Fatigue Evaluation of Structure

This action amends the fatigue requirements for damage- tolerant structure on transport category airplanes to require a demonstration using sufficient full-scale fatigue test evidence that widespread multiple-site damage will not occur within the design service goal of the airplane; and inspection thresholds for certain types of structure based on crack growth from likely initial defects. This change is needed to ensure the continued airworthiness of structures designed to the current damage tolerance requirements, and to ensure that should serious fatigue damage occur within the design service goal of the airplane, the remaining structure can withstand loads that are likely to occur, without failure, until the damage is detected and repaired.