Primary finding
Probable cause
The pilot's failure to maintain lateral control while hovering over an area of snow-covered terrain, in flat light conditions, which resulted in a dynamic rollover.
Investigator assessment
Analysis narrative
The commercial helicopter pilot reported that while flying over an area of flat and featureless, snow-covered terrain, deteriorating weather conditions with low ceilings, light snow, and flat light conditions reduced his visibility, so he elected to make a precautionary landing to wait for improved visibility. He said that while attempting to land, blowing snow from the main rotor downwash reduced his ability to discern topographical features on the snow-covered terrain. During touchdown, the helicopter drifted to the left, the left skid struck the snow-covered terrain, and the helicopter rolled onto its left side. The helicopter sustained substantial damage to the rotor system, tail boom, and fuselage. The operator reported that there were no preaccident mechanical malfunctions or anomalies that would have precluded normal operation.
Source record
Factual narrative
The commercial helicopter pilot reported that while flying over an area of flat and featureless, snow-covered terrain, deteriorating weather conditions with low ceilings, light snow, and flat light conditions reduced his visibility, so he elected to make a precautionary landing to wait for improving visibility. He said that while attempting to land, blowing snow from the main rotor downwash reduced his ability to discern topographical features on the snow-covered terrain. During touchdown, the helicopter drifted to the left, the left skid struck the snow-covered terrain, and the helicopter rolled onto its left side. The helicopter sustained substantial damage to the rotor system, tail boom, and fuselage. The operator reported that there were no preaccident mechanical malfunctions or anomalies that would have precluded normal operation.