(b)
Operate the APU for a minimum of five minutes.
(c)
During the APU operation, examine the fuel-cooled oil cooler for signs of oil and fuel leakage.
(d)
If you find oil or fuel leakage, then do these steps to repair the leakage: 1) Do this task: APU Usual Shutdown (AMM 49-11-00/201). 2) Attach a DO-NOT-OPERATE tag to the APU control switch on
the P5 overhead panel. 3) Repair the cause of the oil or fuel leakage. 4) Remove the DO-NOT-OPERATE tag from the APU control switch
on the P5 overhead panel.
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747-400 MAINTENANCE MANUAL
5) Do this task: APU Starting and Operation (AMM 49-11-00/201). 6) During the APU operation, examine the fuel-cooled oil cooler for signs of oil and fuel leakage. 7) If you find oil or fuel leakage, do the leakage repair again.
(e) If it is not necessary to do other tasks, do this task: APU Usual Shutdown (AMM 49-11-00/201).
S 614-032
(4)
Make sure the APU oil system is full. To check the oil level, do this task: APU Oil Tank Replenishing (AMM 12-13-02/301).
G.
Put the Airplane Back to Its Usual Condition
S 414-031
(1)
Close the left APU access door, 317AL, and right APU access door, 318AR:
(a)
Remove the two quick-release pins, disconnect the two hold-open rods and put the two hold-open rods in the two clips on the right access door.
(b)
Install the two quick-release pins in the two brackets on the right APU compartment bulkhead.
(c)
Lift the right access door until you can install the lanyard on the pin at the aft APU compartment bulkhead.
NOTE: The lanyard will hold the right access door on the APU
____
compartment bulkhead.
(d)
Remove the two quick-release pins, disconnect the two hold-open rods and put the two hold-open rods in the two clips on the left access door.
(e)
Install the two quick-release pins in the two brackets on the left APU compartment bulkhead.
(f)
Make sure the insulation covers are correctly attach to the APU compartment firewall.
(g)
Lift the left access door until the two APU access doors are approximately aligned.
(h)
Close the two APU access doors.
(i)
Close the six latches on the right access door.
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APU OIL INDICATING SYSTEM - DESCRIPTION AND OPERATION
_____________________________________________________
General
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A. The APU oil indicating system has an oil temperature sensor, low oil pressure switch, oil level sensor and oil filter differential pressure indicator.
Oil Temperature Sensor (Fig. 1)
______________________
A. The oil temperature sensor sends an electrical signal to the APU controller for the oil temperature downstream of the oil filter element. The oil temperature sensor has a stainless steel body and a copper tip. The location of the oil temperature sensor is on the oil sensor housing.
Low Oil Pressure Switch (Fig. 1)
_______________________
A. The low oil pressure switch is open in its normal position but will close when the oil pressure reaches 55 to 60 psig. The switch re-opens when the oil pressure reduces to 50 psig minimum. The location of the low oil pressure switch is on the oil sensor housing.
Oil Level Sensor (Fig. 1)
________________
A. The oil level sensor provides a continuous electrical signal to the controller based on liquid levels in the oil tank. The APU controller converts the signal into an oil quantity. The capacitance type sensor probe is fitted vertically into the oil tank through an inlet boss on the bottom right-hand side of the load gearbox.
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