Incident Overview
A helicopter conducting a seismic data acquisition operation was involved in an accident while attempting to land by a road in mountainous terrain at an elevation of approximately 8,400 feet.
Sequence of Events
According to witness accounts, the helicopter approached and hovered over the roadway. The rotor downwash generated a considerable amount of dust, causing ground personnel to cover their eyes and look away. The helicopter then pulled up and moved away from the ground personnel, traveling up the hillside beside the road. It turned right to face the hillside.
Ground personnel reported that the helicopter then made an unusual noise, spun around, began to whip back and forth, and descended into trees in an uncontrolled manner. After impact, the helicopter rolled down the hillside and came to rest on the road.
Injuries and Damage
The pilot was injured and could not remember the occurrence. The extent of damage to the helicopter was not specified in the report.
Investigation Findings
Ground personnel suspected that the engine lost power, but a post-impact examination found no preimpact failure. Several circuit breakers were found in the "out" position, but two of them (boost pump) would normally have been pulled after landing.
Weather conditions at the time included wind from the south at 10 knots. A witness stated that a gust blew dust back toward the aircraft while it was hovering.
Conclusion
The investigation did not determine a specific cause for the accident.