Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to all Boeing Model 707 and 720 series airplanes, that currently requires inspections of the upper and lower chords of the wing front and rear spars, repair if necessary, and application of corrosion inhibitor to the inspected areas. This action would remove the requirements of the existing AD, require new detailed inspections and new high frequency eddy current (HFEC) inspections for corrosion and cracking, and require certain related follow-on and investigative actions, if necessary. This action also would expand the area of inspection to include the dry bay areas. The actions specified by the proposed AD are intended to find and fix corrosion and stress corrosion cracking of the upper and lower chords on the wing front and rear spars, which could result in reduced structural integrity of the wing. This action is intended to address the identified unsafe condition.