Incident Overview
During cruise, the pilot reported that the engine abruptly lost all power. The aircraft subsequently collided with trees during a forced landing at night, causing both wings to be torn off.
Engine Examination
An examination of the engine revealed that the crankshaft gear bolt was loose and that the gear alignment dowel was sheared. This condition resulted in a loss of engine gear train continuity. A metallurgical examination determined that the dowel pin had failed due to fatigue.
Maintenance History
According to the operator's mechanic, the engine had experienced a sudden stoppage due to a propeller strike approximately 151 operating hours before the accident. Lycoming Service Bulletin #465 outlines mandatory inspection, modification, and assembly procedures for the crank gear, to be complied with during overhaul, after a propeller strike, or whenever gear train repair is required. The mechanic reported that the bulletin was not complied with after the propeller strike.