Misshapen and misaligned rivet holes in parts of the fuselage removed from a Southwest Airlines 737-300 has lent more credence to theories that a manufacturing flaw led to the eventual failure of the lap joint during an April 1 accident in which a five-foot-long tear developed in the roof of the airplane while en route from Phoenix to Sacramento. A rapid depressurization occurred at 34,000 feet, forcing the crew to divert to Yuma, Ariz.
Non-destructive eddy current inspections conducted around intact rivets on the removed skin section forward of the actual tear revealed cracks at nine rivet holes in the lower rivet row of the lap joint. An X-ray inspection of the skin located forward of the rupture location revealed gaps between the shank portions of several rivets and the corresponding rivet holes for many rivets associated with the suspect portion of fuselage. Upon removing selected rivets, inspectors found a slight offset in the holes in the upper and lower skin and “many” out-of-round holes on the lower skin.
