Bell 206B N86TA accident near Palmer, Alaska

Probable cause

The pilot's failure to maintain control while hovering at a low altitude, which resulted in an impact with frozen lake ice. Contributing to the accident was the pilot's decision to operate the helicopter from the left seat contrary to the rotorcraft flight manual, and the decision to continue the flight after the initial impact.

NTSB analysis

The solo helicopter pilot was flying a turbine-powered helicopter, equipped with dual controls, while seated in the left seat.

A limitation in the rotorcraft flight manual states, in part: "the minimum flight crew consists of one pilot who shall operate the helicopter from the right crew seat."

The N2 governor linear actuator control switch is located on the collective control for the right crew seat only. The pilot reported that flying the helicopter from the left seat and in order to manipulate this control switch, he had to take his left hand off the collective control for the left crew seat, and place it on the left crew seat cyclic control, then take his right hand off the left crew seat cyclic control and place it on the collective control for the right crew seat.

The pilot said that while in a 6-foot hover above a frozen lake, he became distracted while adjusting the N2 (rotor) rpm using the linear actuator control switch, and the helicopter became unstable and it began to rapidly descend. He attempted to recover from the unstable condition, but the helicopter's skids struck the ice. After the impact, he was able to recover and regain a stable hover above the ice. Believing that just the helicopter's skids were damaged during the impact, the pilot elected to return to his departure airport, about 19 miles away, where emergency services would be available.

During the return flight, as the helicopter climbed to about 50 feet above the ground, all engine power was lost. The pilot entered an emergency autorotation and selected an area of snow-cover as an emergency landing site.

The pilot's postaccident inspection of the helicopter revealed that during the initial impact on the frozen lake, the aft landing gear cross-tube assembly had been crushed into the aft portion of the fuselage, which subsequently ruptured the fuel cell, resulting in the loss of all fuel onboard.

The pilot stated there were no preaccident mechanical malfunctions or anomalies that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for ANC15CA012 for the full record.