Flight Details
The pilot received airport advisories from the unicom operator and requested the runway lights be increased. The airplane was subsequently observed approaching runway 23, which was served by a localizer approach.
Witness Account
A witness at the airport reported seeing the airplane flying in and out of low hanging clouds. The airplane appeared to be in level flight at an estimated altitude of 400 to 500 feet above ground level (AGL). It passed over the airport and entered a steep left turn. After approximately 90 degrees of turn, the airplane began a shallow descent. It rolled out of the turn before descending into terrain about one-quarter mile from the approach end of runway 28. The witness stated that engine sounds were heard throughout the descent.
Examination Findings
An examination of the airplane revealed no evidence of mechanical malfunction. A post-mortem examination of the pilot, who was the sole occupant and was killed, did not reveal evidence of impairment or incapacitation.
Probable Cause
The official finding determined the probable cause to be the pilot's improper IFR procedure by not maintaining sufficient altitude while circling to land. Contributing factors were the low ceiling and visibility conditions in fog.