Document ID: EPA-HQ-OAR-2019-0660-0131
Agency: epa
Document Type: Proposed Rule
Title: Control of Air Pollution from Aircraft Engines: Emission Standards and Test Procedures
Posted Date: 2022-02-03T05:00Z

[Federal Register Volume 87, Number 23 (Thursday, February 3, 2022)]
[Proposed Rules]
[Pages 6324-6362]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-01150]

[[Page 6323]]

Vol. 87

Thursday,

No. 23

February 3, 2022

Part III

 Environmental Protection Agency

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40 CFR Parts 87, 1030, and 1031

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

  Federal Register / Vol. 87 , No. 23 / Thursday, February 3, 2022 / 
Proposed Rules  

[[Page 6324]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 87, 1030, and 1031

[EPA-HQ-OAR-2019-0660; FRL-7558-01-OAR]
RIN 2060-AU69

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing 
particulate matter (PM) emission standards and test procedures 
applicable to certain classes of engines used by civil subsonic jet 
airplanes (those engines with rated output of greater than 26.7 
kilonewtons (kN)) to replace the existing smoke standard for aircraft. 
These proposed standards and test procedures are equivalent to the 
engine standards adopted by the United Nations' International Civil 
Aviation Organization (ICAO) in 2017 and 2020 and would apply to both 
new type design aircraft engines and in-production aircraft engines. 
The EPA, as well as the United States Federal Aviation Administration 
(FAA), actively participated in the ICAO proceedings in which these 
requirements were developed. These proposed standards would reflect the 
importance of the control of PM emissions and U.S. efforts to secure 
the highest practicable degree of uniformity in aviation regulations 
and standards. Additionally, the EPA is proposing to migrate, 
modernize, and streamline the existing regulations into a new part. As 
part of this update, the EPA is also proposing to align with ICAO by 
applying the smoke number standards to engines less than or equal to 
26.7 kilonewtons rated output used in supersonic airplanes.

DATES: Comments on this proposal must be received on or before April 4, 
2022.
    Public hearing: EPA will announce the public hearing date and 
location for this proposal in a supplemental Federal Register document.

ADDRESSES: 
    Comments: EPA solicits comments on all aspects of the proposed 
standards.
    Written comments: Submit your comments, identified by Docket ID No. 
EPA-HQ-OAR-2019-0660, at https://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. The EPA may publish any 
comment received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The EPA is temporarily suspending its Docket Center and Reading 
Room for public visitors, with limited exceptions, to reduce the risk 
of transmitting COVID-19. Our Docket Center staff will continue to 
provide remote customer service via email, phone, and webform. We 
encourage the public to submit comments via https://www.regulations.gov 
as there may be a delay in processing mail and faxes. For further 
information and updates on EPA Docket Center services, please visit us 
online at https://www.epa.gov/dockets.
    The EPA continues to carefully and continuously monitor information 
from the Centers for Disease Control and Prevention (CDC), local area 
health departments, and our Federal partners so that we can respond 
rapidly as conditions change regarding COVID-19.
    Docket: EPA has established a docket for the action under Docket ID 
No. EPA-HQ-OAR-2019-0660. All documents in the docket are listed on the 
www.regulations.gov website. Although listed in the index, some 
information is not publicly available, e.g., confidential business 
information or other information whose disclosure is restricted by 
statute. Certain other material, such as copyrighted material is not 
placed on the internet and will be publicly available only in hard copy 
form. Publicly available docket materials are available either 
electronically through www.regulations.gov or in hard copy at the 
following location:
    Air and Radiation Docket and Information Center, EPA Docket Center, 
EPA/DC, EPA WJC West Building, 1301 Constitution Ave. NW, Room 3334, 
Washington, DC.
    Out of an abundance of caution for members of the public and our 
staff, the EPA Docket Center and Reading Room was closed to public 
visitors on March 31, 2020, to reduce the risk of transmitting COVID-
19. Our Docket Center staff will continue to provide remote customer 
service via email, phone, and webform. We encourage the public to 
submit comments via https://www.regulations.gov or email, as there is a 
temporary suspension of mail delivery to EPA, and no hand deliveries 
are currently accepted. For further information on EPA Docket Center 
services and the current status, please visit us online at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: Bryan Manning, Office of 
Transportation and Air Quality, Assessment and Standards Division 
(ASD), Environmental Protection Agency, 2000 Traverwood Drive, Ann 
Arbor, MI 48105; telephone number: (734) 214-4832; email address: 
[email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    A. Does this action apply to me?
    B. Executive Summary
    1. Summary of the Major Provisions of the Proposed Regulatory 
Action
    2. Purpose of the Proposed Regulatory Action
    3. Environmental Justice
II. Introduction: Context for This Proposed Action
    A. EPA Statutory Authority and Responsibilities Under the Clean 
Air Act
    B. The Role of the United States in International Aircraft 
Agreements
    C. The Relationship Between EPA's Regulation of Aircraft Engine 
Emissions and International Standards
III. Particulate Matter Impacts on Air Quality and Health
    A. Background on Particulate Matter
    B. Health Effects of Particulate Matter
    C. Environmental Effects of Particulate Matter
    1. Deposition of Metallic and Organic Constituents of PM
    2. Materials Damage and Soiling
    D. Near-Source Impacts on Air Quality and Public Health
    E. Contribution of Aircraft Emissions to PM in Selected Areas
    F. Other Pollutants Emitted by Aircraft
    G. Environmental Justice
IV. Details for the Proposed Rule
    A. PM Mass Standards for Aircraft Engines
    1. Applicability of Standards
    2. New Type nvPM Mass Numerical Emission Limits for Aircraft 
Engines
    3. In Production nvPM Mass Numerical Emission Limits for 
Aircraft Engines
    4. Graphical representation of nvPM Mass Numerical Emission 
Limits
    B. PM Number Standards for Aircraft Engines
    1. Applicability of Standards

[[Page 6325]]

    2. New Type nvPM Number Numerical Emission Limits for Aircraft 
Engines
    3. In Production nvPM Number Numerical Emission Limits for 
Aircraft Engines
    4. Graphical representation of nvPM Number Numerical Emission 
Limits
    C. PM Mass Concentration Standard for Aircraft Engines
    1. PM Mass Concentration Standard
    2. Graphical Representation of nvPM Mass Concentration Numerical 
Emission Limit
    D. Test and Measurement Procedures
    1. Aircraft Engine PM Emissions Metrics
    2. Test Procedure
    3. Test Duty Cycles
    4. Characteristic Level
    5. Derivative Engines for Emissions Certification Purposes
    E. Annual Reporting Requirement
V. Aggregate PM Inventory Impacts
    A. Aircraft Engine PM Emissions for Modeling
    1. Baseline PM Emission Indices
    2. Measured nvPM EIs for Inventory Modeling
    3. Improvements to Calculated EIs
    B. Baseline PM Emission Inventory
    C. Projected Reductions in PM Emissions
VI. Technological Feasibility and Economic Impacts
    A. Market Considerations
    B. Conceptual Framework for Technology
    C. Technological Feasibility
    D. Costs Associated With the Proposed Rule
    E. Summary of Benefits and Costs
VII. Technical Amendments
    A. Migration of Regulatory Text to New Part
    B. Deletion of Unnecessary Provisions
    C. Other Technical Amendments and Minor Changes
VIII. Statutory Authority and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution or Use
    I. National Technology Transfer and Advancement Act (NTTAA)
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Does this action apply to me?

    This proposed action would affect companies that design and or 
manufacture civil subsonic jet aircraft engines with a rated output of 
greater than 26.7 kN and those that design and or manufacturer civil 
jet engines for use on supersonic airplanes with a rated output at or 
below 26.7 kN. These affected entities include the following:

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                                                        Examples of
           Category              NAICS code \a\    potentially affected
                                                         entities
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Industry......................           336412   Manufacturers of new
                                                   aircraft engines.
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\a\ North American Industry Classification System (NAICS).

    This table lists the types of entities that EPA is now aware could 
potentially be affected by this action. Other types of entities not 
listed in the table could also be regulated. To determine whether your 
activities are regulated by this action, you should carefully examine 
the relevant applicability criteria in 40 CFR parts 87 and 1031. If you 
have any questions regarding the applicability of this action to a 
particular entity, consult the person listed in the preceding FOR 
FURTHER INFORMATION CONTACT section.
    For consistency purposes across the United States Code of Federal 
Regulations (CFR), common definitions for the words ``airplane,'' 
``aircraft,'' ``aircraft engine,'' and ``civil aircraft'' are found in 
Title 14 CFR part 1, and are used as appropriate throughout this new 
proposed regulation under 40 CFR parts 87 and 1031.

B. Executive Summary

1. Summary of the Major Provisions of the Proposed Regulatory Action
    The EPA is proposing to regulate PM emissions from covered aircraft 
engines through the adoption of domestic PM regulations that match the 
ICAO PM standards, which would be implemented and enforced in the U.S. 
The proposed standards would apply to new type design and in-production 
aircraft engines with rated output (maximum thrust available for 
takeoff) of greater than 26.7 kN used by civil subsonic jet airplanes: 
Those engines generally used in commercial passenger and freight 
aircraft, as well as larger business jets. The EPA is proposing to 
adopt three different forms of PM standards: A PM mass standard in 
milligrams per kilonewton (mg/kN), a PM number standard in number of 
particles per kilonewton (#/kN), and a PM mass concentration standard 
in micrograms per cubic meter ([mu]g/m\3\). The applicable dates and 
coverage of these standards would vary, as described in the following 
paragraphs, and more fully in in IV.A, IV.B, and IV.C respectively.
    First, the EPA is proposing PM engine emissions standards, in the 
form of both PM mass (mg/kN) and PM number (#/kN), for new type designs 
and in-production aircraft turbofan and turbojet engines with rated 
output greater than 26.7 kN. The proposed standards for in-production 
engines would apply to those engines that would be manufactured on or 
after January 1, 2023, even if type certificated before that date. The 
proposed standards for new type designs would apply to those engines 
whose initial type certification application was submitted on or after 
January 1, 2023. The in-production standards would have different 
emission levels limits than would the standards for new type designs. 
The different emission levels limits for new type designs and in-
production engines would depend on the rated output of the engines. 
Compliance with the proposed PM mass and number standards would be done 
in accordance with the standard landing and take-off (LTO) test cycle, 
which is currently used for demonstrating compliance with gaseous 
emission standards (oxides of nitrogen (NOX), hydrocarbons 
(HC), and carbon monoxide (CO) standards) for the covered engines.
    Second, the EPA is proposing a PM engine emissions standard in the 
form of maximum mass concentration ([mu]g/m\3\) for in-production 
aircraft turbofan and turbojet engines with rated output greater than 
26.7 kN manufactured on or after January 1, 2023.\1\ Compliance with 
the PM mass concentration standard would be done using the same test 
data that is developed to demonstrate compliance with the LTO-based PM 
mass and number standards. The proposed PM mass concentration standard 
would apply to the highest concentration of PM measured across the 
engine operating thrust range, not

[[Page 6326]]

just at one of the four LTO thrust settings.
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    \1\ The implementation date for ICAO's PM maximum mass 
concentration standards is on or after January 1, 2020. The final 
rulemaking that would follow this proposed rulemaking for these 
standards is expected to be completed before January 1, 2023. Thus, 
the standards would have an implementation date of January 1, 2023 
(instead of January 1, 2020).
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    The proposed PM mass concentration standard was developed by ICAO 
to provide, through a PM mass measurement, the equivalent smoke opacity 
or visibility control as afforded by the existing smoke number standard 
for the covered engines. Thus, the EPA is also proposing to no longer 
apply the existing smoke number standard for new engines that would be 
subject to the proposed PM mass concentration standard after January 1, 
2023, but the EPA is maintaining smoke number standards for new engines 
not covered by the PM mass concentration standard (e.g., in-production 
aircraft turbofan and turbojet engines with rated output less than or 
equal to 26.7 kN) and for engines already manufactured. This proposed 
approach would essentially change the existing standard for covered 
engines from being based on a smoke measurement to a PM measurement.
    Third, the EPA is proposing testing and measurement procedures for 
the PM emission standards and various updates to the existing gaseous 
exhaust emissions test procedures. These proposed test procedure 
provisions would implement the recent additions and amendments to 
ICAO's regulations, which are codified in ICAO Annex 16, Volume II. As 
we have historically done, we propose to incorporate these test 
procedure additions and amendments to the ICAO Annex 16, Volume II into 
our regulations by reference.
    The proposed aircraft engine PM standards, test procedures and 
associated regulatory requirements are equivalent to the international 
PM standards and test procedures adopted by ICAO in 2017 and 2020 and 
promulgated in Annex 16, Volume II.\2\ The United States and other 
member States of ICAO, as well as the world's aircraft engine 
manufacturers and other interested stakeholders, participated in the 
deliberations leading up to ICAO's adoption of the international 
aircraft engine PM emission standards.
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    \2\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017. Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed 
November 15, 2021). The ICAO Annex 16 Volume II is found on page 17 
of the ICAO Products & Services Catalog, English Edition of the 2021 
catalog, and it is copyright protected; Order No. AN16-2. The ICAO 
Annex 16, Volume II, Fourth Edition, includes Amendment 10 of 
January 1, 2021. Amendment 10 is also found on page 17 of this ICAO 
catalog, and it is copyright protected; Order No. AN 16-2/E/12.
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    In addition to the PM standards just discussed, the EPA is 
proposing to migrate the existing aircraft engine emissions regulations 
from 40 CFR part 87 to a new 40 CFR part 1031, and all the aircraft 
engine standards and requirements described earlier would be specified 
in this new part 1031. Along with this migration, the EPA is proposing 
to restructure the regulations to allow for better ease of use and 
allow for more efficient future updates. The EPA is also proposing to 
delete some unnecessary definitions and regulatory provisions. Finally, 
the EPA is proposing several other minor technical amendments to the 
regulations, including applying smoke number standards to engines of 
less than or equal to 26.7 kilonewtons (kN) rated output used in 
supersonic airplanes.
2. Purpose of the Proposed Regulatory Action
    In developing these proposed standards, the EPA took into 
consideration the importance of both controlling PM emissions and 
international harmonization of aviation requirements. In addition, the 
EPA gave significant weight to the U.S.'s treaty obligations under the 
Chicago Convention, as discussed in Section II.B, in determining the 
need for and appropriate levels of PM standards. These considerations 
led the EPA to propose standards for PM emissions from certain classes 
of covered aircraft engines that are equivalent in scope, stringency, 
and effective date to the PM standards adopted by ICAO.
    The new ICAO aircraft PM emission standards will take effect on 
January 1, 2023 but will not apply in the U.S. unless adopted into 
domestic law. One of the core functions of ICAO is to adopt Standards 
and Recommended Practices on a wide range of aviation-related matters, 
including aircraft emissions. As a member State of ICAO, the United 
States actively participates in the development of new environmental 
standards, within ICAO's Committee on Aviation Environmental Protection 
(CAEP), including the PM standards adopted by ICAO in both 2017 and 
2020. Due to the international nature of the aviation industry, there 
is an advantage to working within ICAO, in order to secure the highest 
practicable degree of uniformity in international aviation regulations 
and standards. Uniformity in international aviation regulations and 
standards is a goal of the Chicago Convention, because it ensures that 
passengers and the public can expect similar levels of protection for 
safety and human health and the environment regardless of manufacturer, 
airline, or point of origin of a flight. Further, it helps reduce 
barriers in the global aviation market, benefiting both U.S. aircraft 
engine manufacturers and consumers.
    When developing new emissions standards, ICAO/CAEP seeks to capture 
the technological advances made in the control of emissions through the 
adoption of anti-backsliding standards reflecting the current state of 
technology. The PM standards the EPA is proposing were developed using 
this approach. Thus, the adoption of these aviation standards into U.S. 
law would simultaneously prevent aircraft engine PM levels from 
increasing beyond their current levels, align U.S. domestic standards 
with the ICAO standards for international harmonization, and help the 
U.S. meet its treaty obligations under the Chicago Convention.
    These proposed standards would also allow U.S. manufacturers of 
covered aircraft engines to remain competitive in the global 
marketplace (as described later in the introductory text of Section 
IV). In the absence of U.S. standards implementing the ICAO aircraft 
engine PM emission standards, U.S. civil aircraft engine manufacturers 
could be forced to seek PM emissions certification from an aviation 
certification authority of another country (not the FAA) in order to 
market and operate their aircraft engines internationally. U.S. 
manufacturers could be at a significant disadvantage if the U.S. fails 
to adopt standards that are at least as stringent as the ICAO standards 
for PM emissions. The ICAO aircraft engine PM emission standards have 
been or are being adopted by other ICAO member states that certify 
aircraft engines. The proposed action to adopt in the U.S. PM standards 
that match the ICAO standards would help ensure international 
consistency and acceptance of U.S. manufactured engines worldwide.
3. Environmental Justice
    Executive Orders 12898 (59 FR 7629, February 16, 1994) and 14008 
(86 FR 7619, February 1, 2021) direct federal agencies, to the greatest 
extent practicable and permitted by law, to make achieving 
environmental justice (EJ) part of their mission by identifying and 
addressing, as appropriate, disproportionately high and adverse human 
health or environmental effects of their programs, policies, and 
activities on minority populations and low-income populations in the 
United States. Section III.G discusses these executive orders in 
greater detail, along with the potential environmental justice concerns 
associated with exposure to aircraft PM near airports. EPA defines 
environmental justice as the fair

[[Page 6327]]

treatment and meaningful involvement of all people regardless of race, 
color, national origin, or income with respect to the development, 
implementation, and enforcement of environmental laws, regulations, and 
policies.
    Studies have reported that many communities in close proximity to 
airports are disproportionately represented by people of color and low-
income populations (as described later in Section III.G). In an action 
separate from this proposed rulemaking, EPA will be conducting an 
analysis of the communities residing near airports where jet aircraft 
operate in order to more fully understand disproportionately high and 
adverse human health or environmental effects on people of color, low-
income populations and/or indigenous peoples. The results of this 
analysis could help inform additional policies to reduce pollution in 
communities living in close proximity to airports.
    As described in Section V.C, while newer aircraft engines typically 
have significantly lower emissions than existing aircraft engines, the 
proposed standards in this action are technology-following in order to 
align with ICAO's standards and are not expected to, in and of 
themselves, result in further reductions in PM from these engines. 
Therefore, we do not anticipate an improvement in air quality for those 
who live near airports where these aircraft operate.

II. Introduction: Context for This Proposed Action

    EPA has been regulating PM emissions from aircraft engines since 
the 1970s when the first smoke number standards were adopted. This 
section provides context for the proposed rule, which proposes three PM 
standards for aircraft engines. This section includes a description of 
EPA's statutory authority, the United States' role in ICAO and 
developing international emission standards, and the relationship 
between United States' standards and ICAO's international standards.

A. EPA Statutory Authority and Responsibilities Under the Clean Air Act

    Section 231(a)(2)(A) of the Clean Air Act (CAA) directs the 
Administrator of EPA to, from time to time, propose aircraft engine 
emission standards applicable to the emission of any air pollutant from 
classes of aircraft engines which in his or her judgment causes or 
contributes to air pollution that may reasonably be anticipated to 
endanger public health or welfare. (See 42 U.S.C. 7571(a)(2)(A)). CAA 
section 231(a)(2)(B) directs the EPA to consult with the Administrator 
of the Federal Aviation Administration (FAA) on such standards, and it 
prohibits the EPA from changing aircraft emission standards if such a 
change would significantly increase noise and adversely affect safety. 
(See 42 U.S.C. 7571(a)(2)(B)(i)-(ii)). CAA section 231(a)(3) provides 
that after we provide notice and an opportunity for a public hearing on 
standards, the Administrator shall issue such standards ``with such 
modifications as he deems appropriate.'' (See 42 U.S.C. 7571(a)(3)). In 
addition, under CAA section 231(b) the EPA is required to ensure, in 
consultation with the U.S. Department of Transportation (DOT), that the 
effective date of any standard provides the necessary time to permit 
the development and application of the requisite technology, giving 
appropriate consideration to the cost of compliance. (See 42 U.S.C. 
7571(b)).
    Consistent with its longstanding approach and D.C. Circuit 
precedent,\3\ the EPA interprets its authority under CAA section 231 as 
providing the Administrator wide discretion in determining what 
standards are appropriate, after consideration of the factors specified 
in the statute and other relevant factors, such as applicable 
international standards. We are not compelled under CAA section 231 to 
obtain the ``greatest degree of emission reduction achievable'' as per 
sections 213(a)(3) and 202(a)(3)(A) of the CAA, and so the EPA does not 
interpret the Act as requiring the agency to give subordinate status to 
factors such as cost, safety, and noise in determining what standards 
are reasonable for aircraft engines. Rather, the EPA has greater 
flexibility under section 231 in determining what standard is most 
reasonable for aircraft engines. Thus, as in past rulemakings, EPA 
notes its authority under the CAA to issue reasonable aircraft engine 
standards with either technology-following or technology-forcing 
results, provided that, in either scenario, the Agency has a reasonable 
basis after considering all the relevant factors for setting the 
standard.\4\ Once EPA adopts standards, CAA section 232 then directs 
the Secretary of Transportation to prescribe regulations to ensure 
compliance with the EPA's standards. (See 42 U.S.C. 7572). Finally, 
section 233 of the CAA vests the authority to promulgate emission 
standards for aircraft or aircraft engines only in the Federal 
Government. States are preempted from adopting or enforcing any 
standard respecting aircraft or aircraft engine emissions unless such 
standard is identical to the EPA's standards. (See 42 U.S.C. 7573).
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    \3\ The U.S. Court of Appeals for the D.C. Circuit has held that 
CAA section 231 confers an ``extraordinarily broad'' degree of 
discretion on EPA to ``weigh various factors'' and adopt aircraft 
engine emission standards as the Agency determines are reasonable. 
Nat'l Ass'n of Clean Air Agencies v. EPA, 489 F.3d 1221, 1229-30 
(D.C. Cir. 2007) (NACAA).
    \4\ See 70 FR 69664, 69676 (November 17, 2005).
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B. The Role of the United States in International Aircraft Agreements

    The Convention on International Civil Aviation (commonly known as 
the `Chicago Convention') was signed in 1944 at the Diplomatic 
Conference held in Chicago. It was ratified by the United States on 
August 9, 1946. The Chicago Convention establishes the legal framework 
for the development of international civil aviation. The primary 
objective is ``that international civil aviation may be developed in a 
safe and orderly manner and that international air transport services 
may be established on the basis of equality of opportunity and operated 
soundly and economically.'' \5\ In 1947, ICAO was established, and 
later in that same year, ICAO became a specialized agency of the United 
Nations (UN). ICAO sets international standards for aviation safety, 
security, efficiency, capacity, and environmental protection and serves 
as the forum for cooperation in all fields of international civil 
aviation. ICAO works with the Chicago Convention's member States and 
global aviation organizations to develop international Standards and 
Recommended Practices (SARPs), which member States reference when 
developing their domestic civil aviation regulations. The United States 
is one of 193 currently participating ICAO member States.6 7 
ICAO standards are not self-implementing. They must first be adopted 
into domestic law to be legally binding in any member State.
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    \5\ ICAO, 2006: Convention on International Civil Aviation, 
Ninth Edition, Document 7300/9. Available at: https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 20, 2021).
    \6\ Members of ICAO's Assembly are generally termed member 
States or contracting States. These terms are used interchangeably 
throughout this preamble.
    \7\ There are currently 193 contracting states according to 
ICAO's website: https://www.icao.int/MemberStates/Member%20States.English.pdf (last accessed July 12, 2021).
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    In the interest of global harmonization and international air 
commerce, the Chicago Convention urges its member States to 
``collaborate in securing the highest practicable degree of uniformity 
in regulations, standards, procedures and organization in relation to 
aircraft, [. . .] in all matters which such uniformity will facilitate 
and improve

[[Page 6328]]

air navigation.'' \8\ The Chicago Convention also recognizes that 
member States may adopt national standards that are more or less 
stringent than those agreed upon by ICAO or standards that are 
different in character or that comply with the ICAO standards by other 
means. Any member State that finds it impracticable to comply in all 
respects with any international standard or procedure, or that 
determines it is necessary to adopt regulations or practices differing 
in any particular respect from those established by an international 
standard, is required to give notification to ICAO of the differences 
between its own practice and that established by the international 
standard.\9\
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    \8\ ICAO, 2006: Convention on International Civil Aviation, 
Article 37, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 
20, 2021).
    \9\ ICAO, 2006: Doc 7300-Convention on International Civil 
Aviation, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 
20, 2021).
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    ICAO's work on the environment focuses primarily on those problems 
that benefit most from a common and coordinated approach on a worldwide 
basis, namely aircraft noise and engine emissions. SARPs for the 
certification of aircraft noise and aircraft engine emissions are 
covered by Annex 16 of the Chicago Convention. To continue to address 
aviation environmental issues, in 2004, ICAO established three 
environmental goals: (1) Limit or reduce the number of people affected 
by significant aircraft noise; (2) limit or reduce the impact of 
aviation emissions on local air quality; and (3) limit or reduce the 
impact of aviation greenhouse gas (GHG) emissions on the global 
climate.
    The Chicago Convention has a number of other features that govern 
international commerce. First, member States that wish to use aircraft 
in international transportation must adopt emission standards that are 
at least as stringent as ICAO's standards if they want to ensure 
recognition of their airworthiness certificates by other member States. 
Member States may ban the use of any aircraft within their airspace 
that does not meet ICAO standards.\10\ Second, the Chicago Convention 
indicates that member States are required to recognize the 
airworthiness certificates issued or rendered valid by the contracting 
State in which the aircraft is registered provided the requirements 
under which the certificates were issued are equal to or above ICAO's 
minimum standards.\11\ Third, to ensure that international commerce is 
not unreasonably constrained, a member State that cannot meet or deems 
it necessary to adopt regulations differing from the international 
standard is obligated to notify ICAO of the differences between its 
domestic regulations and ICAO standards.\12\
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    \10\ ICAO, 2006: Convention on International Civil Aviation, 
Article 33, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 
20, 2021).
    \11\ ICAO, 2006: Convention on International Civil Aviation, 
Article 33, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 
20, 2021).
    \12\ ICAO, 2006: Convention on International Civil Aviation, 
Article 38, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 
20, 2021).
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    ICAO's Committee on Aviation Environmental Protection (CAEP), which 
consists of members and observers from States, intergovernmental and 
non-governmental organizations representing the aviation industry and 
environmental interests, undertakes ICAO's technical work in the 
environmental field. The Committee is responsible for evaluating, 
researching, and recommending measures to the ICAO Council that address 
the environmental impacts of international civil aviation. CAEP's terms 
of reference indicate that ``CAEP's assessments and proposals are 
pursued taking into account: Technical feasibility; environmental 
benefit; economic reasonableness; interdependencies of measures (for 
example, among others, measures taken to minimize noise and emissions); 
developments in other fields; and international and national 
programs.'' \13\ The ICAO Council reviews and adopts the 
recommendations made by CAEP. It then reports to the ICAO Assembly, the 
highest body of the organization, where the main policies on aviation 
environmental protection are adopted and translated into Assembly 
Resolutions. If ICAO adopts a CAEP proposal for a new environmental 
standard, it then becomes part of ICAO standards and recommended 
practices (Annex 16 to the Chicago Convention).\14\ \15\
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    \13\ ICAO: CAEP Terms of Reference. Available at https://www.icao.int/environmental-protection/Pages/Caep.aspx#ToR (last 
accessed July 20, 2021).
    \14\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017. Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed 
November 15, 2021). The ICAO Annex 16 Volume II is found on page 17 
of the ICAO Products & Services English Edition of the 2021 catalog, 
and it is copyright protected; Order No. AN16-2. The ICAO Annex 16, 
Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021. 
Amendment 10 is also found on page 17 of this ICAO catalog, and it 
is copyright protected; Order No. AN 16-2/E/12.
    \15\ CAEP develops new emission standards based on an assessment 
of the technical feasibility, cost, and environmental benefit of 
potential requirements.
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    The FAA plays an active role in ICAO/CAEP, including serving as the 
representative (member) of the United States at annual ICAO/CAEP 
Steering Group meetings, as well as the ICAO/CAEP triennial meetings, 
and contributing technical expertise to CAEP's working groups. The EPA 
serves as an advisor to the U.S. member at the annual ICAO/CAEP 
Steering Group and triennial ICAO/CAEP meetings, while also 
contributing technical expertise to CAEP's working groups and assisting 
and advising the FAA on aviation emissions, technology, and 
environmental policy matters. In turn, the FAA assists and advises the 
EPA on aviation environmental issues, technology, and airworthiness 
certification matters.
    CAEP's predecessor at ICAO, the Committee on Aircraft Engine 
Emissions (CAEE), adopted the first international SARPs for aircraft 
engine emissions which were proposed in 1981.\16\ These standards 
limited aircraft engine emissions of hydrocarbons (HC), carbon monoxide 
(CO), and oxides of nitrogen (NOX). The 1981 standards 
applied to newly manufactured engines, which are those engines 
manufactured after the effective date of the regulations--also referred 
to as in-production engines. In 1993, ICAO adopted a CAEP/2 proposal to 
tighten the original NOX standard by 20 percent and amend 
the test procedures.\17\ These 1993 standards applied both to newly 
certificated turbofan engines (those engine models that received their 
initial type certificate after the effective date of the

