What happened
During an approach under instrument meteorological conditions, the pilot of the aircraft began deviating from the assigned approach course and experienced rapid changes in altitude. The air traffic controller noted these deviations as the aircraft approached the final approach fix. During the sequence, the pilot communicated that the aircraft was experiencing various difficulties and subsequently received vectors toward an alternate airport. While attempting an ILS approach, the pilot expressed uncertainty regarding whether the aircraft was properly established on the course. The controller observed the aircraft descending below the required glide slope intercept altitude and instructed the pilot to climb back to 2,000 feet. In response, the pilot indicated that the aircraft was unstable and expressed a belief that the plane was experiencing icing.
Radar tracking showed the aircraft began a left descending turn from 1,900 feet approximately one minute before the signal was lost. At 17:51, the controller notified the pilot that the altitude had dropped to 1,000 feet and requested a climb to 3,000 feet, to which the pilot responded that he was attempting to maintain altitude. Radar contact was lost at 17:52 while the aircraft was at 800 feet. An eyewitness reported seeing the aircraft emerge from the clouds with a side-to-side wobbling motion before it performed a sharp left turn and struck the ground. The witness noted the engine sounded as though it were at full power.
Findings
Post-accident examination of the aircraft found no mechanical malfunctions occurring prior to the impact. At the time of the accident, an AIRMET Zulu was in effect for the area, warning of moderate rime or mixed icing in clouds below 12,000 feet, with the freezing level extending from the surface to 4,000 feet. While the wing leading edge and empennage de-icing boots were set to the automatic position, the propeller de-ice and windshield anti-ice switches were found in the off position. The pilot had approximately 200 hours of flight time in this specific model and had owned the aircraft for roughly two months. The crash occurred shortly after the end of civil twilight.