Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-100B, 747-100B SUD, 747-200B, 747- 200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes. This proposed AD was prompted by reports of corrosion found on the mating surfaces between certain skin and stringers at circumferential skin splices. This proposed AD would require general visual inspections of the fuselage skin at certain lower circumferential splices for the presence of existing external doublers, repetitive inspections of the fuselage skin, and related investigative and corrective actions if necessary. We are proposing this AD to detect and correct compromised fillet seals, which can result in corrosion and skin cracking and consequent loss of capability to support limit loads.