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CircularSuM=t: EXTENDEDRANGE OPERATION Da* 12/30/88 ACNo: lZO-42AWITH TWO-ENGINE AIRPLANES Initiated by: mS-2lW Change:(ETOPS) -270

1 0 PURPOSE. This advisory circular (AC) states an acceptab lemeans, but not the only means, for obtaining approva l under FARSection 121.161 for two-engine airplanes to operate over a routethat contains a point farther than one hour flying time at thenormal one-engine inoperative cruise speed (in still air) from anadequate airport. Spec ific criteria are included for deviation of75 minutes, 120 minutes or 180 minutes from an adequa te airport.2 CANCELLATION.Engine Airplanes, ACl20-42, Extended Range Operation With Two-dated June 6, 1985, is canceled.3 RELATED FAR SECTIONS. Sections 21.3, 25.901, 25.903, 25.1309,3i.19, 33.75, 121.161, 121.197, 121.373, 121.565, and 121.703 ofthe Federal Aviation Regu lations (FAR) l4 DEFINITIONS.

a. Airport.(1) Adequate. For the purpose of this AC, an adequateairport is an airport certified as an FAR Part 139 airport or isfound to be equivalen t to FAR Part 139 safety requirements.(2) Suitable. For the purpose of this AC, a suitableairport is an adequate airport with weather reports, or forecasts,. or any combination thereof, indicating that the weather conditionsare at or above operating minima, as specified in the operationspecifications, and the field condition reports indicate that asafe landing can be accomplished at the time of the intendedoperation.

b Auxiliary Power Units (APU) A gas turbine engineintended.for use as a power source for driving generators,hydraulic pumps, and other airplane accessories and equipmentand/or to provide compressed air for airplane pneum atic systems.(1) An essential APU installation provides the bleed airand/or mechanical power necessary for the dispatch of a transportcategory airplane for operations other than extended rangeoperations with two-engine airplanes.


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AC 120-42A 12-30-88

(2) An APU installation which is intended to serve as oneof the three or more independent alternating current (AC)electrical power sources required for extended range operationsprovides the bleed air or mechanical power necessary for the safeflight of a two-engine transport category airp lane gpproved forextended range operation under a deviation from FAR Section 121.161and is designed and maintained to provide a level of reliabilitynecessary to perform its intended function.

c. ETOP S Configuration Maintenance and Procedures (CMP)Standard. The particular airplane configuration minimumrequirements including any special inspection, hardware lifei limits, Master Minimum Equ ipmen t List (MMEL) constraints, andmaintenance practices found necessary by the FAA to establish thesuitability of an airframe-engine combination for extended rangeoperation. .d l Engine. The basic engine assembly as supplied by theengine manufacturer.e. Extended Range Operations. For the purpose of this AC,extended range operations are those flights conducted over a routethat contain a point further than one hour flying time at theapproved one-engine inoperative cruise speed (under standardcond itions in still air) from an adequate airport.f Extended Range Entry Po int. The extended range entry pointis th;! point on the aircraft's outbound route which is one-hourflying time at the approved single-engine inoperative cruise speed(under standard cond itions in still air) from an adequate airport.g Fail-Safe. A design methodology upon'which the FAR Part 25

airworthiness standards are based. It requ ires the effect offailures and combination of failures to be considered in defining asafe design. (Refer to Append ix 2 for a more complete definitionof fail-safe des ign concepts,)h In-flight Shutdown (IFSD).function in flight and is shutdown, When an engine ceases towhether self-induced, crewinitiated or caused by some other external influence (i.e,, IFSDfor all causes; for example: due to flameout, internal failure,crew-initiated shutoff, foreign object ingestion, icing, inabilityto obtain and /or control desired thrust, etc.),i. System. A system includes all elements of equipment

necessary for the control and performance of a particular majorfunction. It includes both the equipment specifically providedfor the function in question and other basic equipment such asthat necessary to supp ly power for the equipm ent operation.(1) Airframe System. Any system on the airplane that isnot a part of the propulsion system.

