In-Flight Breakup During Thunderstorm Encounter (N9114B)

Incident Overview and Weather Conditions Following clearance to descend to 12,000 feet and deviate around a large weather cell, the aircraft entered an area containing level two and three thunderstorms. The encounter with this severe weather led to an in-flight breakup, with debris scattered across a four-mile radius. During the structural failure, the right wing and empennage separated from the main fuselage. The left wing and its spar failed at the same location as the right wing, but the left wing remained attached to the fuselage. All three occupants on board were killed in the accident. ## Investigation Findings and Probable Cause The investigation determined that no pre-accident failure, malfunction, or metal fatigue of the aircraft was found. The official probable cause was identified as the pilot's continued flight into known adverse weather and exceeding the design stress limits of the aircraft. These actions resulted in the failure of the wing spars and the separation of the right wing and empennage. Contributing factors included the pilot's continued flight above the maneuvering speed (va), a lack of familiarity with the specific make and model of the aircraft, and the presence of thunderstorms.