SEA98LA069

While reducing power in the initial climb in order to establish cruise flight, the pilot of the helicopter experienced a partial engine power loss, followed by a complete loss of power about 15 seconds later. The pilot executed an autorotation to an emergency landing in a freshly plowed field, whereupon the main rotor flexed downward and contacted the tail boom during the touchdown. A post-accident inspection of the engine revealed that the number two connecting rod had failed near where it attaches to the crankshaft, ultimately leading to a total engine failure. Because both relevant fracture surfaces of the connecting rod were severely damaged and disfigured by repeated rotational impact pounding, the rod was not submitted for metallurgical failure mode examination.

On May 3, 1998, approximately 1200 Pacific daylight time, a Bell 47G3B2A helicopter, N7965J, experienced a hard landing after an inflight total loss of engine power near Stanwood, Washington. The commercial pilot and his two passengers were not injured, but the aircraft, which was owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 sightseeing flight, which departed the Stanwood Fairgrounds about one minute earlier, was being operated in visual meteorological conditions. No flight plan had been filed, and there was no report of an ELT activation.

According to the pilot, he had just taken off and had been airborne for less than a minute when he reduced power in order to establish level flight at about 300 feet above the ground (AGL). As he reduced the power, he heard a loud bang and felt a "high-speed" vibration. Believing that he had experienced a partial power loss, the pilot entered an autorotation and checked to make sure he still had tail rotor authority. About 15 seconds into the autorotation, the engine quit and the vibration "dissipated." The pilot then continued his autorotation to a point where he could complete an emergency landing in a freshly plowed field. According to the pilot, he exaggerated his flare to bring his forward speed to nearly zero, in order to keep the aircraft from rolling over if a skid were to sink into the soft dirt. As the helicopter touched down, the contact with the ground was hard enough that the main rotor flexed downward and impacted the tail boom.

A post-accident inspection of the engine revealed that the number two connecting rod had failed near where it attaches to the crankshaft, leading to a catastrophic failure of other internal engine components. Because the two relevant fracture surfaces on the number two connecting rod were severely damaged and disfigured by repeated rotational impact pounding, the rod was not submitted for metallurgical failure mode examination.