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 a one-time inspection to detect cracking and corrosion of various areas at all four nacelle struts; and repair, if necessary. This amendment requires new repetitive inspections to detect fatigue cracking or loose or missing fasteners of the aft torque bulkheads of the outboard nacelle struts; and repair, if necessary. In addition, this action expands the applicability of the existing AD to include additional airplanes. This amendment is prompted by a report indicating that cracking was found in the aft torque bulkheads of the outboard nacelle struts, and by the availability of new service instructions for detecting fatigue cracking that would not have been detected by the required actions of the existing AD. The actions specified in this AD are intended to detect and correct such fatigue cracking and loose or missing fasteners, which could result in failure of an outboard nacelle strut diagonal brace load path and possible separation of the nacelle from the wing.