BFO92FA025

The aircraft was parked at the arpt 4 days prior to the flight. Acft parked nearby were snow covered. Although the preflight of the acft or takeoff was not witnessed, airport personnel said the pilot borrowed a broom to use for about 10 minutes. 15 minutes later the acft crashed. The acft struck the ground east of rwy 16R in a left bank attitude, about halfway down the rwy, where it touched down in snow covered grass. The acft travelled 298 feet across the ground before it struck a six-foot deep drainage ditch, located parallel and 227 feet from the rwy, and erupted on fire. The examination of the acft did not disclose evidence of mechanical malfunction. Shortly after the accident, as part of the investigation, snow was removed from another aircraft parked near the accident acft. Ice was underneath the snow and could not be removed. The ramp area where the accident acft was parked was checked and airfoil shaped ice was found on the ground where the tail was positioned, but none where the wing was positioned.