Primary finding
Probable cause
The failure of the helicopter's main drive belt resulting in the pilot performing a forced landing, during which the helicopter's fuselage was substantially damage.
Investigator assessment
Analysis narrative
The pilot reported that while in cruise flight the engine RPM of the helicopter suddenly increased to the point where the rev limiter activated. At this point the helicopter was about 700 ft above ground level and the pilot performed an autorotation to a baseball field. During the forced landing, the helicopter sustained substantial damage to its fuselage. Subsequent examination of the helicopter revealed that the main drive belt that transmitted engine power to the rotor system had failed.
Source record
Factual narrative
The pilot reported that while in cruise flight the engine RPM of the helicopter suddenly increased to the point where the rev limiter activated. At this point the helicopter was about 700 ft above ground level and the pilot performed an autorotation to a baseball field. During the forced landing, the helicopter sustained substantial damage to its fuselage. Subsequent examination of the helicopter revealed that the main drive belt that transmitted engine power to the rotor system had failed.