Aniak, AK, USA
N111MT
Bell 206B
The helicopter was operating as a Title 14, CFR Part 91, positioning flight in visual meteorological conditions when it had a total loss of engine power while in cruise flight. The pilot said the first indication of a problem was the illumination of the auto-relight indicator, followed by the engine fail light. He initiated an autorotation towards a clearing, but was unable to reach it. The helicopter impacted trees about 30 feet above the ground. During the inspection of the engine, the compressor discharge pressure line (Pc line) was removed at the compressor scroll, and compressed air was applied. Technicians reported air escaping at the Pc line's junction with the fuel control unit. The B-nut on the Pc line was loose at the fuel control unit. There was evidence of fretting on the B-nut fitting, and there were smears of orange torque seal material on the B-nut. No torque seal material was present on the B-nut fitting. The engine logbook indicated the fuel control unit was replaced by company mechanics 178 hours prior to the accident.
On July 9, 2003, about 1800 Alaska daylight time, a Bell 206B helicopter, N111MT, sustained substantial damage during an in-flight collision with trees after a total loss of engine power, about 10 miles east of Aniak, Alaska. The helicopter was being operated as a visual flight rules (VFR) positioning flight under Title 14, CFR Part 91, by American Helicopters of Angleton, Texas. The solo commercial pilot received minor injuries. Visual meteorological conditions prevailed, and company flight following procedures were in effect. The helicopter departed Red Devil airstrip, Alaska, about 1730, and was en route to Aniak when the accident occurred. In a written statement provided to the NTSB dated July 9, the pilot said that during cruise flight, he noticed a slow reduction of engine power, and a subsequent total loss of engine power. He said the first indication of power loss was the illumination of the auto-relight indicator, followed by the engine fail light. He started an autorotation, and selected a landing zone. The pilot said he was unable to make it to the selected landing zone in the heavily wooded area, and the helicopter impacted trees, about 30 feet above the ground. After recovery of the helicopter, the engine was sent to Premier Turbines of Wichita, Kansas, for inspection. During the inspection on November 3, the compressor discharge pressure line (Pc line) was removed at the compressor scroll, and compressed air was applied to the Pc line. During normal operation, the Pc line provides compressed air (bleed air) from the compressor section of the turbine engine, to operate the fuel control unit. Technicians at Premier reported that air was escaping from the Pc line fitting at the fuel control unit. The B-nut on the Pc line was loose at the fuel control unit. There was evidence of fretting on the B-nut fitting, and there were smears of orange torque seal material on the B-nut. No torque seal material was present on the B-nut fitting. The engine logbook indicates the fuel control unit was replaced by company mechanics 178 hours prior to the accident. There were no known mechanical anomalies with the helicopter prior to the accident.
The compressor discharge pressure line (Pc line) B-nut coming loose at the fuel control unit, which resulted in a total loss of engine power, and subsequent in-flight collision with trees during an autorotation. A factor associated with the accident was the improper installation of the Pc line B-nut by company maintenance personnel.
Source: NTSB Aviation Accident Database
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