What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Powerplant failed in flight. When recovered, found bendix ignition housing assembly had separated from the accessory case, causing immediate, total power loss. This ignition system consists of dual magnetos housed together that are served by a common drive from the accessory case. The entire assembly is attached by retaining nuts (upper/lower) tightened against the respective clips or "ears" to threaded studs protruding from the accessory case.
The lower stud threads were clean and undamaged with no retaining nut found, while the upper stud and retaining clip/ear was broken and damaged- indicating that the lower nut was not installed, or loosened and fell off previously, resulting in increased stress upon, and ultimate failure of the upper retaining "ear".
As the FAA filed it
POWERPLANT FAILED IN FLIGHT. WHEN RECOVERED, FOUND BENDIX IGNITION HOUSING ASSEMBLY HAD SEPARATED FROM THE ACCESSORY CASE, CAUSING IMMEDIATE, TOTAL POWER LOSS. THIS IGNITION SYSTEM CONSISTS OF DUAL MAGNETOS HOUSED TOGETHER THAT ARE SERVED BY A COMMON DRIVE FROM THE ACCESSORY CASE. THE ENTIRE ASSEMBLY IS ATTACHED BY RETAINING NUTS (UPPER/LOWER) TIGHTENED AGAINST THE RESPECTIVE CLIPS OR "EARS" TO THREADED STUDS PROTRUDING FROM THE ACCESSORY CASE.
THE LOWER STUD THREADS WERE CLEAN AND UNDAMAGED WITH NO RETAINING NUT FOUND, WHILE THE UPPER STUD AND RETAINING CLIP/EAR WAS BROKEN AND DAMAGED- INDICATING THAT THE LOWER NUT WAS NOT INSTALLED, OR LOOSENED AND FELL OFF PREVIOUSLY, RESULTING IN INCREASED STRESS UPON, AND ULTIMATE FAILURE OF THE UPPER RETAINING "EAR".
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.