What was found
LOSS OF OIL PRESSURE IN NR 2 ENGINE AND ENGINE VIBRATION. MAINTENANCE FOUND METAL ON THE MASTER & NR 4 BEARING CHIP DETECTORS, & METAL IN THE TAILPIPE. THE ENGINE WAS REPLACED IN SEA. TEARDOWN REVEALED THE THRUST BALANCE CAVITY ROTATING OUTER SEAL CAUGHT FIRE & BURNED AWAY. SUBSEQUENT HEAT DISTRESS LIBERATED LARGE CHUNKS OF BOTH THE STATIC & ROTATING THRUST BALANCE CAVITY OUTER SEALS. SLIGHTLY OVER 7 LBS. OF MATERIAL CENTRIFUGED OUTWARD INTO ROTOR, CREATING APPROX 2100 OZ-IN OF UNBALANCE & THE RESULTANT HIGH VIBRATION. RESULTANT DAMAGE TO NR 4 BEARING, & ITS CARBON SEALS ACCOUNTED FOR OIL LOSS. ROOT CAUSE FOR FIRE IS UNDER PWA INVESTIGATION & WILL TAKE SEVERAL MONTHS.