Lyman, WA, USA
N1088G
Hughes 369D
The pilot made two long-line movements of cargo in light dry snow. After completing the second load, the pilot noticed that the snow had turned wet and heavy, and he told the ground crew that he was leaving the area. As he turned to depart the area, one of the ground crew radioed him and said that he was going to pass near one of the loads, and suggested that he pick it up. The pilot maneuvered toward the load, and entered into a hover to swing the long-line hook forward. Just as he entered the hover, the engine lost power, and the pilot delayed his emergency autorotation to allow the ground crew person to find cover. Because the rotor system energy decayed during the pilot's intentional delay of the autorotation, he was unable to control the descent, and the helicopter settled onto the terrain at an excessive rate of descent. The pilot stated that when he changed the angle of attack to put the hook in the right location, he believes a layer of wet snow and ice crystals lifted off the canopy and entered the engine particle separator, leading to a loss of engine power. A postaccident inspection did not reveal evidence of any system malfunction or anomaly.
On January 4, 2007, approximately 1310 Pacific standard time, a Hughes 369D helicopter, N1088G, impacted the terrain after a loss of engine power about six miles south of Lyman, Washington. The commercial pilot, who was the sole occupant, received serious injuries, and the aircraft, which is owned and operated by Highline Helicopters, sustained substantial damage. The local 14 CFR Part 133, long-line flight was being operated in visual meteorological conditions in an area where there was falling snow and ice crystals. According to the pilot, he made two long-line movements of cargo in light dry snow. After completing the second load, the pilot noticed that the snow had turned wet and heavy. He therefore told the ground crew that he was going to get out of the area. But, as he turned to depart the area, one of the people on the ground radioed him and said that he was going to pass near one of the loads as he left the area. The individual suggested that the pilot pick up this one last load since he would pass so close to it. The pilot therefore maneuvered down toward the load, and then entered into a hover in order to swing the long-line hook forward. Just as he entered the hover, the engine lost power, and because the pilot delayed his autorotational descent in order to allow the ground crew person to find cover, most of the energy in the rotor system was used up by the time he lowered the collective. Because the rotor system energy was used up during the pilot's intentional delay of remedial action, he was unable to control the descent, so the helicopter settled onto the terrain at an excessive rate of descent. It was the opinion of the pilot that when he changed the angle of attack to put the hook in the right location, a layer of wet snow and ice crystals lifted off the canopy and entered the particle separator, leading to a flameout that did not relight. An FAA-directed inspection of the helicopter by representatives of McDonald-Douglas Helicopters and Allison (Rolls-Royce) Turbine Engines did not reveal evidence of any system malfunction or anomaly.
The pilot's intentional flight into adverse weather conditions, which resulted in a loss of engine power during hover due to snow and ice ingestion. Factors associated with the accident are the pilot's delayed remedial actions, and snow and icing conditions.
Source: NTSB Aviation Accident Database
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