EO12866_Aircraft Engine Emission Standards 2060-AO70 NPRM Rulemaking
Document_2011/01/20

  SEQ CHAPTER \h \r 1 ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 87 and Part 1068

[EPA-HQ-OAR-2010-0687; FRL-XXXX-X]

RIN 2060-AO70

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

SUMMARY:  This action proposes several new NOx emission standards,
compliance flexibilities, and other regulatory requirements for aircraft
turbofan or turbojet engines with rated thrusts greater than 26.7
kilonewtons (kN).  We also are proposing certain other requirements for
gas turbine engines that are subject to exhaust emission standards.
First, we are proposing to clarify when the emission characteristics of
a new turbofan or turbojet engine model have become different enough
from its existing parent engine design that it must be separately
certified to the most current emission standards.  Second, we are
proposing a new reporting requirement for manufacturers of gas turbine
engines that are subject to any exhaust emission standard to provide us
with timely and consistent emission-related information.  Third, and
finally, we are proposing amendments to aircraft engine test and
emissions measurement procedures.  EPA actively participated in the
United Nation’s International Civil Aviation Organization (ICAO)
proceedings in which most of these proposed requirements were first
developed.  These proposed regulatory requirements have largely either
been adopted or are actively under consideration by ICAO.  Therefore,
adopting the proposed requirements would bring the United States into
alignment with the international requirements.

DATES: Comments must be received on or before [insert date 60 days after
publication in the Federal Register.]

Hearing:  The public hearing will be held [insert date no fewer than 15
days after publication and at least 30 days before end of comment
period] at the Environmental Protection Agency, XXX Building, Room
Number XXX, 1201 Constitution Avenue, NW, Washington, DC 20004,
Telephone:<PHONE_NUMBER>.  See section VIII for more information about
public hearings.

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

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

	(	Email<EMAIL_ADDRESS>
	(	Fax:<PHONE_NUMBER>

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

Instructions:  Direct your comments to Docket ID No.
EPA-HQ-OAR-2010-0687.  EPA's policy is that all comments received will
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Docket:  All documents in the docket are listed in the
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information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute.  Certain other material, such
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Publicly available docket materials are available either electronically
in www.regulations.gov or in hard copy at EPA Docket Center, EPA/DC, EPA
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excluding legal holidays.  The telephone number for the Public Reading
Room is<PHONE_NUMBER>, and the telephone number for the EPA Docket
Center is<PHONE_NUMBER>

FOR FURTHER INFORMATION CONTACT:  Bryan Manning, Office of
Transportation and Air Quality, Office of Air and Radiation,
Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI
48130; 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:

Category	NAICSa Codes	SIC Codesb	Examples of potentially affected
entities

Industry		336412	3724	Manufacturers of new aircraft engines

Industry		336411	3721	Manufacturers of new aircraft

a North American Industry Classification System (NAICS)

b Standard Industrial Classification (SIC) system code

This table lists the types of entities that EPA is now aware could
potentially be regulated by this action.  Other types of entities not
listed in the table could also be regulated.  To determine whether your
activities are regulated by this action, you should carefully examine
the applicability criteria in 40 CFR 87.1 (part 87).  If you have any
questions regarding the applicability of this action to a particular
entity, consult the person listed in the preceding FOR FURTHER
INFORMATION CONTACT section.

Table of Contents

I. Overview and Background

	A.  Summary of the Proposal

	B.  EPA’s Responsibilities under the Clean Air Act

 	C.  Interaction with the International Community

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

	E.  Brief History of ICAO Regulation of Aircraft Engine Emissions

II. Why is EPA Taking this Action?

	A.  NOx Inventory Contribution

		1.  Landing and Takeoff (LTO) Emissions

		2.  Non-LTO Emissions

	B.  Health, Environmental and Air Quality Impacts

		1.  Background on Ozone, PM and 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

III. Details of the Proposed 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.  Exemptions from the Tier 6 Production Cutoff

			a.  Spare Engines

			b.  New Provisions for Engines Installed in New Aircraft

				i.  Time-Frame and Scope

				ii.  Production Limit

				iii.  Exemption Requests

				iv.  Foreign Aircraft

			c.  Voluntary Emission Offsets

		3.  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.  Proposed Standards for Supersonic Aircraft Turbine Engines

	F.  Amendments to Test and Measurement Procedures

	G.  Future Standards for New Technology Turbine Engines and Supersonic
Aircraft Turbine Engines

IV. Description of Other Revisions to the Regulatory Text

		A.  Applicability Issues

			1.  Military Engines

			2.  Noncommercial Engines

		B.  Non-Substantive Revisions

	C.  Clarifying Language for Regulatory Text

V. Technical Feasibility, Costs, and Emission Benefits

VI. Consultation with FAA

VII. Public Participation

VIII. Statutory Provisions and Legal Authority

IX. Statutory and Executive Orders Review

	A.  Executive Order 12866: Regulatory Planning and Review

	B.  Paperwork Reduction Act

	C.  Regulatory Flexibility Analysis

	D.  Unfunded Mandates Reform Act

	E.  Executive Order 13132: Federalism

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

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

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

	I.   National Technology Transfer Advancement Act

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

I.  Overview and Background

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

Summary of the Proposal

	We are proposing several new emission standards and other regulatory
requirements for aircraft turbofan and turbojet engines with rated
thrusts greater than 26.7 kilonewtons (kN).  First, we are proposing two
new tiers of more stringent emission standards for oxides of nitrogen
(NOx).  The proposed standards would apply differently to two classes of
these engines, i.e., “newly-certified engines” and
“newly-manufactured engines.”  The newly-certified engine standards
would apply to aircraft engines that have received a new type
certificate and have never been manufactured prior to the effective date
of the new emission standards.  Requirements for newly-manufactured
engines would apply to aircraft engines that were previously certified
and manufactured in compliance with preexisting standards, and would
require manufacturers to either comply with the newer standards by a
specified future date or cease production.  Newly-manufactured engine
standards are also sometimes referred to as “production cutoff”
standards.  Second, we are proposing certain time-limited flexibilities,
i.e., the potential for exemptions as defined in the regulations for
newly-manufactured engines that may not be able to comply with the first
tier of the proposed NOx standards because of specific technical or
economic reasons.

	We are also proposing a number of additional changes that would apply
to a wider range of aircraft gas turbine engines than those that would
be subject to the proposed new emission standards.  First, we are
proposing to clarify that when the emission characteristics of a new
turbofan engine model have become different enough from its existing
parent engine design, i.e., a derivative of an originally certified
engine type, that it must be separately certified to the most current
emission standards.  Second, we are proposing new reporting requirements
for manufacturers that produce gas turbine engines subject to any
exhaust emission standard.  This would provide us with timely and
consistent emission data and other information that is necessary to
conduct emission analyses and develop appropriate public policy for this
aviation sector.  Specifically, reports would 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, which are only subject to
smoke standards.  Third, we are proposing amendments to the test and
measurement procedures for aircraft engines.  Finally, as described in
section IV, we are proposing minor amendments to provisions addressing
definitions, acronyms and abbreviations, general applicability and
requirements, exemptions, and incorporation by reference.

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

EPA’s Authority and Responsibilities Under the Clean Air Act

Section 231(a)(2)(A) of the Clean Air Act (CAA) directs EPA, from time
to time, to propose aircraft engine emission standards applicable to the
emission of any air pollutant from classes of aircraft engines which in
its judgment causes, or contributes to, air pollution which 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
insure compliance with EPA’s standards.  42 U.S.C. § 7572.  Finally,
section 233 of the CAA vests the authority to promulgate emission
standards for aircraft or aircraft engines only in EPA.  States are
preempted from adopting or enforcing any standard respecting aircraft
engine emissions unless such standard is identical to EPA’s standards.
42 U.S.C. § 7573.  Section VI of today's proposal further discusses our
coordination with DOT through the FAA.   It also describes DOT’s
responsibility under the CAA to enforce the aircraft emission standards
established by EPA.

Interaction with the International Community

We began regulating the emissions from aircraft engines in 1973.  Since
that time, we have worked with the FAA and the International Civil
Aviation Organization (ICAO) to develop international standards and
other requirements 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.”  ICAO’s responsibilities include developing
aircraft technical and operating standards, recommending practices, and
generally fostering the growth of international civil aviation.  The
United States is currently one of 190 participating member States of
ICAO. ,

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 requirements that
are at least as stringent as ICAO’s standards.  States may ban the use
any aircraft within their airspace that does not meet ICAO standards.
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 its aircraft of any member State will
be permitted to operate in any other member State.  Third, and finally,
to ensure that international commerce is not unreasonably constrainted,
a participating nation which elects to adopt more stringent standards is
obligated to notify ICAO of the differences between its standards and
ICAO standards. ,   However, if a nation sets tighter standards than
ICAO, air carriers not based in that nation (foreign-flagged carriers)
would only be required to comply with ICAO standards or more stringent
standards imposed by their own nations, if applicable.

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

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.  Since that time,
we have occasionally revised those regulations.  Two of these revisions
are most pertinent to today’s proposal.  First, in a 1997 rulemaking,
we made our emission standards and test procedures more consistent with
those of ICAO for turbofan and turbojet engines used in commercial
aviation with rated thrusts greater than 26.7kN.    These ICAO
requirements are generally referred to as CAEP/2 standards.  (The
numbering nomenclature for CAEP requirements is discussed in the next
section.)  This 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)  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.  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).

