Page 89 of May 1, 2012 strikeout ty pe....” 1 We chose not to propose adopting this language on the nominal number of engines based on a single t ype certificate. Our reasons for this deviation were detailed in the. The interested reader is referred to the proposed rule for more detail. (See 76 F R 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 s tandards if a similar production cut - off was adopted. Therefore, we believe our approach is preferable because it more clearl y leaves the number of exemptions that might be granted open , not limited to either more or less than 75 per engine ty pe, and subj ect 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 underly ing 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 b y the Chicago Convention, but also provides streamlined processes and procedures within the regulated industry . They contended that an y 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 wor

k 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 Em ission Certification of Aircraft Engines , Appendix ”ICAO Emissions Environmental Technical Manual”.Page 199 of May 1, 2012 strikeout 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 - by case FAA approval. (a) Engines installed in new aircraft. Ty pe 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 b y a valid type certificate i ssued by FAA. ( 1 ) Submit y our request for an exemption to the FAA before producing the engines to be exempted, who will provide a cop y 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, a ll requests must include the following:Page 45 of May 1, 2021 strikeout the 2006 24 - hour PM 2.5 standard of 35 μg/m 3 without additional controls . 2 , 3 Th ese 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 NO X ensuring long - term maintenance of the NAAQS. In summa ry , the aircraft NOx reductions resulting from these new aircraft engine emission standards will be useful to states in attaining or maintaining the ozone, PM 2.5 , and NO 2 NAAQS standards. I II. Details of the Final Rule The following is a description of the regulations being adopted in this final rule, with an y 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 con tained 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 figure s ar e based on the results of EPA com puter mo deling , which is not affect ed 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 Airc raft 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.