Service difficulty report · Carbon Seal · Boeing 777222

Difficulty date
September 21, 2010
Submitted
October 15, 2010
Operation
Air carrier
Aircraft
N780UA
Make and model
Boeing 777222
Aircraft serial
26944
Aircraft time
57,411 hours, 10,425 cycles
Engine
Pwa PW4077
Engine time
51,649 hours, 9,522 cycles
Part
Carbon Seal
Part number
71R158
Condition
Leaking
Location
Nr 2 Eng Gearbox
Stage of operation
IN
How discovered
V
Nature of condition
K
Precautionary procedure
K

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

What was found

NR 2 ENG GEARBOX SEALS HAVE OIL CONSUMPTION HISTORY THAT IS USUALLY NORMAL BUT ON OCCASIONAL FLIGHTS IT USES A GULP OF OIL AS SHOWN BY LOW QTY IN FLT AND LARGE OIL SVC ON ARRIVAL. SUSPECT A GEARBOX CARBON SEAL MAY BE UNSEATING INTERMITTENTLY. IST OPTY PLZ DO MM STATIC PRESSURE LEAK CK PORTION THAT DOES BUBBLE CK FOR LEAKS FROM GEARBOX ACCY DRIVE PAD DRAINS. IF ANY DRAIN LEAK IS UNUSUALLY RAPID, REPLACE THAT CARBON SEAL ASSY. IF NO LEAK ISOLATED, PRECAUTIONARY REPLACE DEOILER DRIVE CARBON SEAL AND CLEAN THE SEAL SEATING SURFACE IAW MM6. BAGGED DRAIN LINES AND ACP'D HIGH PWR RUN. NO LEAKAGE FROM LINES. ACP'D MM FOR GEARBOX PRESS CHECK, NO LEAKS NOTED. REPLACED DEOILER CARBON SEAL.