NTSB Identification: ANC07LA022.
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Nonscheduled 14 CFR
Accident occurred Saturday, March 03, 2007 in Gustavus, AK
Probable Cause Approval Date: 06/27/2007
Aircraft: Hughes 369D, registration: N5134V
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.

The helicopter was being operated as a visual flight rules on-demand passenger flight under Title 14, CFR Part 135. The purpose of the flight was to tranquilize moose for capture and collaring. The company's chief pilot said a moose was shot with a tranquilizer dart from the helicopter, and that the helicopter was used to block the moose from moving into a hazardous area. The pilot of an airplane orbiting above said the moose charged the helicopter, and that as the helicopter attempted to evade the moose, the moose reared, or jumped, contacting the helicopter's tail rotor. The helicopter pilot reported a loss of directional control, and made a hovering autorotation to the ground. The flex coupling between the drive shaft and the tail rotor gearbox failed, and the spinning drive shaft cut the tail boom and separated the tail from the rest of the airframe. According to the chief pilot, the company's practice had been for the helicopter to hover/maneuver about 10 feet above the ground, and no closer to the darted animal than 10 feet horizontally. He said the pilot and scientist aboard felt the distances were appropriate. He said this was the first incident of extreme, erratic, behavior on the part of a darted animal, and that due to this incident, the company has revised its procedure, and now requires the pilot to maintain 30 feet of altitude above the ground and 30 feet horizontally from a darted animal.

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

The inadequate clearance from a tranquilized moose while hovering in ground effect, and the operator's inadequate procedures for such operations, which resulted in an in-flight collision with the moose. Factors associated with the accident were the moose, a sheared tail rotor drive shaft, and the resultant lack of tail rotor anti-torque control.

Full narrative available

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