EFFECTIVITY:
040-999
21-30-00
PAGE

PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. Pressurization
Control (continued)
CHART 1

FAULTISOLATION(PRESSURIZATIONSYSTEM)(Sheet3 of 5)
Fault
Pressurizedoperation before takeoff and afterlanding. (continued)
Cabin exceeds full positive differentialcalibrated setting.
Cabinclimbs and descends at a fixed rate regardless of rate selection.
Cabinrate exceeds selected rate valve during aircraft climb to cruise altitude.
Cabinpressurerapidly
increasesor decreases with reselection of cabin
altitude.
Cause

Broken wiring to the vacuumrelief solenoid.
Loose or damaged pneumatic tubebetween solenoid valve andsafetyvalve.
Internalmalfunctionin the safety valve.
True static atmospheretube blockedor not connected on isobaric valve and safety valve.
Looseor damaged pneumatic tubingfrom port 1"of safety and isobaric valve to atmosphere.
Internalmalfunctionin controller.
Malfunctionin controller.
Defectivecabin rate of
climb indicator.
Malfunctionin controller.
Remedy
Repairwiring.
Check tube connectionsor replacedamagedtube.
Removeandreplacevalve.
Securelyconnectorremove blockagefrom the true static atmospheretubeon isobaric valve and safety valve.
Repairor replace tubing.
Removeandreplace controller.
Removeand replace controller.
Removeandreplace
indicator.
Removeand replace controller.
EFFECTIVITY: 040-999

Jan 10 21-30-00
Jan 10/90 21-30-00
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. Pressurization Control (continued)
^ CHART1 FAULTISOLATION(PRESSURIZATIONSYSTEM) (Sheet4 of 5)
Fault  Cause Remedy
Cabinaltitudeexceeds Lossofairflowintocabin. Repairbleedairsupply
selectedvalue.  of ECUsystem.
Internalmalfunctionin  Removeandreplacevalve.
isobaricvalve.
Internalmalfunctionin  Removeandreplacevalve.
safetyvalve.
Internalmalfunctionin  Removeand replace
controller.  controller.
Excessivecabinleakrate.  Seal leaks.

Cabinpressurewill not Dumpvalvepartiallyopen. Closevalve;adjustvalve maintaincontrolsetting. controlcables.
Defectiveisobariccontrol  Removeandreplacevalve.
valve.
Defectivesafetyvalve.  Removeand replacevalve.
Defectivepressurizedair Removeorrepairvalve. dump valve.
Defectivecabinaltitude Removeand replacecabin controller. altitudecontroller.
Pressurizationductleakage.  Locate leak andtighten connection.
Cabinleakage Locateandrepairleak. Defectivecabinaltitude Removeandreplacegauge. pressuregauge.
Foreignmatteron isobaric Cleanvalveseats.
outflowcontrolvalve or
safetyvalve seats.

Leak in outflowisobaric Locate leak andtighten
valvecontrolline. connection.

EFFECTIVITY:
040-999
21-30-00 PAGE5

PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. PressurizationControl(continued)
CHART 1 FAULTISOLATION (PRESSURIZATION SYSTEM)
Fault  Cause
Cabinpressureexcessively Isobaricoutflowvalvestatic high. lineclogged.
Defectivecabinoverpressure switch.
Defectivecabinaltitude
pressuregauge.
Safetyvalvestaticvent
clogged.
Defectivesafetyvalve.
Cabindoorunsafelight Latchingrelaystickingin
will notgo out. the openposition.

Switchor switchesin door
frameout of adjustment.
Defectivepressureswitch.
Shortto ground.
Cabindoor unsafelight  Circuitbreakeropen.
will notcomeon.
Brokenwire or loose
connection.

Nopressureto doorseal.  Leakindoorsealpressure system.
(Sheet5 of5)
Remedy
Cleanstaticline.
Removeand replaceswitch.
Removeand replacegauge.
Cleanventline.
Removeandreplacevalve. Lubricatethe mechanicalparts
(sparingly)with "GlideAir"or
equivalent.
Adjust.

Replaceswitch.
Checkwiringand repair.
Resetcircuitbreaker.
Checkwiringand repair.

Checkand repairdoor
sealpressuresystem.

EFFECTIVITY: 040-999

21-30-00
Jan
10/90
21-30-00
PIPER AIRCRAFT

PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

A. PressurizationControl(continued)
FROM 
ECU 
COALESCER 
WATER 
SEPERATOR 
AMBIENTPRESSURE 
　
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