vvEPA
Air and Radiation EPA420-R-05-004
November 2005
United States
Environmental Protection
Agency
Emission Standards and
Test Procedures for
Aircraft and Aircraft Engines
Summary and Analysis of
Comments
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EPA420-R-05-004
November 2005
Emission Standards and Test Procedures for
Aircraft and Aircraft Engines
Summary and Analysis of Comments
Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
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Table of Contents
1. Aircraft Engine NOX Standards 1
1.1 Engine NOX Standard Levels and Stringency 1
1.2 Implementation Timeline 6
1.3 Alignment with ICAO Standards 6
1.4 Past Progress of Aircraft Engine Emissions 11
1.5 Future Standards 13
1.6 Long-Term Technology Goals 17
2. Applying the NOX Standards to Newly Manufactured Engines of Already Certified
Models (Production Cut-off) 19
3. Environmental Need for Control 25
3.1 Overall Air Quality Need 25
3.2 Aircraft Emissions Contribution 27
4. Approaches to Additional Aviation Emission Reductions 32
5. Other Issues 36
5.1 Environmental Justice 36
5.2 General Aviation and Military Aircraft 37
5.3 Auxiliary Power Units 39
5.4 Ground Service Equipment 40
5.5 Lead from Aviation Gasoline 40
5.6 Limits for Hydrocarbons, Particulate Matter, Air Toxics, and Sulfur Dioxide 43
5.7 Interrelationships on Pollutants, Noise, and Performance 44
5.8 Regulations for Airports 44
5.9 Greenhouse Gases 45
5.10 Altitude Where the Majority of Aircraft Emissions Occur 46
5.11 Contrails 46
5.12 Deicing 48
5.13 Airport Water and Noise Pollution 48
5.14 Effect of September 11, 2001 and Economic Downturn on Emissions Growth 48
5.15 Funding Clean Engine Research 49
5.16 Voting Representation in the CAEP Process 50
5.17 Accuracy of Method to Determine Visibility 50
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Introduction
On September 30, 2003, we published a Notice of Proposed Rulemaking (NPRM) for
proposed amendments to existing emission standards for oxides of nitrogen (NOX) for newly
certified commercial aircraft gas turbine engines with rated thrust greater than 26.7 kilonewtons
(kN). These proposed standards are equivalent to the existing (effective in 2004) NOX standards
of the United Nations International Civil Aviation Organization (ICAO), and thereby bring the
United States emission standards into alignment with the internationally adopted standards. The
NPRM also proposed to amend the test procedures for gaseous exhaust emissions to correspond
to recent amendments to the ICAO test procedures for these emissions. In addition, we also took
comment on applying the proposed NOX standards to newly manufactured engines of already
certified models (a production cut-off).
We held a public hearing on the NPRM in Washington, D.C. on November 13, 2003. At
that hearing, oral comments on the NPRM were received and recorded. A written comment
period remained open until December 15, 2003. A complete list of organizations and individuals
that provided comments on the NPRM is contained in the following table. Abbreviations for the
organization names are also included.
This Summary and Analysis of Comments contains a detailed summary of all comments
we received on the NPRM as well as our analysis of each comment and response. The reader
should also refer to the final rulemaking notice in the Federal Register.
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List of Commenters with Acronyms and EDOCKET Reference Numbers
Commenter Acronym
Aerospace Industries Association of America, Inc. (OAR-2002-0030-0113) AIA
Air Transport Association of America, Inc. (OAR-2002-0030-0100) ATA
Air Transport Association of America, Inc. (OAR-2002-0030-0109) ATA
Airports Council International - North America; and
the American Assoc. of Airport Executives (OAR-2002-0030-0119) ACI-NA&AAAE
Alliance of Residents Concerning O'Hare (OAR-2002-0030-0099) AReCO
Anonymous (OAR-2002-0030-0024) -
Anonymous (OAR-2002-0030-0065) -
Anonymous (OAR-2002-0030-0066) -
Anonymous (OAR-2002-0030-0069) -
Anonymous (OAR-2002-0030-0103) -
Bluewater Network (OAR-2002-0030-0096) Blue water Network
California Air Resources Board (OAR-2002-0030-0123) CARB
Center for Clean Air Policy (OAR-2002-0030-0098) CCAP
Center for Clean Air Policy (OAR-2002-0030-0122) CCAP
Clark, Bonnie (OAR-2002-0030-0068) -
Delta Air Lines, Inc. (OAR-2002-0030-0114) Delta
Environmental Defense (OAR-2002-0030-0097) ED
Environmental Defense (OAR-2002-0030-0111) ED
Geiser, Kathleen (OAR-2002-0030-0067) -
Georgia Department of Natural Resources (OAR-2002-0030-0112) GA DNR
Golden Gate University School of Law (on behalf of Bluewater Network) Bluewater Network
(OAR-2002-0030-0106)
Golden Gate University School of Law (on behalf of Bluewater Network) Bluewater Network
(OAR-2002-0030-0107) - Attachment to above comment
New York State Dept. of Environmental Conservation (OAR-2002-0030-0115) NYSDEC
Pederson, Holger (OAR-2002-0030-0062) -
Sachau, B. (OAR-2002-0030-0063) -
Sachau, B. (OAR-2002-0030-0094) -
South Coast Air Quality Mgt. District (OAR-2002-0030-0104) SCAQMD
STAPPA/ALAPCO (OAR-2002-0030-0095) STAPPA/ALAPCO
STAPPA/ALAPCO (OAR-2002-0030-0116) STAPPA/ALAPCO
Starr, Seti (OAR-2002-0030-0064) -
State of New Jersey Dept. of Environmental Protection (OAR-2002-0030-0101) NJDEP
Texas Commission on Environmental Quality (OAR-2002-0030-0120) TCEQ
Public Hearing Testimony (OAR-2002-0030-0121) (November 13, 2003, Washington, D.C.)
Air Transport Association of America, Inc.
Alliance of Residents Concerning O'Hare
Bluewater Network
Center for Clean Air Policy
Environmental Defense
STAPPA/ALAPCO
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1. Aircraft Engine NOX Standards
What We Proposed:
The comments in this section correspond to Sections II and IV of the NPRM, and
therefore are targeted at issues dealing with the proposed aircraft engine NOX standards. A
summary of the comments received, as well as our responses to those comments are located
below. For the full text of comments summarized here, please refer to the public record for this
rulemaking.
1.1 Engine NOX Standard Levels and Stringency
What Commenters Said:
We received a number of comments from state and local governments and environmental
groups stating that the proposed NOX standards should be technology-forcing standards (a
performance level that is beyond what sources are currently achieving). Emission standards
should "point the way" and decrease emissions comparable to other sources. The California Air
Resources Board (CARB) urged EPA to finalize the proposed rule, but they suggested at the
same time that "it does not represent an advancement in emission control technology."
Commenters noted that the proposed standards merely establish consistency with international
and U.S. standards. They stated that the standards are not technology forcing since 94 percent of
all engine models currently in production already meet the proposed standards (85 percent did in
1999 when the ICAO adopted the standards). Furthermore, STAPPA/ALAPCO expressed that
the combined effect of the proposed standards with the previously promulgated NOX standards
(which also were not technology forcing) will only be about a 40 to 50 percent reduction in NOX
emissions from new engine models relative to uncontrolled levels of emissions. In comparison,
all other sources are "controlled to well over 50 percent and some as high as 95 percent." The
New York State Department of Environmental Conservation (NYSDEC) stated that EPA has
already promulgated aggressive NOX regulations for many mobile sources (resulting in over 90
percent NOX reductions in respective categories), including Tier 2 light-duty vehicle standards,
2007 heavy-duty diesel standards, and recent heavy-duty nonroad standards. In addition, the
Alliance of Residents Concerning O'Hare (AReCO) urged us to set aircraft NOX standards at a
level in which "90% of existing fleet engines could not meet it."
State and local governments and environmental groups expressed that since the proposed
standards are not technology-forcing and most engines already meet the standards, aircraft
engine NOX will increase. Furthermore, aircraft emissions will increase (without technology-
forcing standards) because the standards are rate-based, and the projected growth in aircraft
operations (despite the temporary setback in activity following the tragic events of September
11, 2001) outpaces the rate of improvement in emissions-intensity of the standards. The
proposed standards apply only to newly designed or certified engines, and since aircraft operate
in the fleet for a long time (long life/slow turnover of fleet), "the new standards will have a
limited impact on overall emission levels for quite some time" (weak standards will have a long
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lasting impact on air quality since aircraft engines typically last 30 years). Also, commenters
expressed concern the many states are facing air quality challenges with implementation of the
new 8-hour ozone standard and fine particulate matter (PM2 5) national ambient air quality
standards (NAAQS). Decreases in ozone and PM25 precursors, including NOX, require control of
emissions from all sectors, in addition to controls already implemented for 1-hour ozone
NAAQS. For nonattainment areas, aircraft emissions are problematic, and the proposed
standards will not reduce aircraft emissions or address aircraft NOX pollution. Furthermore,
emission reductions from other sources are hard to find. Increasingly stringent standards for
other sources are reducing their pollution, but aircraft NOX continues to increase in lieu of
constraining standards. Commenters urged EPA to not miss an opportunity to establish strong
standards for aircraft when there is a great need for reductions. The Environmental Defense
(ED) suggested that EPA conduct a thorough technology and control strategy review of aircraft
engines prior to establishing standards for these major sources of pollution. The resulting
standards from such a review should lead to downward trend in aircraft emissions.
Bluewater Network expressed that EPA has the authority to adopt technology-forcing
standards according to section 231 of the Clean Air Act (CAA), because section 231 states that
EPA is required to issue standards with sufficient lead time "to permit the development and
application of the requisite technology." In addition, states and local governments and
environmental groups indicated that EPA's failure to propose technology forcing standards is
unfortunate since only EPA (and not states) can effectively regulate aircraft emissions based on
section 233 of the CAA. States are dependent on EPA and the Federal Aviation Administration
(FAA) to control growing aircraft emissions. The Texas Commission on Environmental Quality
(TCEQ) expressed that the fraction of emissions from federal sources has significantly increased
as states adopt control strategies on other sources, and thus, the challenge that states encounter in
creating 8-hour ozone implementation plans substantially increases. ED indicated that the
meager proposed standard will only make it more difficult for states to develop clean air plans.
The limited state authority highlights the necessity of rigorous federal standards.
In addition, Bluewater Network suggested that technology-forcing standards are long
overdue. In 1997, when EPA last revised aircraft emission standards, "EPA adopted standards
that most or all of the engines were already meeting. Compounding the problem, EPA's
adoption of the standards came after ten years of inaction." Now six years later, EPA is again
proposing to adopt standards "that most engines already meet." With many Americans forced to
breathe unhealthy air, "it is time EPA changed its course to adopt technology-forcing standards
that Congress authorized in section 231 of the Act."
Engine and airframe manufacturers and air carriers supported the proposed standards and
opposed the concept of technology-forcing standards. The Air Transport Association of
America, Inc. (ATA) indicated that the proposed rulemaking would codify aircraft emission
standards determined to be technologically feasible. In addition, ATA expressed that
technology-forcing standards would be contrary to the CAA. Aircraft engine emission standards
adopted according section 231 of the CAA must be based on what is technologically feasible,
and the standards cannot be amended if the change would significantly increase noise or
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adversely affect safety. ATA suggested that a technology-forcing NOX standard could adversely
affect noise and safety. In addition, they indicated that section 231 of the Act is different from
other sections of the CAA that call for technology-forcing standards. ATA expressed that
section 231 requires that standards already be technologically feasible and not compromise noise
and safety.
ATA indicated that technology-forcing standards would be based on the promise of
developing technology, and such technology would not have been through rigorous certification
testing that ensures safe flight. Manufacturers may have to compromise performance factors that
implicate safety to meet technology-forcing standards. A technology review would not avert this
risk since, with or without such a review, the technology will ultimately have to be certified to
safety standards of the FAA. Any technology that does not meet those standards with sufficient
margin may eventually come across regulatory roadblocks.
Also, ATA suggested that due to high development costs and the inherent uncertainty of
technological development, there is not a guarantee that even promising technology can become
a certified product. Technology-forcing standards would create market distortions in
manufacturing, which would lead to a diminished choice of products being available for airlines
to serve a range of required missions and raising the cost of products that are available.
In addition, ATA expressed that whether a "standard is technologically feasible depends
not just on whether it can be achieved in a laboratory setting, but whether it can be achieved on a
range of actual aircraft engine and airframe combinations that are certified as airworthy, safe,
and fully operable under flight conditions. Moreover, such demonstrated technology must be
available for application over a sufficient range of newly certificated aircraft, not just on a few
airframe/engine combinations."
Aerospace Industries Association of America, Inc. (AIA) stated that "[m]arket forces and
reasonable standards, based on best available certification technology, will encourage the
development and introduction of this technology into service." Attempting to change this
process by introducing standards that require unproven technologies will have an adverse
environmental impact. "Introduction of new technology will be delayed until it can become
technologically feasible, certifiable and cost effective. Investments in technology development
may actually decrease because of projected small markets and increased failure risks, further
delaying its introduction." Also, AIA suggested that the current (or ICAO) process has been
shown to work, and it will continue to encourage the development of new technology in the
future.
Our Response:
We refer to sections 23 l(a)(2)(B) and (b) of the CAA. Section 23 l(b) requires that any
emission standards "take effect after such period as the Administrator finds necessary (after
consultation with the Secretary of Transportation) to permit the development and application of
the requisite technology, giving appropriate consideration to the cost of compliance during such
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period." 42 U.S.C. §7571(b). Section 23 l(a)(2)(B) provides that the Administrator shall consult
with the Administrator of the FAA on standards, and "shall not change the aircraft engine
emission standards if such change would significantly increase noise and adversely affect
safety." 42 U.S.C. §7571(a)(2)(B). Future aircraft emission standards will involve appropriate
consultations between EPA and the FAA in applying these provisions of the CAA.
EPA also needs to have a technical basis for expecting the standards will be achievable in
a specific period of time. While the statutory language of section 231 is not identical to other
provisions in title II of the CAA that direct EPA to establish technology-based standards for
various types of engines, EPA interprets its authority under section 231 to be somewhat similar
to those provisions that require us to identify a reasonable balance of specified emissions
reduction, cost, safety, noise, and other factors. See, e.g.. Husqvarna AB v. EPA. 254 F.3d 195
(D.C. Cir. 2001) (upholding EPA's promulgation of technology-based standards for small non-
road engines under section 213(a)(3) of the CAA). However, we are not compelled under
section 231 to obtain the "greatest degree of emission reduction achievable" as per sections 213
and 202 of the CAA, and so EPA does not interpret the Act as requiring the agency to give
subordinate status to factors such as cost and safety and noise in determining what standards are
reasonable for aircraft engines. Rather, EPA has greater flexibility under section 231 in
determining what standard is most reasonable for aircraft engines, and is not required to achieve
a "technology-forcing" result. The fact that most engines already meet standards would not in
itself mean that the standard is inappropriate, provided the agency has a reasonable basis after
considering all the relevant factors for setting the standard (with an appropriate period of lead
time for that standard) at a level that results in no actual emissions reduction from the baseline.
