Incident Summary
A helicopter on a short test flight experienced a sudden loss of engine power accompanied by a large yaw at an altitude of 500 feet above ground level. The pilot initiated an autorotation but was forced to maneuver to clear ground obstacles. This resulted in a reduction of main rotor rpm, and the helicopter subsequently fell vertically from approximately 50 feet, leading to a hard landing. No fire occurred.
Aircraft and Pilot Information
The helicopter had recently undergone maintenance; a cylinder had been replaced, and the owner asked a pilot to conduct the test flight after the cylinder's "brake-in" process was completed. The pilot held a private pilot certificate and had logged a total of 1,200 flight hours, including 80 hours in rotorcraft, of which 40 hours were in the same make and model helicopter. Weather conditions were not considered a factor in the event.
Damage and Recovery
All three main rotor blades were destroyed, and the tail boom separated from the airframe. Prior to recovery, approximately ten gallons of aviation fuel were drained from the helicopter. An examination of the airframe and engine revealed no discrepancies that could have contributed to the reported loss of engine power. The reason for the loss of engine power could not be determined.