[[Page 6329]]

regulations, also referred to as new type design engines) and to in-
production engines; the standards had different effective dates for 
newly certificated engines and in-production engines. In 1995, CAEP/3 
recommended a further tightening of the NOX standards by 16 
percent and additional test procedure amendments, but in 1997 the ICAO 
Council rejected this stringency proposal and approved only the test 
procedure amendments. At the CAEP/4 meeting in 1998, the Committee 
adopted a similar 16 percent NOX reduction proposal, which 
ICAO approved in 1998. Unlike the CAEP/2 standards, the CAEP/4 
standards applied only to new type design engines after December 31, 
2003, and not to in-production engines, leaving the CAEP/2 standards 
applicable to in-production engines. In 2004, CAEP/6 recommended a 12 
percent NOX reduction, which ICAO approved in 2005.\18\ \19\ 
The CAEP/6 standards applied to new engine designs certificated after 
December 31, 2007, again leaving the CAEP/2 standards in place for in-
production engines before January 1, 2013. In 2010, CAEP/8 recommended 
a further tightening of the NOX standards by 15 percent for 
new engine designs certificated after December 31, 2013.\20\ \21\ The 
Committee also recommended that the CAEP/6 standards be applied to in-
production engines on or after January 1, 2013, which cut off the 
production of CAEP/2 and CAEP/4 compliant engines with the exception of 
spare engines; ICAO adopted these as standards in 2011.\22\
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    \16\ ICAO, 2017: Aircraft Engine Emissions: Foreword, 
International Standards and Recommended Practices, Environmental 
Protection, Annex 16, Volume II, Fourth Edition, July 2017. 
Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed November 15, 2021). The ICAO Annex 16 
Volume II is found on page 17 of the ICAO Products & Services 
English Edition 2021 catalog and is copyright protected; Order No. 
AN16-2. The ICAO Annex 16, Volume II, Fourth Edition, includes 
Amendment 10 of January 1, 2021. Amendment 10 is also found on page 
17 of this ICAO catalog, and it is copyright protected; Order No. AN 
16-2/E/12.
    \17\ CAEP conducts its work triennially. Each 3-year work cycle 
is numbered sequentially and that identifier is used to 
differentiate the results from one CAEP meeting to another by 
convention. The first technical meeting on aircraft emission 
standards was CAEP's predecessor, i.e., CAEE. The first meeting of 
CAEP, therefore, is referred to as CAEP/2.
    \18\ CAEP/5 did not address new aircraft engine emission 
standards.
    \19\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017. Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed 
June 16, 2021). The ICAO Annex 16 Volume II is found on page 17 of 
the ICAO Products & Services Catalog, English Edition of the 2021 
catalog, and it is copyright protected; Order No. AN16-2. The ICAO 
Annex 16, Volume II, Fourth Edition, includes Amendment 10 of 
January 1, 2021. Amendment 10 is also found on page 17 of this ICAO 
catalog, and it is copyright protected; Order No. AN 16-2/E/12.
    \20\ CAEP/7 did not address new aircraft engine emission 
standards.
    \21\ ICAO, 2010: Committee on Aviation Environmental Protection 
(CAEP), Report of the Eighth Meeting, Montreal, February 1-12, 2010, 
CAEP/8-WP/80 Available in Docket EPA-HQ-OAR-2010-0687.
    \22\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, Amendment 10. CAEP/8 
corresponds to Amendment 7 effective on July 18, 2011. Available at 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on 
page 17 of the ICAO Products & Services Catalog, English Edition of 
the 2021 catalog, and it is copyright protected; Order No. AN16-2. 
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 
of January 1, 2021. Amendment 10 is also found on page 17 of this 
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
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    At the CAEP/10 meeting in 2016, the Committee agreed to the first 
airplane CO2 emission standards, which ICAO approved in 
2017. The CAEP/10 CO2 standards apply to new type design 
airplanes for which the application for a type certificate will be 
submitted on or after January 1, 2020, some modified in-production 
airplanes on or after January 1, 2023, and all applicable in-production 
airplanes manufactured on or after January 1, 2028.
    At the CAEP/10 and CAEP/11 meetings in 2016 and 2019, the Committee 
agreed to three different forms of international PM standards for 
aircraft engines. Maximum PM mass concentration standards were agreed 
to at CAEP/10, and PM mass and number standards were agreed to at CAEP/
11. ICAO adopted the PM maximum mass concentration standards in 2017 
and the PM mass and number standards in 2020. The CAEP/10 PM standards 
apply to in-production engines on or after January 1, 2020, and the 
CAEP/11 PM standards apply to new-type and in-production engines on or 
after January 1, 2023. In addition to CAEP/10 agreeing to a maximum PM 
mass concentration standard, CAEP/10 adopted a reporting requirement 
where aircraft engine manufacturers were required to provide PM mass 
concentration, PM mass, and PM number emissions data--and other related 
parameters--by January 1, 2020 for in-production engines.\23\
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    \23\ More specifically, the international PM standard applies to 
all turbofan and turbojet engines of a type or model, and their 
derivative versions, with a rated output greater than 26.7 kN and 
whose date of manufacture of the individual engine is on or after 
January 1, 2020 (or those engines manufactured on or after January 
1, 2020).
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C. The Relationship Between EPA's Regulation of Aircraft Engine 
Emissions and International Standards

    Domestically, as required by the CAA, the EPA has been engaged in 
reducing harmful air pollution from aircraft engines for over 40 years, 
regulating gaseous exhaust emissions, smoke, and fuel venting from 
engines.\24\ We have periodically revised these regulations.\25\ The 
EPA's actions to regulate certain pollutants emitted from aircraft 
engines come directly from the authority in section 231 of the CAA, and 
we have aligned the U.S. emissions requirements with those promulgated 
by ICAO. As described above in Section II.B, the ICAO/CAEP terms of 
reference includes technical feasibility.\26\ Technical feasibility has 
been interpreted by CAEP as technology demonstrated to be safe and 
airworthy and available for application over a sufficient range of 
newly certificated aircraft.\27\ This interpretation resulted in all 
previous ICAO emission standards, and the EPA's standards reflecting 
them, being anti-backsliding standards (i.e., the standards would not 
reduce aircraft PM emissions below current levels of engine emissions), 
which are technology following.
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    \24\ U.S. EPA, 1973: Emission Standards and Test Procedures for 
Aircraft; Final Rule, 38 FR 19088 (July 17, 1973).
    \25\ The following are the most recent EPA rulemakings that 
revised these regulations. U.S. EPA, 1997: Control of Air Pollution 
from Aircraft and Aircraft Engines; Emission Standards and Test 
Procedures; Final Rule, 62 FR 25355 (May 8, 1997). U.S. EPA, 2005: 
Control of Air Pollution from Aircraft and Aircraft Engines; 
Emission Standards and Test Procedures; Final Rule, 70 FR 69664 
(November 17, 2005). U.S. EPA, 2012: Control of Air Pollution from 
Aircraft and Aircraft Engines; Emission Standards and Test 
Procedures; Final Rule, 77 FR 36342 (June 18, 2012). U.S. EPA, 2021: 
Control of Air Pollution From Airplanes and Airplane Engines: GHG 
Emission Standards and Test Procedures; Final Rule, 86 FR 2136 
(January 11, 2021).
    \26\ ICAO: CAEP Terms of Reference. Available at https://www.icao.int/environmental-protection/Pages/Caep.aspx#ToR (last 
accessed July 20, 2021).
    \27\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP11. It is found on page 26 of the English 
Edition of the ICAO Products & Services 2021 Catalog and is 
copyright protected: Order No. 10126. For purchase and available at: 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed June 21, 2021). The statement on technological feasibility 
is located in Appendix C of Agenda Item 3 of this report (see page 
3C-4, paragraph 2.2).
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    For many years the EPA has regulated aircraft engine PM emissions 
through the use of smoke number standards.\28\ Since setting the 
original smoke number standards in 1973, the EPA has periodically 
revised these standards. The EPA amended its smoke standards to align 
with ICAO's smoke standards in 1982 \29\ and again in 1984.\30\ 
Additionally, EPA has amended the test procedures for measuring smoke

[[Page 6330]]

emissions \31\ and modified the effective dates and compliance schedule 
for smoke emissions standards periodically.\32\ Now, we are proposing 
to adopt three different forms of aircraft engine PM standards: A PM 
mass concentration standard ([mu]g/m\3\), a PM mass standard (mg/kN), 
and PM number standard (#/kN). These proposed aircraft engine PM 
emission standards are a different way of regulating and/or measuring 
\33\ aircraft engine PM emissions in comparison to smoke number 
emission standards.
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    \28\ U.S. EPA, 40 CFR 87.1. ``Smoke means the matter in exhaust 
emissions that obscures the transmission of light, as measured by 
the test procedures specified in subpart G of this part.'' ``Smoke 
number means a dimensionless value quantifying smoke emission as 
calculated according to ICAO Annex 16.''
    \29\ U.S. EPA, Control of Air Pollution From Aircraft and 
Aircraft Engines; Emission Standards and Test Procedures, Final 
Rule, 47 FR 58462, December 30, 1982.
    \30\ U.S. EPA, Control of Air Pollution From Aircraft and 
Aircraft Engines; Smoke Emission Standard, Final Rule, 49 FR 31873, 
August 9, 1984 (bifurcating EPA's smoke standard for new engines 
into two regimes--one for engines with rated output less than 26.7 
kilonewtons and one for engines with rated output equal to or 
greater than 26.7 kilonewtons).
    \31\ U.S. EPA, Control of Air Pollution From Aircraft and 
Aircraft Engines; Emission Standards and Test Procedures, Final 
Rule, 62 FR 25356, May 8, 1997 (harmonizing EPA procedures with 
recent amendments to ICAO test procedures); U.S. EPA, Control of Air 
Pollution From Aircraft and Aircraft Engines; Emission Standards and 
Test Procedures, Final Rule, 70 FR 69664, November 17, 2005 (same); 
U.S. EPA, Control of Air Pollution From Aircraft and Aircraft 
Engines; Emission Standards and Test Procedures, Final Rule, 77 FR 
36342, June 18, 2012.
    \32\ U.S. EPA, Amendment to Standards, Final Rule, 43 FR 12614, 
March 24, 1978 (setting back by two years the effective date for all 
gaseous emissions standards for newly manufactured aircraft and 
aircraft gas turbine engines); U.S. EPA, Control of Air Pollution 
from Aircraft and Aircraft Engines; Extension of Compliance Date for 
Emission Standards Applicable to JT3D Engines, Final Rule, 44 FR 
64266, November 6, 1979 (extending the final compliance date for 
smoke emission standards applicable to the JT3D aircraft engines by 
roughly 3.5 years); U.S. EPA, Control of Air Pollution from 
Aircraft; Amendment to Standards, Final Rule, 45 FR 86946, December 
31, 1980 (setting back by two years the effective date for all 
gaseous emissions standards which would otherwise have been 
effective on January 1,1981, for aircraft gas turbine engines); U.S. 
EPA, Control of Air Pollution from Aircraft and Aircraft Engines, 
Final Rule, 46 FR 2044, January 8, 1981 (extending the applicability 
of the temporary exemption provision of the standards for smoke and 
fuel venting emissions from some in-use aircraft engines); U.S. EPA, 
Control of Air Pollution From Aircraft and Aircraft Engines; Smoke 
Emission Standard, Final Rule, 48 FR 46481, October 12, 1983 
(staying the smoke regulations for new turbojet and turbofan engines 
rated below 26.7 kN thrust).
    \33\ Also, as described in Section IV.D, the proposed PM 
standards employ a different method for measuring aircraft engine PM 
emissions compared to the historical smoke number emission 
standards.
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    Internationally, the EPA and the FAA have worked within the 
standard-setting process of ICAO (CAEP and its predecessor, CAEE) since 
the 1970's to help establish international emission standards and 
related requirements, which individual member States adopt into 
domestic law and regulations. Historically, under this approach, 
international emission standards have first been adopted by ICAO, and 
subsequently the EPA has initiated rulemakings under CAA section 231 to 
establish domestic standards that are harmonized with ICAO's standards. 
After EPA promulgates aircraft engine emission standards, CAA section 
232 requires the FAA to issue regulations to ensure compliance with the 
EPA aircraft engine emission standards when certificating aircraft 
pursuant to its authority under Title 49 of the United States Code. 
This proposed rule would continue this historical rulemaking approach.
    The EPA and FAA worked from 2009 to 2019 within the ICAO/CAEP 
standard setting process on the development of the three different 
forms of international aircraft engine PM emission standards (a PM mass 
concentration standard, a PM mass standard, and a PM particle number 
standard). In this action, we are proposing to adopt PM standards 
equivalent to ICAO's three different forms of aircraft engine PM 
emission standards. Adoption of the proposed standards would meet the 
United States' obligations under the Chicago Convention and would also 
ensure global acceptance of FAA airworthiness certification.
    In December 2018, the EPA issued an information collection request 
(ICR) that matches the CAEP/10 p.m. reporting requirements described 
earlier.\34\ In addition to the PM standards, the proposed rulemaking 
would codify the reporting requirements implemented by this 2018 EPA 
ICR into the EPA regulations, as described later in Section IV.E. Also, 
in a similar time frame as this proposed rulemaking, EPA will be 
renewing this ICR (the ICR needs to be renewed triennially).
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    \34\ 83 FR 44621, August 31, 2018. U.S. EPA, Aircraft Engines--
Supplemental Information Related to Exhaust Emissions (Renewal), OMB 
Control Number 2060-0680, ICR Reference Number 201809-2060-08, 
December 17, 2018.
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III. Particulate Matter Impacts on Air Quality and Health

A. Background on Particulate Matter

    Particulate matter (PM) is a highly complex mixture of solid 
particles and liquid droplets distributed among numerous atmospheric 
gases which interact with solid and liquid phases. Particles range in 
size from those smaller than 1 nanometer (10-9 meter) to 
over 100 micrometers ([mu]m, or 10-6 meter) in diameter (for 
reference, a typical strand of human hair is 70 [mu]m in diameter and a 
grain of salt is about 100 [mu]m). Atmospheric particles can be grouped 
into several classes according to their aerodynamic and physical sizes. 
Generally, the three broad classes of particles include ultrafine 
particles (UFPs, generally considered as particulates with a diameter 
less than or equal to 0.1 [mu]m (typically based on physical size, 
thermal diffusivity or electrical mobility)), ``fine'' particles 
(PM2.5; particles with a nominal mean aerodynamic diameter 
less than or equal to 2.5 [mu]m), and ``thoracic'' particles 
(PM10; particles with a nominal mean aerodynamic diameter 
less than or equal to 10 [mu]m). Particles that fall within the size 
range between PM2.5 and PM10, are referred to as 
``thoracic coarse particles'' (PM10-2.5, particles with a 
nominal mean aerodynamic diameter less than or equal to 10 [mu]m and 
greater than 2.5 [mu]m).
    Particles span many sizes and shapes and may consist of hundreds of 
different chemicals. Particles are emitted directly from sources and 
are also formed through atmospheric chemical reactions between PM 
precursors; the former are often referred to as ``primary'' particles, 
and the latter as ``secondary'' particles. Particle concentration and 
composition varies by time of year and location, and, in addition to 
differences in source emissions, is affected by several weather-related 
factors, such as temperature, clouds, humidity, and wind. Ambient 
levels of PM are also impacted by particles' ability to shift between 
solid/liquid and gaseous phases, which is influenced by concentration, 
meteorology, and especially temperature.
    Fine particles are produced primarily by combustion processes and 
by transformations of gaseous emissions (e.g., sulfur oxides 
(SOX), nitrogen oxides (NOX) and volatile organic 
compounds (VOCs)) in the atmosphere. The chemical and physical 
properties of PM2.5 may vary greatly with time, region, 
meteorology, and source category. Thus, PM2.5 may include a 
complex mixture of different components including sulfates, nitrates, 
organic compounds, elemental carbon, and metal compounds. These 
particles can remain in the atmosphere for days to weeks and travel 
through the atmosphere hundreds to thousands of kilometers.
    Particulate matter is comprised of both volatile and non-volatile 
PM. PM emitted from the engine is known as non-volatile PM (nvPM), and 
PM formed from transformation of an engine's gaseous emissions are 
defined as volatile PM.\35\ Because of the

[[Page 6331]]

difficulty in measuring volatile PM, which is formed in the engine's 
exhaust plume and is significantly influenced by ambient conditions, 
the EPA is proposing standards only for the emission of nvPM.
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    \35\ The ICAO 2019 Environmental Report, Available at https://www.icao.int/environmental-protection/Documents/ICAO-ENV-Report2019-F1-WEB%20(1).pdf (last accessed September 1, 2021). See pages 98, 
100, and 101 for a description of non-volatile PM and volatile PM.
     ``During the combustion of hydrocarbon-based fuels, aircraft 
engines generate gaseous and particulate matter (PM) emissions. At 
the engine exhaust, particulate emissions consist mainly of 
ultrafine soot or black carbon emissions. These particles, referred 
to as ``non-volatile'' PM (nvPM), are present at high temperatures, 
in the engine exhaust. Compared to conventional diesel engines, gas 
turbine engines emit non-volatile particles of smaller mean 
diameter. Their characteristic size ranges roughly from 15 to 60 
nanometers (nm; 1nm = 1/100,000 of a millimeter). These particles 
are invisible to the human eye and are ultrafine.'' (See page 98.)
    ``Additionally, gaseous emissions from engines can also condense 
to produce new particles (i.e., volatile particulate matter--vPM) or 
coat the emitted soot particles. Gaseous emissions species react 
chemically with ambient chemical constituents in the atmosphere to 
produce the so called secondary particulate matter. Volatile 
particulate matter is dependent on these gaseous precursor 
emissions. While these precursors are controlled by gaseous emission 
certification and the fuel composition (e.g., sulfur content) for 
aircraft gas turbine engines, the volatile particulate matter is 
also dependent on the ambient air background composition.'' (See 
pages 100 and 101.)
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B. Health Effects of Particulate Matter

    Scientific studies show exposure to ambient PM is associated with a 
broad range of health effects. These health effects are discussed in 
detail in the Integrated Science Assessment for Particulate Matter (PM 
ISA), which was finalized in December 2019.\36\ The PM ISA concludes 
that human exposures to ambient PM2.5 are associated with a 
number of adverse health effects and characterizes the weight of 
evidence for broad health categories (e.g., cardiovascular effects, 
respiratory effects, etc.).\37\ The PM ISA additionally notes that 
stratified analyses (i.e., analyses that directly compare PM-related 
health effects across groups) provide strong evidence for racial and 
ethnic differences in PM2.5 exposures and in 
PM2.5-related health risk. As described in Section III.D, 
concentrations of PM increase with proximity to an airport. Further, 
studies described in Section III.G report that many communities in 
close proximity to airports are disproportionately represented by 
people of color and low-income populations.
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    \36\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \37\ The causal framework draws upon the assessment and 
integration of evidence from across epidemiological, controlled 
human exposure, and toxicological studies, and the related 
uncertainties that ultimately influence our understanding of the 
evidence. This framework employs a five-level hierarchy that 
classifies the overall weight of evidence and causality using the 
following categorizations: Causal relationship, likely to be causal 
relationship, suggestive of a causal relationship, inadequate to 
infer a causal relationship, and not likely to be a causal 
relationship (U.S. EPA. (2009). Integrated Science Assessment for 
Particulate Matter (Final Report). U.S. Environmental Protection 
Agency, Washington, DC, EPA/600/R-08/139F, Table 1-3).
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    EPA has concluded that recent evidence in combination with evidence 
evaluated in the 2009 p.m. ISA supports a ``causal relationship'' 
between both long- and short-term exposures to PM2.5 and 
mortality and cardiovascular effects and a ``likely to be causal 
relationship'' between long- and short-term PM2.5 exposures 
and respiratory effects.\38\ Additionally, recent experimental and 
epidemiologic studies provide evidence supporting a ``likely to be 
causal relationship'' between long-term PM2.5 exposure and 
nervous system effects, and long-term PM2.5 exposure and 
cancer. In addition, EPA noted that there was more limited and 
uncertain evidence for long-term PM2.5 exposure and 
reproductive and developmental effects (i.e., male/female reproduction 
and fertility; pregnancy and birth outcomes), long- and short-term 
exposures and metabolic effects, and short-term exposure and nervous 
system effects resulting in the ISA concluding ``suggestive of, but not 
sufficient to infer, a causal relationship.''
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    \38\ Short term exposures are usually defined as less than 24 
hours duration.
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    More detailed information on the health effects of PM can be found 
in a memorandum to the docket.\39\
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    \39\ Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660, 
``Health and environmental effects of non-GHG pollutants emitted by 
turbine engine aircraft,'' August 23, 2021.
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C. Environmental Effects of Particulate Matter

    Environmental effects that can result from particulate matter 
emissions include visibility degradation, plant and ecosystem effects, 
deposition effects, and materials damage and soiling. These effects are 
briefly summarized here and discussed in more detail in the memo to the 
docket cited above.
    PM2.5 emissions also adversely impact visibility.\40\ In 
the Clean Air Act Amendments of 1977, Congress recognized visibility's 
value to society by establishing a national goal to protect national 
parks and wilderness areas from visibility impairment caused by manmade 
pollution.\41\ In 1999, EPA finalized the regional haze program (64 FR 
35714) to protect the visibility in Mandatory Class I Federal areas. 
There are 156 national parks, forests and wilderness areas categorized 
as Mandatory Class I Federal areas (62 FR 38680-38681, July 18, 1997). 
These areas are defined in CAA section 162 as those national parks 
exceeding 6,000 acres, wilderness areas and memorial parks exceeding 
5,000 acres, and all international parks which were in existence on 
August 7, 1977. EPA has also concluded that PM2.5 causes 
adverse effects on visibility in other areas that are not targeted by 
the Regional Haze Rule, such as urban areas, depending on 
PM2.5 concentrations and other factors such as dry chemical 
composition and relative humidity (i.e., an indicator of the water 
composition of the particles). EPA established the secondary 24-hour 
PM2.5 NAAQS in 1997 and has retained the standard in 
subsequent reviews.\42\ This standard is expected to provide protection 
against visibility effects through attainment of the existing secondary 
standards for PM2.5. EPA is reconsidering the 2020 decision, 
as announced on June 10, 2021.\43\
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    \40\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \41\ See Section 169(a) of the Clean Air Act.
    \42\ In the 2012 review of the PM NAAQS, the EPA eliminated the 
option for spatial averaging for the 24-hour PM2.5 
standard (78 FR 3086, January 15, 2013).
    \43\ https://www.epa.gov/newsreleases/epa-reexamine-health-standards-harmful-soot-previous-administration-left-unchanged.
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1. Deposition of Metallic and Organic Constituents of PM
    Several significant ecological effects are associated with 
deposition of chemical constituents of ambient PM such as metals and 
organics.\44\ Like all internal combustion engines, turbine engines 
covered by this rule may emit trace amounts of metals due to fuel 
contamination or engine wear. Ecological effects of PM include direct 
effects to metabolic processes of plant foliage; contribution to total 
metal loading resulting in alteration of soil biogeochemistry and 
microbiology, plant and animal growth and reproduction; and 
contribution to total organics loading resulting in bioaccumulation and 
biomagnification.
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    \44\ U.S. Environmental Protection Agency (U.S. EPA). 2018. 
Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides 
of Sulfur and Particulate Matter Ecological Criteria Second External 
Review Draft). EPA-600-R-18-097. Washington, DC. December. Available 
on the internet at https://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=340671.
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2. Materials Damage and Soiling
    Deposition of PM is associated with both physical damage (materials 
damage effects) and impaired aesthetic qualities (soiling effects). Wet 
and dry deposition of PM can physically affect materials, adding to the 
effects of natural weathering processes, by potentially promoting or 
accelerating the corrosion of metals, by degrading paints and by

[[Page 6332]]

deteriorating building materials such as stone, concrete and 
marble.\45\
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    \45\ U.S. Environmental Protection Agency (U.S. EPA). 2018. 
Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides 
of Sulfur and Particulate Matter Ecological Criteria Second External 
Review Draft). EPA-600-R-18-097. Washington, DC. December. Available 
on the internet at https://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=340671.
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D. Near-Source Impacts on Air Quality and Public Health

    Airport activity can adversely impact air quality in the vicinity 
of airports. Furthermore, these adverse impacts may disproportionately 
impact sensitive subpopulations. A recent study by Yim et al. (2015) 
assessed global, regional, and local health impacts of civil aviation 
emissions, using modeling tools that address environmental impacts at 
different spatial scales.\46\ The study attributed approximately 16,000 
premature deaths per year globally to global aviation emissions, with 
87 percent attributable to PM2.5. The study concludes that 
about a third of these mortalities are attributable to PM2.5 
exposures within 20 kilometers of an airport. Another study focused on 
the continental United States estimated 210 deaths per year 
attributable to PM2.5 from aircraft.\47\ While there are 
considerable uncertainties associated with such estimates, these 
results suggest that in addition to the contributions of 
PM2.5 emissions to regional air quality, impacts on public 
health of these emissions in the vicinity of airports are an important 
public health concern.
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    \46\ Yim, S.H.L., Lee, G.L., Lee, I.H., Allrogen, F., Ashok, A., 
Caiazzo, F., Eatham, S.D., Malina, R., Barrett, S. R.H. 2015. 
Global, regional, and local health impacts of civil aviation 
emissions. Environ. Res. Lett. 10: 034001. https://iopscience.iop.org/article/10.1088/1748-9326/10/3/034001.
    \47\ Brunelle-Yeung, E., Masek, T., Rojo, J., Levy, J., 
Arunachalam, S., Miller, S., Barrett, S., Kuhn, S., Waitz, I. 2014. 
Assessing the impact of aviation environmental policies on public 
health. Transport Policy 34: 21-28. https://www.sciencedirect.com/science/article/pii/S0967070X14000468?via%3Dihub.
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    A significant body of research has addressed pollutant levels and 
potential health effects in the vicinity of airports. Much of this 
research was synthesized in a 2015 report published by the Airport 
Cooperative Research Program (ACRP), conducted by the Transportation 
Research Board.\48\ The report concluded that PM2.5 
concentrations in and around airports vary considerably, ranging from 
``relatively low levels to those that are close to the NAAQS, and in 
some cases, exceeding the standards.'' \49\
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    \48\ Kim, B., Nakada, K., Wayson, R., Christie, S., Paling, C., 
Bennett, M., Raper, D., Raps, V., Levy, J., Roof, C. 2015. 
Understanding Airport Air Quality and Public Health Studies Related 
to Airports. Airport Cooperative Research Program, ACRP Report 135. 
https://trid.trb.org/view/1364659.
    \49\ Kim, B., Nakada, K., Wayson, R., Christie, S., Paling, C., 
Bennett, M., Raper, D., Raps, V., Levy, J., Roof, C. 2015. 
Understanding Airport Air Quality and Public Health Studies Related 
to Airports. Airport Cooperative Research Program, ACRP Report 135, 
p. 39. https://trid.trb.org/view/1364659.
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    Furthermore, the report states (p. 40) that ``existing studies 
indicate that ultrafine particle concentrations are highly elevated at 
an airport (i.e., near a runway) with particle counts that can be 
orders of magnitude higher than background with some persistence many 
meters downwind (e.g., 600 m). Finally, the report concludes that 
PM2.5 dominates overall health risks posed by airport 
emissions. Moreover, one recently published study concluded that 
emissions from aircraft play an etiologic role in pre-term births, 
independent of noise and traffic-related air pollution exposures.\50\
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    \50\ Wing, S.E., Larson, T.V., Hudda, N., Boonyarattaphan, S., 
Fruin, S., Ritz, B. 2020. Preterm birth among infants exposed to in 
utero ultrafine particles from aircraft emissions. Environ. Health 
Perspect. 128, https://doi.org/10.1289/EHP5732.
---------------------------------------------------------------------------

    Since the publication of the 2015 ACRP literature review, a number 
of studies conducted in the U. S. have been published which concluded 
that ultrafine particle number concentrations were elevated downwind of 
commercial airports, and that proximity to an airport also increased 
particle number concentrations within residences. Hudda et al. 
investigated ultrafine particle number concentrations (PNC) inside and 
outside 16 residences in the Boston metropolitan area. They found 
elevated outdoor PNC within several kilometers of the airport. They 
also found that aviation-related PNC infiltrated indoors and resulted 
in significantly higher indoor PNC.\51\ In another study in the 
vicinity of Logan airport, Hudda et al. analyzed PNC impacts of 
aviation activities.\52\ They found that, at sites 4.0 and 7.3 km from 
the airport, average PNCs were 2 and 1.33-fold higher, respectively, 
when winds were from the direction of the airport compared to other 
directions, indicating that aviation impacts on PNC extend many 
kilometers downwind of Logan airport. Stacey (2019) conducted a 
literature survey and concluded that the literature consistently 
reports that particle numbers close to airports are significantly 
higher than locations distant and upwind of airports, and that the 
particle size distribution is different from traditional road traffic, 
with more extremely fine particles.\53\ Similar findings have been 
published from European studies.54 55 56 57 58 59  Results 
of a monitoring study of communities near Seattle-Tacoma International 
Airport also found higher levels of ultrafine PM near the airport, and 
an impacted area larger than at near-roadway sites.\60\ The PM 
associated with aircraft landing activity was also smaller in size, 
with lower black carbon concentrations than near-roadway samples. As 
discussed above, PM2.5 exposures are associated with a 
number of serious, adverse health effects. Further, the PM attributable 
to aircraft emissions has been associated with potential adverse health 
impacts.61 62 For example, He et al.