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12-30-88, AC 120042A(2) Propulsion System. The airplane propulsion systemincludes: each component that is necessary for propulsion:components that effect the control of the major propu lsion units:and components that effect the safe operation of the majorpropulsion units.

5 DISCUSSIONe To be eligible for extended range operations, thespecified airframe-engine combination should have beencertificated to the airworthiness standards of transport categoryairplanes and should be evaluated considering the concepts inParagraph 7, evaluated conside ring the type design considerationsin Paragraph 8, evaluated considering in-service experiencediscussed in Paragraph 9, and evaluated considering the continuingairworthiness and operationa l concepts outlined in Paragraph 10,a, General l All two-engine airplanes operated underPart -121 are required to comply with FAR 121.161.Section 121.161 states, (in pertinent part), that "unlessotherwise authorized by the Administrator, based on the character

of the terrain, the kind of operation, or the performance of theairplane to be used, no certificate holder may operate two-engineor three-engine airplanes (except a three-engine turbine poweredairplane) over a route that contains a point farther than one hourflying time (in still air at norma l cruising speed with one-en gineinoperative) from an adequa te airport." It is significant to notethat this rule is app licable to reciprocating, turbopropeller,turbojet, and turbofan airplanes.transiting oceanic areas or routesentirely over land,b Backqround, Although FAR 121,161 requirements evolvedduring the era of piston-engine airplanes and these requirements-are currently app lied to turbine-powered airplanes which have

significantly better reliability, experience has shown the presentrule to be effective and yet flexible enough in its application toaccomm odate significant improvements in technology. Untilrecently, little consideration had been given to reexam ining theviability of extending the perm issible operating range of two-engine turbine powered airplanes, by granting credit for improvedreliability due to the limited range/pay load capabilities of mostof the existing generation of two-engine turbine-powered airplanes.However, some of the new generation airplanes have a range/payloadcapab ility equivalen t to many previous generation three- and four-engine airplanes. The demonstrated range/pay load capabilities ofthe new genera tion airplanes, including their provisions forachieving a higher degree of reliability, clearly indicate there isa need to recogn ize the capabilities of these airplanes and toestablish the conditions under which extended range operations withthese airplanes can be safely conducted.over oceanic and/ordesolate land areas.

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AC 120042A- 12-30-88C. 121.161 Historical Basis. FAR Section 121.161 has anextensive historical basis which began as early as 1936. The rule\in effect in 1936 required the applicant to show, prior toobtaining approva l for the operation, that intermediate fields,availab le for safe takeoff and landings, were located at least at10 0 mile intervals along the pro.posed route. This restrictionapplied to all airplanes operating under this rule regardless ofthe terrain or area overflown. Throughout the evolution of thecurrent 121.161 the following factors have remained constant:

(1) The rule has always applied to all areas of operationand has not been limited to overwater operation.(2) Any additional restrictions imposed or, alternatively,any deviations granted to operate in excess of the basicrequirements were based on a finding by the Administrator thatadequate safety would be provided in the proposed operation whenall factors were considered. This finding was never limited toengine reliability alone.(3) The airports used in meeting the provisions of therule must be adequate for the airplane used (i.e., available forsafe landings and takeoff with the weights authorized), and(4) In granting a deviation from the time restriction, theAdministrator considers the character of the terrain, the kind ofoperation and the performance of the aircraft, etc.

6 APPLICABILITY. Since large transport category airplanes arecirtificated in consideration of the operating rule, FARSection 121.161, any consideration for deviation from thisoperating rule for two-engine airplanes necessitates an evaluationof the type design to determine suitability of that particularairframe-engine comb ination for the intended operation. Thiscircular provides guidance for obtaining type design, continuedairworthiness and operations approva l for those two-enginetransport category airplanes intended for use in extended rangeoperations. The issuance of this AC is not intended to alter thestatus of deviations previously approved in accordance with FARSection 121.161. Although many of the criteria in this AC may becurrently incorporated into an,operator's approved program forother airplanes or route structures, the unique nature of extended, range operations with two-engine airplanes necessitates anevaluation of these operations to ensure that the approved programsare effective. To the extent that changes in the airplane's typedesign, continued airworthiness, or the operations program areinvolved as a result of this evaluation, they are approved throughthe normal approval processes.7 CONCEPTS. Although it is sel'f-evident that the overall safetyof an extended range operation cannot be better than that providedby the reliability of the propulsion systems, some of the factors

