The RAE also reconstructed about two-thirds of G-ALYP at Farnborough and found fatigue crack growth from a rivet hole at the low-drag fibreglass forward aperture around the Automatic Direction Finder, which had caused a catastrophic break-up of the aircraft in high-altitude flight.
22.
The critical problem proved to be a combination of an inadequate understanding of the effect of progressive metal fatigue as the fuselage undergoes repeated stress cycles coupled with a misunderstanding of how aircraft skin stresses are redistributed around openings in the fuselage such as windows and rivet holes.
23.
Also, the fuselage failure initiated in the lap joint along S-10L; the failure mechanism was a result of multiple site fatigue cracking of the skin adjacent to rivet holes along the lap joint upper rivet row and tear strap disbond which negated the fail-safe characteristics of the fuselage.
24.
The investigation disclosed " evidence of fatigue cracks in the right wing's lower surface skin panel, with origins beneath the forward doubler . . . . The origin points were determined to be in rivet holes which join the external doubler and the internal stringers to the lower skin panel.