[[Page 6333]]

(2018) found that particle composition, size distribution and 
internalized amount of particles near airports all contributed to 
promotion of reactive organic species in bronchial epithelial cells.
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    \51\ Hudda, N., Simon, N.C., Zamore, W., Durant, J.L. 2018. 
Aviation-related impacts on ultrafine number concentrations outside 
and inside residences near an airport. Environ. Sci. Technol. 52: 
1765-1772. https://pubs.acs.org/doi/abs/10.1021/acs.est.7b05593.
    \52\ Hudda, N., Simon, M.C., Zamore, W., Brugge, D., Durant, 
J.L. 2016. Aviation emissions impact ultrafine particle 
concentrations in the greater Boston area. Environ. Sci. Technol. 
50: 8514-8521. https://pubs.acs.org/doi/abs/10.1021/acs.est.6b01815.
    \53\ Stacey, B. 2019. Measurement of ultrafine particles at 
airports: A review. Atmos. Environ. 198: 463-477. https://www.sciencedirect.com/science/article/pii/S1352231018307313.
    \54\ Masiol M, Harrison RM. Quantification of air quality 
impacts of London Heathrow Airport (UK) from 2005 to 2012. Atmos 
Environ 2017;116:308-19. https://doi.org/10.1016/j.atmosenv.2015.06.048.
    \55\ Keuken, M.P., Moerman, M., Zandveld, P., Henzing, J.S., 
Hoek, G., 2015. Total and size-resolved particle number and black 
carbon concentrations in urban areas near Schiphol airport (the 
Netherlands). Atmos. Environ. 104: 132-142. https://www.sciencedirect.com/science/article/pii/S1352231015000175?via%3Dihub.
    \56\ Pirhadi, M., Mousavi, A., Sowlat, M.H., Janssen, N.A.H., 
Cassee, F.R., Sioutas, C., 2020. Relative contributions of a major 
international airport activities and other urban sources to the 
particle number concentrations (PNCs) at a nearby monitoring site. 
Environ. Pollut, 260: 114027. https://www.sciencedirect.com/science/article/pii/S0269749119344987?via%3Dihub.
    \57\ Stacey, B., Harrison, R.M., Pope, F., 2020. Evaluation of 
ultrafine particle concentrations and size distributions at London 
Heathrow Airport. Atmos. Environ., 222: 117148. https://www.sciencedirect.com/science/article/pii/S1352231019307873?via%3Dihub.
    \58\ Ungeheuer, F., Pinxteren, D., Vogel, A. 2021. 
Identification and source attribution of organic compounds in 
ultrafine particles near Frankfurt International Airport. Atmos. 
Chem. Phys. 21: 3763-3775. https://doi.org/10.5194/acp-21-3763-2021.
    \59\ Zhang, X., Karl, M. Zhang, L. Wang, J., 2020. Influence of 
Aviation Emission on the Particle Number Concentration near Zurich 
Airport. Environ. Sci. Technol. 54: 14161-14171. https://doi.org/10.1021/acs.est.0c02249.
    \60\ University of Washington. 2019. Mobile Observations of 
Ultrafine Particles: The Mov-UP study report. https://deohs.washington.edu/mov-up.
    \61\ Habre. R., Zhou, H., Eckel, S., Enebish, T., Fruin, S., 
Bastain, T., Rappaport, E. Gilliland, F. 2018. Short-term effects of 
airport-associated ultrafine particle exposure on lung function and 
inflammation in adults with asthma. Environment International 118: 
48-59. https://doi.org/10.1016/j.envint.2018.05.031.
    \62\ He, R.W., Shirmohammadi, F., Gerlofs-Nijland, M.E., 
Sioutas, C., & Cassee, F.R. 2018. Pro-inflammatory responses to 
PM(0.25) from airport and urban traffic emissions. The Science of 
the total environment, 640-641, 997-100. https://www.sciencedirect.com/science/article/pii/S0048969718320394?via%3Dihub.
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    Because of these potential impacts, a systematic literature review 
was recently conducted to identify peer-reviewed literature on air 
quality near commercial airports and assess the quality of the 
studies.\63\ The systematic review identified seventy studies for 
evaluation. These studies consistently showed that particulate matter, 
in the form of ultrafine PM (UFP), is elevated in and around airports. 
Furthermore, many studies showed elevated levels of black carbon, 
criteria pollutants, and polycyclic aromatic hydrocarbons as well. 
Finally, the systematic review, while not focused on health effects, 
identified a limited number of references reporting adverse health 
effects impacts, including increased rates of premature death, pre-term 
births, decreased lung function, oxidative DNA damage and childhood 
leukemia. More research is needed linking particle size distributions 
to specific airport activities, and proximity to airports, 
characterizing relationships between different pollutants, evaluating 
long-term impacts, and improving our understanding of health effects.
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    \63\ Riley, K., Cook, R., Carr, E., Manning, B. 2021. A 
Systematic Review of The Impact of Commercial Aircraft Activity on 
Air Quality Near Airports. City and Environment Interactions, 
100066. https://doi.org/10.1016/j.cacint.2021.100066.
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    A systematic review of health effects associated with exposure to 
jet engine emissions in the vicinity of airports was also recently 
published.\64\ This study concluded that literature on health effects 
was sparse, but jet engine emissions have physicochemical properties 
similar to diesel exhaust particles, and that exposure to jet engine 
emissions is associated with similar adverse health effects as exposure 
to diesel exhaust particles and other traffic emissions. A 2010 
systematic review by the Health Effects Institute (HEI) concluded that 
evidence was sufficient to support a causal relationship between 
exposure to traffic-related air pollution and exacerbation of asthma 
among children, and suggestive of a causal relationship for childhood 
asthma, non-asthma respiratory symptoms, impaired lung function and 
cardiovascular mortality.\65\
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    \64\ Bendtsen, K. M., Bengtsen, E., Saber, A., Vogel, U. 2021. A 
review of health effects associated with exposure to jet engine 
emissions in and around airports. Environ. Health 20:10. https://doi.org/10.1186/s12940-020-00690-y.
    \65\ Health Effects institute. ``Special Report 17: A Special 
Report of the Institute's Panel on the Health Effects of Traffic-
Related Air Pollution.'' January, 2010. https://www.healtheffects.org/publication/traffic-related-air-pollution-critical-review-literature-emissions-exposure-and-health.
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E. Contribution of Aircraft Emissions to PM in Selected Areas

    This section provides background on the contribution of aircraft 
engine emissions to local PM concentrations. In some areas with large 
commercial airports, turbine engine aircraft can make a significant 
contribution to ambient PM2.5. To evaluate these potential 
impacts, we identified the 25 airports where commercial aircraft 
operations are the greatest, based on data for 2017 from the Federal 
Aviation Administration (FAA) Air Traffic Data System (ATADS).\66\ 
These 25 commercial airports are located in 24 counties and 22 
metropolitan statistical areas (MSAs). We compared the contributions of 
these airports to emissions at both the county and MSA levels. 
Comparisons at both scales provide a fuller picture of how airports are 
impacting local air quality. Figure III-1 depicts the contribution to 
county-level PM2.5 direct emissions from all turbine 
aircraft in that county with rated output of greater than 26.7 kN. 
Emissions data were obtained from the EPA 2017 National Emissions 
Inventory (NEI).\67\ The contributions of engines greater than 26.7 kN 
rated output to total turbine engine emissions at individual airports 
were estimated based on FAA data.\68\ At the county level, 
contributions to total mobile source PM2.5 emissions range 
from less than 1 to almost 14 percent. However, it should be noted that 
two airports cross county lines--Hartsfield-Jackson Atlanta 
International Airport (Clayton and Fulton counties) and O'Hare (Cook 
and DuPage counties). For those airports, percentages are calculated 
for the sum of the two counties. In addition, five of these counties 
are in nonattainment for either the PM2.5 or PM10 
standard. When emissions from these airports are considered as part of 
the entire MSA, the contribution is much smaller. Figure III-2 depicts 
the contributions at the metropolitan statistical area (MSA) instead of 
the county level, and contributions across airports range from 0.4 to 3 
percent. Details of this analysis are described in a memorandum to the 
docket.\69\
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    \66\ https://aspm.faa.gov/opsnet/sys/main.asp.
    \67\ 2017 National Emissions Inventory: Aviation Component, 
Eastern Research Group, Inc., July 25, 2019, EPA Contract No. EP-C-
17-011, Work Order No. 2-19. Available at https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-data 
(last accessed on June 27, 2021). See section 3.2 for airports and 
aircraft related emissions in the Technical Supporting Document for 
the 2017 National Emissions Inventory, January 2021 Updated Release. 
Available at https://www.epa.gov/sites/production/files/2021-02/documents/nei2017_tsd_full_jan2021.pdf (last accessed on June 27, 
2021).
    \68\ These data were obtained using radar-informed data from the 
FAA Enhanced Traffic Management System (ETMS). The annual fuel burn 
and emissions inventories at selected top US airports were based on 
the 2015 FAA flight operations database. The fraction of total PM 
emissions from aircraft covered by the proposed PM standards is 
based on the ratio of total PM emissions from flights by engines 
with thrust rating >26.7 kN compared to PM emissions from the whole 
fleet at each airport.
    \69\ Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660, July 
28, 2021, '' Estimation of 2017 Emissions Contributions of Turbine 
Aircraft >26.7 kN to NOX and PM2.5 as a 
Percentage of All Mobile PM2.5 for the Counties and MSAs 
in Which the Airport Resides, 25 Largest Carrier Operations.''
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F. Other Pollutants Emitted by Aircraft

    In addition to particulate matter, a number of other criteria 
pollutants are emitted by the aircraft which are the subject of this 
proposed rule. These pollutants, which are not covered by the rule, 
include nitrogen oxides (NOX), including nitrogen dioxide 
(NO2), volatile organic compounds (VOC), carbon monoxide 
(CO), and sulfur dioxide (SO2). Aircraft also contribute to 
ambient levels of hazardous air pollutants (HAP), compounds that are 
known or suspected human or animal carcinogens, or that have noncancer 
health effects. These compounds include, but are not limited to, 
benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, 
polycyclic organic matter (POM), and certain metals. Some POM and HAP 
metals are components of PM2.5 mass measured in turbine 
engine aircraft emissions.\70\
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    \70\ Kinsey, J.S., Hays, M.D., Dong, Y., Williams, D.C. Logan, 
R. 2011. Chemical characterization of the fine particle emissions 
from commercial aircraft engines during the aircraft particle 
emissions experiment (APEX) 1-3. Environ. Sci. Technol. 45:3415-
3421. https://pubs.acs.org/doi/10.1021/es103880d.
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    The term polycyclic organic matter (POM) defines a broad class of 
compounds that includes the polycyclic aromatic hydrocarbon compounds 
(PAHs). POM compounds are formed primarily from combustion and are 
present in the atmosphere in gas and particulate form. Metal compounds 
emitted from aircraft turbine engine combustion include chromium, 
manganese, and nickel. Several POM compounds, as well as hexavalent 
chromium, manganese compounds and nickel compounds are included in the 
National Air Toxics Assessment, based on potential carcinogenic 
risk.\71\ In addition, as mentioned previously, deposition of metallic 
compounds can have ecological effects. Impacts of POM and metals are 
further discussed in the memorandum to the docket referenced above.
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    \71\ https://www.epa.gov/national-air-toxics-assessment.
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G. Environmental Justice

    Executive Order 12898 (59 FR 7629, February 16, 1994) establishes 
federal executive policy on environmental justice. It directs federal 
agencies, to the greatest extent practicable and permitted by law, to 
make achieving environmental justice part of their mission by 
identifying and addressing, as appropriate, disproportionately high and 
adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States. EPA defines environmental justice as 
the fair treatment and meaningful involvement of all people regardless 
of race, color, national origin, or income with respect to the 
development, implementation, and enforcement of environmental laws, 
regulations, and policies.\72\
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    \72\ Fair treatment means that ``no group of people should bear 
a disproportionate burden of environmental harms and risks, 
including those resulting from the negative environmental 
consequences of industrial, governmental and commercial operations 
or programs and policies.'' Meaningful involvement occurs when ``(1) 
potentially affected populations have an appropriate opportunity to 
participate in decisions about a proposed activity [e.g., 
rulemaking] that will affect their environment and/or health; (2) 
the public's contribution can influence [the EPA's rulemaking] 
decision; (3) the concerns of all participants involved will be 
considered in the decision-making process; and (4) [the EPA will] 
seek out and facilitate the involvement of those potentially 
affected'' A potential EJ concern is defined as ``the actual or 
potential lack of fair treatment or meaningful involvement of 
minority populations, low-income populations, tribes, and indigenous 
peoples in the development, implementation and enforcement of 
environmental laws, regulations and policies.'' See ``Guidance on 
Considering Environmental Justice During the Development of an 
Action.'' Environmental Protection Agency, https://www.epa.gov/environmentaljustice.
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    Executive Order 14008 (86 FR 7619, February 1, 2021) also calls on 
federal agencies to make achieving environmental justice part of their 
missions ``by developing programs, policies, and activities to address 
the disproportionately high and adverse human health, environmental, 
climate-related and other cumulative impacts on disadvantaged 
communities, as well as the accompanying economic challenges of such 
impacts.'' It also declares a policy ``to secure environmental justice 
and spur economic opportunity for disadvantaged communities that have 
been historically marginalized and overburdened by pollution and under-
investment in housing, transportation, water and wastewater 
infrastructure and health care.'' Under Executive Order 13563, federal 
agencies may consider equity, human dignity, fairness, and 
distributional considerations, where appropriate and permitted by law.
    EPA's June 2016 ``Technical Guidance for Assessing Environmental 
Justice in Regulatory Analysis'' provides recommendations on conducting 
the highest quality analysis feasible, recognizing that data 
limitations, time and resource constraints, and analytic challenges 
will vary by media and regulatory context.\73\
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    \73\ ``Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis.'' Epa.gov, Environmental Protection Agency, 
https://www.epa.gov/sites/production/files/2016-06/documents/ejtg_5_6_16_v5.1.pdf (June 2016).
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    When assessing the potential for disproportionately high and 
adverse health or environmental impacts of regulatory actions on 
minority populations, low-income populations, tribes, and/or indigenous 
peoples, the EPA strives to answer three broad questions: (1) Is there 
evidence of potential EJ concerns in the baseline (the state of the 
world absent the regulatory action)? Assessing the baseline will allow 
the EPA to determine whether pre-existing disparities are associated 
with the pollutant(s) under consideration (e.g., if the effects of the 
pollutant(s) are more concentrated in some population groups). (2) Is 
there evidence of potential EJ concerns for the regulatory option(s) 
under consideration? Specifically, how are the pollutant(s) and its 
effects distributed for the regulatory options under consideration? 
And, (3) do the regulatory option(s) under consideration exacerbate or 
mitigate EJ concerns relative to the baseline? It is not always 
possible to quantitatively assess these questions.
    EPA's 2016 Technical Guidance does not prescribe or recommend a 
specific approach or methodology for conducting an environmental 
justice analysis, though a key consideration is consistency with the 
assumptions underlying other parts of the regulatory analysis when 
evaluating the baseline and regulatory options. Where applicable and 
practicable, the Agency endeavors to conduct such an analysis. Going 
forward, EPA is committed to conducting environmental justice analysis 
for rulemakings based on a framework similar to what is outlined in 
EPA's Technical Guidance, in addition to investigating ways to further 
weave environmental justice into the fabric of the rulemaking process.

[[Page 6336]]

    Numerous studies have found that environmental hazards such as air 
pollution are more prevalent in areas where people of color and low-
income populations represent a higher fraction of the population 
compared with the general population, including near transportation 
sources.74 75 76 77 78
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    \74\ Rowangould, G.M. (2013) A census of the near-roadway 
population: Public health and environmental justice considerations. 
Trans Res D 25: 59-67. https://dx.doi.org/10.1016/j.trd.2013.08.003.
    \75\ Marshall, J.D., Swor, K.R., Nguyen, N.P. (2014) 
Prioritizing environmental justice and equality: Diesel emissions in 
Southern California. Environ Sci Technol 48: 4063-4068. https://doi.org/10.1021/es405167f.
    \76\ Marshall, J.D. (2000) Environmental inequality: Air 
pollution exposures in California's South Coast Air Basin. Atmos 
Environ 21: 5499-5503. https://doi.org/10.1016/j.atmosenv.2008.02.005.
    \77\ Tessum, C.W., Paolella, D.A., Chambliss, SE, Apte, J.S., 
Hill, J.D., Marshall, J.D. (2021) PM2.5 polluters 
disproportionately and systemically affect people of color in the 
United States. Science Advances 7:eabf4491. https://www.science.org/doi/10.1126/sciadv.abf4491.
    \78\ Mohai, P., Pellow, D., Roberts Timmons, J. (2009) 
Environmental justice. Annual Reviews 34: 405-430. https://doi.org/10.1146/annurev-environ-082508-094348.
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    As described in Section III.D, concentrations of PM increase with 
proximity to an airport. Air pollution can disproportionately impact 
sensitive subpopulations near airports. Henry et al. (2019) studied 
impacts of several California airports on surrounding schools and found 
that over 65,000 students spend 1 to 6 hours a day during the academic 
year being exposed to airport pollution, and the percentage of impacted 
students was higher for those who were economically disadvantaged.\79\ 
Rissman et al. (2013) studied PM2.5 at the Hartsfield-
Jackson Atlanta International Airport and found that the relationship 
between minority population percentages and aircraft-derived PM was 
found to grow stronger as concentrations increased.\80\
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    \79\ Henry, R.C., Mohan, S., Yazdani, S. (2019) Estimating 
potential air quality impact of airports on children attending the 
surrounding schools. Atmospheric Environment, 212: 128-135. https://www.sciencedirect.com/science/article/pii/S1352231019303516?via%3Dihub.
    \80\ Rissman, J., Arunachalam, S., BenDor, T., West, J.J. (2013) 
Equity and health impacts of aircraft emissions at the Hartfield-
Jackson Atlanta International Airport, Landscape and Urban Planning 
120: 234-247. https://www.sciencedirect.com/science/article/pii/S0169204613001382.
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    Additional studies have reported that many communities in close 
proximity to airports are disproportionately represented by minorities 
and low-income populations. McNair (2020) describes nineteen major 
airports that underwent capacity expansion projects between 2000 and 
2010, thirteen of which met characteristics of race, ethnicity, 
nationality and/or income that indicate a disproportionate impact on 
these residents.\81\ Woodburn (2017) reports on changes in communities 
near airports from 1970-2010, finding suggestive evidence that at many 
hub airports over time, the presence of marginalized groups residing in 
close proximity to airports increased.\82\
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    \81\ McNair, A. (2020) Investigation of environmental justice 
analysis in airport planning practice from 2000 to 2010. Transp. 
Research Part D 81:102286. https://www.sciencedirect.com/science/article/pii/S1361920919311149?via%3Dihub.
    \82\ Woodburn, A. (2017) Investigating neighborhood change in 
airport-adjacent communities in multiairport regions from 1970 to 
2010. Journal of the Transportation Research Board, 2626, 1-8.
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    Although not being conducted as part of this rulemaking, EPA is 
conducting a demographic analysis to explore whether populations living 
nearest the busiest runways show patterns of racial and socioeconomic 
disparity.\83\ This will help characterize the state of environmental 
justice concerns and inform potential future actions. Finely resolved 
population data (i.e., 30 square meters) will be paired with census 
block group demographic characteristics to evaluate if people of color, 
children, indigenous populations, and low-income populations are 
disproportionately living near airport runways compared to populations 
living further away. The results of this analysis could help inform 
additional policies to reduce pollution in communities living in close 
proximity to airports.
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    \83\ EPA anticipates that the results of the study will be 
released publicly in a separate document from the final rule.
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    In summary, the proposed in-production standards for both PM mass 
and PM number are levels that all aircraft engines in production 
currently meet in order to align with ICAO's standards. Thus, the 
proposed standards are not expected to result in emission reductions, 
beyond the business-as-usual fleet turnover that would occur absent of 
the proposed standards. Therefore, we do not anticipate an improvement 
in air quality for those who live near airports where these aircraft 
operate.

IV. Details for the Proposed Rule

    In considering what PM emissions standards for aircraft engines are 
appropriate to adopt under section 231 of the CAA, EPA, after 
consultation with FAA, took into consideration the importance of both 
controlling PM emissions and international harmonization of aviation 
requirements. In addition, the EPA gave significant weight to the 
U.S.'s treaty obligations under the Chicago Convention in determining 
the need for and appropriate levels of PM standards. These 
considerations led the EPA to propose aircraft engine PM standards 
based on engine standards adopted by ICAO. When developing the PM 
standards, ICAO looked at three different methods of measuring the 
amount of PM emitted. The first is PM mass, or a measure of the total 
weight of the particles produced over the test cycle. This is how the 
EPA has historically set PM emissions standards for other sectors. 
Second, ICAO considered PM number, or the number of particles produced 
by the engine over the test cycle. These are two different methods of 
measuring the same pollutant, PM, but each provides distinct and 
valuable information. Third, ICAO developed PM mass concentration 
standards, as a replacement to the existing standards based on smoke 
number.
    EPA's proposed action consists of three key parts: (1) A proposal 
for PM mass and number emissions standards for aircraft gas turbine 
engines, (2) a change in test procedure and form of the existing 
standards--from smoke number to PM mass concentration, and (3) new 
testing and measurement procedures for the PM emission standards and 
various updates to the existing gaseous exhaust emissions test 
procedures.
    Sections IV.A through IV.C describe the proposed mass, number, and 
mass concentration standards for aircraft engines. Section IV.D 
describes the proposed test procedures and measurement procedures 
associated with the PM standards. Section IV.E presents information 
related to the proposed reporting requirements.
    As discussed above in Section III.A, PM2.5 consists of 
both volatile and nonvolatile PM, although only nonvolatile PM would be 
covered by the proposed standards. Only nonvolatile PM is present at 
the engine exit because the exhaust temperature is too high for 
volatile PM to form. The volatile PM (or secondary PM) is formed as the 
engine exhaust plume cools and mixes with the ambient air. The result 
of this is that the volatile PM is significantly influenced by the 
ambient conditions (or ambient air background composition). Because of 
this complexity, a test procedure to measure volatile PM has not yet 
been developed for aircraft engines. In order to directly measure 
nonvolatile PM, ICAO agreed to adopt a measurement procedure, as 
described below in Section IV.D, which is based on conditions that 
prevent the formation of volatile PM upstream of the measurement 
instruments. The intent of

[[Page 6337]]

this approach is to improve the consistency and repeatability of the 
nvPM measurement procedure.
    Due to the international nature of the aviation industry, there is 
an advantage to working within ICAO, in order to secure the highest 
practicable degree of uniformity in international aviation regulations 
and standards. Uniformity in international aviation regulations and 
standards is a goal of the Chicago Convention, because it ensures that 
passengers and the public can expect similar levels of protection for 
safety and human health and the environment regardless of manufacturer, 
airline, or point of origin of a flight. Further, it helps prevent 
barriers in the global aviation market, benefiting both U.S. aircraft 
engine manufacturers and consumers.
    When developing new emissions standards, ICAO/CAEP seeks to capture 
the technological advances made in the control of emissions through the 
adoption of anti-backsliding standards reflecting the current state of 
technology. The PM standards the EPA is proposing were developed using 
this approach. Thus, the adoption of these aircraft engine standards 
into U.S. law would simultaneously prevent aircraft engine PM levels 
from increasing beyond their current levels, align U.S. domestic 
standards with the ICAO standards for international harmonization, and 
help the U.S. meet its treaty obligations under the Chicago Convention.
    These proposed standards would also allow U.S. manufacturers of 
covered aircraft engines to remain competitive in the global 
marketplace. The ICAO aircraft engine PM emission standards have been, 
or are being, adopted by other ICAO member states that certify aircraft 
engines. In the absence of U.S. standards implementing the ICAO 
aircraft engine PM emission standards, the U.S. would not be able to 
certify aircraft engines to the PM standards. In this case, U.S. civil 
aircraft engine manufacturers could be forced to seek PM emissions 
certification from an aviation certification authority of another 
country in order to market and operate their aircraft engines 
internationally. Foreign certification authorities may not have the 
resources to certify aircraft engines from U.S. manufacturers in a 
timely manner, which could lead to delays in these engines being 
certified. Thus, U.S. manufacturers could be at a disadvantage if the 
U.S. does not adopt standards that are at least as stringent as the 
ICAO standards for PM emissions. The proposed action to adopt in the 
U.S. PM standards that match the ICAO standards would help ensure 
international consistency and acceptance of U.S. manufactured engines 
worldwide.
    The EPA considered whether to propose standards more stringent than 
the ICAO standards. As noted above, the EPA considered both the need 
for emissions reductions and the international nature of the aircraft 
industry and air travel in evaluating whether to propose more stringent 
standards. These considerations have historically led the EPA to adopt 
international standards developed through ICAO. The EPA concluded that 
proposing to adopt the ICAO PM standards in place of more stringent 
standards is appropriate in part because international uniformity and 
regulatory certainty are important elements of these proposed 
standards. This is especially true for these proposed standards because 
they change our approach to regulating aircraft PM emissions from past 
smoke measurements to the measurement of nvPM mass and number for the 
first time. It is appropriate to gain experience from the 
implementation of these nvPM standards before considering whether to 
adopt more stringent nvPM mass and/or number standards, or whether 
another approach to PM regulation would better address the health risks 
of PM emissions from aircraft engines. Additionally, the U.S. 
Government played a significant role in the development of these 
proposed standards. The EPA believes that international cooperation on 
aircraft emissions brings substantial benefits overall to the United 
States. Having invested significant effort to develop these standards 
and obtain international consensus for ICAO to adopt these standards, a 
decision by the United States to deviate from them might well undermine 
future efforts by the United States to seek international consensus on 
aircraft emissions standards. For these reasons, EPA placed significant 
weight on international regulatory uniformity and certainty and is 
proposing standards that match the standards which EPA worked to 
develop and adopt at ICAO, and is not proposing more stringent 
standards.

