Preflight and Weather Conditions
Prior to flight, approximately 3 to 4 inches of snow had accumulated on the aircraft. The pilot stated that he swept the snow off except for one area he could not reach. Heavy snowfall and wet snow were reported as the aircraft was prepared for departure, during runup, taxi, and takeoff. The tower advised the pilot that visibility was 1/8 mile with fog and snow. The published takeoff minimum for this FAR Part 135 operation was 1/2 mile.
Takeoff and Accident Sequence
After the aircraft encountered a snowplow located 150 feet left of the runway, it continued over an embankment and came to rest inverted. Witnesses reported that the engines sounded normal and the landing lights were on. Visibility from the snowplow's position was estimated at 600 feet. The pilot reported a manifold pressure of 35 inches when descending, and that MAP increased with additional throttle. No engine roughness was noted.
Post-Accident Findings
Ice and snow were found on the upper tail surface. The elevator trim indicator showed full nose-down position, and the aileron trim indicator showed left bank.