Airworthiness Directives; The Boeing Company Model 747-200C, -200F, -400, -400D, and -400F Series Airplanes

摘要

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Model 747-200C, -200F, -400, -400D, and -400F series airplanes. That AD currently requires repetitive inspections for cracks in the overlapping (upper) skin of the upper fastener row of the lap joints of the fuselage skin in sections 41, 42, and 46; and related investigative and corrective actions, if necessary. This new AD expands the inspection area in the existing AD, and adds a modification of certain lap joints and certain post-repair inspections of the lap joints. Accomplishing the modification would end the repetitive inspections required by the existing AD for the length of lap joint that is modified. This AD results from a structural review of affected skin lap joints for widespread fatigue damage. We are issuing this AD to prevent fatigue cracking in certain lap joints, which could result in rapid depressurization of the airplane.