SDR 2008UALA02126

Service difficulty report · Carbon Seal · Boeing 747422

Difficulty date: April 14, 2008
Submitted: April 16, 2008
Operation: Air carrier
Aircraft: N199UA
Make and model: Boeing 747422
Aircraft serial: 28717
Aircraft time: 43,278 hours, 5,210 cycles
Engine: Pwa PW4056
Engine time: 65,234 hours, 7,894 cycles
System (JASC): 7261 · Turbine Engine Oil System
Part: Carbon Seal
Condition: Leaking
Location: Nr 4 Engine
Stage of operation: CR
How discovered: O
Nature of condition: K, J
Precautionary procedure: E, A

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

What was found

FLIGHT DIVERTED UNDER AMBER ALERT WITH NR 4 ENGINE SHUT DOWN DUE TO LOSS OF OIL QUANTITY. REPLACED ENGINE. SHOP TEARDOWN SHOWED OIL COKE ON THE DRY SIDE OF THE NR 1 AND 2 CARBON SEAL ASSEMBLIES. THIS SUGGESTS THAT OIL WAS LEAKING PAST THESE SEALS DURING ENGINE OPERATION. HOWEVER, THERE WAS NO NOTABLE DAMAGE TO THESE SEALS. NO OTHER DISCREPANCIES WERE NOTED. POOR BREATHER PRESSURE AND/OR SCAVENGING IS SUSPECTED, BUT COULD NOT BE PROVED. ALL OIL SYSTEM COMPONENTS WERE REPLACED.