Primary finding
Probable cause
The flight instructor’s failure to maintain sufficient rotor speed during a practice autorotation which resulted in a hard landing.
Investigator assessment
Analysis narrative
The student pilot and flight instructor initiated a 90° practice autorotation. As the helicopter descended, the flight instructor took control of the helicopter to cushion the landing after the student pilot flared too high. During the attempted recovery, sufficient rotor speed was not maintained, and the helicopter experienced a hard landing. The helicopter sustained substantial damage to the tailboom. Both the student pilot and the flight instructor reported that there were no preaccident mechanical malfunctions or failures that would have precluded normal operations.