What happened
The incident began when the pilot noticed an unusual noise during flight. A seat belt had become caught in the open door and was banging against the exterior of the aircraft. Concerned about the situation, the pilot decided to land immediately to secure the loose item.
During the approach and landing phase, the downwash from the rotor system disturbed the snow on the ground. This action created a dense cloud of blowing snow that obscured the pilot's view of the terrain. Unable to see the ground, the pilot executed a hard landing. The impact caused the helicopter to roll over to the right.
The investigation
Examination of the event focused on the sequence of events leading to the rollover. Investigators noted that the primary trigger was the seat belt caught in the door. The subsequent loss of visual reference was directly attributed to the snow conditions exacerbated by rotor downwash.