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SDR UALA2010040701164

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Service difficulty report · Fire Loop · Boeing 747422

FAA SDR system

Difficulty date
April 6, 2010
Submitted
April 9, 2010
Operation
Air carrier
Aircraft
N171UA
Make and model
Boeing 747422
Aircraft serial
24322
Aircraft time
77,282 hours, 9,235 cycles
Engine
Pwa PW4056
System (JASC)
2611 · Smoke Detection
Part
Fire Loop
Condition
Shorted
Location
Nr 4 Nacelle
Stage of operation
NR
How discovered
O
Nature of condition
J
Precautionary procedure
O

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

What was found

'ENG 4 FIRE LP B' EICAS STATUS MSG DISPLAYED. ENG 4 FIRE LOOP B FIRE OR FAULT OUTPUT. CREW COMMENTS: REPEAT ENG 4 FIRE LOOP B STATUS MSG. REPLACED R7223 RELAY IAW FIM. PCN 585-1052 PER MM 24-31-03, NO HELP. REPLACED TS682 & TS683 FIRE DETECTION LOOPS ENG 4, NO HELP. "ENG 4 FIRE LP B" STATUS MSG SHOWS ON EICAS. AFTER REPLACEMENT OF WIRING, SYS STILLS FAILS TEST. FOUND UPPER AFT LOOP HAD INTERMITTENT RESISTANCE TO THE CASE OF DETECTOR TS681, REPLACED UPPER AFT LOOP AGAIN, GROUND TEST PASSED, NO EXISTING FAULT. NO STATUS.