# Control of Air Pollution From Aircraft and Aircraft Engines; Proposed Emission Standards and Test Procedures

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2011-17660

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** July 27, 2011
- **Citation:** 76 FR 45012

## Text

ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 87 and 1068
[EPA-HQ-OAR-2010-0687; FRL-9437-2]
RIN 2060-AO70
Control of Air Pollution From Aircraft and Aircraft Engines; Proposed Emission Standards and Test Procedures

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

This action proposes several new NO
X
emission standards, compliance flexibilities, and other regulatory requirements for aircraft turbofan or turbojet engines with rated thrusts greater than 26.7 kilonewtons (kN). We also are proposing certain other requirements for gas turbine engines that are subject to exhaust emission standards. First, we are proposing to clarify when the emission characteristics of a new turbofan or turbojet engine model have become different enough from its existing parent engine design that it must conform to the most current emission standards. Second, we are proposing a new reporting requirement for manufacturers of gas turbine engines that are subject to any exhaust emission standard to provide us with timely and consistent emission-related information. Third, and finally, we are proposing amendments to aircraft engine test and emissions measurement procedures. EPA actively participated in the United Nation's International Civil Aviation Organization (ICAO) proceedings in which most of these proposed requirements were first developed. These proposed regulatory requirements have largely been adopted or are actively under consideration by its member states. By adopting such similar standards, therefore, the United States will maintain consistency with these international efforts.

DATES:

Comments must be received on or before September 26, 2011.

Hearing:
The public hearing will be held on August 11, 2011 at the Sheraton Chicago O'Hare Airport Hotel, 6501 North Mannheim Road, Rosemont, IL 60018. Telephone (847)699-6300. See section VII for more information about public hearings.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2010-0687, by one of the following methods:

http://www.regulations.gov:
Follow the on-line instructions for submitting comments.

•
E-mail: A-and-R-Docket@epamail.epa.gov.

•
Fax:
202-566-9744.

Mail:
EPA Docket center, EPA West (Air Docket), Attention Docket ID No. EPA-HQ-OAR-2010-0687, Mailcode: Mail Code 2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460. Please include a total of two copies. In addition, please mail a copy of your comments to the contact person identified below (see
FOR FURTHER INFORMATION CONTACT
). Please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th Street, NW., Washington, DC 20503.

Instructions:
Direct your comments to Docket ID No. EPA-HQ-OAR-2010-0687. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at
http://www.regulations.gov,
including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through
http://www.regulations.gov
or e-mail. The
http://www.regulations.gov
Web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through
http://www.regulations.gov
your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses.

Docket:
All documents in the docket are listed in the
http://www.regulations.gov
index. Although listed in the index, some information is not publicly available,
e.g.,
CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in
http://www.regulations.gov
or in hard copy at EPA Docket Center, EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the EPA Docket Center is 202-566-1742

FOR FURTHER INFORMATION CONTACT:

Richard Wilcox, Office of Transportation and Air Quality, Office of Air and Radiation, Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; telephone number: (734) 214-4390; fax number: (734) 214-4816; e-mail address:
wilcox.rich@epa.gov.

SUPPLEMENTARY INFORMATION:

Does this action apply to me?

Entities potentially regulated by this action are those that manufacture and sell aircraft engines and aircraft in the United States. Regulated categories include:

Category

NAICS
a
Codes

SIC Codes
b

Examples of potentially affected entities

Industry
336412
3724
Manufacturers of new aircraft engines.

Industry
336411
3721
Manufacturers of new aircraft.

a
North American Industry Classification System (NAICS)

b
Standard Industrial Classification (SIC) system code

This table lists the types of entities that EPA is now aware could potentially be regulated by this action. Other types of entities not listed in the table could also be regulated. To determine whether your activities are regulated by this

action, you should carefully examine the applicability criteria in 40 CFR 87.1 (part 87). If you have any questions regarding the applicability of this action to a particular entity, consult the person listed in the preceding
FOR FURTHER INFORMATION CONTACT
section.

Table of Contents

I. Overview and Background

A. Summary of the Proposal

B. EPA's Responsibilities Under the Clean Air Act

C. Interaction With the International Community

D. Brief History of EPA's Regulation of Aircraft Engine Emissions

E. Brief History of ICAO Regulation of Aircraft Engine Emissions

II. Why is EPA taking this action?

A. NO
X
Inventory Contribution

1. Landing and Takeoff (LTO) Emissions

2. Non-LTO Emissions

B. Health, Environmental and Air Quality Impacts

1. Background on Ozone, PM and NO
X

a. What is ozone?

b. What is particulate matter?

c. What is NO
X
?

2. Health Effects Associated With Exposure to Ozone, PM and NO
X

a. What are the health effects of ozone?

b. What are the health effects of PM?

c. What are the health effects of NO
X
?

3. Environmental Effects Associated With Exposure to Ozone, PM and NO
X

a. Deposition of Nitrogen

b. Visibility Effects

c. Plant and Ecosystem Effects of Ozone

4. Impacts on Ambient Air Quality

III. Details of the Proposed Rule

A. NO
X
Standards for Newly-Certified Engines

1. Tier 6 NO
X
Standards for Newly-Certified Engines

a. Numerical Emission Limits for Higher Thrust Engines

b. Numerical Emission Limits for Lower Thrust Engines

2. Tier 8 NO
X
Standards for Newly-Certified Engines

a. Numerical Emission Limits for Higher Thrust Engines

b. Numerical Emission Limits for Lower Thrust Engines

B. Application of NO
X
Standards for Newly-Manufactured Engines

1. Phase-In of the Tier 6 NO
X
Standards for Newly-Manufactured Engines

2. Exemptions and Exceptions From the Tier 6 Production Cutoff

a. New Provisions for Spare Engines

b. New Provisions for Engines Installed in New Aircraft

i. Time-Frame and Scope

ii. Production Limit

iii. Exemption Requests

iv. Coordination of Exemption Requests

c. Voluntary Emission Offsets

3. Potential Phase-In of New Tier 8 NO
X
Standards for Newly-Manufactured Engines

C. Application of Standards for Derivative Engines for Emission Certification Purposes

D. Annual Reporting Requirement

E. Proposed Standards for Supersonic Aircraft Turbine Engines

F. Amendments to Test and Measurement Procedures

G. Possible Future Revisions to Emission Standards for New Technology Turbine Engines and Supersonic Aircraft Turbine Engines

IV. Description of Other Revisions to the Regulatory Text

A. Applicability Issues

1. Military Engines

2. Noncommercial Engines

B. Non-Substantive Revisions

C. Clarifying Language for Regulatory Text

V. Technical Feasibility, Costs, and Emission Benefits

VI. Consultation With FAA

VII. Public Participation

VIII. Statutory Provisions and Legal Authority

IX. Statutory and Executive Orders Review

A. Executive Order 12866: Regulatory Planning and Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Analysis

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

G. Executive Order 13045: Protection of Children From Environmental Health & Safety Risks

H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer Advancement Act

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low Income Populations

I. Overview and Background

This section summarizes the major provisions of the proposed rule for aircraft gas turbine engines. It also contains background on the EPA's standard setting authority and responsibilities under the Clean Air Act, the connection between our emission standards and those of the international community, and a brief regulatory history for this source of emissions.

A. Summary of the Proposal

We are proposing several new emission standards and other regulatory requirements for aircraft turbofan and turbojet engines
1

with rated thrusts greater than 26.7 kilonewtons (kN). First, we are proposing two new tiers of more stringent emission standards for oxides of nitrogen (NO
X
). The proposed standards would apply differently to two classes of these engines,
i.e.,
“newly-certified engines” and “newly-manufactured engines.” The newly-certified engine standards would apply to aircraft engines that have received a new type certificate and have never been manufactured prior to the effective date of the new emission standards. Requirements for newly-manufactured engines would apply to aircraft engines that were previously certified and manufactured in compliance with preexisting standards, and would require manufacturers to either comply with the newer standards by a specified future date or cease production. Newly-manufactured engine standards are also sometimes referred to as “production cutoff” standards. Second, we are proposing certain time-limited flexibilities,
i.e.,
the potential for exemptions or exceptions as defined in the regulations for newly-manufactured engines that may not be able to comply with the first tier of the proposed NO
X
standards because of specific technical or economic reasons.

1
Turbofan and turbojet engines will be collectively referred to as turbofan engines hereafter for convenience.

We are also proposing a number of additional changes that would apply to a wider range of aircraft gas turbine engines
2

than those that would be subject to the proposed new emission standards. First, we are proposing to define a derivative engine for emissions certification purposes. The intent of this definition is to distinguish when the emission characteristics of a new turbofan engine model vary sufficiently from its existing parent engine design, and must show compliance with the emission standard for a newly-certificated engine. Second, we are proposing new reporting requirements for manufacturers that produce gas turbine engines subject to any exhaust emission standard. This would provide us with timely and consistent emission data and other information that is necessary to conduct emission analyses and develop appropriate public policy for the aviation sector. Specifically, reports would be required for turbofan engines with rated thrusts greater than 26.7 kN, which are subject to gaseous emission and smoke standards, in addition to turbofans less than or equal to 26.7 kN, and all turboprop engines, that are only subject to smoke standards. Third, we are proposing amendments to the test and measurement procedures for aircraft engines. Finally, as described in section IV., we are proposing minor amendments to provisions addressing definitions, acronyms and abbreviations, general applicability and

requirements, exemptions, and incorporation by reference.

2
The term gas turbine engine includes turbofan, turbojet, and turboprop engines designs. The rated output for turbofan and turbojet engines is normally expressed as kilonewtons (kN) thrust. The rated output for turboprop engines is normally expressed as shaft horsepower (hp) or shaft kilowatt (kW).

Most of these proposed regulatory requirements have already been adopted or are actively under consideration by the United Nation's International Civil Aviation Organization (ICAO). The proposed requirements would bring the United States into alignment with the international standards and recommended practices.

B. EPA's Authority and Responsibilities Under the Clean Air Act

Section 231(a)(2)(A) of the Clean Air Act (CAA) directs the Administrator of EPA to, from time to time, propose aircraft engine emission standards applicable to the emission of any air pollutant from classes of aircraft engines which in her judgment causes or contributes to air pollution that may reasonably be anticipated to endanger public health or welfare. (See 42 U.S.C. 7571(a)(2)(A).) Section 231(a)(2)(B) directs EPA to consult with the Administrator of the Federal Aviation Administration (FAA) on such standards, and prohibits EPA from changing aircraft emission standards if such a change would significantly increase noise and adversely affect safety. 42 U.S.C. 7571(a)(2)(B)(i)-(ii). Section 231(a)(3) provides that after we propose standards, the Administrator shall issue such standards “with such modifications as he deems appropriate.” 42 U.S.C. 7571(a)(3). The U.S. Court of Appeals for the DC Circuit has held that this provision confers an unusually broad degree of discretion on EPA to adopt aircraft engine emission standards as the Agency determines are reasonable.
NACAA
v.
EPA,
489 F.3d 1221 (DC Cir. 2007).

In addition, under CAA section 231(b) EPA is required to ensure, in consultation with the U.S. Department of Transportation (DOT), that the effective date of any standard provides the necessary time to permit the development and application of the requisite technology, giving appropriate consideration to the cost of compliance. 42 U.S.C. 7571(b). Section 232 then directs the FAA to prescribe regulations to insure compliance with EPA's standards. 42 U.S.C. 7572. Finally, section 233 of the CAA vests the authority to promulgate emission standards for aircraft or aircraft engines only in EPA. States are preempted from adopting or enforcing any standard respecting aircraft engine emissions unless such standard is identical to EPA's standards. 42 U.S.C. 7573. Section VI. of today's proposal further discusses our coordination with DOT through the FAA.
3

It also describes DOT's responsibility under the CAA to enforce the aircraft emission standards established by EPA.

3
The functions of the Secretary of Transportation under part B of title II of the Clean Air Act (§§ 231-234, 42 U.S.C. 7571-7574) have been delegated to the Administrator of the FAA. 49 CFR 1.47(g).