A. PM Mass Standards for Aircraft Engines

1. Applicability of Standards
    These proposed standards for PM mass, like the ICAO standards, 
would apply to all subsonic turbofan and turbojet engines of a type or 
model with a rated output (maximum thrust available for takeoff) 
greater than 26.7 kN whose date of manufacture is on or after January 
1, 2023.\84\ These proposed standards would not apply to engines 
manufactured prior to this applicability date.
---------------------------------------------------------------------------

    \84\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-3 & III-4-4pp. 
Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed November 15, 2021). The ICAO Annex 16 
Volume II is found on page 17 of the ICAO Products & Services 
Catalog, English Edition of the 2021 catalog, and it is copyright 
protected; Order No. AN16-2. The ICAO Annex 16, Volume II, Fourth 
Edition, includes Amendment 10 of January 1, 2021. Amendment 10 is 
also found on page 17 of this ICAO catalog, and it is copyright 
protected; Order No. AN 16-2/E/12.
---------------------------------------------------------------------------

    The level of the proposed standard would vary based on when the 
initial type certification application is submitted.\85\ Engines for 
which the type certificate application was first submitted on or after 
January 1, 2023 would be subject to the new type level in Section 
IV.A.2 below. These engines are new engines that have not been 
previously certificated.
---------------------------------------------------------------------------

    \85\ In most cases, the engine manufacturer applies to FAA for 
the type certification; however, in some cases the applicant may be 
different than the manufacturer (e.g., designer).
---------------------------------------------------------------------------

    Engines manufactured on or after January 1, 2023 would be subject 
to the in-production level, in Section IV.A.3 below.

[[Page 6338]]

2. New Type nvPM Mass Numerical Emission Limits for Aircraft Engines
    Aircraft engines with a rated output (rO), maximum thrust available 
for take-off, greater than 26.7 kN and whose initial type certification 
application is submitted to the FAA on or after January 1, 2023 shall 
not exceed the level, as defined by Equation IV-1. As described in 
Section IV.D, the nvPM Mass limit is based on mg of PM divided by kN of 
thrust, as determined over the LTO cycle.
[GRAPHIC] [TIFF OMITTED] TP03FE22.029

3. In Production nvPM Mass Numerical Emission Limits for Aircraft 
Engines

    Aircraft engines that are manufactured on or after January 1, 2023 
shall not exceed the level, as defined by Equation IV-2.
[GRAPHIC] [TIFF OMITTED] TP03FE22.030

4. Graphical Representation of nvPM Mass Numerical Emission Limits

    Figure IV-1 shows how the proposed nvPM mass emission limits 
compare to known in-production engines.
    Data shown in this figure is from the ICAO Engine Emissions 
Databank (EEDB).86 87
---------------------------------------------------------------------------

    \86\ ICAO Aircraft Engine Emissions Databank, July 20, 2021, 
``edb-emissions-databank v28C (web).xlsx'', European Union Aviation 
Safety Agency (EASA), https://www.easa.europa.eu/domains/environment/icao-aircraft-engine-emissions-databank.
    \87\ Note, EPA ICR number 2427.06 ``Aircraft Engines--
Supplemental information related to Exhaust Emissions'' also 
collects aircraft nvPM data. In the interest of using the most up to 
date information, the ICAO EDB was used because it has been updated 
more recently than EPA data. The EPA should be receiving new data 
from this ICR in Feb. 2022.
[GRAPHIC] [TIFF OMITTED] TP03FE22.031

B. PM Number Standards for Aircraft Engines

1. Applicability of Standards

    These proposed standards for PM number, like the ICAO standards, 
would apply to all subsonic turbofan and turbojet engines of a type or 
model with a rated output greater than 26.7 kN whose date of 
manufacture is on or after January 1, 2023.\88\ These proposed 
standards would not apply to engines manufactured prior to this 
applicability date.
    The level of the proposed standard would vary based on when the 
initial type certification application is submitted. Engines for which 
the type

[[Page 6339]]

certificate application was first submitted on or after January 1, 2023 
would be subject to the new type level in Section IV.B.2 below. These 
are new engines that have not been previously certificated.
    Engines manufactured on or after January 1, 2023 would be subject 
to the in-production level, in IV.B.3 below.

2. New Type nvPM Number Numerical Emission Limits for Aircraft Engines

    Aircraft engines with a rated output greater than 26.7 kN and whose 
initial type certification application is submitted to the FAA on or 
after January 1, 2023 shall not exceed the level, as defined by 
Equation IV-3. As described in Section IV.D, the nvPM number limit is 
based on number of particles divided by kN of thrust, as determined 
over the LTO cycle.
[GRAPHIC] [TIFF OMITTED] TP03FE22.032

3. In Production nvPM Number Numerical Emission Limits for Aircraft 
Engines

    Aircraft engines that are manufactured on or after January 1, 2023 
shall not exceed the level, as defined by Equation IV-4.
[GRAPHIC] [TIFF OMITTED] TP03FE22.033

4. Graphical Representation of nvPM Number Numerical Emission Limits

    Figure IV-2 shows how the proposed nvPM number emission limits 
compare to known in-production engines. Data shown in this figure is 
from the ICA O Engine Emissions Databank (EEDB).\89\
---------------------------------------------------------------------------

    \88\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-4pp. Available at 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on 
page 17 of the ICAO Products & Services Catalog, English Edition of 
the 2021 catalog, and it is copyright protected; Order No. AN16-2. 
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 
of January 1, 2021. Amendment 10 is also found on page 17 of this 
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
    \89\ ICAO Aircraft Engine Emissions Databank, July 20, 2021, 
``edb-emissions-databank v28C (web).xlsx'', European Union Aviation 
Safety Agency (EASA), https://www.easa.europa.eu/domains/environment/icao-aircraft/-engine-emissions/-databank (last accessed 
November 15, 2021).
[GRAPHIC] [TIFF OMITTED] TP03FE22.034

[[Page 6340]]

C. PM Mass Concentration Standard for Aircraft Engines

    The current smoke number-based standards were adopted to reduce the 
visible smoke emitted by aircraft engines. Smoke number is quantified 
by measuring the opacity of a filter after soot has been collected upon 
it during the test procedure. Another means of quantifying the smoke 
from an engine exhaust is through PM mass concentration 
(PMmc).
    ICAO developed a PM mass concentration standard during the CAEP/10 
cycle and adopted it in 2017. This PM mass concentration standard was 
developed to provide equivalent exhaust visibility control as the 
existing smoke number standard starting on January 1, 2020. With the 
EPA's involvement, the ICAO PM mass concentration limit line was 
developed using measured smoke number and PM mass concentration data 
from several engines to derive a smoke number-to-PM mass concentration 
correlation. This correlation was then used to transform the existing 
smoke number-based limit line into a generally equivalent PM mass 
concentration limit line, which was ultimately adopted by ICAO as the 
CAEP/10 PM mass concentration standard. The intention when the 
equivalent PM mass concentration standard was adopted was that 
equivalent visibility control would be maintained and testing would 
coincide with the PM mass and PM number measurement, thus removing the 
need to separately test and measure smoke number.
    While the ICAO PM mass concentration standard was intended to have 
equivalent visibility control as the existing SN standard, the method 
used to derive it was based on limited data and needed to be confirmed 
for regulatory purposes. Additional analysis was conducted during the 
CAEP/11 cycle to confirm this equivalence. The EPA followed this work 
as it progressed, provided input during the process, and ultimately 
concurred with the results.\90\ The analysis, based on aerosol optical 
theory and visibility criterion, demonstrated with a high level of 
confidence that the ICAO PM mass concentration standard did indeed 
provide equivalent visibility control as the existing smoke number 
standard. This provided the justification for ICAO to agree to end 
applicability of the existing smoke number standard for engines subject 
to the PM mass concentration standard, effective January 1, 2023.
---------------------------------------------------------------------------

    \90\ ICAO, 2019: Report of Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP/11. It is found on page 26 of the English 
Edition of the ICAO Products & Services 2021 Catalog and is 
copyright protected; Order No. 10126. For purchase available at: 
https://www.icao.int/publications/Pages/catalogue.aspx (last 
accessed November 15, 2021). The analysis performed to confirm the 
equivalence of the PM mass concentration standard and the SN 
standard is located in Appendix C (starting on page 3C-33) of this 
report.
---------------------------------------------------------------------------

1. PM Mass Concentration Standard
    The EPA is proposing to adopt a PM mass concentration standard for 
all aircraft engines with rated output greater than 26.7 kN and 
manufactured on or after January 1, 2023.\91\ This proposed standard 
has the same form, test procedures, and stringency as the CAEP/10 PM 
mass concentration standard adopted by ICAO in 2017. However, the 
applicability date proposed here is different than that agreed to by 
ICAO. The proposed PM mass concentration standard is based on the 
maximum concentration of PM emitted by the engine at any thrust 
setting, measured in micrograms ([micro]g) per meter cubed (m\3\). This 
is similar to the current smoke standard, which is also based on the 
measured maximum at any thrust setting. Section IV.D describes the 
measurement procedure. Like the LTO-based PM mass and PM number 
standards discussed above, this is based on the measurement of nvPM 
only, not total PM emissions.
---------------------------------------------------------------------------

    \91\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-3. Available at 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on 
page 17 of the ICAO Products & Services Catalog, English Edition of 
the 2021 catalog, and it is copyright protected; Order No. AN16-2. 
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 
of January 1, 2021. Amendment 10 is also found on page 17 of this 
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
---------------------------------------------------------------------------

    To determine compliance with the proposed PM mass concentration 
standard, the maximum nvPM mass concentration [[mu]g/m\3\] would be 
obtained from measurement at sufficient thrust settings such that the 
emission maximum can be determined. The maximum value would then be 
converted to a characteristic level in accordance with the procedures 
in ICAO Annex 16, Volume II, Appendix 6. The resultant characteristic 
level must not exceed the regulatory level determined from the 
following formula:
[GRAPHIC] [TIFF OMITTED] TP03FE22.035

    Engines certificated under the new PM mass concentration standard 
would not need to certify smoke number values and would not be subject 
to in-use smoke standards. It is important to note that other smoke 
number standards remain in effect for in-production aircraft turbofan 
and turbojet engines at or below 26.7 kN rated output and for in-
production turboprop engines. Also, the in-use smoke standards will 
continue to apply to some already manufactured aircraft engines that 
were certified to smoke number standards.
2. Graphical Representation of nvPM Mass Concentration Numerical 
Emission Limit
    Figure IV-3 shows how the proposed nvPM mass concentration emission 
limits compare to known in-production engines. Data shown in this 
figure is from the ICAO Engine Emissions Databank EEDB).\92\
---------------------------------------------------------------------------

    \92\ ICAO Aircraft Engine Emissions Databank, July 20, 2021, 
``edb-emissions-databank v28C (web).xlsx'', European Union Aviation 
Safety Agency (EASA), https://www.easa.europa.eu/domains/environment/icao-aircraft/-engine-emissions/-databank.

---------------------------------------------------------------------------

[[Page 6341]]

[GRAPHIC] [TIFF OMITTED] TP03FE22.036

D. Test and Measurement Procedures

1. Aircraft Engine PM Emissions Metrics
    When developing the PM standards, ICAO looked at three different 
methods of measuring the amount of PM emitted. The first is PM mass, or 
a measure of the total weight of the particles produced over the test 
cycle. This is how the EPA has historically measured PM emissions 
subject to standards for other sectors. Second, ICAO considered PM 
number, or the number of particles produced by the engine over the test 
cycle. These are two different methods of measuring the same pollutant, 
PM, but each provides valuable information. Third, ICAO developed PM 
mass concentration standards, as an alternative to the existing 
visibility standards based on smoke.
    The EPA proposes to incorporate by reference the metrics agreed at 
ICAO and incorporated into Annex 16 Volume II, to measure PM mass 
(Equation IV-6) and PM number (Equation IV-7). These metrics are based 
on a measurement of the nvPM emissions, as measured at the instrument, 
over the LTO cycle and is normalized by the rated output of the engine 
(rO).
[GRAPHIC] [TIFF OMITTED] TP03FE22.037

    The EPA proposes the PM mass concentration standard be based on the 
maximum mass concentration, in micrograms per meter cubed, produced by 
the engine at any thrust setting.
    Regulatory compliance with the emissions standards is based on the 
product of Equation IV-6 or Equation

[[Page 6342]]

IV-7 or mass concentration divided by a correction factor in Table IV-
2, to obtain the characteristic level that is used to determine 
compliance with emissions standards (see IV.D.4 below).
2. Test Procedure
    The emission test and measurement procedures adopted by ICAO were 
produced in conjunction with the Society of Automotive Engineers (SAE) 
E-31 Aircraft Exhaust Emissions Measurement Committee.\93\ These 
procedures were developed in SAE E-31 in close consultation between 
government and industry, and subsequently they were adopted by ICAO and 
incorporated into ICAO Annex 16, Volume II.
---------------------------------------------------------------------------

    \93\ ``E-31 Committee was formed to develop and maintain 
cognizance of standards for measurement of emissions from aircraft 
powerplants and to promote a rational and uniform approach to the 
measurement of emissions form aircraft engines and combustion 
systems to support the practical assessment of the industry. The E-
31 Committee, in its operation uses an Executive Committee, 
Membership Panel, Subcommittees and working technical panels as 
required to achieve its objectives.''
    (See https://www.sae.org/works/committeeHome./do?comtID=TEAE31, 
last accessed November 15, 2021).
---------------------------------------------------------------------------

    These procedures build off the existing aircraft engine measurement 
system for gaseous pollutants. At least 3 engine tests need to be 
conducted to determine the emissions rates. These tests can be 
conducted on a single engine or multiple engines.\94\ A representative 
sample of the engine exhaust is sampled at the engine exhaust exit. The 
exhaust then travels through a heated sample line where it is diluted 
and kept at a constant temperature prior to reaching the measurement 
instruments.
---------------------------------------------------------------------------

    \94\ All three tests could be conducted on a single engine. Or 
two tests could be conducted on one engine and one test on a second 
engine. Or three separate engines could each be tested a single 
time.
---------------------------------------------------------------------------

    The methodology for measuring PM from aircraft engines differs from 
other test procedures for mobile source PM2.5 standards in 
two ways. First, as discussed above, the procedure is designed to 
measure only the nonvolatile component of PM. The measurement of 
volatile PM is very dependent on the environment where it is measured. 
The practical development of a standardized method of measuring 
volatile PM has proved challenging. Therefore, the development of a 
procedure for nvPM was prioritized and the result is proposed here 
today.
    Second, the sample is measured continuously rather than being 
collected on a filter and measured after the test. This approach was 
taken primarily for the practical reasons that, due to high dilution 
rates leading to relatively low concentrations of PM in the sample, 
collecting enough particulate on a filter to analyze has the potential 
to take hours. Given the high fuel flow rates of these engines, such 
lengthy test modes would be very expensive. Additionally, because of 
the high volume of air required to run a jet engine and the extreme 
engine exhaust temperatures, it is not possible to collect the full 
exhaust stream in a controlled manner as is done for other mobile 
source PM2.5 measurements.
    Included in the proposed procedures, to be incorporated by 
reference, are measurement system specifications and requirements, 
instrument specifications and calibration requirements, fuel 
specifications, and corrections for fuel composition, dilution, and 
thermophoretic losses in the collection part of the sampling system.
    To create a uniform sampling system design that works across gas 
turbine engine testing facilities, the test procedure calls for a 35-
meter sample line. This results in a significant portion of the PM 
being lost in the sample lines, on the order of 50 percent for PM mass 
and 90 percent for PM number. These particle losses in the sampling 
system are not corrected for in the regulatory compliance levels 
(standards). Compliance with the standard is based on the measurement 
at the instruments rather than the exit plane of the engine 
(instruments are 35 meters from engine exit). This is due to the lack 
of robustness of the sampling system particle loss correction 
methodology and that a more stringent standard at the instrument will 
lead to a reduction in the nvPM emissions at the engine exit plane. A 
correction methodology has been developed to better estimate the actual 
PM emitted into the atmosphere. This correction is described below in 
Section V.A.2.
3. Test Duty Cycles
    Mass and number PM emissions are proposed to be measured over the 
Landing and Take-Off (LTO) cycle shown in Table IV-1. This is the same 
duty cycle used today to measure gaseous emissions from aircraft 
engines and is intended to represent operations and flight under an 
altitude of 3,000 feet near an airport. Due to challenges in measuring 
at these exact conditions and atmospheric and fuel corrections that 
need to be applied after testing; it is not necessary to measure 
exactly at these points. Emissions rates for each mode can be 
calculated by testing the engine(s) over a sufficient range of thrust 
settings such that the emission rates at each condition in Table IV-1 
can be determined.

 Table IV-1--Landing and Take-Off Cycle Thrust Settings and Time in Mode
                                  \95\
------------------------------------------------------------------------
                                                              Time in
           LTO operating mode             Thrust setting  operating mode
                                            Percent rO       (minutes)
------------------------------------------------------------------------
Take-off................................             100             0.7
Climb...................................              85             2.2
Approach................................              30             4.0
Taxi/ground idle........................               7            26.0
------------------------------------------------------------------------

    The existing smoke number standard was adopted to reduce the 
visible smoke emitted from aircraft engines. Smoke number has been 
determined by measuring the visibility or opacity of a filter after 
soot has been collected upon it during the test procedure. Another 
means of measuring this visibility is by direct measurement of the 
particulate matter mass concentration. By measuring visibility based on 
mass concentration rather than smoke

[[Page 6343]]

number, the number of tests needed can be reduced, and mass 
concentration data can be collected concurrently with other PM 
measurements. Like the existing smoke standard, the proposed PM mass 
concentration standard would be based on the maximum value at any 
thrust setting. The engine(s) would be tested over a sufficient range 
of thrust settings that the maximum can be determined. This maximum 
could be at any thrust setting and is not limited to the LTO thrust 
points.
---------------------------------------------------------------------------

    \95\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-2. Available at 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on 
page 17 of the ICAO Products & Services Catalog, English Edition of 
the 2021 catalog, and it is copyright protected; Order No. AN16-2. 
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 
of January 1, 2021. Amendment 10 is also found on page 17 of this 
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
---------------------------------------------------------------------------

    We are proposing to incorporate by reference ICAO's International 
Standards and Recommended Practices for aircraft engine PM testing and 
certification--ICAO Annex 16, Volume II.
4. Characteristic Level
    Like existing gaseous standards, compliance with the PM standards 
is proposed to be determined based on the characteristic level of the 
engine. The characteristic level is a statistical method of accounting 
for engine-to-engine variation in the measurement based on the number 
of engines tested. A minimum of 3 engine emissions tests is needed to 
determine the engine type's emissions rates for compliance with 
emissions standards. The more engines that are used for testing 
increases the confidence that the emissions rate measured is from a 
typical engine rather than a high or low engine.
    Table IV-2 below is reproduced from Annex 16 Volume II Appendix 6 
Table A6-1 and shows how these factors change based on the number of 
engines tested. As the number of engines tested increases, the factor 
also increases resulting in a smaller adjustment and reflecting the 
increased confidence that the emissions rate is reflective of the 
average engine off the production line. In this way, there is an 
incentive to test more engines to reduce the characteristic adjustment 
while also increasing confidence that the measured emissions rate is 
representative of the typical production engine.

                                               Table IV-2--Factors To Determine Characteristic Values \96\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                             nvPM mass                       nvPM LTO
      Number of engines  tested (i)             CO              HC              NOX             SN         concentration   nvPM LTO mass      number
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................         0.814 7         0.649 3         0.862 7         0.776 9         0.776 9         0.719 4         0.719 4
2.......................................         0.877 7         0.768 5         0.909 4         0.852 7         0.852 7         0.814 8         0.814 8
3.......................................         0.924 6         0.857 2         0.944 1         0.909 1         0.909 1         0.885 8         0.885 8
4.......................................         0.934 7         0.876 4         0.951 6         0.921 3         0.921 3         0.901 1         0.901 1
5.......................................         0.941 6         0.889 4         0.956 7         0.929 6         0.929 6         0.911 6         0.911 6
6.......................................         0.946 7         0.899 0         0.960 5         0.935 8         0.935 8         0.919 3         0.919 3
7.......................................         0.950 6         0.906 5         0.963 4         0.940 5         0.940 5         0.925 2         0.925 2
8.......................................         0.953 8         0.912 6         0.965 8         0.944 4         0.944 4         0.930 1         0.930 1
9.......................................         0.956 5         0.917 6         0.967 7         0.947 6         0.947 6         0.934 1         0.934 1
10......................................         0.958 7         0.921 8         0.969 4         0.950 2         0.950 2         0.937 5         0.937 5
more than 10............................      1-0.13059/      1-0.24724/      1-0.09678/      1-0.15736/      1-0.15736/      1-0.19778/      1-0.19778/
                                                [radic]i        [radic]i        [radic]i        [radic]i        [radic]i        [radic]i        [radic]i
--------------------------------------------------------------------------------------------------------------------------------------------------------

    For PM mass and PM number, the characteristic level would be based 
on the mean of all engines tested, and appropriately corrected, divided 
by the factor corresponding to the number of engine tests performed in 
Table IV-1. For PM mass concentration, the characteristic level would 
be based on the mean of the maximum values of all engines tested, and 
appropriately corrected, divided by the factor corresponding to the 
number of engine tests performed in Table IV-2.
---------------------------------------------------------------------------

    \96\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, App 6-2pp. Available at 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on 
page 17 of the ICAO Products & Services Catalog, English Edition of 
the 2021 catalog, and it is copyright protected; Order No. AN16-2. 
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 
of January 1, 2021. Amendment 10 is also found on page 17 of this 
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
---------------------------------------------------------------------------

    For example, an engine type where three measurements were obtained 
from the same engine has an nvPM mass metric value of 100 mg/kN (mean 
metric value of all engine tests). The nvPM LTO Mass factor (or nvPM 
mass characteristic factor) from Table IV-2 for three engines is 
0.7194. The metric value, with applicable corrections applied, is then 
divided by the factor to obtain the characteristic level of the engine. 
Therefore, the resulting characteristic level for this engine type, to 
determine compliance with the nvPM mass standard is 139.005mg/kN. If 
instead three engines are each tested once, the characteristic factor 
would be 0.8858 and the nvPM mass characteristic level to determine 
compliance with the standard would be 112.892 mg/kN.
    An engine type's characteristic level can also be further improved 
by testing additional engines. For example, if 10 separate engines were 
tested of the same type, the nvPM mass characteristic factor becomes 
0.9375. The resulting characteristic level (assuming the average nvPM 
mass metric value remains 100 mg/kN) would be 106.667 mg/kN. This 
approach could be used if an engine exceeds the standard at the time it 
is initially tested or there is a desire to increase the margin to the 
standard for whatever reason. Table IV-3 shows these three different 
examples for nvPM LTO Mass.

              Table IV-3--Impact of the Number of Engines Tested on Resulting Characteristic Level
----------------------------------------------------------------------------------------------------------------
                                                     Number of     Measured nvPM
            Number of engines tested                 tests per     LTO mass (mg/  Characteristic  Characteristic
                                                      engine            kN)           factor       level (mg/kN)
----------------------------------------------------------------------------------------------------------------
1...............................................               3             100          0.7194         139.005
3...............................................               1             100          0.8858         112.892
10..............................................               1             100          0.9375         106.667
----------------------------------------------------------------------------------------------------------------

[[Page 6344]]

    We are proposing to incorporate by reference ICAO's International 
Standards and Recommended Practices for correcting engine measurements 
to characteristic value--ICAO Annex 16, Volume II, Appendix 6.
5. Derivative Engines for Emissions Certification Purposes
    Aircraft engines can remain in production for many years and be 
subject to numerous modifications during its production life. As part 
of the certification process for any change, the type certificate 
holder will need to show that the change does not impact the engine 
emissions. While some of these changes could impact engine emissions 
rates, many of them will not. To simplify the certification process and 
reduce burden on both type certificate holder and certification 
authorities, ICAO developed criteria to determine whether there has 
been an emissions change that requires new testing. Such criteria 
already exist for gaseous and smoke standards.
    ICAO recommends that if the characteristic level for an engine was 
type certificated at a level that is at or above 80 percent of the PM 
mass, PM number, or PM mass concentration standard, the type 
certificate holder would be required to test the proposed derivative 
engine. If the engine is below 80 percent of the standard, engineering 
analysis can be used to determine new emission rates for the proposed 
derivative engines. Today, the EPA proposes to adopt these ICAO 
provisions.
    Subsequently, ICAO evaluated the measurement uncertainty to develop 
criteria for determining if a proposed derivative engine's emissions 
are similar to the previously certificated engine's emissions, which 
are described below. Today, the EPA proposes to adopt these ICAO 
criteria.
    For PM Mass measurements described above in Section IV.A, the 
following values would apply:
     80 mg/kN if the characteristic level for 
nvPMmass emissions is below 400 mg/kN.
     20% of the characteristic level if the 
characteristic level for nvPMmass emissions is greater than 
or equal to 400 mg/kN.
    For PM number measurements, described above in Section IV.B, the 
following values would apply:
     4 x 10[caret]14 particles/kN if the characteristic level 
for nvPMnum emissions is below 2 x 10[caret]15 particles/kN.
     20% of the characteristic level if the 
characteristic level for nvPMnum emissions is greater than 
or equal to 2 x 10[caret]15 particles/kN.
    For PM mass concentration measurements described above in Section 
IV.C, the following values would apply:
     200 [mu]g/m[caret]3 if the characteristic 
level of maximum nvPM mass concentration is below 1,000 [mu]g/
m[caret]3.
     20% of the characteristic level if the 
characteristic level for maximum nvPM mass concentration is at or above 
1,000 [mu]g/m[caret]3.
    If a type certificate holder can demonstrate that the engine's 
emissions are within these ranges, then new emissions rates would not 
need to be developed and the proposed derivative engine for emissions 
certification purposes could keep the existing emissions rates.
    If the engine is not determined to be a derivative engine for 
emissions certification purposes, the certificate holder would need to 
certify the new emission rates for the engine.