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.  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.  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 newly-manufactured engines unlike the CAEP/2 standards).  In
2004, CAEP/6 recommended a 12 percent NOx reduction, which ICAO approved
in 2005. ,  The CAEP/6 standards applied to newly-certified engine
models beginning after December 31, 2007.  At the most recent meeting,
CAEP/8 recommended a further tightening of the NOx standards by 15
percent for newly-certified engines.,  The Committee also recommended
that the CAEP/6 standards be applied to newly-manufactured engines.
ICAO is currently considering the CAEP/8 recommendations.  We expect
final ICAO action regarding the CAEP/8 recommendations in early 2011.

II. Why Is EPA Taking This Action?

As mentioned above, section 231(a)(2)(A) of the CAA authorizes the
Administrator to “from time to time, issue proposed emission standards
applicable to 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.
NOx is a precursor to the formation of ozone.  Many commercial airports
are located in urban areas and many of these areas have ambient ozone
levels above the National Ambient Air Quality Standards (NAAQS) for
ozone (i.e., they are in nonattainment for ozone) and fine particulate
matter (PM 2.5).  This section discusses the contribution of aircraft
engines used in commercial service with rated thrusts greater than
26.7kN to the national NOx emissions inventory and the health and
welfare impacts of NOx and PM emissions.

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 affect local and regional ambient air quality.  These
emissions generally occur at or below 3,000 feet above ground level and
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 these emissions associated with all ground and flight
operations are generally referred to as full flight emissions.

The aircraft engine NOx emission inventories for the LTO and non-LTO
flight regimes described above are discussed separately in the following
sections.

 1.  Landing and Takeoff Emissions

In this section, we will present NOx emission inventories for commercial
turbine-engine aircraft.  The most recent comprehensive analysis of
historical, current and future LTO emissions from aircraft engines comes
from a study undertaken for us by Eastern Research Group (ERG).

The study analyzed the national emissions of commercial aircraft
operations in the United States from 1986 through 2008, and then
projected emissions in 2020 and 2030.  The study showed that total LTO
NOx emissions from this sector have increased approximately 28 percent
from 78 thousand tons in 1986 to 97 thousand tons in 2008.  Table 1
shows the contribution of aircraft NOx to the current total mobile
source NOx inventory.  It should be noted that the aircraft baseline
emissions year in this table is 2008, whereas the baseline year for all
other mobile sources is 2009.  Clearly aircraft are a meaningful portion
of the current national NOx inventory whose contribution has grown
despite 20 years of NOx emission standards of increasing stringency.

Table 1: Annual NOx Baseline Levels for Commercial Aircraft (LTO only)
and Other Mobile Sources

Category	NOx

(Thousand Tons)

Aircraft	97	0.8%

All Other Nonroad	4,392	37.6%

Highway	7,195	61.6%

Total Mobile Source	11,684	--

As previously mentioned, the operation of other mobile source categories
occurs completely at ground level, and when we compare emissions of
aircraft to other sources, we tend to focus on the LTO emissions that
occur close to the ground.  However, as will be discussed in more detail
in the next section, non-LTO emissions are almost an order of magnitude
larger than LTO emissions.  If we take full flight emissions into
account, the NOx emissions of aircraft are much more comparable to those
from more substantial categories such as locomotives or ocean-going
vessels.  As shown in Table 2, when considering full flight emissions,
aircraft account for 8.5 percent of total mobile source NOx emissions.

Table 2: Current Annual NOx Baseline Levels for Commercial Aircraft
(full flight) and Other Mobile Sources

Category	NOx

(Thousand Tons)

Aircraft	1,078	8.5%

All Other Nonroad	4,392	34.7%

Highway	7,195	58.8%

Total Mobile Source	12,665	--

While aircraft traffic volumes have been down somewhat during the recent
economic downturn, air traffic has historically shown itself to be a
resilient sector, demonstrating consistent growth over time.  Thus,
aircraft traffic is expected to increase in the future.  Indeed, the FAA
projects domestic revenue passenger-miles will rise at an annual rate of
3.1 percent per year from 2009 to 2030.  Expected improvements in
aircraft size, load factor and trip length over that time period result
in expected take-off increases from FAA air traffic facilities to be
somewhat lower than expected increases in passenger-miles, at 1.9
percent per year.

Table 3 shows the projected 2020 and 2030 baseline NOx emissions of
aircraft relative to highway and nonroad mobile sources in the absence
of today’s proposed action.  As can be seen from Table 3, in the
absence of further emission controls, national aircraft LTO emissions
are projected to grow by 64 percent from 2008 to 2030, and triple from
0.8 percent to 2.5 percent of the national mobile source NOx inventory
over that same period.  This latter increase can be attributed to both
the fact that NOx emissions from most of the other source categories are
projected to decrease, and aircraft emissions are projected to increase
due to growth.

Table 3: Projected Future Levels of LTO NOx for Commercial Aircraft

Year	Aircraft NOx

(Thousand Tons)	Percent of Total Mobile Source NOx

2020	119.1	1.8%

2030	147.4	2.5%

As previously mentioned, many airports are located in areas that are in
nonattainment for the ozone NAAQS.  Table 4 shows the current and
projected commercial aircraft NOx emissions inventories in several
extreme, severe and moderate ozone nonattainment areas.  As can be seen
from the table, aircraft emissions are also projected to more than
double in some areas most in need of ozone control.

Table 4: Commercial Aircraft LTO NOx Emissions in Various Ozone
Nonattainment Areas

Ozone Nonattainment Area	Nonattainment Status	Aircraft NOx (Tons)
Percent increase 2008-2030

2008	2020	2030	--

Atlanta, GA	Moderate	5,808	9,172	11,185	92.6%

Baltimore, MD	Moderate	1,148	1,696	2,167	88.8%

Charolotte-Gastonia-Rock Hill, NC-SC	Moderate	1,917	3,118	4,189	118.5%

Chicago-Gary-Lake County, IL-IN	Moderate	6,007	9,089	11,449	90.6%

Houston - Galveston - Brazoria, TX	Severe	3,045	4,571	6,173	102.7%

Los Angeles South Coast Air Basin, CA	Extreme	6,479	8,357	9,753	50.3%

Milwaukee-Racine, WI	Moderate	557	909	1,089	95.5%

Philadelphia-Wilmington-Atlantic City, PA-NY-MD-DE	Moderate	2,308	3,166
4,047	75.3%

San Joaquin Valley, CA	Extreme	74	161	180	143.2%

Riverside County, CA	Severe	70	136	165	136.7%

Sacramento, CA	Severe	603	783	941	56.1%

Washington, DC-MD-VA	Moderate	2,983	4,142	5,217	74.9%

2.  Non-LTO Emissions

Historically, emphasis has been placed on evaluating emissions during
LTO operations given their obvious impact on local air quality.  Less
emphasis has been placed on evaluating emissions from non-LTO operations
(3,000 feet above ground level) based on the assumption that such
emissions have a lesser impact on local air quality.  However, a recent
presentation at the American Meteorological Society and a follow-up
paper by the same authors suggest these upper atmosphere emissions may
also adversely affect public health at ground level more than was
previously thought.,  Based on the data and methodology of the authors,
this effect is caused primarily by the formation of fine particulate
matter, i.e., PM2.5 from gaseous emission precursors in the upper
atmosphere that are then transported to the lower atmosphere.  (The
formation of secondary PM2.5 from NOx is discussed further in section
II.B.1.b).

More specifically, the authors of these works estimated that full flight
emissions cause almost 10,000 premature mortalities per year worldwide,
with over 450 per year in the U.S.  The pollutants emitted during cruise
operations were estimated to be about 89 percent of the
population-weighed PM2.5 from aviation, with the remainder being
associated with LTO operations.  Thus, these studies assert that over
350 premature mortalities per year in the U.S. can be attributed to
secondary PM2.5 emissions originating from non-LTO operations.  We
request comments on the results of these studies, the existence of other
research into this area, and the implications of these analyses on
assessing the need for additional controls on aircraft engine emissions
in the future.

B.  Health, Environmental and Air Quality Impacts

  SEQ CHAPTER \h \r 1 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 that we are proposing to align with will help reduce
ambient ozone and secondary PM levels and thus will help areas with
airports achieve and/or maintain compliance with the National Ambient
Air Quality Standards (NAAQS).

1.  Background on Ozone, PM and NOX

	a.  What is Ozone?

Ground-level ozone pollution is typically formed by the reaction of 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.
Ground-level ozone is produced and destroyed in a cyclical set of
chemical reactions, many of which are sensitive to temperature and
sunlight.  When ambient temperatures and sunlight levels remain high for
several days and the air is relatively stagnant, ozone and its
precursors can build up and result in more ozone than typically occurs
on a single high-temperature day.  Ozone can be transported hundreds of
miles downwind from the sources of precursor emissions, resulting in
elevated ozone levels even in areas with low local VOC or NOX emissions.

	b.  What is Particulate Matter?

