On July 18, 1995, a Hughes 500D (registration N8639F) was involved in an aviation accident near Paxson, AK. Investigators recorded the probable cause as: FUEL STARVATION DUE TO ACRYLAMIDE CONTAMINATION IN THE FUEL CONTROL INLET FILTER. THE LACK OF SUITABLE TERRAIN FOR A FORCED LANDING WAS A RELATED FACTOR. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter transporting a geologist lost main rotor RPM and yawed after departure. The pilot autorotated onto tundra; the tail boom was severed by rotor blades. Inspection revealed acrylamide contamination in the fuel inlet filter.
Incident Description
A helicopter was transporting a geologist in a remote area. After departing from a pickup site located at an elevation of approximately 5,000 feet mean sea level, the pilot observed a decrease in main rotor RPM and the nose of the helicopter yawed. The pilot reduced collective pitch, but engine power and rotor RPM continued to decline. The pilot turned the helicopter toward lower terrain and into the wind, then performed an autorotation landing on tundra-covered terrain. During touchdown, the helicopter impacted the ground hard, and the tail boom was severed by the main rotor blades. After landing, the engine was still running.
Inspection Findings
An inspection of the engine fuel control assembly revealed the presence of acrylamide contamination in the fuel inlet filter.