By the same token, EPA does not agree that a technology-forcing standard would be
precluded by section 231, in light of section 23 l(b)'s forward-looking language. Nor would
EPA have to demonstrate that a technology is currently available universally or over a broad
range of aircraft in order to base a standard on the emissions performance of such technology -
the agency is not limited in identifying what is "technologically feasible" as what is already
technologically achieved. However, EPA would, after consultation with the Secretary of
Transportation, need to provide manufacturers sufficient lead time to develop and implement
requisite technology. As section 231 conveys, there is an added emphasis on the consideration
of safety (see, e.g.. sections 231(a)(2)(B)(ii) ("The Administrator shall not change the aircraft
engine emission standards if such change would [. . .] adversely affect safety") and 231(c) ("Any
regulations in effect under this section [. . .] shall not apply if disapproved by the President, after
notice and opportunity for public hearing, on the basis of a finding by the Secretary of
Transportation that any such regulation would create a hazard to aircraft safety"). Therefore, it
is reasonable for EPA to give greater weight to considerations of safety in this context than it
might in balancing emissions reduction, cost, and energy factors under other title II provisions.
In regard to the comments that technology-forcing standards would create market
distortions in manufacturing (and lead to cost increases of available products) and potentially
decrease investments in technology development, we are not in a position to respond since the
commenters did not submit data or information to support these comments.
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In addition, EPA has authority to under section 23 l(a)(2)(A) to revise emission standards
from "time to time." Since we have already gone past the implementation date of standards
adopted at the fourth meeting of ICAO's Committee on Aviation Environmental Protection
(CAEP/4) - implementation date of December 31, 2003 — and that are equivalent to the
proposed standards, there is not sufficient lead time to require more stringent emission standards
in the very near term. EPA intends to address more stringent emission standards requiring more
lead time in a future rulemaking (see later discussion on future standards in section 1.5). Thus,
EPA will promulgate the proposed standards in this final rulemaking. CAEP/6, which occurred
in February 2004, adopted more stringent international consensus NOX emission standards for
aircraft engines (implementation date of after December 31, 2007), and earlier this year the
ICAO Council approved these standards.1'2 Such standards will be a central consideration in a
future EPA regulation of aircraft engine emissions. We believe this ongoing phased approach is
the most appropriate means to address emissions from aircraft engines.
Moreover, this final rule to promulgate aircraft engine NOX standards equivalent to
CAEP/4 standards is an interim measure that is in accordance with U.S. obligations under ICAO.
By issuing standards that meet or exceed the minimum stringency levels of ICAO CAEP/4
standards, we satisfy these obligations (see section 1.3, Alignment with ICAO Standards, for
further discussion of this issue). As indicated above, the implementation date, December 31,
2003, has already occurred for the CAEP/4 standards, and we need to promulgate the proposed
standards soon to meet our obligations for the CAEP/4 standards. In addition, we would not be
able to quickly adopt a more stringent standard. However, as described earlier, we intend to
consider further stringency in a future rulemaking. In addition, as discussed later in our response
in section 1.5 (Future Standards), we have not yet assessed the costs (and emission benefits) of
more stringent standards, but we anticipate doing so in the future for such standards.
EPA is aware that many states face air quality challenges in light of the new ozone and
PM2 5 NAAQS, and since section 233 of the CAA vests authority only in EPA to set aircraft
emission standards, we understand their perspective regarding the importance of setting more
stringent NOX standards in the future. For these future standards, we expect to adopt standards
developed through the CAEP process in ICAO. Further, federal agencies plan on working
through the environmental Integrated Product Team for the Next Generation Air Transportation
System (NGATS), to conduct a review of technology for aircraft engines and the resulting trend
in aircraft emissions as well as interrelationships with noise (e.g., standards effect on projected
aircraft emissions growth and expected effects on noise).
JThe CAEP/6 NOX standards generally represent about a 12 percent increase in stringency
from the standards promulgated in this final rule.
2ICAO News Release, "ICAO Council Adopts New Standards for Aircraft Emissions,"
PIO 03/05, March 2, 2005. Copies of this document can be obtained at the ICAO website
located at www.icao.int.
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1.2 Implementation Timeline
What Commenters Said:
States and local governments and environmental groups expressed that since ICAO
adopted equivalent standards in 1999, engine manufacturers have been designing engines to
meet the proposed standards for four years. There was plenty of time to meet the standards.
Adopting these standards at this late date will not impact engine designs, and thus, expected
aircraft emissions. If EPA had acted sooner, the Agency could have enacted standards by
January 2004 that provided critically needed emissions reductions. Yet, because of the
inexplicable delay, EPA is accurate to state that "at this time, there is not sufficient lead time to
require more stringent emission standards ... by January 2004."
ATA indicated that while they support the proposed rule to adopt NOX standards
equivalent to ICAO standards, they believe it would have been better if it had occurred sooner.
Given market forces, upon the adoption of the standards by ICAO in 1999, manufacturers began
in earnest to comply with the standard, even though the standards were not implemented until
January 1, 2004. To show a commitment to ICAO standards and more orderly progress for U.S.
standards, EPA should have taken steps to adopt the ICAO standards immediately.
Our Response:
We agree with the view expressed by commenters that it would have been preferable to
adopt standards sooner. However, as discussed above there is currently not enough lead time to
mandate more stringent standards requiring near-term compliance, and thus, EPA plans to
address more stringent standards in a future rule. Moreover, our adoption of standards
equivalent to CAEP/4 standards at this point in time has not resulted in any appreciable loss of
aircraft emissions reduction, given that manufacturers are already voluntarily complying with
CAEP/4 requirements.
1.3 Alignment with ICAO Standards
What Commenters Said:
Bluewater Network urged EPA to take independent action as envisioned by Congress to
set technology-forcing standards, instead of merely adopting the ICAO standards. If Congress
had intended for the international standards to be the ceiling, Congress would have explicitly
stated that in the CAA. Furthermore, because Congress was concerned about FAA regulating
aircraft emissions, they explicitly gave that authority to EPA. However, by adopting ICAO's
CAEP standards, in which the official representative from the U.S. is the FAA, EPA is doing
exactly the opposite of what Congress had intended.
NJ suggested that by simply matching CAEP emission standards, the Agency is missing
an important opportunity to tighten restrictions more, thus allowing the U.S. to be a leader in
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improving emissions from aircraft. CARB expressed that U.S. should take a leadership role in
advancing cleaner engine technology. EPA and FAA should advocate for NOX emission controls
that meet NASA's 70 percent reduction target at CAEP/6. In addition, STAPPA/ALAPCO
indicated that since it is EPA's responsibility to make certain appropriate measures are taken to
protect human health from environmental harm, EPA must also play a stronger role in setting the
U.S. position on environmental matters within ICAO.
ATA expressed that the proposed rule to adopt CAEP/4 standards recognizes the
imperative for preserving consistency in international aircraft emission standards as established
through ICAO procedures, which account for safety matters unique to aviation. It also is a
proper use of EPA's standard-setting role provided under the CAA. The proposed rule follows
the Agency's "precedent of supporting international consistency while advancing environmental
goals." Delta Air Lines, Inc. (Delta) also supports the proposed rule to align U.S. emission
standards and test procedures with ICAO. Airports Council International - North America and
the American Association of Airport Executives (ACI-NA&AAAE) suggested that the proposed
alignment of U.S. standards with ICAO standards is one essential element in their efforts to
reduce emissions at airports. AIA commented that they support the ICAO/CAEP process for
setting recommendations for emission standards.
ATA stated that since aviation is a global industry, it is necessary that it function "under
uniform, internationally recognized standards and procedures." If a country does not adopt an
ICAO standard and files a notification of difference, the activity of aircraft certified by that
country may be affected in nations where the ICAO standard does apply. Based on its
obligations under the Chicago Convention, the U.S. needs to follow the ICAO standards in order
that U.S. registered air carriers will be allowed to operate internationally without unnecessary
and inconsistent restriction by other nations. Even though the proposed rule pertains to a NOX
standard only, the ongoing viability of an established United Nations organization, ICAO, to set
global "consensus standards on safety, security, environmental, air traffic, and other parameters
that allow international aviation to function" is at stake.
In addition, ATA commented that standards that have come from the rigorous CAEP and
ICAO review process of the CAEP/4 standards are the only proper reference point for the EPA
to use its standard setting authority under section 231 of the CAA. Even though CAEP functions
under a wider mandate compared to any agency's statutory authority, CAEP's deliberations
covered the factors that the CAA requires EPA and FAA to evaluate when setting emission
standards for aircraft engines. If the U.S. differs from CAEP/4 emission standards, after
participating in its development and supporting its adoption at ICAO, such a course of action
would undermine ICAO and its ability to set needed emission standards. Any diversion from
CAEP/4, would also undermine U.S. national interest by allowing conflicting agendas for
standard setting, which could weaken the competitiveness of U.S. technology. Moreover, ACI-
NA&AAAE expressed that to make sure U.S.-manufactured aircraft engines are not at a
disadvantage, all engines should be made to meet the international standards from ICAO.
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In addition, Delta Air Lines, Inc. suggested that a nation that chooses not to adopt CAEP
standards is at risk of other member nations deciding not to recognize their air carriers'
airworthiness certificates. Issuing standards that are not aligned with ICAO/CAEP undermines
the mission of ICAO/CAEP and could effect international activity of Delta and other airlines
based in the U.S. Further stringency beyond CAEP standards would result in an additional
economic burden to Delta and other domestic airlines not applicable to other international air
carriers.
Also, ATA indicated that the ICAO/CAEP standard setting process establishes the basis
for the adoption of standards by EPA. ICAO/CAEP has approved four terms of reference for
setting aircraft emission standards: technologically feasible, economically reasonable,
environmentally beneficial, and balanced to account for interrelationships between emissions
and noise. CAEP's assessment of each of these criteria is directly related to the deliberations
that EPA and FAA must make when establishing aircraft emission standards under section 231
of the CAA. ATA commented that EPA and FAA contributed actively to the technical-
feasibility analysis that CAEP's emissions technical-issues workgroup (WG3) undertook for
CAEP/4 standards, and the recommendations by WG3 were accepted by the U.S., CAEP, and the
ICAO Council.
In addition, Delta Air Lines, Inc. and ACI-NA&AAAE commented that the CAEP/4
standards were developed based on thorough consideration of technical feasibility, economic
reasonableness, and environmental benefit by ICAO/CAEP. ACI-NA&AAAE also suggested
that these criteria make certain that there is a successful program of emission reductions for
nearly all sources, and such criteria are consistent with section 231 of the CAA. AIA
commented that the ICAO/CAEP process has proven to be effective since it considers these three
principles, and it "encourages technology development and the safe introduction of that
technology into manufactured products in a cost effective and environmentally responsible
matter."
In regard to economic reasonableness, ATA expressed that an extensive cost/benefit
analysis was conducted for the CAEP/4 standards, and the CAEP workgroup that performed the
analysis concluded that the standard was economically reasonable. CAEP and the ICAO
Council concurred. As a legal matter such a finding by CAEP is important because the CAA
directs EPA and FAA to account for the cost of aircraft standards.
As for environmental benefits and interrelationships, ATA indicated that CAEP/4 found
that the recommended further stringency was the most beneficial NOX reduction that could be
attained without risking CO2 increases. The CAEP/4 standard set a floor for NOX levels of future
production engines, without worsening the concerns about the potential climate change impacts
of CO2. ATA stated that it would be unsound policy for EPA to deal with aircraft NOX in
isolation, an approach inconsistent with international standards.
Our Response:
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The Chicago Convention does not require all Contracting States to adopt identical
airworthiness standards. Although the Convention urges a high degree of uniformity, it is
expected that States will adopt their own airworthiness standards, and it is anticipated that some
states may adopt standards that are more stringent than those agreed upon by ICAO. However,
because any State can ban use within its airspace of any aircraft that does not meet ICAO
standards, States that wish to use aircraft in international air transportation have agreed to adopt
standards that meet or exceed the stringency levels of ICAO standards.3 Because States are
required to recognize certificates of any State whose standards meet or exceed ICAO standards,
a State is assured its aircraft will be permitted to operate in any other Contracting State if its
standards meet or exceed the minimum stringency levels of ICAO standards.
As long as a participating nation of ICAO adopts aircraft emission standards that are
equal to or more stringent than ICAO's standards, the certificates of airworthiness for such
nations are valid. Thus, aircraft belonging to countries with more stringent standards are
permitted to travel through the airspace of other countries without any restriction. To ensure
operation internationally without constraints, a participating nation which elects to adopt more
stringent standards is obligated to notify ICAO of the differences between its standards and
ICAO standards.4 However, if a nation sets tighter standards than ICAO, air carriers not based
in that nation (foreign-flag carriers) would only be required to comply with the ICAO standards.
Section 231 of the CAA directs EPA, from time to time, to propose aircraft engine
emission standards for any air pollutant that may reasonably be anticipated to endanger public
health and welfare. In addition, EPA is required to make certain such standards' effective dates
permit the development of necessary technology, giving appropriate consideration to compliance
cost. We must adhere to section 231, and nothing in the Chicago Convention or ICAO/CAEP
3Text of Article 33 of Chicago Convention:
Certificates of airworthiness and certificates of competency and licenses issued or rendered valid
by the contracting State in which the aircraft is registered, shall be recognized as valid by the
other contracting States, provided that the requirements under which such certificates or licenses
were issued or rendered valid are equal to or above the minimum standards which may be
established from time to time pursuant to this Convention.
4Text of Article 38 of Chicago Convention:
Any State which finds it impracticable to comply in all respects with any such international
standard or procedure, or to bring its own regulations or practices into full accord with any
international standard or procedure after amendment of the latter, or which deems it necessary to
adopt regulations or practices differing in any particular respect from those established by an
international standard, shall give immediate notification to the International Civil Aviation
Organization of the differences between its own practice and that established by the international
standard .... In any such case, the Council shall make immediate notification to all other states
of the difference which exists between one or more features of an international standard and the
corresponding national practice of that State.
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terms of reference for setting aircraft emission standards would supercede these CAA
responsibilities. It is therefore permissible for the U.S. to adopt standards that differ from ICAO
standards. Although it is not our intent at this time, it is plausible that we could in the future
adopt an aircraft emission standard that is tighter than the ICAO standards due to the possible
unique environmental and health concerns found in the U.S. If this was the case, we understand
that domestic air carriers could be at a disadvantage to other international carriers since they
would have to comply with such a standard and other carriers would not. However, before
proposing such a standard we would, of course, give appropriate consideration to cost according
to the CAA. It is important to note that according to 1999 data foreign flag carriers only made
up about 3 percent of major carrier operations in the U.S.,5 and thus, it would seem that the
environmental benefit in the U.S. from more stringent standards could outweigh any potential
competitive issues with foreign carriers. In addition, there might not be competitive issues
between manufacturers since domestic and foreign manufacturers would have to meet the same
requirements to sell compliant engines to U.S. registered air carriers.
As we stated in the proposed rule because aircraft and aircraft engines are international
commodities, there is commercial benefit to consistency between U.S. and international emission
standards. Manufacturers would only have to design to one emission standard globally, and air
carriers would only need to be concerned with making sure the engines installed on their aircraft
meet one standard. Such harmonization has economic and record keeping (and reporting)
benefits. Moreover, since aircraft and their engines operate throughout the world on a daily
basis, one standard may be the most efficient mechanism for meeting international
environmental goals. Before issuing these aircraft engine NOX standards, we have taken into
account compliance costs (according to the CAA), which includes consideration of economic
effects pertaining to consistency with international standards. However, alignment with
international standards was not the sole consideration (we also evaluated technology
development, safety, etc.). As stated above, we anticipate setting tighter NOX standards in the
future since there is currently not enough lead time to do so. For this ongoing phased approach
in establishing standards, we will adhere to our CAA mandate and consider all criteria specified
in section 231 to address aircraft engine emissions.
5Data Base Products Inc. compiled and summarized information from the below data sets.
Domestic carrier data: U.S. DOT, Bureau of Transportation Statistics, "Airport Activity
Statistics of Certificated Air Carriers," Twelve Months Ending December 31, 1999. Foreign-
flag carrier data: Total departures, foreign carriers, all U.S. airports combined, CY 1999, T-100
data from DOT.
