Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to supersede Airworthiness Directive (AD) 2005-13- 05, which applies to certain Boeing Model 747-400F series airplanes. AD 2005-13-05 currently requires 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 requires a preventive modification of the upper deck floor beams, and repetitive inspections for cracking after accomplishing the modification. Since we issued AD 2005-13-05, the upper chords of the upper deck floor beams at certain stations have been determined to be structures that are susceptible to widespread fatigue damage, and certain airplanes with an initial modification require a second modification for the airplane to meet its limit of validity (LOV). This proposed AD would require that second modification and repetitive inspections for cracking and repair if necessary. We are proposing 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.