E. Annual Reporting Requirement

    In 2012, the EPA adopted an annual reporting requirement as part of 
a rulemaking to adopt updated aircraft engine NOX 
standards.\97\ This provision, adopted into 40 CFR 87.42, requires the 
manufacturers of covered engines to annually report data to the EPA 
which includes information on engine identification and 
characteristics, emissions data for all regulated pollutants, and 
production volumes. In 2018, the EPA issued an information collection 
request (ICR) which renewed the existing ICR and added PM information 
to the list of required data.98 99 However, that 2018 ICR 
was not part of a rulemaking effort, and the new PM reporting 
requirements were not incorporated into the CFR at that time. Further, 
that 2018 ICR is currently being renewed (in an action separate from 
this proposal), and the EPA is proposing as part of that effort to add 
some additional data elements to the ICR (specifically, the emission 
indices for HC, CO, and NOX at each mode of the LTO 
cycle).100 101 The EPA is now proposing to formally 
incorporate all aspects of that ICR, as proposed to be renewed, into 
the CFR in the proposed section 1031.150. It is important to note that 
the incorporation of the PM reporting requirements into the CFR would 
not create a new requirement for the manufacturers of aircraft engines. 
Rather, it would simply incorporate the existing reporting requirements 
(as proposed to be amended and renewed in a separate action) into the 
CFR for ease of use by having all the reporting requirements readily 
available in the CFR.
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    \97\ 77 FR 36342, June 18, 2012.
    \98\ 83 FR 44621, August 31, 2018.
    \99\ U.S. EPA, Aircraft Engines--Supplemental Information 
Related to Exhaust Emissions (Renewal), OMB Control Number 2060-
0680, ICR Reference Number 201809-2060-08, December 17, 2018. 
Available at https://www.reginfo.gov/public/do/PRAViewICR?ref_nbr=201809-2060-008, last accessed November 15, 2021.
    \100\ 86 FR 24614, May 7, 2021.
    \101\ Documentation and Public comments are available at: 
https://www.regulations.gov/docket/EPA-HQ-OAR-2016-0546, last 
accessed November 15, 2021.
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    The EPA uses the collection of information to help conduct 
technology assessments, develop aircraft emission inventories (for 
current and future inventories), and inform our policy decisions--
including future standard-setting actions. The information enables the 
EPA to further understand the characteristics of aircraft engines that 
are subject to emission standards--and engines proposed to be subject 
to the PM emission standards--and engines impact on emission 
inventories. In addition, the information helps the EPA set appropriate 
and achievable emission standards and related requirements for aircraft 
engines. Annually updated information helps in assessing technology 
trends and their impacts on national emissions inventories. Also, it 
assists the EPA to stay abreast of developments in the aircraft engine 
industry.
    As discussed in Section VII, the EPA is proposing to migrate the 
existing 40 CFR part 87 regulatory text to a new 40 CFR part 1031. Part 
of that effort includes clarifying portions of the regulatory text for 
ease of use. In the existing 40 CFR 87.42(c)(6), the regulatory text 
does not specifically spell out some required data, but instead relies 
on incorporation by reference for a detailed listing of required items. 
40 CFR 87.42(c)(6) references the data reporting provisions in ICAO's 
Annex 16, Volume II and lists the data from this Annex that is not 
required by the EPA's reporting requirement. For future ease of use, 
the EPA is proposing in the new 40 CFR 1031.150 to explicitly list all 
the required items rather than continuing the incorporation by 
reference approach in the existing reporting regulations. The reader is 
encouraged to consult the proposed 40 CFR 1031.150 text for a complete 
list of the required reporting items. However, as previously mentioned, 
this list contains all the currently required items as well as the HC, 
CO and NOX emission indices as proposed in the separate ICR 
renewal action. Finally, the EPA is proposing to incorporate by 
reference Appendix 8 of

[[Page 6345]]

Annex 16, Volume II, which outlines procedures used to estimate 
measurement system losses, which are a required element of the proposed 
reporting provisions.

V. Aggregate PM Inventory Impacts

    The number of aircraft landings and takeoffs (LTO) affects PM 
emissions that contribute to the local air quality near airports. The 
LTO emissions are defined as emissions between ground level and an 
altitude of about 3,000 feet. They are composed of emissions during 
departure operations (from taxi-out movement from gate to runway, 
aircraft take-off run and climb-out to 3,000 feet), and during arrival 
operations (emissions from approach at or below 3,000 feet down to 
landing on the ground and taxi-in from runway to gate). These LTO 
emissions directly affect the ground level air quality at the vicinity 
of the airport since they are within the local mixing height. Depending 
on the meteorological conditions, the emissions will be mixed with 
ambient air down to ground level, dispersed, and transported to areas 
downwind from the airport with elevated concentration levels.\102\
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    \102\ A local air quality ``. . . emissions inventory for 
aircraft focuses on the emission characteristics of this source 
relative to the vertical column of air that ultimately affects 
ground level pollutant concentrations. This portion of the 
atmosphere, which begins at the earth's surface and is simulated in 
air quality models, is often referred to as the mixing zone'' or 
mixing height. (See page 137.) The air in this mixing height is 
completely mixed and pollutants emitted anywhere within it will be 
carried down to ground level. (See page 143.) ``The aircraft 
operations of interest within the [mixing height] are defined as the 
[LTO] cycle.'' (See page 137.) The default mixing height in the U.S. 
is 3,000 feet. (EPA, 1992: Procedures for Emission Inventory 
Preparation--Volume IV: Mobile Sources, EPA420-R-92-009. Available 
at https://nepis.epa.gov (last accessed June 23, 2021).
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    As described earlier in Section III, aircraft PM emissions are 
composed of both volatile and nonvolatile PM components.\103\ Starting 
from an air and fuel mixture of 16.3 percent oxygen (O2), 
75.2 percent nitrogen (N2), and 8.5 percent fuel, an 
aircraft engine yields combustion products of 27.6 percent water 
(H2O), 72 percent carbon dioxide (CO2), and ~0.02 
percent sulfur oxide (SOX) with only 0.4 percent incomplete 
residual products which can be broken down to 84 percent nitrogen oxide 
(NOX), 11.8 percent carbon monoxide (CO), 4 percent unburned 
hydrocarbons (UHC), 0.1 percent PM and trace amount of other 
products.\104\ Although the PM emissions are a small fraction of total 
engine exhaust, the composition and morphology of PM are complex and 
dynamic. While the proposed emission test procedures focus only on 
measuring nonvolatile PM (black carbon), our emissions inventory 
includes estimates for volatile PM (organic, lubrication oil residues 
and sulfuric acid) as well.
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    \103\ ICAO: 2019, ICAO Environmental Report, Available at 
https://www.icao.int/environmental-protection/Documents/ICAO-ENV-Repor/t2019-F1-WEB%20(1).pdf (last accessed on November 15, 
2021,2021). See pages 100 and 101 for a description of non-volatile 
PM and volatile PM.
    ``At the engine exhaust, particulate emissions mainly consist of 
ultrafine soot or black carbon emissions. Such particles are called 
``non-volatile'' (nvPM). They are present at the high temperatures 
at the engine exhaust and they do not change in mass or number as 
they mix and dilute in the exhaust plume near the aircraft. The 
geometric mean diameter of these particles is much smaller than 
PM2.5 (geometric mean diameter of 2.5 Microns) and ranges 
roughly from 15nm to 60nm (0.06 Microns). These are classified as 
ultrafine particles (UFP).'' (See page 100.) ``The new ICAO standard 
is a measure to control the ultrafine non-volatile particulate 
matter emissions emitted at the engine exit . . .'' (See page 101.)
    ``Additionally, gaseous emissions from engines can also condense 
to produce new particles (i.e., volatile particulate matter--vPM), 
or coat the emitted soot particles. Gaseous emissions species react 
chemically with ambient chemical constituents in the atmosphere to 
produce the so called secondary particulate matter. Volatile 
particulate matter is dependent on these gaseous precursor 
emissions. While these precursors are controlled by gaseous emission 
certification and the fuel composition (e.g., sulfur content) for 
aircraft gas turbine engines, the volatile particulate matter is 
also dependent on the ambient air background composition.'' (See 
pages 100 and 101.)
    \104\ European Monitoring and Evaluation Programme/European 
Environment Agency, Air Pollutant Emission Inventory Guidebook 2019; 
Available at https://www.eea.europa.eu/themes/air/air-pollution-sources-1/emep-eea-air-/pollutant-/emission-/inventory-guidebook/emep (last accessed June 26, 2021).
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A. Aircraft Engine PM Emissions for Modeling

    To quantify the aircraft PM emissions for the purposes of 
developing or modeling an emissions inventory for this proposed 
rulemaking (for an inventory in the year 2017), we used an 
approximation method as described in Section V.A.1. For future emission 
inventories, this approximation method will not be needed for newly 
manufactured engines which will have measured PM emission indices (EIs) 
going forward. However, to accurately estimate the nvPM emissions at 
the engine exit for emission inventory purposes, loss correction 
factors for nvPM mass and nvPM number will need to be applied to the 
measured PM EIs due to particle losses in the nvPM sampling and 
measurement system. An improved approximation method as described in 
Section V.A.3 is expected to be used for modeling PM emissions of in-
service engines that do not have measured PM data. For the final 
rulemaking, we expect to develop an updated PM emissions inventory 
based on available measured PM EIs data with loss correction and the 
improved approximation method for engines without measured PM EIs.
1. Baseline PM Emission Indices
    Measured PM data was not available to calculate the 2017 inventory. 
Thus, to calculate the baseline aircraft engine PM emissions, we used 
the FOA3 (First Order Approximation Version 3.0) method defined in the 
SAE Aerospace Information Reports, AIR5715.\105\ For non-volatile PM 
mass, the FOA3 method is based on an empirical correlation of Smoke 
Number (SN) values and the non-volatile PM (nvPM) mass concentrations 
of aircraft engines. The nvPM mass concentration (g/m\3\) derived from 
SN can then be converted into an nvPM mass emission index (EI) in gram 
of nvPM per kg fuel using the method developed by Wayson et al,\106\ 
based on a set of empirically determined Air Fuel Ratios (AFR) and 
engine volumetric flow rates at the four ICAO LTO thrust settings (see 
Table IV-1). Subsequently, the nvPM mass EI can be used to calculate 
the nvPM mass for the four LTO modes with engine fuel flow rate and 
time-in-mode information. As the name suggests, the FOA3 method is a 
rough estimate, and it is only for nvPM mass.
---------------------------------------------------------------------------

    \105\ SAE Aerospace Information Reports, AIR5715, Procedure for 
the Calculation of Aircraft Emissions, 2009, SAE International.
    \106\ Wayson RL, Fleming GG, Iovinelli R. Methodology to 
Estimate Particulate Matter Emissions from Certified Commercial 
Aircraft Engines. J Air Waste Management Assoc. 2009 Jan 1; 59(1).
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    In addition, as described earlier (Sections III.A and IV), volatile 
PM and nvPM together make up total PM. The FOA3 method for volatile PM 
is based on the jet fuel organics \107\ and sulfur content. Since the 
total PM inventory is the emissions inventory we are estimating for 
this proposed rulemaking, we are including the volatile PM emission 
estimates from the FOA3 method in our emission inventory.
---------------------------------------------------------------------------

    \107\ In this context, organics refers to hydrocarbons in the 
exhaust that coat on existing particles or condense to form new 
particles after the engine exit.
---------------------------------------------------------------------------

2. Measured nvPM EIs for Inventory Modeling
    The measurement and reporting of engine EIs will improve the 
development of future engine emission inventories. As mentioned in 
Section IV, the regulatory compliance level is based on the amount of 
particulate that is directly measured by the instruments. The test 
procedures specify a sampling line that can be up to 35 meters long. 
This length results in significant particle loss in the measurement 
system, on the

[[Page 6346]]

order of 50 percent for nvPM mass and 90 percent for nvPM number.\108\ 
Further the particle loss is size dependent, and thus the losses will 
be dependent on the engine operating condition (e.g., idle vs take-off 
thrust), engine combustor design, and technology. To assess the 
emissions contribution of aircraft engines for inventory and modeling 
purposes, and subsequently for human health and environmental effects, 
it is necessary to know the emissions rate at the engine exit. Thus, 
the measured PM mass and PM number values must be corrected for system 
losses to determine the engine exit emissions rate.
---------------------------------------------------------------------------

    \108\ Annex 16 Vol. II Appendix 8 Note 2.
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    The EPA led the effort within the SAE E-31 committee to develop the 
methodology to correct for system losses. This effort at E-31 resulted 
in the development and publication of AIR 6504 and ARP 6481 describing 
how to correct for system losses. ICAO has incorporated this same 
procedure into Annex 16 Vol. II Appendix 8.
    The engine exit emissions rate, which is corrected for system 
losses, is specific to each measurement system and to each engine. The 
calculation is an iterative function based upon the measured nvPM mass 
and nvPM number values and the geometry of the measurement system. 
Manufacturers provide the corrected emissions values to the ICAO EDB 
and to the EPA.
    When calculating emissions inventories, these corrected EIs will be 
used rather than the values used to show compliance with emission 
standards. These measured EIs are only for the nonvolatile component of 
PM, and an approximation method will still be required for quantifying 
the volatile PM inventory.
3. Improvements to Calculated EIs
    The new version of the approximation method, known as FOA4, has 
been developed by CAEP to improve nvPM mass estimation and to extend 
the methodology to nvPM number based on the newly available PM 
measurement data.\109\ Since PM mass and PM number are two different 
measurement metrics of the same pollutant, PM, they can be converted to 
each other if the size and density distribution of the pollutant can be 
characterized.\110\ FOA4 was not used in the baseline emission rates 
for this proposed rulemaking.
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    \109\ ICAO: Second edition, 2020: Doc 9889, Airport Air Quality 
Manual. Order Number 9889. See Attachment D to Appendix 1 of Chapter 
3. Doc 9889 can be ordered from ICAO website: https://store.icao.int/en/airport-air-/quality-manual/-doc-9889 (last 
accessed June 28, 2021).
    \110\ Based on the newly available measurement data and inputs 
from technical experts in SAE E-31 Aircraft Exhaust Emissions 
Measurement Committee, CAEP has determined that a set of fixed 
geometric mean diameters (GMDs) of 20/20/40/40 nanometers for the 
four LTO modes (idle-taxi/approach/climbout/take-off) fits the data 
the best. Along with the assumptions of a log-normal size 
distribution, a geometric standard deviation of 1.8, and an 
effective density of 1,000 kg/m[caret]3 for the exhaust plume at the 
engine exit plane, nvPM mass EI and nvPM number EI of LTO mode k can 
be converted to each other.
---------------------------------------------------------------------------

    The calculation of volatile PM has not changed between FOA3 and 
FOA4 because no improved data or method has become available to inform 
improvements.

B. Baseline PM Emission Inventory

    The baseline PM emissions inventory used for this proposed rule is 
from the aviation portion of EPA's 2017 National Emissions Inventory 
(NEI).111 112 113 The NEI is compiled by EPA triennially 
based on comprehensive emissions data for criteria pollutants and 
hazardous air pollutants (HAPs) for mobile, point, and nonpoint 
sources. The mobile sources include aviation, marine, railroad, on-road 
vehicles, and nonroad engines. As described earlier in Section V.A, the 
aircraft emission estimates in this 2017 NEI (or the baseline PM 
emissions inventory) are based on the FOA instead of measured PM 
emissions data from aircraft engines proposed to be regulated by this 
rulemaking. For the final rulemaking, we anticipate potentially having 
an updated baseline PM emissions inventory based on measured data from 
numerous in-production engines (we would likely have PM data for nearly 
all in-production engines proposed to be regulated by this rulemaking).
---------------------------------------------------------------------------

    \111\ 2017 National Emissions Inventory: Aviation Component, 
Eastern Research Group, Inc., July 25, 2019, EPA Contract No. EP-C-
17-011, Work Order No. 2-19.
    \112\ See section 3.2 for airports and aircraft related 
emissions in the Technical Supporting Document for the 2017 National 
Emissions Inventory, January 2021 Updated Release; https://www.epa.gov/sites/production/files/2021-02/documents/nei2017_tsd_full_jan2021.pdf.
    \113\ https://www.epa.gov/air-emissions/-inventories/2017-/national-emissions-/inventory-nei-data.
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    The aviation emissions developed for the NEI include emissions 
associated with airport activities in commercial aircraft, air taxi 
aircraft,\114\ general aviation aircraft, military aircraft, auxiliary 
power units, and ground support equipment. All emissions from aircraft 
with gas turbine engines greater than 26.7 kN rated output from the 
aircraft categories described earlier, except military aircraft, are 
used in the emissions inventory for this proposed rule (which is a 
subset of the aviation emissions inventory). To estimate emissions, 
2017 activity data by states were compiled and supplemented with 
publicly available FAA data. The FAA activity data included 2017 T-100 
\115\ dataset, 2014 Terminal Area Forecast (TAF) \116\ data, 2014 Air 
Traffic Activity Data System (ATADS) \117\ data, and 2014 Airport 
Master Record (form 5010) \118\ data.\119\ The NEI used the FAA's 
Aviation Environmental Design Tool (AEDT) \120\ version 2d to estimate 
emissions for aircraft that were in the AEDT database. The NEI used a 
more general estimation methodology to account for emissions from 
aircraft types not available in AEDT by multiplying the reported 
activities by fleet-wide average emission factors of generic aircraft 
types (or by aircraft category--e.g., general aviation or air 
taxi).\121\
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    \114\ Air taxis fly scheduled service carrying passengers and/or 
freight, but they usually are smaller aircraft and operate on a more 
limited basis compared to the commercial aircraft operated by 
airlines.
    \115\ Title 14--Code of Federal Regulations--Part 241 Uniform 
System of Accounts and Reports for Large Certificated Air Carriers. 
T-100 Segment (All Carriers)--Published Online by Bureau of 
Transportation Statistics. https://www.transtats.bts.gov/Fields.asp?Table_ID=293. Accessed May 9, 2018.
    \116\ Federal Aviation Administration. Terminal Area Forecast 
(TAF). https://aspm.faa.gov/main/taf.asp. Accessed April 21, 2018.
    \117\ Federal Aviation Administration. ATADS: Airport 
Operations: Standard Report. https://aspm.faa.gov/opsnet/sys/Airport.asp. Accessed May 23, 2018.
    \118\ Federal Aviation Administration. 2009. Airport Master 
Record Form 5010. Published by GCR & Associates. https://www.gcr1.com/5010WEB/. Accessed May 21, 2009.
    \119\ The rationale for the use of multiple FAA activity 
databases is described in the 2017 NEI report (2017 National 
Emissions Inventory: Aviation Component, Eastern Research Group, 
Inc., July 25, 2019, EPA Contract No. EP-C-17-011, Work Order No. 2-
19. See section 3.2 for airports and aircraft related emissions in 
the Technical Supporting Document for the 2017 National Emissions 
Inventory, January 2021 Updated Release; https://www.epa.gov/sites/production/files/2021-02/documents/nei2017_tsd_full_jan2021.pdf, 
last accessed June 26, 2021.)
    \120\ AEDT is a software system that models aircraft performance 
in space and time to estimate fuel consumption, emissions, noise, 
and air quality consequences. It is available at https://aedt.faa.gov/ (last accessed on June 26, 2021).
    \121\ Ibid.
---------------------------------------------------------------------------

    For aircraft PM contribution in 2017 to total mobile PM emissions 
in counties and MSA's for the top 25 airports (inventories for aircraft 
with engines >26.7 kN), see Figure III-1 and Figure III-2 in Section 
III.E.
    As described earlier, the baseline emissions inventory is based on 
the total PM emissions, which includes both the nvPM and volatile PM 
components of total PM. The 2017 NEI does not provide inventories for 
these components of total PM. However, we estimate that nvPM is about 
70 percent

[[Page 6347]]

(range 51 percent to 72 percent based on modal EIs of a sample engine) 
of the total PM.\122\ We intend to improve this estimate for the final 
rulemaking. Applying the nvPM percentage (or fraction) to the total 
fleet-wide baseline PM inventory, or the 2017 NEI PM inventory for 
aircraft with gas turbine engines greater than 26.7 kN, would better 
enable us to estimate the nvPM portion of the aircraft contribution to 
total mobile PM accordingly.
---------------------------------------------------------------------------

    \122\ ICAO: Second edition, 2020: Doc 9889, Airport Air Quality 
Manual. Order Number 9889. See Attachment D to Appendix 1 of Chapter 
3. Doc 9889 can be ordered from ICAO website: https://store.icao.int/en/airport-air-/quality-manual-/doc-9889 (last 
accessed June 28, 2021).
---------------------------------------------------------------------------

C. Projected Reductions in PM Emissions

    Due to the technology-following nature of the PM standards, the 
proposed in-production and new type standards would not result in 
emission reductions below current levels of engine emissions. The 
proposed in-production standards for both PM mass and PM number, which 
would be set at levels where all in-production engines meet the 
standards, would not affect any in-production engines as shown in 
Figure IV-1 and Figure IV-2. Thus, the proposed standards are not 
expected to produce any emission reductions, beyond the business-as-
usual fleet turn over that would occur absent of the proposed 
standards. The EPA projects that all future new type engines would meet 
the proposed new type standards. There are a few in-production engines 
that do not meet the proposed new type standards, but since in-
production engines would not be subject to these new type standards, 
engine manufacturers would not be required to make any improvements to 
these engines to meet the standards. Therefore, there would be no 
emission reductions from the proposed new type standards.
    Most of the in-production engines that do not meet the proposed new 
type standards are older engines that already have replacement in-
production engines that would meet the proposed new type standards. 
There is only one newer in-production engine (an engine that recently 
started being manufactured) that would not meet the proposed new type 
standards and does not currently have a replacement in-production 
engine. Market forces might drive the manufacturer of this in-
production engine to make some improvements to meet the proposed new 
type standards, but even in this scenario, this manufacturer would 
still have the option to retest the engine and/or make minor 
adjustments or design modifications to improve the test result. The 
other option for this manufacturer would be to bring forward its next 
generation new type engine to the market a few years earlier than 
currently planned.123 124 Since the new type standards would 
not apply to the in-production engines, this manufacturer could 
continue producing and selling its one in-production engine that does 
not meet the proposed new type standards. Further details on market 
forces are provided later in Section VI.A. In conclusion, when 
considering the proposed new type standards in the context of the in-
production engines that already have a replacement engine or the one 
in-production engine that does not, there would be no emission 
reductions from the proposed new type standards.
---------------------------------------------------------------------------

    \123\ https://www.rolls-royce.com/products-and-services/civil-aerospace/future-products.aspx#/; last accessed on June 26, 2021.
    \124\ https://aviationweek.com/mro/rolls-royce-/considers-ultrafan-/development-pause; last accessed on June 26, 2021.
---------------------------------------------------------------------------

VI. Technological Feasibility and Economic Impacts

    As described earlier, we are proposing PM mass concentration, PM 
mass, and PM number standards that match ICAO's standards. As discussed 
previously in Section V.C, for in-production aircraft engines, the 2017 
ICAO PM maximum mass concentration standard and the 2020 ICAO PM mass 
and number standards are set at emission levels where all in-production 
engines meet these standards. Thus, there would not be costs or 
emission reductions associated with the proposed standards for in-
production engines. For new type engines, the 2020 ICAO PM mass and 
number standards are set at more stringent emission levels compared to 
the PM mass and number standards for in-production engines, but nearly 
all in-production engines meet these new type standards. In addition, 
in-production engines would not be required to meet these new type 
standards. Only new type engines would need to comply with the new type 
standards. The EPA projects that all new type engines entering into 
service into the future will meet these PM mass and number standards. 
Thus, EPA expects that there would not be costs and emission reductions 
from the proposed standards for new type engines. In addition, 
following the final rulemaking for the PM standards, the FAA would 
issue a rulemaking to enforce compliance to these standards, and any 
anticipated certification costs for the PM standards would be accounted 
for in the FAA rulemaking.

A. Market Considerations

    Aircraft and aircraft engines are sold around the world, and 
international aircraft emission standards help ensure the worldwide 
acceptability of these products. Aircraft and aircraft engine 
manufacturers make business decisions and respond to the international 
market by designing and building products that conform to ICAO's 
international standards. However, ICAO's standards need to be 
implemented domestically for products to prove such conformity. 
Domestic action through EPA rulemaking and subsequent FAA rulemaking 
enables U.S. manufacturers to obtain internationally recognized U.S. 
certification, which for the proposed PM standards would ensure type 
certification consistent with the requirements of the international PM 
emission standards. This is important, as compliance with the 
international standards (via U.S. type certification) is a critical 
consideration in aircraft manufacturer and airlines' purchasing 
decisions. By implementing the requirements in the United States that 
align with ICAO standards, any question regarding the compliance of 
aircraft engines certificated in the United States would be removed. 
The proposed rule would facilitate the acceptance of U.S. aircraft 
engines by member States, aircraft manufacturers, and airlines around 
the world. Conversely, without this domestic action, U.S. aircraft 
engine manufacturers would be at a competitive disadvantage compared 
with their international competitors.
    In considering the aviation market, it is important to understand 
that the international PM emission standards were predicated on 
demonstrating ICAO's concept of technological feasibility; i.e., that 
manufacturers have already developed or are developing improved 
technology that meets the ICAO PM standards, and that the new 
technology will be integrated in aircraft engines throughout the fleet 
in the time frame provided before the standards' effective date. 
Therefore, the EPA projects that these proposed standards would impose 
no additional burden on manufacturers.

