Aviation Accident Summaries

Aviation Accident Summary CHI04LA027

Coleman, WI, USA

Aircraft #1

N3198C

Bell 206B

Analysis

The helicopter was destroyed by fire following a forced landing to a residential area following a complete loss of engine power. The pilot reported that he heard a loud "bang" from the back of the helicopter and lost all engine power. An autorotation was performed to the back yard of a residence at which time the main rotor of the helicopter struck a garage. The helicopter subsequently rolled onto it's side and burned. On-scene examination of the helicopter failed to reveal any anomalies attributable to a pre-impact defect. Further examination of the engine, fuel pump, fuel control unit, and the power turbine governor revealed no defects that would have prevented normal operation.

Factual Information

On November 3, 2003, about 1240 central standard time, a Bell 206B helicopter, N3198C, was destroyed when it burned after impacting a residential building following a forced landing resulting from a complete loss of engine power during cruise flight near Coleman, Wisconsin. The 14 CFR Part 91 positioning flight was operating in visual meteorological conditions without a flight plan. The pilot and his one passenger received minor injuries. The business flight originated from the Langlade County Airport, Antigo, Wisconsin, about 1220 and was en route to the pilot's residence in Abrams, Wisconsin. According to the pilot's written report he had completed patrolling powerlines, re-fueled the helicopter in Antigo, and was en route to Abrams. The pilot stated that about 15 to 20 minutes after departing Antigo, he heard a loud "bang" from the rear of the helicopter and lights and horns within the cockpit came on. He stated that he was over the town of Coleman, Wisconsin, and had to land in the back yard of a residence. He stated that he had to "flare hard at the bottom to avoid powerlines," and the tail struck the ground. Subsequent to the landing, one of the main rotor blades struck a garage and the helicopter rolled onto it's left side and subsequently burned. The helicopter was extensively demaged by the post-impact fire. Examination of the helicopter at the accident scene failed to reveal any anomalies that could be attributed to a pre-impact defect. The engine was removed from the helicopter and shipped to the manufacturer's facility where a teardown examination was performed under the direct supervision of a National Transportation Safety Board investigator. The exterior of the engine was sooted from the post-impact fire. The compressor section of the engine could not be rotated by hand prior to disassembly. After removal of the compressor case, fire damage was noted to the plastic liner of the case. The fire damage to the compressor case plastic prevented the compressor from being rotated. After removal of the compressor case, the N1 compressor section of the engine rotated freely. Other than the fire damage to the compressor case plastic, no damage was noted with regard to the compressor bearings, vanes, or blades. The remainder of the engine was able to be rotated freely. The turbine nozzles and turbine wheels were intact and no defects were noted. No anomalies were noted with respect to the engine. The engine fuel pump was removed and a teardown inspection performed at the manufacturer's facility under the direct supervision of a Federal Aviation Administration (FAA) inspector. The fuel pump exhibited sooting and evidence of close proximity to the post-impact fire. Upon disassembly, it was noted that the seals and o-rings within the pump had become brittle due to heat damage. No other deficiencies were noted during the examination. The fuel control unit and the power turbine governor were removed and tested at the manufacturers facility under the direct supervision of a FAA inspector. Both units exhibited sooting and evidence of close proximity to the post-impact fire. Both units were tested using the manufacturers specifications and no deficiencies were noted that would have prevented normal operation.

Probable Cause and Findings

The loss of engine power for undetermined reasons and the unsuitable terrain encountered for the forced landing. The garage building was a factor.

 

Source: NTSB Aviation Accident Database

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