Advisory circular explained

Advisory circular (AC) refers to a type of publication offered by the Federal Aviation Administration (FAA) to "provide a single, uniform, agency-wide system … to deliver advisory (non-regulatory) material to the aviation community."^[1] Advisory circulars are now harmonized with soft law Acceptable Means of Compliance (AMC) publications of EASA, which are nearly identical in content. The FAA's Advisory Circular System is defined in FAA Order 1320.46D.^[2]

By writing advisory circulars, the FAA can provide guidance for compliance with airworthiness regulations, pilot certifications, operational standards, training standards, and any other rules within the 14 CFR Aeronautics and Space title, aka 14 CRF or FARs. The FAA also uses advisory circulars to officially recognize "acceptable means, but not the only means," of accomplishing or showing compliance with airworthiness regulations.^{[3] [4]} Advisory circulars may also contain explanations, clarifications, best practices, or other information of use to the aviation community.^{[2] [5]}

Usage

Advisory circulars can recognize industry standards from SAE (ARP), RTCA (DO), and others.^[6] With harmonization of technical content and guidance between EASA and the FAA, later advisory circulars also identify corresponding EUROCAE (ED) publications.^[7]

Some advisory circulars are only a few pages long and do little more than reference a recommended standard; for example, AC 20-152 referencing DO-254.^[8] Others, like AC 20-115C/D, are considerably longer; in this case including guidance on how to transition from DO-178 revision B to C^[9] while AC 20-152A adds several new objectives to an otherwise unchanged DO-254.

Relation to regulations

Generally informative in nature, Advisory Circulars are neither binding nor regulatory; yet some have the effect of de facto standards or regulations.^[10] The FAA establishes regulation of U.S. civil airspace through issuance of Federal Aviation Regulations (FAR). Issuing or amending FARs requires a potentially lengthy period of public commentary and agency reflection on proposed rule making before they may be issued for enforcement. In practice, advisory circulars have essential roles for public compliance with the regulations. The FAA relies on the advisory circular system to

• "Provide an acceptable, clearly understood method for complying with a regulation"
• "Standardize implementation of a regulation or harmonize implementation for the international aviation community"
• "Resolve a general misunderstanding of a regulation"
• "Help the industry and FAA effectively implement a regulation"^[11]

In contrast with the lengthy processes of FARs, advisory circulars may be published with little or no advanced notice or distribution. A concern is that the content of advisory circulars should not have the effect of de facto amendments to regulations.^[12] In general, the FAA may not "use an AC to add, reduce, or change a regulatory requirement."^[13]

Examples of Published Advisory Circulars! Advisory Circular !! Title !! Referenced Standards

AC 00-69	Best Practices for Airborne Software Development Assurance Using and
AC 00-71	Best Practices for Management of Open Problem Reports (OPRs)
AC 00-72	Best Practices for Airborne Electronic Hardware Design Assurance Using and
AC 20-115	Airborne Software Development Assurance Using and	ED-12C/DO-178C ED-215/DO-330 ED-218/DO-331 ED-217/DO-332 ED-216/DO-333
AC 20-136	Aircraft Electrical and Electronic System Lightning Protection	RTCA DO-160 §22
AC 20-148	Reusable Software Components
AC 20-152A	Design Assurance Guidance for Airborne Electronic Hardware	RTCA DO-254
AC 20-170	Integrated Modular Avionics Development. Verification, Integration and Approval	RTCA DO-297
AC 20-189	Management of Open Problem Reports (OPRs)
AC 20-1317	The Certification of Aircraft Electrical and Electronic Systems for Operation in the High Radiated Fields (HIRF) Environment
AC 25.1309-1	System Design and Analysis	ARP4754, ARP4761
AC 20-174	Development of Civil Aircraft and Systems	ARP4754A
AC 43.13-1B	Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair
AC 70-1	Outdoor Laser Operations
AC 91-57B	Exception for Limited Recreational Operations of Unmanned Aircraft (relevant to Regulation of UAVs in the United States)
AC 107-2	Small Unmanned Aircraft Systems (sUAS) (contains 14 CFR part 107 guidance).	49 U.S.C. § 44809

See also

• Airworthiness Directive (in comparison, airworthiness directives are legally enforceable rules)

Notes and References

1. Web site: Advisory Circular . CFI Notebook . Certified Flight Instructor's Notebook . Advisory Circulars (ACs) provide a single, uniform, agency-wide system that the FAA uses to deliver advisory (non-regulatory) material to the aviation community . 2024-04-20 .
2. Order 1320.46D Advisory Circular System . 2015-04-07 . 2024-04-20 . FAA Order . .
3. Book: Developing Safety-Critical Software: A Practical Guide for Aviation Software and DO-178C Compliance . Leanna Rierson . 9781351834056 . 7 January 2013 . 19 December 2017 . 2024-04-10 . . 49 . The recognition typically comes in the form of an Advisory Circular (AC) for the FAA and equivalent advisory materials by other certification authorities. .
4. David B. Walen FAA, Civil Aircraft System Safety and Electromagnetic Compatibility, November 16, 2010, p. 6. "Compliance with Regulations: FAA Guidance for compliance with airworthiness regulations published within Advisory Circulars (ACs) | Define acceptable, but not the only, means to comply with the airworthiness regulations | For example, AC 25.1309-1A describes acceptable means for showing compliance with 14 CFR 25.1309"
5. Hartman v. United States . . Feb 8, 2013 . https://casetext.com/case/hartman-v-united-states-11 . 10. ACs are “advisory” only. ACs provide guidance such as methods, procedures, and practices acceptable to the FAA for complying with regulations and grant requirements. ACs may also contain explanations of regulations, other guidance material, best practices, or information useful to the aviation community. They do not create or change a regulatory requirement. An AC may reflect or restate ways to implement regulatory requirements otherwise established by statute, regulation or grant agreements, but, by FAA order, an AC itself may not impose requirements or prohibitions. (Deemed admitted by the court for the reasons discussed below.) . 2024-04-20 . Note: This is verbatim from FAA Order 1320.46D.
6. Book: Developing Safety-Critical Software: A Practical Guide for Aviation Software and DO-178C Compliance . Leanna Rierson . 9781351834056 . 7 January 2013 . 19 December 2017 . 2022-03-03 . . 49 . The recognition typically comes in the form of an Advisory Circular (AC) for the FAA and equivalent advisory materials by other certification authorities. .
7. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-115D.pdf AC 20-115D
8. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-152.pdf AC 20-152
9. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-115D.pdf AC 20-115D
10. https://archive.org/details/sim_approach_1985-09_31_3/page/24/mode/2up Approach
11. FAA Order 1320.46D, p. 3-1
12. De Facto Amendment of a FAA Amendment of a FAA Regulation by Non-Regulatory Interpretation: Unintended Consequences of FAA Suggestions on How to Comply With the Flight Review Requirement . . Micjael L. Shakman . 2017 . 82 . 2 . ... that purports to explain how to comply with an important regulation in ways that go far beyond the language and intent of the regulation. The result is a de facto amendment without the accompanying safeguards of public comment or consideration of unforeseen but significant consequences for the effected aviation community participants. .
13. FAA Order 1320.46D, p. 3-5