[Federal Register Volume 77, Number 117 (Monday, June 18, 2012)]
[Rules and Regulations]
[Pages 36341-36386]
[FR Doc No: 2012-13828]

Vol. 77

Monday,

No. 117

June 18, 2012

Part II

Environmental Protection Agency

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40 CFR Parts 87 and 1068

Control of Air Pollution From Aircraft and Aircraft Engines; Emission
Standards and Test Procedures; Final Rule

Federal Register / Vol. 77 , No. 117 / Monday, June 18, 2012 / Rules
and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 87 and 1068

[EPA-HQ-OAR-2010-0687; FRL-9678-1]
RIN 2060-AO70

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is adopting several new aircraft engine emission standards
for oxides of nitrogen (NOX), compliance flexibilities, and
other regulatory requirements for aircraft turbofan or turbojet engines
with rated thrusts greater than 26.7 kilonewtons (kN). We also are
adopting certain other requirements for gas turbine engines that are
subject to exhaust emission standards as follows. First, we are
clarifying 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 establishing 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 establishing amendments
to aircraft engine test and emissions measurement procedures. EPA
actively participated in the United Nations' International Civil
Aviation Organization (ICAO) proceedings in which most of these
requirements were first developed. These regulatory requirements have
largely been adopted or are actively under consideration by its member
states. By adopting such similar standards, therefore, the United
States maintains consistency with these international efforts.

DATES: These final rules are effective on July 18, 2012. The
incorporation by reference of certain publications listed in this
regulation is approved by the Director of the Federal Register as of
July 18, 2012.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2010-0687. All documents in the docket are listed on the
http://www.regulations.gov Web site. Although listed in the index, some
information is not publicly available, e.g., confidential business
information or other information whose disclosure is restricted by
statute. Certain other material, such as copyrighted material, is not
placed on the Internet and will be publicly available only in hard copy
form. Publicly available docket materials are available electronically
through http://www.regulations.gov or in hard copy at the 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<PHONE_NUMBER>, and the telephone
number for the Air Docket is<PHONE_NUMBER>.

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:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>;
email address<EMAIL_ADDRESS>
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:

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                                                                                Examples of potentially
                  Category                    NAICS \a\ Codes     SIC \b\ Codes          affected entities
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Industry...................................             336412               3724  Manufacturers of new aircraft
                                                                                engines.
Industry...................................             336411               3721  Manufacturers of new
                                                                                aircraft.
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\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. Executive Summary
II. Overview and Background
    A. Contents of the Final Rule
    B. EPA's Authority and 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
III. Why is EPA taking this action?
    A. Inventory Contribution
    B. Health, Environmental and Air Quality Impacts
    1. Background on Ozone, PM and NOX
    a. What is ozone?
    b. What is particulate matter?
    c. What is NOX?
    2. Health Effects Associated With Exposure to Ozone, PM and
NOX
    a. What are the health effects of ozone?
    b. What are the health effects of PM?
    c. What are the health effects of NOX?
    3. Environmental Effects Associated With Exposure to Ozone, PM
and NOX
    a. Deposition of Nitrogen
    b. Visibility Effects
    c. Plant and Ecosystem Effects of Ozone
    4. Impacts on Ambient Air Quality
IV. Details of the Final Rule
    A. NOX Standards for Newly-Certified Engines
    1. Tier 6 NOX Standards for Newly-Certified Engines
    a. Numerical Emission Limits for Higher Thrust Engines
    b. Numerical Emission Limits for Lower Thrust Engines
    2. Tier 8 NOX Standards for Newly-Certified Engines
    a. Numerical Emission Limits for Higher Thrust Engines
    b. Numerical Emission Limits for Lower Thrust Engines
    B. Application of NOX Standards for Newly-
Manufactured Engines
    1. Phase-In of the Tier 6 NOX Standards for Newly-
Manufactured Engines
    2. Carryover of Previously Generated Emission Data
    3. 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
    v. Low-Volume, Time-Limited Transitional Exception Program
    c. Voluntary Emission Offsets
    4. Potential Phase-In of New Tier 8 NOX Standards for
Newly-Manufactured Engines

    C. Application of Standards for Derivative Engines
    D. Annual Reporting Requirement
    E. 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
V. 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
VI. Technical Feasibility and Cost Impacts
VII. Consultation With FAA
VIII. Public Participation
IX. Statutory Provisions and Legal Authority
X. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review, and
Executive Order 13563: Improving Regulation and Regulatory 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
    K. Congressional Review Act
    L. Executive Order 13609: Promoting International Regulatory
Cooperation

I. Executive Summary

A. Purpose of the Regulatory Action

    The primary purpose of this rule is to adopt new oxides of nitrogen
(NOX) emission standards for aircraft engines with rated
thrusts greater than 26.7 kN thrust. These are mostly commercial
passenger and freighter aircraft in common use at airports across the
U.S. It does not include engines used on military aircraft.
NOX is strongly correlated with NO2, for which
EPA has established National Ambient Air Quality Standards (NAAQS),
i.e., a criteria pollutant, and it is an important precursor gas in the
formation of tropospheric ozone and secondary particulate matter which
are common air pollutants in urban areas where airports are located.
Currently, approximately 154 million people live in areas designated
nonattainment for one or more of the current NAAQS. This rule will
allow us to enforce in the U.S. the emission standards adopted by ICAO,
and will be useful to states in attaining or maintaining the ozone,
PM2.5, and NO2 NAAQS standards. This rule also
contains several provisions to facilitate the implementation of EPA's
aircraft engine emission regulations and related requirements. It is
also important to note that adoption of the provisions in this rule
meets U.S. treaty obligations under the Chicago Convention of 1944 by
aligning our regulations with those in the International Civil Aviation
Organization Annex 16, Volume II (adopted in 2010) that the U.S. helped
to develop and support as part of the international process. This rule
is being implemented under the authority provided in section 231 of the
Clean Air Act (42 U.S.C. 7571), which 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.