The discussion focuses on 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). Current NAAQS use PM2.5 as the indicator for fine particles
(with PM2.5 referring to particles with a nominal mean aerodynamic
diameter less than or equal to 2.5 µm), 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 µm and less than or equal to 10 µm, or PM10-2.5).  Ultrafine
particles are a subset of fine particles, generally less than 100
nanometers (0.1 μm) in aerodynamic diameter.

Fine particles are produced primarily by combustion processes and by
transformations of gaseous emissions (e.g., 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 pollutants including
sulfates, nitrates, organic compounds, elemental carbon and metal
compounds.  These particles can remain in the atmosphere for days to
weeks and travel hundreds to thousands of kilometers.

	c.  What is NOX?

Nitrogen dioxide (NO2) is a member of the NOX family of gases.  Most NO2
is formed in the air through the oxidation of nitric oxide (NO) emitted
when fuel is burned at a high temperature.    NO2 can dissolve in water
vapor and further oxidize to form nitric acid which reacts with ammonia
to form nitrates, an important component of ambient PM.  NOX along with
non-methane hydrocarbon (NMHC) 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 (ozone AQCD) and
2007 Staff Paper.,  People who are more susceptible to effects
associated with exposure to ozone can include children, the elderly, and
individuals with respiratory disease such as asthma.  Those with greater
exposures to ozone, for instance due to time spent outdoors (e.g.,
children and outdoor workers), are of particular concern.  Ozone can
irritate the respiratory system, causing coughing, throat irritation,
and breathing discomfort.  Ozone can reduce lung function and cause
pulmonary inflammation in healthy individuals.  Ozone can also aggravate
asthma, leading to more asthma attacks that require medical attention
and/or the use of additional medication.  Thus, ambient ozone may cause
both healthy and asthmatic individuals to limit their outdoor
activities.  In addition, there is suggestive evidence of a contribution
of ozone to cardiovascular-related morbidity and highly suggestive
evidence that short-term ozone exposure directly or indirectly
contributes to non-accidental and cardiopulmonary-related mortality, but
additional research is needed to clarify the underlying mechanisms
causing these effects.  In a recent report on the estimation of
ozone-related premature mortality published by the National Research
Council (NRC), a panel of experts and reviewers concluded that
short-term exposure to ambient ozone is likely to contribute to
premature deaths and that ozone-related mortality should be included in
estimates of the health benefits of reducing ozone exposure.   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.

	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).  The
ISA summarizes evidence associated with PM2.5, PM10-2.5, and ultrafine
particles (UFPs), and concludes  the following.

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 hospital
admissions and emergency department visits for ischemic heart disease
and congestive heart failure, and respiratory effects, such as
exacerbation of asthma symptoms in children and hospital admissions and
emergency department visits for chronic obstructive pulmonary disease
(COPD) and respiratory infections.  The ISA notes that long-term
exposure to PM2.5 (months to years) is associated with the
development/progression of cardiovascular disease, premature mortality,
and respiratory effects, including reduced lung function growth,
increased respiratory symptoms, and asthma development.  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 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 and cancer, mutagenicity, and genotoxicity and
long-term exposure to PM2.5.

For PM10-2.5, the ISA concludes that the current evidence is suggestive
of a causal relationship between short-term exposures and cardiovascular
effects, such as hospitalization for ischemic heart disease.  There is
also suggestive evidence of a causal relationship between short-term
PM10-2.5 exposure and mortality and respiratory effects.  Data are
inadequate to draw conclusions regarding the health effects associated
with long-term exposure to PM10-2.5.

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

	c.  What are the Health Effects of NOX?

Information on the health effects of NO2 can be found in the EPA
Integrated Science Assessment (ISA) for Nitrogen Oxides.  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.  In addition, small but significant
increases in non-specific airway hyper-responsiveness were reported
following 1-hour exposures of asthmatics to 0.1 ppm NO2.  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.   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.

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
U.S.  The sensitivity of terrestrial and aquatic ecosystems to
acidification from nitrogen deposition is predominantly governed by
geology.  Prolonged exposure to excess nitrogen deposition in sensitive
areas acidifies lakes, rivers and soils.  Increased acidity in surface
waters creates inhospitable conditions for biota and affects the
abundance and nutritional value of preferred prey species, threatening
biodiversity and ecosystem function.  Over time, acidifying deposition
also removes essential nutrients from forest soils, depleting the
capacity of soils to neutralize future acid loadings and negatively
affecting forest sustainability.  Major effects include a decline in
sensitive forest tree species, such as red spruce (Picea rubens) and
sugar maple (Acer saccharum); and a loss of biodiversity of fishes,
zooplankton, and macro invertebrates.

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

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

The deposition of airborne particles can reduce the aesthetic appeal of
buildings and culturally important articles through soiling, and can
contribute directly (or in conjunction with other pollutants) to
structural damage by means of corrosion or erosion.   Particles affect
materials principally by promoting and accelerating the corrosion of
metals, by degrading paints, and by deteriorating building materials
such as concrete and limestone.  Particles contribute to these effects
because of their electrolytic, hygroscopic, and acidic properties, and
their ability to adsorb corrosive gases (principally sulfur dioxide).

b.  Visibility Effects

NOx emissions contribute to visibility impairment in the U.S. through
the formation of secondary PM2.5.  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.

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 proposing would impact
ambient concentrations of air pollutants.  Nationally, levels of PM2.5,
ozone, and NOX are declining.  However as of 2008, approximately 127
million people lived in counties that exceeded any NAAQS.  These numbers
do not include the people living in areas where there is a future risk
of failing to maintain or attain the NAAQS.

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

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 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.   The aircraft engine emission standards being
proposed today were approved by ICAO/CAEP and would have an
implementation date of 2013.  Therefore, the aircraft engine emission
reductions that are being proposed today should be useful to states in
attaining or maintaining the PM2.5 NAAQS.

 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 16
counties with a population of almost 35 million may not attain the 2008
ozone standard of 0.075 ppm (75 ppb).  In addition, our air quality
modeling projects that in 2030 at least 9 counties with a population of
almost 28 million may not attain the 1997 annual PM2.5 standard of 15
µg/m3 and 26 counties with a population of over 41 million may not
attain the 2006 24-hour PM2.5 standard of 35 µg/m3.  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.

There are currently no NO2 nonattainment areas.  However, the NO2
standards were recently revised and a new 1-hour NO2 standard was
promulgated.  Nonattainment area designations for the 1-hour NO2
standard are expected to be finalized in 2012.  These proposed aircraft
NOx reductions would be useful to states in attaining or maintaining the
NO2 standards.

III.  Details of the Proposed Rule

We are proposing two different levels or tiers of increasingly more
stringent  NOx emission standards for gas turbine engines with maximum
rated thrusts greater than 26.7 kilonewtons (kN).  Each of the tiers
would potentially apply to newly-certified engines.  Newly-certified
aircraft engines are those that would receive a new type certificate
after the effective date of the applicable standards.  Such engine types
or models would not have begun production prior to the effective date of
the new requirement.

We are also proposing to apply the first tier of the two tiers of
standards to newly-manufactured engines.  Newly-manufactured aircraft
engines are those that have been previously certified and manufactured
in compliance with preexisting standards, and will continue to be
produced after the effective date of a new applicable standard.
Normally, these newly-manufactured engines would need to comply with the
same NOx limits as newly-certified engines but at a later date or cease
production.  The end of this “phase-in” period for the
newly-manufactured engine standards is sometimes referred to a
“production cutoff,” for obvious reasons.   Again, we are proposing
only the first of the two new tiers of NOx standards for
newly-manufactured engines.  These provisions are described in detail
below.

Five other regulatory features are being proposed in today’s action.
First, we are proposing to revise provisions addressing certain
time-limited flexibilities, i.e., potential exemptions, for
newly-manufactured engines that may not be able to comply with the new
NOx standards because of specific technical or economic reasons.
Second, we are proposing to clarify when the emission characteristics of
a new engine model have become different enough from its existing parent
engine design, i.e., a “derivative” of an originally certified
engine type, that it must be certified to the latest emission standard.
Third, we are proposing new CO and NOx standards for gas turbine engines
that are used to propel supersonic aircraft.  These standards were
adopted by ICAO in the 1980s, but were not previously added to our HC
emission standard for these engines.  The proposed standards would meet
our treaty obligation under the Convention on International Civil
Aviation as previously described in section I.B.   Fourth, we are
proposing several amendments to the emission testing and measurement
procedures in our regulations that are intended to implement ICAO’s
Annex 16 and to incorporate the entire annex in our regulations by
reference.  Finally, as described in Section IV, we are proposing
amendments to current regulatory provisions addressing definitions,
acronyms and abbreviations, general applicability and requirements,
exemptions, and incorporation by reference.  These amendments are
intended to clarify requirements, make them more consistent with other
parts of the program, update the text to be consistent with current
standard language conventions, or remove obsolete provisions.

