What happened
During a cross-country flight, the aircraft's engine failed abruptly without prior warning. The pilot initiated an emergency procedure to execute a forced landing. An initial plan was made to land on a nearby road; however, a vehicle was spotted in the approach path. To avoid a collision with the vehicle, the pilot altered the trajectory and veered off the roadway into an adjacent field. Upon impact, the aircraft's nose gear collapsed.
The investigation
Post-accident examination of the engine revealed that the crankshaft had fractured at the number 4 bearing journal cheek. Metallurgical analysis showed that the shaft contained several gouges extending through approximately 90 degrees of its circumference. The fatigue initiation site was identified within one of these surface imperfections. Maintenance records indicated numerous cylinder changes throughout the engine's service life, but there were no logbook entries documenting a previous sudden stoppage of the engine.
Findings
The mechanical failure was driven by fatigue originating from surface gouges on the crankshaft. The pilot's decision to avoid the vehicle resulted in the nose gear collapse during the forced landing. No evidence suggested a prior catastrophic event that would have alerted maintenance personnel to the developing defect.