproducts New England’s Aerospace Division iscurrently supplying the solid-state oil quantity transmit-ters (see Figure 1) for installation on all new Herculesaircraft. The indicators in the aircraft flight station arenot affected by this change.

A brief explanation at this point will help clarify theoperation of these new solid-state transmitters. The heartof the system is a length of small-diameter, nickel-alloywire used as a sensing element in the solid-state transmit-ter probe housing. The microprocessor, located in theupper end of the transmitter (Figures 1 and 2), pulsescurrent in very small increments through the wire,heating the wire and thereby increasing its resistance.The microprocessor measures the resistance change andis able to calculate the temperature increase of the nickelwire by using data on the temperature coefficient ofnickel, which is stored in its memory.

When the sensing element is immersed in engine oil,the temperature increase is substantially reduced. Theamount of temperature change is dependent upon thetotal mass of the nickel wire, its specific heat, and thepercentage of the element that is immersed in oil. Themicroprocessor calculates the unknown variable, theenergy loss from the portion of the element that is im-mersed, and sends the appropriate signal to theindicator.

The solid-state unit is also different from the olddesign in that it posesses automatic self-test features.

ENGLOW OIL

QUANTITY

2 US GALLONS

WARNING LIGHT & OIL QUANTITY GAUGE

When power is applied to the system, the transmittertests the indicator, the low oil light circuits, the drivecircuits of the transmitter, the transmitter electronics,and the sensing element’s continuity.

The self-test is observed on the appropriate indicatorfor each engine. This feature is not available on the float-type oil quantity transmitters and deserves further ex-planation. When electrical power is applied to the systemwith the appropriate circuit breakers closed, the in-dicator pointer will drive to the “F” mark and hold forapproximately one second. The pointer will then swingto the “O-l” mark and the low oil warning light will il-luminate. This will also be observed for about a second.Then the low oil light will extinguish and the pointerwill drive in one, two, or three increments to the actualoil level quantity. Since each transmitter is capable of

Lockheed SERVICE NEW S V12N2

illuminating the low oil light, power may be applied toeach unit individually to check for proper self-test uponinitial power application.

It should be noted that since this unit is a form, fit,and function replacement of the float-type unit, a com-bination of the two types of transmitters may occur onany particular aircraft. It is important to remember thatunder this condition there will be a difference in indica-tions upon initial power application because of the solid-state unit’s self-test feature.

Once the self-test is completed and the system is in-dicating the oil quantity, the indicator pointer mayoccasionally be observed to be swinging a small amount(+/- l/2 gallon) on either side of the indicated quantity.This is a designed-in search mode and should be con-sidered as normal operation when it is observed.

If a self-test is interrupted for some reason, or poweris removed from the system during normal operation,a 30-second wait is required before the transmitter’smicroprocessor will reset. After this interval, power maybe reapplied for a normal power-on self-test.

The solid-state transmitter also tests the engine oilquantity indicating system continously during anypower-on condition. Should a fault develop in the probe,the low oil light will blink. Should the transmitter finda fault in its own circuits, the low oil light will illuminatesteadily and the indicator pointer will drive to off-scalefull and remain there.

Although the solid-state oil quantity indicating systemtransmitter is designed to be a “form, fit, and function”equivalent of the older float-type unit it supersedes, dur-ing engine servicing some differences may be noted be-tween the oil quantity readings obtained with a solid-state transmitter and those given by float-type units or

Lockheed SERVICE NEWS Vl2N2

OIL QUANTITY TRANSMITTER

SOLID-STATEOIL QUANTITY TRANSMITTER

Figure 1.

the oil tank dipstick.

This is a result of the relative internal positions of theoil tank dipstick and the transmitter probe, which are

9

shown in Figure 2. The figure also shows approximatelywhere the oil supply in the tank would be located at zerodegrees roll-the aircraft wings level. Both the solid-statetransmitter and the float-type transmitter are calibratedin accordance with design specifications to match thereadings of the tank dipstick at zero degrees of roll. Butthe physical locations of the components that actuallymeasure the oil in the two types of transmitters havesome important consequences for the operation of thesystem.

