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Accident investigation report completed and information captured
Narrative: The pilot reported that it was the second flight of the day. After an uneventful first flight, the helicopter returned to the airport to refuel and pick up new passengers. The purpose of the flight was to hunt game. As the passengers were getting into the helicopter, a rifle was dropped on the dash of the helicopter which turned the alt switch, master switch, and clutch switch to off. The pilot immediately turned the switches back on and conducted a hover power and final systems check. The helicopter then took off uneventfully. About 120 ft above the ground, the engine sputtered once then lost complete power. The pilot performed a left turning autorotation to a field. During the descent, the pilot increased the throttle, but the engine did not respond. The helicopter impacted trees before it landed hard on a small mound of dirt and came to rest nose low. During the impact sequence, the main rotor blade contacted and severed the tail boom. The pilot never reported that he conducted the '˜starting engine and run up' checklist before taking off. This was confirmed by an onboard video. The video also showed the ignition switch in OFF throughout the flight, the impact, and following the accident sequence.
During a postaccident engine run, the engine started uneventfully, and a magneto check was completed. When the ignition switch was in the right magneto position the engine rpm stayed the same instead of decreasing, indicating the magneto was not properly grounding. In addition, the engine continued to run despite the ignition switch being in the off position, indicating the engine was operating on one magneto. The ignition switch key was jiggled, manipulated, and even removed from the ignition switch, but the engine continued to run. The engine was shut down and electrical continuity was established from the ignition switch to the magnetos. The magneto grounding wires were examined and appeared to be properly secured. The wiring was tested with a volt/ohm meter and functioned normally. The grounding wires were reinstalled, and the engine was restarted. It operated normally and several magneto checks were normal. The magnetos were removed for a functional bench test and disassembly; no anomalies were noted with either magneto. The ignition switch was also removed, disassembled, and examined. No anomalies were found.
Even though functional and disassembly tests did not indicate a problem with the magnetos themselves, the right magneto did not ground appropriately during the initial engine run. The anomaly was unable to be recreated after the magneto grounding wires were removed and reinstalled.
Because the pilot did not perform all the required pretakeoff checks to ensure all the switches were in the correct positions prior to takeoff, the helicopter took off with the ignition switch in the OFF position. An undefined issue with the grounding wire caused the right magneto to not ground and allowed the helicopter to operate with the ignition in the 'off' position. The magneto likely grounded during the initial climb, and since the ignition switch was in the OFF position, the engine shut down.
Probable Cause: The pilot's inadequate pretakeoff checks which resulted in the magneto switch (key) remaining in the OFF position during the takeoff sequence and initial climb and the right magneto grounding intermittently.