Background
Approximately two and a half hours before the flight, the pilot obtained a weather briefing for a planned VFR flight. The weather specialist reported flight precautions for mountain obscuration with occasional moderate rime or mixed icing in clouds.
Flight
Just prior to departure, the pilot filed a VFR flight plan and checked the weather again for changes. When contacting Missoula Radio to open the flight plan, the pilot changed the VFR flight plan to an IFR flight plan. After takeoff, the pilot was cleared to 11,000 feet. Shortly after leveling at that altitude, the pilot reported picking up a load of ice and requested a lower altitude. Clearance was given to descend and maintain 9,500 feet.
Accident
A short time later, the pilot notified the controller that he was passing through 8,500 feet and unable to maintain altitude. Using another aircraft in the area to relay messages, the pilot reported that he was in instrument meteorological conditions (IMC). No further communications were received.
Search and Recovery
An initial search was unsuccessful. The wreckage was found nearly four months later in mountainous terrain.