Provides guidance for complying with Part 21 of Subchapter C, Chapter 1, Title 14 of the Code of Federal Regulations (CFR), which contains the certification procedures for products and parts.

We, the Federal Aviation Administration (FAA), wrote this advisory circular (AC) to describe how to comply with the requirements of Title 14 of the Code of Federal Regulations (14 CFR) 21.20, 21.97 and 21.303(a)(5).
This AC is not mandatory and is not a regulation.

Describes what you, as an installer, must show in a data package that is presented to the Federal Aviation Administration (FAA) through either a technical standard order authorization (TSOA) or TSO letter of design approval (LODA), under the provisions of Title 14 of the Code of Federal Regulations (14 CFR) part 21. This AC does not address aircraft repairs or alterations involving TSO articles under the provisions of 14 CFR part 43, nor does it address alterations to TSOA articles by repair stations under 14 CFR part 43.

This advisory circular (AC) provides information and guidance concerning special airworthiness certification in the experimental category of certain former military aircraft under Title 14 of the Code of Federal Regulations (14 CFR) part 21, Certification Procedures for Products and Parts, §§ 21.191(a), (c), (d), (e); and 21.193.

This advisory circular (AC) provides information for production approval holders (PAH) pursuant to Title 14 of the Code of Federal Regulations (14 CFR) part 21, Certification Procedures for Products and Articles. This AC provides PAHs and applicants for a production approval with guidance for developing and maintaining a production system that is appropriate to the PAH’s operations and complies with the regulations.

This AC does not apply to the articles that are listed in 14 CFR 21.9(a)(1) through (6).

b. This AC refers to parts and components as articles per 14 CFR 21.1.

Provides information, clarification, and procedural guidance concerning the Inactivation of MIL-S-8879Cm Screw Threads, Controlled Radius Root with Increased Minor Diameter, as it relates to the civil aviation industry.

Provides a means but not the only means for the type, production, and airworthiness certification of very light airplanes (VLA); and designates the “Joint Aviation Requirements for Very Light Aeroplanes” (JAR-VLA), issued April 25, 1990, by the Joint Aviation Authorities (FAA) of Europe as an acceptable airworthiness criteria that provides in equivalent level of safety under FAR 21.17(b) for Federal Aviation Administration (FAA) type certification of VLA as a special class of aircraft.

AC 21-48 describes an acceptable means for using electronic modeling systems in design, manufacturing, installation, and inspection processes.