What happened
During a routine descent, a twin-engine aircraft experienced a catastrophic structural failure when the right wing separated from the fuselage. This separation led to an uncontrolled descent, resulting in the aircraft impacting the ground. At the time of the accident, the airframe had logged a total of 20,457 flight hours. The aircraft had been in service for only 52 hours following its most recent annual inspection, which had been completed by the operator three weeks before the event.
Findings
Investigation of the aircraft's maintenance history revealed that the right wing had undergone various repairs since 1988, including work on the skin, rivets, and the wing stub spar straps, as well as repairs to the right main landing gear.
Metallurgical analysis determined that the primary cause of the failure was the fatigue failure of the right wing's front spar. This fatigue originated at a site containing rough machining marks and mechanical damage. Because primer was found covering the damaged area, investigators concluded that the damage likely occurred during the initial manufacturing process. While it was unclear if the machining marks or the mechanical damage alone initiated the fatigue, the crack eventually spread. Secondary fatigue cracks were also identified on the forward auxiliary spar and the rear spar, which were attributed to load shedding as the primary crack in the front spar expanded.