AUXILLARY VOLUME TANK
CABINPRESSURE
REFERENCEPRESSURE
DISCHARGEPRESSURE
RATEPRESSURE
AIRCRAFT VACUUMPRESSURE TRUESTATIC
PRESSURE
FILTER
TRUE STATIC
ATMOSPHERE
FILTER
SOLENOID CABIN RATE
AIRVALVE CONTROL SELECTOR KNOB
CONTROL
CHAMBER / PORT PORT "1"
ABSOLUTE PRESSURE REGULATOR
TRUESTATIC
ATMOSPHERE
SAFETY VALVE CABIN VESSELBOUNDARY DISCHARGE
CabinPressureControlSystemSchematic Figure 1
EFFECTIVITY: 040-999
21-30-00 Jan
21-30-00 Jan 10/90
PIPERAIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
A. PressurizationControl(continued)
... 425 F
IgnitionTorque GroundBleed
Air Switch
BLEEDAIR PressSwitchAutofeather BLEEDAIR
SHUTOFF P3-13 PSI SHUTOFF
VALVE P25-37 PSI VA
ON/OFFSolenoid BleedAir ON/OFF
HI/LO Solenoid Valve ToECU
425 F 475 475
BleedAirHotWarning
:..........................................
EmergencyPressValve
I
BleedAir ControlandCabinPressurizationSchematic (Sheet1 of 2)
Figure 2
EFFECTIVITY:
040-999
2Jan
10/90
30-00
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. PressurizationControl(continued)
STA 57.00
18 PSI
PRESSURE REGULATOR RELIEFVALVE
CABINDOOR SEAL
SOLENOID
VALVE
EJECTOR
SAFETYVALVE
ABSULUTEPRESSURE REGULATOR(13.500)
SAFETYVALVE OUTFLOWVALVE
STA 3320
CABINALTITUDESWITCH(11,700) CABINALTITUDESWITCH(12,000)
ABSOLUTELY PRESSURE
(ABSOLUTEPRESSURESWITCH) EMERGENCYPRESSURE CABINDIFFERENTIALPRESSURE SWITCH (6.4-6.5 PSI)
STATION57.00
FILTER
AUX VOLUME TANK
REGULATOR
SHUTOFF VALVE VALVES
SUCTION
GAGE
-5 PSI
REGULATED UNREGULATED CONTROLLED SUCTION
SUCTION TO TO TO SUCTION
ABSOLUTE
EJECTORVACUUM
PRESSURE
RELIEF
REGULATOR
SOLENOID
BleedAirControlandCabinPressurizationSchematic(Sheet2 of 2)
Figure 2
EFFECTIVITY: 10/90
21-30-00 Jan
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. PressurizationControl(continued)
1. ComponentDetailedDescriptions
(a) CabinOutflowValve(Figure3)
Theoutflowvalvecontainsa headandbasesection.Theheadsectioncontainsport2
(controllerconnection)anda pluggedcabinairport.Mountedontheheadisthedifferential
control,containingport1(truestaticatmosphereconnectionwithorifice).Thebaseassemblyenclosesapoppetoutflowvalvewhichsitsonabaseassemblysurfacewhenintheclosed position.
(b) CabinSafetyValve(Figure3)
Thesafetyvalvecontainsa headandbasesection.Theheadsectioncontainsport2 depressurizationconnectionandacabinairfilterwithorifice.Mountedontheheadisa differentialcontrol,containingport1(truestaticatmosphereconnectionwithorifice).Thebase assemblyenclosesa poppetoutflowvalvewhichsitsona baseassemblysurfacewheninthe closedposition.
(c) CabinPressureController(Figure 4)
Thecontrollerbodyconsistsofthreeelements: (1.) Thelowerelementformsachamberopentocabinpressureandhousestheabsolute bellows.Itisalsothefaceofthecontrollerthatcontainscabinaltitudeselectorknoband cabinratecontrolknob.
(2.) Themiddleelement,whenassembledtothelowerelement,completesandsealsthe cabinpressurechamberfromtherestofthecontrollerwitha sealingdiaphragm.The oppositesidesofthemiddleelementformsaratepressurechamberwhichhousesthe
ratespring.
(3.) Theupperelement,whenassembledtotheratediaphragmandtheothertwoelements,formsa referencepressurechamberwhichhousesthereferencepressuremeteringvalve andmeteringvalvefollowerspring.Thiselementalsocontainsthevariousair connectionstoinstallthecontrollerintothecabinpressurecontrolsystem.
(d)AuxiliaryVolumeTank
Thetankisa smallsealedchambernexttothecontroller.Whenconnectedtothecontroller,it providesadditionalvolumetotheratepressurechamberinthecontrollerandprovidesgreater accuracyofthecabinrate-of-control.
(e)AbsolutePressureRegulator(Figure502)
Theabsolutepressureregulator aspring-loaded, valveandan
contains closedballmetering
aneroidbellows.Thebellowssensecabinpressureandoverridespringclosingforcewhen
cabinpressurereducestoapproximately13,500+ 1,000feet. Theunitisportedsothat
openingtheball-meteringvalveallowscabinpressureto entertheoutflowvalveheadwith
sufficientflowcapacitytofullyclosetheoutflowvalveandshutoffthepneumaticcontrol
pressurefromthecontroller.
EFFECTIVITY:
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