Aviation Accident Summaries

Aviation Accident Summary ANC05CA049

Elim, AK, USA

Aircraft #1

N422R

Bell 206B

Analysis

The airline transport certificated pilot was flying a high skid-equipped helicopter over flat, snow-covered terrain. As the flight progressed, visibility deteriorated to about one and one-half miles, making it difficult to discern the surface of the featureless terrain. The pilot said that he elected to make a precautionary landing, and wait for improved weather conditions. After landing, he decided to reposition the helicopter to a more suitable site. He said that just after takeoff, as the helicopter moved forward, flat light and worsening fog contributed to his inability to recognize any topographical features. He reported that while hover taxiing, the main rotor blades struck a snow-ridge, and the helicopter pitched forward. When the main rotor blades struck the snow-ridge, the main rotor mast sheered, and the helicopter rolled to the right, coming to rest upright against the snow-ridge. The helicopter sustained substantial damage to the fuselage, tail boom, main rotor blades, and transmission deck assembly. The pilot noted that there were no preaccident mechanical anomalies with the helicopter.

Factual Information

On March 15, 2005, about 1030 Alaska standard time, a high-skid equipped Bell 206B helicopter, N422R, sustained substantial damage after colliding with snow-covered terrain, about 12 miles east of Elim, Alaska. The helicopter was being operated as a visual flight rules (VFR) business/aerial photography flight, under Title 14, CFR Part 91, doing business as Thunderbird Helicopters, when the accident occurred. The helicopter was transporting a photographer from The Outdoor Life Network, covering the 2005 Iditarod sled dog race. The airline transport certificated pilot, and the sole passenger, were not injured. Visual meteorological conditions prevailed at the time of departure, and no flight plan was filed. The flight originated at the Koyuk Airport, Koyuk, Alaska, about 1000, and was en route to Elim. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on March 16, the pilot reported that after departing Koyuk, he proceeded westbound along the Iditarod trail, towards Elim. He said that at the time of departure, weather conditions were 800 feet broken, with visibility of 10 miles, but added that snow squalls were moving through the area. He said that as the flight progressed, the visibility deteriorated to about one and one-half miles, making it difficult to discern any topographic features on the surface of the flat, featureless, snow-covered terrain. The pilot said that he elected to make a precautionary landing, and wait for better weather conditions. After landing, he decided to reposition the helicopter to a more suitable site. He said that just after takeoff, as the helicopter moved forward, flat light conditions, and worsening fog, contributed to his inability to recognize any topographical features. He reported that while hover taxiing the helicopter, the main rotor blades struck a snow-ridge, and the helicopter pitched forward. As the main rotor blades struck the snow-ridge, the main rotor mast sheered off, and the helicopter rolled to the right, and came to rest upright against the snow-ridge. The helicopter sustained substantial damage to the fuselage, tail boom, main rotor blades, and transmission deck assembly. The pilot noted that there were no preaccident mechanical anomalies with the helicopter. The closest official weather observation station is Koyuk, which is located about 26 nautical miles northeast of the accident site. At 1016, an Aviation Routine Weather Report (METAR) was reporting in part: Wind, 160 degrees (true) at 4 knots; visibility, 10 statute miles; clouds and sky condition, 2,100 feet overcast; temperature, 36 degrees F; dew point, 30 degrees F; altimeter, 29.74 inHg.

Probable Cause and Findings

The pilot's continued flight into adverse weather conditions, and his failure to maintain adequate clearance while maneuvering, which resulted in an in-flight collision with terrain. Factors associated with the accident are flat light, whiteout conditions, fog, and snow-covered terrain.

 

Source: NTSB Aviation Accident Database

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