As discussed further below, with the exception of the annual reporting
requirement discussed in section III.D., the proposed reflect those that
were previously adopted by ICAO or that CAEP has recommended for
adoption by ICAO in the near future.  In this latter case, we are
proposing these requirements at this time rather than wait until ICAO
takes final action to help ensure that our standards, and the FAA’s
implementing regulations, are adopted in a timely manner once ICAO
completes its process.  We anticipate that our final standards would
generally conform to ICAO’s final standards, once adopted.  This would
better enable the regulated industry to respond to new, globally
harmonized requirements in an orderly manner, which is important given
the international nature of the market for the aircraft engines that
would be affected by today’s proposed rule.  It would also avoid
continuing the significant lag time that has sometimes occurred between
ICAO’s adoption of international standards and our adoption of
corresponding standards under U.S. law.  To the extent ICAO adopts
standards that differ from those recommended by CAEP before we issue our
final rule, we would then consider whether to make conforming amendments
in our final standards, or to issue a supplemental proposal reflecting
the amended ICAO standards, if appropriate.

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

Except to the extent needed to conform our standards to ICAO’s
standards by making them applicable to both commercial and
non-commercial engines, we are not proposing revised exhaust emission
standards for HC, CO, or smoke, which would remain in effect as
currently promulgated.  All engines subject to the proposed new NOx
standards would also continue to be subject to the existing HC, CO, and
smoke standards.   It is worth emphasizing that although we are
proposing to include these existing HC, CO, and smoke standards in a new
section 87.23, which would also contain the Tier 6 and Tier 8 NOx
standards, we are not actually proposing new standards, since under the
current form of part 87 these HC, CO and smoke standards would already
continue to apply to new engine types subject to future revised NOx
standards.

We are proposing to adopt a new naming convention in this preamble and
the regulatory text to more easily distinguish between the proposed
tiers of increasingly more stringent 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 proposed NOx standards, which are consistent with
CAEP/6, will be referred to as Tier 6 in the remainder of today’s
notice.  The second tier of proposed standards will be referred to as
Tier 8, which is consistent with CAEP/8.  We are also incorporating the
new naming convention in the regulations for the existing 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 upon the effectiveness of a final rule reflecting today’s
proposal 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 proposing two different tiers of increasingly stringent NOx
standards.  These standards would apply for all for newly-certified gas
turbine aircraft engines with maximum rated thrusts greater than 26.7kN.
 (See section III.B for a discussion of how these standards would apply
for newly-manufactured engines that are not considered to be newly
certified.)  The numerical value of the applicable standard for an
individual engine model is defined by the engine’s thrust level and
pressure ratio.  Simply stated, the pressure ratio is a ratio of the air
pressure entering the engine to the air pressure at the entrance to the
combustor, i.e., after the air has passed through the compressor section
of the engine.  Each of the proposed tiers is described separately
below.

1.  Tier 6 NOx Standards for Newly-Certified Engines

This first tier of proposed standards is equivalent to the CAEP/6 NOx
limits that were already adopted by ICAO and became internationally
effective after December 31, 2007.  Given that aircraft turbine engines
are international commodities, engine manufacturers have already
certified engine models introduced after that date in compliance with
these international requirements, or are already planning to do so for
upcoming engine designs.  Based on this, and on our evaluation of the
necessary leadtime, we are proposing that this tier of standards take
effect immediately upon the effective date of our final regulations.

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 89kN, while
lower output engines are defined as having rated thrusts less than 89kN
but greater than 26.7kN.  The proposed Tier 6 NOx standards for each of
these power grouping are described separately below.

a.  Numerical Emission Limits for Higher Thrust Engines

The proposed Tier 6 NOx standards for newly certified gas turbine
engines with rated thrusts of 89 kN or more are differentiated by
pressure ratio as shown below.

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

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

	g/kN rated output  =  -1.04 + (2.0 * engine pressure ratio)

•  For engines with a pressure ration of 82.6 or more:

g/kN rated output  = 32 + (1.6 * engine pressure ratio)

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

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

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

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

•  Retain the slope of the CAEP/4 standard for pressure ratios at or
above 62.5 for pressure ratios at or above 82.6.

The resulting proposed Tier 6 NOx standards for these higher thrust
engines are presented in Figure 1 along with the most recently adopted
existing EPA NOx standards, which were based on CAEP/4, for comparison.

As a matter of convention, the relative stringency from one CAEP
standard to another is expressed relative to a pressure ratio of 30,
because the percentage reduction is usually inconsistent across all of
the possible pressure ratios, which otherwise makes a simple comparison
difficult.  Using that convention, the proposed Tier 6 standards
(CAEP/6) are referred to as being 12 percent more stringent than the
existing EPA 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 proposed Tier 6 NOx standards for newly-certified gas turbine
engines with rated thrusts between 26.7 and less than 89.0kN are
differentiated by both pressure ratio and rated thrust as shown below.

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

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

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

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

In developing the corresponding 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 are well documented and increase
progressively as size is reduced (from around 89kN).  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.  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.

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

Comparing the proposed lower and higher thrust standards at 89kN, 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 89.0kN delineation point.

Again focusing only on 89kN engines, the proposed Tier 6 standards
represent a 12 percent reduction from the existing EPA CAEP/4-based
standards (Tier 4) 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.

At other thrust ratings the percent reduction between the proposed 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
89kN, 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 89kN decreasing to 0 percent at 26.7kN.

2.  Tier 8 NOx Standards for Newly-Certified Engines

The second tier of proposed 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.  The CAEP/8 recommended standards have a
recommended effective date after December 31, 2013.  As discussed
further in section I.V. of today’s notice, we agree with CAEP that
this provides engine manufacturers with adequate leadtime to respond to
these more stringent NOx standards considering the technical feasibility
and cost associated with the requirements.  Therefore, we are proposing
that this tier of proposed standards would take effect on January 1,
2014, provided ICAO adopts CAEP/8’s recommended standards and
effective date.  If ICAO adopts different standards or a different
effective date, we would evaluate whether to similarly adopt
correspondingly different standards and effective dates, or seek further
public comment before doing so.

As with the Tier 6 NOx standards, the basic form of the Tier 8 standards
for gas turbine engines is different for higher- and lower-rated thrust
engines.  Higher output engines are defined as having rated thrusts
equal to or greater than 89kN, while lower output engines are defined as
having rated thrusts less than 89kN but greater than 26.7kN.  The
longer-term standards for each of these power grouping are described
separately below.

a.  Numerical Emission Limits for Higher Thrust Engines

The proposed Tier 8 NOx standards for newly certified gas turbine
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 ration of 104.7 or more:

	g/kN rated output  =  32 + (1.6 * engine pressure ratio)

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

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

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

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

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

The resulting proposed Tier 8 NOx standards for these higher thrust
engines are presented in Figure 4 along with the proposed Tier 6
standards for comparison.

As noted previously, as a matter of convention the relative stringency
from one CAEP standard to another is generally expressed relative to a
pressure ratio of 30.  Using that convention, the proposed Tier 8
standards (CAEP/8 ) are referred to as being 15 percent more stringent
than the proposed Tier 6 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 technology engines ranges from
about 11 to 19 percent.

b.  Numerical Emission Limits for Lower Thrust Engines

The proposed Tier 8 NOx standards for newly-certified gas turbine
engines with rated thrusts between 26.7 but less than 89.0kN 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 proposed Tier 6 low-thrust engine standards.

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

  Third, at other thrust ratings the percent reduction between the
proposed Tier 6 and Tier 8 standards at any pressure ratio becomes
progressively smaller as thrust decreases.  This is illustrated in
Figure 6 for a pressure ratio of 30, following the convention described
above.   Also as shown in the figure for current engines, the reduction
ranges from 15 percent at the upper end of the thrust range to 5 percent
at the lower end of the range.  While not depicted in a figure, the
pattern is similar for the other pressure ratios.  However, the actual
numerical values for percentage reductions at both ends of the thrust
range, i.e., 26.7 to 89kN, 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 26.7kN, 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 89kN engines with pressure ratios of about 15.

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

This section describes our proposal to apply the proposed Tier 6 NOx
standards to newly-manufactured engines, and our proposed amended
temporary flexibilities for newly-manufactured engines that may have
problems complying with these requirements.  Also, although, consistent
with CAEP/8, we are not proposing to apply the 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 proposed Tier 6 NOx standards would apply to all
engine types or models that receive a new type certificate after the
effective date of the final rule.  We are also proposing to phase-in
these same NOx limits for newly-manufactured engines within engine
models (and their derivatives) 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 rule’s
effective date.  As a result, manufacturers would need to bring
newly-manufactured engines of these previously certified models into
compliance with the applicable Tier 6 standards by a future date or
cease production of those engine models. As we discussed and described
in our analysis of the need for a CAEP 6 production cut-off during the
CAEP process, establishing a date certain for compliance with any
emission standard is foundational to its basic design and purpose and
helps to ensure that the full benefits of newer, more stringent
requirements will be achieved in a reasonable time.   We are, however,
proposing certain limited flexibilities for engines that can not be made
compliant because of specific technical or economic reasons, as
discussed later in this section.

The proposed effective date of January 1, 2013 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,, and our more recent
discussions with manufacturers indicate that:  1) all but a few models
are already compliant with CAEP 6 standards, 2) nearly without
exception, all current production models will meet the CAEP 6
requirements by the 2011 time frame, and 3) any noncompliant models will
be phased out of production because of low market demand.

