Summary
This document proposes to revise an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections to detect cracks, corrosion, or damage of the lower spar fitting body and lug, and corrective actions, if necessary. That AD also provides for optional terminating action for the repetitive inspection requirements. The existing AD was prompted by reports that fatigue cracking was found in the lower spar fitting lug on the number 3 pylon and in the lower spar fitting body. The actions specified by that AD are intended to detect and correct such fatigue cracking, which could result in failure of the strut and separation of the engine from the airplane. This new action references additional service bulletins for accomplishment of the optional replacement, and clarifies that accomplishment of certain AD's terminates the repetitive inspections.