Service difficulty report · Switch · Boeing 757222

Difficulty date
July 18, 2010
Submitted
July 21, 2010
Operation
Air carrier
Aircraft
N543UA
Make and model
Boeing 757222
Aircraft serial
25698
Aircraft time
71,816 hours, 20,833 cycles
Engine
Pwa PW2037
Part
Switch
Part number
1103P1341
Part serial
94
Condition
Faulty
Location
Position A
Component
Apu
Component part number
380029817
Stage of operation
IN
How discovered
9
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

APU INOPERATIVE. 'LOP' ON APU BITE WITH AUTO SHUTDOWN DURING START AT 95 PERCENT RPM (ECU DOES NOT MONITOR LOP UNTIL 95 PERCENT). WITH LOP FAULTS PRIOR TO APU RPLM'T 10JULY, ACP'D WIRING RING OUT BETWEEN LOP SWITCH, PIN 1 TO ECU BENCH PLUG, PIN C5 AND GRD IS AT LOP SW, PIN 2--ALL CHECKS OK. REPLACED PRESS AND GEN SCAV FILTERS REF MM (FILTERS WERE CLEAN). WITH DIRECT READING GAUGE AT LUBE PUMP TEST PORT, OIL PRESS IS 22 PSI (NORMAL IS 65+-5 PSI). REMOVED DEOIL SOLENOID TO VERIFY FULLY CLOSED, CHECKED OK. REINSTALLED DEOIL SOLENOID. VERIFIED GEN SCAV PUMP OPS NORMAL WITH APPROX 4-6 OZ'S OIL DRAINING OUT ON REMOVAL OF IT'S CHIP DETECTOR PLUG HOUSING. REPLACED APU FUEL CONTROL. LEAK CHECKS OK, APU OPERATES NORMAL