Airworthiness Directive · Amendment 39-12756 · Boeing Model 747 Series Airplanes
Boeing Model 747 Series Airplanes
Superseded. A later AD replaced this one: AD 2005-20-30. Comply with the one in force.
Model 747 series airplanes, as listed in Boeing Service Bulletin 747-53-2349, dated June 27, 1991, or Boeing Alert Service Bulletin 747-53A2349, Revision 1, dated October 12, 2000; certificated in any category.
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair, if necessary. This amendment adds new repetitive inspections for cracking of certain areas of the upper chord of the upper deck floor beams, and repair, if necessary. This amendment is prompted by the results of fatigue testing that revealed severed upper chords of the upper deck floor beams due to fatigue cracking. The actions specified by this AD are intended to prevent loss of the structural integrity of the fuselage, which could result in rapid depressurization of the airplane.
