Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes. This action 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. This action also 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. Terminating action is also provided by this AD. This amendment is prompted by reports of migration of bolts completely from the tangential link of the aft engine mount, a condition which would reduce the capability of the retention system for the engine. The actions specified in this AD are intended to prevent separation of the engine from the airplane due to migration of the tangential link upper bolt.