Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires inspections of the lower engine mount to determine if the tangential link upper bolt and nut are oriented properly, and if the tangential link upper bolt nut is torqued within certain limits. Additionally, that AD requires replacement of the bolt and nut with serviceable parts, if necessary, and requires certain follow-on actions for airplanes on which the upper bolt is missing. That AD also provides for replacement of the safety links with modified links as an optional terminating action for the repetitive inspections. This action would require accomplishment of either the previously optional terminating action or a new, alternative terminating action. This proposal is prompted by development of a new terminating action by the manufacturer. The actions specified by the proposed AD are intended to prevent separation of the engine from the airplane due to migration of the tangential link upper bolt.