What happened
The aircraft was operating en route to a designated field when an unexpected loss of engine power occurred at an altitude of approximately 500 feet above ground level. The pilot initiated a forced landing procedure but did not jettison the load of chemicals carried on board. The aircraft touched down on wet grass but lacked sufficient stopping distance to avoid striking a dirt embankment, resulting in a collision.
The investigation
Post-accident examination of the engine revealed significant mechanical failures. The crankshaft was found broken between the number 3 main journal and the number 3 connecting rod journal. Investigation of the fracture surface indicated the presence of fatigue-related markings. Additionally, the number 3 main bearings were worn and had been rotating on the crankshaft, suggesting a lack of proper fit or lubrication.
Findings
The engine had accumulated 2,160 total operating hours, with 877 hours since its last overhaul. The owners reported no history of propeller ground strikes that could have contributed to the failure. The combination of worn bearings and fatigue cracking in the crankshaft points to mechanical deterioration as the primary factor in the power loss.