What was found
PILOT REPORTED ON APPROACH TO LANDING, A MOMENTARY RIGHT ENGINE POWER FLUCTUATION, FOLLOWED BY RIGHT ALTERNATOR FAILURE, LANDED WITHOUT INCIDENT. POST FLIGHT MAINTENANCE FOUND ALTERNATOR DRIVE SHAFT SHEARED NEAR ALTERNATOR STATOR. THE ALTERNATOR DRIVE COUPLER LOCATED INSIDE THE CASE ALONG WITH SHEARED ALTERNATOR TO CRANKSHAFT DRIVE GEAR. THE ALTERNATOR DRIVE COUPLER RETAINING NUT AND WASHER NOT LOCATED. DAMAGE OBSERVED TO CRANKCASE, DRIVE GEARS ETC. METAL CONTAMINATION FOUND THROUGHOUT THE FORWARD AREA OF CRANKCASE.