C. Interaction With the International Community

We began regulating the emissions from aircraft engines in 1973. Since that time, we have worked with the FAA and later with the International Civil Aviation Organization (ICAO) to develop international standards and other recommended practices pertaining to aircraft engine emissions. ICAO was established in 1944 by the United Nations (by the Convention on International Civil Aviation, the “Chicago Convention”) “* * * in order that international civil aviation may be developed in a safe and orderly manner and that international air transport services may be established on the basis of equality of opportunity and operated soundly and economically.”
4

ICAO's responsibilities include developing aircraft technical and operating standards, recommending practices, and generally fostering the growth of international civil aviation. The United States is currently one of 190 participating member States of ICAO.
5 6

4
International Civil Aviation Organization (ICAO), “Convention on International Civil Aviation,” Ninth Edition, Document 7300/9, 2006. Copies of this document can be obtained from the ICAO Web site located at
http://www.icao.int.

5
Members of ICAO's Assembly are generally termed member States or contracting States. These terms are used interchangeably throughout this preamble.

6
There are currently 190 Contracting States according to ICAO website located at
http://www.icao.int.

In the interests of global harmonization and international air commerce, the Chicago Convention urges a high degree of uniformity by its member States. Nonetheless, the Convention also recognizes that member States may adopt their own unique airworthiness standards and that some may adopt standards that are more stringent than those agreed upon by ICAO.

The Convention has a number of other features that govern international commerce. First, States that wish to use aircraft in international transportation must adopt emission standards and other recommended practices that are at least as stringent as ICAO's standards. States may ban the use of any aircraft within their airspace that does not meet ICAO standards.
7

Second, States are required to recognize the airworthiness certificates of any State whose standards are at least as stringent as ICAO's standards, thereby assuring that aircraft of any member State will be permitted to operate in any other member State.
8

Third, and finally, to ensure that international commerce is not unreasonably constrained, a participating nation which elects to adopt more stringent standards is obligated to notify ICAO of the differences between its standards and ICAO standards.
9

However, if a nation sets tighter standards than ICAO, air carriers not based in that nation (foreign-flagged carriers) would only be required to comply with ICAO standards or more stringent standards imposed by their own nations, if applicable.

7
ICAO, “Convention on International Civil Aviation,” Article 87, Ninth Edition, Document 7300/9, 2006. Copies of this document can be obtained from the ICAO website located at
http://www.icao.int/icaonet/arch/doc/7300/7300_9ed.pdf.

8
ICAO, “Convention on International Civil Aviation,” Article 33, Ninth Edition, Document 7300/9, 2006. Copies of this document can be obtained from the ICAO Web site located at
http://www.icao.int/icaonet/arch/doc/7300/7300_9ed.pdf.

9
ICAO, “Convention on International Civil Aviation,” Articles 38, Ninth Edition, Document 7300/9, 2006. Copies of this document can be obtained from the ICAO Web site located at
http://www.icao.int/icaonet/arch/doc/7300/7300_9ed.pdf.

ICAO Council's Committee on Aviation Environmental Protection (CAEP) undertakes ICAO's technical work in the environmental field. The Committee is responsible for evaluating, researching, and recommending measures to the ICAO Council that address the environmental impact of international civil aviation. CAEP is composed of various task groups, work groups, and other contributing committees whose contributing members include atmospheric, economic, aviation, environmental, and other professionals. At CAEP meetings, the United States is represented by the FAA, which plays an active role at these meetings. EPA has historically been a principal participant in the development of U.S. policy in various ICAO/CAEP working groups and other international venues, assisting and advising FAA on aviation emissions, technology, and policy matters. If ICAO adopts a CAEP proposal for a new environmental standard, it then becomes part of ICAO standards and recommended practices (Annex 16 to the Chicago Convention).
10

10
ICAO, “Aircraft Engine Emissions,” International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Second Edition, July 2008. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

D. Brief History of EPA's Regulation of Aircraft Engine Emissions

As mentioned above, we initially regulated gaseous exhaust emissions, smoke, and fuel venting from aircraft engines in 1973.
11

Since that time, we have occasionally revised those regulations. Two of these revisions are most pertinent to today's proposal. First, in a 1997 rulemaking, we made our emission standards and test procedures more consistent with those of ICAO for turbofan engines used in commercial aviation with rated thrusts greater than 26.7kN.
12

These ICAO requirements are generally referred to as CAEP/2 standards. (The numbering nomenclature for CAEP requirements is discussed in the next section.) That action included new NO
X
emission standards for newly-manufactured commercial turbofan engines (those engines built after the effective date of the regulations that were already certified to pre-existing standards)
13

and for newly-certified commercial turbofan engines (those engine models that received their initial type certificate after the effective date of the regulations). It also included a CO emission standard for newly-manufactured commercial turbofan engines. Second, in our most recent rulemaking in 2005, we promulgated more stringent NO
X
emission standards for newly-certified commercial turbofan engines.
14

That final rule brought the U.S. standards closer to alignment with ICAO CAEP/4 requirements that were effective in 2004. In ruling on a petition for judicial review of the 2005 rule filed by the National Association of Clean Air Agencies (NACAA), the U.S. Court of Appeals held that EPA's approach of tracking the ICAO standards was reasonable and permissible under the CAA.
NACAA
v.
EPA,
489 F.3d 1221, 1230-32 (DC Cir. 2007).

11
U.S. EPA, “Emission Standards and Test Procedures for Aircraft;” Final Rule, 38 FR 19088, July 17, 1973.

12
U.S. EPA, “Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures;” Final Rule, 62 FR 25356, May 8, 1997. While ICAO's standards were not limited to “commercial” aircraft engines, our 1997 standards were explicitly limited to commercial engines, as our finding that NO
X
and CO emissions from aircraft engines cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare was so limited, See 62 FR 25358. As explained later in today's notice, we are proposing to expand the scope of that finding and of our standards to include such emissions from both commercial and non-commercial aircraft engines, in order to bring our standards into full alignment with ICAO's.

13
This does not mean that in 2005 we promulgated requirements for the re-certification or retrofit of existing in-use engines.

14
U.S. EPA, “Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures;” Final Rule, 70 FR 2521, November 17, 2005.

E. Brief History of ICAO Regulation of Aircraft Engine Emissions

The first international standards and recommended practices for aircraft engine emissions was recommended by CAEP's predecessor, the Committee on Aircraft Engine Emissions (CAEE), and adopted by ICAO in 1981.
15

These standards limited aircraft engine emissions of HC, CO, and NO
X
. In 1994, ICAO adopted a CAEP/2 proposal to tighten the original NO
X
standard by 20 percent and amend the test procedures.
16

At the next CAEP meeting (CAEP/3) in 1995, the Committee recommended a further tightening of 16 percent and additional test procedure amendments, but in 1997 the ICAO Council rejected this stringency proposal and approved only the test procedure amendments. At the CAEP/4 meeting in 1998, the Committee adopted a similar 16 percent NO
X
reduction proposal, which ICAO approved on 1998. The CAEP/4 standards applied only to new engine designs certified after December 31, 2003 (
i.e.,
the requirements did not also apply to newly-manufactured engines unlike the CAEP/2 standards). In 2004, CAEP/6 recommended a 12 percent NO
X
reduction, which ICAO approved in 2005.
17 18

The CAEP/6 standards applied to newly-certified engine models beginning after December 31, 2007. At the most recent meeting, CAEP/8 recommended a further tightening of the NO
X
standards by 15 percent for newly-certified engines.
19 20

The Committee also recommended that the CAEP/6 standards be applied to newly-manufactured engines. ICAO is currently considering the CAEP/8 recommendations. We expect final ICAO action regarding the CAEP/8 recommendations in 2011.

15
ICAO, Foreword of “Aircraft Engine Emissions,” International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Third Edition, July 2008. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

16
CAEP conducts its work over a period of years. Each work cycle is numbered sequentially and that identifier is used to differentiate the results from one CAEP to another by convention. The first technical meeting on aircraft emission standards was CAEP's successor,
i.e.,
CAEE. The first meeting of CAEP, therefore, is referred to as CAEP/2.

17
CAEP/5 did not address new aircraft engine emission standards.

18
ICAO, “Aircraft Engine Emissions,” Annex 16, Volume II, Third Edition, July 2008, Amendment 4 effective on July 20, 2008. Copies of this document can be obtained from the ICAO Web site at
http://www.icao.int.

19
CAEP/7 did not address new aircraft engine emission standards.

20
ICAO, “Committee on Aviation Environmental Protection (CAEP), Report of the Eighth Meeting, Montreal, February 1-12, 2010,” CAEP/8-WP/80. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

II. Why is EPA taking this action?

As mentioned above, section 231(a)(2)(A) of the CAA authorizes the EPA Administrator to “from time to time, issue proposed emission standards applicable to the emission of any air pollution from any class or classes of aircraft or aircraft engines which in his judgment causes, or contributes to air pollution which may reasonably be anticipated to endanger public health or welfare.” 42 U.S.C. 7571(a)(2)(A).

One of the principal components of aircraft exhaust emissions is NO
X
. NO
X
is a precursor to the formation of tropospheric ozone.
21

Many commercial airports are located in urban areas and many of these areas have ambient pollutant levels above the National Ambient Air Quality Standards (NAAQS) for ozone and fine particulate matter (PM
2.5
) (
i.e.,
they are in nonattainment for ozone and PM
2.5
). This section discusses the contribution of aircraft engines used in commercial service with rated thrusts greater than 26.7kN to the national NO
X
emissions inventory and to NO
X
emission inventories in selected ozone nonattainment areas, the potential effect of NO
X
emissions in the upper atmosphere on ground level PM
2.5
in addition to the health and welfare impacts of NO
X
and PM emissions.

21
Ground-level ozone, the main ingredient in smog, is formed by complex chemical reactions of volatile organic compounds (VOC) and NO
X
in the presence of heat and sunlight. Standards that reduce NO
X
emissions will help address ambient ozone levels. They can also help reduce particulate matter (PM) levels as NO
X
emissions can also be part of the secondary formation of PM. See Section II.B below.

A. Inventory Contribution

In contrast to all other mobile sources, whose emissions occur completely at ground level, the emissions from aircraft and aircraft engines can be divided into two flight regimes. The first regime includes the emissions that are released in the lower layer of the atmosphere and directly affect local and regional ambient air quality. These emissions generally occur at or below 3,000 feet above ground level,
i.e.,
during the landing and takeoff (LTO) cycle. The aircraft operations that comprise an LTO cycle are: engine idle at the terminal gate (and sometimes during ground delays while holding for the active runway); taxiing between the terminal and the runway; take-off; climb-out; and approach to the airport. The second regime includes emissions that occur above 3,000 feet above ground level,

known as non-LTO emissions. Collectively, the emissions associated with all ground and flight operations are generally referred to as full flight emissions.

The aircraft engine NO
X
emission inventories for the LTO and non-LTO flight regimes described above are discussed separately in the following sections.

1. Landing and Takeoff Emissions

In this section, we will discuss NO
X
emission inventories for commercial turbine-engine aircraft, both nationally and for selected ozone nonattainment areas (NAAs). These inventories reflect emissions during the landing and takeoff cycle only. The most recent comprehensive analysis of historical and current LTO emissions from aircraft engines comes from a study undertaken for us by Eastern Research Group (ERG).
22

The study analyzed the national emissions of commercial aircraft operations in the United States, and showed that in the most recent year studied (2008), such aircraft operations contributed about 97 thousand tons to the national NO
X
inventory. A summary of the national inventory of LTO NO
X
emissions is shown in Table 1.

22
“Historical Assessment of Aircraft Landing and Take-off Emissions (1986-2008),” Eastern Research Group, May 2011. A copy of this document can be found in public docket EPA-HQ-OAR-2010-0687.

When these nationwide LTO emissions are compared to the total U.S. mobile source inventory for 2009, they account for less than one percent of the total. However, such a comparison may be a bit misleading, as it only includes those aircraft emissions that occur below 3,000 feet altitude, while comparing them to the entirety of other mobile source emissions. In the U.S., LTO emissions account for only about ten percent of full flight NO
X
emissions. When considering full flight aircraft emissions (
i.e.,
including both LTO and non-LTO emissions), the contribution of aircraft to the total mobile source NO
X
inventory is approximately 7.7 percent.
23

23
U.S. EPA, “Comparison of Aircraft LTO and Full Flight NO
X
Emissions to Total Mobile Source NO
X
Emissions,” memorandum from John Mueller, Assessment and Standards Division, Office of Transportation and Air Quality, to docket EPA-HQ-OAR-2010-0687, May 10, 2011.

