1IntroductionTheAlliedSignalGCTP331-200ERgasturbineAPUsuppliestheauxiliarypowersystemwithelectricandpneumaticpower.Thisletstheairplaneoperateindependentlyofgroundexternalpowersourcesorthemainengines.Auxiliarypowerisalsoavailableintheair.TheAPUgeneratorsupplies90kVAelectricalpoweratanyaltitude.Pneumaticpressureisavailableuptoanaltitudeof17,500feet（5,300m）.TheAPUcanoperateat100or101percent.TheAPUoperatesat101percentduringthesemodes：intheair,ECSdemand,andmainenginestar（tMES）返回2GeneralDescriptionTheAPUsystemcontainsthesesubsystems：thecontrolsystem,ignition/startingsystem,AUPandgeneratorlubricationsystem,oilindicatingsystem,fuelsystem,airsystem,indicatingsystem,andexhaustsystem.AnAPUcontrollercontrolsAPUsystemfunctionsandisaninterfacewithotherairplanesystems.TheAPUisasingleshaftgasturbineenginewhichdrivesanelectricgeneratorandaloadcompressor.AgearboxonthefrontoftheAPUsuppliespowertodrive;APUaccessories.下一頁返回2GeneralDescriptionThepowerplanthasthesesystemsandcomponents：theauxiliarypowerunit,APUmounts,APUwireharness,APUairintake,APUdrainsandvents.TheAPUenginehasthesecomponents：thetwo-stagecentrifugalflowcompressor;reverseflowannularcombustionchamber,andthree-stageaxialflowturbine.TheAPUandgeneratorlubricationsystemlubricatesandcoolsthesecomponents：theAPUbearings,gearbox,andelectricgenerator.上一頁下一頁返回2GeneralDescriptionTheAPUoilindicatingsystemsuppliesthesedataabouttheAPUoiltoflightdeckdisplays：thetemperature,pressure,andquantity.TheAPUenginefuelsystemsuppliesthepressurizedandmeteredfueltotheAPUcombustionchamber.Italsosuppliesthepressurizedfueltooperatetheinletguidevanesandthesurgevalve.Duringenginestart,theignition/startingsystemturnstheAPUandsuppliesignition.TheAPUairsystemsuppliesthepressurizedairtotheairplanepneumaticsystem.上一頁下一頁返回2GeneralDescriptionInletguidevanescontroltheamountofairsuppliedtotheloadcompressor.Asurgevalvereleasesexcessbleedairoverboard.AcoolingsystemcoolstheAPUcompartmentandtheengineoil.TheAPUindicatingsystemsuppliesAPUEGTdataforflightdeckdisplay.TheAPUexhaustsystemsendstheAPUexhaustgasesoutofthetailcone.上一頁返回3APUInterfacesTheAPUhasinterfaceswiththesesystemsthathaveinformationinotherchapters/sections：theelectricalpower,pneumatic,fireprotection,andEICAS.ExternalambientaircomesintotheAPUairinletplenumthroughanAPUairintakedoor.TheairthatcomesintotheAPUairinletplenumisusedforthesefunctions：cooling,supportcombustion,andpowersource.AhighspeedcoolingfancirculatesairtocooltheAPUcompartmentandtheoil.Theinletguidevane（IGV）actuatorcontrolsthepneumaticoutputoftheAPU.TheIGVopensandclosestoregulatetheamountofairthatcomesintotheloadcompressorsectionoftheAPU.下一頁返回3APUInterfacesTheyarecontrolledinresponsetoaircraftpneumaticdemand.Aflowsensormeasurespneumaticoutput.TheECUusesthisinformationtomoveasurgevalvetopreventaloadcompressorsurge.TheAPUusesacommonoilsystemtocoolandlubricatethesecomponents：thebearings,gearbox,andgenerator.TheAPUgeneratorhasaseparate,non-bypassoilfilter.Ifthegeneratorfails,thefilterprotectstheremainingAPUcomponentsfromdamage.Ade-oilsystempermitseasierstartatcoldtemperatures.上一頁下一頁返回3APUInterfacesThelowoilpressureswitchsignalstheECUwhenthereislowoilpressureinthepressuresupplyline.TheoiltemperaturesensorsuppliesoiltemperatureinformationtotheECU.Thegearboxpressureregulatingvalvecontrolsgearboxpressurization.Atloweraltitudes,thegearboxventstoambient.Athigheraltitudes,highpressureairisusedtopressurizethegearbox.Thispreventsoilfoamintheoilpump.Thegearboxshuttlevalvecontrolstheinputofhighpressureairtopressurizethegearboxabove18,000feet.Theshuttlevalveselectsthesourceofbufferairforthecompressorandcoolingfanbearings.