Skip to page content

USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Site Notification

Site Notification

United States Department of TransportationUnited States Department of Transportation

Aircraft Certification Service (AIR)
Draft Advisory Circulars (ACs) Open for Comment

Document Title: AC 20-29C, Approval and Use of Fuel System Icing Inhibitors (FSII)
Summary: This advisory circular (AC) describes an acceptable method to demonstrate compliance with Title 14, Code of Federal Regulations (14 CFR) 23.2620(a)(1), 25.1583(b)(1), 27.1583(b)(1), 29.1583(b)(1), 33.7(b)(2), and 33.7(c)(2) regarding the requirements for the approval and use of Fuel System Icing Inhibitors (FSII) in engines and aircraft. Additional guidance on specifications and standards applicable to FSII is also provided.
Documents for Download: Draft Document
Draft Document Comment Grid
Reference: Title 14, Code of Federal Regulations (14 CFR) 23.2620(a)(1), 25.1583(b)(1), 27.1583(b)(1), 29.1583(b)(1), 33.7(b)(2), and 33.7(c)(2)
Comments Due: July 1, 2022
How to Comment: Email comments to:
Jeffery.Finley@faa.gov

Deliver comments by mail or hand to:
Federal Aviation Administration
Policy and Innovation Division, System and Equipment Standards Branch, AIR-6B0
950 L'Enfant Plaza SW, Suite 500
Washington, DC 20024

Fax comments to:
781-238-7199
Document Title: AC 25.562-2B Change 2, Dynamic Evaluation of Seat Restraint Systems and Occupant Protection on Transport Airplanes
Summary: This change updates methods of compliance for front-row seats under paragraph 5e(5)(d) and Appendix 4, based on studies of forward‑facing seats with conventional lap and Y‑belt restraints. Additionally, it updates Section 13, Pass/Fail Criteria, paragraph 13.a.(2)b, for purposes of eliminating neck injuries associated with occupant interaction with interior features, and provides additional guidance for seat designs for which dynamic testing shows obvious and unacceptable injurious interactions of the head and neck.
Documents for Download: Draft Document
Draft Document Comment Grid
Reference: 14 CFR 25.562 and 25.785
Comments Due: July 18, 2022
How to Comment: Email comments to:
Tracy.r.szczepaniak@faa.gov

Deliver comments by mail or hand to:
Federal Aviation Administration
Policy and Innovation Division, Strategic Policy Management Branch, AIR-612
950 L'Enfant Plaza SW, Suite 500
Washington, DC 20024

Fax comments to:
202-267-1813 
Document Title: Turbine Engine Inlet Sensor Ice Crystal and Mixed Phase Icing Compliance
Summary: This advisory circular (AC) describes an acceptable method for demonstrating compliance with Title 14, Code of Federal Regulations (14 CFR) 33.28, 33.68, 33.89 and 33.91, regarding mixed phase and ice crystal icing (ICI) with respect to engine inlet sensors.  This AC may also be useful when demonstrating compliance with 14 CFR 25.901(c), 25.1093(b), 25.1309, 25.1323, 25.1324, and 25.1325 regarding ICI with respect to engine inlet sensors on turbine-powered airplanes.  This AC addresses temperature probes, combined temperature and pressure probes, and static pressure probes used by turbine engines.  Manufacturers can use this method of compliance to evaluate probe behavior in mixed phase and ICI conditions and the resulting impact of engine probe performance on engines and airframe systems.  In addition, this methodology is flexible enough to evaluate temperature probe, combined pressure/temperature probe, and static pressure probe behavior regardless of installation location.
Documents for Download: Draft Document
Draft Document Comment Grid
Reference: Title 14, Code of Federal Regulations (14 CFR) 33.28, 33.68, 33.89 and 33.91
Comments Due: July 29, 2022
How to Comment: Email comments to:
Jeffery.Finley@faa.gov

Deliver comments by mail or hand to:
Federal Aviation Administration
Policy and Innovation Division, System and Equipment Standards Branch, AIR-6B0
950 L'Enfant Plaza SW, Suite 500
Washington, DC 20024
Document Title: Engine Fuel Systems
Summary: This advisory circular (AC) provides guidance for demonstrating compliance with the requirements of Title 14, Code of Federal Regulations (14 CFR) Section 33.67, Fuel system. This AC addresses turbine aircraft engine compliance methods, failure modes, Section 33.67 lessons learned, and references to associated aircraft-level guidance. It does not address aircraft-level fuel system icing effects or compliance.
Documents for Download: Draft Document
Draft Document Comment Grid
Reference: Title 14, Code of Federal Regulations (14 CFR) Section 33.67
Comments Due: August 5, 2022
How to Comment: Email comments to:
Jeffery.Finley@faa.gov

Deliver comments by mail or hand to:
Federal Aviation Administration
Policy and Innovation Division, System and Equipment Standards Branch, AIR-6B0
950 L'Enfant Plaza SW, Suite 500
Washington, DC 20024

Page last modified: