NTSB Identification: DEN05LA131.
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Accident occurred Friday, September 02, 2005 in Duchesne, UT
Probable Cause Approval Date: 07/31/2006
Aircraft: Aerospatiale SA315B, registration: N220SH
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

During a helicopter external load operation, the pilot was attempting to lift a 1,500 pound drill rig that was attached to the end of a 75-foot long line at a terrain elevation of approximately 7,000 feet msl. As the drill was being lifted off the ground, the helicopter "suddenly [and] violently accelerated (pitched) down [and] left." The pilot attempted to correct the uncommanded movement by applying right aft cyclic; however, the helicopter began a "rapid spin to the left." A ground witness observed the helicopter complete 3 or 4, 360-degree rotations. The pilot then closed the throttle to the flight idle position, and the left rotation stopped. The helicopter entered a descent toward the terrain with approximately 10 knots of forward airspeed. Approximately 30-40 feel above ground level (agl), the pilot pulled the "remaining" collective to slow the descent and rotor RPM. The helicopter's main rotor blades contacted trees, and subsequently the helicopter came to rest on its right side. During the accident sequence, the pilot did not jettison the external load. The pilot reported the wind conditions as "calm" and the temperature 71 degrees Fahrenheit at the time of the accident. Examination of the airframe, systems, and a functional test of the engine revealed no anomalies. The reason for the loss of control was not determined.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the loss of control during external load operations for undetermined reasons.

Full narrative available

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