What happened
The incident occurred while the aircraft was conducting an agricultural application flight, specifically a swath run. During this phase of operation, the engine began to lose power unexpectedly. The pilot responded by pulling up to gain altitude and searching for a suitable landing area. To reduce weight and improve glide performance, the pilot dumped the chemical load carried in the tank.
Despite these efforts, engine RPM continued to decrease, indicating a severe mechanical failure. With no other options available, the pilot elected to land in a field that was currently being summer fallowed. During the landing rollout, the aircraft nosed over, resulting in damage to the airframe and engine components.
The investigation
A post-accident examination of the aircraft revealed significant mechanical issues within the engine assembly. Inspectors found that the number four exhaust valve had become frozen shut, preventing proper operation. Additionally, the push rod associated with this valve was found to be bent, likely due to the stress caused by the valve's failure to move freely.