Accident Description
During the landing rollout on a gravel airstrip, the pilot engaged the propellers in reverse. Shortly thereafter, the airplane began to veer to the left. In response, the pilot applied the right brake and increased reverse thrust on the right engine. Despite these actions, the pilot was unable to regain directional control, and the airplane departed the left side of the airstrip. It then encountered brush and rough terrain before coming to rest.
Propeller Control Unit Examination
Following the accident, the engines were examined. Inspection of the right engine propeller control unit revealed that a pin, on which the propeller control cam slides, had separated. The cockpit propeller control operates the control cam directly. Examination of the fracture surface of the pin disclosed that the pin failed in overload.