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12-30-88 ~ - AC 12042Arelated to extended range operations are not necessarily obvious.For example, cargo compartment fire suppression/containmentcapability co-uld be a significant factor or operational/maintenancepractices may invalidate certain determinations made during theairplane type design certification, or the probability of systemfailures could be a more significant problem than the probabilityof propulsion system failures. Although engine reliability is acritical factor, it is not the only factor which should beseriously considered in evaluating extended range operations. Anydecision relating to extended range operation with two-engineairplanes should also consider the probability of occurrence ofany condition which would reduce the capability of the airplane orthe ability of the crew to cope with adverse operating conditions.The following is provided to define the concepts for evaluatingextended range operations with two-engine airplanes. This approachensures that two-engine airplanes are consistent with the level ofsafety required for current extended range operations with threeand four-engine turbine powered airplanes without unnecessarilyrestricting operation.

a. Airframe System, A number of airframe systems have aneffect on the safety of extended range operations; therefore, thetype design certification of the airplane should be reviewed toensure that the design of these systems are acceptable for the safeconduct of the intended operation.b Propulsion System. A review of the historical data (1978throuih 1988) for transport aviation two-engine turbofan poweredlarge commercial airplanes indicates that the current safetyrecord, as exem plified by the world accident rate (airworthinesscauses) I is sustained in part by a propu lsion system IFSD rate ofonly about l 02/1000 hours, Although the quality of this safetyrecord is not wholly attributable to the IFSD rate, it is believedthat maintaining an IFSD rate of that order is necessary to notadversely impact the world accident rate from airworthiness causes.Upon further review of the historical data base and inconsideration of the required safety of extended range operation,it is necessary that the achieved performance and reliability ofthe airplane should be shown to be sufficiently high. Whenconsidering the impact of increasing diversion time, it must beshown that the operation can be conducted at a level of reliabilityresulting in no adverse cha nge in risk.c. Maintenance Reliability Program Definition. Since the

quality.of maintenance and reliability programs can have anapprec iable effect on the reliability of the propu lsion system an dthe airframe systems required for extended range operation, anassessment should be made of the proposed maintenance andreliability program's ability to maintain a satisfactory level ofairplane systems reliability for the particular airframe-enginecombination.

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AC 120042A 12-30-88

d Maintenance and Reliability Program Implementation.FolloA ing a determination that the airframe systems and propulsionsystems are designed to be suitable for extended range operations,an indepth review of the applicant's training programs, operations,and maintenance and reliability programs shou ld be accomplished toshow ability to achieve and maintain an acceptable level ofsystems reliability to safely conduct these operations.

e. Human Factors. System failures or malfunctions occurringduring extended range operations could affect flightcrew workloadand procedures. Although the demands on the flightcrew mayincrease, an assessment should be made to ensure that exceptiona lpiloting skills or crew coordination are not required.f Approval Basis. Each applicant (manufacturer or operatoras appropriate) for extended range approva l should show that theparticular airframe-engine comb ination is sufficiently reliable.Systems required for extended range operations should be shown bythe manufacturer to be designed to a fail-safe criteria and should

be shown by the operator to be continuously maintained and operatedat levels of reliability appropriate for the intended operation.(1) Type Design ETOP S Approval. Preceding the type designapproval, the applicant shou ld show that the airframe andpropulsion systems for the particular airplane can achieve asufficiently high level of reliability in service so that safeextended range operations may be conducted. The achievement ofthe required level of propulsion system reliability is determinedin accordance with Appendix 1. (See Paragraph 9.a.) Evidence thatthe type design of the airplane is suitable for extended rangeoperations is norma lly reflected by a statement in the FAA-approvedAirplane Flight Manual (AFM) and Type Certificate Data sheet or

