Accident Sequence
Approximately 10 minutes after departure, while operating in heavy, wet, blowing snow, the helicopter suffered a loss of engine power. The aircraft was at an altitude of roughly 100 feet above ground level at the time. Upon the first indication of the power loss, the pilot initiated an autorotative landing and successfully touched down in an open field. During the landing, the main rotor blades flexed downward and impacted the tail boom. The auto-ignition system had activated, and the engine was running when the helicopter landed.
Investigation Findings
An investigation determined that the engine's particle separator had become completely blocked by snow. The aircraft was equipped with a particle separator differential pressure sensor and a cockpit warning light system intended to alert the pilot of such blockages. However, the pilot did not receive any advance warning from these systems. Consequently, the pilot did not manually open the particle separator bypass door before the engine flamed out.
Conclusion
The investigation revealed that the particle separator was completely clogged with snow, and the pilot did not receive a warning from the differential pressure sensor and cockpit light system. The pilot therefore did not manually release the bypass door before the engine lost power.