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Statement of Need: History has shown that widespread fatigue damage (WFD) is a significant safety risk for transport category airplanes. The Aloha B-737 accident in 1988 showed FAA and industry that WFD could be a problem that could lead to catastrophic failure of airplane structure. Numerous widespread fatigue damage incidents since then have confirmed that it is a threat common to all aging airplanes. Because widespread fatigue damage results from the interaction of many small cracks, existing inspection methods are inadequate to reliably detect and prevent it.

Summary of the Legal Basis: Section 44701, Title 49 of the United States Code states that the Administrator shall promote safety of flight of civil aircraft in air commerce by prescribing minimum standards required in the interest of safety.

Alternatives: The FAA acknowledges the proposed rule may have a significant impact on a substantial number of small entities. We conclude the current proposal is the preferred alternative because it provides for a common WFD system for all operators who fly in the same airspace under the same operating environment. We considered the following alternatives: 1. Exclude small entities 2. Extend the compliance deadline for small entities 3. Establish lesser technical requirements for small entities 4. Expand the requirements to cover more airplanes

Anticipated Costs and Benefits: The cost of this proposal is $358.1 million. The benefits of this proposal consist of $654 million in accident prevention benefits and $74 million in detection benefits, for total benefits of $728 million.

Risks: Because widespread fatigue damage problems will occur as airplanes operate beyond their initial operational limit, operators are likely to detect such problems over the 20-year forecast period. The FAA has assumed that there is a probability of widespread fatigue damage problems occurring for each fuselage type of five percent in each year. Under this assumption, there is a 35 percent chance that there will be zero WFD problems detected for a particular fuselage type over a 20-year period.