As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ALTERNATOR WENT OFF LINE. UPON REMOVAL OF THE ALTERNATOR WAS NOTICED THAT THE SPLINE GEAR WAS SHEARED. THE DRIVE SHAFT WAS ALSO SHEARED IN THE THREADED PORTION, JUST BELOW THE CASTLE NUT. THE CASTLE NUT WAS STILL INTACT ON THE TIP OF THE THREADED SHAFT WITH THE COTTER PIN INTACT. THIS PARTICULAR UNIT HAS BEEN SENT TO DND TEST FACILITIES TO DETERMINE THE EXACT CAUSE OF FAILURE.