Table 1—Current National NO
X
Emissions From Commercial Aircraft

Aircraft category

2008 total NO
X

(thousand tons)

Air Carrier
86

Commuter/Air Taxi
11

Total Commercial
97

In addition, it is important to assess the contribution of commercial aircraft LTO NO
X
emissions on a local level, especially in areas containing or adjacent to airports. The historical analysis conducted by ERG also included an assessment of selected ozone nonattainment areas (NAAs). The NAAs selected for study were chosen as follows. First, the 25 ozone NAAs with airports which had high commercial traffic volumes were identified. Second, the 25 ozone NAAs with the largest population were identified. These lists were combined. However, there was some overlap, and this led to a total of 41 NAAs being identified for the study. These 41 NAAs collectively include 200 airports, accounting for about 70 percent of commercial air traffic operations. Although 41 NAAs were studied, the non-aircraft emissions data source that the aircraft emissions were compared to for this analysis did not distinguish between the Boston NAA in Massachusetts and the greater Boston NAA in New Hampshire. Thus, aircraft emissions from those two NAAs were combined into a single NAA for the purpose of this analysis, yielding 40 NAAs for study. Current (2008) and projected (2020) NO
X
emissions for these 40 NAAs, as well as the percent contribution of aircraft to total mobile source inventories (as compared to 2005 and 2020 mobile source inventories), are shown in Table 2.
24 25

The relative contribution of aircraft in any given NAA varies based on activity in other transportation and industrial sectors. As can be seen from this table, expected growth in aircraft operations in many of these areas combined with anticipated reductions in NO
X
emissions from other mobile source categories results in the growth of the relative contribution of aircraft LTO emissions to mobile source NO
X
emissions in NAAs.

24
U.S. EPA, “Relative Contribution of Aircraft to Total Mobile Source NO
X
Emissions in Selected Ozone Nonattainment Areas,” memorandum from John Mueller, Assessment and Standards Division, Office of Transportation and Air Quality, to docket EPA-HQ-OAR-2010-0687, May 10, 2011.

25
U.S. EPA, “Addendum to “Relative Contribution of Aircraft to Total Mobile Source NO
X
Emissions in Selected Ozone Nonattainment Areas,”” memorandum from John Mueller, Assessment and Standards Division, Office of Transportation and Air Quality, to docket EPA-HQ-OAR-2010-0687, May 17, 2011.

Table 2—Current NO
X
Emissions in Selected Ozone Nonattainment Areas

Nonattainment area

2008 total NO
X

(tons)

2008 aircraft

percent of mobile source NO
X

2020 aircraft

percent of mobile source NO
X

Albuquerque, NM
380
1.6
4.3

Anchorage, AK
2,538
23.4
49.3

Aspen
16
2.0
6.6

Atlanta, GA
5,808
2.6
8.2

Baltimore, MD
1,148
1.3
4.4

Boston—including MA and NH NAAs
2,032
1.0
2.7

Charlotte-Gastonia-Rock Hill, NC-SC
1,917
2.6
10.0

Chicago-Gary-Lake County, IL-IN
6,007
1.8
5.0

Cincinnati-Hamilton, OH-KY-IN
1,287
1.5
3.3

Cleveland-Akron-Lorain, OH
680
0.5
1.3

Dallas-Fort Worth, TX
3,880
1.7
6.9

Denver-Boulder-Greeley-Fort Collins-Loveland, CO
2,649
2.5
7.1

Detroit-Ann Arbor, MI
2,312
1.1
3.0

El Paso, TX
223
0.9
1.1

Greater Connecticut, CT
405
0.8
2.4

Houston-Galveston-Brazoria, TX
3,045
1.3
3.4

Indianapolis, IN
1,089
1.4
3.0

Las Vegas, NV
2,308
6.0
15.8

Los Angeles South Coast Air Basin, CA
6,479
1.5
4.5

Louisville, KY-IN
1,211
1.9
6.2

Memphis, TN-AR
2,988
6.3
16.8

Milwaukee-Racine, WI
557
0.9
3.2

Minneapolis-St Paul, MN
2,154
1.0
5.1

New York-N. New Jersey-Long Island, NY-NJ-CT
10,093
2.3
6.3

Philadelphia-Wilmington-Atlantic City, PA-NY-MD-DE
2,308
1.0
2.8

Phoenix-Mesa, AZ
2,298
1.4
3.3

Pittsburgh-Beaver Valley, PA
480
0.5
1.1

Providence (entire State), RI
232
1.0
2.3

Raleigh-Durham-Chapel Hill, NC
565
1.0
3.2

Reno, NV
246
1.9
4.4

Riverside County (Coachella Valley), CA
70
0.2
0.5

Sacramento Metro, CA
603
1.0
2.0

Salt Lake City, UT
1,235
4.4
14.1

San Diego, CA
1,035
1.4
3.4

San Francisco Bay Area, CA
4,405
2.7
6.7

San Joaquin Valley, CA
74
0.0
0.1

Seattle-Tacoma, WA
1,958
1.4
3.9

St. Louis, MO-IL
810
0.6
1.6

Syracuse, NY
139
0.8
1.9

Washington, DC-MD-VA
2,983
2.0
6.2

Table 3 shows how commercial aircraft operations are projected to rise in the future on a nationwide basis. As operations increase, the inventory impact of these aircraft on national and local NO
X
inventories will also increase, as was seen in Table 2.

Table 3—Current and Projected Commercial Aircraft Operations

Year

Air carrier
operations
(millions)

Commuter/air taxi operations
(millions)

Total commercial operations
(millions)

Total increase in commercial
operations over 2008
(percent)

2008
14.1
13.8
27.9

2020
16.5
14.1
30.5
9

2030
20.6
16.0
36.6
31

Source: December 2010 FAA TAF, which is located at
http://aspm.faa.gov/main/taf.asp.

2. Non-LTO Emissions

Historically, emphasis has been placed on evaluating emissions during LTO operations given their obvious impact on local air quality. Less emphasis has been placed on evaluating emissions from non-LTO operations (emissions at altitudes greater than 3,000 feet above ground level) based on the assumption that such emissions have a lesser impact on local air quality. However, modeling by Barrett
et al.
(2010) finds that these upper atmosphere emissions may adversely affect public health more than was previously thought.
26

Based on the data and methodology of the authors, this effect is caused primarily by two pathways:

26
Barrett, S. R. H., R. E. Britter and I. A. Waitz, 2010. Global mortality attributable to aircraft cruise emissions.
Environmental Science & Technology
44 (19), pp. 7736-7742. DOI: 10.1021/es101325r.

The formation of fine particulate matter,
i.e.,
PM
2.5
, from emission of gaseous precursors of PM (NO
X
and SO
2
) in the upper atmosphere that are then transported to the lower atmosphere. (The formation of secondary PM
2.5
from NO
X
is discussed further in section II.B.1.b).

Aviation NO
X
emissions promote ozone formation throughout the troposphere and hence increase hydroxyl radical (OH) concentrations. This increases the oxidation of non-aviation SO
2
(such as that emitted from power stations) in the gas phase relative to aqueous oxidation and dry deposition thereby increasing atmospheric sulfate (a type of PM
2.5
) concentrations.

The authors of this work estimated that full flight emissions cause almost 10,000 premature mortalities (their central estimate) per year worldwide, with over 450 per year in the U.S. The pollutants emitted during cruise operations were estimated to be about 80 percent of the population-weighed PM
2.5
from aviation, with the remainder being associated with LTO operations (although they note the LTO portion may be under-estimated). The study asserts that over 380 premature mortalities per year in the U.S. can be attributed to secondary PM
2.5
associated with non-LTO operations. We request comments on the results of these studies and the existence of other research into this area.

B. Health, Environmental and Air Quality Impacts

NO
X
emissions from aircraft and other mobile and stationary sources contribute to the formation of ozone. In addition, NO
X
emissions at low altitude

also react in the atmosphere to form secondary fine particulate matter (PM
2.5
), particularly ammonium nitrate. In the following sections we discuss the adverse health and welfare effects associated with NO
X
emissions, in addition to the current and projected levels of ozone and PM across the country. The ICAO NO
X
standards with which we are proposing to align will help reduce ambient ozone and secondary PM levels and thus will help areas with airports achieve or maintain compliance with the National Ambient Air Quality Standards (NAAQS).
27

27
The discussion of PM health and welfare effects throughout this notice relates exclusively to the effects of the proposed NO
X
emission standards on the formation of secondary PM from nitrate formation in the atmosphere. Presently, there are no emission standards for PM emitted directly from aircraft turbine engines. The current and planned future work programs for CAEP/ICAO are developing PM test procedures and information to characterize the amount and type of these emissions from aircraft engines that are in production. Ultimately, this information will be used to assess the need for an aircraft turbine engine PM standard (
i.e.,
whether PM emissions from aircraft cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare), with standard setting as appropriate.

1. Background on Ozone, PM and NO
X

a. What is ozone?

Ground-level ozone pollution is typically formed by the reaction of VOC and NO
X
in the lower atmosphere in the presence of sunlight. These pollutants, often referred to as ozone precursors, are emitted by many types of pollution sources, such as highway and nonroad motor vehicles and engines, power plants, chemical plants, refineries, makers of consumer and commercial products, industrial facilities, and smaller area sources.

The science of ozone formation, transport, and accumulation is complex.
28

Ground-level ozone is produced and destroyed in a cyclical set of chemical reactions, many of which are sensitive to temperature and sunlight. When ambient temperatures and sunlight levels remain high for several days and the air is relatively stagnant, ozone and its precursors can build up and result in more ozone than typically occurs on a single high-temperature day. Ozone can be transported hundreds of miles downwind from the sources of precursor emissions, resulting in elevated ozone levels even in areas with low local VOC or NO
X
emissions.

28
U.S. EPA Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental Protection Agency, Washington, DC, EPA 600/R-05/004aF-cF, 2006. This document is available in Docket EPA-HQ-OAR-2010-0687. This document may be accessed electronically at:
http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html.

b. What is particulate matter?

The discussion includes PM
2.5
because the NO
X
emitted by aircraft engines can react in the atmosphere to form nitrate, a component of PM
2.5
. Particulate matter is a generic term for a broad class of chemically and physically diverse substances. It can be principally characterized as discrete particles that exist in the condensed (liquid or solid) phase spanning several orders of magnitude in size. Since 1987, EPA has delineated that subset of inhalable particles small enough to penetrate to the thoracic region (including the tracheobronchial and alveolar regions) of the respiratory tract (referred to as thoracic particles). Current NAAQS use PM
2.5
as the indicator for fine particles (with PM
2.5
referring to particles with a nominal mean aerodynamic diameter less than or equal to 2.5 µm), and use PM
10
as the indicator for purposes of regulating the coarse fraction of PM
10
(referred to as thoracic coarse particles or coarse-fraction particles; generally including particles with a nominal mean aerodynamic diameter greater than 2.5 µm and less than or equal to 10 µm, or PM
10-2.5
). Ultrafine particles are a subset of fine particles, generally less than 100 nanometers (0.1 μm) in aerodynamic diameter.

Fine particles are produced primarily by combustion processes and by transformations of gaseous emissions (
e.g.,
SO
X
, NO
X
and VOC) in the atmosphere. The chemical and physical properties of PM
2.5
may vary greatly with time, region, meteorology, and source category. Thus, PM
2.5
may include a complex mixture of different pollutants including sulfates, nitrates, organic compounds, elemental carbon and metal compounds. These particles can remain in the atmosphere for days to weeks and travel hundreds to thousands of kilometers.

c. What is NO
X
?

Nitrogen dioxide (NO
2
) is a member of the NO
X
family of gases. Most NO
2
is formed in the air from the oxidation of nitric oxide (NO) emitted when fuel is burned at a high temperature. NO
2
can dissolve in water vapor and further oxidize to form nitric acid which reacts with ammonia to form nitrates, an important component of ambient PM. NO
X
along with non-methane hydrocarbon (NMHC) are the two major precursors of ozone. The health effects of ozone, ambient PM and NO
X
are covered in section II.B.2.

