Airworthiness Directives; Boeing Model 747-400 Series Airplanes Powered by Pratt & Whitney PW4000 Engines

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-400 series airplanes, that requires repetitive inspections to ensure proper installation of the engine thrust link components, and follow-on corrective action, if necessary; and replacement of the forward engine mount end cap assembly with an improved end cap assembly. Such replacement, when accomplished, will terminate the repetitive inspections. This amendment is prompted by a report of fatigue cracking of end cap bolts, caused by improper installation. Subsequent investigation revealed that properly installed end caps also are subject to early fatigue cracking. The actions specified by this AD are intended to prevent failure of the end cap assembly, which could lead to separation of the engine from the airplane in the event of a primary thrust linkage failure.