FAA Adopts New Aircraft Engine Emission Standards for Non-Volatile Particulate Matter

May 2, 2024

The Federal Aviation Administration (FAA) adopted a new rule that will set a limit on carbon particles emitted by subsonic aircraft engines, according to an April 26 press release.

The rule sets maximum standards for the amount of non-volatile particulate matter (nvPM) emissions from U.S. civil aircraft engines. It aligns with Environmental Protection Agency (EPA) recommendations and International Civil Aviation Organization (ICAO) standards.

Ultrafine carbon particles that aircraft engines produce are an inhalation concern for humans. Also, nvPM emissions can become the nucleus for persistent contrails, meaning that the line-shaped clouds behind some jet engines expand into broader cloudiness that may affect the planet.

"This first-of-its-kind rule in the United States will reduce the environmental impact of civil aviation on our health and climate,” said Laurence Wildgoose, Assistant Administrator for the FAA’s Office of Policy, International Affairs and Environment.

Aircraft engine exhaust is comprised of gaseous compounds, and of particulate matter that contributes to both visible plume exhaust and atmospheric particulate matter. Particulate matter emissions include both volatile and non-volatile components. NvPM is emitted directly from the engine and is comprised of a small amount of carbon particles (or “soot”) that did not fully convert to the gaseous form of carbon dioxide (CO2) during the combustion process.

Volatile particulate matter (vPM) condenses and agglomerates in the aircraft exhaust plume or where the gaseous emissions from the plume react with ambient chemicals present in the atmosphere. Since vPM are affected by atmospheric conditions and undergo rapid changes when emitted, they are difficult to predict or measure accurately. This rule does not address vPM, nor are there international standards for aircraft engine vPM emissions.

Engine manufacturers will have new emissions standards to follow to reduce harmful effects to health and the environment. This new rule gives manufacturers certainty about nvPM emissions criteria that they can use in developing the next generation of aircraft engines.

The final rule adopts the emissions levels and test requirements that will allow the FAA to certificate aircraft engines to the nvPM emissions standards developed by ICAO and made effective in the United States by the EPA on December 23, 2022. These new nvPM standards apply to subsonic aircraft turbofan engines having a rated output greater than 26.7 kN.

As a practical matter, the new nvPM emission standards allow engine manufacturers to use the same probe and rake collection system used to measure gaseous pollutants to simultaneously measure nvPM emissions for certification purposes. This simultaneous measurement eliminates the separate SN collection and measurement of soot on filter paper, reducing the amount of fuel needed to conduct separate engine tests, and making the component emissions measurements more representative of an engine's output.

"Manufacturers are already complying with the ICAO nvPM standards to be able to market their aircraft worldwide, so this final rule will not place any new costs on manufacturers when engines are certificated in the United States," the FAA notes in the new rule. "Manufacturers would likely incur some extra costs if this rule is not implemented, as they would be required to seek certification with a non-U.S. certification authority."

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