(2)
Access Panels
1201 Electronic Equipment Access Door
3804 APU Cowl Door
E. Procedure
S 865-090
(1) Prepare for the test:
(a)
Start the APU (AMM 49-11-00/201).
(b)
Let the APU operate at a stable speed with no load applied for 5 minutes.
NOTE: This will make sure fuel is available to the APU.
____
(c) Do the APU usual shutdown (AMM 49-11-00/201).
S 865-091
(2) Set the switch and the circuit breaker:
(a) Set the APU master switch on the P5 forward overhead panel to the OFF position and attach a DO-NOT-OPERATE tag.
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(b) Open this circuit breaker and attach a DO-NOT-CLOSE tag: 1) E3-3 Electrical Shelf, APU Control Unit
S 015-092
(3) Open the APU cowl door:
(a)
Open the latches for the APU cowl door:
(b)
Open the APU cowl door.
(c)
Connect the door support rods.
S 015-093
CAUTION:_______BE CAREFUL WHEN YOU MOVE THE LOWER SHROUD. DAMAGE TO THE SHROUD DRAIN LINES CAN OCCUR.
(4) Remove the lower shroud:
(a)
Hold the lower shroud and open the shroud latches.
(b)
Remove the lower shroud.
S 485-094
(5) Install the test pressure gage:
(a)
Remove the cap from the control-air pressure port on the fuel control unit.
(b)
Disconnect the high-pressure fuel line from the fuel atomizer.
(c)
Connect the test pressure gage, a component of the gage and case set, to the high-pressure fuel line.
S 785-095
(6) Do the opening pressure test for the acceleration limiter valve on the fuel control unit:
(a) Supply external electrical power to the airplane
(AMM 24-22-00/201).
NOTE: The ac power is necessary to operate the aft boost
____
pump in the No. 1 fuel tank.
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(b) (c) Remove the DO-NOT-CLOSE tag and close this circuit breaker: 1) E3-3 Electrical Shelf, APU Control UnitSet the No. 1 AFT FUEL PUMP switch on the P5 forward overhead panel to the ON position.
NOTE:____ If you must use the fuel boost pumps in the center tank, you must have a maintenance person or observer in the flight compartment to continuously monitor the LOW PRESSSURE lights. Turn the applicable fuel boost pump to the OFF position if the LOW PRESSURE light for the center tank stays on.
(d) (e) Set the BAT switch on the P5 forward overhead panel to the ON position.Remove the DO-NOT-OPERATE tag and set the APU master switch on the P5 forward overhead panel to the START position.
NOTE:____ The APU master switch will go back to the ON position. The engine will start to motor after the air inlet door and the APU fuel valve open. After approximately 90 seconds, the APU control unit will stop the engine operation.
(f) (g) (h) While the engine motors, loosen the fuel line nut at the test gage to remove the air from the line.Tighten the fuel line nut.AIRPLANES WITHOUT THE TAFCU; While the engine rpm becomes stable, monitor the cracking pressure of the acceleration limiter valve.
NOTE:____ The cracking pressure must be 60 |3 psig (414 |21 kPa).
(i) AIRPLANES WITH THE TAFCU; While the engine rpm becomes stable, monitor the cracking pressure of the acceleration limiter valve.
NOTE:____ The cracking pressure must be 60 |5 psig (414 |34 kPa).
(j) AIRPLANES WITHOUT THE TAFCU; If the cracking pressure is not in the limits, adjust the acceleration limiter valve as follows:
1) Remove the lockwire from the locknut for the valve adjustment screw.
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