18 psig appearsonthe test unitdoorsealpressuregauge.If shop airis hooked up,apply equalpressure. (4.) Connecttestunitto proper voltagesourceandturnflowrate valve knobtofullbypass positiontoallowmachineto turn on.
CAUTION: TO PREVENTDAMAGETO RATE OF CLIMB INDICATOR,DO NOT EXCEED4,000 FEETPER MINUTERATESOF CHANGE.
(5.) Turncabinpressurizationflowcontrolvalve so a 2,000to 4,000feet per minuterateof descentis maintained on the rateof climb indicator.Allowcabindifferentialpressureto riseto 6.0 psi onthe cabin differential pressuregauge (CDP).
(6.) When6.0 psi is indicatedon CDP gauge,rotateflowcontrolvalveanddecreaseairflow
rateuntil the cabinrateof climb gaugeindicateszero. (7.) Maintain6.0 psi cabin differentialpressureand zero rate of change. (8.) Observeleak rateon testunitflow meter. Theactualleakageratemustnot exceed60
CFM.
(9) If allowable leakagerate is exceeded,locateleakusingsoapbubbles,mechanic stethoscopeor otherappropriatemethod;repairleakandre-pressurizeby following the aboveprocedures. (10.)Aftercompletionof leakratetest,checkannunciator/warninglightsystemasfollows: (a.) Ensureambientsenselinefromoutflowand safety valvesarecapped. (b.) Securedoorand anyotheropenings;slowlyincreasecabinpressureto a 6.45± 0.05 psigreadingonthe cabin differentialpressuregauge.
(c.) Noteactivationof annunciator/warming lightsystemandensurecabinpressuredoes notexceed6.5 psig. Thelightmustcomeon at 6.45± 0.05 psig.
CAUTION: AFTERCOMPLETIONOF PRECEDINGTESTS,ENSURECAPSARE REMOVEDFROMAMBIENTSENSELINESTO OUTFLOWAND SAFETYVALVESAND ENSURECOTTERPONSARE REPLACED.
EFFECTIVITY:
040-999
21-30-00 PAGE17
21-30-00 Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. PressurizationControl (continued)
3. PressurizationCheck with Test Unit (continued)
(c)TestUnit Operation (continued)
(11.) Prior to any engine runup test, check bleed air, cabin pressurization system, safety and outflow valves as follows: (a.) Safety valve check -Ensure ambient sense line for safety valve is open. Cap outflow valve ambient sense line.
(b.) With cabin pressure stabilized, slowly increase cabin pressure to a 6.2 to 6.4 psi reading on cabin differential pressure gauge to permit opening of safety valve. The test unit cabin rate of climb indicator will indicate a climb when safety valve opens.
(c.) Outflow valve check -Cap ambient sense line for safety valve and open ambient sense line for outflow valve. Repeat preceding step for outflow valve.
(1 2.)After completing safety and outflow valve opening checks, rotate flow control to depressurize cabin and bring pressure to ambient, by observing cabin differential pressure gauge. Secure ambient sense lines in open positions by removing caps and replacing cotter pins.
(13.)Shut down and turn off shop air to test to test unit. Bleed off air pressure in door seal and open cabin door.
(14.)De-energize airplane electrical system and disconnect test unit pneumatic lines from airplane. Connect electrical lines to vacuum relief solenoid, if disconnected and all aircraft pneumatic lines.
(15.)Replaceaccessand trim panels.
4. PressurizationSystem Checkout Procedure
The following procedures are established to sytematically check the function of each cabin
pressure control system element, so that any single or combination or component malfunction is
safely detected and corrected. If a malfunction is detected, it must be corrected immediately.
5. GroundOperationalCheck
WARNING: THE FOLLOWING OPERATIONALCHECK REQUIRES ENGINERUNUPAND ALL SAFETY PRECAUTIONS MUST BE STRICTLY OBSERVED. ALL PERSONNEL WORKINGON THIS CHECK MUST HAVE COMPLETE OPERATIONAL KNOWLEDGEOF POWER PLANTS AND BE FAMILIAR WITH ALL EMERGENCY PROCEDURESOUTLINED IN THE AIRPLANE FLIGHT MANUAL.
(a)
Verify that the cabin door and pilot window are closed and locked.
(b)
Open manual test valve.
NOTE: Make certain that the caps are removed from the outflow and safety valve ambient sense lines.
(c)
Position the right and left bleed air switches ON.
(d)
Verify that the cabin air selector switch is in the CABIN PRESS position.
(e)
Rotate the rate of change control knob to the NOM position.
(f)
Rotate the cabin altitude controller knob until the indicator is at approximately 500 feet above field elevation.
EFFECTIVITY:
040-999 Jan 10/90
21-30-00
Jan 10/90 21-30-00
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCE MANUAL
A. PressurizationControl(continued)
5. Ground Operational Check (continued)
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本文链接地址：夏延飞机维护手册 Cheyenne IIIA PA-42-720 AMM 1(61)
