NTSB Identification: SEA96TA207.
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Accident occurred Wednesday, September 04, 1996 in SHERIDAN, WY
Probable Cause Approval Date: 05/30/1997
Aircraft: Bell 206L-3, registration: N253EV
Injuries: 1 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.
The helicopter pilot was attempting to drop water on a forest fire from a sling-loaded bucket. He was flying about 8,200 feet above mean sea level and in close proximity to mountainous terrain. Density altitude was about 11,600 feet, and high winds, gusts, turbulence, and smoke prevailed. As the pilot approached the target area to drop the water, he could not see the target and was advised that he had overflown it. He maneuvered the helicopter in an attempt to be in a position to drop the water after reacquiring the target. There was evidence that the pilot inadvertently encountered a loss of tail rotor effectiveness in unfavorable wind conditions. The helicopter began to spin to the right. The pilot attempted to recover by entering an autorotation; however, before he regained control, the helicopter impacted trees and was substantially damaged. An examination of the wreckage did not reveal evidence of preimpact mechanical deficiencies. The pilot had much experience in helicopters; however, he had no recent mountain flying experience nor any firefighting experience.'
The National Transportation Safety Board determines the probable cause(s) of this accident to be: the pilot's improper in-flight planning/decision, concerning maneuvers to position the helicopter for aerial application; and inadvertent loss of tail rotor effectiveness, which resulted in loss of directional control and subsequent collision with the terrain. Factors relating to the accident include unfavorable weather conditions (high wind, gusts, turbulence, smoke, and high density altitude); the pilot's lack of recent experience in type of operation, and the lack of suitable terrain for a safe autorotation. Full narrative available
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