What happened
A pilot departed late at night into marginal VFR weather conditions without obtaining a weather briefing. The pilot was not instrument rated for such conditions. Prior to departure, a witness observed that the pilot appeared somewhat tired, though no mechanical issues were apparent with the aircraft.
During the flight, the aircraft entered an area characterized by clouds, rain, and moderate turbulence, all of which had been forecasted. Radar data indicates that the airplane entered a rapid descending turn from approximately 5,700 feet MSL. Following this maneuver, both radio and radar contact were lost. The aircraft underwent an in-flight breakup, with wreckage distributed over a 3/4 mile area.
The investigation
An examination of the structural fractures revealed that the stabilators and the left wing failed due to downward overload. Additionally, the right outboard wing panel failed upward from overload, and the vertical stabilizer experienced failure to the right due to torsional loads. While the aircraft had undergone recent stripping and repainative work, investigators found no evidence of any pre-accident mechanical deficiency.