Service difficulty report · Control Unit · Boeing 747422

Difficulty date
April 5, 2011
Submitted
April 27, 2011
Operation
Air carrier
Aircraft
N171UA
Make and model
Boeing 747422
Aircraft serial
24322
Aircraft time
81,212 hours, 9,698 cycles
Engine
Pwa PW4056
Part
Control Unit
Condition
Faulted
Location
Fuel System
Stage of operation
CR
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

FUEL IMBALANCE BETWEEN NR 2 AND NR 3 TANKS. CONFIRMED UNWANTED FUEL TRANSFER TO NR 3 MAIN TANK. WITH CENTER PUMPS ON TRANSFER RATE 1000LB IN 10 MIN. WILL REQUIRE TANK ENTRY FOR INSP OF NR 3 MAIN TANK PLUMBING. FOUND NR 2 MAIN JETTINSON TRX VLV INOP AND NR 3 MAIN FUEL VALVE LEAKING FUEL. REPLACED NR 2 MAIN JETTISON VLV PER MM. NEEDS OPS CHECK PER MM. REPLACED NR 3 MAIN OTBD REFUEL VALVE CONTROL UNIT, OPS AND LEAK CHECKED GOOD.