Accident Overview
A helicopter sustained a loss of engine power during flight due to the failure of the No. 3 exhaust valve. The cause of the valve failure could not be determined. Following the power loss, the pilot initiated an autorotation maneuver. However, the pilot did not maintain sufficient rotor rpm and an appropriate rate of descent, resulting in the helicopter colliding with terrain while still airborne.
Pilot Information
The pilot held a helicopter rating and had accumulated a total of 67 flight hours in helicopters, of which 18 hours were as pilot-in-command. The pilot's most recent practice of autorotation maneuvers had occurred four months prior to the accident.
Findings
Examination of the engine revealed that the No. 3 exhaust valve had failed, leading to a loss of power. The reason for the valve failure remains undetermined. The subsequent autorotation was not executed with proper control of rotor rpm and descent rate, leading to the collision with terrain.