Supp lementa l Type Certificate (See Paragraph EL), which specifiesthe CMP standard requirements for suitability.(2) Inservice Experience. It is also necessary for eachoperator desiring approva l for extended range operations to showthat it has obtained sufficient maintenance 'and operationsexperience with that particular airframe-engine combina tion tosafely conduct these operations. (See,Paragraph 9.b.)(3) O perations Approval. The type design approva l doesnot reflect a continuing airworthiness or operational approva l toconduct extended range operations. Therefore, before approval,each operator should demonstrate the ability to maintain andoperate the airplane so as to achieve the necessary reliability andto train its personnel to achieve competence in extended rangeoperations. The operational approval to conduct extended rangeoperations is made by amendm ent to the operator's operationsspecifications (see Paragraph 10) which includes requisite itemsprovided in the AFM.

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12-30-88 AC 120042A(4) Continuing Airworthiness. From time to time, the FA Amay require that the type design CMP standard be revised to correctsubsequent problems that impede the achievement of the requiredlevel of reliability. The FA A will initiate action as necessary torequire a CMP standard revision to achieve and maintain desiredlevel of reliability and, therefore, safety of the extended range. operation. CMPstandards in effect prior to revision will nolonger be considered suitable for continued extended rangeoperation.

8 - TYPE DESIGN APPROVALCONSIDERATION. When a two-engine typedesign airplane is intended to be used in extended rangkoperations, a determination should be made that the designfeatures are suitable for the intended operation. In some casesmodifications to systems may be necessary to achieve the desiredreliability. The essential airframe systems and the propu lsionsystem for the particular airframe-engine combina tion shou ld beshown to be designe d to a fail-safe criteria and through serviceexperience it must be determined that it can achieve a level ofreliability suitable for the intended operation.a. Request for Approva l. An airplane manufacturer or othercivil airworthiness authorities requesting a determination that aparticular airframe-engine comb ination is a suitable type designfor extended range operation, shou ld apply to the cognizant typecertificate ho lding aircraft certification office. An operatorshould apply similarly, except through their certificate holdingoffice. The responsible aircraft certificationoffice will theninitiate an assessment of the airframe-engine comb ination inaccordance with Paragraphs 8, 9, and Appendix 1 of this AC.bfailures Criteria. The applicant shou ld conduct an evaluation ofand failure combinations based on engineering andoperational consideration as well as acceptab le fail-safemethodo logy. The analysis shou ld consider effects of operationswith a single engine, including allowance for additiona l stressthat cou ld result from failure of the first eng ine. Unless it canbe shown that equivalent safety levels are provided or the effectsof failure are minor, failure and reliability analysis should beused as guidance in verifying that the proper level of fail-safedesign has been provided. The following criteria are applicable tothe extended range operation of airplanes with two engines:

(1) Airframe systems should be shown to comp ly withSection 25.1309, of the Federal Aviation Regulations,Amendment 25-41.

(2) The propu lsion systems should be shown to comp ly withSection 25.901, of the Federal Aviation Regulations,Amendment 25-40.

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AC 120-42-A 12-30-88

(i) Engineering and operational judgment applied inaccordance with the guidance outlined in Append ix 1 should be used.to show that the propu lsion system can achieve the desired level ofreliability. This determination of the propu lsion systemreliability is derived from a world-fleet data base containing allIFSD events, all significant engine reliability problems, andavailab le data on cases of significant loss of thrust, includingthose where the engine failed or was throttled-back/shut down bythe pilot. This determination shou ld take due account of theapproved maximum diversion time'and rectification of identifiedengine design problems, as well as events where in-flight startingcapability may be degraded.

(ii) Contained engine failure, cascad ing failures,conseq uential damage or failure of rema ining systems or equipmentshould be assessed in accordance with Section 25.901 of the FARs.(iii) In addition to the flightcrew fuel managementdiscussed inparagraph lO.e.(2)(vii), a means shou ld be provided toalert the flightcrew of a low-fuel quantity condition. The alertshou ld commence at a total fuel quantity available'condition 'equivalen t to no less than one-half hour operation at maximumcontinuous power.

