What was found
DURING ROUTINE OIL CHANGE, FND METAL PIECES OF BALL BEARING CAGE IN SUCTION SCREEN. REMOVAL OF LT MAG REVEALED ALMOST TOTAL FAILURE OF LT MAG DRIVE BRG & ITS SLEEVE IN CRANKCASE. SLEEVE HAD BEEN INSTALLED IAW LYC SI NR 1140 DURING ENG O\H. THIS IS 5TH FINDING OF THIS NATURE IN FLEET OF 6 AIRPLANES IN 12 MONTHS. PREV FINDINGS COINCIDED WITH C/W AD 78-09-7R3, BENDIX MAG IMPULSE COUPLING INSP. THIS LAST ENG DID NOT REQUIRE AD INSP DUE TO SLICK MAG INSTALL. SUBMITTER STATED FAILURE LEFT UNDETECTED COULD CAUSE TOTAL ENG FAILURE. UNNECESSARY C/W SI NR 1140, WHEN NOT NEEDED, IMPROPER FAB & FITTING OF SLEEVE IN CRANKCASE BY O/H MIGHT CAUSE FAILURES. ENG RETURNED TO O/H FOR REPAIRS. ENG TSOH 462.0 HRS.