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1.4 Past Progress of Aircraft Engine Emissions
What Commenters Said:
The Georgia Department of Natural Resources (GA DNR) expressed that the proposed
standards were adopted at ICAO's CAEP/4, and ICAO's standards historically follow aviation
technology (85 percent of engines already met the CAEP/4 standards when then were approved
in 1999 and today 94 percent of engines meet the CAEP/4 standards). The South Coast Air
Quality Management District (SCAQMD) suggested that "aircraft emission standards have not
been adequately developed and implemented by EPA to address the growing impact of aircraft
emissions on air quality and historically aircraft have been under-regulated as compared to other
sources."
ED indicated that the General Accounting Office's (GAO) February 2003 report,
Aviation and the Environment: Strategic Framework Needed to Address Challenges Posed by
Aircraft Emissions., showed that even though new aircraft engines are more fuel efficient and
emit less carbon monoxide (CO), they emit more NOX than older engine models. EPA needs to
reconcile this finding with the statements in the NPRM that 94 percent of in-production engines
already meet or perform better than the proposed NOX standards. ED questioned whether these
new standards would have an impact "on newer aircraft engines that are in some cases much
dirtier than older engines." At a minimum, the rulemaking needs to explain this apparent
discrepancy.
AIA expressed that "[historically, the aircraft industry has responded favorably to
standards based on best available technology that has demonstrated safety and airworthiness." A
look back at past standards will show that by the time a new standard is implemented industry
has taken voluntary action, where technologically feasible, to meet those standards, in most
cases, many years ahead of the implementation date. "The same can be said for the CAEP/4
standard." In 1998, four engine families in-production and three new type engine families did
not meet the standard, and as of December 2003, only two in-production engines will not meet
this standard. "For one of those engines, a technology has been identified to meet the standard,
and market forces will dictate its introduction into service." This shows that the proposed
standard allows development of the necessary technology while giving appropriate consideration
to the cost of compliance.
ATA suggested that while manufacturers have continued to improve NOX, they have also
attained marked improvements in fuel efficiency - 125 percent since 1975 according to FAA
statistics (with corresponding carbon dioxide emission reductions). In the same time frame, the
U.S. has decreased the population exposed to significant levels of aircraft noise from over 7
million to fewer than 500,000, while enplanements have tripled. In addition, there have been
continued decreases in carbon monoxide, hydrocarbons, and smoke. Moreover, Delta Air Lines,
Inc. indicated that the international air carrier industry holistically has demonstrated continued
proactive behavior in decreasing pollution (both air and noise) from aviation. Because of the
proactiveness of industry, 94 percent of the in-production engines already meet or perform better
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than the proposed NOX standards. Delta Air Lines, Inc. commented that "[tjhese achievements,
and ongoing work within ICAO, show the industry's commitment to reducing pollution without
the need for further burdensome regulations."
Our Response:
We would agree that historically aircraft standards have not had the tighter stringency
that some other sources have had. As stated earlier, section 23 l(b) permits EPA to set aircraft
emission standards at a level that is currently not achieved in practice if we provide sufficient
lead time for development of technology before such standards must be met. However, we are
not compelled under section 231 to obtain the "greatest degree of emission reduction achievable"
as per section 213 (nonroad standards) and 202 (on-highway standards) of the CAA.
In regard to the finding in the GAO report that new aircraft engines emit more NOX than
older engines models (but emit less carbon monoxide and are more fuel efficient), we believe
some additional context is needed. As pointed out in the report, there are engine technologies
that manufacturers have developed for some newer engines now in service such as Pratt and
Whitney's Technology for Affordable Low NOX (TALON) that reduce NOX. Also, the 1999
Intergovernmental Panel on Climate Change report entitled, Aviation and the Global Atmosphere
stated that "[tjhere is no single relationship between NOX and CO2 that holds for all engine types.
However, for the best current aircraft engine and combustor design, there is a direct link between
the emissions of NOX and CO2. As the temperatures and pressures in the combustors are
increased to obtain better fuel efficiency, emissions of NOX increase, unless there is also a
change in combustor technology."6 In addition, it is difficult to compare old and new aircraft
due to the many differences (e.g., range, number of passengers, fuel and structural weight,
performance, etc.) between otherwise similar aircraft. For instance, similar aircraft of the same
series could carry almost an identical number of passengers; however, the newest aircraft may
have twice the range of the older aircraft. There would likely be an increase in emissions from
the newest aircraft for carrying the additional fuel and structural weight, but there may be
benefits as well. For a mission well suited to the newest aircraft, the older aircraft might need an
intermediate stop (and/or additional landing and takeoff), which may lead to more emissions that
affect local air quality. Also, when comparing older and similar aircraft of the same series,
which used the same engine, nearly identical emissions could be reported even though one of the
older aircraft may be able to carry substantially more passengers. Such results may be due to
6Reference provided in IPCC report: ICCAIA, Emissions Technology Review, Working
Paper 3/11 presented at the 3rd meeting of ICAO/CAEP Working Group 3 (Emissions-Technical
Issues), Savannah, GA, May 1997.
Intergovernmental Panel on Climate Change (IPCC), "Aviation and the Global
Atmosphere," I.E. Penner, D.H. Lister, D. J. Griggs, D. J. Dokken, and M. McFarland, editors.
Cambridge University Press, 1999.
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model limitations, and it may not be a valid comparison of the two aircraft. Overall, an engine to
engine comparison would probably show less of a NOX increase from old to new.
As for the effect the standards will have on newer engines, it is important to note that the
levels of the proposed and previous NOX standards increases as the engine pressure ratio
increases (the NOX standard varies with and is a function of an engines pressure ratio), and based
on available information some new engines will have low and medium engine pressure ratios
(less than or equal to 30) and others will have high pressure ratios (greater than 30). These new
engines are not expected to be all high pressure ratio engines, and thus the effect of the standards
will vary. Also, regardless of the engine pressure ratio, the proposed (and promulgated)
standards are never less stringent than the previous standards. In addition, as stated in the
NPRM and the preamble of the final rule, we will codify current practice (NOX standards will
ensure that new engine designs incorporate the existing combustor technology), with no
significant lead time, as a near-term approach, and we intend to address more stringent emission
standards requiring more lead time in a future rulemaking
Even with the overall growth in aviation emissions (continued increases in aviation
activity are directly related), we recognize that since the 1970's industry has made continued
improvements in the pollution emitted from the aircraft technology. However, as described in
section 3 below (Environmental Need for Control) and section II of the preamble for the final
rulemaking, many areas in U.S. have air quality problems and will have a difficult time meeting
the new 8-hour ozone and PM25 NAAQS without decreasing aircraft emissions, which continue
to grow. As previously discussed, today's standards will lead to minimal emission reductions,
and thus, we intend to address more stringent NOX standards in the future. We believe this
ongoing phased approach is the most appropriate way to address aircraft engine emissions at this
time.
1.5 Future Standards
What Commenters Said:
States and local governments expressed that EPA "has an obligation to immediately
follow this rulemaking with further, more aggressive action, taking into consideration the
deliberations of CAEP/6 in 2004...." It is vital that EPA take a more aggressive role in setting
standards in time to meet the CAA deadlines for air quality attainment. In addition, they would
like future standards to control aircraft emissions in a manner equal with emission control
strategies from other sources. CAEP/6 standards would be "a step in the right direction, but even
stronger, forward looking, technology-forcing standards are also absolutely necessary,"
otherwise emissions will continue to increase in the future. EPA acknowledged in the proposed
rule that many engines already perform better than the CAEP/4 or proposed standards.
However, the Agency should set future standards "that reflect the emission reductions that
technologies will deliver at the future implementation date."
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Also, state and local governments and environmental groups suggested that ongoing
progress in the development of technology provides a reasonable expectation that significant
emissions reductions from aircraft are attainable in the relatively near term. Currently, the
National Aeronautic and Space Administration's (NASA) Ultra-Efficient Engine Technology
(UEET) program aims to achieve 70 percent reduction (from CAEP/2) in NOX levels within the
next 10 years without adversely affecting noise or fuel burn. This NASA "stretch" goal seems to
be a sensible starting point for a technology-based standard for aircraft. CARB believes future
standards consistent with the NASA 70 percent reduction target are achievable and necessary "to
meet air quality and public health goals," and EPA should immediately begin work with FAA to
set more effective standards for implementation beginning in 2010 (so states can start realizing
benefits in time to comply with air quality attainment deadlines for the 1-hour ozone, 8-hour
ozone, and PM2 5 NAAQS). In addition, state and local governments and environmental groups
expressed that due to the promising technological developments taking place with aircraft
aerodynamic design and materials (lighter and stronger), there is great promise in the future for
more fuel-efficient and lower-emitting aircraft (which could lead to substantial reductions in
emissions). The Agency should consider regulating emissions from the aircraft instead of the
engine in order encourage the continuing development and application of new technology for
airframes. STAPPA/ALAPCO urges EPA to promptly develop future aircraft emission
standards according to a forward-looking approach that will get the most out of such
technological advancement. GA DNR indicated that considering the engine and airframe
technology for future standards will benefit the aircraft industry and the federal, state, and local
officials responsible for managing the nation's air resources.
In addition, for assessments of future standards, STAPPA/ALAPCO urged EPA to
calculate not only the costs, but also the emission benefits, over the full useful life of aircraft
engines. The cost results provided at CAEP/6 were not calculated in such a way.
Delta Air Lines, Inc. expressed that EPA has been premature in bringing up the issue of
further NOX stringency beyond the proposed (or CAEP/4) standards and prior to a complete
assessment by CAEP. It may set expectations on standards or their implementation date that are
not consistent with the conclusions and recommendations of the CAEP/6 meeting. The Agency
should align new standards "with ICAO and refrain from independently pursuing more stringent
regulations that would place U.S.-based airlines at an economic disadvantage in the global
marketplace." Delta suggested that since aircraft emissions account for a small percentage of the
total NOX from mobile sources (only 1 percent), the potential for actual NOX reductions from
aircraft is limited. It is not clear that additional reductions from aircraft would provide a
substantial benefit to assist states with air quality attainment. The need for pursuing additional
decreases in aircraft emissions should be based upon regional ozone modeling protocols, not the
relative contributions.
ACI-NA&AAAE suggested that the U.S. continue to press for further NOX stringency at
CAEP/6 and beyond, accounting for economic considerations consistent with the CAA.
Our Response:
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As stated earlier in section 1.1 of this document (Engine NOX Standard Levels and
Stringency), section 23 l(b) of the CAA allows EPA to establish aircraft emission standards at a
level that is currently not achieved in practice, provided we give sufficient lead time to develop
necessary technology before such standards must be met. However, we are not compelled under
section 231 to obtain the "greatest degree of emission reduction achievable" as per sections 213
and 202 of the CAA. EPA has more flexibility under section 231 in determining what aircraft
emission standard is most sensible. Expectations for the NASA UEET program could be the
basis for future standards similar to a 70 percent NOX reduction (from CAEP/2). A commenter
urged us to set future standards similar to NASA targets for implementation in 2010, but it is
premature to determine whether this is sufficient lead time since we have not undertaken an
assessment of future standards, the technologies that could be used to meet them, or the costs or
safety considerations of this goal. For such future standards, lead time would be a central
consideration. In addition, we would need to appropriately evaluate the costs to meet stringency
levels comparable to NASA targets, including after the NASA research ends and the industry
begins applying the technology to their products. We anticipate setting more stringent NOX
standards in the future, and the Agency would assess the costs (and emission benefits) of any
future standards regardless of stringency level. However, we have yet to conduct such an
assessment of future standards.
In regard to the comment that for analysis of future standards EPA should calculate the
emission benefits over the full useful life of aircraft engines, we would agree. It is normal EPA
practice to do so for our regulatory impact analysis of rulemakings (which are typically
conducted when the regulated entities are not already voluntarily complying with requirements -
as is the case with today's action). But since today's standards will not compel a reduction in
emissions beyond the current baseline, it was not necessary for us to calculate emission benefits
for them.
We agree with the view expressed by commenters that it may make more sense as a
practical matter to regulate emissions from the entire aircraft instead of only the engine.
However, it may take many years to develop new procedures or methods for assessing aircraft
and engine emissions together. Thus, the benefits of any such standards requested by some
commenters would not be realized in the near term. For the sake of meeting the specific
mandate of section 231, we believe it is more appropriate at this time to continue focusing
standards on the aircraft engine. However, we will take the suggestions provided on regulating
the entire aircraft under consideration in the setting of future standards.
We do not agree with the comment that it was premature to discuss further NOX
stringency beyond the proposed standards before a CAEP assessment. We believe a ongoing
phased approach is the most appropriate means to address emissions: codify current practice
(with no significant lead time) as a near-term approach and address more stringent emission
standards requiring more lead time in a future rulemaking. Due to our intention to explore more
stringent standards in the future, it was appropriate to raise this issue for public consideration in
the proposal. In regard to consistency with ICAO standards, see our response on this issue in
section 1.3 of this document (Alignment with ICAO Standards).
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We disagree with the comment questioning whether additional reductions from aircraft
would provide a substantial benefit to help states with attainment. Although aircraft NOX
emissions are a relatively smaller part of the national emissions inventory, they clearly contribute
to the overall quality of air throughout the nation. In addition, as described later in our response
to comments in section 3.2 (Aircraft Emissions Contribution) and in the proposed rulemaking,
growth in commercial aircraft emissions is expected to occur (even with the temporary set back
due to the tragic events of September 11, 2001) when other significant sources are drastically
reducing emissions, thereby accentuating the growth in aircraft emissions. For instance, from a
local/regional perspective the 1999 EPA study (Evaluation of Air Pollutant Emissions from
Subsonic CommercialJet Aircraft) showed that as an average for the for ten cities analyzed,
commercial aircraft's contribution to regional mobile source NOX emissions was anticipated to
increase from about 2 percent in 1990 to 5 percent in 2010.
Aircraft NOX emissions contribute to ground level ozone and secondary particulate matter
(PM2 5). As indicated in our response to comments in section 3.1 of this document (Overall Air
Quality Need), there are approximately 159 million people living in areas that either do not meet
the 8-hour ozone NAAQS or contribute to violations in other counties as noted in EPA's recent
nonattainment designations for part or all of 474 counties. In addition, approximately 88 million
people live in 208 full and partial counties where air quality measurements violate the PM2 5
NAAQS (a map of the current areas violating the ozone and PM25 NAAQS and a list of affected
counties can be found in Docket No. OAR-2002-0030, Document No. OAR-2002-0030-0209).
Aircraft operate nationwide, including in these nonattainment areas.
While we have not modeled the impacts on ozone and PM2 5 levels due to the future
aircraft standards, such future standards would result in NOX emission reductions throughout the
nation. Because NOX is a precursor to ozone and PM2 5, these reductions may be especially
helpful for those areas that are in nonattainment of the ozone and PM2 5 NAAQS. Federal, state
and local governments will need to reduce emissions from many different sources of ozone and
PM2 5 precursors to achieve the reductions needed to meet the NAAQS. Most of these sources
are not by themselves large contributors to the percentages of ozone and PM2 5 precursors in the
air. However, taken together they represent a large source of potential emission reductions that
can reduce the number and severity of ozone exceedances. Neither EPA nor other governments
can effectively and cost-effectively reduce emissions by regulating only a few large sources or
source categories. Getting further emissions from sources that are already well regulated can
often be much less cost-effective than reducing emissions from those sources that have not been
as well regulated in the past.