B. Summary of Major Provisions of the Regulatory Action

    The rule contains six major provisions. The first two provisions
are new NOX emission standards for newly certified-engine
models. The first standards, Tier 6, take effect when this rule becomes
effective. These represent approximately a 12 percent reduction from
current Tier 4 levels. They were actually adopted by ICAO in 2005 with
an implementation date in 2008. The second standards, Tier 8, were
adopted by ICAO in 2008 and take effect in 2014. These represent
approximately a 15 percent reduction from Tier 6 levels. As noted
above, both tiers of emission standards are needed to address local air
quality concerns (NAAQS) and to meet U.S. treaty obligations under the
Chicago Convention. The third major provision is a production cut-off
for newly-manufactured engines (as opposed to newly-certified engines)
which basically requires that after December 31, 2012 all newly-
manufactured engines must meet at least Tier 6 NOX emission
standards. This is also needed to meet our obligations under the
Chicago Convention. The production cut-off is needed to ensure that the
emission reductions envisioned by the emission standards are achieved
on new production engines. The fourth major provision is related to
potential exemptions or exceptions to the production cut-off
requirement. These include revised provisions allowing manufacturers to
request that FAA in consultation with EPA grant exemptions from the
production cut-off for a designated number of engines within a
prescribed time frame. These also include a low-volume, time-limited
exception provision that will exclude several engines from the
production cutoff. Both of these provisions help to assure an orderly
transition to the new standards for engines needing more time to comply
or for a few engines at the end of their production life. Finally, the
rule includes a set of provisions which may be considered as minor if
viewed separately, but collectively are important in upgrading EPA's
regulations by incorporating some related agreements from our ICAO
process and clarifying and improving existing provisions. Examples of
this include special provisions for spare engines, provisions related
to derivative engine models, test procedure specifications and
reporting requirements. These changes are important for an effective
implementation of the new requirements, and in many cases are also
needed to meet our obligations under the Chicago Convention.

C. Costs and Benefits

    This is not an economically significant regulatory action. Aircraft
engines are international commodities used on aircraft manufactured and
sold around the world. When developing new engine models manufacturers
not only consider current emission requirements but also try to
anticipate the stringency of future standards and respond
appropriately. Engine manufacturers participated in the deliberations
leading up to ICAO decisions on the aircraft engine NOX
emission standards and after the ICAO decisions they incorporated
engine technology changes as needed to meet the new ICAO requirements.
This helps to ensure the world wide acceptability of their products.
Essentially all of these changes are now complete. Thus, while there is
some cost to a manufacturer for responding to the new ICAO provisions,
there is no significant further direct cost to the manufacturers
created by EPA's adopting the requirements into U.S regulations. In
fact, it is likely that our adopting these requirements facilitates the
acceptance of U.S. type certificates by aircraft manufacturers and
airlines around the world.

II. Overview and Background

    This section summarizes the major provisions of the final 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. Contents of the Final Rule

    We are adopting 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 establishing
two new tiers of more stringent emission standards for oxides of
nitrogen (NOX).\2\ The standards apply differently to two
classes of these engines, i.e., ``newly-certified engines'' and
``newly-manufactured engines.'' The newly-certified engine standards
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 apply
to aircraft engines that were previously certified and manufactured in
compliance with preexisting standards, and they require manufacturers
to either comply with the newer standards by a specified future date or
cease production of the affected engine models. Newly-manufactured
engine standards are also sometimes referred to as ``production
cutoff'' standards. Second, we are adopting 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 NOX standards
because of specific technical or economic reasons.\3\
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    \1\ Turbofan and turbojet engines will be collectively referred
to as turbofan engines hereafter for convenience.
    \2\ As previously mentioned, these new NOX standards
are identical to requirements established by ICAO. The stringency of
any new emission standard is selected based on an assessment of the
technical feasibility, cost, and environmental benefit of potential
requirements. The NOX standards we are promulgating today
will not affect fuel economy or have any practical effect on
CO2 emissions. (See International Civil Aviation
Organization (ICAO), ``Committee on Aviation Environmental
Protection (CAEP), Eighth Meeting, Montreal, 1 to 12 February 2010,
CAEP/8 NOX Stringency Cost-Benefit Analysis Demonstration
Using APMT-IMPACTS,'' CAEP/8-IP/30, December 1, 2010. A copy of this
document is in docket number EPA-HQ-OAR-2010-0687.)
    \3\ These exemption or exception provisions are conceptually the
same as the ICAO exemption provisions and provide the same
regulatory flexibilities to all engine manufacturers.
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    We are also making a number of additional changes that would apply
to a wider range of aircraft gas turbine engines \4\ than those that
would be subject to the new emission standards.\5\ First, we are
defining the meaning of 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 establishing new reporting requirements for
manufacturers that produce gas turbine engines subject to any exhaust
emission standard. This will provide us with timely and consistent
emission data and other information that is necessary to conduct
emission inventory and air quality analyses and develop appropriate
public policy for the aviation sector. Specifically, reports are
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.\6\ Third, we are adopting
minor amendments to the test and measurement procedures for aircraft
engines. Finally, as described in section IV, we are making minor
amendments to regulator provisions addressing definitions, acronyms and
abbreviations, general applicability and requirements, exemptions, and
incorporation by reference.
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    \4\ 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).
    \5\ This includes turbofan and turbojet engines less than 26.7
kN thrust and all turboprop engines that are subject to any emission
standard, e.g., smoke.
    \6\ As discussed further in section III.D., the voluntary
emission data report to ICAO does not include turbofans at or below
26.7 kN or turboprops subject to any emission standard.
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    Most of these new regulatory requirements have already been adopted
by the United Nation's International Civil Aviation Organization
(ICAO). The requirements contained in this final rule 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 D.C. 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 (D.C. 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 ensure
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. Sec.
7573. Section VI of today's final rule further discusses our
coordination with DOT through the FAA.\7\ It also describes DOT's
responsibility under the CAA to enforce the aircraft emission standards
established by EPA.
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    \7\ The functions of the Secretary of Transportation under part
B of title II of the Clean Air Act (Sec. Sec.  231-234, 42 U.S.C.
7571-7574) have been delegated to the Administrator of the FAA. 49
CFR 1.47(g).
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C. Interaction With the International Community

