Primary finding
Probable cause
The non-helicopter-rated pilot's improper decision to operate the helicopter at low-level and his inability to adequately see the horizon over snow and ice, which resulted in controlled flight into terrain.
Investigator assessment
Analysis narrative
The non-helicopter-rated pilot reported that while performing a bank, at low level, above a frozen river, he lost sight of the horizon and the helicopter impacted the frozen river. The helicopter came to rest on its left side, which resulted in substantial damage to the main rotor, tailboom, and cockpit structure. The non-helicopter-rated pilot further reported to a representative of the Federal Aviation Administration and Sheriff's Deputies that the helicopter was functioning "normally" at the time of impact and that "somehow I must have lost sight of the horizon in all the snow and ice." No preimpact malfunctions or abnormalities were noted with the helicopter that would have precluded normal operation.
Source record
Factual narrative
The non helicopter-rated pilot reported that while performing a bank, at low level, above a frozen river, he lost sight of the horizon and the helicopter impacted the frozen river. The helicopter came to rest on its left side, which resulted in substantial damage to the main rotor, tailboom, and cockpit structure. The non helicopter-rated pilot further reported to a representative of the Federal Aviation Administration and Sheriff's Deputies that the helicopter was functioning "normally" at the time of impact and that "somehow I must have lost sight of the horizon in all the snow and ice." No preimpact malfunctions or abnormalities were noted with the helicopter that would have precluded normal operation.