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1.6 Long-Term Technology Goals
What Commenters Said:
AIA expressed that the long-term technology goal program considered at CAEP/6 offers
a medium to ensure the development of appropriate breakthrough technologies to further
decrease aircraft engine emissions. "Certification standards are not the appropriate means to
achieve these ends. The proposed standard is a certification standard whereby aircraft engines
must be demonstrated as airworthy to enter service in order to remain in service. Design of an
engine must allow for differing thrust requirements and for uncertainty in specification of safety
and environmental regulations. This is by nature a conservative process . Technologies used in
engine design are rarely breakthrough technologies; rather, they are improvements to existing
technologies and/or application of newly developed technologies to the combustor. Certification
standards are appropriate to evolutionary technology developments; long term technology goals
are appropriate to progressing breakthrough technologies. Long term technology goals coupled
with its standards setting prerogative will ensure continued progress toward meeting Clean Air
Act requirements." Also, AIA strongly supports working with CAEP on their future work
program on non-binding long-term technology goals.
ATA suggested that CAEP's goal review process provides the forward-looking viewpoint
that will facilitate the development of technology. At the CAEP/6 meeting in February 2004,
CAEP will consider a new process to setting long-term and medium-term technology goals.
Long-term goals will comprise technology under development by research agencies. Medium
term goals will cover technology at a more advanced stage that is being further developed by
manufacturers. The goal review panel will consist of experts from research establishments and
manufacturers, plus other stakeholders and independent experts. The panel will meet on a
schedule consistent with the CAEP cycle, and it will provide CAEP with a comprehensive
assessment of the goals being pursued by governments and industry globally. In addition, ATA
indicated that the panel will check the progress toward existing goals, and decide whether
technological innovations substantiate raising the goals. This review procedure will facilitate
lower-emission technology development in a way consistent with the safety and airworthiness
requirements. Also, ATA stated that "[w]hen technology progresses to a certification-ready
stage, it can then be considered for future standards."
In addition, ATA expressed that while recognizing the fact that standards and goals must
remain separate, the goal procedure will give CAEP a forward-looking focus on developing
technology. "Though CAEP is not itself a research body, it can facilitate the efforts of
researchers at all stages by bringing a comprehensive approach to technological development
under the aegis of CAEP."
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Our Response:
At CAEP/6, it was agreed that the future CAEP work program would continue efforts on
developing long-term technology goals, including implementing a CAEP-approved process to set
and review these goals.7 We support this future work item and related process for establishing
goals. However, this should not be interpreted as agreement on our part that the CAEP process
is the exclusive appropriate process for setting aircraft emissions reduction goals or for
encouraging the development of better performing technology. (For example, the Next
Generation Air Transportation System (NGATS) plan was released in December 2004 - a
Congressionally chartered and Administration endorsed activity to develop research and plans to
transform the air transportation system. Efforts there will include assessment of various
technological and operational procedures to reduce aircraft emissions, including NOX, as well as
a thorough assessment of interrelationships between noise and emissions and amongst emissions
to enable maximizing environmental benefit derived from mitigating actions). In our long
history of mobile source regulation, we have found that performance-based standards have been
successfully used to stimulate technological development resulting in cleaner, cost-effective, and
safe engines.
In regard to comments on setting aircraft engine standards or the basis for the level of
standards, refer to our response to comments in sections 1.1 and 1.5 of this document (Engine
NOX Standard Levels and Stringency and Future Standards).
7ICAO, CAEP, Sixth Meeting, Montreal, Quebec, February 2-12, 2004, Report, Letter of
Transmittal to the President of the Council From the Chairman of the Sixth Meeting of CAEP,
CAEP/6-WP/57 (Report on Agenda Item 4). Copies of this document can be obtained from
ICAO (www.icao.inty It can also be found in Docket No. OAR-2002-0030.
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2. Applying the NOX Standards to Newly Manufactured Engines of Already Certified
Models (Production Cut-off)
What We Proposed:
The comments in this section correspond to Section IV of the aircraft engine NPRM, and
therefore are targeted at issues of applying the CAEP/4-equivalent NOX standards to newly
manufactured engines of already certified models (i.e., a production cut-off date by which all
new engines produced after that date must meet today's standards, rather than following CAEP/4
and merely applying today's standards to future engine designs and allowing currently produced
engine models to meet the previous standards), which we requested comment on in the NPRM.8'9
A summary of the comments received, as well as our responses to those comments are located
below. For the full text of comments summarized here, please refer to the public record for this
rulemaking.
What Commenters Said:
Bluewater Network expressed that EPA conceded in the proposed rule that it has
historically applied aircraft emission standards to newly manufactured engines of already
certified models and doing so this time would prohibit the indefinite continued production of
aircraft engines that would meet only the previous standards. "EPA does not explain why it is
proposing a sudden departure from the past practice of regulating already certified, newly
manufactured engines - i.e., what is different about this particular rulemaking that justifies the
exemption of such engines." Bluewater Network suggested that without a reasoned explanation,
the Agency's proposal to exempt newly manufactured engines of already certified models from
the new standards would be considered arbitrary and capricious, especially taking into account
the harm of ozone pollution, the nonattainment problem throughout the country, and the aircraft
emissions contribution to lo cal air quality problems. With the long life of aircraft engines and
the availability of newly manufactured engines of already certified models in the future, there is
a need to apply the proposed NOX standards to this category of aircraft engines. In addition, with
respect to an implementation date for such requirements (which we requested comment on in the
8The provision of applying the standards to newly manufactured engines of already
certified models does not mean the re-certification or retrofit of existing in-use engines. Instead
the provision would require the ongoing production of engines that have already been certified to
meet the new standards (i.e., those individual engines that are part of an already certified engine
model, but are built after the effective date of the regulations for such engines and have never
been in service).
9In the proposal, we referred to such engines as already certified, newly manufactured
engines or already certified engines; however, this terminology may need some clarification for
the final rulemaking (thus, we use the term "newly manufactured engines of already certified
models").
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NPRM), Bluewater Network expressed that the Agency should evaluate information on why
such lead time would be needed and choose the shortest lead time. Also, in response to an
NPRM request for comment on an averaging program for newly manufactured engines of
already certified models, Bluewater Network indicated that an averaging program would create
auditing and enforcement challenges that would necessitate considerable resources.
State and local governments recommended that the standards for newly manufactured
engines of already certified models should be implemented one year after the effective date of
the final rulemaking. At a minimum, EPA should have an implementation date that prohibits
engine manufacturers from selling already certified engines unless the engines were recertified
or redesigned to meet the proposed standards. STAPPA/ALAPCO commented that such a
provision would be consistent with a stated objective of the rulemaking, which is to assure that
progress in reducing aircraft engine emissions is not reversed in the future. Without such
standards, high-emitting engines can continue to be produced and brought into service, further
adding to the long-term growth in aircraft emissions that is anticipated without a more aggressive
approach to regulating this source.
Also, STAPPA/ALAPCO commented that as EPA indicated in the NPRM, except for
aircraft engines, all current CAA mobile source programs involving new emission standards
apply to newly manufactured engines or vehicles based on the certification model year.
STAPPA/ALAPCO questioned why the Agency did not pursue the same approach in the NPRM.
In addition, ED suggested that whether or not the proposed NOX standards should be
applied to newly manufactured engines of already certified models is almost moot because the
standards have no real effect. If the Agency issued a technology-forcing standard that ultimately
reduced emissions, then it may make sense to provide some period of time (2-4 years) prior to
applying the standard to such engines.
ATA commented that as the NPRM acknowledges, market incentives lead manufacturers
to bring their engines to the levels of the CAEP/4 NOX standards as soon as possible once the
standards take effect. Air carriers investing in costly, long-lasting assets prefer to buy engines
that meet the latest standards, and demand engines that perform better than the standard without
regulatory intervention of a production cut-off (applying standards to newly manufactured
engines of already certified models). Such market forces together with EPA's four-year delay in
proposing to adopt the CAEP/4 NOX standards, account for the fact that 94 percent of in-
production engines already meet the standard.
Also, ATA indicated that at CAEP/6 in February 2004 a decision will be made on
whether to apply the CAEP/4 standards to newly manufactured engines of already certified
models. CAEP's Forecasting and Economic Analysis Support Group (FESG) has assessed the
costs and benefits of such a provision. If CAEP adopts a this provision, it will also recommend
an implementation date.
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In addition, ATA and Delta Air Lines, Inc. expressed that for the same reasons that the
Agency should generally align with ICAO standards, it should be consistent with ICAO on
whether to apply CAEP/4 standards to newly manufactured engines of already certified models.
If EPA differed from ICAO on this provision, there would be the very inconsistency between
domestic and international practice that aligning with ICAO requirements avoids. Furthermore,
if EPA adopts such a provision prior to ICAO, such action would potentially place U.S.
manufacturers and air carriers at a competitive disadvantage for what EPA acknowledges to be
minimal environmental benefit.
Delta Air Lines, Inc. commented that application of the new standards to newly
manufactured engines of already certified models is unwarranted. According to the Clean Air
Act, EPA must give "appropriate consideration" to the cost of compliance for new aircraft
emission standards. Any further stringency (such as these provisions for newly manufactured
engines of already certified models), beyond those set by ICAO will result in additional cost to
Delta and other domestic air carriers. The cost EPA describes in the NPRM has not undergone
an appropriate cost benefit assessment to find out the true effect on U.S. air carriers of applying
the proposed standards to newly manufactured engines of already certified models. According to
the commenter both the minimal environmental benefit acknowledged by EPA (with which Delta
is in agreement) and the potential for competitive disadvantage for domestic carriers argue for
the Agency to conduct such an analysis before further consideration of this issue.
In addition, of the four engine models that would be effected by applying the standards to
newly manufactured engines of already certified models, Delta Air Lines, Inc. presently has the
JT8D-219 engine on some of its commercial jets. Delta expressed that the NPRM indicated that
the JT8D-219 would be used in supersonic business jets, which they do not operate; however,
Delta (and maybe other domestic air carriers) operates this engine in its commercial aircraft
fleet. Therefore, the implication of these provisions has not been fully investigated by EPA as
mandated by the CAA.
Also, Delta Air Lines, Inc. stated that full consideration must be given to the overall
environmental benefit of such a provision. Changes to engine design parameters to decrease
emissions of one pollutant not only affects engine performance, but it can and does increase
emissions of other pollutants and/or noise. The interrelationships between aircraft engine
performance, emissions of different pollutants, and noise are complex and bring about the need
to consider trade-offs related to changing engine design. "These interrelationships must be fully
evaluated and understood, and balanced against one another to effectively address all issues
associated with aircraft engine operations."
AReCO suggested that today's standards should also be applied retroactively to all
existing fleet aircraft (an existing in-use engine standard), with a phase-in period of linearly
increasing stringency for the next 20 years. ATA stated that they strongly oppose any measure
that retroactively applies to the existing fleet.
Our Response:
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It is important to mention that, as indicated in the preamble of the final rulemaking,
CAEP/6 did not adopt provisions to apply the CAEP/4 NOX standards to newly manufactured
engines of already certified models. CAEP/6 noted the industry view that market forces are the
primary drivers of the development and incorporation of new technology (asserting voluntary
compliance would suffice), and an understanding at CAEP/4 that a production cut-off would not
be introduced in the future. CAEP/6, after reviewing that commitment, decided that "...this
should not be interpreted as meaning that production cut-offs would not be introduced in the
future if the situation so warranted."10'11
As an update to the status of engines discussed in the proposed rulemaking, nearly all
engines that did not meet the CAEP/4 NOX standard in 1998 now comply, except for the JT8D-
200 engine family.12 The PW4090 family of engines, which was described as not meeting the
proposed standards in the NPRM, now has the means to eventually meet the standards (utilizing
technology that would meet the lower ranges of stringency options for the NOX standards
considered at CAEP/6), although the manufacturer has projected it would be some years before it
expects to meet CAEP/6 levels (the manufacturer has not provided us with a projected necessary
lead-time to meet CAEP/4).
The JT8D-200 engine powers the MD-80 aircraft, which is no longer in production. Yet,
the JT8D-200 engine (JT8D-217C and JT8D-219 in-production engines) could potentially apply
to future supersonic business jets. As stated in the NPRM, the resulting NOX emission benefits
of applying the standards to the JT8D-200 (for these possible supersonic business jets) would be
expected to be very small, and the costs would also likely be relatively small on an industry wide
basis, although as discussed further below we do not feel we have a sufficient record at this point
- nor have we presented it for public comment - to state our definitive views on these issues.
10ICAO, CAEP, Sixth Meeting, Montreal, Quebec, February 2-12, 2004, Report, Letter of
Transmittal to the President of the Council From the Chairman of the Sixth Meeting of CAEP,
CAEP/6-WP/57 (Report on Agenda Item 1). Copies of this document can be obtained from
ICAO (www.icao.inty It can also be found in Docket No. OAR-2002-0030.
nCAEP/6 noted that industry "pointed out that introduction of a production cut-off now
would cause the manufacturer to modify engines to meet the CAEP/4 standards, whereas if no
cut-off were imposed it was likely that they could be modified to meet the new standards agreed
at this meeting." (ICAO, CAEP, Sixth Meeting, Montreal, Quebec, February 2-12, 2004,
Report, Letter of Transmittal to the President of the Council From the Chairman of the Sixth
Meeting of CAEP, CAEP/6-WP/57, Report on Agenda Item 1, page 1-13.)
12ICAO, CAEP/6, Working Paper 34, "NOX Production Cut-off Consideration," Presented
by the International Coordinating Council of Aerospace Industries Associations (ICCAIA),
January 6, 2004. A copy of this document can be found in Docket No. OAR-2002-0030.
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However, the direct (development) costs would most likely be borne by one engine
manufacturer.13
As indicated earlier, the implementation date applicable to newly designed and certified
engines under CAEP/4, December 31, 2003, has already occurred for the CAEP/4 standards, and
at this late date to promulgate a provision to apply today's standards to newly manufactured
engines of already certified models (a production cut-off) could be disruptive to the production
planning of engine manufacturers. EPA and ICAO (as we mentioned in the proposal and as one
commenter noted in its comments) have historically adopted production cut-offs for previous
standards, but in today's unique case the lateness of the rule may not provide manufacturers
enough lead time for such planning. However, as we discussed earlier in section 1, we intend to
consider more stringent NOX standards in a future rulemaking, and similar to CAEP/6's future
plans described above, we also intend to consider applying more stringent standards to newly
manufactured engines of already certified models for such a future rulemaking. This provision is
an important issue that we expect to fully consider for future standards.
While we solicited comment on extending the CAEP/4 standards to newly manufactured
engines of already certified models, we did not develop a record that fully analyzes the emissions
benefits (if any) and the implementation costs of going beyond CAEP in this manner. Therefore,
the public has not been provided an opportunity to analyze and comment upon these important
factors. We believe that our analysis of these factors would need to be weighed through a
notice-and-comment process in determining whether a production cut-off, with a specific lead-
time period, would be appropriate under CAA section 231 in this case. Particularly regarding
the cost of compliance within necessary lead-time issue, we are concerned that there is
insufficient data that specifically addresses the appropriate lead time for subjecting the few
remaining in-production engine models to the CAEP/4 standards, and that our selection of a
production cut-off date could therefore be viewed as arbitrarily chosen.
Since we have not yet provided that opportunity for public comment on our analysis of
this issue, and since attempting to do so now would in our view unacceptably slow down this
rulemaking, in the interests of expediency and of bringing U.S. domestic law into conformity
with our obligations under the Chicago Convention (albeit tardily), we have decided that the
most appropriate course for now, under CAA section 231 (a), is to simply update our regulations
to track CAEP/4 in terms of both stringency levels and scope of applicability. Similarly, without
having developed the necessary record and analysis, at this time we are unable to respond to the
substantive comments offered by commenters regarding the production-cutoff issue, and our
decision today should in no way be viewed as either endorsing or rejecting the concept of a
13ICAO, CAEP/6, Information Paper 28 - Appendix B, "FESG Economic Assessment of
Applying a Production Cut-off to the CAEP/4 NOX Standard" Presented by the FESG
Rapporteur, January 29, 2004 (Same as CAEP-SG20031-IP/9, which was presented at June 10,
2003 CAEP Steering Group Meeting). A copy of this document can be found in Docket No.
OAR-2002-0030.
