Preflight and Departure
Before the personal instrument flight rules flight, the pilot obtained a preflight weather briefing indicating that instrument meteorological conditions, convective activity, and moderate-to-severe icing conditions would be present along the route of flight.
In-Flight Events
According to track data, while navigating to avoid weather, the pilot was using the autopilot for maneuvering. After reporting to air traffic control that the airplane would be turning direct to its destination, the performance analysis of track data showed that the airplane began a slight left turn with a bank angle of about 10°, consistent with the intended route. However, the turn then reversed, and the airplane began banking to the right, reaching about 120° right wing down during the next 70 seconds, accompanied by a slow oscillation in pitch attitude.
Satellite imagery indicated that the airplane was likely in instrument meteorological conditions when it began a rapid descent at a rate of about 7,000 feet per minute.
Postaccident Examination
Postaccident examination of the airplane and the right engine (the left engine was not recovered) revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.
Analysis of Flight Dynamics
The dynamics of the airplane’s movements after the right turn began indicated that the airplane likely was not being actively controlled when it diverted from the intended flightpath. The circumstances were consistent with the pilot’s lack of timely recognition that the autopilot was disengaged. The available evidence precluded a determination of where the pilot’s attention was directed while navigating direct to the destination. However, turbulence would have increased the pilot’s workload, and restricted visibility conditions would have prevented the pilot’s use of outside cues to detect deviations in attitude. Additionally, initial roll rates might not have provided reliable cues of the developing bank, and convective conditions would likely have made it difficult for the pilot to detect and recover from the fully developed unusual attitude.
Probable Cause
The pilot’s failure to maintain control of the airplane while maneuvering in instrument meteorological conditions, which placed the airplane in an unusual attitude from which the pilot could not recover. Contributing to the accident was the convective and turbulent weather.