2. Health Effects Associated With Exposure to Ozone, PM and NO
X

a. What are the health effects of ozone?

The health and welfare effects of ozone are well documented and are assessed in EPA's 2006 Air Quality Criteria Document (ozone AQCD) and 2007 Staff Paper.
29 30

People who are more susceptible to effects associated with exposure to ozone can include children, the elderly, and individuals with respiratory disease such as asthma. Those with greater exposures to ozone, for instance due to time spent outdoors (
e.g.,
children and outdoor workers), are of particular concern. Ozone can irritate the respiratory system, causing coughing, throat irritation, and breathing discomfort. Ozone can reduce lung function and cause pulmonary inflammation in healthy individuals. Ozone can also aggravate asthma, leading to more asthma attacks that require medical attention and/or the use of additional medication. Thus, ambient ozone may cause both healthy and asthmatic individuals to limit their outdoor activities. In addition, there is suggestive evidence of a contribution of ozone to cardiovascular-related morbidity and highly suggestive evidence that short-term ozone exposure directly or indirectly contributes to non-accidental and cardiopulmonary-related mortality, but additional research is needed to clarify the underlying mechanisms causing these effects. In a recent report on the estimation of ozone-related premature mortality published by the National Research Council (NRC), a panel of experts and reviewers concluded that short-term exposure to ambient ozone is likely to contribute to premature deaths and that ozone-related mortality should be included in estimates of the health benefits of reducing ozone exposure.
31

Animal toxicological evidence indicates that with repeated exposure, ozone can

inflame and damage the lining of the lungs, which may lead to permanent changes in lung tissue and irreversible reductions in lung function. The respiratory effects observed in controlled human exposure studies and animal studies are coherent with the evidence from epidemiologic studies supporting a causal relationship between acute ambient ozone exposures and increased respiratory-related emergency room visits and hospitalizations in the warm season. In addition, there is suggestive evidence of a contribution of ozone to cardiovascular-related morbidity and non-accidental and cardiopulmonary mortality.

29
U.S. EPA Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental Protection Agency, Washington, DC, EPA 600/R-05/004aF-cF, 2006. This document is available in Docket EPA-HQ-OAR-2010-0687. This document may be accessed electronically at:
http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html.

30
U.S. EPA (2007) Review of the National Ambient Air Quality Standards for Ozone, Policy Assessment of Scientific and Technical Information. OAQPS Staff Paper.EPA-452/R-07-003. This document is available in Docket EPA-HQ-OAR-2010-0687. This document is available electronically at:
http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_sp.html.

31
National Research Council (NRC), 2008.
Estimating Mortality Risk Reduction and Economic Benefits from Controlling Ozone Air Pollution.
The National Academies Press: Washington, DC. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

b. What are the health effects of PM?

Scientific studies show ambient PM is associated with a series of adverse health effects. These health effects are discussed in detail in EPA's Integrated Science Assessment for Particulate Matter (ISA).
32

The ISA summarizes evidence associated with PM
2.5
, PM
10-2.5
, and ultrafine particles (UFPs), and concludes the following.

32
U.S. EPA (2009) Integrated Science Assessment for Particulate Matter, EPA 600/R-08/139F. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

The ISA concludes that health effects associated with short-term exposures (hours to days) to ambient PM
2.5
include mortality, cardiovascular effects, such as altered vasomotor function and hospital admissions and emergency department visits for ischemic heart disease and congestive heart failure, and respiratory effects, such as exacerbation of asthma symptoms in children and hospital admissions and emergency department visits for chronic obstructive pulmonary disease (COPD) and respiratory infections.
33

The ISA notes that long-term exposure to PM
2.5
(months to years) is associated with the development/progression of cardiovascular disease, premature mortality, and respiratory effects, including reduced lung function growth, increased respiratory symptoms, and asthma development.
34

The ISA concludes that the currently available scientific evidence from epidemiologic, controlled human exposure, and toxicological studies supports a causal association between short- and long-term exposures to PM
2.5
and cardiovascular effects and mortality. Furthermore, the ISA concludes that the collective evidence supports likely causal associations between short- and long-term PM
2.5
exposures and respiratory effects. The ISA also concludes that the scientific evidence is suggestive of a causal association for reproductive and developmental effects and cancer, mutagenicity, and genotoxicity and long-term exposure to PM
2.5
.
35

33
U.S. EPA (2009). Integrated Science Assessment for Particulate Matter (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/139F, 2009. Section 2.3.1.1.

34
U.S. EPA (2009). Integrated Science Assessment for Particulate Matter (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/139F, 2009. page 2-12, Sections 7.3.1.1 and 7.3.2.1.

35
U.S. EPA (2009). Integrated Science Assessment for Particulate Matter (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/139F, 2009. Section 2.3.2.

For PM
10-2.5
, the ISA concludes that the current evidence is suggestive of a causal relationship between short-term exposures and cardiovascular effects, such as hospitalization for ischemic heart disease. There is also suggestive evidence of a causal relationship between short-term PM
10-2.5
exposure and mortality and respiratory effects. Data are inadequate to draw conclusions regarding the health effects associated with long-term exposure to PM
10-2.5
.

For ultrafine particulates (UFPs), the ISA further concludes that there is suggestive evidence of a causal relationship between short-term exposures and cardiovascular effects, such as changes in heart rhythm and blood vessel function. It also concludes that there is suggestive evidence of association between short-term exposure to UFPs and respiratory effects. Data are inadequate to draw conclusions regarding the health effects associated with long-term exposure to UFP's.

c. What are the health effects of NO
X
?

Information on the health effects of NO
2
can be found in the EPA Integrated Science Assessment (ISA) for Nitrogen Oxides.
36

The EPA has concluded that the findings of epidemiologic, controlled human exposure, and animal toxicological studies provide evidence that is sufficient to infer a likely causal relationship between respiratory effects and short-term NO
2
exposure. The ISA concludes that the strongest evidence for such a relationship comes from epidemiologic studies of respiratory effects including symptoms, emergency department visits, and hospital admissions. The ISA also draws two broad conclusions regarding airway responsiveness following NO
2
exposure. First, the ISA concludes that NO
2
exposure may enhance the sensitivity to allergen-induced decrements in lung function and increase the allergen-induced airway inflammatory response following 30-minute exposures of asthmatics to NO
2
concentrations as low as 0.26 ppm. In addition, small but significant increases in non-specific airway hyper-responsiveness were reported following 1-hour exposures of asthmatics to 0.1 ppm NO
2
. Second, exposure to NO
2
has been found to enhance the inherent responsiveness of the airway to subsequent nonspecific challenges in controlled human exposure studies of asthmatic subjects. Enhanced airway responsiveness could have important clinical implications for asthmatics since transient increases in airway responsiveness following NO
2
exposure have the potential to increase symptoms and worsen asthma control. Together, the epidemiologic and experimental data sets form a plausible, consistent, and coherent description of a relationship between NO
2
exposures and an array of adverse health effects that range from the onset of respiratory symptoms to hospital admission.

36
U.S. EPA (2008).
Integrated Science Assessment for Oxides of Nitrogen—Health Criteria (Final Report).
EPA/600/R-08/071. Washington, DC: U.S. EPA. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

Although the weight of evidence supporting a causal relationship is somewhat less certain than that associated with respiratory morbidity, NO
2
has also been linked to other health endpoints. These include all-cause (non-accidental) mortality, hospital admissions or emergency department visits for cardiovascular disease, and decrements in lung function growth associated with chronic exposure.

3. Environmental Effects Associated With Exposure to Ozone, PM and NO
X

a. Deposition of Nitrogen

Emissions of NO
X
from aircraft engines contribute to atmospheric deposition of nitrogen in the U.S. Atmospheric deposition of nitrogen contributes to acidification, altering biogeochemistry and affecting animal and plant life in terrestrial and aquatic ecosystems across the U.S. The sensitivity of terrestrial and aquatic ecosystems to acidification from nitrogen deposition is predominantly governed by geology. Prolonged exposure to excess nitrogen deposition in sensitive areas acidifies lakes, rivers and soils. Increased acidity in surface waters creates inhospitable conditions for biota and affects the abundance and nutritional value of preferred prey species, threatening biodiversity and ecosystem function. Over time, acidifying deposition also removes essential nutrients from forest soils, depleting the capacity of soils to neutralize future acid loadings and

negatively affecting forest sustainability. Major effects include a decline in sensitive forest tree species, such as red spruce (
Picea rubens
) and sugar maple (
Acer saccharum
); and a loss of biodiversity of fishes, zooplankton, and macro invertebrates.

In addition to the role nitrogen deposition plays in acidification, nitrogen deposition also leads to nutrient enrichment and altered biogeochemical cycling. In aquatic systems increased nitrogen can alter species assemblages and cause eutrophication. In terrestrial systems nitrogen loading can lead to loss of nitrogen sensitive lichen species, decreased biodiversity of grasslands, meadows and other sensitive habitats, and increased potential for invasive species.

Adverse impacts on soil chemistry and plant life have been observed for areas heavily influenced by atmospheric deposition of nutrients, metals and acid species, resulting in species shifts, loss of biodiversity, forest decline and damage to forest productivity. Across the U.S. there are many terrestrial and aquatic ecosystems that have been identified as particularly sensitive to nitrogen deposition. The most extreme effects resulting from nitrogen deposition on aquatic ecosystems are due to nitrogen enrichment which contributes to “hypoxic” zones devoid of life. Three hypoxia zones of special concern in the U.S. are the zones located in the Gulf of Mexico, the Chesapeake Bay in the mid-Atlantic region, and Long Island Sound, in the northeast U.S.
37

37
U.S. EPA (2008).
Nitrogen Dioxide/Sulfur Dioxide Secondary NAAQS Review: Integrated Science Assessment (ISA).
Washington, DC: U.S. Environmental Protection Agency. Retrieved on March 18, 2009 from
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=180903.

The deposition of airborne particles can reduce the aesthetic appeal of buildings and culturally important articles through soiling, and can contribute directly (or in conjunction with other pollutants) to structural damage by means of corrosion or erosion.
38

Particles affect materials principally by promoting and accelerating the corrosion of metals, by degrading paints, and by deteriorating building materials such as concrete and limestone. Particles contribute to these effects because of their electrolytic, hygroscopic, and acidic properties, and their ability to adsorb corrosive gases (principally sulfur dioxide).

38
U.S. EPA (2005). Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information, OAQPS Staff Paper. Retrieved on April 9, 2009 from
http://www.epa.gov/ttn/naaqs/standards/pm/data/pmstaffpaper_20051221.pdf.

b. Visibility Effects

NO
X
emissions contribute to visibility impairment in the U.S. through the formation of secondary PM
2.5.
39

Visibility impairment is caused by light scattering and absorption by suspended particles and gases. Visibility is important because it has direct significance to people's enjoyment of daily activities in all parts of the country. Individuals value good visibility for the well-being it provides them directly, where they live and work, and in places where they enjoy recreational opportunities. Visibility is also highly valued in significant natural areas, such as national parks and wilderness areas, and special emphasis is given to protecting visibility in these areas. For more information on visibility see the final 2009 PM ISA.
40

39
U.S. EPA (2004).
Air Quality Criteria for Particulate Matter (AQCD).
Volume I Document No. EPA600/P-99/002aF and Volume II Document No. EPA600/P-99/002bF. Washington, DC: U.S. Environmental Protection Agency. Retrieved on March 18, 2009 from
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903.

40
U.S. EPA (2009). Integrated Science Assessment for Particulate Matter (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-08/139F, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

c. Plant and Ecosystem Effects of Ozone

Elevated ozone levels contribute to environmental effects, with impacts to plants and ecosystems being of most concern. Ozone can produce both acute and chronic injury in sensitive species depending on the concentration level and the duration of the exposure. Ozone effects also tend to accumulate over the growing season of the plant, so that even low concentrations experienced for a longer duration have the potential to create chronic stress on vegetation. Ozone damage to plants includes visible injury to leaves and impaired photosynthesis, both of which can lead to reduced plant growth and reproduction, resulting in reduced crop yields, forestry production, and use of sensitive ornamentals in landscaping. In addition, the impairment of photosynthesis, the process by which the plant makes carbohydrates (its source of energy and food), can lead to a subsequent reduction in root growth and carbohydrate storage below ground, resulting in other, more subtle plant and ecosystems impacts. These latter impacts include increased susceptibility of plants to insect attack, disease, harsh weather, interspecies competition and overall decreased plant vigor. The adverse effects of ozone on forest and other natural vegetation can potentially lead to species shifts and loss from the affected ecosystems, resulting in a loss or reduction in associated ecosystem goods and services. Lastly, visible ozone injury to leaves can result in a loss of aesthetic value in areas of special scenic significance like national parks and wilderness areas. The final 2006 Ozone Air Quality Criteria Document presents more detailed information on ozone effects on vegetation and ecosystems.

