Accident Summary
A helicopter conducting an aerial survey was cruising at 400 feet above ground level in mountainous terrain. Without any warning, the engine experienced a flameout. The pilot immediately initiated an autorotation and located a suitable landing area. On final approach, the pilot observed a steel cable crossing the landing site directly in the helicopter's flight path. The pilot managed to fly over the cable, but during this maneuver, the main rotor rpm decayed, resulting in a hard landing.
Investigation Findings
Post-accident investigation disclosed that the engine would not operate at governor power level angles of less than 50 degrees. After bench testing, the power turbine governor operated normally when reinstalled on the engine. Test engineers reported that this condition, in all probability, indicates a contaminate was lodged in the power turbine governor. The contaminate was dislodged during the bench test.