Airworthiness Directive · Amendment 39-9868 · Boeing Model 747 Series Airplanes
Boeing Model 747 Series Airplanes
Model 747 series airplanes having line numbers 1 through 1046, inclusive; certificated in any category; that meet all of the following criteria: equipped with Pratt & Whitney Model PW4000 series engines, or General Electric Model CF6-80C2 series engines, or Rolls Royce Model RB211 series engines; on which fuse pins having part numbers 310U2301-101, - 116, -117, or -120 ("third generation" fuse pins) are installed at the midspar/spring beam fittings of the engine pylon; and on which the modification of the nacelle strut and wing structure in accordance with Boeing Alert Service Bulletin 747- 54A2156 or Boeing Alert Service Bulletin 747-54A2157, as applicable, has not been accomplished.
This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) T96-26-52 that was sent previously to all known U.S. owners and operators of Boeing Model 747 series airplanes by individual telegrams. This AD requires repetitive inspections of the access doors to the midspar/spring beam fuse pins on all engine pylons to detect cracks on the external surface; repetitive inspections of each midspar/spring beam fuse pin to detect if it protrudes beyond its mating nut by a specified distance; and repair of any discrepancy found. This action is prompted by a report indicating that a fuse pin had migrated on an inboard spring beam fitting on the Number 1 engine pylon of a Boeing Model 747-400 airplane. The actions specified by this AD are intended to prevent migration of this fuse pin, which, if not detected and corrected in a timely manner, could result in failure of the engine pylon and consequent separation of the engine from the wing.
