AD 2021-24-12 Prompted By Significant Changes, Including New Or More Restrictive Requirements...

The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company Model 777 airplanes.

 This AD was prompted by significant changes, including new or more restrictive requirements, made to the airworthiness limitations (AWLs) and Critical Design Configuration Control Limitations (CDCCLs) related to fuel tank ignition prevention, the engine fuel suction feed system, and the nitrogen generation system. This AD requires revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective February 1, 2022.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain The Boeing Company Model 777 airplanes. The NPRM published in the Federal Register on March 26, 2021 (86 FR 16133). The NPRM was prompted by significant changes, including new or more restrictive requirements, made to the AWLs and CDCCLs related to fuel tank ignition prevention, the engine fuel suction feed system, and the nitrogen generation system.

In the NPRM, the FAA proposed to require revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. The FAA is issuing this AD to address ignition sources inside the fuel tanks and the increased flammability exposure of the center fuel tank caused by latent failures, alterations, repairs, or maintenance actions, which could result in a fuel tank explosion and consequent loss of an airplane; and to address potential loss of engine fuel suction feed capability, which could result in dual engine flameouts, inability to restart engines, and consequent forced landing of the airplane.

FMI: www.regulations.gov