Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that would have required a one-time inspection to determine whether H-11 steel bolts are installed as attach and support bolts at the trailing edge flap transmissions, and replacement of any H-11 steel bolt with an Inconel bolt. That proposal was prompted by reports of fracturing or cracking of H-11 steel bolts at the flap transmissions. This new action revises the proposed rule by expanding the applicability to include additional airplanes. The actions specified by this new proposed AD are intended to prevent loss of a flap transmission, which could reduce lateral controllability of the airplane.