Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 707 and 720 series airplanes, that would have superseded an existing AD to require repetitive inspections to detect cracks in certain areas of the upper forward skin panels of the wing center section, and repair, if necessary. That AD also would have provided an optional terminating modification for the repetitive inspections. That proposal was prompted by reports that the inspections required by the existing AD are not effective in detecting fatigue cracks in a timely manner. This action revises the proposed rule by reducing certain compliance times and by revising the applicability statement of the AD. The actions specified by this proposed AD are intended to prevent fatigue cracking and subsequent failure of the upper forward skin panels of the wing center section.