Accident Description
During a practice 180-degree autorotation landing, the helicopter touched down hard. The main rotor struck the tail boom, severing it, and the helicopter subsequently rolled onto its side.
Pilot Statements
The first pilot reported that during four of six prior autorotations performed by the second pilot, it was necessary for the first pilot to assume control and make power recoveries due to high landing flares, improper airspeed, and improper rotor rpm. During the seventh autorotation—the one that resulted in the accident—the first pilot stated that the second pilot first let the main rotor rpm get too high, then too low, and then let airspeed get low. The first pilot again took control and applied engine power, but this time, as the ground approached more rapidly than before due to recovery from a low airspeed and low rpm condition, the second pilot "began to scream" and interfered with the first pilot's control by pulling up on the collective. The first pilot could not overpower him, the rotor rpm decayed further, and a hard landing resulted. The first pilot reported there were no mechanical problems with the helicopter.
The second pilot reported that, as he initiated the final autorotation, the first pilot said "hold on, hold on," and the second pilot thought he was again taking the controls and relinquished them to him. As the helicopter continued the descent, the first pilot continued to say "hold on, hold on," and the second pilot became worried because the ground approached rapidly and the low rpm horn had been on for several seconds. When the second pilot realized they were going to crash and the first pilot wasn't doing anything to arrest the situation, he (the second pilot) took the controls and tried to flare and pulled full up collective to cushion the landing.
Previous Autorotation Issues
The first pilot noted that in prior autorotations by the second pilot, intervention was frequently required to correct high flares, improper airspeed, and rotor rpm deviations. This pattern preceded the accident autorotation.