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production cut-off. Given the need to quickly promulgate standards that are at least as stringent
as CAEP/4, we must decline to resolve the numerous issues raised either in favor of or in
opposition to applying the CAEP/4 standards to newly manufactured engines of already certified
models.
In response to the comment that an emission averaging program would generate
enforcement (and/or administrative) challenges that would necessitate substantial resources, we
would agree that such a program would require more than a trivial amount of resources to
implement; however, we would not anticipate the need for any more resources than is currently
provided for other CAA mobile source programs. Such an averaging program would be
enforced by FAA, who is responsible for the enforcement of aircraft emission standards
according to section 232 of the Act, and we believe that we could work with FAA to set up a
program that would be supported with a reasonable amount of resources. On the other hand,
because we did not receive any comments supporting an averaging program and nearly all in-
production engines meet the standards, we have decided to not move forward with such a
provision in today's rulemaking. It may be more productive to revisit the concept of an
averaging program in a future rulemaking for tighter standards, where there would likely be a
better opportunity to flesh out the details of such a program and submit them for public
comment.
As for the comment on applying today's standards retroactively to existing fleet aircraft
(or existing in-use engine standards), such requirements are not within the scope of this
rulemaking. In the NPRM, we requested comment on applying the NOX standards to newly
manufactured engines of already certified models (or newly manufactured engines within
existing engine models), but not to existing fleet or in-use aircraft engines. Moreover, we did
not ask for comment on the retroactive application of such a standard, and therefore do not
believe we could take final action to retroactively impose such standards in this rulemaking. As
is the case with applying a production cut-off, we believe we would need to develop a record and
analysis for this issue and submit that for public comment before we consider adopting such an
approach. The need for us to adopt today's standards quickly precludes our ability to further
consider that issue in this rulemaking.
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3. Environmental Need for Control
What We Proposed:
The comments in this section correspond to Section III of the aircraft engine NPRM, and
therefore are targeted at environmental need issues for the proposal. A summary of the
comments received, as well as our responses to those comments are located below. For the full
text of comments summarized here, please refer to the public record for this rulemaking.
3.1 Overall Air Quality Need
What Commenters Said:
Bluewater Network expressed that many urban areas are currently not in attainment with
the 1-hour ozone standard and won't be with the upcoming 8-hour ozone standard. Bluewater
Network stated that according to data from 1999 to 2001, "EPA expects 111 million people will
live in nonattainment areas where they will be forced to breathe unhealthful air." Based on non-
EPA data, 2002 was the worst smog year in history, with 41 states and the District of Columbia
exceeding the 8-hour ozone standards nearly 9,000 times, a 90% increase over 2001 data.14 Also
in 2002, twenty-nine states and the District of Columbia did not meet the one-hour ozone
standard over 800 times. For these nonattainment regions, aircraft emissions are a problem, and
to highlight this concern these regions are currently indicating that reductions from stationary
sources are more and more difficult to find.
In addition, the Center for Clean Air Policy (CCAP) expressed that an EPA analysis
shows the a wide number of areas are expected to be designated as nonattainment for the 8-hour
ozone and PM2 5 standards. Specifically, EPA currently estimates that 290 counties throughout
the nation are projected to be in nonattainment with the 8-hour ozone standard and 129 counties
for PM2 5. (ED suggested that nationwide monitoring indicates that 175 million people in 628
counties are exposed to ozone levels that exceed the NAAQS.) CCAP commented that since
most of these counties include major urban areas, there will be some form of air travel in these
nonattainment areas. However, these proposed standards "will not provide significant benefits to
the environment, human-health, and communities working to come into attainment for the 8-
hour ozone and fine particulate standards." Also, CARB expressed that over 100 million
residents of the U.S. live in areas with unhealthy ozone or PM25 levels, and Californians
experience the highest levels in the nation. Moreover, SCAQMD recently adopted 2003 Air
Quality Management Plan to comply with 1-hour ozone and PM10 NAAQS, and significant
reductions in emissions are required to meet these standards by 2010. GA DNR suggested that
reductions of ozone and PM25 and their precursors necessitates control of emissions from every
sector, in addition to reductions already applied to attain the 1-hour ozone standards.
14U.S. PIRG Education Fund, "Danger in the Air: Unhealthy Levels of Smog in 2002,"
Augusts, 2003.
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STAPPA/ALAPCO suggested that "NOX is a major contributor to multiple environmental
problems including ozone, fine particles, acid rain, regional haze, and the nitrification of water
bodies. ED indicated that elevated ozone concentrations have a number of adverse health effects
including reduced lung function (especially in children active outdoors), hospital admissions and
emergency room visits for respiratory causes (among children and adults with pre-existing
respiratory disease such as asthma), inflammation of the lungs, and possible long-term lung
damage. Considerable additional reductions in NOX emissions are needed to effectively address
these problems and balance the anticipated growth in activity from sources that account for most
NOX emissions. STAPPA/ALAPCO expressed that nationwide NOX emissions from all sources
increased by 2 percent between 1989 and 1998. To tackle this problem, STAPPA/ALAPCO and
GA DNR commented that the U.S. will apply stringent new standard for some of the most
significant sources of NOX. For instance, with Tier 2 motor vehicle standards, light-duty vehicle
NOX emissions will be 99 percent less than NOX from the uncontrolled vehicle of the 1960s. In
addition, the standards for heavy-duty highway vehicles that will be implemented in 2007
require a 90 percent reduction in NOX emissions from today's levels, and the recent regulations
for heavy-duty nonroad diesel engines will also decrease NOX by 90 percent from today's levels
by 2011 (similar controls already or will apply to power plants as well). Moreover, due to
federal transportation conformity, major cities' ground transportation programs will encounter
considerable pressure to reduce NOX.
In addition, one commenter indicated that "as a breather of common air (as we all are), I
believe it is in everyone's best interests to reduce the pollution from aircraft and their engines as
much as possible."
Our Response:
Nationwide, there are approximately 159 million people living in 126 areas that are
designated as not attaining the 8-hour ozone NAAQS based upon the monitored data from 2001-
2003 and other factors.15 All or part of 474 counties are designated as non-attainment for the 8-
hour ozone NAAQS. In addition, approximately 88 million people live in 39 areas and 208 full
and partial counties that are designated as not attaining the PM2 5 NAAQS (a map of the current
areas violating the ozone and PM25 NAAQS and a list of affected counties can be found in
Docket No. OAR-2002-0030, Document No. OAR-2002-0030-0209). These numbers do not
include the tens of millions of people living in areas where there is a significant future risk of
failing to maintain or achieve the ozone or PM2 5 NAAQS. Federal, state, and local governments
are working to bring ozone and PM levels into compliance with the NAAQS.
15U.S. EPA, "Air Quality Designations and Classifications for the 8-hour Ozone National
Ambient Air Quality Standards; Early Action Compact Areas With Deferred Effective Dates,"
Final Rule, 69 FR 23858 (April 30, 2004). On June 15, 2004, the 8-hour ozone nonattainment
designations became effective.
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From air quality modeling performed for the recent Clean Air Interstate Rule (CAIR),16
we anticipate that without emission reductions beyond those already required under promulgated
regulation and approved State Implementation Plans (SIPs), ozone nonattainment will likely
persist into the future. With reductions from programs already in place, including the CAIR, the
number of counties in the eastern U.S. violating the ozone 8-hour standard is expected to
decrease in 2015 to 16 counties where 12 million people are projected to live. Furthermore, for
PM2 5, air quality modeling performed recently in connection with our CAIR rule, suggests that
elevated PM2 5 levels are likely to continue to exist in the future in many areas in the absence of
additional emission controls.17 For example in the eastern U.S. in 2015, based on emission
controls currently adopted, we project that 16 million people will live in 18 counties with
average PM25 levels above 15 ug/m3. See Section II of the preamble of today's final rulemaking
for further discussion on air quality need.
As discussed above in our response, we have updated information on the number of
people and counties exceeding the 8-hour ozone and PM2 5 NAAQS, and we would agree that
many urban areas are currently not in attainment with the ozone and PM2 5 standards. In
addition, we agree that NOX is a significant contributor to a number of environmental problems
including ozone, fine particles, and visibility. We also would agree that NOX reductions in
addition to those expected from recent new standards issued by EPA for other sources are
needed to address these problems. Moreover, we realize that reductions from other significant
mobile and stationary sources are becoming tougher to find since they are (or have) already
greatly reducing their emissions. We understand that many areas will have a difficult time
meeting the NAAQS without decreasing aircraft emissions, which continue to grow. In addition,
we acknowledged in the NPRM that the proposed standards would have minimal air quality
benefit. Therefore, as stated earlier we have promulgated the proposed standards, and we
anticipate establishing more stringent NOX standards in the future. We consider this ongoing
phased approach to be the most appropriate way to address aircraft engine emissions.
3.2 Aircraft Emissions Contribution
What Commenters Said:
STAPPA/ALAPCO and GA DNR expressed that in contrast to other sources aircraft NOX
is projected to rise at a rapid rate. STAPPA/ALAPCO also stated that "[f]or most states and
localities with major airports and seaports, aircraft and international marine vessels are the only
16U.S. EPA, "Rule To Reduce Interstate Transport of Fine Particulate Matter and Ozone
(Clean Air Interstate Rule); Revisions to Acid Rain Program; Revisions to the NOX SIP Call,"
Final Rule, 70 FR 25162, May 12, 2005.
17U.S. EPA, "Rule To Reduce Interstate Transport of Fine Particulate Matter and Ozone
(Clean Air Interstate Rule); Revisions to Acid Rain Program; Revisions to the NOX SIP Call,"
Final Rule, 70 FR 25162, May 12, 2005.
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two source sectors where emissions are projected to increase in the future." Moreover,
STAPPA/ALAPCO and GA DNR commented that based on recent FAA growth projections,
aircraft emissions are estimated to double by 2030, despite the effects of the tragic events of
September 11, 2001. Georgia DNR indicated that NOX emissions from Harstfield-Jackson
Atlanta International Airport increased substantially in the 1990's, and from 1990 to 2002 NOX
emissions grew from 1 to 3.2 percent of all NOX emissions in the Atlanta nonattainment area.
Airport-related NOX at this airport is projected to grow by 26 to 42 percent by 2010, and
emissions growth is expected well in the future due to increases in operations (activity increase
projected by FAA-approved airport layout plan). In addition, NY suggested that aircraft NOX are
projected to grow rapidly in the future, and even with effects of 9/11, aircraft emissions are
expected to grow by 100 percent in the next 30 years. Bluewater Network also commented that
aircraft operations are projected to grow even despite the temporary setback in aircraft activity
after the tragic events of September 11, 2001. At airports in ten major cities, NOX emissions will
likely grow by about 15,000 tons per year from 1990 levels. GA DNR commented that for states
and local air agencies to meet the NAAQS, they will have to control major sources further in
order to offset the increase in aircraft emissions - if the aviation sector is not required to flatten
the growth curve and start to return emissions to some baseline, e.g. 1990 emission levels.
CARB commented that they can not meet their goals for health protection without tackling the
continued growth in aircraft emissions.
CCAP stated that aircraft NOX is projected to grow with the proposed standard. The NOX
stringency analysis conducted by the Environmental Consulting Group, LLC for EPA in 2003
demonstrates the directional emissions effect of the proposed standards. Based on this
assessment, in 2015 aircraft NOX throughout the nation are estimated to be 46 percent above
2000 NOX levels. This time frame corresponds with the time period that many communities will
need to decrease NOX to meet the 8-hour ozone standard. In addition, over a longer time frame
(2000 to 2040) aircraft NOX is estimated to increase by an even greater amount (159 percent)
with the proposed rule.
SCAQMD expressed that aircraft remain a significant and growing emissions source in
the South Coast Air Basin (Basin) since passenger and cargo carrier activity are projected to
double by 2030 (compared to 2002 levels). Standards for aircraft emissions have not been
adequately developed to tackle the increasing effect of these emissions on air quality. Even
though EPA acknowledges aircraft's environmental effects, the proposed rule does nothing to
address these effects. Also, SCAQMD commented that the Basin has a tough challenge to
achieve attainment of the 1-hour ozone standard by 2010, and to meet its goal, emissions from
all sources including those under federal jurisdiction such as aircraft will be necessary. Thus,
SCAQMD strongly believes that EPA should make every effort to do its fair share in obtaining
all feasible aircraft reductions, thereby assisting their region in complying with the federal
NAAQS. Without sufficient control on emission sources such as aircraft, the burden for
reductions would shift unfairly towards other mobile and stationary sources, which have been
heavily regulated for many years.
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In addition, CCAP indicated that the 2003 Northeast States for Coordinated Air Use
Management (NESCAUM) and CCAP study at three airports in the Northeast shows that airport
emission sources such as aircraft, ground service equipment (e.g., baggage tugs), and auxiliary
power units are significant sources of emissions in comparison to other emission sources in their
respective regions. The assessment also showed that aircraft contribute about 85 percent of
emissions from these airport sources. While aircraft may contribute a little different fraction of
emissions at each airport, it is correct to expect that aircraft are one of the (if not) most dominant
sources of on-airport emissions at airports nationwide. In addition, the study showed that future
aircraft emissions at the airports evaluated could become as large as major stationary sources in
the region. ED expressed that this assessment indicated inventories for aircraft emissions were
seriously under reported (typically 50 percent lower) in State Implementation Plans (SIPs), and
this further emphasizes the necessity from effective federal measures for aircraft emissions.
Even with this under reporting, there are numerous airports in areas with ozone problems. In
2001, nationwide there were 132 airports in one-hour ozone nonattainment and maintenance
areas, and 22 of the largest 31 airports in the nation are located in ozone nonattainment areas.
Also, in accordance with the air quality monitoring data for 1997 - 1999, there were 137 airports
in potential 8-hour ozone nonattainment areas, and there will probably be several more areas
added to the list in more recent years.
In addition, STAPPA/ALAPCO suggested that at this time, NOX emitted from major
airports is greater than NOX from large stationary sources such as refineries and electrical
generating facilities. NY has a growing concern with the substantial number of unregulated
emissions from aviation activity. Also, ED expressed that airports are a significant source of
ozone-forming pollution in many ozone nonattainment areas. ED suggested that "[s]tate and
local governments need rigorous federal clean air measures to lower smog-forming pollutants
and to restore healthy air quality to vast areas of the country." AReCO indicated that Chicago's
O'Hare Airport (with all its related aircraft operations) is not only one of the worst polluters in
the state of Illinois, but it may be the worst polluter in the nation. Based on their data, AReCO
claims that the emissions of criteria pollutants at O'Hare Airport are "off the charts." A new
O'Hare/Peotone study shows that the health of 8.3 million people is affected by O'Hare
operations (5.5 million people are affected significantly).
ACI-NA&AAAE commented that their "members who operate and manage the nation's
airports are greatly concerned with the quantity of criteria pollutants emitted from airport
sources." The ability of their members to develop critically needed airport facilities that will
provide the capacity for the air transport industry to grow and attain future air travel demand is
seriously and negatively affected by rising public concerns over pollutants impacting air quality
in the vicinity of airports. For these reasons, our members have voluntarily undertaken
considerable steps to decrease emissions from sources under their control at U.S. airports. In
addition, ACI-NA&AAAE expressed that activities at U.S. airports are expected to increase well
into the future, "potentially doubling over the next 20 years." This rise in air traffic will be in
direct response to the U.S. economic growth. The proposed NOX standards are needed to ensure
that air travel does not negatively impact local air quality, while also allowing for the economic
viability of the aviation industry.
