SDR 2007UALA01648

Service difficulty report · Engine · Boeing 747422

Difficulty date: May 26, 2007
Submitted: June 1, 2007
Operation: Air carrier
Aircraft: N193UA
Make and model: Boeing 747422
Aircraft serial: 26890
Aircraft time: 45,513 hours, 5,522 cycles
Engine: Pwa PW4056
Engine time: 36,213 hours, 4,507 cycles
System (JASC): 7200 · Engine (Turbine/Turboprop)
Part: Engine
Condition: Failed
Location: Nr 4
Stage of operation: CL
How discovered: O
Nature of condition: Y, J
Precautionary procedure: A

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

What was found

RTFL UNDER AMBER ALERT DUE TO NR 4 ENGINE FAILURE. [07-17-07] ENGINE REPLACED AT SFO FOLLOWING 3-ENGINE FERRY. TEARDOWN FOUND A FAILED STAGE-1 HP TURBINE INNER AIRSEAL. MODE CAUSED BY FLUTTER OF THE AIRSEAL. RESULTANT DAMAGE TO THE HP & LP TURBINES WAS SEVERE. ADDITIONALLY, THE HP COMPRESSOR BLADE TIPS WERE HEAVILY WORN DUE TO THE RESULTANT ROTOR UNBALANCE. THE FAILURE MODE IS STILL UNDER INVESTIGATION BY PWA. INSTALLED A NEW BRUSH SEAL, AND RING DAMPER, AT EVERY HP TURBINE RE-BUILD.