(iv) It shou ld be shown during type design evaluationthat adequa te engine limit margins exist (i.e., rotor speed,exhaust gas temperatures) for conducting.extended duration single-engine operation during the diversion at all approved power levelsand in all expected environmen tal conditions. This assessmentshou ld account for the effects of additiona l engine loading de mands(e.g., anti-ice, electrical, etc.) which may be necessary duringthe single-engine flight phase associated with the diversion.(Reference Appendix 4, Paragraph la(5).)

(3) The safety impact of an uncon tained engine failureshould be assessed in accordance with Sections 25.903, 33.19, and33.75 of the FAR.(4) The APU installation, if ,required for extended rangeoperations, should meet the app licable Part 25 provisions (SubpartE - Powerplant Provisions, through Amendment 25-46) and anyadditiona l requirements necessary to demonstrate its ability toperform the intended function as specified by the FA A following areview of the applicant's data. If a 'certain extended range

operation may necessitate in-flight start and run of the APU, itmust be substantiated that the APU has adequa te reliability forthat operation.(5) Extended duration, single-en gine operations shou ld not 'require exceptiona l piloting skills and/or crew coordination.Considering the degradation of the performance of the airplane typewith a single-engine inoperative, the increased flightcrewworkload, and the malfunction of rema ining systems and equipment,

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12-30-88 _ AC 120942Athe impact on flightcrew procedures should be minimLed.Consideration should also be given to the effects of continuedflight with an engine and/or airframe system inoperative on theflightcrew's and passengers' physiolog ical needs (for example,temperature control).

(6) It should be demonstrated for extended durationsingle-engine operation, .that the remaining power (electrical,hydraulic, pneumatic) will continue to be available at levelsnecessary to permit continued safe flight and landing, and toprovide those services necessary for the overall safety of thepassengers and crew. Unless it can be shown that cabin pressurecan be maintained on single-engine operation at the altitudenecessary for continued flight to a suitable airport, oxygenshould be available to sustain the passengers and crew for themaximum diversion time. .(7) In the event of any single failure, or any combinatiorof failures not shown to be extremely improbable, it should be

shown that electrical power is provided for essential flightinstruments, warning systems, avionics, communications,navigation, required route or destination guidance equipment,supportive systems and/or hardware and any other equipment deemednecessary for extended range operation to continue safe flight andlanding at a suitable airport. Information provided to each pilotshould be of sufficient accuracy for the intended operation./03) Three or more reliable, independent alternatingcurrent (AC) electrical power sources should be available. As aminimum, each electrical source should be capable of powering theitems specified in Paragraphs 8.c.M) and 8.c.(7). If one or moreof the required electrical power sources are provided by an APU,

hydraulic system, or ram air turbine, the following criteria applyas appropriate:.(1) The APU when installed, should meet the criteriain Paragraph 8.bJ4).

{ii) The hydraulic power source should be reliable.To achieve this reliability, it may be necessary to provide two ormore- independent energy sources (e.g., bleed air from two or morepneumatic sources) l(iii) Ram air turbine (RAT) deployment should be .demonstrated to be sufficiently reliable in deployment and use.

The RAT should not require engine dependent power for deployment.(9) It should be shown that adequate status monitoringinformation and procedures on all critical systems are availablefor the flightcrew to make pre-flight, in-flight go/no-go anddiversion decisions.

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(10) Extended range operations are not permitted withtime-related cargo fire limitations less than the approved maximumdtversion time in still air conditions (including an allowance for15 minutes holding and an approach and landing) determined bycons idering other relevant failures, such as an engine inoperative,and combinations of failures not shown to be extremely improbable.(11) Airframe and propulsion ice protection should beshown to provide adequate capability (aircraft controllability,etc.) for the intended operation. This shou ld account forprolonged exposure to lower altitudes associated with the engine-out diversion, cruise, holding, approach and landing.(12) Although a hardware/design solution to a problem ispreferred, if scheduled maintenance, replacement, and/orinspection are utilized to obtain type design approval forextended range operation, then the specific maintenanceinformation should be easily retrievable and clearly referencedand identified in an appropriate maintenance document.