    We began regulating the air pollution 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.'' \8\
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 191 participating member States of
ICAO.9 10
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    \8\ 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 www.icao.int.
    \9\ Members of ICAO's Assembly are generally termed member
States or contracting States. These terms are used interchangeably
throughout this preamble.
    \10\ There are currently 191 Contracting States according to
ICAO Web site located at www.icao.int.
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    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.\11\ 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.\12\ 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.\13\ However,
if a nation sets tighter standards than ICAO, air carriers not based in
that nation would only be required to comply with ICAO standards or
more stringent standards imposed by their own nations, if applicable.
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    \11\ ICAO, ``Convention on International Civil Aviation,''
Article 87, Ninth Edition, Document 7300/9, 2006. Copies of this
document can be obtained from the ICAO Web site located at
www.icao.int/icaonet/arch/doc/7300/7300_9ed.pdf.
    \12\ 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
www.icao.int/icaonet/arch/doc/7300/7300_9ed.pdf.
    \13\ 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
www.icao.int/icaonet/arch/doc/7300/7300_9ed.pdf.
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    ICAO'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 committees whose contributing members include
atmospheric, economic, aviation, environmental, and other professionals
interested in aviation and environmental protection. At CAEP meetings,
the United States is represented by the FAA, which plays an active role
at these meetings.\14\ 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).15 16
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    \14\ Pursuant to the President's memorandum of August 11, 1960
(and related Executive Order No. 10883 from 1960), the Interagency
Group on International Aviation (IGIA) was established to facilitate
coordinated recommendations to the Secretary of State on issues
pertaining to international aviation. The DOT/FAA is the chair of
IGIA, and as such, the FAA represents the U.S. on environmental
matters at CAEP.
    \15\ 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.
    \16\ CAEP develops new emission standards based on an assessment
of the technical feasibility, cost, and environmental benefit of
potential requirements.
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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.\17\
Since that time, we have occasionally revised those regulations. Two of
these revisions are most pertinent to today's final rule. 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.\18\ 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 NOX 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) \19\ 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 NOX emission standards for newly-
certified commercial turbofan engines.\20\ 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 (D.C. Cir. 2007).
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    \17\ U.S. EPA, ``Emission Standards and Test Procedures for
Aircraft;'' Final Rule, 38 FR 19088, July 17, 1973.
    \18\ 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
NOX 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 section IV.A.2. of today's notice, we are
expanding the scope of that finding and of our standards pursuant to
section 231(a)(2)(A) of the Clean Air Act to include such emissions
from both commercial and non-commercial aircraft engines based on
the physical and operational similarities between commercial and
noncommercial civilian aircraft and to bring our standards into full
alignment with ICAO's.
    \19\ This does not mean that in 2005 we promulgated requirements
for the re-certification or retrofit of existing in-use engines.
    \20\ 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.
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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.\21\ These standards limited aircraft engine
emissions of HC, CO, and NOX. In 1994, ICAO adopted a CAEP/2
proposal to tighten the original NOX standard by 20 percent
and amend the test procedures.\22\ 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 NOX 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 previously certified, newly-manufactured engines
unlike the CAEP/2 standards). In 2004, CAEP/6 recommended a 12 percent
NOX reduction, which ICAO approved in 2005.23 24
The CAEP/6 standards applied to new engine designs (newly-certified
models) certified after December 31, 2007. At the most recent meeting,
CAEP/8 recommended a further tightening of the NOX standards
by 15 percent for newly-certified engines.25 26 The
Committee also recommended that the CAEP/6 standards be applied to
newly-manufactured engines. ICAO approved these recommendations in
2011.\27\
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    \21\ ICAO, Foreword of ``Aircraft Engine Emissions,''
International Standards and Recommended Practices, Environmental
Protection, Annex 16, Volume II, Third Edition, July 2008. Copies of
this document can be obtained from the ICAO Web site at
www.icao.int.
    \22\ 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.
    \23\ CAEP/5 did not address new aircraft engine emission
standards.
    \24\ 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
www.icao.int.
    \25\ CAEP/7 did not address new aircraft engine emission
standards.
    \26\ 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.
    \27\ ICAO, ``Aircraft Engine Emissions,'' Annex 16, Volume II,
Third Edition, July 2008, Amendment 7 effective on July 18, 2011.
Copies of this document can be obtained from the ICAO Web site at
www.icao.int.
---------------------------------------------------------------------------

III. 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
NOX, a precursor to the formation of tropospheric ozone and
secondary PM.\28\ Most commercial airports are located in urbanized
areas \29\ and many urbanized areas have ambient pollutant levels above
the National Ambient Air Quality Standards (NAAQS) for ozone and fine
particulate matter (PM2.5) (i.e., they are in nonattainment
for ozone and PM2.5).\30\ This section discusses the
contribution of aircraft engines used in commercial service with rated
thrusts greater than 26.7kN to the national NOX emissions
inventory and to NOX emission inventories in selected ozone
and PM2.5 nonattainment areas, the potential effect of
NOX emissions in the upper atmosphere on ground level
PM2.5 in addition to the health and welfare impacts of
NOX and PM emissions.
---------------------------------------------------------------------------

    \28\ Ground-level ozone, the main ingredient in smog, is formed
by complex chemical reactions of volatile organic compounds (VOC)
and NOX in the presence of heat and sunlight. Standards
that reduce NOX emissions will help address ambient ozone
levels. They can also help reduce particulate matter (PM) levels as
NOX emissions can also be part of the secondary formation
of PM. See Section II.B below.
    \29\ According to Airport Council International--North America
and similar FAA databases, most commercial operations occur at
airports that are in or near large cities or urbanized areas. There
are about 130 commercial airports in 78 ozone and fine particulate
nonattainment areas (based on the nonattainment areas status of
2008). There are about 325 commercial airports in the U.S.
    \30\ For a current list of nonattainment areas see: http://www.epa.gov/oar/oaqps/greenbk/index.html.
---------------------------------------------------------------------------

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.
    In this section, we will discuss NOX emission
inventories for commercial turbine-engine aircraft, both nationally and
for selected ozone and PM2.5 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).\31\ 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 LTO operations contributed about 97 thousand tons
to the national NOX inventory.\32\ A summary of the national
inventory of LTO NOX emissions is shown in Table 1.
---------------------------------------------------------------------------

    \31\ ``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.
    \32\ The cumulative LTO NOX reduction associated with
the new NOX standards is projected to be about 100,000
tons from 2014 to 2030 (2014 is the implementation date of the CAEP/
8 NOX standards). See ``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 NOX 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 NOX inventory is approximately 7.7
percent.\33\ It is also worth noting that these LTO emissions are more
localized in that they occur near airports, which are mostly within
urban areas.
---------------------------------------------------------------------------

    \33\ U.S. EPA, ``Comparison of Aircraft LTO and Full Flight
NOX Emissions to Total Mobile Source NOX
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 NOX Emissions From Commercial Aircraft
------------------------------------------------------------------------
                                                         2008 Total NOX
                  Aircraft category                     (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 NOX 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 NAAs with airports which had high commercial
traffic volumes were identified. Second, the 25 NAAs with the largest
population were identified. These lists were combined. However, there
was some overlap, and this led to a total of 40 NAAs being identified
for the study.\34\ These NAAs collectively include 200 airports,
accounting for about 70 percent of commercial air traffic operations.
---------------------------------------------------------------------------

    \34\ 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.
---------------------------------------------------------------------------

    Of the 40 NAAs originally studied by ERG as previously described,
we identified the 30 areas that were in nonattainment for ozone or
PM2.5 as of March 30, 2012.\35\ Current (2008) and projected
(2020) NOX emissions for these 30 ozone and PM2.5
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 2.36 37 38 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 NOX emissions from
other mobile source categories results in the growth of the relative
contribution of aircraft LTO emissions to mobile source NOX
emissions in NAAs.
---------------------------------------------------------------------------

    \35\ For a current list of nonattainment areas see: http://www.epa.gov/oar/oaqps/greenbk/index.html.
    \36\ U.S. EPA, ``Relative Contribution of Aircraft to Total
Mobile Source NOX 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.
    \37\ U.S. EPA, ``Addendum to `Relative Contribution of Aircraft
to Total Mobile Source NOX 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.
    \38\ U.S. EPA, ``Update to `Relative Contribution of Aircraft to
Total Mobile Source NOX 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, April 30, 2012.

