Summary
We propose to supersede Airworthiness Directive (AD) 2004-13- 02, which applies to certain The Boeing Company Model 747-100, -200B, and -200F series airplanes. AD 2004-13-02 currently requires initial and repetitive inspections to find discrepancies in the upper and lower skins of the fuselage lap joints, and repair if necessary. Since we issued AD 2004-13-02, an evaluation by the design approval holder (DAH) indicates that the longitudinal lap joints are subject to widespread fatigue damage (WFD), and that a structural modification at the lap joint, and post-modification repetitive inspections of the skin, existing internal doubler, or splice strap for cracks, and corrective actions if necessary, are required to reach the limit of validity (LOV). This proposed AD would add post-repair inspections for cracking and corrosion, and repair if necessary; structural modification at the lap joints; and post-modification inspections for cracking and corrosion, and repair if necessary.We are proposing this AD to detect and correct fatigue cracking in the upper and lower skins of the fuselage lap joints, which could result in sudden fracture and failure of a lap joint and rapid in-flight decompression of the airplane fuselage.