Primary finding
Probable cause
The pilot’s failure to maintain rotor rpm during a practice autorotation, which resulted in ground contact and a dynamic rollover.
Investigator assessment
Analysis narrative
The helicopter pilot reported that he entered a practice autorotation and intended to terminate the maneuver to a hover. During the flare phase of the maneuver, he allowed the rotor rpm to decay. He increased collective and subsequently added power with throttle. The nose of the helicopter yawed to the right and simultaneously the fuselage rolled to the left. He applied left pedal, but the left skid struck rising terrain and the helicopter entered dynamic rollover. The helicopter sustained substantial damage to the main rotor drive system and the tail rotor drive system. The pilot reported that there were no mechanical malfunctions or failures with the helicopter that would have precluded normal operation.
Source record
Factual narrative
The helicopter pilot reported that he entered a practice autorotation and intended to terminate the maneuver to a hover. During the flare phase of the maneuver, he allowed the rotor RPM to decay. He increased collective and subsequently added power with throttle. The nose of the helicopter yawed to the right and simultaneously the fuselage rolled to the left. He applied left pedal, but the left skid struck rising terrain and the helicopter entered dynamic rollover. The helicopter sustained substantial damage to the main rotor drive system and the tail rotor drive system. The pilot reported that there were no mechanical malfunctions or failures with the helicopter that would have precluded normal operation.