Primary finding
Probable cause
The pilot’s improper recovery from a practice autorotation, which resulted in a hard landing. Contributing to the accident was the flight instructor’s inadequate supervision of the pilot receiving instruction.
Investigator assessment
Analysis narrative
The pilot and flight instructor were conducting training exercises in a helicopter at night using night vision goggles. The exercises included four autorotation landings from a hover, each initiated about 4 ft above ground level. The pilot reported that during the second autorotation landing, following the flight instructor’s reduction of power, he reacted prematurely and inadvertently increased the helicopter’s height above the ground, which resulted in a hard landing. Unaware that the helicopter had been damaged, the remainder of the training flight was completed uneventfully. The following day, during a preflight inspection, another flight crew discovered substantial damage to the tail boom. The pilot and the flight instructor reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.