NTSB Identification: LAX99LA300.
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Accident occurred Thursday, September 09, 1999 in PIUTE, NV
Probable Cause Approval Date: 08/13/2001
Aircraft: Robinson R-22-BETA, registration: N4076Z
Injuries: 2 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

Two flight instructors were practicing autorotations. The last planned autorotation began at 600 feet above ground level (agl) and 70 knots. Turning into the landing area, the pilot was maintaining rotor rpm in the green arc and the airspeed at 60 knots. As he was about to roll onto final, he heard the low rotor rpm horn and saw the rpm drop to 85 percent. As he lowered the collective, he noted he was still descending rapidly and he did not see the rpm increase substantially. He attempted a power recovery and the other pilot tried to help roll on the throttle and lower the collective. At 100 feet with full throttle and the collective lowered, the pilot recognized he would touch down and attempted to flare and lower the descent rate. The rpm remained below 80 percent and the airspeed slowed to 40 knots. He raised the collective to cushion the landing and touched down an estimated 200 feet from his intended landing spot. The helicopter landed hard and rolled over onto its right side.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the failure of the pilot to maintain rotor rpm while practicing autorotations, resulting in a hard landing and roll over.

Full narrative available

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