ANC95LA107

The helicopter pilot was transporting a geologist in a remote area. After departing from a pickup site that was at an elevation of about 5,000 feet mean sea level, the pilot noticed a decrease in main rotor RPM, and the nose of the helicopter yawed. The pilot decreased collective pitch, but engine power and rotor RPM continued to decrease. The pilot turned the helicopter toward lower terrain and into the wind, then performed an autorotation on tundra covered terrain. During touchdown, the helicopter hit the ground hard, and the tail boom was severed by the main rotor blades. The engine was still running after landing. An inspection of the engine fuel control assembly revealed the presence of acrylamide contamination in the fuel inlet filter.

On July 18, 1995, about 1230 Alaska daylight time, a Hughes 500D helicopter, N8639F, crashed during a forced landing about 22 miles west of Paxson, Alaska. The helicopter was being operated as a visual flight rules (VFR) local area on-demand charter flight under Title 14 CFR Part 135 when the accident occurred. The helicopter, operated by Soloy Helicopters Inc., Wasilla, Alaska, received substantial damage. The certificated commercial pilot and the sole passenger were not injured. Visual meteorological conditions prevailed. A VFR flight plan was filed. The flight originated from a remote landing area near Summit Lake, Alaska.

The pilot reported that he was transporting geologists to remote areas around the accident site and had performed numerous takeoff and landings prior to the accident. While in cruise flight, the pilot noticed a decrease in the main rotor RPM and the nose of the helicopter noticeably yawed. The pilot decreased collective pitch, but the engine power and rotor RPM continued to decrease. He noted that the engine did not fail completely. The pilot selected an emergency landing area in rough terrain. During the touchdown, the helicopter hit the ground hard and the tail boom was severed by the main rotor blades.

After the helicopter was recovered, it was inspected on July 19, 1995, by a Federal Aviation Administration (FAA) airworthiness inspector from the Anchorage, Alaska, Flight Standards District Office (FSDO). No malfunction was noted during the inspection; however, the engine fuel control assembly and the power turbine governor were removed for additional testing. Both components were sent to the FAA's South Bend, Indiana, FSDO for testing at the AlliedSignal Aerospace, Engine and Accessories facility in South Bend.

On August 28, 1995, a functional test of the power turbine governor and the fuel control assembly was conducted at AlliedSignal and overseen by an FAA inspector. The examination of the power turbine governor revealed no mechanical malfunction. An examination of the fuel control did not reveal any mechanical malfunction; however, disassembly of the fuel control revealed that the fuel inlet filter was contaminated by a acrylamide material.