Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires inspection of the flap tracks of the wing trailing edge flaps for adequate cadmium plating and for corrosion of certain bolt holes of the fail-safe bar, and plating of such holes, if necessary. This amendment also requires post-modification inspections of certain bolt holes of the fail-safe bar of the flap tracks of the wing trailing edge flaps for discrepancies, and corrective actions, if necessary. This amendment is prompted by reports of corrosion and cracks found in certain bolt holes reworked according to the existing AD. The actions specified by this AD are intended to find and fix discrepancies of the bolt holes, which could result in fracture of the flap track, separation of the flap, and consequent loss of control of the airplane. This action is intended to address the identified unsafe condition.