NTSB Identification: DEN05LA137.
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Accident occurred Tuesday, September 13, 2005 in Rock Springs, WY
Probable Cause Approval Date: 08/29/2006
Aircraft: Bell 47G-3B-1, registration: N24SD
Injuries: 2 Uninjured.

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

According to the pilot, he was maneuvering at approximately 25 feet agl. The pilot stated that he heard a grinding noise and the "helicopter yawed to the right a couple of times." He stated that the engine began to overspeed and he initiated an autorotation. The pilot stated that the helicopter impacted the ground hard, resulting in substantial damage. An examination, revealed that all six shearbolts had failed. Examination of the fracture faces of the six shear bolts revealed signatures consistent with a shearing action. The examination of the helicopter airframe, engine, transmission, and remaining systems revealed no anomalies.

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

the pilot's failure to maintain control of the helicopter during the attempted autorotation after he experienced an engine overspeed that occurred for reasons undetermined.

Full narrative available

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