Accident Sequence
The airplane was in a normal descent when the right wing separated in flight, leading to an uncontrolled descent and subsequent impact with the ground.
Aircraft Information
The aircraft had accumulated a total of 20,457 flight hours. The most recent annual inspection had been performed by the current operator three weeks before the accident, and the airplane had been flown 52 hours since that inspection.
Maintenance History
Available maintenance records indicated that, since 1988, maintenance personnel had made numerous repairs to the right wing. These repairs included addressing skin cracks, working rivets, wing stub spar straps, and the right main landing gear.
Metallurgical Examination
Metallurgical examination revealed that the right wing's front spar failed due to fatigue. The fatigue initiated at an area of mechanical damage and rough machining marks. The presence of primer covering the mechanical damage strongly suggested that the damage was produced during the manufacturing process. It could not be determined whether the mechanical damage or the machining, acting alone, could have caused the fatigue cracking to initiate. Fatigue cracking found on the rear spar and the forward auxiliary spar was most likely secondary fatigue due to load shedding as the crack grew in the front spar.
Probable Cause
The official probable cause was the fatigue failure of the right wing spar as a result of inadequate quality control during manufacture of the spar. A factor was the inadequate inspection of the right wing by maintenance personnel, which failed to detect the crack.