上一頁下一頁返回3APUInterfacesTheAPUenginefuelsystemregulatesanddistributesfuelforenginecombustionandinletguidevanecontrol.Thefuelcontrolunit（FCU）doesthesefunctionforthefuelsupply：itshutsoff,filters,pressurizes,andmeters.ThefuelcontrolunitiselectricallycontrolledbytheECU.Theflowflows.Thesolenoidvalvepreventsexcessivefuelflowintothecombustionchamberduringstart.Fuelmanifoldsandnozzlesgiveeventhedistributionofprimaryandsecondaryfuelflowintothecombustionchamber.上一頁下一頁返回3APUInterfacesTheAPUstartsa28VDCelectricmotor.Asingleignitionunitsendsahighvoltagetotheigniterplugthatcausesignition.ALLoperationsoftheAPUarecontrolledandmonitoredbytheAPUelectroniccontrolunit（ECU）.TwoAPUmonopolessupplyredundantspeed（RPM）signalstotheECU.TheAPUinletpressureandtemperaturesensorssendthesignalsofinletairconditionstotheECU.TheECUusesthisinformationforfuelflowscheduleandsurgeprotection.OperationconditionsoftheAPUgototheEICAScomputersfordisplay.上一頁下一頁返回3APUInterfacesEICASshowsthisinformation：APURPM,EGT,oilstatusmessages,andfaultmessages.OillevelinformationgoesfromtheoilquantitysensordirectlytotheEICAS.EGTthermocouplesmeasureexhaustgastemperature.上一頁返回4APUControlThesearetheAPUflightdeckcontrols：theAPUselector,APUmaintenanceswitch,andAPUfireswitch.TheAPUselectorontheAPUcontrolpanelisusedtostartandshutdowntheAPU.TheAPUmaintenanceswitchcausesengineandAPUdatatoshowonthelowerEICASdisplay.TheAPUfireswitch,onthecargofire/enginecontrolpanel,willshutdowntheAPUwhenpulled.Turnthehandletodischargetheextinguisherbottle.YoucanshutdowntheAPUfromoutsidetheairplanewiththeairshutdownswitch.ThisswitchisontheP40APUremoteshutdownpanelonthenoselandinggearstrut.下一頁返回4APUControlIfthisswitchisoperated,thebatteryswitchmustberecycledtoresetthesystem.TheEICASshowsthesedata：APUexhaustgastemperature（EGT）,APUspeed,andoilstatus.Alert,statusandmaintenancemessagescanalsoshow.上一頁返回5APU’sInstallationandRemovalTheAPUisremovedwithtwofishpolehoistsorasinglehydrauliclift.Eithermethod,theinstallationofanAPUcradle,whichsupportstheAPUduringinstallationandremoval,isnecessary.Thecradleattachestotheleftforwardandbothrightsidemountingbrackets.ToremovetheAPU,disconnecttheseitems：theAPUharness,groundjumpercables,generatorandstartermotorelectricalconnections,APUfuelline,draintankairpressureline,andthreeairducts（pneumaticsystemairsupplyducts,oilcoolingdischargeductandtheexhaustduct）.下一頁返回5APU’sInstallationandRemovalInstalltheseitems：theAPUcradle,fishpolehoists,andgroundsupportequipment.YoumayinstallagroundsupportsaddleassemblyandclipassembliestosupporttheexhaustductandsecurethetubularsupportsduringAPUremoval.ThefishpolehoistsinstallinkeyholeslotspermanentlyattachedtothebottomoftheAPUairinletplenum.Withthehoistinstalled,theAPUweightcanberemovedfromitssupportinstallation.DisconnecttheAPUfromitstubularsupportandloweritoutoftheairplane.IftheAPUisremoved,andthegeneratorisnotinstalled,theinstallationof78poundsofballastweightmountedonthecradleisnecessary.上一頁返回6APUDrainsandVentsWastefuel,oil,andwaterareremovedfromtheAPUbygravity-feddrainsandvents.TherainwaterthatleaksintotheintakeplenumdrainsoverboardontherightsideoftheAPUcompartmentthroughtheAPUplenumdrain.Anairintakehousingandductdrainsendsrainwaterleakageoverboardontherightsideoftheairplane.ThewaterthatcollectsintheinletplenumdrainsintotheAPUco