What happened
The flight departed under visual meteorological conditions but transitioned into instrument meteorological conditions while climbing through 12,8-00 feet. During the ascent, air traffic control notified the pilot of rime icing present between 15,000 and 17,000 feet. Although the pilot initially indicated the conditions were manageable, the pilot later reported vibrations and requested a higher altitude. After being cleared to flight level 200, the aircraft type reached a maximum altitude of 17,800 feet before performing a sharp left turn and beginning a rapid descent. During the descent through 17,400 feet, the pilot began an emergency declaration for N731CA before all communications ceased.
The aircraft struck a paved surface and a wooded median on an interstate highway, resulting in a post-accident fire. Debris, including the rudder, elevator, horizontal stabilizer, and the outboard section of the right wing, was discovered approximately 1/4 mile southwest of the main wreckage in a residential zone. Witnesses observed components separating from the plane during its descent.
Findings
Investigation of the wreckage determined that the outboard portion of the right wing detached during flight at a low altitude. This separation subsequently struck and severed parts of the empennage. There was no evidence of prior mechanical issues that would have prevented the engine or airframe from operating normally. While an AIRMET advisory had noted moderate icing in the area, no severe icing was specifically forecasted. However, other pilots in the vicinity reported severe icing conditions. The pilot operating handbook for the aircraft type explicitly prohibited flight in severe icing. It is believed that the pilot either failed to recognize the severity of the icing or failed to take immediate action to exit the conditions despite the known risks.