As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ALCOR ALTERNATOR INSTALLATION, FIA/W STC SA334SW, MOUNTING BOLT BROKE AT THREADED AREA. BOLT APPEARS TO BE TOO SHORT FOR APPLICATION, LOAD BEARING IS ON PORTION OF THREADED AREA RATHER THAN BOLT GRIP. SUGGEST STC BE AMENDED TO CALL OUT LONGER BOLT. FAILURE CAUSED TOTAL ACFT ELECTRICAL FAILURE.