Action
Notice of proposed rulemaking (NPRM).
Summary
The FAA proposes to supersede 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 requires 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 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 proposed AD would continue to require repetitive inspections of the TADDs for damage with revised compliance times, and repair if applicable. This proposed AD would also require repetitive replacement of the TADDs and would remove the structural inspections of the center fuel tanks. This proposed AD would also prohibit the installation of affected parts. The FAA is proposing this AD to address the unsafe condition on these products.