What happened
NTSB summary, verbatimThe commercial helicopter pilot was flying three passengers to several remote sites in northern Alaska to collect snow samples. The snow was being collected from flat, featureless terrain. The pilot said that he was able to reach five of the six predetermined sites, but was unable to reach the sixth site due to low fog, reduced visibility, and flat light conditions. While attempting to return to the base camp, he encountered an area of low fog, which reduced his ability to discern a horizon. He said that the visibility diminished so that he was unable to discern any topographic features, and he elected to make a precautionary landing to wait for improved visibility. After about 3 minutes, he decided to return to the base camp. Just after takeoff, flat light conditions, and worsening fog conditions, reduced his ability to recognize any topographical features on the snow-covered tundra. He said that he initiated another landing, and lowered the collective when he believed the landing gear skids were on the ground. The skids were not on the ground, and the helicopter subsequently descended, and rolled to the right on ground contact. The helicopter continued to roll to the right, and the main rotor blades struck the ground. After striking the ground, the main rotor blades sheered off, and one main rotor blade struck the top left portion of the helicopter's cabin, passed through the left side of the cabin, and struck the passenger seated in the front left seat. The pilot reported that there were no preaccident mechanical anomalies with the helicopter.
Probable cause
the Board's determinationThe pilot's continued VFR flight into instrument meteorological conditions (IMC), and his spatial disorientation and loss of control during a subsequent landing. Factors associated with the accident are flat light and whiteout conditions, fog, and snow-covered terrain.
NTSB analysis
from the final reportThe commercial helicopter pilot was flying three passengers to several remote sites in northern Alaska to collect snow samples. The snow was being collected from flat, featureless terrain. The pilot said that he was able to reach five of the six predetermined sites, but was unable to reach the sixth site due to low fog, reduced visibility, and flat light conditions. While attempting to return to the base camp, he encountered an area of low fog, which reduced his ability to discern a horizon. He said that the visibility diminished so that he was unable to discern any topographic features, and he elected to make a precautionary landing to wait for improved visibility. After about 3 minutes, he decided to return to the base camp. Just after takeoff, flat light conditions, and worsening fog conditions, reduced his ability to recognize any topographical features on the snow-covered tundra. He said that he initiated another landing, and lowered the collective when he believed the landing gear skids were on the ground. The skids were not on the ground, and the helicopter subsequently descended, and rolled to the right on ground contact. The helicopter continued to roll to the right, and the main rotor blades struck the ground. After striking the ground, the main rotor blades sheered off, and one main rotor blade struck the top left portion of the helicopter's cabin, passed through the left side of the cabin, and struck the passenger seated in the front left seat. The pilot reported that there were no preaccident mechanical anomalies with the helicopter.