The float-type transmitter incorporates a float thatmeasures the oil level close to the dipstick, a point whichis some distance from where the transmitter is installed.As the degree of roll varies from zero (because of anunlevel ramp, for example), the dipstick and the floattransmitter readings remain about the same.

The solid-state transmitter is installed at the samelocation as the float-type transmitter, but it also takesreadings there. This means that the solid-state transmit-ter is measuring the oil level near the side of the tankthat is opposite from the dipstick. This arrangement,which is necessary to meet the requirement of completeinterchangeability with the old unit, will yield oil quan-tity indicating system readings that are in good agree-ment with the dipstick as long as the wings are level,in other words, at zero degrees roll.

But any condition that will affect roll, such as park-ing ramps that are not level, unequal fuel loads in thewings, possibly even wind conditions, can produce oilquantity readings that do not agree. When measured onthe ground, the difference between the values shown bya solid-state oil quantity transmitter and the dipstick ofthe same engine may differ by as much as 2.25 gallonswith up to 2 degrees of roll and still be considered withintolerances.

The operation of the oil quantity indicating systemis not affected by such factors in normal flight, and itis in flight where the advantages of the new transmit-ters become most apparent. From a practical standpoint,the tank dipstick should be used for determining groundservicing requirements, while the solid state transmittercan be considered a “remote dipstick” for all normalflying operations.

The Dataproducts New England manufactured solid-state oil quantity transmitter is hermetically sealed,making it virtually immune to the detrimental effectsof dust, sand, salt air, oil, humidity, and altitude. Withself-test features, built-in fault codes, and continuousmonitoring of system integrity, the DNE solid-state oilquantity transmitter offers Hercules aircraft operatorsenhanced performance from the engine oil quantity indi-cating system.

QUANTITY

TIME-SHARED POWER TO GAUGE

TRANSMITTER/QUANTITYSIGNAL TO GAUGE

MICROPROCESSOR -CONTROLLED PULSE

ANDMEASURING ELECTRONICS

PROTECTIVE

INiCKEL WIRE ON RIGID SPINE

Figure 2. SOLID STATE OIL QUANTITY TRANSMITTER TANK INSTALLATION.

10 Lockheed SERVICE NEWS V12N2

Today most aircraft are cleaned in the conventionalmanner using cold water, detergents, a sponge, and abrush. However, conventional washing techniques havethe following disadvantages:

Excessive material costs due to high consumptionof cleaning compound and water,

Excessive labor costs due to high manhourrequirements,

Aircraft surface deterioration caused by harshbrush effects, and

Inadequate cleaning resulting in corrosion.

Aside from the benefit of an enhanced physical ap-pearance, and aircraft with a clean exterior surfaceprovides the following economic benefits:

l Increased service life due to improved corrosionresistance.

Early detection of surface cracks, leaks, and wornparts,

Increased fuel efficiency due to reducedaerodynamic drag, and

Reduced fuel consumption due to lower weight.

In an effort to provide these benefits while loweringthe operator’s costs, Lockheed began a study of aircraftcleaning equipment. The result of that study is the in-troduction of the Avwash Cleaning System (P/N1310858-101, NSN 4940-Ol-157-8614BP) shown inFigure 1.

Avwash is a self-contained mobile cleaning system,requiring only an external water source. It is designedto economically clean a variety of aircraft, machinery,mobile and stationary equipment, floors, and any sur-face subject to dirt, oil, grease, or other contaminants.This system cleans on contact by rapidly disintegratingand dissolving surface contaminants by means of a high

Lockheed SERVICE NEWS V12N2 11

energy (high pressure, 1000 PSI, and high temperature,2OO'F/93'C) spray of water and cleaning compound.This provides for thorough cleaning of the surfaces withless scrubbing, resulting in more effective corrosionprevention and less surface deterioration.

When compared with conventional methods ofwashing an aircraft, the savings in cleaning compound,water, manpower, and time derived from using the Av-wash System are evident. Figure 2 illustrates the savingswhich can be achieved on a Hercules type aircraft usingAvwash.

the Hercules in approximately three hours. This is ac-

By following the operating manual provided with thesystem, a crew of three can wash an aircraft the size of

complished by having two men operating spray gunswhile one man operates and monitors the systemcontrols.

