Accident Details
While hovering over a mountainous area during an aerial observation mission, a helicopter entered a rapid yaw rotation to the left and subsequently descended to ground impact. The pilot was at an altitude of 200 feet above ground level when initiating a left turn. The helicopter turned more rapidly than normal, and the pilot applied right pedal input. The right pedal did not counteract the turn rate, and the helicopter continued spinning left. The pilot then reduced power and pitched the nose forward while maintaining right pedal, but the helicopter continued to rotate as it descended.
Pilot and Operational Context
The pilot was not aware of the wind direction at the time of the accident. Their regular flying assignment consisted of high-altitude surveillance flights over Florida, and they were on a short-duration pilot augmentation assignment to the Tucson operations base. The pilot had limited mountain flying experience. A pilot flying in the area immediately after the accident reported winds greater than 20 knots from the west.
Aircraft and Environmental Conditions
The helicopter was operating at a gross weight of 4,020 pounds. The maximum allowable gross weight for the helicopter is 4,961 pounds. The density altitude was 7,850 feet mean sea level (msl), and the out-of-ground-effect hover capability of the helicopter was about 8,000 feet msl.
Post-Accident Examination
A post-accident examination of the helicopter did not reveal any preimpact airframe or engine malfunctions.