Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747-100B SUD, - 200B, -300, -400, and -400D series airplanes. The existing AD currently requires repetitive inspections for cracking in fuselage stringers 8L, 8R, 10L, and 10R at body stations 460, 480, and 500 frame locations; and repair if necessary. This proposed AD would revise the applicability to include an additional airplane, and reduce compliance times for the initial inspection and repetitive intervals for Model 747-400 series airplanes that have been converted to the large cargo freighter configuration. This proposed AD results from findings of cracking in fuselage stringers 8L, 8R, 10L, and 10R at body stations 460, 480, and 500 frame locations. We are proposing this AD to detect and correct fatigue cracking in certain fuselage stringers, which, if left undetected, could result in fuselage skin cracking that reduces the structural integrity of the skin panel,and consequent rapid depressurization of the airplane.