Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 747SP series airplanes, that would have superseded an existing AD to require inspections to detect cracks in the web of the wing front spar, and modification, if necessary. That proposal was prompted by a report of cracking in the web in an area outside the inspection zone specified in the existing AD. A crack in the web that is not detected before it extends outside the chord footprints can allow fuel leakage. This action revises the proposed rule by reducing the compliance time for inspections of certain airplanes. The actions specified by this proposed AD are intended to prevent fuel leakage onto an engine and a resultant fire due to cracking in the web of the wing front spar.