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ATA expressed that aviation has always contributed a small fraction of national NOX
emissions even before September 11. The Bureau of Transportation and Statistics data indicates
that in 2001 aircraft contributed only 0.75 percent of NOX from transportation sources, in
comparison to 77 percent for highway vehicles and 11.5 percent for railroads.
In addition, Delta Air Lines, Inc. suggested that for the most adversely affected cities
evaluated by EPA (1999 EPA study, Evaluation of Air Pollutant Emissions from Subsonic
CommercialJet Aircraft), the Agency indicated that by 2010 aircraft NOX are projected to
contribute up to 10 percent of the NOX from mobile sources. What is not clearly conveyed with
this result is that part of the relative increase is because of the actual reduction of emissions from
other more substantial mobile sources. The EPA estimates were published in 1999 and do not
consider the downturn in air transportation from a variety of long- and short-term effects of such
events as September 11, SARS, and the Iraq War. Also, these estimates do not seem to account
for emission reductions due to operations resulting from aircraft fleet renewal and airport
expansion and renewal.
Our Response:
We agree with the comments on aircraft emissions growth. As we stated in the proposed
rulemaking and the preamble of the final rule, commercial aircraft emissions are projected to be
a growing segment of the transportation sector's emission inventory (in spite of the temporary set
back due to the tragic events of September 11, 2001). This growth in commercial aircraft
emissions is expected to occur at a time when other significant mobile and stationary sources are
drastically reducing emissions, thereby accentuating the growth in aircraft emissions.
Furthermore, we would agree that aircraft NOX will continue to grow even with today's standard
or the recently adopted CAEP/6 standard. In addition, airports are an important source of
emissions in nonattainment areas, and aircraft are one of the main sources of emissions at
airports. In addition, we would agree with the comment that states and localities may have to
control other sources further if aviation emissions do not stop growing. Therefore, we are in
agreement with the comments that there needs to be effective controls for aircraft emissions.
As we have already stated, we anticipate establishing more stringent NOX standards in the
future. We believe this ongoing phased approach is the proper way to address aircraft engine
emissions. As we also discussed earlier, the CAEP/6 standards will be a central consideration in
future EPA regulations for aircraft engine emissions. We realize that if we adopted standards in
the future which were equivalent to the CAEP/6 standard, aircraft NOX would continue to grow.
Therefore, such information will be evaluated as we consider the stringency level of future
standards.
In regard to the comments from ATA on the fraction of national NOX emissions from
aircraft, we do not disagree with the national numbers they report. However, from a
local/regional perspective, as described in the proposed rule, the 1999 EPA study (Evaluation of
Air Pollutant Emissions from Subsonic CommercialJet Aircraft) showed that in 2010
commercial aircraft are projected to contribute as much as 10 percent of total regional mobile
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source NOX emissions in at least two of the cities studied. Thus, aircraft are an important and
growing source of emissions regionally and locally, especially for nonattainment areas.
As for Delta Air Lines, Inc. comments that the 1999 EPA study does not make clear that
part of the relative increase is due to the actual reduction of emissions from other more
substantial mobile sources, we would disagree. Specifically, on page 4-1 of this study we state
that "[w]hile emissions from most transportation sources such as NOX from automobiles are
predicted to stabilize and, in many cases, decrease from 1990 through 2010, ground level
emissions from commercial jet aircraft are expected to continue rising." We also elaborate
further on this point in other parts of the study. In addition, as described earlier, we stated in the
NPRM that "[t]his growth in commercial aircraft emissions is expected to occur at a time when
other significant mobile and stationary sources are drastically reducing emissions, thereby
accentuating the growth in aircraft emissions" (see discussion in the NPRM preceding the
mention of the 1999 EPA study). Also, this study accounted for aircraft fleet turnover (activity
of removed or retired aircraft was assigned the emissions of an "average future" aircraft), and it
actually acknowledged the comments from industry on this approach. Yet, we would agree with
Delta that the 1999 EPA estimates did not consider the effects of events such as September 11,
SARS, and the Iraq War. However, as discussed in the NPRM and the preamble of the final
rule, FAA expects the demand for air travel to recover, and then continue a long-term trend of
annual growth in the nation (though from a lower base and a slower rate in the United States).
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4. Approaches to Additional Aviation Emission Reductions
What We Proposed:
The comments in this section correspond to Section VI of the aircraft engine NPRM, and
therefore are targeted at possible other approaches for future aviation emission reductions, which
we requested comment on in the NPRM. A summary of the comments received, as well as our
responses to those comments are located below. For the full text of comments summarized here,
please refer to the public record for this rulemaking.
What Commenters Said:
The CCAP expressed that the combination of current and projected future emission
levels, the need for emission reductions by 2010-2015 for most communities to meet the 8-hour
ozone and PM2 5 NAAQS, and the new NOX standards proposed by ICAO (NOX emissions
growth is estimated to decline slightly due to new ICAO standards), emphasize the need for a
new approach to addressing aircraft emissions. The 2003 NESCAUM and CCAP study assessed
a number of market-based approaches, such as emissions "bubbles" and emissions-based landing
fees, that could be useful models for alternative approaches for the aviation sector.18 CCAP
suggested that "[i]n addition to an airport-by-airport approach (e.g., an airport bubble), EPA may
want to consider a national emissions trading program for aircraft." An absolute emissions (e.g.,
the Acid Rain Trading Program) or rate-based (e.g., NOX emissions per landing and take-off)
reduction could be the basis for either of the above approaches.
Also, ED recommended that the Agency quickly develop national policy guidelines to
help states establish enforceable, declining NOX pollution caps for airports in ozone
nonattainment areas, as well as information about appropriate SIP credit. Approaches such as
"cap-and-trade" or airport bubbles have the potential to limit airport-related emissions, give
flexibility in achieving reductions, and encourage the utilization and development of cleaner
technologies. "Boston's Logan Airport has a cap on airport emissions where any emissions
increases that result from airport activity must be offset by on-airport emission reductions,
reductions near the airport, or by purchasing emission credits." ED suggests that "airport
emissions caps can encourage the introduction of control technologies such as gate
electrification, less polluting aircraft engines, and alternative fuel ground service equipment and
ground access vehicles."
In addition, SCAQMD suggested that in lieu of more stringent national emission
standards for aircraft, and due to the fact that by 2010 such standards would have limited
emission benefit, the Agency should assess and create other innovative aircraft programs.
Particularly, EPA should think about the development of a mitigation fee program for aircraft to
18NESCAUM and CCAP, "Controlling Airport-Related Air Pollution," 2003, available at
www.nescaum.org/workgroups/aircraftport.html.
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attain equivalent reductions in emissions from other sources (e.g., nonroad equipment or on-
highway vehicles), similar to the Mitigation Fee Program for Federal Sources control measure in
SCAQMD's 2003 Air Quality Management Plan. "Under such a program, EPA would charge
fees on aircraft or designate grant funds based on the emission contribution from aircraft (i.e.,
aircraft/engine type, number of operations, etc.)." Furthermore, SCAQMD expressed that the
funding collected from this program would then be transferred to the localities affected
considerably by aircraft emissions for putting into practice emission reduction projects that
would attain equivalent or greater reductions. As an alternative, EPA could create an incentive-
based program that facilitates and promotes the use of less polluting aircraft in the South Coast
Air Basin. These kinds of approaches would make sure that federal sources such as aircraft
would do their fair share toward helping attain the NAAQS.
AReCO also expressed that in the next action, EPA, FAA, and Congress should set
airport based landing fees proportional to the quantity of pollutants emitted by aircraft at an
airport. These fees should be of an amount guaranteed to prompt both air carriers and airports to
decrease emissions. Such incentive fees should be put in a trust fund strictly for environmental
improvements, which would be administered by EPA with oversight by an independent fund
dispersal board (that includes considerable representation from environmental interests). In
addition, ED indicated that airports with emission-based fee programs assess a greater charge to
higher polluting aircraft, and such programs have been implemented at Switzerland's Zurich and
Geneva Airports, and at nineteen airports in Sweden.
Also, ED commented that cost-effective measures exist for decreasing aircraft emissions,
and such measures should be required by this rulemaking. "Near-term emission reduction
options for aircraft include improving airlines' overall operational efficiency, reducing taxi time,
and reducing power output during taxi, takeoff and landing." Optimizing the number of
passengers per flight and maximizing the airlines' use of the cleanest aircraft are cost-effective
methods for improving aircraft efficiency. Decreases in taxi time can be achieved through
"dispatch towing," permitting aircraft to stay closer to runways between landing and takeoff,
decreasing congestion on the ground and in the air by a variety of methods and technology
improvements. The minimization of engine use can be accomplished by approaches such as
engine taxi, decreased utilization of reverse thrust, and utilizing less that full power at takeoff.
In addition, ED indicated that "Heathrow Airport in the United Kingdom encourages
pilots to shut down one or more engines during taxi." This practice is left to the pilots'
discretion since shutting down some engines can reduce aircraft control and might not be
feasible in particular situations or with particular aircraft. Also, National Airspace System
improvements are being considered for the aircraft efficiency benefits. ED expressed that all of
the above approaches cost little or nothing to implement and provide reductions in emissions and
savings in fuel use. Moreover, ED commented that the 2003 NESCAUM and CCAP study
found that the following practices decreased fuel costs and thus reduced emissions of NOX,
hydrocarbons (HC), and carbon monoxide (CO) to various degrees: dispatch towing,
decentralized gates, measures to decrease ground congestion, reduced engine taxi, derated
takeoff, and reduced reverse thrust. Also, ED suggested that the technology improvements that
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decrease aircraft taxi and idling times by making the aircraft movement at the airport more
efficient should be pursued further. "For example, advanced surface movement guidance, very
high frequency (VHP) datalink, arrival and departure management systems, and automatic
dependent surveillance broadcast systems are viable options for reducing emissions."
In addition, ED indicated that long-term aircraft improvements that will considerably
decrease emissions include a blended-wing body configuration (which NASA is presently
working on) that would decrease emissions and improve fuel efficiency (because of its more
aerodynamic design compared to today's aircraft) and the utilization of liquid hydrogen as a
replacement fuel.
SCAQMD expressed that the 2003 Proposed State and Federal Strategy for the California
SIP calls for EPA to assess approaches for decreasing aircraft emissions, including engine
retrofit kits and reformulation of jet fuel. Because of the slow turnover rate of aircraft engines,
the Agency should assess the potential for existing engine retrofits and repowers of aircraft in
use so that emissions from existing fleet aircraft could be decreased without compromising
safety. Also, SCAQMD suggested that repowering could be applied to particular aircraft types
which accommodate the utilization of several different types of engines where a lower polluting
engine could replace an existing, more polluting engine. Fuel reformulations for aircraft might
also be a subject that EPA should assess for feasible emission reductions. In addition, AReCO
suggested that there are other solutions to addressing airport environmental issues such as
creating new fuel sources, constructing new, environmentally friendly airport designs, etc.
ACI-NA&AAAE indicated that they are committed to working with EPA and other
parties on creating and putting into practice balanced emissions reduction programs, for aircraft
sources as well as other emission sources that their airport operators can control.
Delta Air Lines, Inc. commented that they agree "with EPA's recognition that aircraft
engine emissions are but one part of the overall emissions associated with commercial aerospace
operations." Also, Delta expressed that they appreciate the Agency's efforts to work with
stakeholders to create a voluntary program to reduce emissions from other aerospace operations.
They believe "that voluntarily addressing emissions from other aircraft-related operations will
provide more near term environmental benefits than further regulating aircraft engine emissions.
Additional reduction of aircraft emissions is a long-term approach that must incorporate
additional study to fully understand emission interrelationships and economic impacts."
Our Response:
As described in the preamble of the NPRM and final rule, FAA and EPA participated in a
national stakeholder initiative led by states and industry whose goal was to develop a voluntary
program to reduce pollutants from aircraft and other aviation sources that contribute to local and
regional air pollution in the United States. Initially, the discussions with stakeholders focused on
the prospect of aircraft engine emission reduction retrofit kits, which might be applied to certain
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existing aircraft engines.19 However, as the initiative evolved, the focus was expanded by the
stakeholders to identify strategies for various types of ground service equipment (GSE) in use at
airports,20 in addition to strategies to reduce aircraft emissions.21 (At the same time, FAA
developed a program, with Congressional approval, to fund conversion of airport infrastructure
and ground support vehicles to alternative fuels technologies.22) Unfortunately, the state and
industry stakeholders did not reach consensus on a national aviation emissions reduction
program. The Agencies are currently contemplating next steps following from the national
stakeholder initiative and discussions of potential voluntary programs, and the approaches
suggested above by commenters will be taken under consideration.
In addition, the approaches or measures described above by commenters are not within
the scope of this rulemaking since we only proposed new NOX standards for aircraft main
engines. Promulgating such approaches/measures would require another notice and comment
rulemaking action. Moreover, we would need to develop a cost and emission benefit analysis for
these approaches. Instead of slowing down the implementation of the aircraft engine NOX
standards promulgated in this final rule, we may consider such an analysis and the
approaches/measures in the future.
19Two engine models were indeed certificated with emissions retrofit kits, and a number
of these engines have been purchased for aircraft with the retrofit kits installed in their stock
configuration. However, retrofit kits have not to date provided widescale emissions
improvements because it seems they may have limited applicability to certain engine types,
small emission benefits, and cost issues.
20The stakeholders considered the impact, operation and design of GSE at airports, and
whether to undertake projects at several airports to reduce overall emissions.
21Operational strategies, such as reducing the time in which aircraft are in idle and taxi
modes and the impact of auxiliary power units (APUs) were also considered.
22The Vision 100-Century of Aviation Reauthorization Act, signed into law on December
12, 2003 (P.L. 108-176), directs the FAA to establish a national program to reduce airport
ground emissions at commercial service airports located in air quality nonattainment and
maintenance areas. The new Voluntary Airport Low Emissions (VALE) program will allow
airport sponsors to use the Airport Improvement Program (AIP) and Passenger Facility Charges
(PFCs) to finance low- emission vehicles, refueling and recharging stations, gate electrification,
and other airport air quality improvements. See the FAA website located at
www. faa. gov/arp/environmental/vale.
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5. Other Issues
What We Proposed:
The items raised in the following comments were not specifically addressed in the
NPRM, and therefore have no general corresponding NPRM section.
5.1 Environmental Justice
What Commenters Said:
Bluewater Network expressed that since EPA's proposed NOX standards do not provide
meaningful emission reductions, it results in environmental injustice for communities near some
airports. Thus, EPA is not fulfilling it's obligation under the Executive Order on Environmental
Justice (Executive Order 12898) and EPA's Policies on Environmental Justice. For example, in
Atlanta, Georgia, Black or African-American residents are 81 percent of the population living
close to the Hartsfield Atlanta International Airport (4 closest zip code areas), in comparison to
about 32 percent in the urban area of Atlanta. The median household income in the same area
close to the airport ranges from $28,155 to $39,141, in comparison to $52,512 in the Atlanta
urban area. "Even in the absence of statistical testing, this demographic data strongly imply that
people of color and low-income communities may experience increased exposure to air pollution
from airports."
