Primary finding
Probable cause
The pilot receiving instruction’s rapid reduction in throttle during hover autorotation training which resulted in a loss of control and collision with the ground.
Investigator assessment
Analysis narrative
The flight instructor reported that, while conducting hover autorotation training from about one foot above the ground, the pilot receiving instruction quickly closed the throttle. The helicopter subsequently descended rapidly, caught the left skid on the pavement and rolled over to the left. The helicopter sustained substantial damage to the tail boom and main rotor blades. The flight instructor reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.