We think that the proposed five-year phase-in period from ICAO’s
effective date of the CAEP/6 standards (corresponding to our proposed
Tier 6 NOx standards) for newly-certified engines is adequate for
manufacturers and their customers to respond to the new requirements
without significantly disrupting their future planning and purchasing
decisions.,  This phase-in period for applying the Tier 6 NOx standards
to newly-manufactured engines is identical to the date for this same
requirement that CAEP/8 has recommended to ICAO for adoption.
Therefore, we are proposing that all engines newly-manufactured after
December 31, 2012 must comply with the Tier 6 NOx standards.  Again, if
ICAO ultimately adopts a production cut-off date that differs from this
proposed date, we would evaluate whether to adopt a correspondingly
different date in the final rule or to seek further public comment on
the change.

Exemption from the Tier 6 Production Cutoff

In conjunction with the implementation of the Tier 6 NOx standards, we
are proposing provisions which would allow engine manufacturers to
request exemption from meeting the Tier 6 NOx standards.  These proposed
provisions would replace existing provisions addressing exemptions,
currently promulgated in section 87.7 of our aircraft engine
regulations.  (Any exemptions previously issued under section 87.7 would
not be affected by the proposed revisions.)   This section of the
preamble describes these proposed exemption provisions which have
largely been crafted to be consistent with exemption provisions in the
ICAO Environmental Technical Manual (ETM) that has been recommended by
CAEP/8 for adoption by ICAO.,  The provisions in this ETM were crafted
in the context of the CAEP/6 NOx production cutoff deliberations leading
up to the CAEP/8 meeting in February 2010.

While we are proposing to revise our regulations, the process for
evaluating any request for an exemption 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.  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.

Under the existing regulations, EPA and the FAA may exempt
low-production volume engines from being fully compliant with the
emission standards.  Several such short-term exemptions were granted in
the 1980s when emission standards were first applied.  These exemptions
have since expired, and requests for new exemptions under those
provisions have not been submitted; therefore, we believe that the
provisions allowing for such exemptions are no longer of any utility,
and are proposing to delete these provisions.  We are also proposing to
delete the existing provisions for temporary exemptions based on flights
for short durations and infrequent intervals.  These provisions are not
necessary because our standards apply to aircraft certificated by the
FAA, and the FAA does not address in the certification process whether
an aircraft will be used for short durations or infrequent intervals.
Hence, the provisions are of no utility.

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

Finally, we are deleting the exemption provisions in §87.7(d).  These
provisions, which were intended for when the standards of §§87.11(a),
87.31(a), and 87.31(c) took effect, are now obsolete.

   a.  New Provisions for Spare Engines

This proposed exemption is intended to allow production and sale of a
newly-manufactured engine for installation on an in-service aircraft
(i.e., a “spare engine”).  It would not allow for installing such an
engine on a new aircraft.  Spare engines are produced from time to time
in order to keep an aircraft in revenue service when the existing
in-service engine must be removed for maintenance purposes.  Otherwise
removing these aircraft from active service would be very expensive and
logistically difficult.  Also, under our proposed regulations, there
would be no adverse environmental effect from allowing the use of a
spare engine as a direct replacement for an existing engine, because a
spare could be used only when the emissions of the spare engine are
equal to or lower than those of the engine it is replacing, for all
pollutants.  While manufacturers would not be required to obtain FAA or
EPA approval before producing or shipping spare engines, they would have
to submit an annual report with information about spare engines.  The
permanent record for each engine exempted under this provision would
need to indicate that the engine is an exempted spare engine and the
engine itself would need to be labeled as “EXEMPT SPARE.”

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

Under the proposed regulations, engines meeting the requirements for
spare engines could be produced and enter into commerce without prior
approval from EPA.  (The FAA intends to adopt its own separate
provisions for overseeing production of spare engines.)  It is important
to note that while engines would be exempt from the Tier 6 NOx standards
being proposed today, they would still need to be produced under an FAA
type certificate and have an Airworthiness Approval Tag.  (This process
would essentially serve as the approval step envisioned by ICAO in its
ETM language for spare engines.)  We would expect little or no
additional burden for manufacturers, since we are not proposing new
restrictions or requirements other than the end of year report.  When
combined with the proposed prohibition against using spare engines to
replace lower emitting engines, this program will ensure that using a
spare engine would not increase emissions, but would at the same time
allow the availability of spares for maintenance or replacement as
needed.

b.  New Provisions for Engines Installed in New Aircraft

The primary purpose of allowing limited continued production of Tier 4
engines is to provide for an orderly implementation of the Tier 6 NOx
production cut-off.  It addresses engines reaching the end of their
production cycles in the time frame when new emission standards take
effect.  The typical production cycle would have annual production
volumes ramp up quickly, remain at relatively large volumes for several
or many years, and then fall off over a few more years.  When new
emission standards are adopted in the middle of a production cycle to
take effect a few years later, manufacturers generally devote technical
resources to bringing into compliance those engine models expected to be
produced in large numbers in the time frame when the new standards are
in effect.  In contrast, they may plan not to invest in upgrading the
emissions of engine models that would be very near the end of their
normal production cycles when compliance with the new standards becomes
required.  The actual length and shape of this tail of production
volumes can be affected by factors not fully within the engine
manufacturers’ control, e.g., unexpected market demand.  Thus,
exemptions may be needed if a manufacturer does not complete the
production cycle before the production cutoff date and projected
production volumes are not adequate to justify resource investment to
reduce emissions or there are other technological issues.

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

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

i.  Time Frame and Scope

The proposed regulations would allow manufacturers to request an
exemption for engines  not meeting the Tier 6 NOx standards to be
installed in new aircraft.  If granted, the exemption would allow
manufacturers to produce a limited number of newly-manufactured engines,
in a time period beginning after December 31, 2012 and going through
December 31, 2016.  The time period for any given approved exemption
could be shorter depending on the specifics of the application but could
not be longer.  This exemption would be limited to NOx emissions from
engines that are covered by a valid type certificate issued by FAA.  The
engines would be required to meet all other applicable requirements.
More specifically, an engine exempted from the Tier 6 NOx standards
would need to be covered by a previously issued type certificate showing
compliance with the Tier 4 NOx standards, as well as the current HC, CO,
fuel venting, and smoke standards.

ii.  Production Limit

The number of engines exempted would generally not be allowed to exceed
75 engines per manufacturer – or more precisely per type certificate
holder.   However, any given approved exemption would include a specific
limit based on the information laid out in the manufacturer’s
exemption request.  It is worth noting that this limit of 75 differs
slightly from the current ICAO ETM exemption language, which would
generally allow up to 75 engines per type certificate.   While our
proposal would be technically different from, and potentially more
stringent than, the current ETM language, it would have practical
significance only to the extent that any manufacturer seeks exemptions
for more than one engine family and could separately justify exempting
sufficient numbers of each family to exceed the 75 total.  We do not
expect this situation to occur for the Tier 6 NOx standards.  For
example, individual manufacturers produced only 15 engines under the
most recent exemption we have granted.  Since current engine emission
data suggest that most engine models already meet the Tier 6 emission
standards, it is very unlikely that any manufacturer would seek
exemptions for multiple engine families, let alone more than two
families, and this difference should not adversely affect the industry.
Nonetheless, we have submitted a paper through the ICAO/CAEP process
seeking to align the ETM provision with those in this proposal.  Under
both our proposed regulations and the ETM, this production cap would
apply for total worldwide sales, so coordination between the
certificating authorities is important to assure this program is
implemented as envisioned in the ETM.

Our proposed exemption from the production cutoff is for up to 75
engines per type certificate holder.  In this context each corporation
or joint venture that holds a type certificate would be a separate type
certificate holder.  For the purposes of these proposed exemption
provisions, a list of likely entities that would be considered separate
type certificate holders would include the following manufacturers:
Honeywell, General Electric, Pratt & Whitney, Pratt & Whitney Canada,
and Rolls Royce (to include the BMW and Allison as separate entities).
In addition to these manufacturers, there are several joint ventures
active in the aircraft engine market, such as CFM International and
Engine Alliance.  We propose to also treat these joint ventures as type
certificate holders apart from those manufacturers making up the joint
venture.  We ask for comment on our proposed approach for defining the
corporate entity for the purposes of applying the production limit.

We are requesting comment on whether the limit of 75 engines per type
certificate holder is the appropriate value.  Seventy-five engines per
type certificate holder is reasonable based on our assessment of
historic production patterns.  In support of this proposal, we analyzed
past production histories and projected future orders of engine models
that may need exemptions to further verify that a limit of 75 would be
appropriate.  To conduct this analysis, we used data from the ASCEND
Database, which contains information on past production volumes and
estimates production volumes in the future years based on information on
actual or potential new orders.  Based on this analysis, it appears
highly unlikely that any type certificate holder would need exemptions
for more than 75 engines during the years exemptions will be available.

Beyond this, a reasonably tight limit on production volumes reflects the
economics of aircraft engine production.  Engine modifications to meet
more stringent standards and subsequent recertification are often an
expensive undertaking. When future sales are projected to be larger in
number, manufacturers have argued that economics favor a return on
investment and that market forces dictate that they make the investment
to so that they have fully compliant engines to meet customer demands.
In these cases exemptions would not be necessary.  However, in
transitions, economics are less attractive and the market forces
argument is less compelling.