The cleaning compounds recommended for use withthe Avwash System are nontoxic, have no dangerousfumes, are economical (formulated for use in a 50 to1 dilution), and contain corrosion-inhibitor additives.

As well as being a cleaning system, Avwash can easi-ly be adapted to perform other functions, including:

order to provide the desired capability.

deicing, anti-icing, chemical decontamination, hi-density foaming, and wet sandblasting. These conver-sions can be accomplished by substituting speciallydesigned modules for certain svstem components, in

Labor (Manhours)

Cleaning Compound ($)

NOTE: Based on 13 washes per year per aircraft, three (3) hours cleaning time per aircraft, andcleaning compound at $3.00/Gal.

One such derivative is the Decontamination, Deicing,and Cleaning System (P/N 1310847-101) shown in Figure3. This is a mobile unit which in addition to these func-tions can be used as an internal jet engine washer as wellas a personnel shower. It will draw water, glycol,detergent, liquid decontamination agents, and diesel fuelfrom any available source.

Figure 3.

The Avwash system and its derivatives represent asignificant advancement in the area of aircraftmaintenance. Designed to reduce both labor andmaterial costs associated with aircraft washing, thissystem provides superior cleaning capability. It’s mobili-ty, simplicity of operation, and ability to conserve waterand other valuable resources makes it ideal for bothremote and main operating bases.

If you would like additional technical or procurementinformation about the Avwash system, please direct in-quiries to the Manager, Supply Sales and ContractsDepartment, at the following address:

i i;Lockheed-Georgia Company

DECONTAMINATION, DEICING, &CLEANING SYSTEM (P/N 1310847-101)

Supply Sales and Contracts DepartmentDepartment 65-11, Zone 451Marietta, Georgia 30063Telephone (404) 424-4214TELEX 542642

12 Lockheed SERVICE NEWS Vl2N2

Occasionally we receive reports from Hercules aircraftoperators of aft cargo doors failing to lock in the openposition during in-flight door operation. On the ground,an operational check of the aft cargo door often failsto duplicate the in-flight write-up. This leaves themaintenance technician in the unenviable situation ofhaving to troubleshoot a problem he cannot duplicate.The most common course of action then is to try outsome things to see if they will help. Unfortunately, inthis particular case the efforts to remedy the problemmay ultimately do more harm than good, and theunderlying problem will still be left unresolved.

The usual practice after an initial in-flight cargo dooroperation malfunction is to sign off the write-up if anoperational check by the maintenance technician isfound to be satisfactory. If the cargo door continues tofail to lock open during in-flight operation, one of two

Lockheed SERVICE NEWS V12N2

things is usually done which may appear to solve theproblem. One fix is to shorten the cargo door actuatorby adjusting the rod end; the other is to lower the uplockassembly. These two procedures are often done evenwhen it has been previously determined that the aftcargo door system is rigged in accordance with the rampand aft cargo door section of the maintenance manual.Let us see why these two actions should not be under-taken in an attempt to correct this kind of in-flight aftcargo door malfunction.

First, by shortening the cargo door actuator, unduestress can be transmitted to the actuator attach pointon the cargo door or aircraft structure. This could leadto cracking and failure of the attach points if the in-creased stress is maintained.

If the second approach is chosen, lowering the uplock,

13

craft is in flight. Since the air load cannot be eliminated,another means of reducing the downward force on thedoor must be found.

Figure 1 illustrates a typical Hercules aircraft aft cargodoor and the storage compartments located on it. Whenboth auxiliary ramps and both paratroop door laddersare stowed, and all stowage boxes are loaded to theirmaximum allowable weights, a total of 578 pounds ofequipment is stored on the door. This weight - in par-ticular the way it is distributed- plus the weight on thedoor, the force needed to overcome the door snubber(installed on most Hercules aircraft built since 1972),the force needed to engage the uplock, and the forcecaused by the air load during flight combine to requirea pressure of more than 3300 psi to open and lock thedoor during flight. Since the auxiliary hydraulic systemonly provides 3000 psi, it is obvious why a heavily loadedcargo door cannot lock open during flight. Even on Her-cules aircraft without a snubber installed, the pressurerequired to open and lock a fully loaded aft cargo doorin flight is approximately 3270 psi.

