Accident Sequence
The private pilot was conducting a personal flight during daytime under instrument flight rules (IFR). After checking in with an air route traffic control center, radar data showed multiple altitude changes not matching assigned altitudes. An air traffic controller queried the pilot, who reported an autopilot problem. The pilot later requested clearance to deviate around weather at a higher altitude. As the airplane passed through several sectors, controllers understood the pilot was aware of adverse weather based on deviation information in the flight strip. However, the air traffic controller did not provide additional adverse weather information and updates as required by a Federal Aviation Administration order. General broadcasts of weather information were recorded on the frequency the pilot was using before the accident.
Weather Conditions
Multiple weather resources indicated rapidly developing multicellular to supercell-type convective activity with cloud tops near 48,000 ft. Forecasts and advisories warned of potential strong to severe thunderstorms with moderate-to-severe turbulence, hail, lightning, heavy rains, and high winds. Radar data showed that the pilot turned into the intense weather cells instead of away from them as he had requested.
Loss of Control
The pilot declared a "mayday" and reported losing visual reference and being in a spin. Damage to the airplane and witness marks on the ground were consistent with an impact in a level attitude and a flat spin. No mechanical anomalies were found that would have precluded normal operation before the loss of control and impact.
Investigation Findings
The investigation could not determine if there was an anomaly with the autopilot or if the rapidly developing thunderstorms and associated weather created a perception of an autopilot problem. An autopsy identified coronary artery disease in the pilot. Although coronary artery disease could lead to symptoms such as chest pain, shortness of breath, palpitations, or fainting, it was unlikely to have impaired the pilot's judgment during preflight briefings or en route decision-making. There was no evidence that a medical condition contributed to the accident. Toxicology testing found zolpidem in the pilot's blood and tetrahydrocannabinol and its metabolite in cavity blood, indicating use of two potentially impairing substances in the days to hours before the accident. It is unlikely that zolpidem use contributed to the accident, but the investigation could not determine whether marijuana use contributed to the cause.
Probable Cause
The pilot's improper decision to enter an area of known adverse weather, which resulted in the loss of airplane control. Contributing to the accident was the air traffic controller's failure to provide critical weather information to the pilot to help him avoid the storm, as required by Federal Aviation Administration directives.