CL Ana lysis of Failure Effects and Reliab ility.(1) General.- The analysis and demonstration of airframeand propulsion system failure effects and reliability provided bythe applicant should be based on inservice experience as requiredby Paragraph 9, and the expected longest diversion time forextended range routes likely to be flown with the airplane. If itis necessary in certain failure scenarios to conside r less time dueto time-limited systems, the next lower time of 75 or 120 minuteswill be established as the approved diversion time.(2) Propulsion Systems.

.(1) An assessment of the propulsion systemsreliability for particular airframe-engine comb inations should bemade in accordance with Appendix 1.(ii) The analysis should consider:

(A) Effects of operation with a single-propu lsion system (i.e. high-power demands, bleed requirements,etc.) and include probable damage that cou ld result from failureof the first engine .(B) Effects of the ava ilability and management

of fuel for propulsion system operation (i.e. crossfeed valvefailures, fuel mismanagement, ability to distingu ish and isolateleaks, etc.).(C) Effects of other failures , externalconditions, maintenance and crew errors that could jeopardize theoperation of the remaining propulsion system should be examined.

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12-30-88 .. AC 120942A(D) Effect of inadvertent thrust reverserdeployment, if not shown to be extremely improbab le (includesdesign and maintenance)*

(3) Hydraulic Power and Flight Control. Consideration ofthese systems may be combined, since many commercial airplanes havefull hydraulically-powered controls. For airplanes with all flightcontrols being hydrau lically powered, evaluation of hydraulicsystem redundancy should show that single failures or failurecombinations not shown to be extremely improbab le do not precludecontinued safe flight and landing at a suitable airport. As partof this evaluation, the loss of any two hydraulic systems and anyengine should be assumed to occur unless it is established duringfailure evaluation that there are no sources of damage or thelocation of the damage sources are such that this failure conditionwill not occur,

(4) Electrical Power. Electric power is provided to asmall group of instruments and devices required for continued safeflight and landing, 'and to a much larger group of instruments anddevices ne eded to allow the flightcrew to cope effectively withadverse operating conditions. Multiple sources (engine drivengenerators, APU's, etc.) should be provided to meet both the"continued safe flight and landing requirements" and the "adverseconditions requirements" as amplified in AC 25.1309~1A. A reviewshould be conducted of fail-safe and redundancy features supportedby a statistical analysis considering exposure times established inParagraph 8.cJP).(5) Equipment Cooling. The data should establish that thenecessary electronic equipment for extended range operation hasthe ability to operate acceptably considering failure modes in thecooling system not shown to be extremely improbable. Adequateindication of the proper functioning of the cooling system shouldbe demonstrated to ensure system operation prior to dispatch andduring flight.(6) Cargo Compartment. The cargo compartment design andfire protection system capab ility (if necessary) should beconsistent with the following:

.(1) Design. The cargo compartment fire protectionsystem integrity and reliability should be suitable for theintended operation considering fire detection sensors, linermaterials, etc.(ii) Fire Protection. An analysis or tests sho uld beconducted to show, considering approved maximum diversion in stillair (including an allowance for 150minute holding and/or approach.and land), that the ability of the system to suppress orextinguish fires is adequate to ensure safe flight and landing at asuitable airport.

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AC 120-42A 12-30-88_ ~(7) Communication, Navigation, and Basic FlightInstruments (Altitude, Airspeed,-- Attitude and--Heading).- It shouldbe shown that, under all combinations of propulsion and/or airframesystem failures which are not extremely improbable, reliablecoimmunication, sufficiently accurate navigation, basic flightinstruments, and any route and destination guidance needed to

comply with contingency procedures for intended operation will beavailable to each pilot. .(8) Cabin Pressurization. A review of fail-safe andredundancy features should show that the loss of cabin pressure isimprobable under single- engine operating conditions. FAA-approved airplane performance data should be available to verifythe ability to continue safe flight and landing after loss ofpressure and subsequent operation at a lower altitude.(9) Cockpit and Cabin Environment. It should be shownthat an adequate cockpit and cabin environment is preservedfollowing all combinations of propulsion and electrical system

failures which are not shown to be extremely improbable.d Assessment of Failure Conditions. In assessing the fail-safe ieatures and effects of failure conditions, account should betaken of:

