What happened
While returning to the airport, the pilot experienced an unexpected engine failure. According to the pilot, an abnormal vibration was first noticed after pulling out of a field. The pilot attempted to mitigate the issue by reducing the throttle by 100 rpm, which briefly appeared to stabilize the engine. However, approximately one-half mile later, the engine began to shake violently and subsequently quit. The aircraft subsequently landed in a wheat field.
The investigation
The aircraft was equipped with a Continental 6-285 "Tiara" geared engine. During the post-accident examination of the engine, investigators discovered that the prop driver gear shaft was protruding approximately one inch further out of the front of the engine than normal. Additionally, the engine could not be rotated by hand. No other anomalies were found in the airframe or the engine that could be linked to a pre-existing condition.