Incident Overview
Following takeoff, as the wing flaps were retracted, the captain noted airframe vibration. In response, he dumped fuel and returned to land. Subsequent examination of the airplane revealed that the No. 1 movable flap fairing was missing.
Discovery and Examination
The fairing was located the following day in a field approximately three miles from the departure runway. Examination of the fairing showed that the two lower hinge bolts were missing. The hinges and bushings exhibited no evidence of deformation or failure.
Conclusion
The investigation did not specify a probable cause for the missing bolts or fairing separation.