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At approximately 55 minutes and 110 miles after departure from elko and 38 minutes and 77 miles out from pocatello, the barrier inlet air filter light started to flicker. The barrier filter had just been changed less than a week before, and the PIC thought this was too early to see the light flickering, although the aircraft had been flying in a dirty/dusty/smokey environment on the stockade fire. The PIC had flown in worse conditions in other helicopters and had not had a barrier inlet filter come on. As the crew got closer to Burley the light was more on than flickering. The PIC opted to press the light button which bypasses the barrier filter.

At about 15 miles south of Burley, the PIC and crew discussed whether they should land at Burley or continue to pocatello. They decided to continue to pocatello as terrain was no longer a factor and the ETA was within 5 minutes of the planned 2120 arrival. It was essentially a “straight shot” with no need to vary course or altitude. The autopilot was set, the power setting was in the upper green and airspeed of 120 knots was maintained.

Approximately 1 minute and 2 miles after the decision was made to continue to pocatello, the pilot observed the mgt starting to rise into the yellow. In response, the PIC reduced power and began descending. Despite this, the mgt continued to rise. At an altitude between 1000-1500 feet, the mgt went past the 779 redline and kept going up despite power reduction. The PIC decided to make a precautionary landing and was looking for a suitable landing area, hoping to make a power-on landing. He saw a grass field, but it was on a slope, and an adjacent corn field which appeared to be somewhat less sloped.

The engine began to indicate an overspeed and the PIC lifted the collective twice to try to arrest the overspeed, but the engine did not respond to his control inputs (the PIC had used this technique in prior situations when maneuvering Bell 407’S and the RPM had always corrected quickly). Based upon this, the PIC decided commit to full down autorotation into the corn field. Right before his flare, the low RPM horn sounded briefly. The PIC flared hard above the cornfield and leveled the aircraft. Most of the airspeed had been depleted but the helicopter still had some forward movement as skids settled into the corn. The PIC timed his pitch pull at the bottom the best he could given that he could not see how tall the corn was. The PIC estimates the aircraft dropped the last 5 feet or so with some forward movement and nose attitude down but did not roll over. Due to this nose down attitude the seat belts took most of the force instead of the crew’s backs.

Immediately after landing, the engine came back on for about 10 seconds shaking the aircraft and crew violently. The PIC tried to reach for the rotor brake and the fuel shut off valve during this time, but due to aircraft’s shaking, he was unable to do so. However, within about 10 seconds, the engine quit.

The crewmembers in the rear seats were able to exit the aircraft and they helped extricate the front crew members.

The PIC and crew gathered away from the helicopter and began assessing one another’s injuries. They then decided to walk out to the grass field that was initially intended as the landing area and noted that the field had a barbed wire fence going through it.

The crew called their supervisors and gave waypoint info and decided to walk to the nearest road about half a mile toward a farming facility. Life flight arrived about the same time ambulances arrived. The crew all declined the helicopter ride and rode in the ambulances to Burley where they were all treated and given CT scans. They were all discharged at the same time with minor injuries at approximately 0200-0230 local.