What happened
The airplane encountered a total loss of engine power while in flight. Unable to maintain altitude or reach a suitable runway, the pilot executed a forced landing in a soft, furrowed field. Upon impact, the aircraft nosed over. No other anomalies were found with respect to the airframe, engine or systems that could be identified as existing prior to impact.
The investigation
Post-acc examination of the engine revealed that a rocker arm shaft for one of the exhaust valves had split. This mechanical failure was determined to be the primary cause of the power loss. No other anomalies were found with respect to the airframe, engine or systems that could be identified as existing prior to impact.
Findings
The investigation concluded that the split rocker arm shaft led directly to the total loss of engine power. The pilot was unable to restart the engine and was forced to land in a field. The aircraft nosed over during the landing. No other anomalies were found with respect to the airframe, engine or systems that could be identified as existing prior to impact.