N/A Airport
Aircraft Accident/Incident Report

Prairie Du Sac, Wisconsin 53578
Friday, August 6, 2004 19:59 CDT

The helicopter was destroyed by impact forces and post crash fire after it collided with a static wire spanning a lake bay inlet about 80 feet above the surface of the water. The Fenestron (tail rotor) assembly separated from the tail boom when it struck the wire and the helicopter subsequently entered an uncontrolled descent. The main helicopter body impacted a single-family residence located near the shoreline and came to rest on the ground next to the home. The pilot and pilot-rated passenger sustained fatal injuries. One person in the residence sustained minor injuries. Witnesses at several locations along the flight path reported a low-flying helicopter matching the description of the accident aircraft. One witness noted that it was "very fast" and at or below the top of their 70-foot high silos. Two witnesses to the accident sequence reported that they were in a boat on the lake and that they saw the helicopter descend toward their position. One of them noted that the aircraft's flight path was "very direct" and that it was not "wavering." As the helicopter passed overhead, they recalled components coming off the aircraft. They both stated that when they looked back the power lines were "bouncing." A third witness reported that she saw the helicopter dip low toward the water and then come back up toward the power lines. She saw the tail separate from the helicopter and the aircraft went over trees on the opposite side of the lake from her position. The power company reported that power was automatically interrupted in the area at the time of the accident. Technicians dispatched to the site reported that one of the static wires was wrapped around a transmission line. A post accident inspection of the helicopter did not reveal any anomalies associated with a pre impact failure. The Fenestron fracture surface exhibited directional metal transfer features and transferred zinc consistent with impact with a galvanized steel static line.

The pilot's intentional low-level flight toward the lake and his failure to maintain clearance from the static wire on power transmission lines. Contributing factors were the separation of the Fenestron (tail rotor) assembly from the tail boom as a result of the collision with the static wire and the subsequent loss of control.