The pilot reported that while in cruise flight, the engine rpm of the Rotorway Executive 162F helicopter suddenly increased to the point wher the rev limiter activated.

At this point the helicopter was about 700 feet above ground level and the pilot performed an autorotation to a baseball field in Plymouth, Indiana.

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.

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.

NTSB Identification: CEN15CA155

This February 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.