KETCHIKAN, AK, USA
N1091S
Hughes 369D
The commercial certificated pilot was conducting an on-demand air taxi flight in a turbine-powered helicopter. While performing an aerial survey, about 100 feet agl, the engine-out annunciator sounded, and the pilot entered an autorotation. As the helicopter touched down in a small clearing, the pilot had the collective pitch control full up to cushion the landing. When the helicopter touched down, the engine power suddenly surged, and the helicopter then began to climb. During the pilot's efforts to control the helicopter, the main rotor blades collided with several trees, and the blades then severed the tail boom. Following the collision with the trees, the pilot rolled the throttle to the off position, but the engine would not shut-down. He then pulled the emergency fuel shut off. Examintion of the helicopter revealed that a bolt, used to connect the N2 governor input arm to an airframe mounted bellcrank, was missing. The bellcrank is connected to the helicopter's collective control linkage. As the pilot moves the collective control, through the bellcrank and governor input arm, engine power increases or decreases. The bolt is normally retained by a castellated nut, and then secured in-place by a cotter pin. Company personnel returned to the accident scene and located the missing bolt and nut lying on the ground, under the location where the engine access doors were opened during an inspection of the engine, before the helicopter was removed from the accident scene. Also found was a cotter pin with one broken side, but it could not be determined if the broken cotter pin was the missing pin from the bolt. The most recent inspection of the helicopter was a 100 hour inspection, conducted by company personnel, 51.8 service hours before the accident. Numerous company pilots had flown the helicopter before the accident. In addition, each pilot conducted an inspection of the helicopter before beginning flight operations. On the day of the accident, the helicopter had flown about 2.5 hours before the accident.
On July 21, 2003, about 0900 Alaska daylight time, a high skid-equipped Hughes 369D helicopter, N1091S, sustained substantial damage when it collided with trees during a forced landing following a loss of engine power, about 32 miles north of Ketchikan, Alaska. The helicopter was being operated as a visual flight rules (VFR) cross-country on-demand passenger flight under Title 14, CFR Part 135, when the accident occurred. The helicopter was operated by Temsco Helicopters Inc., Ketchikan. The commercial certificated pilot, and one passenger, were not injured. The other passenger received minor injuries. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect. The flight originated at the Temsco Heliport, Ketchikan, about 0830. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on July 21, the director of operations for the operator reported the pilot was conducting aerial surveys and was in a turn about 100 feet agl when the engine-out annunciator sounded, and the pilot entered an autorotation. As the helicopter touched down in a small clearing, the pilot had the collective pitch control full up to cushion the landing, and the throttle was still open. The pilot told the director of operations that when the helicopter touched down, the engine power suddenly surged, and the helicopter then began to climb. During the pilot's efforts to control the helicopter, the main rotor blades collided with several trees, and the blades then severed the tail boom. Following the collision with the trees, the pilot rolled the throttle to the off position, but the engine would not shut-down. He then pulled the emergency fuel shut off. Following recovery of the helicopter, the director of operations reported that a bolt, used to connect the N2 governor input arm to an airframe mounted bellcrank, was found to be missing. The bellcrank is connected to the helicopter's collective control linkage. As the pilot moves the collective control, through the bellcrank and governor input arm, engine power increases or decreases. The bolt is normally retained by a castellated nut, and then secured in-place by a cotter pin. The director of operations, along with company personnel, returned to the accident scene on July 23. They located the missing bolt and nut lying on the ground, under the location where the engine access doors were opened during an inspection of the engine, before the helicopter was removed from the accident scene. He also found a cotter pin with one broken side. He said he could not be certain if the broken cotter pin was the missing pin from the bolt. The most recent inspection of the helicopter, conducted by company personnel, was a 100 hour inspection on July 8, 51.8 service hours before the accident. Numerous company pilots had flown the helicopter before the accident. In addition, each pilot conducted an inspection of the helicopter before beginning flight operations. On the day of the accident, the helicopter had flown about 2.5 hours before the accident.
The improper installation of a bolt in the gas generator governor linkage by company maintenance personnel, which resulted in a loss of the bolt, a loss of engine power while maneuvering, and subsequent forced landing and collision with trees. Factors contributing to the accident were an inadequate preflight inspection by the pilot, and an uncommanded surge in engine power.
Source: NTSB Aviation Accident Database
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