NTSB Factual Report

On March 3, 2007, about 1610 Alaska standard time, a Hughes 369D helicopter, N5134V, sustained substantial damage while hovering in ground-effect, when its tail rotor was struck by a moose during a game management operation, about 1 mile southwest of the Gustavus Airport, Gustavus, Alaska. The helicopter was being operated by Temsco Helicopters Inc., Ketchikan, Alaska, as a visual flight rules (VFR) on-demand passenger flight under Title 14, CFR Part 135, when the accident occurred. The commercial certificated pilot and sole passenger were not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on March 5, the chief pilot for the operator said the helicopter was involved in a moose tagging operation for the Alaska State Department of Fish and Game. He said the moose was shot with a tranquilizer dart from the helicopter, and that the helicopter is used to block the moose's path to prevent them from running into water and drowning, or running into an area where the tranquilized animals cannot be handled safely. He said the helicopter was hovering, waiting for the animal to "go down." The chief pilot said that the pilot of an airplane was orbiting above, and saw the moose charge the helicopter. According to the chief pilot, the airplane pilot stated that as the helicopter attempted to evade the moose, the moose reared, or jumped, contacting the helicopter's tail rotor. The airplane pilot said that the helicopter made three complete 360 degree rotations before it landed.

The helicopter pilot reported that he was not aware that the moose contacted the tail rotor. He indicated he had a loss of directional control, and said that he made a hovering autorotation to the ground. According to the chief pilot, the flex coupling between the drive shaft and the tail rotor gearbox failed. He said the spinning drive shaft cut through the tail boom adjacent to the gearbox, and separated the tail from the rest of the airframe.

On April 2, the chief pilot told the IIC that their past 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 this past practice had served them well, and the pilot and scientist aboard the helicopter felt the distances were appropriate. He said this was the first incidence of extreme, erratic, behavior on the part of a darted animal. In a written statement to the NTSB dated March 14, the chief pilot reported that due to this incident, the company had 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.

NTSB Probable Cause

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.