Emissions Certification Policy and Guidance

Regulated emissions include raw fuel vented to the atmosphere during normal engine shutdown, and the following products of combustion in engine exhaust for certain classes of engines: smoke (SN), hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The International Civil Aviation Organization (ICAO) has most recently adopted a reporting requirement for non-volatile particulate matter (nvPM) emissions from engines and emissions limits for carbon dioxide (CO2) from aircraft.

Review Recommended Best Practices for Quantifying Speciated Organic Gas Emissions From Aircraft Equipped with Turbofan, Turbojet, and Turboprop Engines  and Guidance for Quantifying Speciated Organic Gas Emissions from airport Sources

Which engines do the emissions certification requirements apply to?

The Engine Fuel Venting and Exhaust Emissions certification requirements (14 CFR Part 34) apply to civil airplanes that are powered by aircraft gas turbine engines of the classes specified in the rule. The engines must have U.S. standard airworthiness certificates or foreign airworthiness certificates that are equivalent to U.S. standard airworthiness certificates.

U.S. manufactured gas turbine engines or foreign manufactured gas turbine engines that are installed in U.S. manufactured Part 23 or Part 25 aircraft must show compliance to the 14 CFR Part 34 fuel venting and exhaust emissions requirements.

Who is authorized to set emissions certification requirements?

The Secretary of Transportation is mandated, by authority of Section 232 of the Clean Air Act (CAA), to "prescribe regulations to ensure compliance with all standards prescribed by the Administrator" (of the Environmental Protection Agency).

The EPA, similarly, gets its authority from Section 231 of the CAA that mandates EPA to determine "the extent to which such emissions affect air quality in air quality regions throughout the United States," and "the technological feasibility of controlling such emissions.“

The EPA sets the Emissions Standards and FAA sets and administers the Certification Requirements for aircraft and engines to demonstrate compliance with the Emissions Standards. In addition, Section 233 of the CAA prohibits states and local communities from setting their own standards.

What is the basis of these requirements?

The standards, as developed by EPA are issued in Title 40 Part 87 of the Code of Federal Regulations (40CFR87), "Control of air pollution from aircraft and aircraft engines." The requirements as developed by FAA in association with EPA are issued in Title 14 Part 34 of the Code of Federal Regulations (14CFR34), "Fuel Venting and Exhaust Emission Requirements for Turbine Engine Powered Airplanes.“

Independently, the International Civil Aviation Organization (ICAO) issued, as one of their International Standards and Recommendation Practices, Annex 16 to the Convention on International Civil Aviation, Environmental Protection, Volume II, Aircraft Engine Emissions and ICAO Annex 16, Volume III CO2 emissions. The EPA has adopted, by reference in 40CFR87 selected sections of Annex 16 that describe requirements for sampling, measurement and the analytical determination of compliance. These requirements are reflected in 14CFR34 in sections 34.64, "Sampling and analytical procedures for measuring gaseous exhaust emissions;" 34.82, "Sampling and analytical procedures for measuring smoke exhaust emissions;" and sections34.71, "Compliance with gaseous emissions standards," and 34.89, "Compliance with smoke emissions standards.“

The regulations are complex and offer challenges in arriving at and maintaining uniformity of interpretation and application by engine manufacturers and regulatory authorities. To address this problem, FAA has issued an Advisory Circular, AC34-1B, "Fuel Venting and Exhaust Emissions Requirements for Turbine Engine Powered Airplanes."  ICAO subsequently developed an equivalent Environmental Technical Manual, "Volume II Procedures for the Emissions Certification of Aircraft Engines.“

What is the basis of fuel venting and exhaust emissions requirements?

The Clean Air Act (CAA) of 1970 directs EPA to establish air pollution standards, including those applicable to aircraft exhaust. Under Sections 231 and 232 of the CAA, EPA consults with FAA to ensure that the development and application of requisite technology is possible. The FAA issues regulations under 14 CFR Part 34 to enforce compliance with EPA emissions regulations under 40 CFR Part 87.

Which FAA organization is responsible for maintaining emissions certification requirements?

AEE-300 has responsibility for maintaining the fuel venting, exhaust and aircraft emissions standards of 14 CFR Part 34, as well as approving new or equivalent test procedures under 14 CFR Part 34, and processing applications for exemptions per 14 CFR Part 11. In addition, AEE-300 provides policy and guidance relative to this rule and promotes international harmonization of emissions standards through ICAO's Committee for Aviation Environmental Protection. AEE-300 also coordinates with EPA on aviation emissions standards codified in 40 CFR Part 87. Finally, AEE-300 provides policy and guidance via Advisory Circular AC-34. 

Last updated: Thursday, August 31, 2023