(2)
Test Standby Mode.
(a)
On control panel set CAB ALT to field altitude and CABIN RATE at pip mark.
(b)
Set CABIN PRESS BARO SET to field barometric pressure (QFE), or to the corrected sea level pressure (QNH).
(c)
Set CAB ALT to 200 feet below field altitude (QNH), or to a minus 200 feet (QFE).
(d)
Switch selector to STBY and check that STANDBY light comes on.
(e)
Place FLT-GRD switch to GRD and check that outflow valve is open, or opens.
(f)
Check standby mode flight operation.
1) Open landing gear lights circuit breaker and check that outflow valve goes to the full closed position in 10 to 40 seconds as observed on the VALVE position indicator.
2) Place FLT-GRD switch to FLT. 3) Close landing gear lights circuit breaker and check that outflow valve remains closed. 4) Increase CAB ALT control setting to 200 feet above field altitude and check that outflow valve goes to full open.
(g) Check airplane barometric correction.
1) Set CAB ALT control setting to field elevation.
CAUTION: DO NOT EXCEED NORMAL BAROMETER OPERATING RANGE OF 28.10-31.00 IN. HG (952-1049 MB). EXCEEDING RANGE MAY CAUSE MALFUNCTION OF PRESSURIZATION SYSTEM.
2) Set CABIN PRESS BARO-SET counter to 0.3 in. Hg (10 mb) above field barometric pressure and check that outflow valve goes closed.
3) Set CABIN PRESS BARO-SET counter to 0.3 in. Hg (20 mb) below field barometric pressure and check that outflow valve goes open.
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4) Set CABIN PRESS BARO-SET counter to field barometric pressure. 5) Select DC MANUAL OPEN. Ensure that outflow valve opens. 6) Remove electrical power if no longer required.
E. Automatic Mode Test
(1)
Prepare to test Automatic Mode.
(a)
Refer to par. 1.B. (1).
(b)
Install vacuum source on airplane pitot-static system, or on front of pressure controller after removing static sense line.
(2)
Test Automatic Mode.
(a)
Place mode selector switch to AUTO and check that AUTO FAIL, STANDBY, OFF SCHED DESCENT and MANUAL lights are off.
(b)
Check ground pressurized and ground unpressurized circuits.
1) Place FLT-GRD switch to FLT and check that outflow valve goes to the full closed position in approximately 30 seconds as observed on the VALVE position indicator.
2) Place FLT-GRD switch to GRD and check that outflow valve goes to full open within 30 seconds as observed on the VALVE position indicator.
(c) Check automatic fault detector operation. 1) Place FLT-GRD switch to FLT. 2) Place mode selector switch to CHECK and check that AUTO FAIL and
STANDBY lights come on. 3) Place FLT-GRD switch to GRD and check that AUTO FAIL and STANDBY lights go out. 4) Wait at least 30 seconds and then place FLT-GRD switch to FLT.
NOTE: Elapsed time periods are required for initial fault conditions to clear.
5) Place mode selector switch to AUTO and check that AUTO FAIL and STANDBY lights come on.
6) Place mode selector switch to STBY and check that AUTO FAIL light goes out.
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7) Wait at least 30 seconds and then place mode selector switch to AUTO and check that STANDBY light goes out. 8) Open AUTO AC circuit breaker and check that AUTO FAIL light comes on immediately and that STANDBY light comes on in 11 to 19 seconds. 9) Close AUTO AC circuit breaker and check that STBY and AUTO FAIL light goes out. 10) On airplanes with three CABIN pressure fittings on front of controller, check that AUTO FAIL and STBY lights go out. 11) On airplanes with one CABIN pressure fitting on front of controller, a) Place mode selector switch to STBY and check that AUTO FAIL lights go out.
NOTE: At this time a delay of 20 to 30 seconds is necessary to allow induced voltage to bleedoff.
b) Place mode selector switch to AUTO and check that STANDBY lights go out.
(d)
Check automatic fault detector operation with standby mode inoperative. 1) Place FLT-GRD switch to FLT. 2) Open STANDBY AC circuit breaker. 3) Open AUTO AC circuit breaker and check that the AUTO FAIL light comes on,
but STANDBY light does not. 4) Place FLT-GRD switch to GRD and check that AUTO FAIL light goes out. 5) Close STANDBY AC circuit breaker. 6) Close AUTO AC circuit breaker.
(e)
Check automatic mode barometric correction circuits. 1) Set FLT ALT control to 35,000 feet. 2) Set LAND ALT control to field altitude. 3) Place FLT-GRD switch to FLT and wait for outflow valve to close. 4) Set CABIN PRESS BARO-SET counter to field pressure.
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