4. Impacts on Ambient Air Quality

The aircraft NO
X
emission standards we are proposing would impact ambient concentrations of air pollutants. Nationally, levels of PM
2.5
, ozone, and NO
X
are declining.
41

However as of 2008, approximately 127 million people lived in counties that exceeded any NAAQS.
42

These numbers do not include the people living in areas where there is a future risk of failing to maintain or attain the NAAQS.

41
U.S. EPA (2010). Our Nation's Air: Status and Trends through 2008. Office of Air Quality Planning and Standards, Research Triangle Park, NC. Publication No. EPA 454/R-09-002. This document can be accessed electronically at:
http://www.epa.gov/airtrends/2010/.

42
U.S. EPA (2010). Our Nation's Air: Status and Trends through 2008. Office of Air Quality Planning and Standards, Research Triangle Park, NC. Publication No. EPA 454/R-09-002. This document can be accessed electronically at
http://www.epa.gov/airtrends/2010/.

States with nonattainment areas are required to take action to bring those areas into compliance in the future. Based on the final rule designating and classifying 8-hour ozone nonattainment areas for the 1997 standard (69 FR 23951, April 30, 2004), most 8-hour ozone nonattainment areas will be required to attain the ozone NAAQS in the 2007 to 2013 time frame and then maintain the NAAQS thereafter. EPA is reconsidering the 2008 ozone NAAQS. If EPA promulgates different ozone NAAQS as a result of the reconsideration, these standards would replace the 2008 ozone NAAQS and EPA would subsequently designate nonattainment areas for the revised primary ozone NAAQS. The attainment dates for areas designated nonattainment for a revised primary ozone NAAQS could range from 2015 to 2032, depending on the severity of the problem.
43

43
U.S. EPA (2010). Fact Sheet Revisions to Ozone Standards. This document can be accessed electronically at:
http://www.epa.gov/groundlevelozone/pdfs/fs20100106std.pdf.

Areas designated as not attaining the 1997 PM
2.5
NAAQS will need to attain the 1997 standards in the 2010 to 2015 time frame, and then maintain them thereafter. The 2006 24-hour PM
2.5

nonattainment areas will be required to attain the 2006 24-hour PM
2.5
NAAQS in the 2014 to 2019 time frame and then be required to maintain the 2006 24-hour PM
2.5
NAAQS thereafter.

The aircraft engine emission standards being proposed today were approved by ICAO/CAEP and would have an implementation date of 2013. Therefore, the aircraft engine emission reductions that are being proposed today should be useful to states in attaining or maintaining the ozone and PM
2.5
NAAQS.

EPA has already adopted many emission control programs that are expected to reduce ambient ozone and PM
2.5
levels and which will assist in reducing the number of areas that fail to achieve the NAAQS. Even so, our air quality modeling projects that in 2030 as many as 16 counties with a population of almost 35 million may not attain the 2008 ozone standard of 0.075 ppm (75 ppb).
44

In addition, our air quality modeling projects that in 2030 at least 9 counties with a population of almost 28 million may not attain the 1997 annual PM
2.5
standard of 15 μg/m
3
and 26 counties with a population of over 41 million may not attain the 2006 24-hour PM
2.5
standard of 35 μg/m
3
.
45

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 NO
X
ensuring long-term maintenance of the NAAQS.

44
U.S. EPA (2010). Regulatory Impact Analysis: Final Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards. Chapter 7: Environmental and Health Impacts. EPA420-R-10-009.

45
U.S. EPA (2010). Regulatory Impact Analysis: Final Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards. Chapter 7: Environmental and Health Impacts. EPA 420-R-10-009.

There are currently no NO
2
nonattainment areas. However, the NO
2
standards were recently revised and a new 1-hour NO
2
standard was promulgated.
46

Nonattainment area designations for the 1-hour NO
2
standard are expected to be finalized in 2012. These proposed aircraft NO
X
reductions would be useful to states in attaining or maintaining the NO
2
standards.

46
U.S. EPA, “Primary National Ambient Air Quality Standards for Nitrogen Dioxide;” Final Rule, 75 FR 6474, February 9, 2010.

III. Details of the Proposed Rule

We are proposing two different levels or tiers of increasingly more stringent NO
X
emission standards for gas turbofan engines with maximum rated thrusts greater than 26.7 kilonewtons (kN).
47

Each of the tiers would potentially apply to newly-certified engines. Newly-certified aircraft engines are those that would receive a new type certificate after the effective date of the applicable standards. Such engine types or models would not have begun production prior to the effective date of the new requirement.
48

47
The proposed standards would apply to engines used in commercial and noncommercial aviation for which the FAA issues airworthiness certificates,
e.g.,
non-revenue, general aviation service. The vast majority of these engines are used in commercial applications. See section IV.A.2. for more information regarding noncommercial applications.

48
ICAO standards describe newly-certified engines as “* * * engines of a type or model for which the date of manufacture of the first individual production model was after * * *.” the effective date of the emission standards. See ICAO, “Aircraft Engine Emissions,” Annex 16, Volume II, Third Edition, July 2008, Amendment 4 effective on July 20, 2008. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

We are also proposing to apply the first tier of the two tiers of standards to newly-manufactured engines. Newly-manufactured aircraft engines are those that have been previously certified and manufactured in compliance with preexisting standards, and will continue to be produced after the effective date of a new applicable standard. Normally, these newly-manufactured engines would need to comply with the same NO
X
limits as newly-certified engines, but at a later date or cease production.
49

The end of this “phase-in” period for the newly-manufactured engine standards is sometimes referred to a “production cutoff,” for obvious reasons. Again, we are proposing only the first of the two new tiers of NO
X
standards for newly-manufactured engines. These provisions are described in detail below.

49
The standards for newly-manufactured engines are described in general regulatory terms as the date that the type or model was first certified and produced in conformance with specific emission standards, and the date beyond which an individual engine meeting those same requirements cannot be made. So ICAO standards describe newly-manufactured engines as “* * * engines of a type or model for which the date of manufacture of the first individual production model was after * * *.” the effective date of the applicable standards, and “ * * * for which the date of manufacture of the individual engine was on or before * * * ” a specific date that is later than the first effective date of the standards. See ICAO, “Aircraft Engine Emissions,” Annex 16, Volume II, Third Edition, July 2008, Amendment 4 effective on July 20, 2008. Copies of this document can be obtained from the ICAO Web site at
http://www.icao.int.

Five other regulatory features are being proposed in today's action. First, we are proposing to revise provisions addressing certain time-limited flexibilities,
i.e.,
potential exemptions, for newly-manufactured engines that may not be able to comply with the first tier of the proposed new NO
X
standards because of specific technical or economic reasons.
50

Similarly, the proposal includes exception provisions for spare engines. Second, we are proposing to define a derivative engine for emissions certification purposes. The intent of this definition is to distinguish when the emission characteristics of a new turbofan engine model vary substantially from its existing parent engine design, and must show compliance with the emission standards for a newly-certificated engine. Third, we are proposing new CO and NO
X
standards for turbofan engines that are used to propel supersonic aircraft. These standards were adopted by ICAO in the 1980s, but were not previously added to our HC emission standard for these engines. The proposed standards would meet our treaty obligation under the Convention on International Civil Aviation as previously described in section I.B. Fourth, we are proposing several amendments to the emission testing and measurement procedures in our regulations that are intended to implement ICAO's Annex 16 and to incorporate the entire annex in our regulations by reference. Finally, as described in section IV., we are proposing amendments to current regulatory provisions addressing definitions, acronyms and abbreviations, general applicability and requirements, exemptions, and incorporation by reference. These amendments are intended to clarify requirements, make them more consistent with other parts of the program, update the text to be consistent with current standard language conventions, or remove obsolete provisions.

50
These apply only to the Tier 6 NO
X
standards. We are not yet proposing a production cutoff for the Tier 8 NO
X
standard.

As discussed further below, with the exception of the annual reporting requirement described in section III.D., the proposed amendments reflect those changes that were previously adopted by ICAO or that CAEP has recommended for adoption by ICAO in the near future. In this latter case, we are proposing these standards and recommended practices at this time rather than wait until ICAO takes final action to help ensure that our standards, and the FAA's implementing regulations, are adopted in a timely manner once ICAO completes its process. We anticipate that our final standards would generally conform to ICAO's final standards, once adopted.

This would better enable the regulated industry to respond to new, globally harmonized requirements in an orderly manner, which is important given the international nature of the market for the aircraft engines that would be affected by today's proposed rule. It would also avoid continuing the significant lag time that has sometimes occurred between ICAO's adoption of international standards and our adoption of corresponding standards under U.S. law. To the extent ICAO adopts standards that differ from those recommended by CAEP before we issue our final rule, we would then consider whether to make conforming amendments in our final standards, or to issue a supplemental proposal reflecting the amended ICAO standards, if appropriate.

This proposal also is consistent with our authority and obligations under the CAA as described in section I.B. More specifically, the technical feasibility and cost of the proposed emission standards were well documented by our own analyses and CAEP as described later in this section and in section V., Technical Feasibility, Costs, and Emission Benefits. We think that the proposal would provide adequate lead time for the development and application of the requisite technology with appropriate consideration to the cost of compliance. We have consulted with the Department of Transportation through the FAA regarding lead time, noise, safety, and the technical feasibility of the proposed standards. Today's proposal is also consistent with U.S. treaty obligations under the Chicago Convention as described in section I.C., because the proposed requirements are consistent with current ICAO standards or those that we expect ICAO to adopt prior to the promulgation of any final rule.

Except to the extent needed to make our standards conform to ICAO's standards by making them applicable to both commercial and non-commercial engines, we are not proposing revised exhaust emission standards for HC, CO, or smoke, which would remain in effect as currently promulgated. All engines subject to the proposed new NO
X
standards would also continue to be subject to the existing HC, CO, and smoke standards. It is worth emphasizing that although we are proposing to include these existing HC, CO, and smoke standards in a new section 87.23, which would also contain the proposed Tier 6 and Tier 8 NO
X
standards, we are not actually proposing new standards, since under the current form of part 87 these HC, CO and smoke standards would already continue to apply to new engine types subject to future revised NO
X
standards.

We are proposing to adopt a new naming convention in this preamble and the regulatory text to more easily distinguish between the proposed tiers of increasingly more stringent NO
X
emission standards. This convention is also consistent with the numeric identifier that CAEP uses to differentiate the CAEP work cycle that produces new NO
X
standards. (The CAEP naming convention is described in section I.E.) As a result, the first tier of proposed NO
X
standards, which are consistent with CAEP/6, will be referred to as Tier 6 in the remainder of today's notice. The second tier of proposed standards will be referred to as Tier 8, which is consistent with CAEP/8. We are also incorporating the new naming convention in the regulations for the existing NO
X
emission standards,
i.e.,
Tier 0, Tier 2, and Tier 4. There is no material change to the existing NO
X
standards themselves, except to the extent that upon the effectiveness of a final rule reflecting today's proposal the existing NO
X
standards would be superseded by Tier 6 standards.

We acknowledge that this new naming convention is a change from the past practice of not describing aircraft engine emission standards as tiers. However, we believe the new naming scheme is a valuable tool that makes referring to individual NO
X
standards much easier. It is also similar to the terminology we use for other mobile source sectors that are subject to environmental regulation and for which standards have become more stringent or have otherwise been amended over time.

A. NO
X
Standards for Newly-Certified Engines

We are proposing two different tiers of increasingly stringent NO
X
standards. These standards would apply for all for newly-certified turbofan aircraft engines with maximum rated thrusts greater than 26.7 kN.
51

(See section III.B. for a discussion of how these standards would apply for newly-manufactured engines that are not considered to be newly certified.) The numerical value of the applicable standard for an individual engine model is defined by the engine's thrust level and pressure ratio. Simply stated, the pressure ratio is a ratio of the air pressure entering the engine to the air pressure at the entrance to the combustor,
i.e.,
after the air has passed through the compressor section of the engine. Each of the proposed tiers is described separately below.

