Incident Details
A helicopter pilot departed from a mountainous work site with the intention of returning to Salt Lake City, Utah. The weather was clear at the work site, which had an elevation of 6,700 feet. However, fog was present at lower elevations. After descending into the fog, the pilot began to hover while maintaining a slow forward speed over snow-covered terrain.
Passenger Account
A passenger on board reported that where rocks protruded through the snow, they provided a visual reference. The passenger noted that suddenly there were no rocks visible, indicating a change in the terrain.
Loss of Reference
As the helicopter proceeded over an open area, the pilot lost ground references. The pilot stated that he may have experienced vertigo, as he believed he was approximately on the ground when the helicopter struck the ground and rolled over. The crash site was at an elevation of about 5,000 feet.
Conclusion
The accident occurred due to the pilot's loss of ground references in fog over snow-covered terrain, leading to a misperception of altitude and subsequent impact with the ground.