Accident
The pilot had completed a spraying operation and was proceeding to the Glendive Airport when the engine or propeller began a sudden severe vibration, necessitating an engine shutdown. An emergency landing was performed. During the landing, the left wing struck a hill, causing the aircraft to spin to the left. Subsequently, the right main landing gear, tailwheel, and both the upper and lower right wings failed. A post-impact fire consumed the aircraft.
Examination
A post-accident examination uncovered that the outer 13 inches of one propeller blade, part number 6101A-13, had failed. Additionally, the engine mounting structure and several mounts were found broken. Maintenance records indicated that the Hamilton Standard propeller hub (model 2-D-30-237) had been overhauled in 1977, during which twisted blades were straightened. The total time on the propeller since that overhaul was 1,168 hours.