What was found
(CAN) ENGINE SENT FOR REPAIR AFTER REDUCTION GEARBOX WAS FOUND MAKING M50 METAL. DISASSEMBLY OF ENGINE REVEALED SOURCE OF THE M50 METAL CONTAMINATION A SPALLED NR 15 BEARING. NR 15 BEARING HAD ELECTRO-EROSION ON THE OUTER RACE AND ROLLERS. NR 15 BEARING BORE WAS FRETTED AND BEARING HAD SPUN ON THE PROP SHAFT. SUBMITTER SUGGESTED CAUSE OF BEARING FAILURE WAS ELECTRO-EROSION WHICH APPEARED TO BE A STRAY ELECTRICAL DISCHARGE FROM SOME ACFT COMPONENT AND NOT A LIGHTNING STRIKE. THERE WAS SECONDARY DAMAGE ON THE BULL GEAR, LT AND RT 2ND STAGE SPUR GEARS, OVERSPEED GOVERNOR SPUR GEAR AND REDUCTION GEARBOX SCAVENGE PUMP HOUSING. PART TC: 19,818.