Incident
During final approach to landing, approximately 16 feet of the left inboard trailing edge flap separated from the aircraft. The approach and landing were completed without further incident.
Investigation
The subsequent investigation examined the forward attachment fittings of the No. 3 flap track. Of the eight bolts securing the forward attach fitting to the wing, five showed signs of fatigue failure. The remaining three bolts exhibited overload type failures.
Findings
At the time of the accident, Boeing had not required any inspection requirements for the forward attachment bolts. The investigation concluded that the bolt failures were due to fatigue in five bolts and overload in three.