What happened
The pilot had received a weather briefing and filed an instrument flight rules (IFR) flight plan to Boeing Field in Seattle, Washington. Departing from Kalispell, Montana, at 11:35 Mountain Standard Time, the pilot proceeded toward the destination. Upon reaching the Spokane area, the pilot reviewed weather reports for Seattle and determined that conditions were unsuitable for arrival. Consequently, the decision was made to turn around and return to Kalispell.
By the time the aircraft approached Kalispell, weather conditions there had deteriorated significantly. The pilot was cleared for a contact approach but later advised Salt Lake Air Route Traffic Control Center (ARTCC) that he had sighted a small lake below. At this point, the pilot cancelled IFR and proceeded under visual flight rules (VFR).
Ice fishermen in the area observed the aircraft making several passes over the lake before hearing the sound of an impact. Witnesses described the weather as having low ceilings, reduced visibility, snow, and fog. The pilot was unable to recall the specific events leading up to the accident but surmised that he may have attempted a precautionary landing due to an accumulation of airframe ice.
Findings
Flight precautions for moderate rime ice in clouds and precipitation from the freezing level to 14,000 feet had been forecast for the area. The combination of deteriorating weather, including low ceilings and reduced visibility, along with the presence of moderate rime ice, contributed to the incident. The pilot's inability to recall the final moments suggests a possible loss of situational awareness or control due to these adverse conditions.
Safety message
Pilots operating in environments with forecast moderate rime ice should remain vigilant for airframe ice accumulation. When weather deteriorates rapidly, early decision-making regarding diversion or return is critical. Cancelling IFR in marginal visual meteorological conditions (MVFR) or worse requires careful assessment of visibility and ceiling heights to ensure safe VFR flight.