Introduction
An instructor and student pilot conducted autorotation training in a helicopter. The student entered a well-maintained 70-knot glide prior to performing the autorotation recovery. The maneuver did not proceed as expected, leading to a hard landing that caused substantial damage to the aircraft.
Sequence of Events
According to the instructor, the student flared too high, approximately 10 to 12 feet above ground level (agl), and kept the throttle closed. This prevented the governor from restoring the rotor rpm needed to recover from the maneuver. The lack of sufficient lift and low altitude did not allow the student to slow the descent. The helicopter landed hard, resulting in damage to the skids and tailboom.
The student pilot stated that everything at the time of the flare was normal. However, the instructor took control of the aircraft and felt the student trying to roll the throttle on, but for some reason, the student was unable to release the throttle. The helicopter then landed hard from about 5 to 6 feet agl.
Damage
The hard landing inflicted substantial damage to the helicopter's skids and tailboom. No other damage was reported.
Investigation
No probable cause has been determined based on the available information. The investigation includes statements from the instructor and student pilot but does not specify contributing factors or causal links.