Most of the rivets in the repair of the CI-611 aft belly skin were found by Aviation Safety Council investigators to have been overdriven (see ASW, June 30). The implication is that these so-called "bucked rivets" hastened fatigue. Aubury points out that, "on the contrary, there are good studies showing that excessively bucked rivets extend fatigue life by putting the surrounding material in compression."
Indeed, according to a 1997 Boeing [NYSE: BA] paper, rivet installation under "controlled high squeeze force" can raise the life of a three-row countersunk-rivet lap splice from no more than 100,000 flight cycles to failure to almost 500,000 cycles. In fact, a combination of techniques, including rivets squeezed into position and increasing the overlap of the spliced joint could result in a pressurized fuselage with a 200-year service life (see ASW, Dec. 23, 2002).
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