51
There are no gaseous emission standards,
e.g.,
NO
X
, for gas turbine engines with maximum rated thrusts equal to or less than 26.7 kN. These engines are, however, subject to smoke and fuel venting standards.

1. Tier 6 NO
X
Standards for Newly-Certified Engines

This first tier of proposed standards is equivalent to the CAEP/6 NO
X
limits that were already adopted by ICAO and became internationally effective after December 31, 2007. Given that aircraft turbofan engines are international commodities, engine manufacturers have already introduced engine models after that date that demonstrate compliance with these international standards, or are already planning to do so for upcoming engine designs. Based on this, and on our evaluation of the necessary lead time, we are proposing that this tier of standards take effect immediately upon the effective date of our final regulations.

The basic form of the NO
X
standards for turbofan engines is different for higher- and lower-rated thrust engines. Higher output engines are defined as having rated thrusts equal to or greater than 89 kN, while lower output engines are defined as having rated thrusts less than 89 kN but greater than 26.7 kN. The proposed Tier 6 NO
X
standards for each of these power grouping are described separately below.

a. Numerical Emission Limits for Higher Thrust Engines

The proposed Tier 6 NO
X
standards for newly-certified gas turbine engines with rated thrusts of 89 kN or more are differentiated by pressure ratio as shown below.

• For engines with a pressure ratio of 30 or less: g/kN rated output = 16.72 + (1.4080 * engine pressure ratio).

• For engines with a pressure ratio of more than 30 but less than 82.6: g/kN rated output = −1.04 + (2.0 * engine pressure ratio).

• For engines with a pressure ratio of 82.6 or more: g/kN rated output = 32 + (1.6 * engine pressure ratio).

The corresponding CAEP/6 standards were derived by CAEP using the following methodology:

• Make the CAEP/6 standard 12 percent more stringent than the CAEP/4 requirement at a pressure ratio of 30;

• Retain the same percent reduction,
i.e.,
12 percent, for pressure ratios below 30;

• Retain the slope of the CAEP/4 standard for pressure ratios of 30 to 62.5 for the CAEP/6 pressure ratios of 30 to 82.6;

• Retain the slope of the CAEP/4 standard for pressure ratios equal to or

greater than 62.5 for the CAEP/6 pressure ratios at or above 82.6.
52

52
Reverting to the CAEP/4 slope at a pressure ratio of 82.6 prevents the CAEP/6 standard from otherwise intersecting the older CAEP/2 standard at this point and thereby actually making CAEP/6 less stringent than CAEP/2. It has no practical effect because current engines or anticipated engine designs do not utilize such high pressure ratios. Presently, there are no current engines with pressure ratios above approximately 42.

The resulting proposed Tier 6 NO
X
standards for these higher thrust engines are presented in Figure 1 along with the most recently adopted existing EPA NO
X
standards, which were based on CAEP/4, for comparison.

EP27JY11.000

As a matter of convention, the relative stringency from one CAEP standard to another is expressed relative to a pressure ratio of 30, because the percentage reduction is usually inconsistent across all of the possible pressure ratios, which otherwise makes a simple comparison difficult. Using that convention, the proposed Tier 6 standards (CAEP/6) are referred to as being 12 percent more stringent than the existing EPA NO
X
Tier 4 standards (CAEP/4). The relative stringency can also be illustrated at other pressure ratios. At pressure ratios less than 30 the reductions are also 12 percent. At pressure ratios above 30, however, the percent reduction decreases as the pressure ratio is increased. Based on the figure, the percent reduction for current technology engines ranges from about 8 to 12 percent.

b. Numerical Emission Limits for Lower Thrust Engines

The proposed Tier 6 NO
X
standards for newly-certified gas turbine engines with rated thrusts between 26.7 and less than 89.0 kN are differentiated by both pressure ratio and rated thrust as shown below.

• For engines with a pressure ratio of 30 or less:

g/kN rated output = 38.5486 + (1.6823 * engine pressure ratio) − (0.2453 * kN rated thrust) − (0.00308 * engine pressure ratio * kN rated thrust).

• For engines with a pressure ratio of more than 30 but less than 82.6:

g/kN rated output = 46.1504 + (1.4285 * engine pressure ratio) − (0.5298 * kN rated thrust) + (0.00642 * engine pressure ratio * kN rated thrust).

In developing the corresponding NO
X
standards for low thrust engines, CAEP recognized the technical challenges that physically smaller-sized engines represent relative to incorporating some of the lowest NO
X
technology, which is otherwise available to their larger counterparts. These technical difficulties are well documented and increase progressively as size is reduced (from around 89 kN).
53

For example, the relatively small combustor
54

space and section height of these engines creates constraints on the use of low NO
X
fuel-staged combustor concepts which inherently require the availability of greater flow path cross-sectional area than conventional combustors. Also, fuel-staged combustors need more fuel injectors, and this need is not compatible with the relatively smaller total fuel flows of lower thrust engines. (Reductions in fuel flow per nozzle are difficult to attain without having clogging problems due to the small sizes of the fuel metering ports.) In addition, lower thrust engine combustors have an inherently greater liner surface-to-combustion volume ratio, and this requires increased wall cooling air flow. Thus, less air will be available to obtain acceptable turbine inlet temperature distribution and for emissions control.
55

With these technological constraints in mind, CAEP fashioned the CAEP/6 NO
X
standards across the range of thrusts represented by low-thrust engines to become comparatively less stringent,

i.e.,
CAEP/6 relative to CAEP/4, as the rated output and physical size of the engines decrease. We agree with this approach.

53
ICAO/CAEP, “Report of Third Meeting, Montreal, Quebec, December 5-15, 1995,” Document 9675, CAEP/3. A copy of this paper can be found in Docket EPA-HQ-OAR-2010-0687.

54
The combustor is a chamber where a mixture of fuel and air is burned to form very hot, expanding gases. As these gases move through the combustion chamber, the walls of the combustor are cooled with dilution air to prevent thermal damage. Dilution air is also used to tailor the gas' temperature profile as it exits the combustor so that the final temperatures will not exceed the allowable limit at the turbine inlet.

55
ICAO, “Combined Report of the Certification and Technology Subgroups,” section 2.3.6.1, CAEP Working Group 3 (Emissions). Presented by the Chairman of the Technology Subgroup, Third Meeting, Bonn, Germany, June 1995. A copy of this paper can be found in Docket EPA-HQ-OAR-2010-0687.

As mentioned, the proposed Tier 6 standards depend on an individual engine's rated thrust and pressure ratio. With two variables in the calculation, the standards cannot be represented in a simple figure,
i.e.,
no single line graph showing the standards for all engines within the thrust range is possible as it was for higher thrust engines. Regardless of this complexity, however, some general observations are useful to characterize the proposed Tier 6 NO
X
standards for lower thrust engines based on the engine size versus technological challenge described in the previous paragraph.

Comparing the proposed lower and higher thrust standards at 89 kN, which is the demarcation point between the two sets of standards, shows that the standards for lower thrust engines are numerically equivalent to the limit for higher thrust engines at each pressure ratio. This is as expected because the engine sizes and ability to incorporate low-NO
X
technologies are the same at 89.0 kN delineation point.

Again focusing only on 89 kN engines, the proposed Tier 6 standards represent a 12 percent reduction from the existing EPA Tier 4 (CAEP/4 based standards) for pressure ratios of 30 or less as shown below in Figure 2. This includes the region represented by almost all current engine designs. At higher pressure ratios, the relative numerical reduction is progressively less because the slope of the two standards is essentially the same.

EP27JY11.001

At other thrust ratings the percent reduction between the proposed Tier 6 and existing EPA NO
X
standards at any pressure ratio becomes progressively smaller as thrust decreases. This is illustrated in Figure 3 for a pressure ratio of 30. This pressure ratio was chosen for the example because, as before, the relative stringency of CAEP NO
X
standards is generally compared at this point as a matter of convention. As shown in the figure for current engines, the reduction ranges from 12 percent at the upper end of the thrust range to 0 percent at the lower end of the range. The pattern is similar for the other pressure ratios. Only the actual numerical value for percentage reduction at 89 kN, as shown on the far right of the figure, may vary by pressure ratio, as described at the beginning of this paragraph. However, in the region of pressure ratios represented by today's engines, the results are identical to those shown in the figure,
i.e.,
a 12 percent reduction at 89 kN decreasing to 0 percent at 26.7 kN.

EP27JY11.002

2. Tier 8 NO
X
Standards for Newly-Certified Engines

The second tier of proposed standards,
i.e.,
Tier 8, are equivalent to the NO
X
limits that were most recently recommended at CAEP/8 in February 2010 for adoption by ICAO.
56

The CAEP/8 recommended standards have a recommended effective date after December 31, 2013. As discussed further in section V. of today's notice, we agree with CAEP that this provides engine manufacturers with adequate lead time to respond to these more stringent NO
X
standards considering the technical feasibility and cost associated with the requirements. Therefore, we are proposing that this tier of proposed standards would take effect on January 1, 2014, provided ICAO adopts CAEP/8's recommended standards and effective date. If ICAO adopts different standards or a different effective date, we would evaluate whether to similarly adopt correspondingly different standards and effective dates, or seek further public comment before doing so.

56
CAEP/7 did not adopt new aircraft engine NO
X
standards.

As with the Tier 6 NO
X
standards, the basic form of the Tier 8 standards for turbofan engines is different for higher- and lower-rated thrust engines. Higher output engines are defined as having rated thrusts equal to or greater than 89 kN, while lower output engines are defined as having rated thrusts less than 89 kN but greater than 26.7 kN. The longer-term standards for each of these power grouping are described separately below.

a. Numerical Emission Limits for Higher Thrust Engines

The proposed Tier 8 NO
X
standards for newly-certified turbofan engines with rated thrusts of 89 N or more are differentiated by pressure ratio as shown below.

• For engines with a pressure ratio of 30 or less: g/kN rated output = 7.88 + (1.4080* engine pressure ratio).

• For engines with a pressure ratio of more than 30 but less than 104.7: g/kN rated output = − 9.88+ (2.0 * engine pressure ratio).

• For engines with a pressure ratio of 104.7 or more: g/kN rated output = 32 + (1.6 * engine pressure ratio).

The corresponding CAEP/8 standards were derived by CAEP using the following methodology:

• Make the CAEP/8 standard 15 percent more stringent than the CAEP/6 requirement at a pressure ratio of 30;

• Retain the slope of the CAEP/6 standard for pressure ratios below 30;

• Retain the slope of the CAEP/6 standard for pressure ratios of 30 to 82.6 for the CAEP/8 pressure ratios of 30 to 104.7;

• Retain the slope of the CAEP/6 standard for pressure ratios above 82.6 for the CAEP/8 pressure ratios equal to or greater than 104.7.
57

57
Reverting to the CAEP/6 slope at a pressure ratio of 104.7 prevents the CAEP/8 standard from otherwise intersecting the older CAEP/2 standard at this point and thereby actually making CAEP/8 less stringent than CAEP/2. It has no practical value because current engines or anticipated engine designs do not utilize such high pressure ratios. Presently, there are no current engines with pressure ratios above approximately 42.

The resulting proposed Tier 8 NO
X
standards for these higher thrust engines are presented in Figure 4 along with the proposed Tier 6 standards for comparison.

EP27JY11.003

As noted previously, as a matter of convention the relative stringency from one CAEP standard to another is generally expressed relative to a pressure ratio of 30. Using that convention, the proposed Tier 8 standards (CAEP/8) are referred to as being 15 percent more stringent than the proposed Tier 6 NO
X
standards (CAEP/6). The relative stringency can also be illustrated at other pressure ratios. At pressure ratios less than 30 the reductions increase. At pressure ratios above 30, however, the percent reduction decreases. Based on the figure, the percent reduction for current technology engines ranges from about 11 to 19 percent.

b. Numerical Emission Limits for Lower Thrust Engines

The proposed Tier 8 NO
X
standards for newly-certified gas turbine engines with rated thrusts between 26.7 but less than 89.0 kN are differentiated by both pressure ratio and rated thrust as shown below.