While it is not possible to know how many engines (if any at all) would
be exempted during the four-year period, we can estimate a worst case
scenario.  For example, previous CAEP analysis indicated that there are
four engine manufacturers with product which does not yet meet the
proposed Tier 6 NOx standard.  If each applied for and were granted the
maximum allowable 75 exemptions over the four-year period, the total of
300 exempted engines worldwide would only be 2-3 percent of the newly
produced fleet.

iii.  Exemption Requests

We are proposing a process for requesting exemptions (for engines used
on new aircraft) that would be more formal and structured than the
current process.  We are proposing that manufacturers be required to
submit their requests to both the EPA and FAA, in order to facilitate
the timely consultation process of the two agencies.

To ensure that we have the information necessary to evaluate exemption
requests in this specific manner, the requests would need to include the
following details to describe the specific engine model for which the
manufacturer is requesting the exemption.  The proposed provisions
contained in §87.50, which are summarized below, are consistent with
and in some areas expand on the provisions in the ETM:

General Information

•  Corporate name and an authorized representative’s contact
information;

•  Description of the engines for which you are requesting the
exemption, including the engine model and sub-model names;

•  The number of engines that you would produce under the exemption
and the period during which you would produce them;

•  Identify the authorizing type certificate (type certificate number
and date);

•  Information about the aircraft in which the engines will be
installed, including the airframe models and expected first
purchasers/users of the aircraft, and the countries in which you expect
the aircraft to be flagged; and

•  List of other certificating authorities from which you have
requested (or expect to request) exemptions, and a summary of each
request.

Justification and Impacts Assessment

•  A detailed description and assessment of the environmental impact
of granting the exemption;

•  Technical issues, from an environmental and airworthiness
perspective, which may have caused a delay in compliance with a
production cutoff, if any;

•  Any economic impacts on the manufacturer, operator(s), and aviation
industry at large; and

•  Projected future production volumes and plans for producing a
compliant version of the engine model in question.

 Other Factors

•  Hardship: Impact of unforeseen technical circumstances, business
events. Or other natural or manmade calamities beyond your control, and

•  Equity issues in administering the production cutoff among
economically competing parties

It is important that any action on a potential exemption request be in
the public interest; the fairly comprehensive list of application
information in the proposed regulations is intended to gather the
information needed for this assessment.  We would expect to take a broad
perspective in evaluating what is or is not in the public interest.
This is why the manufacturer justifications would need to include a
quantified description of the environmental effects of granting the
exemption, as well as discussion of economic and technical issues
related to bringing the engine into compliance.  The analysis of
environmental impacts would need to specify by how much the exempted
engines would exceed the standards, the in-use effects in terms of
lifetime tons of NOx, and estimate the emissions rates of
engines/aircraft that could potentially be used if the exemption was not
granted.  Since exemptions granted under the proposed regulations would
apply only for NOx emissions, the analysis could also include possible
benefits regarding noise levels or reduced emissions of pollutants other
than NOx.  Relevant economic impacts could include impacts on the engine
manufacturer, airframe manufacturer, airline(s), and/or the general
public.

In the past, some manufacturers have requested exemptions based on the
largest number of engines they hoped to continue producing without
knowing how many they would actually be able to produce or who would
purchase them.  The new exemption language calls for manufacturers to
target their requests more specifically based on likely production needs
and time periods.  At any time before approval, manufacturers could
revise their requests to justify covering additional engines up to the
cap.  We would then review the revised request.  For exemptions that
have already been approved, manufacturers could also ask for additional
engines, again subject to the cap.  If they were able to justify it, we
would then amend the exemption.  For example, in the past, a
manufacturer with a potential customer interested in purchasing 10
engines might have requested an exemption to cover up to 100 engines in
case they subsequently find additional customers.  Under the proposed
regulations, the manufacturer would request an exemption for the first
10 engines.  If additional engines are needed after approval of the
exemption, including cases where they are needed by a different
customer, the manufacturer could ask to amend their approved exemption
to cover a higher number of engines.  Manufacturers also would be
required to notify us if they determine after submitting a request that
the information is not accurate, either from an error or from changing
circumstances.

While we expect a manufacturer to have this specific information when
they submit a request, the regulations would allow us to process
exemption requests with somewhat less specific information.  However, we
would expect this to apply only for unusual circumstances.

If, after consulting with FAA, we determine that the exemption request
is fully documented and approval would be in the public interest, we
would concur with approving the request if the FAA also concluded that
the request should be granted.  Note that we could approve the exemption
for a smaller number of engines than the manufacturer requested, or we
could include certain other conditions.

In order to allow us to oversee these exempted engines, manufacturers
would also be required to provide an annual report on exempt engines
similar to the information about spare exempt engines.  The permanent
record for each engine exempted under this provision would need to
indicate that the engine is an exempted engine and the engine itself
would need to be labeled as “EXEMPT NEW”.

iv.  Foreign Aircraft

We are proposing that manufacturers also include in their requests a
list of countries in which the aircraft would be expected to be
registered (sometimes called “flagged”).  While not specifically
listed in the ETM, we believe that this information is consistent with
the ETM as it would be necessary to ensure proper coordination with
other countries in which these aircraft will be registered and used.
This coordination is necessary because many countries require FAA
certification even for aircraft that will never operate in the U.S.
Normally, we would not expect that we would approve an exemption for
engines used on aircraft that would be registered in countries opposing
the exemption.

It is worth emphasizing that the proposed requirement for EPA and FAA
approval would apply equally for engines that were exempted by foreign
authorities if any of them would be used on aircraft subject to U.S.
regulations.  The ETM includes a presumption that each member country
will recognize exemptions granted by other countries.  However, this
presumption is conditioned upon the exemption being granted consistent
with the guidelines of the ETM.  Significantly, the ETM requires
thorough coordination when exempted engines will be used in multiple
countries.  It states:

Exemptions for new engines should be processed and approved by the
competent authorities for both the manufacture of the exempted engines
and the initial operator of the aircraft to which they are to be fitted.
Given the international nature of the aviation enterprise, civil
aviation authorities of member states should attempt to collaborate and
consult on the details of exemptions. In the case where engine type
certification is done through a reciprocity agreement between or among
member states, the states involved should coordinate on the processing
of exemptions and concur before approval is granted.

Thus in most cases, manufacturers should be getting approval from all
relevant authorities at the same time.  However, whether they seek
approval at the same time or in sequence, requiring EPA and FAA approval
is consistent with our international agreements.  The Clean Air Act
(which provides EPA with its authority to establish emission standards)
includes no provisions that would allow any foreign country to exempt
aircraft engines from the applicable standards promulgated thereunder.
Nevertheless, since our proposed exemptions provisions are consistent
with the procedures called for in the ETM, assuming appropriate
coordination, we would not expect to object to exemptions to engines
properly exempted by other countries under those procedures.

Finally, the proposed regulations state that the production limit would
apply to worldwide sales of the exempted engines.  For example, where a
manufacturer requesting an exemption already has an exemption issued by
a foreign competent authority for 20 engines not subject to EPA emission
standards because they will not operate in the U.S., the maximum number
of engines that we would exempt would be an additional 55.  We believe
that to approve more than 55 would be inconsistent with the ETM.  We
would also likely include as a condition of our exemption approvals that
manufacturers could not obtain exemptions for more than 75 engines
worldwide.

c.  Voluntary Emission Offsets

We are requesting comment on establishing a voluntary program by which
manufacturers could receive emission credits to offset higher emissions
from exempted engines.  An example of such a program is summarized in a
memorandum to the docket.  We would expect manufacturers to be
interested in generating offsets for one of three purposes.  First,
manufacturers might choose to generate offsets as part of their
justifications for exemptions.  For example, where we determine that an
exemption would not be in the public interest because it would have an
undue adverse effect on air quality, a manufacturer might use offsets so
that the combination of the exemption and offsets would be more emission
neutral.  Second, manufacturers might choose to generate offsets as part
of a justification for being allowed to exceed the cap of 75 exempted
engines per manufacturer.  Note that since this is not specifically
allowed in the proposed regulations, we would need to amend the proposed
regulations as part of the final rule to allow this option.  We are
asking for comment on this option, and could include it in the final
rule based on the comments and our assessment of the inputs and issues.
Third, a manufacturer might also be interested in generating offsets to
bank for use for exemptions of engines to be produced after the credit
generating engines are produced, or possibly against a future production
cutoff.  This would also require a change to the proposed regulations.

Under this approach, generation of offsets would be voluntary and would
be open to all certifying engine manufacturers.  One concept would be to
allow credits to be generated only from engine models that are
introduced after this rule and that had characteristic levels
significantly below the otherwise applicable standard (e.g., at least 10
percent below).  Another concept would be to allow credits only to the
degree which the NOx characteristic level was more than 10 percent below
the standard.  For example, an engine that was 15 percent below the
standard would generate credits equivalent to 5 percent of the standard.
 This would ensure a net improvement in emissions.  If we were to
finalize such a program, we could reserve the right to restrict the use
of credits so that they were used in a manner that ensured there was no
net adverse impact on air quality.  Such a program would need to ensure
that emission benefits from one aircraft model truly offset the higher
emissions from another model.  For example, emissions from regional
aircraft may not be directly equivalent to emissions from aircraft
designed for longer cross-country or international flights.  Equivalency
factors could be developed to account for differences in the number of
LTOs per mile, the number of LTOs per years, and the lifetime of the
aircraft.  Commenters are encouraged to review additional information
contained in the memorandum to the public docket and provide input on
the ideas, concepts, and options presented therein.

