Action
Final rule.
Summary
We are superseding Airworthiness Directive (AD) 2010-03-05 for all the Boeing Company Model 747-200C and -200F series airplanes. AD 2010-03-05 required, for the upper chords of the upper deck floor beam of section 41, an inspection for cracking of certain fastener holes, and corrective action if necessary; and repetitive replacements of the upper chords, straps (or angles), and radius fillers of certain upper deck floor beams and, for any replacement that is done, inspections for cracking, and corrective actions if necessary. This new AD adds repetitive inspections of the upper chords of the upper deck floor beam of Section 42, repetitive replacements of the upper chords, post- replacement inspections, and corrective actions if necessary. This new AD also adds post-replacement inspections for section 41 and reduces certain compliance times. This AD was prompted by a determination that the upper deck floor beams are subject to widespread fatigue damage (WFD), the existing inspection program is not sufficient to maintain an acceptable level of safety, and the upper chords of the upper deck floor beam of section 42 are subject to the unsafe condition. We are issuing this AD to detect and correct cracking of the upper chords and straps (or angles) of the floor beams, which could lead to failure of the floor beams and consequent loss of controllability, rapid decompression, and loss of structural integrity of the airplane.