Our Response:
EPA supports implementing the Executive Order on Environmental Justice. However, its
provisions are not relevant because like other technology-based or performance-based rules we
adopt under the CAA, according to section 231 of the Act we have based the level of the
standards promulgated in the rule on what we expect can be met after considering technology
development, lead time, and costs of compliance (without consideration of the specific effect the
standards have on air quality and meeting the NAAQS). Moreover, as we discussed earlier, EPA
intends to address more stringent emission standards requiring more lead time in a future
rulemaking (a ongoing phased approach to address aircraft emissions). In addition, as discussed
in the preambles of the NPRM and final rule, air pollutants resulting from airport operations are
emitted from several types of sources: aircraft main engines and auxiliary power units (APUs);
ground service equipment (GSE); ground access vehicles (GAV), which include vehicles from
off-site used by passengers, employees, freight operators, and other persons utilizing an airport.
EPA's previous estimates show aircraft engines comprise approximately 45 percent of total air
pollutant emissions from airport operations; GAV account for another 45 percent, and APUs and
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GSE combined make up the remaining 10 percent.23 As stated earlier, EPA has established
stringent emission standards for GAVs and other on-highway motor vehicles (and new GSE and
other nonroad equipment), and overall emissions from these vehicles (and equipment) will
continue to decline for many years while the growth in commercial aircraft emissions is expected
to continue. Even though aircraft are and/or will be the predominant source of emissions at
airports, they are not the only source of emissions. Aircraft are one of several contributors
(including stationary sources at airports as well) to emissions at or around airports. Therefore,
EPA will continue to take a holistic approach to reducing emissions and improving air quality in
and around airports (keep on focusing our efforts on all sources of emissions in and around
airports).
5.2 General Aviation and Military Aircraft
What Commenters Said:
Bluewater Network suggested that the NPRM exempts all general aviation, air taxi, and
military aircraft engines from EPA emission regulations. "Failure to regulate them would be
arbitrary and capricious and inconsistent with the law, again in light of the harm of ozone
pollution, the nonattainment problem nationwide, and the contribution of aircraft pollution to
local air problems." In section 231 of the CAA, Congress required the Agency to issue emission
standards from "any class or classes of aircraft or aircraft engines." The terms "aircraft" and
"aircraft engines" are defined to comprise all types of aircraft and engines. These terms do not
exclude general aviation and military aircraft engines (see section 234 of the CAA).
Also, the State of New Jersey Department of Environmental Protection (NJDEP)
expressed that the proposed NOX standards could also apply to engines with a rated output less
than 26.7 kilonewtons, which would address smaller air taxis and business jets. Such action
would enable the U.S. to obtain greater emission reductions and provide "the international
community a more environmental friendly blueprint."
23The California FIP, signed by the Administrator 2/14/95, is located in EPA Air Docket
A-94-09, item number V-A-1. The FIP was vacated by an act of Congress before it became
effective.
For comparison, the 1997 EPA Draft Final Report entitled, "Analysis of Techniques to
Reduce Air Emission at Airports" (prepared by Energy and Environmental Analysis, Inc), it was
estimated that for the four airports studied (which are large air traffic hubs) on average aircraft
compromise approximately 35 percent of NOX emissions from airport operations; GAV account
for another 35 percent, and APUs and GSE contribute about 15 percent each for the remaining
30 percent. For NOX and volatile organic compounds (VOC) together, aircraft contribute about
35 percent; GAV account for another 40 percent, and APUs and GSE combined make up the
remaining 25 percent. This document can be found in Docket No. OAR-2002-0030.
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In addition, Bluewater network indicated that the Agency has gone beyond its authority
by excluding military aircraft and aircraft engines since only the President may provide such
exemptions under section 118 of the CAA (Control of Pollution from Federal Facilities). This
section directs federal agencies to comply with air pollution control requirements "in the same
manner, and to the same extent as any nongovernmental entity." If exemptions for the military
could be carried out at the rulemaking level, the necessity for a presidential exemption would
become meaningless. Furthermore, Congress' intent that the military follow the same
requirements that apply to non-governmental entities would be easily frustrated if EPA were
permitted to exclude military in this rule.
Also, Bluewater Network commented that emissions from exempted aircraft engines -
from 1 to 26 percent of emissions from all aircraft engines - are considerable; therefore, EPA
has to explain its rationale for the exemption. In the NPRM, the Agency did not describe why
these emissions would be exempted. "EPA's failure to regulate these sources is thus arbitrary
and capricious."
In addition, as described earlier SCAQMD expressed that the 2003 Proposed State and
Federal Strategy for the California SIP calls for EPA to assess options for decreasing aircraft
emissions, including the application of standards for commercial aircraft engines to non-tactical
military aircraft.
Our Response:
The promulgated NOX standards apply to commercial aircraft engines of rated thrust
greater than 26.7 kilonewtons, and general aviation and military aircraft can use commercial
aircraft engines subject to these standards (e.g., small regional jet engines are also utilized in
executive general aviation aircraft and larger commercial aircraft engines may also be used in
military transport aircraft). In the NPRM, we stated that no general aviation or military engines
are covered by the proposal. However, this statement may need some clarification (and was
revised in the preamble of the final rule). For general aviation, EPA's 1982 aircraft final rule
withdrew emission standards "for all gas turbine engines used only for general aviation
applications" (and for all gas turbine engines of rated thrust less than or equal to 26.7
kilonewtons), but emission standards for aircraft gas turbine engines used for commercial
transport by air carriers or commercial operators remained (although the standards were
revised).24 Currently, some engines used in commercial transport also power general aviation
aircraft (e.g., business jets), and because such engines are used in commercial applications (and
not merely general aviation operation), they must comply with EPA's aircraft engine emission
standards - including the standards promulgated in this final rule. Therefore, it is more
appropriate to state that the promulgated NOX emission standards do not apply to aircraft engines
used only for general aviation or military applications.
24U.S. EPA, "Control of Air Pollution from Aircraft and Aircraft Engines; Emission
Standards and Test Procedures," Final Rule, 47 FR 58462, December 30, 1982.
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In regard to regulating general aviation aircraft engines, military aircraft engines, and
aircraft engines with a rated output less than or equal to 26.7 kilonewtons, it is important to note
that the scope of this rulemaking was limited to adopting NOX standards equivalent to the
CAEP/4 NOX standards for commercial aircraft gas turbine engines of rated thrust greater than
26.7 kilonewtons. Such engines were the only type of aircraft engines we requested comment on
in the NPRM for amending the NOX standards, and thereby bringing the United States emissions
standards into alignment with the internationally adopted standards. We may have mentioned
other types of aircraft engines in the NPRM, but we did not invite comments on applying the
new NOX standards to these other types of aircraft engines. Thus, regulating these other types of
aircraft engines is not within the scope of this rulemaking.
In addition, our record to support regulations for aircraft engines other than commercial
aircraft engines greater than 26.7 kilonewtons was similarly limited. We did not assess costs,
emission benefits, and the state of technology related to such engines for the NPRM, and we
have yet to conduct such an assessment to support regulations for these engines. To finalize
standards for these other types of aircraft engines, we believe this information would first need to
have been put out for public comment. Also, there are a number of issues regarding enforcement
mechanisms and legal authority that we would similarly need to address through a notice and
comment process before adopting regulations for the other types of aircraft engines.
Currently, as described in the NPRM and the preamble of the final rule, nationwide
aircraft emission estimates have limitations for military aircraft (and thus, a range of commercial
aircraft's emissions contribution to nationwide aircraft NOX was provided - see section II of the
preamble for the final rule for further discussion of this range). The documentation for EPA's
most recent national aircraft emission estimates identifies the areas of improvement to enhance
the emissions estimates.25 In particular, for military aircraft emissions we need to obtain better
activity data for the diverse aircraft included in this category. In the future, EPA will be working
to improve the data for military aircraft emissions.
5.3 Auxiliary Power Units
What Commenters Said:
The TCEQ expressed that EPA has failed to address aircraft auxiliary power units
(APUs), which are a considerable source of NOX emissions.
25U.S. EPA, "Documentation for Aircraft, Commercial Marine Vessel, Locomotive, and
other Nonroad Components of the National Emissions Inventory, Volume I - Methodology,"
Prepared for EPA by Eastern Research Group, Inc., October 7, 2003. A copy of this document
can be found in Docket No. OAR-2002-0030.
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Our Response:
APUs are not within the scope of this rulemaking since we only proposed new NOX
standards for aircraft main engines. New emission standards for APUs would require another
notice and comment rulemaking action. For estimates of APUs' contribution to total emissions
from airports, see the above discussion in the Environmental Justice section of this document
(section 5.1).
5.4 Ground Service Equipment
What Commenters Said:
ED commented that a considerable amount of air pollution from airports is the result of
ground service equipment (which include vehicles such as aircraft tugs, baggage tugs, fuel
trucks, maintenance vehicles, and other miscellaneous vehicles used to support aircraft
operations). EPA should quickly finalize the nonroad diesel emission standards proposed in
April 2003 and expand the voluntary diesel retrofit program to achieve substantial, lasting
reductions in these important sources of air pollution.
Our Response:
EPA finalized the new nonroad diesel emission standards on June 29, 2004 (69 FR
38958).26 In addition, most GSE are powered by nonroad large spark-ignition engines, and EPA
promulgated standards for these engines on November 8, 2002 (67 FR 68242).27 In addition, see
our response to comments in section 4 (Approaches to Additional Aviation Emission Reductions)
for a discussion of the national stakeholder initiative and its relation to GSE. For estimates of
GSE's contribution to total air pollutant emissions from airport operations, see the earlier
discussion in the Environmental Justice section of this document (section 5.1).
5.5 Lead from Aviation Gasoline
What Commenters Said:
Bluewater Network stated that while the downward trend in mean blood-lead levels
(since the 1970's) in children is encouraging, particular subpopulations are still exposed to lead.
"For example, according to EPA, residents near "general aviation airports where leaded gasoline
26U.S. EPA, "Control of Emissions of Air Pollution from Nonroad Diesel Engines and
Fuel," Final Rule, 69 FR 38958, June 29, 2004.
27U.S. EPA, "Control of Emissions from Nonroad Large Spark-Ignition Engines, and
Recreational Engines (Marine and Land-Based)" Final Rule, 67 FR 68242, November 8, 2002.
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is still being used as fuel may have an increased risk of lead exposure.28" Lead from general
aviation aircraft may also effect workers and maintenance employees, as well as aircraft
passengers. Also, lead emissions can be deposited in wetlands and other ecologically sensitive
areas next to airports.
In addition, Bluewater Network indicated that in 1970 Congress gave EPA the
responsibility under section 231 of the CAA to determine whether emissions from aircraft
endanger the public health or welfare. At the same time, Congress provided FAA with the
authority to set standards for aircraft fuel and fuel additives to control or eliminate aircraft
emissions that EPA "decides under section 231 of the Clean Air Act endangers public health or
welfare" (49 U.S.C. § 44714). In a 1972 aircraft emissions study, EPA concluded that "the
existing and potential air quality impact of sulfur oxides and lead is considered to be negligible
in comparison to other sources of these two pollutants.29" Therefore, the Agency did not conduct
any further analysis of the two pollutants.
Bluewater Network suggested that since 1972 two developments have undermined EPA's
rationale for not studying lead pollution from aircraft further. First, nowadays lead is recognized
as being much more toxic (previously safe blood level for children of 40 mcg/dL to current
concentration of concern for lead paint of 10 mcg/dL). Second, because lead emissions from on-
highway mobile sources have been practically eliminated, lead from pollution from general
aviation aircraft now makes up a much greater fraction of total lead emissions. Also, Bluewater
Network commented that EPA's 1999 National Emission Inventory indicated that aircraft
emissions contribute about 16 percent of total lead emissions. Due to these developments and
the health and environmental concerns near airports that Bluewater Network expressed earlier,
they recommended that EPA make a determination that under section 231 of the Act aircraft lead
emissions endanger public health and welfare. This step would prompt FAA's duty to control or
eliminate aircraft lead emissions.
In addition, Bluewater Network commented that they are concerned that EPA's work
with FAA on a voluntary process to remove lead from aviation gas will not result in a phase-out
of lead in any reasonable time period. Without pressure from regulations, the goal of removing
lead from aviation gas could be delayed for an indefinite period. "In fact, concern that voluntary
measures were not accomplishing the air pollution control goals motivated Congress to add
section 231 to the CAA in the first place."
28U.S. EPA, Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Alkyl-Lead Work
Group, "Draft PBT National Action Plan for Alkyl-lead," May 8, 2000. A copy of this
document can be found in Docket No. OAR-2002-0030.
29U.S. EPA, "Aircraft Emissions: Impact on Air Quality and Feasibility of Control,"
1972. A copy of this document can be found in Docket No. OAR-2002-0030.
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Our Response:
Based on EPA's 2003 National Air Quality and Emission Trends Report?0 in 2000
nationwide lead emissions from aircraft were 545 tons per year, and total lead emissions from all
sources were reported as 4,228 tons per year. Thus, based on the latest available information
aircraft emissions represent about 13 percent of the total lead emissions, which is similar to the
fraction provided by the commenter. In addition, for the remaining mobile sources emitting
exhaust emissions of lead, aircraft are the most significant.
Currently, aviation gasoline is the only aviation fuel containing lead. Aviation gasoline
is utilized in a relatively small number of aircraft (within the general aviation aircraft category),
those with piston engines, which are generally used for personal transportation, sightseeing, crop
dusting, and similar activities. (Lead is not used in jet fuel, the fuel utilized by most commercial
aircraft.) Part of the lead additive package used to boost the octane of aviation gasoline keeps
the lead volatile so that it does not deposit in the engine. Such deposits result in poorer
performance and increased maintenance costs.
Because of our general concern for lead emissions in aviation gasoline, we have been
encouraging FAA to develop an unleaded aviation gasoline. Research by FAA continues for
unleaded aviation gasoline, but has yet to be successful. To ban lead emissions from aircraft, in
the absence of an unleaded aviation gasoline, would ground the aircraft described above,
resulting in severe economic penalties for the many small businesses which utilize them.
Moreover, the 2000 EPA draft action plan for lead31 discussed earlier was finalized in 2002, and
the final plan stated (as did the draft plan) that the desire to find a no-lead gasoline substitute for
aviation gasoline needs to be balanced with safety concerns.32 The performance of an unleaded
high-octane aviation gasoline in all possible and operational and atmospheric conditions must be
thoroughly tested due to concerns pertaining to aircraft safety. High-performance piston aircraft
engines need high-octane gasoline, and lead is extremely efficient at increasing the octane
without creating any other undue performance effects.
30U.S. EPA, "National Air Quality and Emissions Trends Report - 2003 Special Studies
Edition," EPA 454/R-03-005. A copy of this document can be found in Docket No. OAR-2002-
0030.
31U.S. EPA, Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Alkyl-Lead Work
Group, "Draft PBT National Action Plan for Alkyl-lead," May 8, 2000. A copy of this
document can be found in Docket No. OAR-2002-0030.
32U.S. EPA, Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Program, "PBT
National Action Plan for Alkyl-lead," June, 2002. This document is available at
www.epa.gov/pbt/pubs/alkyl_lead_action_plan_final.pdf A copy of this document can be found
in Docket No. OAR-2002-0030.
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We acknowledge that as aviation gasoline with lead is still utilized certain
subpopulations may remain at risk. However, as indicated in the 2002 final EPA action plan for
lead, there is insufficient information to evaluate whether the remaining uses of lead (including
aviation gasoline) result in adverse public health or welfare effects. In particular, there is no
information to determine whether there is increased risk to lead exposure to at-risk populations
(especially children) living near general aviation airports, spectators at air shows, and fuel
handlers (aviation crews). Therefore, we do not believe we currently have sufficient information
that would enable us to make a determination whether aircraft lead emissions may reasonably be
anticipated to endanger public health and welfare. Nevertheless, EPA will continue to pursue
voluntary initiatives to the reduce the use of lead in aviation gasoline and collect information as
possible.
