Accident Sequence
During a practice 180-degree autorotation with a power recovery, a commercial/student pilot was flying a helicopter when an excessive rate of descent developed. The flight instructor, who had joined the student on the controls, initiated a progressive rollout of the turn while applying aft cyclic, raising the collective, and adding power for a recovery to level flight. The instructor reported that the engine did not respond to the throttle input.
Due to the rate of descent, the instructor decided not to attempt an aggressive flare, fearing a tail rotor ground strike. Instead, he continued with aft cyclic input and collective manipulation to reduce forward airspeed and rate of descent for a run-on landing. The helicopter contacted the ground in a near-skids-level attitude at approximately 30 knots, with rotor rpm in the high end of the green region. The helicopter became airborne approximately 8 to 10 feet above the ground.
The instructor indicated that the throttle was still unresponsive. He raised the collective to cushion the second impact, and the low rotor rpm warning light and horn activated prior to touchdown. The helicopter impacted the ground again at approximately 20 knots, collapsing the left skid. The helicopter then rolled to the left and came to rest on its left side, facing approximately 180 degrees from the approach heading.
Post-Accident Examination
A post-accident examination of the helicopter revealed no anomalies, with the exception of a failed left seat restraining system. An engine test run was conducted and no anomalies were noted that would have affected its operation.