Airbus AS-350 N504WD accident near Hamilton, Montana

Probable cause

The pilot's excessive collective application during an autorotation. Contributing to the accident was the flight instructor's inadequate supervision of the training flight.

NTSB analysis

The flight instructor, in the left seat reported that he was providing flight instruction to the commercial pilot, in the right seat, which included a series of hovering autorotations. According to the instructor, as the commercial pilot hovered the helicopter about 3 or 4 ft above the ground, the instructor initiated the hovering autorotation by reducing the floor-mounted throttle (fuel flow control lever) to about 70% N1, and the helicopter descended to about 1 ft above the ground. As the commercial pilot tried to cushion the touchdown, he inadvertently applied too much collective pitch, and the helicopter ballooned to a higher altitude. During the second descent, the main rotor rpm continued to decay, and the helicopter’s skids struck the ground. The instructor did not take control of the helicopter during this sequence. A postflight inspection revealed substantial damage to the tailboom.

Text from the NTSB. Open the NTSB docket for ANC15LA076 for the full record.