                     Table 2--NOX Emissions in Selected Ozone and PM2.5 Nonattainment Areas
----------------------------------------------------------------------------------------------------------------
                                                                              2008 Aircraft      2020 Aircraft
                   Nonattainment area                      2008 Total NOX   percent of mobile  percent of mobile
                                                               (tons)           source NOX         source NOX
----------------------------------------------------------------------------------------------------------------
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
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
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
Milwaukee-Racine, WI...................................                557                0.9                3.2
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
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
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 NOX
inventories will also increase.

                          Table 3--Current and Projected Commercial Aircraft Operations
----------------------------------------------------------------------------------------------------------------
                                                                                Total increase in
                                         Air carrier        Commuter/air     Total commercial      commercial
                Year                      operations      taxi operations       operations      operations over
                                          (millions)         (millions)         (millions)       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.

B. Health, Environmental and Air Quality Impacts

    NOX emissions from aircraft and other mobile and
stationary sources contribute to the formation of ozone. In addition,
NOX emissions at low altitude also react in the atmosphere
to form secondary fine particulate matter (PM2.5),
particularly ammonium nitrate. In the following sections we discuss the
adverse health and welfare effects associated with NOX
emissions, in addition to the current and projected levels of ozone and
PM across the country. The ICAO NOX standards with which we
are aligning will help reduce ambient ozone and secondary PM levels and
thus will help areas with airports achieve or maintain attainment with
the National Ambient Air Quality Standards (NAAQS).\39\
---------------------------------------------------------------------------

    \39\ The discussion of PM health and welfare effects throughout
this notice relates exclusively to the effects of the NOX
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 NOX
a. What is ozone?
    Ground-level ozone pollution is typically formed through reactions
involving VOC and NOX 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.\40\ 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 and its precursors can be
transported hundreds of miles downwind from precursor emissions,
resulting in elevated ozone levels even in areas with low local VOC or
NOX emissions.
---------------------------------------------------------------------------

    \40\ 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 PM2.5 because the NOX
emitted by aircraft engines can react in the atmosphere to form
nitrate, a component of PM2.5. 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). The current PM
NAAQS uses PM2.5 as the indicator for fine particles (with
PM2.5 generally referring to particles with a nominal mean
aerodynamic diameter less than or equal to 2.5 micrometers ([micro]m)),
and use PM10 as the indicator for purposes of regulating the
coarse fraction of PM10 (referred to as thoracic coarse
particles or coarse-fraction particles; generally including particles
with a nominal mean aerodynamic diameter greater than 2.5 [micro]m and
less than or equal to 10 [micro]m, or PM10-2.5). Ultrafine
particles are a subset of fine particles, generally less than 100
nanometers (0.1 [mu]m) in diameter.
    Fine particles are produced primarily by combustion processes and
by transformations of gaseous emissions (e.g., SOX,
NOX and VOC) in the atmosphere. The chemical and physical
properties of PM2.5 may vary greatly with time, region,
meteorology, and source category. Thus, PM2.5 may include a
complex mixture of different components 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 NOX?
    Nitrogen dioxide (NO2) is a member of the NOX
family of gases. Most NO2 is formed in the air from the
oxidation of nitric oxide (NO) emitted when fuel is burned at a high
temperature. NO2 and its gas phase oxidation products can
dissolve in water droplets and further oxidize to form nitric acid
which reacts with ammonia to form nitrates, an important component of
ambient PM. NOX and VOC are the two major precursors of
ozone. The health effects of ozone, ambient PM and NOX are
covered in section II.B.2.
2. Health Effects Associated With Exposure to Ozone, PM and
NOX
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 and 2007 Staff
Paper.41 42 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 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.\43\ 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.
---------------------------------------------------------------------------

    \41\ 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.
    \42\ 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.
    \43\ 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).\44\
The ISA summarizes health effects evidence associated with both short-
term and long-term exposures to PM2.5, PM10-2.5,
and ultrafine particles.
---------------------------------------------------------------------------

    \44\ 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 PM2.5 include
mortality, cardiovascular effects, such as altered vasomotor function
and myocardial ischemia, 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 and respiratory
infections.\45\ The ISA notes that long-term exposure (months to years)
to PM2.5 is associated with the development/progression of
cardiovascular disease, premature mortality, and respiratory effects,
including reduced lung function growth in children, increased
respiratory symptoms, and asthma development.\46\ 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 PM2.5
and cardiovascular effects and premature mortality. Furthermore, the
ISA concludes that the collective evidence supports likely causal
associations between short- and long-term PM2.5 exposures
and respiratory effects. The ISA also concludes that the scientific
evidence is suggestive of a causal association for reproductive and
developmental effects including respiratory-related infant mortality
and cancer, mutagenicity, and genotoxicity and long-term exposure to
PM2.5.\47\
---------------------------------------------------------------------------

    \45\ 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 <IP_ADDRESS>.
    \46\ 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
<IP_ADDRESS> and <IP_ADDRESS>.
    \47\ 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 PM10-2.5, the ISA concludes that the current
evidence is suggestive of a causal relationship between short-term
exposures and premature mortality, cardiovascular effects, and
respiratory effects. Data are inadequate to draw conclusions regarding
the health effects associated with long-term exposure to
PM10-2.5.
    For ultrafine particles, the ISA 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 ultrafine particles and
respiratory effects. Data are inadequate to draw conclusions regarding
the health effects associated with long-term exposure to ultrafine
particles.
c. What are the health effects of NOX?
    Information on the health effects of NO2 can be found in
the EPA Integrated Science Assessment (ISA) for Nitrogen Oxides.\48\
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 NO2 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 NO2
exposure. First, the ISA concludes that NO2 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 NO2
concentrations as low as 0.26 ppm. Second, exposure to NO2
has been found to enhance the inherent responsiveness of the airway to
subsequent nonspecific challenges in controlled human exposure studies
of asthmatic subjects. Small but significant increases in non-specific
airway hyperresponsiveness were reported following 1-hour exposures of
asthmatics to 0.1 ppm NO2. Enhanced airway responsiveness
could have important clinical implications for asthmatics since
transient increases in airway responsiveness following NO2
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 NO2 exposures and an array of adverse
health effects that range from the onset of respiratory symptoms to
hospital admission.
---------------------------------------------------------------------------

    \48\ 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,
NO2 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
NOX
a. Deposition of Nitrogen
    Emissions of NOX 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 United States. 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 damage to forest productivity and
reductions in ecosystem services. Potential impacts also include
adverse effects to human health through ingestion of contaminated
vegetation or livestock (as in the case for dioxin deposition),
reduction in crop yield, and limited use of land due to contamination.
    Atmospheric deposition of pollutants 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.\49\ Atmospheric
deposition may 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).
---------------------------------------------------------------------------

