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type....” 1 We chose not to propose adopting this language on the nominal number of engines 

based on a single type certificate. Our reasons for this deviation were detailed in the. The 

interested reader is referred to the proposed rule for more detail. (See 76 FR 45012. July 27. 

2011.) We also want to emphasize that the exemption provisions as proposed and promulgated 

in this notice are not necessarily limited to the Tier 6 NOx production cut-off, but could in fact 

be applied to future aircraft engine emission standards if a similar production cut-off was 

adopted. Therefore, we believe our approach is preferable because it more clearly leaves the 

number of exemptions that might be granted open, not limited to either more or less than 75 per 

engine type, and subject to the justification supplied by the engine manufacturer, both for the 

Tier 6 production cut-off and the future.

We received several comments focusing primarily on the number of exemptions and the 

underlying process that is embodied in the ETM and our proposal. General Electric Aviation 

(GE) maintained that harmonization with the international community is not only required by the 

Chicago Convention, but also provides streamlined processes and procedures within the 

regulated industry. They contended that any purported benefits to EPA’s unique exemption 

scheme were outweighed by setting up a conflict with the remainder of the world. They also 

suggested that if EPA wants a different approach for evaluating exemptions, it would be more 

appropriate to work inside the ICAO/CAEP process toward that end.

 

1 CAEP/8 – WP/18, Environmental Technical Manual (ETM), Vol II on the Use of Procedures in the 

Emission Certification of Aircraft Engines, Appendix ”ICAO Emissions Environmental Technical Manual”.
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This section specifies provisions related to exempting/excepting engines from some or all 

of the standards and requirements of this part 87. Exempted/excepted engines must conform to 

regulatory conditions specified for an exemption in this section and other applicable regulations. 

Exempted/excepted engines are deemed to be “subject to” the standards of this part even though 

they are not required to comply with the otherwise applicable requirements. Engines 

exempted/excepted with respect to certain standards must comply with other standards. 

Exemption requests under paragraph (a) of this section must be approved by the FAA, with the 

written concurrence of EPA, to be effective. Exemption requests under paragraph (b) of this 

section must be approved only by the FAA to be effective. Exceptions do not require a case-bycase FAA approval. 

(a) Engines installed in new aircraft. Type certificate holders may request an exemption

to produce a limited number of newly manufactured engines through December 31, 2016, to be 

installed in new aircraft as specified in this paragraph (a). This exemption is limited to NOx 

emissions from engines that are covered by a valid type certificate issued by FAA. 

(1) Submit your request for an exemption to the FAA before producing the engines to 

be exempted, who will provide a copy to the Designated EPA Program Officer. Exemption 

by an authority outside the United States does not satisfy this requirement. Unless EPA and 

FAA allow otherwise, all requests must include the following:
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the 2006 24-hour PM2.5 standard of 35 μg/m

3 without additional controls.2,3

 These 

numbers do not account for those areas that are close to (e.g., within 10 percent of) the standards. 

These areas, although not violating the standards, would also benefit from any reductions in NOX

ensuring long-term maintenance of the NAAQS.

In summary, the aircraft NOx reductions resulting from these new aircraft engine 

emission standards will be useful to states in attaining or maintaining the ozone, PM2.5 , and NO2

NAAQS standards.

III. Details of the Final Rule

The following is a description of the regulations being adopted in this final rule, with any 

changes from the proposal also noted. The descriptions also include our response to the most 

significant comments received on the proposal. A full summary of the comments and our 

responses are contained in the response to comments document for the rule that is available in 

the public docket for this action.4

 

2 U.S. EPA (2010). Regulatory Impact Analysis: Final Rulemaking to Establish Greenhouse Gas Emission 

Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles. Chapter 8: Health 

and Environmental Impacts. EPA 420-R-11-901.

3 These figures are based on the results of EPA computer modeling, which is not affected by the upcoming 

2008 ozone NAAQS nonattainment designations.

4 U.S. Environmental Protection Agency, “Summary and Analysis of Comments: Control of Air Pollution 

from Aircraft and Aircraft Engines,” Office of Transportation and Air Quality, EPA-420-R-12-011, May 2012. A 

copy of this document is in docket number EPA-HQ-OAR-2010-0687.