Action
Final rule.
Summary
We are superseding Airworthiness Directive (AD) 2005-13-05, which applied to certain Boeing Model 747-400F series airplanes. AD 2005-13-05 required inspections for cracking of the web, upper chord, and upper chord strap of the upper deck floor beams, and repair of any cracking. AD 2005-13-05 also required a preventive modification of the upper deck floor beams, and repetitive inspections for cracking after accomplishing the modification. This new AD retains these actions and requires a second modification, repetitive inspections for cracking, and repair if necessary. This AD was prompted by a determination that the upper chords of the upper deck floor beams at certain stations are structures that are susceptible to widespread fatigue damage, and that certain airplanes with an initial modification require a second modification for the airplane to meet its limit of validity (LOV). We are issuing this AD to detect and correct fatigue cracking in certain upper chords of the upper deck floor beam, which could result in reduced structural integrity of the airplane and rapid decompression or reduced controllability of the airplane.