In an action for which the airline manufacturing industry is probably well prepared, EPA has issued final NOx emission standards for aircraft turbofan and turbojet engines with rated thrusts greater than 26.7 kilonewtons (kN).

The rating range covers commercial and passenger and freighter aircraft in common use at airports across the U.S. According to EPA, the rule harmonizes U.S. regulations with of emission standards adopted by the United Nations’ International Civil Aviation Organization (ICAO) and allows enforcement of those standards in the U.S.. EPA notes that engine manufacturers participated in deliberations leading up to ICAO decisions on aircraft engine NOx emissions and subsequently incorporated changes to meet the ICAO standards.

“Thus, while there is some cost to a manufacturer for responding to the new ICAO provisions, there is no significant further direct cost to the manufacturers created by EPA’s adopting the requirements into U.S. regulations,” states EPA. “In fact, it is likely that our adopting these requirements facilitates the acceptance of U.S. type certificates by aircraft manufacturers around the world.”

Under the rule, the NOx standards are applied to (a) newly-certified engines that have never been manufactured prior to the effective date of the new standards and (b) newly-manufactured engines that were previously manufactured and certified according to pre-existing standards. Aircraft are currently subject to NOx Tier 4 levels.

Specific requirements of EPA’s rule include:

• Engine models originally certificated prior to the effective date of the rule may continue production without meeting the Tier 6 standards through December 31, 2012. (The Tier 6 standards represent an approximate 12 reduction in NOx emissions from Tier 4 standards.) After that date, these engines must comply with the new Tier 6 standards; this date is generally referred to as the Tier 6 pro¬duction cutoff. The delay in complying with the Tier 6 standards for previ¬ously certificated engine models is intended to allow for an orderly transition to the Tier 6 standards, says EPA.
• Engine models that were originally certificated between the effective date of the rule and December 31, 2013 must comply with the Tier 6 standards.
• Engine models that were originally certificated beginning on or after January 1, 2014, must comply with the Tier 8 standards, which represent an approximate 15 percent reduction in NOx emissions from Tier 6 levels. EPA says it anticipates establishing a future production cutoff to require all engine models that were originally certificated before this date to comply with the Tier 8 standards.

Also under the rule, EPA is issuing a definition of derivative engine to clarify when the emission characteristics of a new turbofan engine model vary sufficiently from its parent engine design and must therefore comply with the emission standard of a newly-certified engine.

The Agency is also requiring that manufacturers of gas turbine engines subject to any emission standard provide timely reports of emission data and other information needed to support development and maintenance of an emission inventory and air quality analysis.

Finally, the rule includes “minor amendments” to test and measurements procedures for aircraft engines.

EPA’s final rule on controlling air pollution from aircraft and aircraft engines is at http://www.epa.gov/oms/regs/nonroad/aviation/aircraft-engine-nox-frn.pdf.