    \49\ 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
    NOX emissions contribute to visibility impairment in the
U.S. through the formation of secondary PM2.5.\50\
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.\51\
---------------------------------------------------------------------------

    \50\ 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.
    \51\ 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 NOX emission standards we are promulgating
would affect ambient concentrations of air pollutants. Nationally,
levels of PM2.5, ozone, and NOX are
declining.\52\ However as of March 30, 2012, over 15 million people
live in areas designated nonattainment for one or more of the current
NAAQS.\53\ These numbers do not include the people living in areas
where there is a future risk of failing to maintain or attain the
NAAQS.
---------------------------------------------------------------------------

    \52\ 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/.
    \53\ U.S. EPA, 2012. http://www.epa.gov/oar/oaqps/greenbk/index.html
---------------------------------------------------------------------------

    States with ozone nonattainment areas are required to take action
to bring

those areas into attainment. The attainment date assigned to an ozone
nonattainment area is based on the area's classification. Most ozone
nonattainment areas are required to attain the 1997 8-hour ozone NAAQS
in the 2007 to 2013 time frame and then to maintain it thereafter.\54\
We anticipate designating areas for the 2008 ozone standards in late
spring 2012; thus, the attainment dates for areas designated
nonattainment for the 2008 8-hour ozone NAAQS would likely be in the
2015 to 2032 timeframe, depending on the severity of the problem in
each area.\55\
---------------------------------------------------------------------------

    \54\ The Los Angeles South Coast Air Basin 8-hour ozone
nonattainment area and the San Joaquin Valley Air Basin 8-hour ozone
nonattainment area are designated as extreme and will have to attain
before June 15, 2024. The Sacramento, Coachella Valley and Houston
8-hour ozone nonattainment areas are designated as severe and will
have to attain by June 15, 2019. In addition, the Western Mojave 8-
hour ozone nonattainment area has requested to be reclassified as
severe. This request has not yet been acted on.
    \55\ U.S. EPA, 2012. Proposed Rule--Implementation of the 2008
National Ambient Air Quality Standards for Ozone: Nonattainment Area
Classifications Approach, Attainment Deadlines and Revocation of the
1997 Ozone Standards for Transportation Conformity Purposes. (77 FR
8107, February 14, 2012).
---------------------------------------------------------------------------

    Areas designated as not attaining the 1997 PM2.5 NAAQS
will need to attain the 1997 standards in the 2010 to 2015 time frame,
and then maintain compliance with them thereafter. The 2006 24-hour
PM2.5 nonattainment areas will be required to attain the
2006 24-hour PM2.5 NAAQS in the 2014 to 2019 time frame and
then be required to maintain the 2006 24-hour PM2.5 NAAQS
thereafter.
    EPA has already adopted many emission control programs that are
expected to reduce ambient ozone and PM2.5 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 10 counties with a population of over 30 million may not attain the
2008 ozone standard of 0.075 ppm (75 ppb) without additional
controls.\56\ In addition, our air quality modeling projects that in
2030 at least four counties with a population of nearly 7 million may
not attain the 1997 annual PM2.5 standard of 15 [mu]g/m\3\
and 22 counties with a population of over 33 million may not attain the
2006 24-hour PM2.5 standard of 35 [mu]g/m\3\ without
additional controls.57 58 These numbers do not account for
those areas that are close to (e.g., within 10 percent of) the
standards. These areas, although not violating the standards, would
also benefit from any reductions in NOX ensuring long-term
maintenance of the NAAQS.
---------------------------------------------------------------------------

    \56\ U.S. EPA (2010). Regulatory Impact Analysis: Final
Rulemaking To Establish Greenhouse Gas Emission Standards and Fuel
Efficiency Standards for Medium- and Heavy-Duty Engines and
Vehicles. Chapter 8: Health and Environmental Impacts. EPA 420-R-11-
901.
    \57\ U.S. EPA (2010). Regulatory Impact Analysis: Final
Rulemaking To Establish Greenhouse Gas Emission Standards and Fuel
Efficiency Standards for Medium- and Heavy-Duty Engines and
Vehicles. Chapter 8: Health and Environmental Impacts. EPA 420-R-11-
901.
    \58\ These figures are based on the results of EPA computer
modeling, which is not affected by the upcoming 2008 ozone NAAQS
nonattainment designations.
---------------------------------------------------------------------------

    In summary, the aircraft NOX reductions resulting from
these new aircraft engine emission standards will be useful to states
in attaining or maintaining the ozone, PM2.5, and
NO2 NAAQS standards.

IV. Details of the Final Rule

    The following is a description of the regulations being adopted in
this final rule, with any changes from the proposal also noted. The
descriptions also include our response to the most significant comments
received on the proposal. A full summary of the comments and our
responses are contained in the response to comments document for the
rule that is available in the public docket for this action.\59\
---------------------------------------------------------------------------

    \59\ U.S. Environmental Protection Agency, ``Summary and
Analysis of Comments: Control of Air Pollution From Aircraft and
Aircraft Engines,'' Office of Transportation and Air Quality, EPA-
420-R-12-011, May 2012. A copy of this document is in docket number
EPA-HQ-OAR-2010-0687.
---------------------------------------------------------------------------

    We are establishing two different levels or ``tiers'' of
increasingly more stringent NOX emission standards for gas
turbofan engines with maximum rated thrusts greater than 26.7
kilonewtons (kN).\60\ Each of the tiers 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.\61\
---------------------------------------------------------------------------

    \60\ The standards will 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.
    \61\ 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. Copies of this document can
be obtained from the ICAO Web site at www.icao.int. The term ``first
individual production model'' means the first engine ever produced
of a unique model or type.
---------------------------------------------------------------------------

    We are also requiring newly-manufactured engines to comply with the
first tier of the two tiers of standards. 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 must comply with the same
NOX limits as newly-certified engines, but at a later date
or cease production.\62\ The end of this ``phase-in'' period for the
newly-manufactured engine standards is sometimes referred to as a
``production cutoff.''. Again, we are adopting only the first of the
two new tiers of NOX standards for newly-manufactured
engines. These provisions are described in detail below.
---------------------------------------------------------------------------

    \62\ 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 www.icao.int.
---------------------------------------------------------------------------

    Five other regulatory features are being established in this final
rule. First, we are revising provisions for 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 new
NOX standards because of specific technical or economic
reasons.\63\ Second, we are defining ``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 establishing new CO and
NOX 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. Promulgating these standards meets our treaty obligation under
the Convention on International Civil Aviation as previously described

in section I.C. Fourth, we are making several changes 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
amending the current regulatory provisions that address 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.
---------------------------------------------------------------------------

