AD FAA-2014-0778

We are adopting 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 AD was prompted by reports of skin cracks and subsequent findings of hidden corrosion found on the mating surfaces between certain skin and stringers at circumferential skin splices. This AD requires 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 issuing this AD to detect and correct hidden corrosion due to compromised fillet seals, which can result in skin cracking and consequent loss of capability to support limit loads.