毕业设计论文方案论证报告提要_精品文档.doc
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毕业设计论文方案论证报告提要_精品文档.doc
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Toascertaintheperformancecapabilitiesoftheprototypedevelopmenthardwareunderthenewtwo-fail/operaterequirements,theBA609FlightControlsIPTinitiatedaprogramofpilot-in-the-looptestingofactuatorfailuremodes.ThesetestscomprisedpilotevaluationsofBA609flightcontrolsystemhandlingqualitiesfollowingtheoccurrences:
•Dualelectricalsystemfailures.
•Dualelectricalcomponentfailures.
•Dualhydraulicsystemfailures.
•Dualhydrauliccomponentfailures.
•Singleelectricalsystemcombinedwithsinglehydraulicsystemfailures.
•Singleelectricalcomponentcombinedwithsinglehydraulicsystemfailures.
•Singleelectricalsystemcombinedwithsinglehydrauliccomponentfailures.
•Singleelectricalcomponentcombinedwithsinglehydrauliccomponentfailures.
Foreachtestcondition,theworstcasesystemorcomponentfailuremodewaseitherinitiatedorsimulated.ForEHSVfailures,secondstagespoolswerefailedhard-overinbothdirections,aswellasatnullposition,causingthecylindertohydraulicallylock.Solenoidswerefailedbothopenandclosed.LVDTswereshortedandcoresweresimulatedtostructurallyfail.Bypass,pressurerelief,anddeltapressuresensorhydraulicspoolsweresimulatedtobestuckinanyposition,andtheirspringsweresimulatedasfailed.Foranycomponentwhoseproperfunctioningcouldnotvalidatedeitherinflightorduringpreflightbuilt-intesting(PFBIT),thecomponentwasconsideredtobeanexistingdormantfailure.BecausetheBA609isatiltrotoraircraft,ithasthreedifferentmodesofflight:
airplane,conversion,andhelicopter.Asaresult,testingofeachrelevantfailuremodeconditionineachofthethreeflightmodeswasrequired.
OneareainwhichtheVMSILtestingwasnotrepresentativeoftheactualaircraftwasthestructuralstrengthofthesimulatedflaperonandelevatorsurfaces.Althoughtheflaperonandelevatoractuatortestrigshadbeenmodifiedtorepresenttheaircraftstructuralstiffness,itwasimpracticaltosimulateactualaircraftstructuralstrengthwiththetestrigs.Therefore,actuatorloadsweremonitoredduringtestingtodetermineifacceptablestructuralloadswereexceeded.
BasedonVMSILpilot-in-the-loopevaluations,testdatafromthefailuremodetesting,andarevisedfailuremodeanalysis,itwasconcludedthatallactuatorinstallations(collective,longitudinal,flaperon,andelevator)oftheprototypedevelopmentactuatordesignprovidedunacceptableperformancefortheproductionBA609aircraft.Dualfailuremodetestingrevealedacriticalfailuremodecombinationthatimpactedallprototypedevelopmentactuatorinstallations.TheBA609hydraulicsystemarchitecture,utilizingthreehydrauliccylinderstoactuateeachflightcontrol,placesauniqueimportanceontheproperfunctioningoftheprototypemanifoldbidirectionalpressurereliefvalve(PRV).ProperoperationofthePRVbecomescriticalforfailuremodesthatresultinblockageofthecylinderports(evenmomentarily),suchasanEHSVand/orbypassvalvefailure.FunctionalintegrityoftheprototypePRV,however,couldnotbeverifiedontheaircraft,leadingtoapotentialdormantfailure.Figure15comparesthepotentialactuatorinternalpressuresgeneratedbyablockedcylinderportfortheconventionaltwo-cylinderarchitectureandtheBA609threecylinderarchitecture.Botharchitecturesillustratedrepresentfly-by-wiresystemsusing3,000psisystempressure,equalextend-and-retractcylinderpistonareas,andanexternalairloadequivalentto50%ofstallofonecylinder.
Withaconventionaltwo-cylinderhydraulicarchitecture,ablockedcylinderportcangenerate4,500psiinternalhydraulicpressure.Thehydrauliccomponentproofpressure(asdefinedinbothARP-5440andinFARPart27)requireshydrauliccylinderstowithstand150%ofoperatingpressure(4,500psi)withnoevidencematerialyielding.Therefore,theeffectofablockedcylinderporthasminimalimpactonstructuralsizing.
WiththeBA609three-cylinderarchitecture,ablockedcylinderportcangenerate7,500psiinternalhydraulicpressure.Thisdual-failure-modegeneratedpressurenotonlyexceedsthe150%ofoperatingpressurestandard,butitalsoreachesthelimitoftherecommendedcylinderburstpressure(250%ofoperatingpressure).Theeffectofablockedcylinderportforthisconditionismoredetrimentalintheflaperonandelevatoractuatorscylinders,duetotheirunequalextendend-retractpistonareas,whichamplifyinternalpressureto8,955psiand9,676psi,respectively.Therefore,topreventdamagefromoccurringeithertoanactuatorortheaircraftstructurefromablockedcylinderport,eithertheactuatorsortheaircraftstructureneedstobesizedtowithstandthehigherresultingpressuresandloads,orareliablePRVmustbeincorporatedintoeachactuatormanifold.
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