Advisory
Circular
Subject: Damage Tolerance
and Fatigue Evaluation of Structure
Date: 1/13/2011
Initiated By: ANM-115
AC No: 25.571-1D
1. Purpose.
a. This advisory circular (AC) provides guidance for compliance with the provisions of
Title 14, Code of Federal Regulations (14 CFR) part 25, pertaining to the requirements for
damage-tolerance and fatigue evaluation of transport category aircraft structure, including
evaluation of widespread fatigue damage (WFD) and establishing a limit of validity of the
engineering data that supports the structural-maintenance program (hereafter referred to as the
LOV). This AC also includes guidance pertaining to discrete source damage.
b. The following appendices appear at the end of this AC:
● Appendix 1 – References and Definitions
● Appendix 2 – Full-Scale Fatigue Testing
● Appendix 3 – Process for Compliance with 14 CFR 25.571(a), (b) and (c) for
Fatigue Damage
● Appendix 4 – Examples of Alterations that May Require Full-Scale Fatigue Testing
● Appendix 5 – PSE, FCS and WFD-Susceptible Structure
● Appendix 6 – Acronyms and Abbreviations Used in this AC
2. Applicability.
a. The guidance provided in this document is directed to airplane manufacturers,
modifiers, foreign civil-aviation authorities, and Federal Aviation Administration (FAA)
transport airplane type certification engineers and designees.
b. This material is neither mandatory nor regulatory in nature and does not constitute a
regulation. It describes acceptable means, but not the only means, for demonstrating compliance
with the applicable regulations. The FAA will consider other methods of demonstrating
compliance that an applicant may elect to present. While these guidelines are not mandatory,
they are derived from extensive FAA and industry experience in determining compliance with
the relevant regulations. On the other hand, if the FAA becomes aware of circumstances that
convince us that following this AC would not result in compliance with the applicable
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