    \63\ These apply only to the first tier of NOX
standards. We are not adopting a production cutoff for the second
tier of standards.
---------------------------------------------------------------------------

    As discussed further below, with the exception of the annual
reporting requirement described in section III.D, the amendments
reflect those changes that were previously adopted by ICAO.
    This final rule 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 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 final rule
provides 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 new standards. Today's final rule is also consistent
with U.S. treaty obligations under the Chicago Convention as described
in section I.C., because the requirements are consistent with current
ICAO standards.
    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 revising exhaust emission standards for
HC, CO, or smoke. All engines subject to the new NOX
standards would also continue to be subject to the existing HC, CO, and
smoke standards. It is worth emphasizing that although we are including
these existing HC, CO, and smoke standards in a new section 87.23,
which would also contain the new Tier 6 and Tier 8 NOX
standards, we are not actually adopting new standards for these three
pollutants, 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 NOX standards.
    As discussed above, we are adopting a new naming convention in this
preamble and the regulatory text to more easily distinguish between the
tiers of increasingly more stringent NOX emission standards.
This convention is also consistent with the numeric identifier that
CAEP uses to differentiate the CAEP work cycle that produces new
NOX standards. (The CAEP naming convention is described in
section I.E.) As a result, the first tier of NOX standards,
which correspond to CAEP/6, are referred to as Tier 6 in the remainder
of today's notice. The second tier of standards is referred to as Tier
8, which correspond to CAEP/8. We are also incorporating the new naming
convention in the regulations for the existing NOX emission
standards, i.e., Tier 0, Tier 2, and Tier 4. There is no material
change to the existing NOX standards themselves, except to
the extent that when today's final rule becomes effective, the existing
NOX 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 NOX 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. NOX Standards for Newly-Certified Engines

    We are adopting two different tiers of increasingly stringent
NOX standards. These standards would apply for all for
newly-certified turbofan aircraft engines with maximum rated thrusts
greater than 26.7 kN.\64\ (See section III.B for a discussion of how
these standards 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 the numerical 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.\65\ The new
tiers are described separately below.
---------------------------------------------------------------------------

    \64\ There are no gaseous emission standards, e.g.,
NOX, 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.
    \65\ 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.
---------------------------------------------------------------------------

1. Tier 6 NOX Standards for Newly-Certified Engines
    This first tier of new standards is equivalent to the CAEP/6
NOX limits that were adopted by ICAO and became
internationally applicable after December 31, 2007. Given that aircraft
turbofan engines are international commodities, engine manufacturers
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, our evaluation of the
necessary lead time, and the lack of any comments on this aspect of the
proposal, this tier of standards takes effect immediately upon the
effective date of this final rule.
    The basic form of the NOX 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 new Tier 6 NOX
standards for each of these power groupings are described separately
below.
a. Numerical Emission Limits for Higher Thrust Engines
    The Tier 6 NOX standards for newly-certified gas turbine
engines with rated thrusts more than 89 kN 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 new Tier 6 NOX standards for these higher thrust
engines are presented in Figure 1 along with the previous EPA
NOX standards, which were based on CAEP/4, for comparison.

[GRAPHIC] [TIFF OMITTED] TR18JN12.000

    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 Tier 6 standards (CAEP/6) are
referred to as being 12 percent more stringent than the existing EPA
NOX 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 new Tier 6 NOX standards for newly-certified gas
turbine engines with rated thrusts between 26.7 and equal to or 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 = 46.1600 + (1.4286 * engine pressure ratio) -
(0.5303 * kN rated thrust) + (0.00642 * engine pressure ratio * kN
rated thrust)

    In developing the corresponding NOX standards for lower
thrust engines, CAEP recognized the technical challenges that
physically smaller-sized engines sometimes present relative to
incorporating some of the lowest NOX technology approaches,
which are otherwise available to their larger counterparts. These
technical difficulties are well documented and increase progressively
as size is reduced (from around 89 kN).\66\ For example, the relatively
small combustor space and section height of these engines creates
constraints on the use of low NOX 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.\67\ With these technological constraints in mind,
CAEP fashioned the CAEP/6 NOX 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.
---------------------------------------------------------------------------

    \66\ 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.
    \67\ ICAO, ``Combined Report of the Certification and Technology
Subgroups,'' section <IP_ADDRESS>, 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 new 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 Tier 6 NOX standards for lower
thrust engines based on the engine size versus technological challenge
described in the previous paragraph.
    Comparing the new 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-NOX technologies are
the same at 89.0 kN delineation point.
    Again focusing only on 89 kN engines, the new 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.
[GRAPHIC] [TIFF OMITTED] TR18JN12.001

    At other thrust ratings the percent reduction between the new Tier
6 and existing EPA NOX 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
NOX 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.

[GRAPHIC] [TIFF OMITTED] TR18JN12.002

2. Tier 8 NOX Standards for Newly-Certified Engines
    The second tier of new standards, i.e., Tier 8, are equivalent to
the NOX limits that were most recently recommended at CAEP/8
in February 2010 for adoption by ICAO.\68\ The CAEP/8 recommended
standards have a recommended applicable 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 NOX standards considering
the technical feasibility and cost associated with the
requirements.\69\ Therefore, this tier of standards takes effect on
January 1, 2014. As with the new Tier 6 NOX standards, the
basic form of the new 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.
---------------------------------------------------------------------------

    \68\ CAEP/7 did not adopt new aircraft engine NOX
standards.
    \69\ Leadtime in this context refers to the time between CAEP
adoption of a new emission standard and the effective date of the
requirement. ICAO emission standards are global in nature and
designed to provide engine manufacturers with adequate time to
develop and deploy the requisite technology. Manufacturers produce
engines that comply with new ICAO standards to ensure their products
can be sold and used worldwide even in the absence of specific U.S.
regulations. Based on this response to the ICAO standard, we find
that there is also adequate leadtime between EPA's promulgation of
the new requirement and the associated effective date. No public
comments pertaining to leadtime were received.
---------------------------------------------------------------------------

a. Numerical Emission Limits for Higher Thrust Engines
    The new Tier 8 NOX 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 new Tier 8 NOX standards for these higher thrust
engines are presented in Figure 4 along with the new Tier 6 standards
for comparison.

