Airworthiness Directives; Boeing Model 747 Series Airplanes Equipped With General Electric Model CF6-45 or -50 Series Engines or Pratt & Whitney Model JT9D-3, -7, or -70 Series Engines; and 747-E4B (Military) Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes equipped with General Electric Model CF6-45 or -50 series engines or Pratt & Whitney Model JT9D-3, -7, or -70 series engines; and all 747-E4B (military) airplanes. That AD currently requires repetitive inspections to detect cracking or fracture of the steel attachment fittings of the diagonal brace to the nacelle struts; and replacement of the attachment fittings with new steel fittings, if necessary. This amendment adds new repetitive inspections of the fasteners of the steel attachment fittings of the diagonal brace to the inboard and outboard nacelle struts to find discrepancies; and mandates certain one-time inspections of the existing attachment fittings, installation of new fasteners, and replacement or rework of the fittings, which terminates the repetitive inspections. This amendment is prompted by a report of fatigue cracking in a steel attachment fitting of the diagonal brace to the number 2 nacelle strut. The actions specified by this AD are intended to prevent such cracking or a fracture, which could result in failure of a nacelle strut diagonal brace load path and possible separation of the nacelle from the wing.