Schweizer 269C N432MS accident near Buffalo, Wyoming

Probable cause

The pilot's attempted downwind takeoff that resulted in an aborted takeoff. Contributing to the accident was the unsuitable terrain.

NTSB analysis

The helicopter pilot was picking up a biologist who was conducting land surveys. Prior to landing he circled the landing zone to observe the wind conditions. During the landing approach he transitioned out of effective translational lift earlier than expected, and attributed this to a reduced headwind caused by the enclosed terrain. During departure and acceleration to effective translational lift speed, the rotor speed began to decay. The ground speed was faster than he anticipated so he lowered the collective, and added forward cyclic, but could not maintain enough rotor speed for sustained flight. The pilot elected to land the helicopter ahead on a 30-degree uphill slope. After landing, the helicopter rolled back and the tail rotor made contact with the ground causing substantial damage to the tail rotor drive system. After the accident the pilot noted that the winds had shifted 180 degrees from his initial pre-accident observation.

Text from the NTSB. Open the NTSB docket for LAX08LA196 for the full record.