What happened
The pilot obtained weather briefings for the destination airport that indicated instrument meteorological conditions (IMC), including fog, mist, low visibility, and low ceilings. After departing, the pilot proceeded to the destination and was cleared for an ILSS approach.
While flying along the localizer course, approximately 0.5 miles from the runway approach end, the aircraft initiated a climb and a left turn toward the east. The aircraft continued turning left and headed north, subsequently entering a series of ascending and descending turns to various altitudes. During the final three minutes of flight, the aircraft performed 18 ascents and descents, with vertical speeds ranging from +4,600 to -6,000 fpm and altitudes fluctuating between 600 and 1,800 feet MSL.
Witnesses reported hearing the aircraft fly loudly overhead immediately before it collided with terrain. At the time of the accident, airport weather reports indicated fog, zero visibility, and a vertical visibility of 100 feet.
Findings
Two independent toxicology reports confirmed the presence of chlorpheniramine, a sedating antihistamine, in both the blood and urine of the pilot.