Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP Series Airplanes Equipped with General Electric CF6-45 or -50 Series Engines, or Equipped with Pratt & Whitney JT9D-3 or -7 (Excluding -70) Series Engines

The FAA is superseding an existing airworthiness directive (AD) that applies to certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes. The existing AD currently requires repetitive inspections to detect cracks and fractures of the strut front spar chord assembly at each strut location, and repair if necessary. This new AD expands the inspection area by requiring repetitive inspections for any cracks or fracture of the strut front spar chord assembly in an area forward of the existing inspection area at each strut location, and repair if necessary. This AD results from a strut front spar chord assembly that was found fractured, forward of the inspection area required by the existing AD. We are issuing this AD to detect and correct cracks and fracture of the nacelle strut front spar chord assembly. Fracture of the front spar chord assembly could lead to loss of the strut upper link load path and consequent fracture of the diagonal brace, which could result in in-flight separation of the strut and engine from the airplane.