Primary finding
Probable cause
The certified flight instructor's failure to maintain adequate main rotor RPM during the autorotation.
Investigator assessment
Analysis narrative
The certified flight instructor reported that the purpose of the flight was to demonstrate a variety of maneuvers to the student in the helicopter. Near the end of the flight the instructor demonstrated a power-on autorotation; however, he delayed the application of power and did not have sufficient rotor RPM to recover the helicopter before impacting the ground. Upon ground impact, the helicopter's tail rotor drive shaft and main rotor blades were damaged. The pilot reported no preimpact mechanical malfunctions of failures with the airframe or the engine that would have precluded normal operation.
Source record
Factual narrative
The certified flight instructor reported that he took off in the helicopter to show a student pilot a demonstration of various maneuvers. Near the end of the flight the instructor demonstrated a power on autorotation but he was late rolling on the throttle and did not have sufficient rotor RPM to recover the helicopter before impacting the ground. Upon ground impact the helicopter's tail rotor drive shaft and main rotor blades were damaged. The pilot reported no pre-impact mechanical malfunctions of failures with the airframe or the engine that would have precluded normal operation.