When the aircraft is sitting on the ground, the cargodoor is subjected to all the forces just mentioned ex-

care must be taken to ensure that the required 108-inchclearance between the ramp floor and the cargo dooris maintained when both are in the open position. If thelob-inch clearance is not maintained, a loadmastermight unwittingly try to push a normal-size load throughtoo small an opening, possibly damaging the cargo door.

When these two approaches to getting the door tolock during in-flight operation fail, some maintenanceorganizations have even removed and replaced the wholedoor in an attempt to solve the problem.

None of these corrective actions need be used for thetype of in-flight malfunction that we have described.The solution is likely to be much simpler. When a cargodoor operates on the ground in accordance with themaintenance manual, but does not lock open during in-flight operations, the problem is usually too muchweight on the cargo door.

The reason that the door does not open completelyand lock in flight is because of an extra force that actsin the opposite direction from the actuator trying toopen the door. This added force is caused by an air load,which in effect tries to pull the door down when the air-

Figure 1. AFT CARGO DOOR.

I2 25,000 LB

TIEDOWN CHAINSMISC EQUIPMENT

MAX WEIGHT50 LBS

NO BOX

MISC EQUIPMENTMAX WEIGHT

50 LBS

t 4CAPASSY 112 TIEDOWN RINGMISC EQUIPMENT

MAX WEIGHT50 LBS

2 AUX RAMPSMAX WEIGHT

100 LBS

1 CARGO NETTYPE A2

MAX WEIGHT50 LBS 15 TYPE AlA

TIEDOWNS15 TYPE MC1TIEDOWNS

MAX WEIGHT100 LBS

15 TYPE AlATIEDOWNS

15 TYPE MC1TIEDOWNS

1 CARGO NETTYPE A2

MAX WEIGHT50 LBS

MAX WEIGHT100 LBS

THESEBOXESWEIGHT 28 LBS

FWD

1

14 Lockheed SERVICE NEWS Vl2N2

cept for the air load. Without the air-load force, thepressure required to open and lock the door on aircraftwith a snubber is approximately 2400 psi, less for air-craft without a snubber.

The obvious solution to the problem is to removeenough weight from the cargo door during in-flight door operation to counteract the effect of the in-flight airload. If all the equipment stowed in the forward threestowage boxes is removed, the weight on the door will

be reduced by 150 pounds. This may not sound likemuch, but this weight coupled with its distance fromthe cargo door hinge line reduces the amount ofhydraulic pressure needed to lock the cargo door openin flight from more than 3300 psi to approximately 2955 psi. On airplanes without a snubber, the pressure need-ed is less than 2900 psi.

The information that we have just related about thepressures needed to open and lock the aft cargo doorunder different conditions is based upon functional testsperformed by Lockheed during the early 1970’s. As aresult of these tests, Lockheed started installing a decalon each of the forward three stowage boxes starting withHercules aircraft LAC 4682. This decal reads“STOWAGE BOX TO BE EMPTY DURING IN-FLIGHT OPERATION OF THE AFT CARGODOOR?

In an effort to further emphasize the importance ofunloading these stowage boxes when the aft cargo dooris to be opened in flight, Lockheed will include instruc-tions to this effect in future editions of the appropriatetechnical manuals. A recommendation will also be madethat similar information be included in upcoming revi-sions of the affected military technical orders.

Making certain that the forward stowage boxes areempty will help ensure that the aft cargo door will lockproperly in the open position during in-flight door

operation. One of the first questions that maintenanceshould ask when debriefing a flight crew that hasreported an in-flight problem with the aft cargo dooris whether the forward stowage boxes were emptied priorto door operat ion. Th is may save a lo t o ftroubleshooting time and needless maintenance to aperfectly rigged aft cargo door.

Lockheed SERVICE NEWS V12N2 15

I ..... -" .. ( f t' (j •.. ~ -.. -.-.,. ....,,-. "