What happened
The flight was operating in cruise conditions at an altitude of 20,000 feet mean sea level (MSL). While navigating around convective build-ups, the aircraft inadvertently entered instrument meteorological conditions (IMC). Shortly after penetration into the cloud layer, the airplane encountered severe turbulence. This event caused several flight instruments to become unreliable, with indications that they had tumbled or failed.
Positive control of the aircraft was eventually regained at an altitude between 16,800 and 17,000 feet MSL. Following the incident, a physical examination of the airplane revealed substantial damage to the airframe.