What happened
Approximately 20 minutes into a cross-country flight, the pilot received clearance from air traffic control to climb to 17,000 feet MSL. Radar tracking showed the aircraft type reached a peak altitude of 16,800 feet MSL before initiating a series of descending turns. During a left-hand descending turn, the pilot notified controllers that the autopilot had disconnected and that the aircraft was in an unusual attitude. The pilot repeated this distress call multiple times, eventually stating that efforts were being focused on recovering the aircraft. Although witnesses heard the engine overhead for several minutes, visibility was obscured by a low cloud ceiling. The aircraft was operating in instrument meteorological conditions at the time of the incident.
Findings
Post-accident inspections of the engine and mechanical systems showed no failures that would have prevented standard operation. However, investigators discovered a loose screw within the pitch servo housing of the autopilot system. This screw, which was intended to secure a high-wattage resistor to the solenoid housing, showed signs of corrosion in its threads, suggesting it was not properly engaged. While the exact operational effect of this loose screw remains unconfirmed, the pilot failed to follow established procedures for managing an autopilot malfunction.
Environmental factors likely played a role, as the flight likely encountered icing and turbulence, despite the aircraft being equipped with ice protection systems. Regarding the pilot, toxicology reports identified levels of diphenhydramine, a sedating antihistamine, that exceeded therapeutic limits. This medication impairment likely hindered the pilot's ability to recover the aircraft from its unusual attitude. While ethanol was detected in some samples, investigators could not confirm if this resulted from ingestion or postmortem processes.