What was found
WHILE ON THE GROUND TAXIING IN, THE FLIGHT CREW RECEIVED A LT ENGINE OIL CHIP CAS MESSAGE. A LOCAL MAINTENANCE VENDOR WAS CONTACTED TO PERFORM A CHIP DETECTOR INSPECTION AND ENGINE OIL SOAP SAMPLE, ALONG WITH ENGINE DATA DOWNLOADS. ALL CHIP DETECTORS WERE FOUND TO HAVE SUBSTANTIAL METAL DEBRIS, AND THE OIL SOAP LAB RESULT CAME BACK AS EXCESSIVE CARBON. AN ENGINE MAINTENANCE VENDOR PERFORMED THE ON WING ENGINE TEAR DOWN AND INSPECTION. IT WAS DETERMINED FROM THE INSPECTION FINDINGS THAT THE NR 4 BEARING CARBON SEAL HAD FAILED WHICH RESULTED IN CARBON SEAL AND METAL FRAGMENTS OBSERVED IN THE STUB SHAFT, NR 4 AND NR 5 BEARING REGION. THERE WAS NO FAILURE OF THE NR 4 AND NR 5 BEARINGS, BOTH WERE INTACT. THE ENGINE WILL BE REPAIRED ON WING.