B. Conceptual Framework for Technology

    The long-established ICAO/CAEP terms of reference were taken into 
account when deciding the international PM standards, principal among 
these being technical feasibility. For the ICAO PM standard setting, 
technical feasibility refers to refers to any

[[Page 6348]]

technology demonstrated to be safe and airworthy proven to Technical 
Readiness Level \125\ (TRL) 8 and available for application over a 
sufficient range of newly certificated aircraft.\126\ This means that 
the analysis that informed the international standard considered the 
emissions performance of aircraft engines assumed to be in-production 
on the implementation date for the PM mass and number standards, 
January 1, 2023.\127\ The analysis included the current in-production 
fleet and engines scheduled for entry into the fleet by this date. 
(ICAO/CAEP's analysis was completed in 2018 and considered at the 
February 2019 ICAO/CAEP meeting.)
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    \125\ TRL is a measure of Technology Readiness Level. CAEP has 
defined TRL8 as the ``actual system completed and `flight qualified' 
through test and demonstration.'' TRL is a scale from 1 to 9, TRL1 
is the conceptual principle, and TRL9 is the ``actual system `flight 
proven' on operational flight.'' The TRL scale was originally 
developed by NASA. ICF International, CO2 Analysis of CO2-Reducing 
Technologies for Aircraft, Final Report, EPA Contract Number EP-C-
12-011, see page 40, March 17, 2015.
    \126\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP11. It is found on page 26 of the English 
Edition of the ICAO Products & Services 2021 Catalog and is 
copyright protected: Order No. 10126. For purchase and available at: 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The statement on technological 
feasibility is located in Appendix C of Agenda Item 3 of this report 
(see page 3C-4, paragraph 2.2).
    \127\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP11. It is found on page 26 of the English 
Edition of the ICAO Products & Services 2021 Catalog and is 
copyright protected: Order No. 10126. For purchase and available at: 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). The summary of technological 
feasibility and cost information is located in Appendix C to the 
report on Agenda Item 3 (starting on page 3C-1).
---------------------------------------------------------------------------

C. Technological Feasibility

    The EPA and FAA participated in the ICAO analysis that informed the 
adoption of the international aircraft engine PM emission standards. A 
summary of that analysis was published in the report of ICAO/CAEP's 
eleventh meeting (CAEP/11),\128\ which occurred in February 2019. 
However, due to the commercial sensitivity of much of the data used in 
the ICAO analysis, the publicly available, published version of the 
ICAO report of the CAEP/11 meeting only provides limited supporting 
data for the ICAO analysis. Separately from this ICAO analysis and the 
CAEP/11 meeting report, information on technology for the control of 
aircraft engine PM emissions is provided in an Independent Expert 
Review document on technology goals for engines and aircraft, which was 
published in 2019.\129\ Although this ICAO document is primarily used 
for setting goals, and is not directly related to ICAO's adoption of 
the PM emission standards, information from the Independent Expert 
Review is helpful in understanding the state of aircraft engine 
technology.
---------------------------------------------------------------------------

    \128\ Ibid.
    \129\ ICAO, 2019: Independent Expert Integrated Technology Goals 
Assessment and Review for Engines and Aircraft, Document 10127. It 
is found on page 32 of the English Edition of the ICAO Products & 
Services 2021 Catalog and is copyright protected; Order No. 10127. 
For purchase and available at: https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed November 15, 2021).
---------------------------------------------------------------------------

    The 2019 ICAO Independent Expert Review document indicates that new 
technologies aimed at reducing aircraft engine NOX also 
resulted in an order of magnitude reduction in nvPM mass and nvPM 
number in comparison to most in-service engines.\130\ (As described 
earlier in Section IV.D.1, only nvPM emissions would be measured in the 
proposed test procedure for the proposed standards.) Specifically, the 
current lean-burn engines and some advanced Rich-Quench-Lean (RQL) 
engines \131\ developed for the purpose of achieving low NOX 
emissions coincidentally provide order of magnitude reductions in nvPM 
emissions in comparison to existing RQL engines. However, achieving 
these levels of nvPM emissions will be more difficult for physically 
smaller-sized engines due to technical constraints.\132\ In addition, 
some previous generation engines that are in production meet the 
proposed new type standards, which match the ICAO standards, with 
considerable margin. When considering the nvPM emission levels for 
current in-production engines and those engines expected to be in 
production by the effective date of the ICAO standard, January 1, 2023, 
the lean-burn, advanced RQL, and some previous generation technologies 
(with relatively low levels of nvPM emissions) of many of the engines 
demonstrate that the proposed standards, which match ICAO standards, 
are technologically feasible.
---------------------------------------------------------------------------

    \130\ Ibid. See page 8 of this document.
    \131\ For lean-burn engines, ``. . . enough air is introduced 
with the fuel from the injector so that it is never overall rich. In 
aviation combustors, the fuel is not premixed and pre-vaporized and 
in the microscopic region around each droplet, the mixture can be 
close to stoichiometric. However, the mixture remains lean 
throughout the combustor and temperature does not approach the 
stoichiometric value. . . . In a lean-burn combustor, the peak 
temperatures are not as high, so NOX is low.'' (See pages 
47 and 48.) From previous generation rich-burn to lean-burn 
technology, an order of magnitude improvement in nvPM mass and nvPM 
number is likely for the LTO cycle. (See pages 57 and 58.)
    For Rich-Quench-Lean (RQL) engines, ``. . . the fuel first burns 
rich so there is little oxygen free to form NOX. Dilution 
air is introduced to take the mixture as quickly as possible through 
stoichiometric region (when it briefly gets very hot) to a cooler, 
lean state.'' (See page 47.) Potentially, an order of magnitude 
improvement in nvPM mass and nvPM number could be achieved for the 
LTO cycle from previous generation rich-burn to advanced rich-burn 
combustor technology. (See pages 57 and 58.)
    ICAO, 2019: Independent Expert Integrated Technology Goals 
Assessment and Review for Engines and Aircraft, Document 10127. It 
is found on page 32 of the English Edition of the ICAO Products & 
Services 2021 Catalog and is copyright protected; Order No. 10127. 
For purchase and available at: https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed November 15, 2021). See 
pages, 47, 48, 57, and 58 of this document.
    \132\ For example, the relatively small combustor space and 
section height of these engines creates constraints on the use of 
low NOX combustor concepts, which inherently require the 
availability of greater flow path cross-sectional area than 
conventional combustors. Also, fuel-staged combustors need more fuel 
injectors, and this need is not compatible with the relatively 
smaller total fuel flows of lower thrust engines. (Reductions in 
fuel flow per nozzle are difficult to attain without having clogging 
problems due to the small sizes of the fuel metering ports.) In 
addition, lower thrust engine combustors have an inherently greater 
liner surface-to combustion volume ratio, and this requires 
increased wall cooling air flow. Thus, less air will be available to 
obtain acceptable turbine inlet temperature distribution and for 
emissions control. U.S. EPA, 2012: Control of Air Pollution from 
Aircraft and Aircraft Engines; Emission Standards and Test 
Procedures; Final Rule, 77 FR 36342, June 18, 2012. (See page 
36353.)
---------------------------------------------------------------------------

D. Costs Associated With the Proposed Rule

    EPA does not anticipate new technology costs due to the proposed 
rule. Nevertheless, it is informative to describe the elements of cost 
analysis for technology improvements, such as non-recurring costs 
(NRC), certification costs, and recurring costs. As described in the 
summary of the ICAO analysis for the PM emission standards,\133\ 
generally, CAEP considered certain factors as pertinent to the non-
recurring cost estimates of a technology level for engine changes for 
PM mass and number. The first technology level was regarded as a minor 
change, and it could include minor improvements, and additional testing 
and re-certification of emissions. The PM mass and number

[[Page 6349]]

emission reductions for the first technology level would be from 1 to 
10 percent, and the estimated associated costs would be $15 million. 
The second technology level was considered a scaled proven technology. 
At this level an engine manufacturer applies its best-proven, 
combustion technology that was already been certificated in at least 
one other engine type to another engine type. This second technology 
level would include substantial modeling, design, combustion rig 
testing, modification and testing of development engines, and flight-
testing. The PM mass and number emission reductions for the second 
technology level would be a minimum of 10 percent, and the estimated 
associated costs would be $150 million and $250 million, respectively 
for PM mass and number. The third technology level was regarded as new 
technology or current industry best practice, and it was considered 
where a manufacturer has no proven technology that can be scaled to 
provide a solution and some technology acquisition activity is 
required. (One or more manufacturers have demonstrated the necessary 
technology, while the remaining manufacturers would need to acquire the 
technology to catch up.) The PM mass and number emission reductions for 
the third technology level would be a minimum of 25 percent, and the 
estimated costs would be $500 million. As described earlier, since all 
in-production engines meet the in-production standards and nearly all 
in-production engines meet these new type standards--even though they 
do not have to, we believe that there would not be costs, nor emission 
reductions, from the proposed rule. Also, because current in-production 
engines would not be required to make any changes under this proposed 
rule, there will not be any adverse impact on noise and safety of these 
engines. Likewise, the noise and safety of future type designs should 
not be adversely impacted by compliance with these proposed new type 
standards since all manufacturers currently have engines that meet that 
level.
---------------------------------------------------------------------------

    \133\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP11. It is found on page 26 of the English 
Edition of the ICAO Products & Services 2021 Catalog and is 
copyright protected: Order No. 10126. For purchase and available at: 
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last 
accessed November 15, 2021). See pages 3C-17 to 3C-19 in Appendix C 
to the report on Agenda Item 3 (starting on page 3C-1).
    U.S. EPA, 2012: Control of Air Pollution from Aircraft and 
Aircraft Engines; Emission Standards and Test Procedures; Final 
Rule, 77 FR 36342, June 18, 2012. (See pages 36375 and 36376.)
---------------------------------------------------------------------------

    Following the final rulemaking for the PM standards, the FAA would 
issue a rulemaking to enforce compliance to these standards, and any 
anticipated certification costs for the PM standards would be estimated 
by FAA. The EPA is not making any attempt to quantify the costs 
associated with certification actions required by the FAA to enforce 
these standards.
    As described earlier, manufacturers have already developed or are 
developing technologies to respond to ICAO standards that are 
equivalent to the proposed standards, and they will comply with the 
ICAO standards in the absence of U.S. regulations. Also, domestic 
implementation of the ICAO standards would potentially provide for a 
cost savings to U.S. manufacturers since it would enable them to 
certify their aircraft engine (via subsequent FAA rulemaking) 
domestically instead of having to certificate with a foreign authority 
(which would occur without this EPA rulemaking). If the proposed PM 
standards, which would match the ICAO standards, are not ultimately 
adopted in the United States, U.S. civil aircraft engine manufacturers 
will have to certify to the ICAO standards at higher costs because they 
will have to move their entire certification program(s) to a non-U.S. 
certification authority.\134\ Thus, there would be no new certification 
costs for the proposed rule, and the proposed rule could potentially 
provide a costs savings.
---------------------------------------------------------------------------

    \134\ In addition, European authorities charge fees to aircraft 
engine manufacturers for the certification of their engines, but FAA 
does not charge fees for certification.
---------------------------------------------------------------------------

    For the same reasons there would be no NRC and certification costs 
for the proposed rule as discussed earlier, there would be no recurring 
costs (recurring operating and maintenance costs) for the proposed 
rule. The elements of recurring costs would include additional 
maintenance, material, labor, and tooling costs.
    As described earlier in Section IV.E, the EPA is proposing to 
formally incorporate the PM aspects of the existing information 
collection request (ICR) into the CFR (or regulations) in the proposed 
section 1031.150. This proposed action would not create a new 
requirement for the manufacturers of aircraft engines. Instead, it 
would simply incorporate the existing reporting requirements into the 
CFR for ease of use by having all the reporting requirements readily 
available in the CFR. Thus, this proposed action would not create new 
costs.

E. Summary of Benefits and Costs

    The proposed standards match the ICAO standards, and ICAO 
intentionally established its standards at a level which is technology 
following. In doing this, ICAO adheres to its technical feasibility 
definition for the standard setting process, which is meant to consider 
the emissions performance of existing in-production engines and those 
engines expected to be in production by 2023. Independent of the ICAO 
standards all engines currently manufactured will meet the ICAO in-
production standards, and nearly all these same engines will meet the 
new type standards--even though these new type standards do not apply 
to in-production engines. Therefore, there would be no costs and no 
additional benefits from complying with these proposed standards--
beyond the benefits from maintaining consistency or harmonizing with 
the international standards and preventing backsliding by ensuring that 
all in-production and new type engines have at least the PM emission 
levels of today's aircraft engines.

VII. Technical Amendments

    In addition to the PM-related regulatory provisions discussed 
earlier in this document, the EPA is proposing technical amendments to 
the regulatory text that apply more broadly than to just the proposed 
new PM standards. First, the EPA is proposing to migrate the existing 
aircraft engine emissions regulations from 40 CFR part 87 to a new 40 
CFR part 1031. Along with this migration, the EPA is proposing to 
restructure the regulations to allow for better ease of use and allow 
for more efficient future updates. The EPA is also proposing to delete 
some regulatory provisions and definitions that are unnecessary, as 
well as make several other minor technical amendments to the 
regulations. Finally, as explained in more detail below, EPA is also 
proposing revisions to 40 CFR part 87 to provide continuity during the 
transition of 40 CFR part 87 to 40 CFR part 1031.

A. Migration of Regulatory Text to New Part

    In the 1990s, the EPA began an effort to migrate all 
transportation-related air emissions regulations to new parts, such 
that all mobile source regulations are contained in a single group of 
contiguous parts of the CFR. In addition to the migration, that effort 
has included clarifications to regulations and improvements to the ease 
of use through plain language updates and restructuring. To date, the 
aircraft engine emission regulations contained in 40 CFR part 87 are 
the only mobile source emission regulations which have not undergone 
this migration and update process.
    The current 40 CFR part 87 was initially drafted in the early 1970s 
and has seen numerous updates and revisions since then. This has led to 
a set of aircraft engine emission regulations that is difficult to 
navigate and contains numerous unnecessary provisions. Further, the 
current structure of the regulations would make the adoption of the PM 
standards proposed in this document, as well as any future standards 
the EPA may

[[Page 6350]]

propose, difficult to incorporate into the existing regulatory 
structure.
    Therefore, the EPA is proposing to migrate the existing aircraft 
engine regulations from 40 CFR part 87 to a new 40 CFR part 1031, 
directly after the airplane GHG standards contained in 40 CFR part 
1030. In the process, the EPA is proposing to restructure, streamline 
and clarify the regulatory provisions for ease of use and to facilitate 
more efficient future updates. Finally, the EPA is proposing to delete 
unnecessary regulatory provisions, which are discussed in detail in the 
next section.
    This regulatory migration and restructuring effort is not intended 
to change any substantive provision of the existing regulatory 
provisions. Thus, the EPA is not seeking comment on the proposed 
migration and restructuring, except in cases where a commenter believes 
that the proposed structure unintentionally changes the meaning of the 
regulatory text. The following two sections on the deletion of 
unnecessary provisions and additional technical amendments specify 
areas where the EPA invites comment on proposed changes to the 
regulations separate from the proposed migration and restructuring.
    As is noted in the amendatory text to the proposed regulations, the 
EPA is proposing to make this transition effective on January 1, 2023. 
The new 40 CFR part 1031 would become effective (i.e., be incorporated 
into the Code of Federal Regulations) 30 days following the publication 
of the final rule in the Federal Register. However, the applicability 
language in the proposed section 1031.1 indicates that the new 40 CFR 
part 1031 would apply to engines subject to the standards beginning 
January 1, 2023. Prior to January 1, 2023, the existing 40 CFR part 87 
would continue to apply. On January 1, 2023, the existing 40 CFR part 
87 would be replaced with a significantly abbreviated version of 40 CFR 
part 87 whose sole purpose would be to direct readers to the new 40 CFR 
part 1031. Additionally, a reference in the current 40 CFR part 1030 to 
40 CFR part 87 would be updated to reference 40 CFR part 1031 at that 
time. The purpose of the abbreviated 40 CFR part 87 is to accommodate 
any references to 40 CFR part 87 that currently exist in the type 
certification documentation and advisory circulars issued by the FAA, 
as well as any other references to 40 CFR part 87 that currently exist 
elsewhere. Since it would be extremely difficult to identify and update 
all such documents prior to January 1, 2023, the EPA is instead 
proposing to adopt language in 40 CFR part 87 that simply states the 
provisions relating to a particular section of the 40 CFR part 87 apply 
as described in a corresponding section of the proposed new 40 CFR part 
1031.

B. Deletion of Unnecessary Provisions

    As previously mentioned, the existing aircraft engine emissions 
regulations contain some unnecessary provisions which the EPA proposes 
to delete. These proposed deletions include transitional exemption 
provisions that are no longer available, several definitions, and some 
unnecessary language regarding the Secretary of the Department of 
Transportation, as detailed in the following paragraphs.
    The EPA is proposing to not migrate the current 40 CFR 87.23(d)(1) 
and (3) to the new 40 CFR part 1031. Both these paragraphs contain 
specific phase-in provisions available for a short period after the 
Tier 6 NOX standards began to apply, and their availability 
as compliance provisions ended on August 31, 2013. Thus, they are no 
longer needed. It should be noted that while the EPA is proposing to 
effectively delete these provisions by not migrating them to the 
proposed new 40 CFR part 1031, the underlying standards referred to in 
these provisions (i.e., the Tier 4 and 6 NOx standards) are proposed to 
remain unchanged. Thus, the underlying certification basis for any 
engines certificated under these provisions will remain intact.
    The EPA is also proposing to delete a number of definitions from 
the current 40 CFR part 87 as it is migrated to the new proposed Part 
1031 for two reasons. First, in the effort to streamline and clarify 
the regulations, some of these definitions have effectively been 
incorporated directly into the regulatory text where they are used, 
making a standalone definition unnecessary and redundant. Second, some 
of these definitions are simply not needed for any regulatory purpose 
and are likely artifacts of previous revisions to the regulations 
(e.g., where a regulatory provision was deleted but the associated 
definition was not).
    The definitions that the EPA proposes to delete and the reasons for 
the proposed deletions are listed in Table VII-1.

   Table VII-1--List of Terms for Which Definitions Are Proposed To Be
                                 Deleted
------------------------------------------------------------------------
               Term                     Reason for proposed deletion
------------------------------------------------------------------------
Act...............................  Not used in the regulatory text.
Administrator.....................  No longer needed as not used in
                                     proposed revised and streamlined
                                     regulatory text.
Class TP..........................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Class TF..........................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Class T3..........................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Class T8..........................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Class TSS.........................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Commercial aircraft...............  No longer needed as not used in
                                     proposed revised and streamlined
                                     regulatory text.
Commercial aircraft gas turbine     No longer needed as not used in
 engine.                             proposed revised and streamlined
                                     regulatory text.
Date of introduction..............  Unnecessary definition that is not
                                     used in existing regulatory text
                                     and not needed in revised
                                     regulatory text.
Engine............................  For regulatory purposes, definition
                                     of engine not needed given existing
                                     definitions of Aircraft engine,
                                     Engine model, and Engine sub-model.
In-use aircraft gas turbine engine  No longer needed in light of
                                     proposed deletion of unnecessary
                                     provisions and technical amendments
                                     to fuel venting requirements.
Military aircraft.................  Not needed as regulatory text
                                     applies to commercial engines.
Operator..........................  No longer needed as not used in
                                     proposed revised and streamlined
                                     regulatory text.
Production cutoff or the date of    No longer needed with proposed
 production cutoff.                  deletion of unnecessary exemption
                                     provisions and streamlining of
                                     exemption regulatory text.
Tier 0............................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Tier 2............................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Tier 4............................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Tier 6............................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.
Tier 8............................  No longer needed as definition was
                                     effectively incorporated into
                                     regulatory text during proposed
                                     migration.

[[Page 6351]]

 
U.S.-registered aircraft..........  Unnecessary term that is not used in
                                     the regulatory text.
------------------------------------------------------------------------

    The EPA is also proposing to not migrate the current 40 CFR 87.3(b) 
to the new 40 CFR part 1031, which in effect will result in its 
deletion. This paragraph is simply a restatement of an obligation 
directly imposed under the Clean Air Act the Secretary shall issue 
regulations to assure compliance with the regulations issued under the 
Act. This is not a regulatory requirement related to the rest of the 
part, and as such it is not needed in the proposed 40 CFR part 1031.

C. Other Technical Amendments and Minor Changes

    In addition to the migration of the regulations to a new part and 
the removal of unnecessary provisions just discussed, the EPA is 
proposing some minor technical amendments to the regulations.
    The EPA is proposing to add definitions for ``Airplane'' and 
``Emission index.'' Both these terms are used in the current aircraft 
engine emissions regulations, but they are currently undefined. The new 
proposed definitions would help provide clarity to the provisions that 
utilize those terms.
    The EPA proposes to modify the definitions for ``Exception'' and 
``Exemption.'' The current definitions of these terms in Part 87.1 go 
beyond simply defining the terms and contain what could more accurately 
be described as regulatory requirements stating what provisions an 
excepted or exempted engine must meet. These portions of the 
definitions, which are more accurately described as regulatory 
requirements, are proposed to be moved to the introductory text in 
1031.15 and 1031.20, as applicable. These proposed changes are in no 
way intended to change any regulatory requirement applicable to 
excepted or exempted engines. Rather, they are proposed simply to more 
clearly separate definitions from the related regulatory requirements.
    The EPA is proposing to not migrate the existing 87.42(d) to the 
proposed new Part 1031, which in effect will result in the deletion of 
this provision. This paragraph in the annual production report section 
regards the identification and treatment of confidential business 
information (CBI) in manufacturers' annual production reports. The EPA 
is instead relying on the existing CBI regulations in 40 CFR 1068.10 
(as referenced in the proposed 1031.170). This proposed change would 
have no impact on the ability of manufacturers to make claims of CBI, 
or in the EPA's handling of such claims. However, it would assure a 
more consistent treatment of CBI across mobile source programs.
    The EPA is proposing a minor change to the existing emissions 
requirements for spare engines, as found in 87.50(c)(2). In the 
proposed regulatory text for 1031.20(a), the EPA is proposing to delete 
the existing provision that a spare engine is required to meet 
standards applicable to Tier 4 or later engines (currently contained in 
40 CFR 87.50(c)(2)). The EPA is proposing to retain and migrate to part 
1031 the requirement in 40 CFR 87.50(c)(3) such that a spare engine 
would need to be certificated to emission standards equal to or lower 
than those of the engines they are replacing, for all regulated 
pollutants. This proposed deletion of 40 CFR 87.50(c)(2) would align 
with ICAO's current guidance on the emissions of spare engines and is 
consistent with U.S. efforts to secure the highest practicable degree 
of uniformity in aviation regulations and standards. The EPA does not 
believe this proposed change would have any impact on current industry 
practices. Deleting the provision currently in 40 CFR 87.50(c)(2) would 
leave in place the requirement that any new engine manufactured as a 
spare would need to be at least as clean as the engine it is replacing 
(as stated in the current 40 CFR 87.50(c)(3)), but with no requirement 
that it meet standards applicable to Tier 4 or later engines. Thus, 
under this proposed deletion a new spare engine could, in theory, be 
manufactured that only met pre-Tier 4 standards. The Tier 4 standards 
became effective in 2004, so the proposed deletion would only impact 
spare engines manufactured to replace engines manufactured roughly 
before 2004. It is extremely unlikely that a manufacturer would build a 
new engine as a replacement for such an old design as it would be very 
disruptive to the manufacturing of current designs for new aircraft. 
Rather, it is common practice that spares for use in replacing older 
engines would not be newly manufactured engines of an old design, but 
engines that have been taken from similar aircraft that have been 
retired. The EPA does not believe that any engines would be 
manufactured to pre-Tier 4 designs for use as spare engines given 
current practices. Thus, the EPA does not believe that this proposed 
deletion of 40 CFR 87.50(c)(2) for the purposes of uniformity would 
have any practical impact on current industry practices.
    The EPA is proposing to align the applicability of smoke number 
standards for engines used in supersonic airplanes with ICAO's 
applicability. The EPA adopted emission standards for engines used on 
supersonic airplanes in 2012.\135\ Those standards were equivalent to 
ICAO's existing standards with one exception. ICAO's emission standards 
fully apply to all engines to be used on supersonic airplanes, 
regardless of rated output. In an apparent oversight, the EPA only 
applied the smoke number standards to engines of greater than or equal 
to 26.7 kN rated output. Thus, the EPA is proposing to apply smoke 
number standards to include engines below 26.7 kN rated output for use 
on supersonic airplanes which are equivalent to ICAO's provisions. This 
change is proposed consistent with U.S. efforts to secure the highest 
practicable degree of uniformity in aviation regulations and standards 
and would have no practical impact on engine manufacturers. The EPA is 
currently unaware of any engines in production which could be used on 
supersonic airplanes, and those being developed for application to 
future supersonic airplanes are expected to be well above 26.7 kN rated 
output, and thus, they would be covered by the existing smoke number 
standard. Throughout its regulations, the EPA is proposing to align 
with ICAO regarding a common rated output threshold for emission 
regulations. The applicability and/or stringency of several aircraft 
engine emission standards can be different depending on whether an 
engine's rated output is above or below 26.7 kN. In the ICAO 
regulations, the threshold is consistently stated as either greater 
than, or less than or equal to 26.7 kN. In the current 40 CFR part 87, 
the equal to portion of the threshold is applied inconsistently. In 
some cases, it

[[Page 6352]]

is expressed as less than, and greater than or equal to. In other 
cases, it is expressed as greater than, and less than or equal to. The 
proposal is to make all instances in the proposed Part 1031 consistent 
with ICAO, i.e., greater than, and less than or equal to. As there are 
no current engines with a rated output of exactly at 26.7 kN, this 
proposed change would have no practical impact. However, it is 
consistent with U.S. efforts to secure the highest practicable degree 
of uniformity in aviation regulations and standards.
---------------------------------------------------------------------------

    \135\ 77 FR 36342, June 18, 2012.
---------------------------------------------------------------------------

    The EPA is proposing to incorporate by reference Appendix 1 of 
ICAO's Annex 16, Volume II. This appendix deals with the determination 
of a test engine's reference pressure ratio, and its exclusion from the 
U.S. regulations was an oversight. Other Annex 16, Volume II appendices 
which contain test procedures, fuel specifications, and other 
compliance-related provisions have been incorporated by reference into 
the U.S. regulations for many years, and it is important to correct 
this oversight so that the complete testing and compliance provisions 
are clear.
    The EPA is proposing to streamline, restructure, and update the 
exemption provisions currently in 40 CFR 87.50. First, this section 
contains provisions regarding exemptions, exceptions, and annual 
reporting provisions relating to exempted and excepted engines. The EPA 
is proposing to migrate the exceptions section concerning spare engines 
(87.50(c)) to its own new section 1031.20(a), with the proposed changes 
discussed earlier in this section. The provisions regarding the annual 
reporting of exempted and excepted engines are proposed to be 
incorporated into the new annual reporting section 1031.150. These 
reporting provisions otherwise remain unchanged. Section 87.50(a), 
regarding engines installed on new aircraft, and section 87.50(b), 
regarding temporary exemptions based on flights for short durations at 
infrequent intervals, are proposed to be migrated to a new section 
1031.15. The temporary exemptions provisions remain unchanged, with the 
exception of the addition of ``of Transportation'' after ``Secretary'' 
in 1031.15(b)(4) to provide additional clarity. The proposed changes to 
the exemptions for engines installed on new aircraft are a bit more 
extensive, as discussed in the next paragraph.
    In 2012, the EPA adopted new exemption provisions specifically to 
provide flexibility during the transition to Tier 6 and Tier 8 
NOX standards.\136\ These provisions were only available 
through December 31, 2016 and are proposed to be deleted, as previously 
discussed. However, during the adoption of those transitional 
flexibilities, the EPA inadvertently replaced the existing exemption 
provisions with the new transitional provisions rather than appending 
the transitional provisions to the existing ones. This left 87.50 with 
no general exemption language, only those provisions specific to the 
newly adopted NOX standards. Given that the transitional 
NOX exemption provisions have expired and are now obsolete, 
the EPA is proposing to delete them rather than migrate them to the new 
1031.15. The EPA is further proposing to restore the general exemption 
authority that was inadvertently removed in 2012. In a recent action 
which established GHG standards for airplanes, the EPA adopted much 
more streamlined exemption provisions for airplanes in consultation 
with the FAA.\137\ The EPA is proposing to adopt similarly streamlined 
general exemption provisions for aircraft engines as well, as contained 
in the proposed 1031.15(a).
---------------------------------------------------------------------------

    \136\ 77 FR 36342, June 18, 2012.
    \137\ 86 FR 2136, January 11, 2021.
---------------------------------------------------------------------------

