What happened
While returning from spraying operations, an agricultural airplane experienced a gear collapse during a forced landing. The aircraft impacted the terrain and came to rest in a soft farm field consisting of wheat stubble. The pilot sustained 1 fatal injury.
The investigation
Investigators examined the wreckage and found that the seat belt cable and shoulder harness cable had separated. The separation points showed evidence of tensile overload. It was noted that the pilot was not wearing a helmet, and the manual control for the shoulder harness inertia reel was in the unlocked position.
An examination of the engine revealed that the number four cylinder was compromised. A portion of the piston pin was protruding through a hole in the cylinder wall. Further inspection of the number four piston and intake valve determined that the intake valve failed due to overstress. Additionally, portions of the piston skirt had fractured and separated from the piston. The fracture surfaces on the piston skirt showed severe mechanical damage, with one side exhibiting damage consistent with the piston rotating about the piston pin and the connecting rod impacting the skirt. No other anomalies related to preexisting conditions were identified.