Incident Overview
The pilot was maneuvering the helicopter near friends at an altitude of approximately 600 feet above ground level. After completing several turns while departing the area, the pilot observed that the clutch light was illuminated. About five seconds later, he pulled the clutch circuit breaker. Simultaneously, the engine's revolutions per minute (rpm) increased sharply, and the main rotor rpm alarm activated.
Pilot Actions
In response, the pilot immediately lowered the collective and rolled on the throttle in an attempt to increase rotor rpm. When these actions failed to restore normal rotor speed, he initiated an autorotation to descend to the ground. During the descent, the pilot was unable to bring the rotor rpm back into the normal operating range.
Impact and Damage
The helicopter landed hard. The impact caused the skids to spread, and one main rotor blade struck the tail boom.
Postaccident Examination
An examination of the helicopter's drive system revealed that the V-drive belts had rolled off their respective sheaves. The reason for the belt displacement could not be determined.