What was found
OWNER OF THIS AIRCRAFT EXPERIENCED FWD ENGINE ALTERNATOR FAILURE (AS INDICATOR BY FAILURE LIGHT) DURING FLIGHT. TECHNICIAN AND OWNER REMOVED ALTERNATOR FROM ENGINE AND DISCOVERED THE DRIVE SHAFT SHEARED. THE GEAR RETAINING BOLT HAD RUBBED INTERNALLY AND BUSTED A PIECE OF THE COTTER PIN OFF, WHICH WAS FOUND ON THE MAGNETIC OIL DRAIN PLUG. THE DRIVE GEAR ALSO DISPLAYED SIGNS OF WEAR. THE ALTERNATOR SHAFT FAILURE APPEARS TO BE A MATERIAL DEFECT.