    The EPA is proposing some changes relative to the prohibition on 
fuel venting. The fuel venting standard is intended to prevent the 
discharge of fuel to the atmosphere following engine shutdown, as 
explicitly stated in 40 CFR 87.11(a). The existing definition for fuel 
venting emissions in 87.1 defines fuel venting emissions as fuel 
discharge during all normal ground and flight operations. As the 
standard section itself limits the applicability only to venting that 
occurs following engine shutdown, consistent with ICAO's fuel venting 
provisions, the EPA is proposing to delete the definition for fuel 
venting emissions as both unnecessary and contradictory to the actual 
requirement. Further, the EPA is proposing to add the word ``liquid'' 
before fuel in the fuel venting requirements, consistent with the ICAO 
fuel venting provisions. Neither of these proposed changes would have 
any practical effect on the requirements on engine manufacturers, but 
these changes both clarify the requirements and fully align with ICAO 
standards and recommended practices, consistent with U.S. efforts to 
secure the highest practicable degree of uniformity in aviation 
regulations and standards.
    The EPA is proposing to modify the applicability date language 
associated with the standards applicable to Tier 8 engines, as 
contained in the proposed 1031.60(e)(2). The applicability of new type 
standards has traditionally been linked to the date of the first 
individual production engine of a given type, both for EPA regulations 
and ICAO regulations. This approach has been somewhat cumbersome in the 
past because a manufacturer would have to estimate what standards would 
be in effect when actual production of a new type began in order to 
determine to what standards a new type engine would be subject. Given 
that the engine type certification process can take up to three years, 
this approach has proven problematic during periods of transition from 
one standard to another. To address this concern, ICAO agreed at the 
CAEP/11 meeting in 2019 to transition from the date of manufacture of 
the first production engine to the date of application for a type 
certificate to determine standards applicability for new types. The EPA 
was actively involved in the deliberations that led to this agreement 
and supported the transition from date of first individual production 
model to date of application for type certification as the basis for 
standards applicability in the future. This approach is reflected in 
the applicability date provisions of the proposed PM standards, 
consistent with ICAO. The EPA is also proposing to adopt it for 
existing standards applicable to Tier 8 engines as well. This proposed 
change would have no impact on manufacturers as the existing standards 
applicable to Tier 8 engines have been in place since 2014, and there 
are no new gaseous or smoke number standards set to take effect for 
such engines. Thus, this proposed change is solely intended to improve 
consistency with ICAO and to structure the regulations such that the 
adoption of any future standards using this applicability date approach 
would be straightforward.
    The EPA is proposing to revise the definition of ``date of 
manufacture'' by replacing ``competent authority'' with ``recognized 
airworthiness authority'' in two places. The term ``competent'' has no 
specific meaning in the context of either the EPA's or the FAA's 
regulations. However, the FAA does recognize other airworthiness 
authorities for engines certificated outside the United States, as 
indicated through existing bilateral agreements with such authorities. 
Also, the EPA is proposing to update its definition of ``supersonic'' 
by replacing it with a new definition of ``supersonic airplane.'' The 
proposed new definition for ``supersonic airplane'' is based on a 
revised definition for such proposed by the FAA in a recent proposed 
action

[[Page 6353]]

regarding noise regulations for supersonic airplanes.\138\ This 
proposed new definition would provide greater assurance that the 
proposed standards applicable to engines used on supersonic airplanes 
would apply to the engines for which they are intended.
---------------------------------------------------------------------------

    \138\ 85 FR 20431, April 13, 2020.
---------------------------------------------------------------------------

    The EPA is proposing to update several definitions and align them 
with definitions included in the recent airplane GHG regulations.\139\ 
The definitions proposed to be updated are for ``Aircraft,'' ``Aircraft 
engine,'' ``Airplane,'' ``Exempt,'' and ``Subsonic.'' These definitions 
are proposed to be updated in the aircraft engine regulations simply 
for consistency with the airplane GHG regulations and with FAA 
regulations. The changes being proposed would not have any impact on 
the regulatory requirements related to the definitions.
---------------------------------------------------------------------------

    \139\ 86 FR 2136, January 11, 2021.
---------------------------------------------------------------------------

    The EPA is also proposing to address an unintentional applicability 
gap related to EPA's airplane GHG standards that could potentially 
exclude some airplanes from being subject to the standards. The 
intention of the international standards was to cover all jet airplanes 
with an MTOM greater than 5,700 kg. At ICAO it was agreed that 
airplanes with an MTOM less than 60,000 kg and with 19 seats or fewer 
could have extra time to comply with the standards (incorporated at 40 
CFR 1030.1(a)(2)). With that in mind, 40 CFR 1030.1(a)(1) was written 
to cover airplanes with 20 or more seats and an MTOM greater than 5,700 
kg. However, this means that airplanes with 19 seats or fewer and an 
MTOM greater than 60,000 kg are not covered by the current regulations 
but would be covered by the ICAO CO2 standard. While the EPA 
is not aware of any airplanes in this size range, the intent of the 
EPA's GHG rule was to cover all jet airplanes with MTOM greater than 
5,700 kg. The EPA is proposing to adopt new language at 40 CFR 
1030.1(a)(1)(iv)-(vi) to cover these airplanes, should they be 
produced. This proposed change would expand the current applicability 
of the GHG standards on the date this final rulemaking goes into 
effect. However, airplanes in this size category were considered as 
part of the GHG standard setting process and had been intended to be 
subject to the GHG standards.
    The EPA is proposing to correct the effective date of new type 
design GHG standards for turboprop airplanes (with a maximum takeoff 
mass greater than 8,618 kg), which is currently specified in 40 CFR 
1030.1(a)(3)(ii) as January 1, 2020. The EPA did not intend to 
retroactively apply these standards using the ICAO new type start date 
for these airplanes. Rather, this effective date should have been 
January 11, 2021, to be consistent with the effective date of new type 
standards for other categories of airplanes in this part (e.g., 40 CFR 
1030.1(a)(1)). Based on consultations with the FAA, this proposed 
change to part 1030 will not impact any airplanes.
    Finally, the EPA is proposing a minor word change to the existing 
applicability language in 40 CFR part 1030 in order to make it 
consistent with the current applicability language in the EPA's 
airplane engine regulations as well as FAA regulations. Specifically, 
the current language in 40 CFR 1030.1(c)(7) refers to airplanes powered 
with piston engines. The EPA is proposing to replace the word 
``piston'' with ``reciprocating'' in 40 CFR 1030.1(c)(7) to align it 
with the existing 40 CFR 87.3(a)(1), the proposed language in 40 CFR 
1031.1(b)(1), and existing FAA regulations in 14 CFR parts 1 and 33. 
This proposed change is for consistency among federal regulations and 
to avoid any confusion that may be caused by the use of two different 
terms. This proposed change would have no material impact on the 
meaning of the regulatory text.

VIII. Statutory Authority and Executive Order Reviews

    Additional information about these statutes and Executive orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is a significant regulatory action that was submitted 
to the Office of Management and Budget (OMB) for review. This action 
raises ``. . . novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
this Executive Order.'' This action promulgates new aircraft engine 
emissions regulations and as such, requires consultation and 
coordination with the Federal Aviation Administration (FAA). 
Accordingly, the EPA submitted this action to the OMB for review under 
E.O. 12866 and E.O. 13563. Any changes made in response to OMB 
recommendations have been documented in the docket. Section VI.E of 
this preamble summarizes the cost and benefits of this action.

B. Paperwork Reduction Act (PRA)

    This action does not impose any new information collection burden 
under the PRA. OMB has previously approved the information collection 
activities contained in the existing regulations and has assigned OMB 
control number 2060-0680. This proposed rule would codify that existing 
collection by including the current nvPM data collection in the 
proposed regulatory text, but it would not add any new reporting 
requirements.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. Among 
the potentially affected entities (manufacturers of aircraft engines) 
there is only one small entity, and that aircraft engine manufacturer 
does not make engines in the category subject to the proposed new 
provisions contained in this document (i.e., engines greater than 26.7 
kN rated output) and has not indicated any plans to begin such 
production. Therefore, this action will not impose any requirements on 
small entities. Supporting information can be found in the docket.\140\
---------------------------------------------------------------------------

    \140\ U.S. EPA, 2021: Determination of no SISNOSE for Proposed 
Aircraft Engine Emission Standards, Memorandum to Docket ID No. EPA-
HQ-OAR-2019-0660. This memorandum describes that the only small 
entity is Williams Int'l, which only make engines below 26.7 kN. 
Thus, they are not subject to the proposed standards.
---------------------------------------------------------------------------

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. The action imposes no enforceable duty on any state, 
local or tribal governments or the private sector.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

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

    This action does not have tribal implications as specified in 
Executive Order 13175. This action regulates the manufacturers of 
aircraft engines and will not have substantial direct effects on one or 
more Indian tribes, on the relationship between the Federal Government 
and Indian tribes, or on the distribution of power and

[[Page 6354]]

responsibilities between the Federal Government and Indian tribes. 
Thus, Executive Order 13175 does not apply to this action.

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

    This action is not subject to Executive Order 13045 because it is 
not economically significant as defined in Executive Order 12866. This 
action's health and risk assessments are contained in Section III.

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

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution or use of energy. These aircraft engine emissions 
regulations are not expected to result in any changes to aircraft fuel 
consumption.

I. National Technology Transfer and Advancement Act (NTTAA)

    This action involves technical standards for testing emissions for 
aircraft gas turbine engines. EPA is proposing to use test procedures 
contained in ICAO's International Standards and Recommended Practices 
Environmental Protection, Annex 16, Volume II along with the 
modifications contained in this rulemaking as described in Section IV. 
These procedures are currently used by all manufacturers of aircraft 
gas turbine engines to demonstrate compliance with ICAO emissions 
standards.
    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of test procedures contained in 
ICAO's International Standards and Recommended Practices Environmental 
Protection, Annex 16, Volume II, along with the modifications contained 
in this rulemaking. This includes the following standards and test 
methods:

 
------------------------------------------------------------------------
     Standard or test method          Regulation            Summary
------------------------------------------------------------------------
ICAO 2017, Aircraft Engine        40 CFR              Test method
 Emissions, Annex 16, Volume II,   1031.140(a), (b),   describes how to
 Fourth Edition, July 2017, as     (f), (g), and       measure PM,
 amended by Amendment 10,          (h), and 40 CFR     gaseous and smoke
 January 1, 2021.                  1031.205.           emissions from
                                                       aircraft engines.
------------------------------------------------------------------------

    The version of the ICAO Annex 16, Volume II that is proposed to be 
incorporated into the new 40 CFR part 1031 is the same version that is 
currently incorporated by reference in 40 CFR 87.1, 40 CFR 87.42(c), 
and 40 CFR 87.60(a) and (b).
    The referenced standards and test methods may be obtained through 
the International Civil Aviation Organization, Document Sales Unit, 999 
University Street, Montreal, Quebec, Canada H3C 5H7, (514) 954-8022, 
www.icao.int, or [email protected].

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

    The EPA believes that this action does not have disproportionately 
high and adverse human health or environmental effects on minority 
populations, low-income populations and/or indigenous peoples, as 
specified in Executive Order 12898 (59 FR 7629, February 16, 1994). 
This proposed action would not achieve emission reductions and would 
therefore result in no improvement in per-aircraft emissions for all 
communities living near airports. EPA describes in Section III.G the 
existing literature reporting on disparities in potential exposure to 
aircraft emissions for people of color and low-income populations. EPA, 
in an action separate from this proposed rulemaking, will be conducting 
an analysis of the communities residing near airports where jet 
aircraft operate in order to more fully understand disproportionately 
high and adverse human health or environmental effects on people of 
color, low-income populations and/or indigenous peoples, as specified 
in Executive Order 12898. The results of this analysis could help 
inform additional policies to reduce pollution in communities living in 
close proximity to airports.

List of Subjects

40 CFR Parts 87 and 1031

    Environmental protection, Air pollution control, Aircraft, 
Incorporation by reference.

40 CFR Part 1030

    Environmental protection, Air pollution control, Aircraft, 
Greenhouse gases.

Michael S. Regan,
Administrator.

    For the reasons set forth in the preamble, EPA proposes to amend 40 
CFR parts 87, 1030, and 1031 as follows:

PART 87--CONTROL OF AIR POLLUTION FROM AIRCRAFT AND AIRCRAFT 
ENGINES

0
1. Revise part 87 to read as follows:

PART 87--CONTROL OF AIR POLLUTION FROM AIRCRAFT AND AIRCRAFT 
ENGINES

87.1 Definitions.
87.2 Abbreviations.
87.3 General applicability and requirements.
87.10 Applicability--fuel venting.
87.11 Standard for fuel venting emissions.
87.20 Applicability--exhaust emissions.
87.21 Exhaust emission standards for Tier 4 and earlier engines.
87.23 Exhaust emission standards for Tier 6 and Tier 8 engines.
87.31 Exhaust emission standards for in-use engines.
87.48 Derivative engines for emissions certification purposes.
87.50 Exemptions and exceptions.
87.60 Testing engines.

    Authority:  42 U.S.C. 7401 et seq.

Sec.  87.1  Definitions.

    Definitions apply as described in 40 CFR 1031.205.

Sec.  87.2  Abbreviations.

    Abbreviations apply as described in 40 CFR 1031.200.

Sec.  87.3  General applicability and requirements.

    Provisions related to the general applicability and requirements of 
aircraft engine standards apply as described in 40 CFR 1031.1.

[[Page 6355]]

Sec.  87.10  Applicability--fuel venting.

    Fuel venting standards apply to certain aircraft engines as 
described in 40 CFR 1031.30(b).

Sec.  87.11  Standard for fuel venting emissions.

    Fuel venting standard apply as described in 40 CFR 1031.30(b).

Sec.  87.20  Applicability--exhaust emissions.

    Exhaust emission standards apply to certain aircraft engines as 
described in 40 CFR 1031.40 through 1031.90.

Sec.  87.21  Exhaust emission standards for Tier 4 and earlier engines.

    Exhaust emission standards apply to new aircraft engines as 
described in 40 CFR 1031.40 through 1031.90.

Sec.  87.23  Exhaust emission standards for Tier 6 and Tier 8 engines.

    Exhaust emission standards apply to new aircraft engines as 
follows:
    (a) New turboprop aircraft engine standards apply as described in 
40 CFR 1031.40.
    (b) New supersonic engine standards apply as described in 40 CFR 
1031.90.
    (c) New subsonic turbofan or turbojet aircraft engine standards 
apply as follows:
    (1) Standards for engines with rated output at or below 26.7 kN 
thrust apply as described in 40 CFR 1031.50.
    (2) Standards for engines with rated output above 26.7 kN thrust 
apply as described in 40 CFR 1031.60.
    (d) NOX standards apply based on the schedule for new 
type and in-production aircraft engines as described in 40 CFR 1031.60.

Sec.  87.31  Exhaust emission standards for in-use engines.

    Exhaust emission standards apply to in-use aircraft engines as 
described in 40 CFR 1031.60.

Sec.  87.48  Derivative engines for emissions certification purposes.

    Provisions related to derivative engines apply as described in 40 
CFR 1031.130.

Sec.  87.50  Exemptions and exceptions.

    Provisions related to exceptions apply as described in 40 CFR 
1031.11. Provisions related to exemptions apply as described in 40 CFR 
1031.10.

Sec.  87.60  Testing engines.

    Test procedures for measuring gaseous emissions and smoke number 
apply as described in 40 CFR 1031.140.

PART 1030--CONTROL OF GREENHOUSE GAS EMISSIONS FROM ENGINES 
INSTALLED ON AIRPLANES

0
2. The authority citation for part 1030 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
3. Amend Sec.  1030.1 by:
0
a. Revising paragraphs (a) introductory text and (a)(1)(iii);
0
b. Adding paragraphs (a)(1)(iv) through (vi);
0
c. Revising paragraphs (a)(3)(ii) and (c)(7).
    The revisions and additions read as follows:

Sec.  1030.1  Applicability.

    (a) Except as provided in paragraph (c) of this section, when an 
aircraft engine subject to 40 CFR part 1031 is installed on an airplane 
that is described in this section and subject to title 14 of the Code 
of Federal Regulations, the airplane may not exceed the Greenhouse Gas 
(GHG) standards of this part when original civil certification under 
title 14 is sought.
    (1) * * *
    (iii) An application for original type certification that is 
submitted on or after January 11, 2021; or
    (iv) A type-certificated maximum passenger seating capacity of 19 
seats or fewer, and
    (v) A MTOM greater than 60,000 kg, and
    (vi) An application for original type certification that is 
submitted on or after [DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL 
REGISTER].
* * * * *
    (3) * * *
    (ii) An application for original type certification that is 
submitted on or after January 11, 2021.
* * * * *
    (c) * * *
    (7) Airplanes powered by reciprocating engines.
0
4. Add part 1031 to read as follows:

PART 1031--CONTROL OF AIR POLLUTION FROM AIRCRAFT ENGINES

Subpart A--Scope and Applicability
1031.1 Applicability.
1031.5 Engines installed on domestic and foreign aircraft.
1031.10 State standards and controls.
1031.15 Exemptions.
1031.20 Exceptions.
Subpart B--Emission Standards and Measurement Procedures
1031.30 Overview of emission standards and general requirements.
1031.40 Turboprop engines.
1031.50 Subsonic turbojet and turbofan engines at or below 26.7 kN 
thrust.
1031.60 Subsonic turbojet and turbofan engines above 26.7 kN thrust.
1031.90 Supersonic Engines.
1031.130 Derivative engines for emissions certification purposes.
1031.140 Test procedures
Subpart C--Reporting and Recordkeeping
1031.150 Production reports.
1031.160 Recordkeeping.
1031.170 Confidential business information.
Subpart D--Reference Information
1031.200 Abbreviations.
1031.205 Definitions.
1031.210 Incorporation by reference.

    Authority:  -42 U.S.C. 7401-7671q.

Subpart A--Scope and Applicability

Sec.  1031.1  Applicability.

    This part applies to aircraft gas turbine engines on and after 
January 1, 2023. Emission standards apply as described in subpart B of 
this part.
    (a) Except as provided in paragraph (b) of this section, the 
regulations of this part apply to aircraft engines subject to 14 CFR 
part 33.
    (b) The requirements of this part do not apply to the following 
aircraft engines:
    (1) Reciprocating engines (including engines used in ultralight 
aircraft).
    (2) Turboshaft engines such as those used in helicopters.
    (3) Engines used only in aircraft that are not airplanes.
    (4) Engines not used for propulsion.

Sec.  1031.5  Engines installed on domestic and foreign aircraft.

    The Secretary of Transportation shall apply these regulations to 
aircraft of foreign registry in a manner consistent with obligations 
assumed by the United States in any treaty, convention or agreement 
between the United States and any foreign country or foreign countries.

Sec.  1031.10  State standards and controls.

    No State or political subdivision of a State may adopt or attempt 
to enforce any aircraft or aircraft engine standard with respect to 
emissions unless the standard is identical to a standard that applies 
to aircraft or aircraft engines under this part.

Sec.  1031.15  Exemptions.

    Individual engines may be exempted from current standards as 
described in this section. Exempted engines must conform to regulatory 
conditions specified for an exemption in this part and other applicable 
regulations. Exempted engines are deemed to be ``subject to'' the 
standards of this part

[[Page 6356]]

even though they are not required to comply with the otherwise 
applicable requirements. Engines exempted with respect to certain 
standards must comply with other standards as a condition of the 
exemption.
    (a) Engines installed in new aircraft. Each person seeking relief 
from compliance with this part at the time of certification must submit 
an application for exemption to the FAA in accordance with the 
regulations of 14 CFR parts 11 and 34. The FAA will consult with the 
EPA on each exemption application request before the FAA takes action. 
Exemption requests under this paragraph (a) are effective only with FAA 
approval and EPA's written concurrence.
    (b) Temporary exemptions based on flights for short durations at 
infrequent intervals. The emission standards of this part do not apply 
to engines that power aircraft operated in the United States for short 
durations at infrequent intervals. Exemption requests under this 
paragraph (b) are effective with FAA approval. Such operations are 
limited to:
    (1) Flights of an aircraft for the purpose of export to a foreign 
country, including any flights essential to demonstrate the integrity 
of an aircraft prior to its flight to a point outside the United 
States.
    (2) Flights to a base where repairs, alterations or maintenance are 
to be performed, or to a point of storage, and flights for the purpose 
of returning an aircraft to service.
    (3) Official visits by representatives of foreign governments.
    (4) Other flights the Secretary of Transportation determines to be 
for short durations at infrequent intervals. A request for such a 
determination shall be made before the flight takes place.

Sec.  1031.20  Exceptions.

    Individual engines may be excepted from current standards as 
described in this section. Excepted engines must conform to regulatory 
conditions specified for an exception in this part and other applicable 
regulations. Excepted engines are deemed to be ``subject to'' the 
standards of this part even though they are not required to comply with 
the otherwise applicable requirements. Engines excepted with respect to 
certain standards must comply with other standards from which they are 
not excepted.
    (a) Spare engines. Newly manufactured engines meeting the 
definition of ``spare engine'' are automatically excepted as follows:
    (1) This exception allows production of a newly manufactured engine 
for installation on an in-use aircraft. It does not allow for 
installation of a spare engine on a new aircraft.
    (2) Spare engines excepted under this paragraph (a) may be used 
only if they are certificated to emission standards equal to or lower 
than those of the engines they are replacing, for all regulated 
pollutants.
    (3) Engine manufacturers do not need to request approval to produce 
spare engines, but must include information about spare engine 
production in the annual report specified in Sec.  1031.150(d).
    (4) The permanent record for each engine excepted under this 
paragraph (a) must indicate that the engine was manufactured as an 
excepted spare engine.
    (5) Engines excepted under this paragraph (a) must be labeled with 
the following statement: ``EXCEPTED SPARE''.
    (b) [Reserved]

Subpart B--Emission Standards and Measurement Procedures

Sec.  1031.30  Overview of emission standards and general requirements.

    (a) Overview of standards. Standards apply to different types and 
sizes of aircraft engines as described in Sec. Sec.  1031.40 through 
1031.90. All new engines and some in-use engines are subject to smoke 
standards (either based on smoke number or nvPM mass concentration). 
Some new engines are also subject to standards for gaseous emissions 
(HC, CO, and NOX) and nvPM (mass and number).
    (1) Where there are multiple tiers of standards for a given 
pollutant, the named tier generally corresponds to the meeting of the 
International Civil Aviation Organization's (ICAO's) Committee on 
Aviation Environmental Protection (CAEP) at which the standards were 
agreed to internationally. Other standards are named Tier 0, Tier 1, or 
have names that describe the standards.
    (2) Where a standard is specified by a formula, determine the level 
of the standard as follows:
    (i) For smoke number standards, calculate and round the standard to 
the nearest 0.1 smoke number.
    (ii) For maximum nvPM mass concentration standards, calculate and 
round the standard to the nearest 1 [mu]g/m[caret]3.
    (iii) For LTO nvPM mass standards, calculate and round the standard 
to three significant figures.
    (iv) For LTO nvPM number standards calculate and round the standard 
to three significant figures.
    (v) For gaseous emission standards, calculate and round the 
standard to three significant figures, or to the nearest 0.1 g/kN for 
turbojet and turbofan standards at or above 100 g/kN.
    (3) Perform tests using the procedures specified in Sec.  1031.140 
to measure emissions for comparing to the standard. Engines comply with 
an applicable standard if test results show that the engine type 
certificate family's characteristic level does not exceed the numerical 
level of that standard.
    (4) Engines that are covered by the same type certificate and are 
determined to be derivative engines for emissions certification 
purposes under the requirements of Sec.  1031.130 are subject to the 
emission standards of the previously certified engine. Otherwise, the 
engine is subject to the emission standards that apply to a new engine 
type.
    (b) Fuel venting. (1) The fuel venting standard in paragraph (b)(2) 
of this section applies to new subsonic and supersonic aircraft engines 
subject to this part. This fuel venting standard also applies to the 
following in-use engines:
    (i) Turbojet and turbofan engines with rated output at or above 36 
kN thrust manufactured after February 1, 1974.
    (ii) Turbojet and turbofan engines with rated output below 36 kN 
thrust manufactured after January 1, 1975.
    (iii) Turboprop engines manufactured after January 1, 1975.
    (2) Engines may not discharge liquid fuel emissions into the 
atmosphere. This standard is directed at eliminating intentional 
discharge of liquid fuel drained from fuel nozzle manifolds after 
engines are shut down and does not apply to normal fuel seepage from 
shaft seals, joints, and fittings. Certification for the fuel venting 
standard will be based on an inspection of the method designed to 
eliminate these emissions.

Sec.  1031.40  Turboprop engines.

    The following standards apply to turboprop engines with rated 
output at or above 1,000 kW:
    (a) Smoke. (1) Engines of a type or model for which the date of 
manufacture of the individual engine is on or after January 1, 1984, 
may not have a characteristic level for smoke number exceeding the 
following value:

SN = 187[middot]rO-0.168

    (2) [Reserved]
    (b) [Reserved]

Sec.  1031.50  Subsonic turbojet and turbofan engines at or below 26.7 
kN thrust.

    The following standards apply to new turbofan or turbojet aircraft 
engines with rated output at or below 26.7 kN thrust that are installed 
in subsonic aircraft:
    (a) Smoke. (1) Engines of a type or model for which the date of

[[Page 6357]]

manufacture of the individual engine is on or after August 9, 1985 may 
not have a characteristic level for smoke number exceeding the lesser 
of 50 or the following value:

SN = 83.6[middot]rO-0.274

    (2) [Reserved]
    (b) [Reserved]

Sec.  1031.60  Subsonic turbojet and turbofan engines above 26.7 kN 
thrust.