5.6 Limits for Hydrocarbons, Particulate Matter, Air Toxics, and Sulfur Dioxide
What Commenters Said:
Bluewater Network indicated that EPA last regulated hydrocarbon emissions for aircraft
engines back in 1982. Because hydrocarbons are precursors to ozone and many of the same
reasons the Agency proposes to amend the aircraft engine NOX standards apply to hydrocarbons,
EPA should revisit the hydrocarbon requirements to make them stronger.
A few commenters expressed concerns with particulate matter, air toxics, and sulfur
dioxide emitted from aircraft engines. CARB urged EPA to consider limits on PM2 5 and air
toxics in future aircraft rules to control the complete range of air pollutants that endanger our
health. STAPPA/ALAPCO indicated that particulate matter and sulfur dioxide emissions from
aircraft engines require a better understanding than is presently available. Moreover,
STAPPA/ALAPCO stated that "EPA must be a leader in research in this area and set appropriate
standards when sufficient data is available." In addition, AReCO suggested that new aircraft
engine certifications should include measurements and characterization of PM10 and PM25
starting in 2004, and this requirement should be expanded to all existing engines over the next
three years. Also, AReCO expressed concerns with the health effects from air toxics emitted
from aircraft and at airports.
Our Response:
Aircraft engine emissions of hydrocarbons (HC), particulate matter (PM), sulfur dioxide
(SO2), and air toxics are not within the scope of this rulemaking since we only proposed new
NOX standards. In addition, we did not request comments on these other pollutants in the
NPRM. New aircraft engines standards for pollutants other than NOX would require another
notice and comment rulemaking action. Therefore, we are not prepared in this final rule to either
revise standards for hydrocarbon emissions or set standards for PM, SO2, or air toxics.
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5.7 Interrelationships on Pollutants, Noise, and Performance
What Commenters Said:
A number of commenters expressed that in setting new standards (now and in the future)
the EPA needed to consider the interrelationships with other pollutants, noise, and performance
factors (including fuel efficiency and safety).
Our Response:
We agree that such interrelationships should be considered for today's and future
standards. For today's standards these interrelationships were taken under consideration (as
discussed earlier in this document), and for future standards we intend to do the same.
5.8 Regulations for Airports
What Commenters Said:
AReCO urged EPA to immediately amend regulations so all airports are considered to be
consolidated sources of emissions. Such provisions "should include all fixed, mobile, and area
sources of airport and aircraft related emissions, both on and off airport property as well as
aircraft operations below 3,000 meters altitude." Also, AReCO expressed that from now on all
airport expansion projects with an activity increase, should have environmental assessments and
effective mitigation of consolidated airport activities that lead to exceedances in ambient air
quality standards for particulate matter (at least PM2 5).
In addition, AReCO suggested that they agree with the General Accounting Office33 in
their opposition to massive expansion of existing airports and their solutions to addressing long-
term capacity needs. AReCO stated that these solutions are the following: "(1) take the issue
away from the FAA and make this a transportation issue not just an aviation issue; (2) put back
the airport operational and management controls, the removal of which started the massive
airport delays we saw in 2000; (3) build a national Wayport system; and (4) build a world-class
national and high-speed rail system."
Our Response:
Requirements for airports as one source of emissions and airport capacity are not within
the scope of this rulemaking since we only proposed new NOX standards for commercial aircraft
engines. New regulations for airports would require another notice and comment rulemaking
action.
33U.S. General Accounting Office, "Long-Term Capacity Planning Needed Despite
Recent Reduction in Flight Delays," GAO-02-185, December 2001.
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5.9 Greenhouse Gases
What Commenters Said:
AReCO stated that the U.S. General Accounting Office (GAO) assessed the climate
change issue and found that aviation emissions accounted for about three percent of the
greenhouse gases and other emissions that contribute to global warming. Even though this
percentage is relatively small, aviation emissions are potentially significant for a number of
reasons:
"1. Jet aircraft emissions are deposited directly into the upper atmosphere and some of them
have a greater warming effect than gases emitted closer to the surface, such as automobile
exhaust.
2. The primary gas emitted by jet aircraft engines is carbon dioxide, which can survive in the
atmosphere up to 100 years.
3. Carbon dioxide, combined with other exhaust gases and particulates emitted from jet engines
could have two to four times as great an impact on the atmosphere as carbon dioxide emissions
alone."
Also, AReCO indicated that the GAO report recommended additional research into the effect of
jet aircraft emissions on the global atmosphere to help guide the development of new aircraft
engine technology.
In addition, AReCO suggested that many new studies now "point to commercial jet aircraft as a
major, if not the major cause of man-made climate change." One commenter also stated that
aircraft emit "frightening" amounts of greenhouse gases and other pollutants.
Our Response:
EPA is promulgating amendments to the NOX emission standard for aircraft engines in
order to address the direct adverse impacts of NOX emissions on public health, welfare and the
environment, rather than to address climate change. Issues related to climate change are
therefore beyond the scope of this rulemaking. Moreover, EPA has previously determined that it
does not have authority under the CAA to regulate greenhouse gas (GHG) emissions to address
global climate change. See 68 Fed. Reg. 52,922, 52,925 (September 8, 2003).
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5.10 Altitude Where the Majority of Aircraft Emissions Occur
What Commenter Said:
AReCO stated "that airports and their operations are major local point or area emission
sources, since over 90% of aircraft emissions are emitted at or relatively near the airport during
the landing and take-off cycles."
Our Response:
We would agree that airports are significant sources of emissions (as discussed in section
3, Environmental Need for Control of this document), but we do not agree that over 90 percent
of aircraft emissions are emitted during the landing and take-off cycles. NASA, in a 2001 report
entitled, "Scheduled Civil Aircraft Emission Inventories for 1999: Data Base Development and
Analysis," found that approximately 9 percent of aircraft NOX emissions for the scheduled global
fleet in May 1999, occurred at an altitude of 0 tol kilometers (0 to 3,281 feet). (Typically, the
landing and take-off cycle occurs up to an altitude of 3,000 feet, which is a default mixing height
used for emission inventory calculations.34) In addition, approximately 58 percent of aircraft
NOX emissions occurred at altitudes ranging from 10 to 12 kilometers (32,808 to 39,370 feet), the
typical cruise mode of operation.35
5.11 Contrails
What Commenters Said:
We received several comments from the general public expressing a concern about
contrails produced by commercial and military aircraft. Commenters alleged that many contrails
they observed were not "normal," but produced as a result of aircraft fitted with spraying
devices, or direct injection into the engine(s) with compounds in order to disperse and spray a
wide variety of chemicals or other harmful agents upon U.S. population centers. Some
commenters claimed a number of health effects from these aircraft activities including, but not
limited to colds, congestion, aches, respiratory, and skin problems.
34U.S. EPA, Evaluation of Air Pollutant Emissions from Subsonic CommercialJet
Aircraft, Prepared for EPA by ICF Consulting Group. U.S. Environmental Protection Agency,
April 1999, EPA-420-R-99-013. This document is available at www.epa.gov/otaq/aviation.htm.
A copy of this document can also be found in Docket No. OAR-2002-0030.
35NASA, Donald J. Sutkus, Jr. et al., Scheduled Civil Aircraft Emission Inventories for
1999: Database Development and Analysis, October 2001, NASA/CR-2001-211216. This
document is available at
gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?2001/CR-2001-211216.html. A copy of this
document can also be found in Docket No. OAR-2002-0030.
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A commenter stated that these spraying operations were intentionally carried out to
produce cloudy sky conditions on what commenced as a clear day. Another commenter claimed
observing a jetliner dumping jet fuel (apparently not for emergency purposes) through spray
nozzles. Some commenters advanced the theory that persistent contrails are abnormal and
offered this as evidence to support their allegations of chemical spraying, while another stated
that this was a "secret" government program, its scope and purpose withheld from the general
public.
Our Response:
EPA is unaware of any program to spray U.S. population centers with chemicals or other
substances from jets or any another type of aircraft. What we can do is provide an explanation of
how jet exhaust occasionally forms contrails.
Jet aircraft engines operating at high altitudes emit tiny particles that serve as
condensation nuclei. High-altitude water vapor collects on these particles, crystallizes, and
forms streaks of frozen water vapor otherwise known as contrails. Some contrails join with
other contrails and expand into large, natural-looking clouds of cirrus characteristics that can
cover large areas of the sky. (Cirrus clouds are wispy white, usually a natural phenomenon,
consisting of minute ice crystals formed at high altitudes of 20,000 to 40,000 feet.) Research by
the National Aeronautics and Space Administration (NASA) has recognized jet aircraft cloud
formation as a potential problem for blocking sunlight, but not solar heat reaching the earth,
thereby acting as a thermal blanket and perhaps contributing to global warming.
In September 2000, EPA published a document entitled, Aircraft Contrails Factsheet,
EPA430-F-00-005, in conjunction with NASA, the National Oceanic and Atmospheric
Administration (NOAA), and the Federal Aviation Administration (FAA). This fact sheet
describes the formation, occurrence, and effects of "condensation trails" or contrails, and it is
located on EPA's web site at: www.epa.gov/otaq/aviation.htm. Information from the Air Force
about military aircraft and their atmospheric and environmental effects can be found at:
http://www.af.mil/shared/media/document/AFD-051013-001 .pdf
Also, a 1999 report issued by the Intergovernmental Panel on Climate Change, entitled,
Aviation and the Global Atmosphere, discusses contrail formation and its effects in detail. The
influence of contrails on cirrus clouds is noted as a key area of scientific uncertainty that limits
the ability to project aviation impacts on climate and ozone. Further work is required to reduce
scientific and other uncertainties of aviation impacts. EPA fully supports continued research to
address these issues.36
^Intergovernmental Panel on Climate Change (IPCC), "Aviation and the Global
Atmosphere," I.E. Penner, D.H. Lister, D. J. Griggs, D. J. Dokken, and M. McFarland, editors.
Cambridge University Press, 373 pp., 1999.
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5.12 Deicing
What Commenter Said:
A commenter expressed a concern about chemical deicing of aircraft and the resulting
pollution.
Our Response:
Aircraft deicing is not within the scope of this rulemaking since we only proposed new
NOX standards for aircraft engines.
5.13 Airport Water and Noise Pollution
What Commenter Said:
AReCO expressed a concern that "airport operations emit extraordinary levels of air,
ground, water and noise pollution."
Our Response:
Water and noise pollution from airports are not within the scope of this rulemaking since
we only proposed new NOX standards for aircraft engines. For a discussion of air pollution at
airports, see sections 3.2 and 5.8 of this document {Aircraft Emissions Contribution and
Regulations for Airports).
5.14 Effect of September 11, 2001, and Economic Downturn on Emissions Growth
What Commenters Said:
In regard to the effect of September 11, 2001 and the economic downturn on the
projected growth of commercial aircraft emissions, ATA indicated that major airlines decreased
their flight schedules and grounded aircraft. The NPRM (Table III-l) references the FAA
Terminal Area Forecast summaries (December 2000 and May 2003), which reflect the decreased
level of aircraft activity after 2000. Also, nearly every major airline altered its fleet plan to
reflect its changing economic situation.
In addition, ATA expressed that EPA has the ability to translate actual post-September 11
activity data and continuing forecasts into emissions data, as part of its ongoing assessment of
national emissions trends. The Agency's February 2003 national emissions inventory (updated
through 2001), indicates that 2001 aircraft NOX to be 19 percent below their peak, and at their
lowest point since 1996. "EPA has at its disposal the data and models that would allow it to
make the more refined post-September 11 analysis that it seeks. ATA and its member carriers
have not had the resources to devote to such an analysis, particularly in view of the many non-
cyclical factors that have affected industry operations, such as the wars in Afghanistan and Iraq
and SARS."
Our Response:
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We would not disagree with the commenter's characterization of nationwide aircraft NOX
in 2001 compared to prior years. More recent EPA estimates of national aircraft NOX show
similar trends.37 In addition, recent (June 2005) FAA Terminal Area Forecast summaries
continue to show a reduced level of aircraft operations after 2000. However, as indicated in the
NPRM and the preamble of the final rulemaking, the FAA expects the demand for air travel to
recover, and then continue a long-term trend of annual growth in the United States (though from
a lower base and a slower rate in the United States).38 FAA reports (2005 Terminal Area
Forecasts) that flights of commercial air carriers and commuters/air taxis will increase by 22
percent from 2000 to 2015, about 12 percent less than what was forecast before September
llth.39'40
5.15 Funding Clean Engine Research
What Commenter Said:
AReCO suggested that airlines should be required to contribute (e.g., through passenger
facility charges) at least $10 million per year to EPA and NASA for research aimed at reducing
aircraft engine emissions.
Our Response:
37U.S. EPA, "Documentation for Aircraft, Commercial Marine Vessel, Locomotive, and
Other Nonroad Components of the National Emissions Inventory, Volume I - Methodology,"
Prepared by Eastern Research Group, Inc., October 7, 2003. This document is available at
www.epa.gov/ttn/chief/net/1999inventory.html. A copy of this document can also be found in
Docket No. OAR-2002-0030.
38U.S. General Accounting Office, "Aviation and the Environment: Strategic Framework
Needed to Address Challenges Posed by Aircraft Emissions," GAO-03-252, February 2003.
This document is available at www.gao.gov/cgi-bin/getrpt7GAO-03-252. and it can also be
found in the Docket No. OAR-2002-0030.
39U.S. FAA, "APO Terminal Area Forecast Summary Report," Aircraft Operations, June
30, 2005. The flight forecast data is based on FAA's Terminal Area Forecast System (TAPS).
TAFs is the official forecast of aviation activity at FAA facilities. This includes FAA-towered
airports, federally-contracted towered airports, nonfederal towered airports, and many
non-towered airports. For detailed information on TAFS and the air carrier activity forecasts see
the following FAA website: http://www.apo.data.faa.gov/main/taf.asp. The June 30, 2005
aviation forecasts contained in TAFS for Fiscal Years 2002-2020 included the impact of the
terrorists' attacks of September 11, 2001 and the recent economic downturn. Currently, the
aviation industry is undergoing significant structural and economic changes. These changes may
necessitate revisions to forecasts for a number of large hub airports prior to the update of the
entire TAP next year. A copy of the June 30, 2005 forecast summary report can also be found in
Docket No. OAR-2002-0030.
40U.S. FAA, "APO Terminal Area Forecast Summary Report," Aircraft Operations,
December 14, 2000. A copy of this document can be found in Docket No. OAR-2002-0030.
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Such a funding program is not within the scope of this rulemaking since we only
proposed new NOX standards for aircraft engines.
5.16 Voting Representation in CAEP Process
What Commenter Said:
In another comment, AReCO expressed that EPA and FAA need to demand that 1CAO
have significant representation from environmental interests for CAEP meetings, [otherwise] the
U.S. will appropriately reduce its funding to ICAO/CAEP.
Our Response:
A change in the representation structure within CAEP is not within the scope of this
rulemaking since we only proposed new NOX standards for aircraft engines.
5.17 Accuracy of Method to Determine Visibility
What Commenter Said:
The commenter expressed the opinion that in footnote 72 of the NPRM (Section III,
Environmental Need for Control) that we define "visibility" by using a subjective method in part
as follows: "Visual range can be defined as the maximum distance at which one can identify a
black object against the horizon sky. Visibility is typically described in miles or kilometers."
The commenter was concerned that a subjective method to determine visibility would result in a
loss of accuracy.
Our Response:
The commenter is technically correct that use of a photometric method and
instrumentation would probably produce more accurate visibility determinations. However, for
ease of implementation, we plan on making visibility estimates by employing the visual method
partially described in footnote 72 of the Proposed Rule.
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