Summary
We propose to supersede an existing airworthiness directive (AD) that applies to certain The Boeing Company Model 747 series airplanes. The existing AD currently requires repetitive detailed inspections to detect cracking in certain fuselage upper deck tension ties, repair or modification of any cracked tension ties, and repetitive inspections of repaired and modified tension ties and repair or modification if necessary. The existing AD also provides for optional terminating action for the repetitive detailed inspections of tension ties that have not been repaired or modified. This proposed AD was prompted by an evaluation by the design approval holder indicating that the upper deck tension ties of the fuselage are subject to widespread fatigue damage. This proposed AD would retain the repetitive inspections, mandate the previously optional terminating modification, and add, for tension ties that have not been repaired or modified, repetitive inspections that must be done concurrently with the existing repetitive inspections. We are proposing this AD to prevent widespread fatigue damage of certain fuselage upper deck tension ties, which could result in reduced structural integrity of the airplane.