[GRAPHIC] [TIFF OMITTED] TR18JN12.003

    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 new Tier
8 standards (CAEP/8) are referred to as being 15 percent more stringent
than the new Tier 6 NOX 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 engine designs range from
about 11 to 19 percent.
b. Numerical Emission Limits for Lower Thrust Engines
    The new Tier 8 NOX standards for newly-certified gas
turbine engines with rated thrusts between 26.7 but less than or equal
to 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 NOX standards for
low thrust engines, CAEP recognized the technical challenges that
physically smaller-sized engines represent relative to incorporating
some of the lowest NOX technology, which is otherwise
available to their larger counterparts. These technical difficulties
were described in the previous section for the 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 new
Tier 8 NOX standards for lower thrust engines based on the
engine size versus technological challenge described in the previous
paragraph. First, the new Tier 8 NOX 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-
NOX technologies are comparable. This same characteristic
was observed for the Tier 6 standards. Second, as shown below in Figure
5 for 89 kN engines, at this thrust rating the new Tier 8 standards
represents a 15 percent reduction from the 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.

[GRAPHIC] [TIFF OMITTED] TR18JN12.004

    Third, at other thrust ratings the percent reduction between the
new 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.
[GRAPHIC] [TIFF OMITTED] TR18JN12.005

B. Application of the Tier 6 NOX Standards to Newly-
Manufactured Engines

    This section describes the application of the new Tier 6
NOX standards to newly-manufactured engines, and our amended
temporary flexibilities for newly-manufactured engines that show
significant problems complying with these requirements. Also,
consistent with CAEP/8, we are not applying the new Tier 8
NOX 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 NOX Standards for Newly-
Manufactured Engines
    As described above, the new Tier 6 NOX standards apply
to all engine types or models that receive a new type certificate after
the effective date of the final rule. We are also phasing in these same
NOX 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.\70\ As a
result, manufacturers 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.\71\ 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 necessary to
ensure that the full benefits of newer, more stringent requirements
will be achieved in a reasonable time.\72\ We are, however, adopting
certain limited flexibilities for engines that cannot be made compliant
because of specific technical or economic reasons, as discussed later
in this section.
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    \70\ The requirement that newly-manufactured engines must meet
the CAEP 6 NOX 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.
    \71\ 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.
    \72\ 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.
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    As described in the proposal, the effective date of January 1, 2013
\73\ 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 NOX 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
74 75 76 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 2012 time frame, and
(3) any noncompliant models will be phased out of production because of
low market demand.
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    \73\ The regulatory text specifies that engine models certified
at or below the Tier 4 NOX standards may be produced
through December 31, 2012 without meeting the Tier 6 NOX
standards. Therefore, the effective date of the standards for newly-
manufactured engines is effectively January 1, 2013.
    \74\ 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.
    \75\ 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 NOX Production Cutoff Cost Analysis, WP/
39, Presented by the FESG NOX Stringency Task Group,
February 6, 2009. A copy of this document is in docket number EPA-
HQ-OAR-2010-0687.
    \76\ 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 NOX 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.
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    We think that the five-year phase-in period from ICAO's effective
date of the CAEP/6 standards (corresponding to our new Tier 6
NOX standards) for newly-manufactured engines is adequate
for manufacturers and their customers to respond to the new
requirements without disrupting their future planning and purchasing
decisions.77 78 This phase-in period for applying the Tier 6
NOX standards to newly-manufactured engines is also
identical to the date for this same requirement that was adopted by
ICAO. No comments were received expressing concern with this phase-in
period for newly-manufactured engines.
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    \77\ The ICAO CAEP/6 NOX standards became effective
after December 31, 2007.
    \78\ 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.
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    We did, however, receive two comments expressing the view that the
time between the date of our final rule and the January 1, 2013
effective date of the production cutoff would be too short if it is
less than one year. General Electric Aviation (GE) was the most
detailed and began by noting that most of the engine models currently
in production were certified to the Tier 4 standards and had
demonstrated NOX emissions below the Tier 6 at that time.
They continued that if the original certification reports are
sufficient for the FAA to formally certify these engines to the Tier 6
standards, then none of these engines would be adversely affected by
the production cutoff. However, GE expressed the concern that if
additional interactions or formal action by the FAA were needed, or
revisions to the FAA's FAR Part 34 were required, then having less than
one year between EPA's final rule and the production cutoff could
disrupt current engine production. As a result, GE asked that the date
of the production cutoff be delayed to take effect 12 months after the
final rule, i.e., 2013. The other joint comment from the Aerospace
Industries Association (AIA) and the General Aviation Manufacturers
Association (GAMA) was similar in nature, but without supporting
details.
    The commenters' concerns do not relate to the technical or economic
feasibility of newly-manufactured engines achieving emission levels in
compliance with the new Tier 6 standards by the date of the production
cutoff as proposed. The concerns expressed do not argue that additional
time is necessary ``to permit the development and application of the
requisite technology'' to comply with the standards under CAA section
231(b). Therefore, the date of the Tier 6 production cutoff is
appropriate and consistent with the Clean Air Act.
    Section 232(b) of the Act directly addresses our obligation
relative to the effective date of the regulation. Specifically, it
says: ``Any regulation prescribed under this section (and any revision
thereof) shall take effect after such period as the Administrator finds
necessary (after consultation with the

