Airworthiness Directives; The Boeing Company Airplanes

The FAA is superseding Airworthiness Directive (AD) 2021-07- 09, which applies to all The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes. AD 2021-07-09 required repetitively inspecting all trim air diffuser ducts or sidewall riser duct assemblies (collectively referred to as TADDs) for damage, including repetitive structural inspections of the center fuel tanks for damage, and performing applicable on-condition actions. Since the FAA issued AD 2021-07-09, the agency has determined that the existing requirements do not adequately address the unsafe condition. This AD continues to require repetitive inspections of the TADDs for damage, with revised compliance times, and repair if applicable. This AD also requires repetitive replacement of the TADDs and removes the structural inspections of the center fuel tanks. This AD also prohibits the installation of affected parts. This AD removes certain airplanes from the applicability. The FAA is issuing this AD to address the unsafe condition on these products.