Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes. That AD currently requires inspections to detect fatigue cracking of the vertical beam webs and chords of the nose wheel well (NWW) and of the inner chord and web of the fuselage frames at body station (BS) 300 and BS 320, and repair, if necessary. This action would expand the applicability of the existing AD to include additional airplanes, and add new requirements for repetitive inspections to detect fatigue cracking of the NWW vertical beam webs and frames from BS 260 to BS 320, and follow-on actions, if necessary, which would end the currently required inspections for airplanes subject to them. This action also provides terminating action for the new repetitive inspections. The actions specified by the proposed AD are intended to detect and correct fatigue cracking of the NWW vertical beam webs and frames, which could result in collapse of the NWW pressure bulkhead and subsequent rapid decompression of the airplane.