Secretary of Transportation) to permit the development and application
of the requisite technology, giving appropriate consideration to the
cost of compliance within such period.'' Based on the information
provided above, the aircraft engine models described by GE are already
capable of complying with the EPA Tier 6 NOX standards using
already applied requisite technology, i.e., the cost of applying with
has already been borne, as the effective date of the corresponding ICAO
CAEP/6 NOX standard has already passed. We do not believe
there are any technical feasibility or economic implications arising
from the continued application of the requisite technology for those
engines to meet the Tier 6 NOX standards. Also, consistent
with our most recent previous amendment to the NOX
standards, which similarly promulgated the standard at a level that was
already being met by aircraft engine manufacturers who were already
applying the requisite technology, the effective date does not need to
include additional lead time for the development and application of
additional technology that would be needed to comply with the
standards. See, e.g., 70 FR 69604, 69674-76 (Nov. 17, 2005). As a
result, the implementation dates provide more than adequate lead time
under the statute. Therefore, because aircraft engine manufacturers are
already able to comply with the Tier 6 NOX standard through
the continued use of already applied requisite technology, and because
the effective date of the corresponding ICAO CAEP/6 NOX
standard has already passed (and also based on the assessment described
in section V. Technical Feasibility, Cost, and Emission Benefits), we
find that the dates provide more than adequate lead time under the
statute for application of requisite technology.
    We also want to stress that the production cutoff is actually an
ICAO standard and we think it is important to stay aligned with the
CAEP production cutoff date. We note that this is also being adopted by
the European Aviation Safety Agency (EASA) and perhaps other aviation
certification authorities. Our adoption of the proposed date insures
international consistency regarding the production cutoff date and
avoids contradicting our international bilateral agreements with other
governments, e.g., the European Union.
    Regarding the need for engine models to be formally recognized by
the FAA as complying with the new Tier 6 standard, this is completely
within the purview of the FAA. In our previous most recent amendment to
the NOX standard, we provided just a one-month lead time
period before the revised standard became effective, and FAA did not
adopt corresponding implementing regulations until one year later, with
no apparent disruption to the industry. (See 70 FR 69664, Nov. 17,
2005.) The new Tier 6 standards are the same as the CAEP/6 standards
that were approved by ICAO in 2005 with an effective date of beginning
after December 31, 2007. Therefore, just as for the 2005 revised
NOX standard that we similarly promulgated significantly
later than the effective date of the corresponding ICAO CAEP standard,
we do not believe that it is necessary to delay the effective date
based on a need for the FAA to revise its own implementation and
enforcement regulations.
    Finally, section 232(a) of the Act directs the FAA to ensure
compliance with our standards. In this regard, the FAA has developed a
streamlined process to recognize compliance with Tier 6 and or Tier 8
as appropriate for currently type certified engine models which meet
the emission standards and they have assured the regulated industry
that they will dedicate the necessary resources to formally recognize
conformance with the standards before the production cutoff date.
    For the reasons stated above, EPA is promulgating the Tier 6
production cutoff with the originally proposed effective date of
January 1, 2013.
2. Carryover of Previously Generated Emission Test Data
    Aircraft engine models normally receive type certificates, which
include a determination that the model meets the emission standards in
force at the time the type certificate is granted. EPA has not updated
its aircraft emission standards or test procedure regulations since
2005. In this action we are adopting Tier 6 and Tier 8 NOX
emission standards and are adopting either in 40 CFR part 87 directly
or through incorporation by reference of Annex 16, Volume II a number
of minor changes to test procedures and related requirements. These
changes will become effective on the date when the rule becomes
effective.
    This leaves open a question regarding the future validity and
acceptability for amended type certificates of emission tests and
emission test data generated under previously specified test procedures
and related requirements. For example, there may be an engine model
tested in 2004 that demonstrated HC, CO, and NOX emission
levels below the exhaust emission standards in effect at that time and
also below the Tier 6 or perhaps even the Tier 8 standards that are
being promulgated in this final rule. We want to be clear that we do
not intend minor changes to test procedures or related provisions and
requirements to trigger the need for additional testing. Thus, in cases
where a manufacturer has a valid current type certificate based on
emissions information generated under the test procedures in force at
the time the type certificate was granted, we consider that data to be
valid for any formal FAA recognition of compliance, e.g., an amended
type certificate, with the Tier 6 or Tier 8 NOX emission
requirements if the original test data demonstrate such compliance. The
same is true for the HC and CO emission standards. This clarification
should greatly facilitate compliance determinations by the FAA and
eliminate any uncertainty regarding the potential for otherwise minor
test procedure changes to trigger new emissions testing for previously
certificated engines with emission levels below the new NOX
standards.
3. Exemptions and Exceptions From the Tier 6 Production Cutoff
    In conjunction with the implementation of the new Tier 6
NOX standards, we are establishing provisions which allow
engine manufacturers to request an exemption or exception from meeting
the Tier 6 NOX standards for newly-manufactured engines.
These provisions replace existing provisions addressing exemptions that
were promulgated in section 87.7 of our aircraft engine regulations.
(Any exemptions previously issued under section 87.7 would not be
affected by the revisions.) This section of the preamble describes
these 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. It also includes a
description of a short-term exception program (termed the low-volume,
time-limited transitional exemption program). These provisions have
largely been crafted to be consistent with exemption provisions in the
ICAO Environmental Technical Manual (ETM).79 80 The
provisions of

the ETM guidance were developed in the context of the CAEP/6
NOX production cutoff deliberations leading up to the CAEP/8
meeting in February 2010.
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    \79\ 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.
    \80\ Note that EPA has submitted a paper to amend the exemption
provisions included in this ETM to be consistent with this rule. See
ICAO, ``Newly Produced Engine Exemptions for CAEP/6 NOX
Production Cutoff,'' CAEP9--WG3-CTG-2--IP01, September 23, 2010. A
copy of this document is in docket number EPA-HQ-OAR-2010-0687.
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    While we are revising 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.\81\ 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.
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    \81\ 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.
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    We are deleting from our regulations the requirement in Sec.
87.7(e) that the FAA publish a notice of the exemption in the Federal
Register. The FAA has an established process in place for publishing
requests for exemption that are filed in accordance with 14 CFR part
11. Under Sec.  87.7(b) of the existing regulations, the FAA, with EPA
concurrence, may also 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.\82\ Therefore, we are deleting these provisions to avoid
confusion.
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    \82\ 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.
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    We are also deleting the time-limited exemption provision for in-
use engines that is contained in section 87.7(d) of the existing
regulations. This provision applies to fuel venting and smoke emission
standards, which were new when the exemption was adopted in 1973. The
exemption allowance was limited to in-use engines that were unable to
comply with the requirements when the regulation became effective in
1974. The in-use fleet of engines was fully retrofitted to comply with
the standards later in the 1970s. Therefore, this provision is now
obsolete and we are deleting it to avoid confusion. We proposed to
delete the existing provisions for temporary exemptions based on
flights for short durations and infrequent intervals. This proposal was
based on the EPA's and FAA's belief that the provisions were
unnecessary 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 appeared to have no utility.
    We received two comments from the Aerospace Industries Association
(AIA) and the General Aviation Manufacturers Association (GAMA)
requesting that the provision be retained. First, they argued that as
in the past, a new aircraft may be produced at a commercial facility
that is destined for immediate conversion to a military only
application at a separate facility. These aircraft may require a small
number of airworthiness flight tests before being delivered to the
conversion facility and conceivably would be subject to EPA standards
during flight testing. While these aircraft would generally utilize
compliant engines, it may be possible that non-compliant engines could
be used (our standards do not apply to engines used on military
aircraft as discussed later) and temporary exemptions would be
necessary. Second, AIA and GAMA commented that it would be helpful if
the provision also allowed for granting a discrete number of exemptions
over a specified time period, rather than having to request the
exemption prior to each flight as currently required.
    In considering the commenters' suggestion to retain the exemption
provision, we note that allowing such operations will not have any
significant adverse affect on the environment because of the infrequent
nature and short duration of such flights. Retaining the exemption is
also consistent with exempting military aircraft from emission control
requirements as discussed later. Therefore, we have retained the
provision with one change, made in response to the comments, as
described below.
    The current provision calls for the Secretary of Transportation to
consult with the EPA Administrator when considering any exemption
request for infrequent interval and short duration flights not
explicitly allowed by the regulations. Given the inconsequential nature
of such flights on the environment, we believe that the Secretary
should be able to consider and act on these petitions unilaterally to
streamline the process. Therefore, we are deleting that portion of the
previous exemption provision. Of course, we will consult with the
Secretary if asked to do so. As for requesting a discrete number of
temporary exemptions, we believe this is an issue that the Secretary of