Accident Details
While departing, the helicopter reached an altitude of 100 feet and an airspeed of 60 knots when the pilot noted an airframe vibration. Concurrently, a fuel filter caution light, engine power warning light and horn activated, followed by a loss of engine power. The pilot initiated an autorotation, but the subsequent landing was hard, causing the main rotor to sever the tail boom.
Investigation Findings
Post-accident examination revealed a leak in the fuel filter bypass switch. This leak allowed air to enter the suction-fed engine fuel system, disrupting fuel flow. Detailed inspection of the bypass switch found leakage occurring between the mating flange halves. The leakage was attributed to deteriorated safety wiring, which failed to maintain proper sealing of the flanges.
Maintenance History
The last scheduled maintenance on the helicopter had been performed 77 hours prior to the accident. The condition of the safety wiring indicated that maintenance procedures may not have been fully effective in preventing deterioration over time.