• For engines with a pressure ratio of 30 or less:

g/kN rated output = 40.052 + (1.5681 * engine pressure ratio) − (0.3615 * kN rated thrust) − (0.0018 * engine pressure ratio * kN rated thrust).

• For engines with a pressure ratio of more than 30 but less than 104.7:

g/kN rated output = 41.9435 + (1.505 * engine pressure ratio) − (0.55823 * kN rated thrust) + (0.005562 * engine pressure ratio * kN rated thrust).

In developing the corresponding CAEP/8 NO
X
standards for low thrust engines, CAEP recognized the technical challenges that physically smaller-sized engines represent relative to incorporating some of the lowest NO
X
technology, which is otherwise available to their larger counterparts. These technical difficulties were described in the previous section for the proposed Tier 6 low-thrust engine standards.

Also as previously described, no single line graph showing the standards for all engines within the thrust range is possible as it was for higher thrust engines, because the equations have two variables. However, some general observations are useful to characterize the proposed Tier 8 NO
X
standards for lower thrust engines based on the engine size versus technological challenge described in the previous paragraph. First, the proposed Tier 8 NO
X
standards for lower thrust engines are numerically equivalent to the limit for higher thrust engines across all pressure ratios at the highest rating of 89 kN, where the engine sizes and ability to incorporated low-NO
X
technologies are comparable. This same characteristic was observed for the proposed Tier 6 standards. Second, as shown below in Figure 5 for 89 kN engines, at this thrust rating the proposed Tier 8 standards represents a 15 percent reduction from the proposed Tier 6 standards for a pressure ratio of 30. However, within the region of pressure ratios for all current engine designs, the reductions range from 19 to 23 percent.

ep27jy11.004

Third, at other thrust ratings the percent reduction between the proposed Tier 6 and Tier 8 standards at any pressure ratio becomes progressively smaller as thrust decreases. This is illustrated in Figure 6 for a pressure ratio of 30, following the convention described above. Also as shown in the figure for current engines, the reduction ranges from 15 percent at the upper end of the thrust range to 5 percent at the lower end of the range. While not depicted in a figure, the pattern is similar for the other pressure ratios. However, the actual numerical values for percentage reductions at both ends of the thrust range,
i.e.,
26.7 to 89 kN, may vary by pressure ratio. In the region of pressure ratios represented by today's engines, the results are identical to those shown in Figure 6 at 26.7 kN,
i.e.,
a 5 percent reduction at all pressure ratios for that thrust rating. However, percent reductions increase linearly up to a maximum 23 percent reduction for 89 kN engines with pressure ratios of about 15.

ep27jy11.005

B. Application of the Tier 6 NO
X
Standards to Newly-Manufactured Engines

This section describes our proposal to apply the proposed Tier 6 NO
X
standards to newly-manufactured engines, and our proposed amended temporary flexibilities for newly-manufactured engines that may have significant problems complying with these requirements. Also, consistent with CAEP/8, we are not proposing to apply the Tier 8 NO
X
standards to newly-manufactured engines at this time. This section concludes with a description of future efforts to examine such a possibility.

1. Phase-In of the Tier 6 NO
X
Standards for Newly-Manufactured Engines

As described above, the proposed Tier 6 NO
X
standards would apply to all engine types or models that receive a
new
type certificate after the effective date of the final rule. We are also proposing to phase-in these same NO
X
limits for newly-manufactured engines for engine models (and their derivatives for emissions certification purposes) that were originally certified to less stringent requirements (
i.e.,
Tier 2 or Tier 4) and were already being produced for installation on new aircraft prior to the effective date of the final rule.
58

As a result, manufacturers would need to bring newly-manufactured engines of these previously certified models into compliance with the applicable Tier 6 standards by a future date or cease production of those engine models.
59

As we discussed and described in our analysis of the need for a CAEP 6 production cutoff during the CAEP process, establishing a date certain for compliance with any emission standard is foundational to its basic design and purpose and helps to ensure that the full benefits of newer, more stringent requirements will be achieved in a reasonable time.
60

We are, however, proposing certain limited flexibilities for engines that cannot be made compliant because of specific technical or economic reasons, as discussed later in this section.

58
The requirement that newly-manufactured engines must meet the CAEP 6 NO
X
standard by a date certain applies only to engines that are intended to be installed on all new airframes. It would not apply to engines produced as “spares,” which are intended to be installed on existing airframes as replacements for maintenance or other reasons. See section III.B.2. for more information about new and spare engines.

59
After this date the production of any noncompliant engines would cease because the FAA would discontinue issuing an airworthiness approval tag (FAA Form 8130-3) to these engines.

60
ICAO, Committee on Aviation Environmental Protection (CAEP), Eight Meeting, Montreal, 1 to 12 February 2010, Agenda 2: Review of Technical Proposals Relating to Aircraft Engine Emissions, Adoption of Production Cutoff for Emission Standards, WP/56, Presented by the United States, December 12, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

The proposed effective date of January 1, 2013
61

for the newly-manufactured engine standards is consistent with the expected market demand for these previously certified engine types. Historically, engine manufacturers have often responded to the adoption of more stringent NO
X
standards by bringing older engine types into compliance with the newer requirements well before the required date in anticipation of the likely market demand, or planning for the orderly withdrawal of these engines from the marketplace. Information developed during the ICAO process in 2008 and 2009
62 63 64

and our more recent discussions with manufacturers indicate that: (1) All but a few models are already compliant with CAEP/6 standards, (2) nearly without exception, all current production models will meet the CAEP/6 requirements by the 2011 time frame, and (3) any noncompliant models will be phased out of production because of low market demand.

61
The proposed regulatory text specifies that engine models certified at or below the Tier 4 NO
X
standards may be produced through December 31, 2012 without meeting the Tier 6 NO
X
standards. Therefore, the effective date of the proposed standards for newly-manufactured engines is effectively January 1, 2013.

62
ICAO, Committee on Aviation Environmental Protection (CAEP), Steering Group Meeting, Salvador, Brazil, 22 to 26 June 2009, Agenda 6: Emissions Technical-WG3, Production Cutoffs and Associated Flexibilities for ICAO Engine Emission Standards, WP/39, Presented by U.S. Representative, August 6, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

63
ICAO, Committee on Aviation Environmental Protection (CAEP), Steering Group Meeting, Salvador, Brazil, 22 to 26 June 2009, Agenda Item 3: Forecasting and Economic Analysis Support Group (FESG), CAEP/6 NO
X
Production Cutoff Cost Analysis, WP/39, Presented by the FESG NO
X
Stringency Task Group, February 6, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

64
ICAO, Committee on Aviation Environmental Protection (CAEP), Steering Group Meeting, Seattle, 22 to 26 September 2008, Agenda Item 3: Forecasting and Economic Analysis Support Group (FESG), Production Cutoff for NO
X
Standards, WP/6, Presented by the FESG Rapporteurs, April 9, 2008. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

We think that the proposed five-year phase-in period from ICAO's effective date of the CAEP/6 standards (corresponding to our proposed Tier 6 NO
X
standards) for newly-certified engines is adequate for manufacturers and their customers to respond to the new requirements without disrupting their future planning and purchasing decisions.
65 66

This phase-in period for applying the Tier 6 NO
X
standards to newly-manufactured engines is identical to the date for this same requirement that CAEP/8 has recommended to ICAO for adoption.
67

Therefore, we are proposing that all engines newly-manufactured after December 31, 2012 must comply with the Tier 6 NO
X
standards. Again, if ICAO ultimately adopts a production cutoff date that differs from this proposed date, we would evaluate whether to adopt a correspondingly different date in the final rule or to seek further public comment on the change.

65
The ICAO CAEP/6 NO
X
standards became effective after December 31, 2007.

66
This period of time is also consistent with the phase-in period associated with previous ICAO standards. CAEP's predecessor, the Committee on Aircraft Engines Emissions, established the first international emission standards with an effective date four years after adoption,
i.e.,
effectively a four year phase-in. CAEP2 included a phase-in period of 4 years for newly-manufactured engines.

67
We expect that ICAO will formally adopt the CAEP/8 recommendations with an effective date in November 2011, which is well before the projected effective date of our final rule.

2. Exemption and Exceptions From the Tier 6 Production Cutoff

In conjunction with the implementation of the proposed Tier 6 NO
X
standards, we are proposing provisions which would allow engine manufacturers to request an exemption exception from meeting the Tier 6 NO
X
standards for newly-manufactured engines. These proposed provisions would replace existing provisions addressing exemptions, currently promulgated in section 87.7 of our aircraft engine regulations. (Any exemptions previously issued under section 87.7 would not be affected by the proposed revisions.) This section of the preamble describes these proposed exemption and exception provisions,
i.e.,
exemptions for engines installed in new aircraft and exceptions for spare engines used in existing aircraft for maintenance purposes. These provisions have largely been crafted to be consistent with exemption provisions in the ICAO Environmental Technical Manual (ETM).
68 69

The provisions of the ETM guidance were developed in the context of the CAEP/6 NO
X

production cutoff deliberations leading up to the CAEP/8 meeting in February 2010.

68
ICAO, “Committee on Aviation Environmental Protection (CAEP), Report of the Eighth Meeting, Montreal, February 1-12, 2010,” CAEP/8-WP/80. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

69
Note that EPA has submitted a paper to amend the exemption provisions included in this ETM to be consistent with this proposed rule. See ICAO, “Newly Produced Engine Exemptions for CAEP/6 NO
X
Production Cutoff,” CAEP9_WG3-CTG-2_IP01, September 23, 2010. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

While we are proposing to revise our regulations, the process for evaluating any request for an exemption,
i.e.,
petition, and any final decision on its disposition would be unchanged. In this regard, the FAA is the process owner under its enforcement authority contained in section 232 of the Clean Air Act.
70

The FAA must consult with EPA in evaluating the merits of the request, and the EPA must formally concur with any decision regarding the granting or denial of the request.

70
EPA formally transferred the responsibility and authority for the evaluation of requests for exemptions from the emission standards to the Secretary of Transportation (DOT). See “Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures;” Final Rule, 47 FR 58462, December 30, 1982.

Under the existing regulations, the FAA, with EPA concurrence, may exempt low-production volume engines from being fully compliant with the emission standards. Several such short-term exemptions were granted in the 1980s when emission standards were first applied. These exemptions have since expired, and requests for new exemptions under those provisions have not been submitted. We have determined that these provisions, which were adopted in conjunction with revised emission standards in 1982, are no longer of any utility.
71

Therefore, we are proposing to delete these provisions to avoid confusion.

71
U.S.EPA, “Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures,” Final Rule, 47 FR 58462, December 30, 1982.

We are also proposing to delete the existing provisions for temporary exemptions based on flights for short durations and infrequent intervals. These provisions are not necessary because our standards apply to aircraft certificated by the FAA, and the FAA does not address in the certification process whether an aircraft will be used for short durations or infrequent intervals. Hence, the provisions are of no utility.

The current regulations also provide for permanent exemptions based on consideration of the certain factors specified in section 87.7(c). We are proposing to replace these provisions with new regulatory text consistent with the ETM that would provide for two separate types of permanent exemptions: Exceptions for spare engines and exemptions for engines on new aircraft. These are summarized below. (See § 87.50 of the proposed regulations for additional details on these exemptions.)

Finally, we are deleting the time-limited exemption provisions for in-use engines that are contained in section 87.7(d). These provisions, which were intended for when the standards of sections 87.11(a), 87.31(a), and 87.31(c) first took effect, are now obsolete.

a. New Provisions for Spare Engines

This proposed allowance, which is an exception to the standards as described below, is intended to allow the production and sale of a newly-manufactured engine for installation on an in-service aircraft,
i.e.,
a “spare engine.” It would
not
allow for installing such an engine on a new aircraft. Spare engines are produced from time to time in order to keep an aircraft in revenue service when the existing in-service engine must be removed for maintenance or replacement purposes as needed. Otherwise removing these aircraft from active service would be very expensive and logistically difficult. Also, under our proposed regulations, there would be no adverse environmental effect from allowing the use of a spare engine as a direct replacement for an existing engine, because a spare could be used only when the emissions of the spare engine are equal to or lower than those of the engine it is replacing, for all pollutants. Manufacturers would not be required to obtain FAA or EPA approval before producing spare engines. However, they would have to submit information about the production of spare engines in an annual report to the EPA. Because manufacturers would not be required to seek or obtain formal approval to produce spare engines, this allowance is being referred to as an “exception” rather than an “exemption”. This terminology would be consistent with current FAA regulations. The permanent record for each engine excepted under this provision would need to indicate that the engine is an excepted spare engine and the engine itself would need to be labeled as “EXCEPTED SPARE.” in accordance with FAA marking requirements of 14 CFR.