(1) The variations in the performance of the system, theprobability of the failure(s), the complexity of the crew action,and the type and frequency of the relevant crew training.(2) Factors alleviating or aggrava ting the direct effectsof the initial failure condition, including consequential orrelated conditions existing within the airplane which may affect

the ability of the crew to deal with direct effects, such as thepresence of smoke, airplane accelerations, interruption of air-to-ground communication, cab in pressurization problems, etc.(3) A flight t est should be conducted by the manufacturerand witnessed by the FAA type certificate holding office tovalidate expected airplane flying qualities and performancecons idering eng ine failure, electrical power losses, etc. The.adequacy of remaining airplane systems and performance andflightcrew ability to dea l with the emergency cons idering rema iningflight deck information will be assessed in all phases of flightand anticipated operating conditions. Depending on the scope,content, and review, by the responsible FAA Aircraft Certification

Office, of the manufacturer's data base, this flight test cou ld beused as a means for approving the basic aerodynamic and engineperformance data used to establish the airplane performanceidentified in Paragraph lO.d.(6).e. FAA Airplane Assessment Report. The assessment of thereliability of propu lsion and airframe systems for a particular

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12-30-88 AC 120042A_ ~airframe-engine combination will be contained in an FAA AirplaneAssessment Report. The report will be provided to the TransportAirplane Certification Directorate (FAA Northwest Mountain Region)for approval and to the directors of Flight Standards, and AircraftCertification Service, for review and concurrence. Followingapproval of the report, the propulsion and airframe systemrecommendations will be included in an FAA-approved document thatestablishes the CMP standard requirements for the candidateairplane. This document will then be referenced in the OperationsSpecification and the Airplane Flight Manual.

f ETOPS Type Design Approval. Upon satisfactory completionof the airplane evaluation through an engineering inspection andtest program consistent with the type certification procedures ofFAR Part 21 and sufficient inservice experience data:(1) The type design approval will be reflected in the FAA-approved AFM or supplement, and Type Certification Data Sheet orSupplem ental Type Certificate which contain directly or by

reference the following pertinent information, as applicable:.(1) Spec ial limitations (if necessary) I includingany limitations associated with a maximum diversion timeestablished in accordance with Paragraph 8cU) l(ii) Markings or placards (if required);

(iii) Revision to the performance section inaccordance with paragraph lOd(6);(iv) The airborne equipment, installation, andflightcrew procedures required for extended range operations;w Description or reference to a documentcontaining the approved airplane configuration CMP standard:

(vi) A statement to the effect that:"The type design reliability and performanceof this airframe-engine combination has been evaluated inaccordance with AC 120042A and found suitable for (state maximumdiversion time) extended range operations with the incorporationof the approved airplane configuration CMP standard. This findingdoes not constitute approval to conduct extended rangeoperations."

g T_lypeDesign Chanqe Process. The FAA directorateresponsible for the certification of the type design will includethe consideration of extended range operation in its normalmonitoring and design change approval functions. 'Any significantproblems which adversely effect extended range operation will becorrected. Modifications or maintenance actions to achieve ormaintain the reliability objective of extended range operations

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will be incorporated into the type design CMP standard document.The FAA will normally coordinate this action with the affectedindustry. The Airworthiness Directive process will be utilized asnecessary to effect a CMP standard change. The current CMPstandard will be reflected in Part D of each ETO PS operator'soperations specifications.h Continued Airworthiness. The type design CMP standardwhich'establishes the suitability of an airplane for extendedrange operations defines the minimum standards for the operation.Incorporation of additional modifications or maintenance actionsgenerated by an operator or manufacturer to enhance or maintain thecontinued airworthiness of the airplane may be made through thenormal approval process. The operator or manufacturer (asappropriate) should thoroughly evaluate such changes to ensure thatthey do not adversely effect reliab ility or conflict withrequirements for extended range approval.

