Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes. This proposal would require repetitive inspections of the outboard nacelle struts to detect fatigue cracking of the strut skin and spring beam support fittings, and to detect cracked or loose fasteners of the support fittings; and corrective actions, if necessary. This proposal also provides for optional terminating action for the repetitive inspection requirements. This proposal is prompted by reports indicating that several cracked or broken spring beam support fittings were found on the outboard nacelle struts. The actions specified by the proposed AD are intended to detect and correct such fatigue cracking and loose fasteners, which could result in failure of the outboard nacelle struts and consequent separation of the engine.