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 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 amendment 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. This amendment requires accomplishment of a previously optional terminating action or a new alternative terminating action for the repetitive inspections. This amendment is prompted by development of a new terminating action by the manufacturer. The actions specified by this AD are intended to prevent separation of the engine from the airplane due to migration of the tangential link upper bolt.