Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-200C, 747-300, 747-400, 747-400D, 747-400F, and 747SR Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires inspections for cracking of the forward end clevis lugs of the flap track, and replacement of the flap track with a new flap track if necessary. That AD also currently provides for an optional modification of the forward end clevis lugs, which terminates the required inspections. This amendment expands the applicability of the existing AD, and requires new repetitive inspections for evidence of rotation or migration of the bushings or cracking of the lugs of the forward end clevis of the flap tracks that support the wing trailing edge flaps, corrective actions if necessary, and eventual accomplishment of a terminating action. These actions are necessary to prevent cracking and fracture of the forward end clevis of the flap track, which could result in reduced structural capability of the flap and reduced controllability of the airplane. This action is intended to address the identified unsafe condition.