U.S. Department
of Transportation
Federal Aviation
Administration
Advisory
Circular
Subject: DEVELOPMENT OF
STANDARD WIRING PRACTICES
DOCUMENTATION
Date: 11/14/07
Initiated by: ANM-100
AC No. 25-26
1. PURPOSE. This advisory circular (AC) provides guidance for developing an electrical
system standard wiring practices document for air carriers, air operators, holders of type
certificates (TC), holders of supplemental type certificates (STC), maintenance providers, and
repair stations. This AC provides a means, but not the only means, to create a document that
complies with the requirements of section H25.5(a)(2) of appendix H to Title 14 Code of Federal
Regulations (14 CFR) part 25.
2. APPLICABILITY.
a. The guidance provided in this AC is applicable to all air carriers, air operators, holders of
type certificates, holders of STCs, maintenance providers, and repair stations operating
under 14 CFR parts 21, 25, 43, 91, 121, 125, 135, and 145.
b. This material is neither mandatory nor regulatory in nature and does not constitute a
regulation. It describes an acceptable means, but not the only means, for demonstrating
compliance with the applicable regulations. We 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 we become
aware of circumstances that convince us that following this AC would not result in
compliance with the applicable regulations, we will not be bound by the terms of this AC,
and we may require additional substantiation or design changes as a basis for finding
compliance.
c. This material does not change or create any additional regulatory requirements nor does
it authorize changes in or permit deviations from existing regulatory requirements.
d. Terms used in this AC such as “shall” or “must” are used only in the sense of ensuring
applicability of this particular method of compliance when the acceptable method of
compliance described herein is used.
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