Background
The flight was cleared to maintain 3,000 ft mean sea level (msl) until over the airport, then cruise. The pilot reported seeing lights on the ground and stated he was 15 miles from the airport.
Flight Progress
At 2013, the pilot said, "we oughta be able to cancel here." At that time, the aircraft was approximately 6 miles from the airport. The airport operator heard an aircraft flying low overhead and was able to see stars. Ground witnesses closer to the impact point reported very thick patchy fog with visibility around 200 ft. One witness observed the aircraft's navigation lights performing unusual maneuvering, while another saw the lights very low.
Accident Sequence
The aircraft impacted the ground in a left wing low, near level flight attitude. The wreckage was found in an area consistent with a downwind-to-base leg turn.
Approach Information
The airport has a single VOR/DME approach to runway 11, with a minimum descent altitude (MDA) of 1,260 ft and required visibility of 1 mile. The circling approach has an MDA of 1,420 ft and also requires 1 mile visibility.
Altimeter Setting
The pilot received an altimeter setting of 29.77. However, the aircraft's altimeter was set between 30.29 and 30.30.
Probable Cause
The official probable cause findings cite an in-flight collision with terrain during the approach phase (VFR pattern, base turn). Identified factors include dark night, fog, the pilot not performing an aborted landing, not maintaining proper altitude, and improper altimeter setting.