B. Hydraulic System Failure (continued)
CHART 1
FAULT ISOLATION (HYDRAULIC SYSTEM) (continued)
Fault
Gearoperatesabnorrmally slow or partially.
Selector handle retunns to neutral before cycle is complete.
Cause
Low fluid level.
Leakingor kinked line.
Internal leak in cylinder.
Priority valve out of adjustmentor leaking.
Slowleak in main relief valve. (Enginepump)
Slow leak in hand pump relief valve.
Extemal leakage at selectorvalve.
Oneengine pump inoperative.
Low pump pressure.
Cable,line or obstruction restrictingthe travel required to fully select gear up or down.
Selectorlever out of adjustment.
Ifgear completes cycle (redlight out) doors do notclose, battery output maybe low.
Time relay valve and/or piston release lock out of adjustment.
Time delay valveair locked.
Remedy
Fill p owerpackwith hydr aulicfluid.
Replace line.
Repaair or replace cylinder.
Check valve operation.
Checck system operation.
Check system operation.
Replace damaged O-rings.
Replace pump.
Replacepump.
Check and remove obstruction.
Adjustcontrol.
Check voltage.
Check operation.
Bleedair out by holding selectordown for 30 seconnds,thenmakethree orfo r rapid movements to ne utraland back to dowr.
EFFECTIVITY:
040-999 29-00-00
Jan 10/90
29-00-00
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
B. Hydraulic System Failure (continued)
CHART 1
FAULTISOLATION(HYDRAULICSYSTEM)(continued)
Fault Cause Remedy
Gearretractsorextends beforedoorsopen. Priority valve leaksin power pack. Check valve cracking pressure.
Solenoidvalvestuck in closed position. Turn off power and hand pump doors open. (Note:
With power off solenoid
valve shuttles to door open
and the doors may be opened
without selecting gear up or
down.)
Micro switch on power Check for loose wire or
pack out of adjustment. mounting, or bent bracket.
Doorscome open in flight. (Note: Refer to 32-00-00, Fault Isolation -(Landing Gear) Micro switch on power pack out of adjustment. Adjust micro switch. (Door solenoid should remain in door close position when handle returns to neutral.)
Chart 1.)
Doors adjusted too tight, Loosen adjustment on
actuatorriotlocking. actuator rod end.
Doorsfail to close. Faulty limit switch. Check all indicator lights.
Low electric power Check battery.
supply.
Cannon plug on power Tighten.
pack loose.
Solenoidvalve stuck in door open position. Check wiring to solenoid valve.
Circuit breaker out. Check breaker. (Note: Withoutelectric power,
thegear doors will open
but not close.)
EFFECTIVITY: 040-999
PAGE4 29-00-00
Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
B. HydraulicSystemFailure(continued)
CHART 2
LEADING PARTICULARS, HYDRAULIC POWER PACK
NOMENCLATURE WTC 2135-1
(SeeNote Below) OperatingPressure 1900PSI
Main Relief ValvePressure(Primary) 1900- 1950 PSI HandPump Relief ValvePressure(Secondary) 2025 -2100 PSI HandPumpReliefValve Reseat Pressure 1900-1950PSI
LowPressureThermalRelief Vent Valve'Open" 0 to 100 PSI Low Pressure ThermalReliefVent Valve "Closed" 150 PSI Max. PriorityValveCracking Pressure 600 -650 PSI
HandPumpCheck Valve CrackingPressure 1 to 3 PSI LandingGear PositionRelease 1220- 1250 PSI Time Delay Valve 3 to 9 seconds HydraulicFluid Required MIL-H-5606 WeightDry-Power Pack 10.00pounds
HydraulicFluidFlow Rate (BothPumpsOperating) 1.6 G.P.M. ReservoirOperatingFluid Level (EnginePump) (Minimum-Maximum) 1.82 -2.1 pints ReservoirFluidLevel (Emergency) (StandPipeLevel) 1.22pints
NOTE: Shouldthe values in the textdiffer from the chart values,the chart valuestakeprecedence.
EFFECTIVITY:
040-999
29-00-00 Jan 1090
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. Main
1. Flushing Hydraulic System.
When hydraulic system is contaminated, drain and flush entire system to remove contaminated fluid. Determine cause and type of contamination and proceed as follows:
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