What happened
During a daylight flight in visual meteorological conditions, an airplane departed from its home base for an 18-nautical mile trip intended for a practice instrument approach. After contacting approach control to request a practice ILS approach, the pilot was instructed to fly northwest and maintain an altitude of 2,500 feet MSL. However, radar data showed the aircraft maintained a northerly heading instead of the requested northwest direction.
At approximately 11:13:48, the aircraft was positioned roughly 5 miles southwest of the destination airport at 1,900 feet MSL, traveling at 172 knots. Following instructions from the controller to turn southbound and avoid Class C airspace, radar coverage became intermittent. By 11:14:29, the aircraft was detected 4 miles southwest of the destination at 1,800 feet MSL, with its ground speed dropping to 106 knots and its heading shifting to 101 degrees.
As the aircraft continued an east-southeast path, its speed further decreased. At 11:14:58, the aircraft entered a rapid descent, losing 1,500 feet of altitude in just 15 seconds. The final radar contact occurred at 11:15:13, showing the aircraft at 200 feet MSL with a ground speed of 64 knots. Witnesses reported seeing the aircraft enter a flat spin before striking a shallow canal in a residential neighborhood. The aircraft impacted the water in a nearly level attitude.
Findings
Post-accident investigations found no mechanical failures in the airframe or engines that would have hindered normal flight. While testing showed that the electronic engine control units could trip to manual mode due to electrical overstress, this would not have prevented the pilot from manually managing power and temperature.
However, toxicology results indicated that the pilot had a concentration of chlorpheniramine, a sedating antihistamine, in his bloodstream that was more than ten times the level expected from a standard over-the-counter dose. It is concluded that the pilot's judgment and performance were significantly impaired by high levels of this medication.