Exceptions for spare engines are not addressed in the existing regulations because there is no production cutoff for the current Tier 4 NO
X
standards. Thus manufacturers have been allowed to continue production of older engine designs under type certificates first issued before the Tier 4 standards took effect (
e.g.,
Tier 2). However, our proposal to apply a Tier 6 NO
X
production cutoff to all newly- manufactured engines means that if we did not also propose this exception process, manufacturers would be prohibited from producing Tier 4 spare engines under the existing type certificates. We see no reason to change our policy of allowing manufacturers to produce new engines for use as spares. The proposed regulatory provisions would allow this practice to continue.

Under the proposed regulations, engines meeting the requirements for spare engines could be produced and enter into commerce without prior approval from EPA or FAA. (This allowance would also need to be promulgated by the FAA.) It is important to note that while spare engines would be excepted from the Tier 6 NO
X
standards being proposed today, they would still need to be produced under an FAA type certificate. (This FAA oversight would serve the same role as the exemption approval step envisioned by ICAO in its ETM language for spare engines.) We would expect little or no additional burden for manufacturers, since we are not proposing new restrictions, monitoring, recordkeeping, or reporting requirements other than the end of year report. When combined with the proposed prohibition against using spare engines to replace lower emitting engines, this program will ensure that using a spare engine would not increase emissions, but would at the same time allow the availability of spares for maintenance or replacement as needed.

b. New Provisions for Engines Installed in New Aircraft

The primary purpose of allowing limited continued production of Tier 4 engines is to provide for an orderly implementation of the Tier 6 NO
X
production cutoff. It addresses engines reaching the end of their production cycles in the time frame when new emission standards take effect. The typical production cycle would have annual production volumes ramp up quickly, remain at relatively large volumes for several or many years, and then fall off over a few more years. When new emission standards are adopted in the middle of a production cycle to take effect a few years later, manufacturers generally devote technical resources to bring into compliance those engine models expected to be produced in large numbers in the time frame when the new standards are in effect. In contrast, they may plan not to invest in upgrading the emissions of engine models that would be very near the end of their normal production cycles when compliance with the new standards becomes required. The actual length and shape of this tail of production volumes can be affected by factors not fully

within the engine manufacturers' control,
e.g.,
unexpected market demand. Thus, exemptions may be justified if a manufacturer does not complete the production cycle before the production cutoff date and projected production volumes are not adequate to justify investing the necessary resources to reduce emissions or there are other technological issues.

Furthermore, in certain exceptional circumstances exemptions may also be appropriate. These are “hardship” situations that may arise as a result of unforeseen technical or economic circumstances or events beyond control of the manufacturer. For example, this could vary from unexpected problems with technology upgrade programs to labor disruptions or natural events disrupting production or parts availability.

Our regulations currently address these kinds of situations in section 87.7(c), entitled “Exemptions for New Engines in Other Categories.” Today's proposed amendments would replace this provision with a new set of provisions addressing exemptions for new engines. We invite public comment on any other ways to address the need for flexibilities in the above circumstances.

i. Time Frame and Scope

The proposed regulations would allow manufacturers to request an exemption for engines not meeting the Tier 6 NO
X
standards so they may be installed in new aircraft. If granted, the exemption would allow manufacturers to produce a limited number of newly-manufactured engines, in a time period beginning after December 31, 2012 and going through December 31, 2016. The time period for any given approved exemption could be shorter depending on the specifics of the application but could not be longer. This exemption would be limited to NO
X
emissions from engines that are covered by a valid type certificate issued by FAA. The engines would be required to meet all other applicable requirements. More specifically, an engine exempted from the Tier 6 NO
X
standards would need to be covered by a previously issued type certificate showing compliance with the Tier 4 NO
X
standards,
72

as well as the current HC, CO, fuel venting, and smoke standards.

72
Engines certified only for compliance with earlier NO
X
standards would not be eligible for exemptions. This is also consistent with the exemption language in the ICAO ETM. Note that where such engines have emissions actually meeting the Tier 4 NO
X
standard, they may be recertified to the Tier 4 standards, but only before the effective date of the proposed regulations.

ii. Production Limit

In the proposed new regulatory language for exemptions, we are proposing to use the general exemption language for exhaust emission standards contained in part 87.7(c) of the current regulations. That language states that the Secretary of the Department of Transportation determines, with the EPA Administrator's concurrence, when the emission standards do not apply to engines based on a number of specific considerations such as adverse economic impact on the engine manufacturer, aircraft manufacturer, or airline industry; in addition to the effects on public health and welfare. We are also proposing to make this language applicable only to the Tier 6 production cutoff, which is consistent with the ETM guidance. No need has been identified to apply such exemption language to the other regulated exhaust pollutants,
i.e.,
hydrocarbons and carbon monoxide. The emission standards for those pollutant species have remained unchanged for nearly three decades and present no technical issues for modern turbofan engines.
73

If new emission standards for these pollutants are considered in the future, the potential need for exemption provisions will also be assessed at that time.

73
For example, the hydrocarbon exhaust emission standards were adopted on December 30, 1982. See 47 FR 58462.

Each request for exemption would be evaluated on a case-by-case basis, using the information provided by the applicant and any other relevant information that is available to FAA and EPA at the time. Any approved exemption would include a specific limit on the number of such engines based on that information and is not defined on a basis such as type certificate. (See section III.B.b.iii. for a description of what the request must contain.) The intent, of course, would be to exempt the minimum number of engines that can be clearly justified, including a consideration of the public health and welfare effects associated with the exemptions.

We acknowledge that our proposal differs from the language contained in the current ICAO ETM guidance, which would nominally allow up to 75 engines per type certificate.
74

To understand why we find that a deviation from the ETM is appropriate in this instance, the following explanation regarding the historical perspective on the development of the ETM provision is helpful.

74
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”.

Prior to the CAEP/8 meeting in February 2010, ICAO had no specific provisions regarding exemptions. The only language regarding exemptions was contained in Annex 16 Volume II section 2.1.1 which rather generically stated that:

In considering exemptions, certificating authorities should take into account the probable number of such engines that will be produced and their impact on the environment. When such an exemption is granted, the certificating authority should consider imposing a time limit on the production of such engines for installation on new aircraft or on existing aircraft as spares.

When ICAO/CAEP began considering a production cut-off for the CAEP/6 NO
X
standard, there was a consensus among the participants in the technical working group that more specific provisions were needed with respect to potential exemptions from that requirement.
75

The provisions would help support an orderly transition in the implementation of the production cut-off. Toward that end, the group consulted periodically over several months to craft provisions addressing number, time limit, and emission levels (impact on the environment). The deliberations were complicated by the fact that the language in Annex 16 simultaneously addressed both engines for new production aircraft and spare engines for existing aircraft.
76

75
ICAO, “Committee on Aviation Environmental Protection (CAEP), Report of the 6th Meeting,” CAEP/8-WG3-WP7-03, Presented by the Rapporteurs, London, UK, April 1-3, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

76
ICAO, “Committee on Aviation Environmental Protection (CAEP), Draft Minutes of ETM/Annex 16 Ad-Hoc Group Telecon,” May 26, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

For new production engines, agreement was reached relatively quickly that exemptions should be available for up to four years after the production cut-off becomes effective, and that any engine model for which an exemption was requested should at a minimum comply with the emission standards for all other regulated pollutants, including the CAEP/4 NO
X
requirements. Similarly, it was readily agreed in the technical working group that there would be no limit on the number of spare engines because these units would essentially be installed in

place of in-use engines that are removed for maintenance or other reasons.
77

77
ICAO, “Committee on Aviation Environmental Protection (CAEP), Report of the Eighth Meeting, Montreal, February 1-12, 2010,” CAEP/8-WP/80. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

However, discussions and deliberations were more difficult with regard to the number of potential exemptions for engines for new production aircraft. This difficulty stemmed from the fact that the ICAO Emissions Data Bank identified 20 unique engine models/sub models that could have been affected by the production cutoff. Those models had valid type certificates and, therefore, were considered to be “in production.”
78

During further discussions the engine manufacturers clarified that most of these 20 were not in active production because the airlines normally purchase new aircraft with engines meeting the latest emission standards. Nonetheless, it was stated that if the demand existed, 14 of these 20 models could potentially be produced under the exemption provisions since they had valid type certificates and met the previously mentioned exemption emission requirements.
79 80 81 82

After much deliberation, the technical working group settled on a value of 75 engines per type certificate over the four years for the ICAO ETM guidance based on the information available at the time.
83

78
U.S. EPA, “Simplified Working Copy of ICAO EDB, Issue 16A,” memorandum from Glenn Passavant, Assessment and Standards Division, Office of Air Quality and Transportation, March 25, 2010. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

79
ICAO, “Committee on Aviation Environmental Protection (CAEP), Response to EPA Paper 14 and 16,” WG-3 Flimsy 6-2, ICCAIA, London, UK, April 13, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

80
ICAO, “Committee on Aviation Environmental Protection (CAEP), Production Cut-Off for Engine NO
X
Standards,” CAEP-SG/20082-WP/6, Presented by FESG, September 4, 2008. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

81
ICAO, “Committee on Aviation Environmental Protection (CAEP), CAEP/6 NO
X
Productin Cut-Off Analysis,” CAEP-SB/20093-IP/19, Presented by FESG NO
X
Stringency Task Group, June 2, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

82
ICAO, “Committee on Aviation Environmental Protection (CAEP), Production Cut-Off and Associated Flexibilities for ICAO Engine Emission Standards,” CAEP-SG/20093-WP/39, U.S. EPA, June 8, 2009. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

83
ICAO, “Committee on Aviation Environmental Protection (CAEP), Report of the Eighth Meeting, Montreal, February 1-12, 2010,” CAEP/8-WP-80, Appendix B. A copy of this document is in docket number EPA-HQ-OAR-2010-0687.

This value and the maximum number of engines it could represent were of immediate concern to EPA. First, in a hypothetical worst case, it represented the potential for over 1000 exempt engines (500 aircraft) to enter the fleet over this time period based on the information above. Assuming two engines per aircraft, this is essentially equivalent to the number of civil aircraft shipped in a single year.
84

Second, it was unclear to us if that number of potential exemptions,
i.e.,
75 per type certificate, was necessary. Third, from a broader perspective, while EPA regulations normally include hardship type provisions, it is not normal for EPA to include specific transitional exemptions of this magnitude in our regulations.

84
See Table 5 of the most recent AIA statistical report available at
http://www.aia-aerospace.org/assets/Table
5.pdf.

As we continued efforts to identify how many exemptions might potentially be needed for the CAEP/6 production cutoff, three new pieces of information became available during the development of this proposed rule that were not considered during the deliberations leading up to the ICAO decision for the ETM guidance. First, a review of previously unavailable information on past exemption requests to FAA under the previous less specific ICAO language indicated that of the eight requests were granted since 1983, only three involved exemptions during standards transition (two related to smoke for turboprop engines and one related to NO
X
for a turbofan engine). These three exemption petitions in combination ultimately affected less than 50 engines.
85

Second, engine manufacturers indicated individually that the potential need for exemptions was not as large as EPA understood during the technical working group deliberations, and that absent unforeseen events, a much smaller value was workable on a per manufacturer basis as opposed to a per type certificate basis.
86 87 88

Third, our most recent discussions with the engine manufacturers that are directly affected by the proposed Tier 6 NO
X
standards,
i.e.,
CAEP/6 standards, concluded that only one or two engine models may be candidates for exemptions. Those discussions also concluded that the likely potential number of justifiable exemptions would be less than 75 in total.
89

Considering all o

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2011-17660. Public record. Not legal advice.