9 INSERVICE EXPERIENCE. In establishing the suitability oft;pe design in accordance with Paragraph 8 of this AC and as a aprerequisite to obtaining any operational approval, in accordancewith the criteria of Paragraph 10 of this AC, it should be shownthat an acceptable level of propulsion system reliability has beenachieved in service by the world fleet for that pa rticularairframe-engine combination. The candidate operator needs also toobtain sufficient maintenance and operation familiarity with theparticular airframe-engine combination in question.a. Prior to the type design approval, Paragraph 8, it shouldbe shown that the world fleet of the particular airframe-enginecombination for which approval is sought can or has achieved, as

determined by the FAA (see Appe ndix 11, an acceptable andreasonab ly stable leve l of single propulsion system in-flightshutdown (IFSD) rate and airframe system reliability. Engineeringand operational judgment applied in accordance with the guidanceoutlined-in Appendix 1 will then be used to determine that the IFSDrate objective for all independent causes can be achieved. Thisassessment is an integral part of the determination inParagraph 8.bJ2) for type design approval. This determination ofpropulsion system reliability is derived from a world fleet data-base containing all in-flight shutdown events and significantengine reliability problems, in accordance with requirements ofAppe ndix 1. This determination will take due account of theapproved maximum diversion time, rectification of identifiedsystem problems, as well as events where in-flight startingcapab ility may be degraded.

b Each operator requesting approval to conduct extendedrange operations should have operational inservice experienceappropriate to the operation proposed. Subparagraphs 9.b.W (2) (3)contain guidelines for requisite inservice experience. Theseguidelines may be reduced or increased following review andconcurrence on a case-by-case basis by the Director, Flight14 par 8


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12-30-88 AC 120~42A.Standards Service. Any reduction or increase in inservice'experience guidelines will be based on an evaluation of the .operator's abil'ity and competence to achieve the necessary'reliability for the particular airframe-engine combination inextended range operations. For example, a reduction in inserviceexperience may be considered for an operator who can show extensiveinservice experience with a related engine on another airplanewhich has achieved acceptable reliability. In contrast, anincrease in inservice.experience may be considered for those caseswhere heavy maintenance has yet to occur and/or abnorm ally lownumber of takeoffs have occurred,

(1) 750Minute Operation. Consideration may be given tothe approval of 75-minute extended range operations for operatorswith minimal or no inservice experience with the airframe-enginecombination. This determination considers such factors as theproposed area of operations, the operator's demonstrated ability to 1successfully introduce airplanes into operations, and the qualityof the proposed maintenance and operations programs.(2) 1200Minute Operation. Each operator requestingapproval to conduct extended range operations with a maximumdiversion time of 120 minutes (in still air) should have 12consecutive months of operational inservice experience with thespecified airframe-engine combination. Inservice experienceguidelines may be increased or decreased by the Director, FlightStandards Service, as noted in Paragraph 9b.(3) 1800Minute Operation. Each operator requestingapproval to conduct extended range operations with a maximumdiversion time of 180 minutes (in still air) should havepreviously gained 12 consecutive months of operational inservice

experience with the specified airframe-engine combination inconducting 120-minute extended range operations. Inserviceexperience guidelines may be reduced or increased by the Director,Flight Standards Service, as noted in Paragraph 9b. Likewise, thesubstitution of inservice experience which is equivalent. to theactual conduct of 1200minute ETO PS operations will also beestablished by the Director, Flight Standards Service, on a case-by-case basis.10 OPERATIONAL APPROV ALCONSIDERATIONS. Paragraphs 10.a. through1O:h. detail the criteria for operational approval of extendedrange operations with a maximum diversion time of 120 minutes to aien route alternate (at single-engine inoperative cruise speed instill air). Appendices 4 and 5 serve two functions; first, theyprovide expanded explanation of the elements contained in thisadvisory circular and second, they serve to differentiate thecriteria for approval of operations less than 120 minutes(75 minutes) and beyond "120 minutes (180 minutes) l For approvalof 750minute operations, only certain requirements of this ACapply* (See Appendix 5.)

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