What happened
Prior to flight preparation, the aircraft had accumulated three to four inches of snow. The pilot reported sweeping most of the snow off the airframe but noted an area that was inaccessible for cleaning. During the preparation phase, taxi, and runup, heavy wet snow continued to fall. The control tower advised the pilot that visibility was one-eighth of a mile due to fog and snow. Published takeoff minimums for this operation required one-half mile visibility.
After passing a snowplow located 150 feet left of the runway, the aircraft continued its ascent over an embankment and came to rest inverted. Witnesses reported that the engines sounded normal and landing lights were on. From their position near the snowplow, they estimated visibility at 600 feet. The pilot stated he was at 35 inches of manifold pressure when descending, which increased with additional throttle. No engine roughness was noted.
The investigation
Examination of the wreckage revealed ice and snow found on upper tail surface. The elevator trim indicated full nose down position, while aileron trim indicated a left bank.