What happened
While operating a scheduled cargo flight to a remote village in western Alaska, the pilot experienced a partial loss of engine power. Due to the reduction in power, the pilot was unable to maintain the aircraft's altitude, resulting in a forced landing on a frozen lake.
The pilot reported weather conditions at the time of the accident as 4,000 feet overcast with 8 miles of visibility. However, other pilots operating in the same general area reported significantly worse weather, which was approaching instrument meteorological conditions.
Because of the extreme winter weather and the remote location of the crash site, investigators were unable to recover the aircraft for a physical examination. Consequently, the specific reason for the engine power loss remains unknown.