3.  Potential Phase-In of New Tier 8 NOx Standards for
Newly-Manufactured Engines

We are not proposing to phase-in the proposed Tier 8 NOx standards for
newly-manufactured engines at this time, since such a feature is not
included in the CAEP/8 recommendation to ICAO.  This means that engine
manufacturers may continue to produce Tier 6 compliant engines within
already certified models after the proposed Tier 8 standards become
effective for newly-certified engine models.  As noted elsewhere, EPA is
working within the ICAO/CAEP framework to develop harmonized
international standards for aircraft turbine engines.  At the February
2010 meeting of CAEP, where the CAEP/8 NOx standards were approved for
recommendation to ICAO, the committee decided to continue considering a
related newly-manufactured engine standard as a future work item at
CAEP, pending new information on technology and market responses.

We will continue our efforts to evaluate a newly-manufactured engine
standard as a complement to the Tier 8 NOx standards as part of the
future CAEP work programs.  We believe that such a requirement is a
necessary component of any effective NOx control strategy for aircraft
turbine engines.  It provides an orderly, stable transition between
emission requirements that is helpful for product planning by engine and
airframe manufacturers, and in making purchasing decisions by their
customers.  It also ensures compliance with any new emission standard in
a reasonable period of time, thereby providing the public with all the
environmental benefits that a new emission standard can provide.
However, in order to maximize consistency with the CAEP/8 NOx standard
as currently recommended to ICAO, our proposed Tier 8 standard does not
contain a production cut-off.

Assuming a CAEP/8 production cutoff is adopted at some time in the
future, we will re-examine the permanent exemption provisions to ensure
a timely and orderly phase-out of engine models that do not meet the
CAEP/8 NOx standards.  We would expect this to be done as part of future
CAEP deliberations and through a notice and comment rulemaking process
to amend our own regulations.

Application of Standards for Derivative Engines

It is very common for a manufacturer to make slight changes to an engine
model that is in production while keeping the same engine core design.
Depending on the degree of these changes, a decision must be made
whether the modified design was significant enough that a new type
certificate is necessary, or if the changes were minor relative to the
base engine so that it still conformed to the original type certificate
of the model.  This may be further complicated because of the common
practice of making iterative changes over time, that leaves open the
question as to when the cumulative changes reach a point where a new
type certificate is warranted.

In the past, these determinations were made for turbofan engines by an
engineering evaluation that was performed by the engine manufacturer and
then confirmed by the FAA’s certificating directorate.   As part of
the ICAO/CAEP deliberations leading up to the February 2010 CAEP/8
meeting, a new standardized protocol was agreed upon.  The protocol
included specific criteria for deciding when a modification constituted
a new model that required a new type certificate, or when a modification
was simple enough to be considered a derivative of an already
type-certified engine model.

Toward that end, we are proposing to allow manufacturers to ask for a
determination that an engine model is a derivative of a previously
certified engine having substantially the same engine core design.
Where we determine the engine model to be sufficiently similar to be
considered a derivative engine model, we would allow continued
production of engine model to the same extent as allowed for the
original engine model. Where the FAA determines that an engine model is
not a derivative of a previously certified engine model, it would be
required to be certified to the same standards as other new engine
models certified at that time.

Consistent with ICAO provisions, we would consider a modified engine to
be a derivative engine for emissions purposes if the modified engine
model had been derived from an original engine that was certified to the
requirements of this part, and one of the following conditions is met:

(1) All modifications from the original engine were necessary for
improved safety and continued airworthiness, as determined by FAA.

(2) Emissions from the derivative engines must be equivalent to or lower
than the original engine.

The proposed regulations specify that to show emissions equivalency, the
engine manufacturer must demonstrate that the difference between
emission rates of a derivative engine and the original engine are within
the following allowable ranges:

	± 3.0 g/kN for NOx.

	± 1.0 g/kN for HC.

	± 5.0 g/kN for CO.

	± 2.0 SN for smoke.

Engine models represented by characteristic levels at least five percent
below all applicable standards would be allowed to demonstrate
equivalency by engineering analysis.  In all other cases, the
manufacturer would be required to test the new engine model to show that
its emissions met the equivalency criteria.

D.  Annual Reporting Requirements

In May of 1980, ICAO’s Committee on Aircraft Engine Emissions (CAEE)
recognized that certain information relating to environmental aspects of
aviation should be organized into one document.  This document became
ICAO’s “Annex 16 to the Convention on International Civil Aviation,
International Standards and Recommended Practices, Environmental
Protection” and was split into two volumes – Volume I addressing
Aircraft Noise topics and Volume II addressing Aircraft Engine
Emissions.  Annex 16 has continued to grow and today Annex 16 Volume II
includes a list of mandatory requirements to be satisfied in order for
an aircraft engine to meet the ICAO emission standards.  These
requirements include information relating to engine identification and
characteristics, fuel usage, data from engine testing, data analysis,
and the results derived from the test data.  Additionally, this list of
aircraft engine requirements is supplemented with voluntarily reported
information which has been assembled into an electronic spreadsheet
entitled “Emissions Databank” (EDB) for turbofan engines with
maximum thrust ratings greater than 26.7 kN in order to aid with
emission calculations and analysis as well as help inform the general
public.

In order to understand how current gaseous emission standards are
affecting the current fleet, we need to have access to timely,
representative emissions data of the engine fleet at the requisite model
level.  The EDB is a useful tool for providing a general overview of the
aircraft fleet, as it contains information on engine exhaust emissions
and performance tests.  However, it is not updated on a consistent
basis, it contains a varying amount of voluntarily reported data from
each manufacturer, and it does not specifically list every engine
sub-model.  It also does not contain information on smaller thrust
category turbofans or turboprops, and contains no information on past or
recent engine production volumes.  We need this data to conduct accurate
emission inventories and develop appropriate policy; therefore, the EDB
is not necessarily the proper tool for us to use in order inform our
policy decisions, including future standard-setting actions.
Furthermore, while the situation is unique here, in the context of the
roles of EPA and FAA with regard to aircraft engine emission standards,
it is consistent with EPA policy and practice to ask for timely and
reasonable reporting of emission certification testing and other
information that is relevant to our emission standards.  Under the Clean
Air Act, we are authorized to require manufacturers to establish and
maintain necessary records, make reports, and provide such other
information as we may reasonably require to carry out our functions
under the Act.  See 42 U.S.C. § 7414(a)(1).

Therefore, we are proposing to require the submission of specific
information from any engine manufacturer for each individual engine
submodel that:  1) is designed to propel subsonic aircraft, 2) is
subject to our exhaust emission standards, and 3) has received a U.S.
type certificate.  More specifically, the scope of the proposed report
would include turbofan engines as described above with maximum rated
thrusts greater than 26.7 kN, i.e., those subject to gaseous emission
and smoke standards; in addition to turbofans with maximum rated thrusts
less than or equal to 26.7 kN and all turboprop engines, i.e., those
only subject to smoke standards.  We are also proposing that this
specific exhaust emission related information be reported to us in a
timely manner, which will allow us to conduct proper emissions inventory
analyses of the existing fleet and to ensure that any public policy we
create based on this information will be well informed.

We are proposing to have each affected engine manufacturer report a
reduced number of specific data elements to us as compared to those
already reported voluntarily and periodically by most engine
manufacturers to the EDB.  We feel that this minimizes the reporting
burden for each manufacturer while still providing us with the proper
amount of information we need to do our job.  With the exception of
requiring total annual engine production volumes, all of the specific
reporting items we are proposing are same as requested for the EDB.  We
have assessed the potential reporting burden associated with the
proposed annual reporting requirement.  That assessment is presented in
section V. of this notice.

We are proposing to require the information listed below for each
affected gas turbine engine sub-model in order to establish our own
independent engine exhaust emissions database. We are seeking comment on
the proposed data reporting elements.

•  Company corporate name as listed on the engine type certificate;

•  Calendar year for which reporting;

•  Complete sub-model name (This will generally include the model name
and the sub-model identifier, but may also include an engine type
certificate family identifier.)

