Primary finding
Probable cause
The pilot's failure to maintain rotor speed during the autorotation, which resulted in an excessive sink rate and a hard landing.
Investigator assessment
Analysis narrative
The pilot reported that shortly after liftoff he noticed a “disturbing vibration” in the helicopter. He elected to initiate an autorotation to an open agricultural field. The pilot stated that he executed a 180-degree turn in order to avoid a tree line. He noted that the rotor speed got too low and he was unable to reduce the sink rate, which resulted in a hard landing. The main rotor contacted and separated the tail boom and the right landing skid collapsed during the accident sequence. The pilot noted that additional practice in autorotation descents and landings might have prevented the accident.
Source record
Factual narrative
The pilot reported that shortly after liftoff he noticed a “disturbing vibration” in the helicopter. He initiated an autorotation to an open agricultural field. The pilot stated that he executed a 180-degree turn in order to avoid a tree line. He noted that the rotor speed got too low and he was unable to reduce the sink rate, which resulted in a hard landing. The main rotor contacted and separated the tail boom, and the right landing skid collapsed during the accident sequence. The pilot noted that additional practice in autorotation descents and landings might have prevented the accident.