What happened
During preparations for a pilot's helicopter commercial checkride, a flight instructor and a student were practicing autorotation procedures. During the second autorotation attempt, the flight instructor observed that the rotor RPM had decreased significantly. The instructor noted that the pilot was pulling up on the collective during this period.
In response to the dropping RPM, the instructor immediately took command of the flight controls and attempted to lower the collective. The helicopter subsequently made a hard landing on the runway, which caused the aircraft to bounce and yaw to the right. After a second bounce, the aircraft came to rest on the right side of the runway. The aircraft sustained substantial damage to the tailboom, and the occupants were not injured.
The investigation
The flight instructor reported that there were no mechanical failures or malfunctions with the helicopter prior to the accident that would have prevented normal operation.