•  The type certificate number, as issued by the FAA  (Specify if the
sub-model also has a type certificate issued by a certificating
authority other than the FAA);

•  Date of issue of type certificate and / or exemption, i.e. month
and year;

•  Emission standards to which the engine is certified, i.e. Annex 16,
Volume II, edition number and publication date;

•  If this is a derivative engine, identify the original certified
engine model;

•  Engine sub-model that received the original type certificate for
the engine type certificate family;

•  U.S. directed production volume of the sub-model for the previous
calendar year, or if zero, state that the engine model is not in
production and list the date of manufacture (month and year) of the last
engine produced;

•  Regarding the above production volume report, specify (if known)
the number of engines that are intended for use on new aircraft and the
number intended for use as certified (non-exempt) spare engines on
in-use aircraft;

•  Reference pressure ratio;

•  Combustor description (type of combustor where more than one type
available on an engine);

•  Engine maximum rated thrust output, in kilonewtons (kN) ) or watts
(W) (depending on engine type);

•  Unburned hydrocarbon (HC) mass (g) total (weighted) and over each
segment of the Landing and Take-off Cycle (LTO), i.e. Take-off, Climb,
Approach, Taxi / Ground Idle;

•  Unburned hydrocarbon characteristic level (i.e. mass of
hydrocarbons over LTO cycle / Rated Thrust (Dp/Foo);

•  Carbon monoxide (CO) mass (g) total (weighted) and over each
segment of the entire Landing and Take-off Cycle (LTO) (i.e. Take-off,
Climb, Approach, Taxi / Ground Idle);

•  Carbon monoxide (CO) characteristic level (i.e. mass of CO over LTO
cycle / Rated Thrust (Dp/Foo)) ;

•  Nitrogen oxides (NOx) mass (g) total (weighted) and over each
segment of the entire Landing and Take-off Cycle (LTO) (i.e. Take-off,
Climb, Approach, Taxi / Ground Idle);

•  Nitrogen oxides (NOx) characteristic level (i.e. mass of NOx over
LTO cycle / Rated Thrust (Dp/Foo)).

•  Smoke number total and over each segment of the entire Landing and
Take-off Cycle (LTO) (i.e. Take-off, Climb, Approach, Taxi / Ground
Idle);

•  Smoke number characteristic level;

•  Carbon dioxide (CO2) mass (g) total (weighted) and over each
segment of the entire Landing and Take-off Cycle (LTO), i.e. Take-off,
Climb, Approach, Taxi / Ground Idle;

•  Number of tests run per sub-model;

•  Number of engines tested per sub-model;

•  Fuel flow (grams / second) total (weighted) and over each segment
of the Landing and Take-off Cycle (LTO) (i.e. Take-off, Climb, Approach,
Taxi / Ground Idle); and

•  Any additional remarks to the EPA.

The proposed annual report would be submitted for each calendar year in
which a manufacturer produces any affected gas turbine engine.  These
reports would be due by February 28 of each year, starting with the 2014
calendar year.  This report would be sent to the Designated EPA Program
Officer.  Where information provided for any previous year remains valid
and complete, you may report your production figures and state that
there are no changes instead of resubmitting the original information.
To facilitate and standardize reporting, we expect to specify a
particular format for this reporting in the form of a spreadsheet or
database template that we provide to each manufacturer.  Note that this
annual report does not affect the existing regulatory requirements in §
87.64 to report CO2 and NOx emission data for purposes of greenhouse gas
reporting.  We are, however, clarifying those provisions to specify that
CO2 reporting should be for individual modal values rather than a
weighted composite value. Additionally, both the greenhouse gas
reporting and this reporting will be incorporated into one submission in
order to minimize the reporting burden to the manufacturer.

Our intent for utilizing this proposed reported information is to help
inform any public policy we create, including future emissions
standards, as well as help provide transparency to the general public.
Subject to the applicable requirements of 42 U.S.C. 7414(c), 18 U.S.C.
1905, and 40 CFR part 2, all data received by the Administrator that is
not confidential business information may be posted on our website and
would be updated annually. By collecting and publically posting this
proposed information on EPA’s website, we will be able to calculate
turbine exhaust emission rates and demonstrate to the public how the
fleet meets the current emission requirements. We believe that this
information will also be useful to the general public to help inform
aircraft exhaust emission values.  We ask for comment on our proposed
plan to post this information on our website.

E.  Proposed Standards for Supersonic Aircraft Turbine Engines

We are proposing CO and NOx emission standards for engines that are used
to propel supersonic aircraft to compliment our existing HC standard for
these engines.  These proposed standards were originally adopted by ICAO
in the 1980s, and our adoption of NOx and CO standards for commercial
engines in 1997 omitted coverage of these pollutants for supersonic
commercial engines that were then in use.  The lack of EPA CO and NOx
standards for supersonic aircraft has had no practical effect, because
no such engines have been certified by the FAA.  Also, none of these
engines are currently in production and we are not aware of any
substantive work by engine manufacturers to develop new engine designs
in the immediate future.   However, to meet our treaty obligations under
the Convention on International Civil Aviation as previously described
in section I.B. and to account for the possibility that supersonic
engines could be placed in future use, we believe it is necessary and
appropriate to propose these conforming standards.

F.  Amendments to Test and Measurement Procedures

We are proposing to incorporate by reference into the 40 CFR § 87.60
regulatory text, amendments to ICAO’s International Standards and
Recommended Standards for aircraft engine emissions testing and
certification.  These amendments to Annex 16, Volume II are mainly
intended to ensure that the provisions reflect current certification
practices.  The amendments make clarifications or add flexibilities for
engine manufacturers.  They are described separately below for the
amendments that have already been adopted by ICAO, and those that have
been recommended by CAEP for adoption by ICAO.

The amendments that have already been adopted by ICAO are:

•  Standardizing of the terminology relating to engine thrust/power;

•  Clarifying the need to correct measured results to standard
reference day and reference engine conditions;

•  Allowing a certificating authority to approve the use of test fuels
other than those specified during certification testing;

•  Allowing materials other than stainless steel in the sample
collection equipment; and

•  Clarifying the appropriate value of fuel flow to be used at each
LTO test	point.

The amendments that have been recommended for adoption by ICAO are:

•  Clarifying exhaust nozzle terminology for exhaust emissions
sampling; and

•  Allowing an equivalent procedure for gaseous emission and smoke
measurement if approved by the certificating authority.

The test procedure amendments that ICAO has already adopted became
applicable on November 20, 2008.  The amendments that have been
recommended to ICAO are expected to be adopted prior to the date of the
final action on today’s proposed rule.  Manufacturers are either
already voluntarily complying with these changes or will be even in the
absence of a final rule.  Our adoption of these test procedure
amendments will therefore not likely require new action by manufacturers
beyond what they are already undertaking to meet ICAO’s adopted and
recommended amendments.

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

The high price of jet fuel, current emphasis on fuel economy, and need
to reduce emissions have renewed interest in open rotor propulsion
designs for future aircraft gas turbine engines.  Essentially, the fan
of an open rotor engine is not contained within the nacelle as it is
with a conventional turbofan engine.  This design has also been referred
to as an unducted fan, propfan, or ultra-high bypass engine.  At least
two engine manufacturers are actively pursuing such designs for
certification in the 2018 timeframe.

It now appears that certain aspects of the current gas turbine engine
emission standards may be incompatible with these new designs.  For
example, the current landing and takeoff cycle for emissions
certification is based on conventional engine designs where a
significant amount of thrust is generated by an idling engine.
Specifically, idle emissions are measured and calculated at seven
percent of the engine’s rated thrust.  However, the fan/prop blades of
an open rotor engine may be variable in pitch and this may allow the
blades to be “feathered” at idle.  In that position, the blades are
rotated so very little thrust is generated as the engine idles and
generates emissions.  Also, future aircraft using these engine designs
may fly at somewhat slower speeds.  This might affect the time these
aircraft spend during the climbout mode of the landing and takeoff
cycle.  Therefore, the traditional landing and takeoff cycle used in
turbine engine emissions certification may need to be revised in the
future to accommodate open rotor engines.

We will be working within CAEP to evaluate the differences between
conventional turbine engine and open rotor engine technologies, and to
revise the emission standards and test procedures as appropriate for
these latter engines.  If any changes are required, EPA will undertake
rulemaking to revise our regulations accordingly.

There may also be changes in the emission standards or test procedures
for future supersonic transport (SST) aircraft engines.  The emission
standards for these engines were originally developed in the early 1970s
in response to the Aerospatiale-BAC Concorde.  Since that time, there
have been varying levels of interest in developing a new generation of
supersonic transport.  As a result, the current CAEP work program is
evaluating the status of supersonic aircraft engine development and the
potential need for new emission standards and test procedures.  Our
recent discussions with engine manufacturers indicate that no
substantive work is being undertaken at this time, however.  We will
continue to work within CAEP on this issue and undertake rulemaking to
revise the regulations for supersonic aircraft engines as appropriate.

We request comments on the status and timing of open rotor and future
supersonic engine designs and how the aircraft engine emission standards
and test procedures may need to be modified to accommodate these types
of engines.

IV.  Description of Other Revisions to the Regulatory Text

In addition to the proposed changes discussed above, we are proposing a
number of other changes to the regulatory program.  Most of these
changes are designed to bring the program into conformity with current
technology and current technical or policy practice.  Each of these is
discussed below.

A.  Applicability Issues

This section discusses how the proposed rule relates to engines used in
military and noncommercial civilian aircraft.  We do not believe the
proposed changes would have practical significance for current engine
models because the changes align with manufacturers’ current practice
in certifying their engines.

1.  Military Engines

We are not proposing any specific provisions with respect to engines
installed on military aircraft, and we do not believe our proposal would
have any impact on such engines.  Military aircraft are not required to
have FAA airworthiness certificates, and our 1997 endangerment finding
for NOx and CO emissions and resulting standards did not cover military
aircraft (see 62 FR at 25359).  As such, engines used in military
aircraft are not required to meet EPA emission standards, since our
current regulations define “aircraft” subject to our rules as any
airplane for which a U.S. standard airworthiness certificate (or foreign