Incident Sequence
The airplane was cruising at 11,000 feet when air traffic control (ATC) observed it deviating more than 40 degrees from its assigned heading. The controller contacted the pilot, who stated he would correct the heading. ATC then offered a direct course to the destination, which the pilot accepted. Subsequently, the controller observed the airplane execute what was described as a "hard left turn" and attempted to contact the pilot again, but received no response. The airplane then lost 4,000 feet over a 24-second period, after which radar contact was lost.
Witness Observations
Witnesses on the ground reported seeing the airplane descend out of the clouds in a vertical spiral. They then observed the left wing separate from the aircraft. The engine was noted to be running at an overspeed condition during the descent.
Toxicological Findings
Toxicological testing of the pilot, a retired medical doctor, revealed the presence of several substances in his system: a barbiturate, an antidepressant, an antihistamine sometimes prescribed as a sleep aid, and quinine.