NTSB Identification: DEN01LA154.
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Accident occurred Sunday, September 02, 2001 in Kemmerer, WY
Probable Cause Approval Date: 02/20/2002
Aircraft: McDonnell Douglas 369E, registration: N440TJ
Injuries: 1 Uninjured.

NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot was transporting bags of seismic equipment by long line to a remote site. While he hovered into the wind waiting for a flagger, the helicopter was struck by a wind gust and started turning right. The pilot applied left pedal, but was unable to stop the rotation. The helicopter struck terrain, breaking off both skid legs, tail rotor blades, and tail rotor gearbox. FAA's Advisory Circular 90-95 defines the loss of tail rotor effectiveness as "a critical, low-speed aerodynamic flight characteristic that can result in an uncommanded rapid yaw rate which does not subside of its own accord and, if not corrected, can result in the loss of aircraft control." Some of the conditions conducive to LTE include (1) a high power setting, (2) low airspeed, and (3) a tailwind or left crosswind.

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

loss of tail rotor effectiveness while hovering. A contributing factor was the wind gust.

Full narrative available

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