    The following standards apply to new turbofan or turbojet aircraft 
engines with rated output above 26.7 kN thrust that are installed in 
subsonic aircraft:
    (a) Smoke. (1) Tier 0. Except as specified in (a)(2) of this 
section, engines of a type or model with rated output at or above 129 
kN, and for which the date of manufacture of the individual engine 
after January 1, 1976 and is before January 1, 1984 may not have a 
characteristic level for smoke number exceeding the following emission 
standard:

SN = 83.6[middot]rO-0.274

    (2) JT8D and JT3D engines. (i) Engines of the type JT8D for which 
the date of manufacture of the individual engine is on or after 
February 1, 1974 and before January 1, 1984 may not have a 
characteristic level for smoke number exceeding an emission standard of 
30.
    (ii) Engines of the type JT3D for which the date of manufacture of 
the individual engine is on or after January 1, 1978 and before January 
1, 1984 may not have a characteristic level for smoke number exceeding 
an emission standard of 25.
    (3) Tier 0 in-use. Except for engines of the type JT8D and JT3D, 
in-use engines with rated output at or above 129 kN thrust may not 
exceed the following smoke number standard:

SN = 83.6[middot]rO-0.274

    (4) JT8D in-use. In-use aircraft engines of the type JT8D may not 
exceed a smoke number standard of 30.
    (5) Tier 1. Engines of a type or model for which the date of 
manufacture of the individual engine is on or after January 1, 1984 and 
before January 1, 2023 may not have a characteristic level for smoke 
number exceeding an emission standard that is the lesser of 50 or the 
following:

SN = 83.6 [middot] rO-0.274

    (6) Tier 10. Engines of a type or model for which the date of 
manufacture of the individual engine is on or after January 1, 2023 may 
not have a characteristic level for the maximum nvPM mass concentration 
in [mu]g/m[supcaret]3 exceeding the following emission standard:

nvPMMC = 10(3+2.9[middot]rO-0.274)
    (b) LTO nvPM mass and number. An engine's characteristic level for 
nvPM mass and nvPM number may not exceed emission standards as follows:
    (1) Tier 11 new type. The following emission standards apply to 
engines of a type or model for which an application for original type 
certification is submitted on or after January 1, 2023 and for engines 
covered by an earlier type certificate if they do not qualify as 
derivative engines for emission purposes as described in Sec.  
1031.130:

    Table 1 to Sec.   1031.60(b)(1)--Tier 11 New Type nvPM Standards
------------------------------------------------------------------------
                                      nvPMmass in         nvPMnum in
     Rated output (rO) in kN         milligrams/kN       particles/kN
------------------------------------------------------------------------
26.7 < rO <= 150................  1251.1-             1.490[middot]10[su
                                   6.914[middot]rO.    pcaret]16-
                                                       8.080[middot]10[s
                                                       upcaret]13[middot
                                                       ]rO
rO > 150........................  214.0.............  2.780[middot]10[su
                                                       pcaret]15
------------------------------------------------------------------------

    (2) Tier 11 in-production. The following emission standards apply 
to engines of a type or model for which the date of manufacture of the 
individual engine is on or after January 1, 2023:

  Table 2 to Sec.   1031.60(b)(2)--Tier 11 In-Production nvPM Standards
------------------------------------------------------------------------
                                      nvPMmass in         nvPMnum in
     Rated output (rO) in kN         milligrams/kN       particles/kN
------------------------------------------------------------------------
26.7 < rO <= 200................  4646.9-             2.669[middot]10[su
                                   21.497[middot]rO.   pcaret]16-
                                                       1.126[middot]10[s
                                                       upcaret]14[middot
                                                       ]rO
rO > 200........................  347.5.............  4.170[middot]10[su
                                                       pcaret]15
------------------------------------------------------------------------

    (c) HC. Engines of a type or model for which the date of 
manufacture of the individual engine is on or after January 1, 1984 may 
not have a characteristic level for HC exceeding an emission standard 
of 19.6 g/kN.
    (d) CO. Engines of a type or model for which the date of 
manufacture of the individual engine is on or after July 7, 1997 may 
not have a characteristic level for CO exceeding an emission standard 
of 118 g/kN.
    (e) NOX. An engine's characteristic level for NOX may 
not exceed emission standards as follows:
    (1) Tier 0. The following NOX emission standards apply 
to engines of a type or model for which the date of manufacture of the 
first individual production model was on or before December 31, 1995 
and for which the date of manufacture of the individual engine was on 
or after December 31, 1999 and before December 31, 2003:

NOX + (40 + 2(rPR)) g/kN

    (2) Tier 2. The following NOX emission standards apply 
to engines of a type or model for which the date of manufacture of the 
first individual production model was after December 31, 1995 or for 
which the date of manufacture of the individual engine was on or after 
December 31, 1999 and before December 31, 2003:

NOX + (32 + 1.6(rPR)) g/kN

    (3) Tier 4 new type. The following NOX emission 
standards apply to engines of a type or model for which the date of 
manufacture of the first individual production model was after December 
31, 2003 and before July 18, 2012:

     Table 3 to Sec.   1031.60(e)(3)--Tier 4 New Type NOX Standards
------------------------------------------------------------------------
  If the rated pressure ratio     and the rated       the NOX emission
          (rPR) is--             output (kN) is--   standard (g/kN) is--
------------------------------------------------------------------------
(i) rPR <= 30.................  (A) 26.7 < rO <=   37.572 + 1.6(rPR)-
                                 89.                0.2087(rO)
                                (B) rO > 89......  19 + 1.6[middot]rPR

[[Page 6358]]

 
(ii) 30 < rPR < 62.5..........  (A) 26.7 < rO <=   42.71 + 1.4286(rPR)-
                                 89.                0.4013(rO) +
                                                    0.00642(rPR x rO)
                                (B) rO > 89......  7 + 2[middot]rPR
(iii) rPR >= 82.6.............  All..............  32 + 1.6[middot]rPR
------------------------------------------------------------------------

    (4) Tier 6 in-production. The following NOX emission 
standards apply to engines of a type or model for which the date of 
manufacture of the individual engine is on or after July 18, 2012:

   Table 4 to Sec.   1031.60(e)(4)--Tier 6 In-Production NOX Standards
------------------------------------------------------------------------
  If the rated pressure ratio     and the rated       the NOX emission
          (rPR) is--             output (kN) is--   standard (g/kN) is--
------------------------------------------------------------------------
(i) rPR <= 30.................  (A) 26.7 < rO <=   38.5486 +
                                 89.                1.6823[middot]rPR-
                                                    0.2453[middot]rO-
                                                    0.00308[middot]rPR[m
                                                    iddot]rO
                                (B) rO > 89......  16.72 +
                                                    1.4080[middot]rPR
(ii) 30 < rPR < 82.6..........  (A) 26.7 < rO <=   46.1600 +
                                 89.                1.4286[middot]rPR-
                                                    0.5303[middot]rO +
                                                    0.00642[middot]rPR[m
                                                    iddot]rO
                                (B) rO > 89......  -1.04 +
                                                    2.0[middot]rPR
(iii) rPR >= 82.6.............  All..............  32 + 1.6[middot]rPR
------------------------------------------------------------------------

    (5) Tier 8 new type. The following NOX standards apply 
to engines of a type or model for which the date of manufacture of the 
first individual production model was on or after January 1, 2014; or 
for which an application for original type certification is submitted 
on or after January 1, 2023; or for engines covered by an earlier type 
certificate if they do not qualify as derivative engines for emission 
purposes as described in Sec.  1031.130:

     Table 5 to Sec.   1031.60(e)(5)--Tier 8 New Type NOX Standards
------------------------------------------------------------------------
                                                       the NOX emission
   If the rated pressure ratio       and the rated      standard (g/kN)
           (rPR) is--              output (kN) is--          is--
------------------------------------------------------------------------
(i) rPR <= 30...................  (A) 26.7 < rO <=    40.052 +
                                   89.                 1.5681[middot]rPR-
                                                       0.3615[middot]rO-
                                                       0.0018[middot]rPR
                                                       [middot]rO
                                  (B) rO > 89.......  7.88 +
                                                       1.4080[middot]rPR
(ii) 30 < rPR < 104.7...........  (A) 26.7 < rO <=    41.9435 +
                                   89.                 1.505[middot]rPR-
                                                       0.5823[middot]rO
                                                       +
                                                       0.005562[middot]r
                                                       PR[middot]rO
                                  (B) rO > 89.......  -9.88 +
                                                       2.0[middot]rPR
(iii) rPR >= 104.7..............  All...............  32 +
                                                       1.6[middot]rPR
------------------------------------------------------------------------

Sec.  1031.90  Supersonic engines.

    The following standards apply to new engines installed in 
supersonic airplanes:
    (a) Smoke. (1) Engines of a type or model for which the date of 
manufacture was on or after January 1, 1984, may not have a 
characteristic level for smoke number exceeding an emission standard 
that is the lesser of 50 or the following:

    SN = 83.6[middot]rO-0.274

    (2) [Reserved]
    (b) [Reserved]
    (c) HC. Engines of a type or model for which the date of 
manufacture was on or after January 1, 1984, may not have a 
characteristic level for HC exceeding the following emission standard 
in g/kN rated output:

HC = 140[middot]0.92rPR

    (d) CO. Engines of a type or model for which the date of 
manufacture was on or after July 18, 2012, may not have a 
characteristic level for CO exceeding the following emission standard 
in g/kN rated output:

CO = 4550[middot]rPR-1.03

    (e) NOX. Engines of a type or model for which the date of 
manufacture was on or after July 18, 2012, may not have a 
characteristic level for NOX engines exceeding the following 
emission standard in g/kN rated output:

NOX = 36+2.42[middot]rPR

Sec.  1031.130  Derivative engines for emissions certification 
purposes.

    (a) Overview. FAA may approve a type certificate holder's request 
for an engine configuration to be considered a derivative engine for 
emission purposes under this part if the type certificate holder 
demonstrates the engine configuration is similar in design to a 
previously certificated (original) engine for purposes of compliance 
with exhaust emission standards and at least one of the following 
circumstances applies:
    (1) The FAA determines that a safety issue requires an engine 
modification.
    (2) All regulated emissions from the proposed derivative engine are 
lower than the corresponding emissions from the previously certificated 
engine.
    (3) The FAA determines that the proposed derivative engine's 
emissions are similar to the previously certificated engine's emissions 
as described in paragraph (c) of this section.
    (b) Determining emission rates. To determine new emission rates for 
a derivative engine for demonstrating compliance with emission 
standards under Sec.  1031.30(a)(4) and for showing emissions 
similarity in paragraph (c) of this section, testing may not be 
required in all situations. If the previously certificated engine model 
or any associated sub-models have a characteristic level before 
modification that is at or above 95% of any applicable standard for 
smoke number, HC, CO, or NOX or at or above 80% of any 
applicable nvPM standard, you must test the proposed derivative engine. 
Otherwise, you may use engineering analysis to determine the new 
emission rates, consistent with good engineering judgment. The 
engineering analysis must address all modifications from the

[[Page 6359]]

previously certificated engine, including those approved for previous 
derivative engines.
    (c) Emissions similarity. (1) A proposed derivative engine's 
emissions are similar to the previously certificated engine's emissions 
if the type certificate holder demonstrates that the engine meets the 
applicable emission standards and differ from the previously 
certificated engine's emissions only within the following ranges:
    (i) 3.0 g/kN for NOX.
    (ii) 1.0 g/kN for HC.
    (iii) 5.0 g/kN for CO.
    (iv) 2.0 SN for smoke number.
    (v) The following values apply for nvPMMC:
    (A) 200 [mu]g/m[supcaret]3 if the characteristic level 
of maximum nvPMMC is below 1,000 [mu]g/m[supcaret]3.
    (B) 20% of the characteristic level if the 
characteristic level for maximum nvPMMC is at or above 1,000 
[mu]g/m[supcaret]3.
    (vi) The following values apply for nvPMmass:
    (A) 80 mg/kN if the characteristic level for nvPMmass 
emissions is below 400 mg/kN.
    (B) 20% of the characteristic level if the 
characteristic level for nvPMmass emissions is greater than 
or equal to 400 mg/kN.
    (vii) The following values apply for nvPMnum:
    (A) 4 x 10[supcaret]14 particles/kN if the characteristic level for 
nvPMnum emissions is below 2 x 10[supcaret]15 particles/kN.
    (B) 20% of the characteristic level if the 
characteristic level for nvPMnum emissions is greater than 
or equal to 2 x 10[supcaret]15 particles/kN.
    (2) In unusual circumstances, the FAA may adjust the ranges 
specified in paragraph (c)(1) of this section to evaluate a proposed 
derivative engine, after consulting with the EPA.

Sec.  1031.140  Test procedures.

    (a) Overview. Measure emissions using the equipment, procedures, 
and test fuel specified in Appendices 1 through 8 of ICAO Annex 16 
(incorporated by reference, see Sec.  1031.210) as described in this 
section (referenced in this section as ``ICAO Appendix #''). For 
turboprop engines, use the procedures specified in ICAO Annex 16 for 
turbofan engines, consistent with good engineering judgment.
    (b) Test fuel specifications. Use a test fuel meeting the 
specifications described in ICAO Appendix 4. The test fuel must not 
have additives whose purpose is to suppress smoke, such as 
organometallic compounds.
    (c) Test conditions. Prepare test engines by including accessories 
that are available with production engines if they can reasonably be 
expected to influence emissions.
    (1) The test engine may not extract shaft power or bleed service 
air to provide power to auxiliary gearbox-mounted components required 
to drive aircraft systems.
    (2) Test engines must reach a steady operating temperature before 
the start of emission measurements.
    (d) Alternate procedures. In consultation with the EPA, the FAA may 
approve alternate procedures for measuring emissions. This might 
include testing and sampling methods, analytical techniques, and 
equipment specifications that differ from those specified in this part. 
An applicant for type certification may request this approval by 
sending a written request with supporting justification to the FAA and 
to the Designated EPA Program Officer. Such a request may be approved 
only in the following circumstances:
    (1) The engine cannot be tested using the specified procedures.
    (2) The alternate procedure is shown to be equivalent to or better 
(e.g., more accurate or precise) than the specified procedure.
    (e) LTO cycles. The following landing and take-off (LTO) cycles 
apply for emission testing and calculating weighted LTO values:

                                                     Table 1 to Sec.   1031.140(e)--LTO Test Cycles
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                     Subsonic                                       Supersonic
                                                         -----------------------------------------------------------------------------------------------
                                                                     Turboprop                 Turbojet and turbofan
                          Mode                           ----------------------------------------------------------------                  Time in mode
                                                                           Time in mode                    Time in mode    Percent of rO     (minutes)
                                                           Percent of rO     (minutes)     Percent of rO     (minutes)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Take-off................................................             100             0.5             100             0.7             100             1.2
Climb...................................................              90             2.5              85             2.2              65             2.0
Descent.................................................              NA              NA              NA              NA              15             1.2
Approach................................................              30             4.5              30             4.0              34             2.3
Taxi/ground idle........................................               7            26.0               7            26.0             5.8            26.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (f) Pollutant-specific test provisions. Use the following 
provisions to demonstrate whether engines meet the applicable 
standards:
    (1) Smoke number. Use the equipment and procedures specified in 
ICAO Appendix 2 and ICAO Appendix 6. Test the engine at sufficient 
thrust settings to determine and compute the maximum smoke number.
    (2) nvPM. Use the equipment and procedures specified in ICAO 
Appendix 7 and ICAO Appendix 6, as applicable:
    (i) Maximum nvPM mass concentration. Test the engine at sufficient 
thrust settings to determine and compute the maximum nvPM mass 
concentration produced by the engine at any thrust setting, according 
to the procedures of ICAO Appendix 7.
    (ii) LTO nvPM mass and number. Test the engine at sufficient thrust 
settings to determine the engine's nvPM mass and nvPM number at the 
rated output identified in table 1 to paragraph (e) of this section.
    (3) HC, CO, and NOX. Use the equipment and procedures specified in 
ICAO Appendix 3, ICAO Appendix 5, and ICAO Appendix 6, as applicable. 
Test the engine at sufficient thrust settings to determine the engine's 
HC, CO, and NOX emissions at the rated output identified in 
table 1 to paragraph (e) of this section.
    (4) CO2. Calculate CO2 emission values from 
fuel mass flow rate measurements in ICAO Appendix 3 and ICAO Appendix 5 
or, alternatively, according to the CO2 measurement criteria 
in ICAO Appendix 3 and ICAO Appendix 5.
    (g) Characteristic level. The compliance demonstration consists of 
establishing a mean value from testing some number of engines, then 
calculating a ``characteristic level'' by applying a set of statistical 
factors in ICAO Appendix 6 that take into account the number of engines 
tested. Round each characteristic level to the same number of decimal 
places as the corresponding standard. Engines

[[Page 6360]]

comply with an applicable standard if the testing results show that the 
engine type certificate family's characteristic level does not exceed 
the numerical level of that standard.
    (h) System loss corrected nvPM emission indices. Use the equipment 
and procedures specified in ICAO Appendix 8, as applicable, to 
determine system loss corrected nvPM emission indices.

Subpart C--Reporting and Recordkeeping

Sec.  1031.150  Production reports.

    Engine manufacturers must submit an annual production report for 
each calendar year in which they produce any engines subject to 
emission standards under this part.
    (a) The report is due by February 28 of the following calendar 
year. Include emission data in the report as described in paragraph (c) 
of this section. If you produce exempted or excepted engines, submit a 
single report with information on exempted/excepted and normally 
certificated engines.
    (b) Send the report to the Designated EPA Program Officer.
    (c) In the report, specify your corporate name and the year for 
which you are reporting. Include information as described in this 
section for each engine sub-model subject to emission standards under 
this part. List each engine sub-model manufactured or certificated 
during the calendar year, including the following information for each 
sub-model:
    (1) The type of engine (turbofan, turboprop, etc.) and complete 
sub-model name, including any applicable model name, sub-model 
identifier, and engine type certificate family identifier.
    (2) The certificate under which it was manufactured. Identify all 
the following:
    (i) The type certificate number. Specify if the sub-model also has 
a type certificate issued by a certificating authority other than FAA.
    (ii) Your corporate name as listed in the certificate.
    (iii) Emission standards to which the engine is certificated.
    (iv) Date of issue of type certificate (month and year).
    (v) Whether or not this is a derivative engine for emissions 
certification purposes. If so, identify the previously certificated 
engine model.
    (vi) The engine sub-model that received the original type 
certificate for an engine type certificate family.
    (3) Identify the combustor of the sub-model, where more than one 
type of combustor is available.
    (4) The calendar-year production volume of engines from the sub-
model that are covered by an FAA type certificate. Record zero for sub-
models with no engines manufactured during the calendar year, or state 
that the engine model is no longer in production and list the date of 
manufacture (month and year) of the last engine manufactured. Specify 
the number of these engines that are intended for use on new aircraft 
and the number that are intended for use as non-exempt engines on in-
use aircraft. For engines delivered without a final sub-model status 
and for which the manufacturer has not ascertained the engine's sub-
model when installed before submitting its production report, the 
manufacturer may do any of the following in its initial report, and 
amend it later:
    (i) List the sub-model that was shipped or the most probable sub-
model.
    (ii) List all potential sub-models.
    (iii) State ``Unknown Sub-Model.''
    (5) The number of engines tested and the number of test runs for 
the applicable type certificate.
    (6) Test data and related information required to certify the 
engine sub-model for all the standards that apply. Round reported 
values to the same number of decimal places as the standard. Include 
the following information, as applicable:
    (i) The engine's rated pressure ratio and rated output.
    (ii) The following values for each mode of the LTO test cycle:
    (A) Fuel mass flow rate.
    (B) Smoke number.
    (C) nvPM mass concentration.
    (D) mass of CO2
    (E) Emission Indices for HC, CO, NOX, and 
CO2.
    (F) The following values related to nvPM mass and nvPM number:
    (1) Emission Indices as measured.
    (2) System loss correction factor.
    (3) Emissions Indices after correcting for system losses.
    (iii) Weighted total values calculated from the tested LTO cycle 
modes for HC, CO, NOX, CO2, and nvPM mass and 
nvPM number. Include nvPM mass and nvPM number values with and without 
system loss correction.
    (iv) The characteristic level for HC, CO, NOX, smoke 
number, nvPM mass concentration, nvPM mass, and nvPM number.
    (v) The following maximum values:
    (A) Smoke number.
    (B) nvPM mass concentration.
    (C) nvPM mass Emission Index with and without system loss 
correction.
    (D) nvPM number Emission Index with and without system loss 
correction.
    (d) Identify the number of exempted or excepted engines with a date 
of manufacture during the calendar year, along with the engine model 
and sub-model names of each engine, the type of exemption or exception, 
and the use of each engine (for example, spare or new installation). 
For purposes of this paragraph (d), treat spare engine exceptions 
separate from other new engine exemptions.
    (e) Include the following signed statement and endorsement by an 
authorized representative of your company: ``We submit this report 
under 40 CFR 1031.150. All the information in this report is true and 
accurate to the best of my knowledge.''
    (f) Where information provided for the previous annual report 
remains valid and complete, you may report your production volumes and 
state that there are no changes, without resubmitting the other 
information specified in this section.

Sec.  1031.160  Recordkeeping.

    (a) You must keep a copy of any reports or other information you 
submit to us for at least three years.
    (b) Store these records in any format and on any media, as long as 
you can promptly send us organized, written records in English if we 
ask for them. You must keep these records readily available. We may 
review them at any time.

Sec.  1031.170  Confidential business information.

    The provisions of 40 CFR 1068.10 apply for information you consider 
confidential.

Subpart D--Reference Information

Sec.  1031.200  Abbreviations.

    The abbreviations used in this part have the following meanings:

[deg] Degree
% Percent
CO carbon monoxide
CO2 carbon dioxide
EI emission index
G Gram
HC hydrocarbon(s)
Kg Kilogram
kN Kilonewton
kW Kilowatt
LTO landing and takeoff
M Meter
Mg Milligram
[Mgr]g microgram
NOX oxides of nitrogen
Num number
nvPM nonvolatile particulate matter
nvPMmass nonvolatile particulate matter mass
nvPMnum nonvolatile particulate matter number
nvPMMC nonvolatile particulate matter mass concentration

[[Page 6361]]

rO rated output
rPR rated pressure ratio
SN smoke number

Sec.  1031.205  Definitions.

    The following definitions apply to this part. Any terms not defined 
in this section have the meaning given in the Clean Air Act (42 U.S.C. 
7401-7671q). The definitions follow:
    Aircraft has the meaning given in 14 CFR 1.1, a device that is used 
or intended to be used for flight in the air.
    Aircraft engine means a propulsion engine that is installed on or 
that is manufactured for installation on an airplane for which 
certification under 14 CFR is sought.
    Aircraft gas turbine engine means a turboprop, turbojet, or 
turbofan aircraft engine.
    Airplane has the meaning given in 14 CFR 1.1, an engine-driven 
fixed-wing aircraft heavier than air, that is supported in flight by 
the dynamic reaction of the air against its wings.
    Characteristic level has the meaning given in Appendix 6 of ICAO 
Annex 16 (incorporated by reference, see Sec.  1031.210). The 
characteristic level is a calculated emission level for each pollutant 
based on a statistical assessment of measured emissions from multiple 
tests.
    Date of manufacture means the date on which a manufacturer is 
issued documentation by FAA (or other recognized airworthiness 
authority for engines certificated outside the United States) attesting 
that the given engine conforms to all applicable requirements. This 
date may not be earlier than the date on which engine assembly is 
complete. Where the manufacturer does not obtain such documentation 
from FAA (or other recognized airworthiness authority for engines 
certificated outside the United States), date of manufacture means the 
date of final engine assembly.
    Derivative engine for emissions certification purposes means an 
engine that has the same or similar emissions characteristics as an 
engine covered by a U.S. type certificate issued under 14 CFR part 33. 
These characteristics are specified in Sec.  1031.130.
    Designated EPA Program Officer means the Director of the Assessment 
and Standards Division, 2000 Traverwood Drive, Ann Arbor, Michigan 
48105.
    Emission index means the quantity of pollutant emitted per unit of 
fuel mass used.
    Engine model means an engine manufacturer's designation for an 
engine grouping of engines and/or engine sub-models within a single 
engine type certificate family, where such engines have similar design, 
including being similar with respect to the core engine and combustor 
designs.
    Engine sub-model means a designation for a grouping of engines with 
essentially identical design, especially with respect to the core 
engine and combustor designs and other emission-related features. 
Engines from an engine sub-model must be contained within a single 
engine model. For purposes of this part, an original engine model 
configuration is considered a sub-model. For example, if a manufacturer 
initially produces an engine model designated ABC and later introduces 
a new sub-model ABC-1, the engine model consists of two sub-models: ABC 
and ABC-1.
    Engine type certificate family means a group of engines (comprising 
one or more engine models, including sub-models and derivative engines 
for emissions certification purposes of those engine models) determined 
by FAA to have a sufficiently common design to be grouped together 
under a type certificate.
    EPA means the U.S. Environmental Protection Agency.
    Except means to routinely allow engines to be manufactured and sold 
that do not meet (or do not fully meet) otherwise applicable standards. 
Note that this definition applies only with respect to Sec.  1031.11 
and that the term ``except'' has its plain meaning in other contexts.
    Exempt means to allow, through a formal case-by-case process, an 
engine to be certificated and sold that does not meet the applicable 
standards of this part.
    Exhaust emissions means substances emitted to the atmosphere from 
exhaust discharge nozzles, as measured by the test procedures specified 
in Sec.  1031.140.
    FAA means the U.S. Department of Transportation, Federal Aviation 
Administration.
    Good engineering judgment involves making decisions consistent with 
generally accepted scientific and engineering principles and all 
relevant information, subject to the provisions of 40 CFR 1068.5.
    ICAO Annex 16 means Volume II of Annex 16 to the Convention on 
International Civil Aviation (see Sec.  1031.210 for availability).
    New means relating to an aircraft or aircraft engine that has never 
been placed into service.
    Non-volatile particulate matter (nvPM) means emitted particles that 
exist at a gas turbine engine exhaust nozzle exit plane that do not 
volatilize when heated to a temperature of 350 [deg]C.
    Rated output (rO) means the maximum power or thrust available for 
takeoff at standard day conditions as approved for the engine by FAA, 
including reheat contribution where applicable, but excluding any 
contribution due to water injection. Rated output is expressed in 
kilowatts for turboprop engines and in kilonewtons for turbojet and 
turbofan engines to at least three significant figures.
    Rated pressure ratio (rPR) means the ratio between the combustor 
inlet pressure and the engine inlet pressure achieved by an engine 
operating at rated output, expressed to at least three significant 
figures.
    Round has the meaning given in 40 CFR 1065.1001.
    Smoke means the matter in exhaust emissions that obscures the 
transmission of light, as measured by the test procedures specified in 
Sec.  1031.140.
    Smoke number means a dimensionless value quantifying smoke 
emissions as calculated according to ICAO Annex 16.
    Spare engine means an engine installed (or intended to be 
installed) on an in-use aircraft to replace an existing engine. See 
Sec.  1031.11.
    Standard day conditions means the following ambient conditions: 
Temperature = 15 [deg]C, specific humidity = 0.00634 kg H2O/
kg dry air, and pressure = 101.325 kPa.
    Subsonic means relating to an aircraft that has not been 
certificated under 14 CFR to exceed Mach 1 in normal operation.
    Supersonic airplane means an airplane for which the maximum 
operating limit speed exceeds a Mach number of 1.
    System losses means the loss of particles during transport through 
a sampling or measurement system component or due to instrument 
performance. Sampling and measurement system loss is due to various 
deposition mechanisms, some of which are particle-size dependent. 
Determining an engine's actual emission rate depends on correcting for 
system losses in the nvPM measurement.
    Turbofan engine means a gas turbine engine designed to create its 
propulsion from exhaust gases and from air that bypasses the combustion 
process and is accelerated in a ducted space between the inner (core) 
engine case and the outer engine fan casing.
    Turbojet engine means a gas turbine engine that is designed to 
create its propulsion entirely from exhaust gases.
    Turboprop engine means a gas turbine engine that is designed to 
create most of

[[Page 6362]]

its propulsion from a propeller driven by a turbine, usually through a 
gearbox.
    Turboshaft engine means a gas turbine engine that is designed to 
drive a rotor transmission system or a gas turbine engine not used for 
propulsion.
    We (us, our) means the EPA Administrator and any authorized 
representatives.

Sec.  1031.210  Incorporation by reference.

    (a) Certain material is incorporated by reference into this part 
with the approval of the Director of the Federal Register under 5 
U.S.C. 552(a) and 1 CFR part 51. To enforce any edition other than that 
specified in this section, the Environmental Protection Agency must 
publish a document in the Federal Register and the material must be 
available to the public. All approved material is available for 
inspection at U.S. EPA, Air and Radiation Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Ave NW, Washington, DC 20004, 
www.epa.gov/dockets, (202) 202-1744, and is available from the sources 
listed in this section. It is also available for inspection at the 
National Archives and Records Administration (NARA). For information on 
the availability of this material at NARA, email [email protected] 
or go to www.archives.gov/federal-register/cfr/ibr-locations.html.
    (b) International Civil Aviation Organization, Document Sales Unit, 
999 University Street, Montreal, Quebec, Canada H3C 5H7, (514) 954-
8022, www.icao.int, or [email protected].
    (1) Annex 16 to the Convention on International Civil Aviation, 
Environmental Protection, as follows:
    (i) Volume II--Aircraft Engine Emissions, Fourth Edition, July 
2017, Including Amendment 10 of January 1, 2021 (as indicated in 
footnoted pages). IBR approved for Sec. Sec.  1031.140 and 1031.205.
    (ii) [Reserved]
    (2) [Reserved]

[FR Doc. 2022-01150 Filed 2-2-22; 8:45 am]
BILLING CODE 6560-50-P