Incident Overview
While conducting an aerial application flight, the pilot noted a change in engine sound accompanied by a slight loss of power. During the turn to return to the airstrip for a precautionary landing, the engine experienced a complete loss of power. The pilot executed a forced landing onto soft terrain. During the landing roll, the wheels sank into the soft ground, causing the aircraft to flip inverted.
Investigation Findings
Post-incident investigation revealed that the exhaust valve rocker shaft on cylinder #5, along with both retaining nuts (which were required to be secured with safety wire), were missing. The absence of these components was documented as a significant finding.
Conclusions
The incident resulted from an engine failure that led to a forced landing. The investigation identified the missing rocker shaft and retaining nuts, but no causal determination was provided in the source material.