In Defective Fasteners Drive Structural Failures ForensisGroup® expert witness John D. Pratt, Ph.D., P.E., discusses failures of mechanically-fastened joints:
Structural failures can oftentimes be traced to a defective mechanically-fastened joint. For example, longitudinal and circumferential fuselage joints are among the most highly loaded parts of an airframe, subject to loading each time the aircraft is pressurized. Over many flight cycles improperly installed rivets can loosen, permitting microscopic movement between overlapping fuselage panels. Such movement leads to fretting fatigue cracks resulting in early failure. The highly publicized rapid decompression of Aloha Airlines flight 243 in 1988 resulted from such fatigue cracks along the fuselage joints. These cracks eventually grew long enough to connect with one another and catastrophic failure resulted.
While the Aloha Airlines case represents a failure of maintenance and engineering personnel to anticipate the impact of multi-site fatigue damage, there are in fact many causes of premature joint failure, ranging from inadequate supplier quality control to defective installation practices.
