Document ID: EPA-HQ-OAR-2019-0660-0211
Agency: epa
Document Type: Rule
Title: Control of Air Pollution from Aircraft Engines: Emission Standards and Test Procedures
Posted Date: 2022-11-23T05:00Z

[Federal Register Volume 87, Number 225 (Wednesday, November 23, 2022)]
[Rules and Regulations]
[Pages 72312-72357]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-25134]

[[Page 72311]]

Vol. 87

Wednesday,

No. 225

November 23, 2022

Part III

Environmental Protection Agency

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40 CFR Parts 9, 87, 1030, et al.

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

  Federal Register / Vol. 87, No. 225 / Wednesday, November 23, 2022 / 
Rules and Regulations  

[[Page 72312]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9, 87, 1030, and 1031

[EPA-HQ-OAR-2019-0660; FRL-7558-02-OAR]
RIN 2060-AU69

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

AGENCY: Environmental Protection Agency (EPA)

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is finalizing 
particulate matter (PM) emission standards and test procedures 
applicable to certain classes of engines used by civil subsonic jet 
airplanes (engines with rated output of greater than 26.7 kilonewtons 
(kN)) to replace the existing smoke standard for those engines. The EPA 
is adopting these standards under our authority in the Clean Air Act 
(CAA). These 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 will apply to both new type 
design aircraft engines and in-production aircraft engines. The EPA, as 
well as the U.S. Federal Aviation Administration (FAA), actively 
participated in the ICAO proceedings in which the ICAO requirements 
were developed. These standards 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 migrating, modernizing, and streamlining the 
existing regulations into a new part in the Code of Federal 
Regulations. As part of this update, the EPA is also aligning with ICAO 
by applying the smoke number standards to engines less than or equal to 
26.7 kilonewtons rated output used on supersonic airplanes.

DATES: This final rule is effective on December 23, 2022. The 
incorporation by reference of certain material listed in this rule is 
approved by the Director of the Federal Register as of December 23, 
2022.

ADDRESSES: The EPA has established a docket for this 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 EPA Docket Center, WJC West Building, Room 3334, 1301 
Constitution Ave. NW, Washington, DC. The Docket Center's hours of 
operations are 8:30 a.m.-4:30 p.m., Monday-Friday (except Federal 
Holidays). For further information on the EPA Docket Center services 
and the current status, see: 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
    C. EPA Future Work on Aircraft Engine PM Standards Beyond the 
Scope of This Final Rule
    D. Judicial Review, Administrative Reconsideration, and 
Severability
II. Introduction: Context for This Action
    A. The 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 the 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
    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 of the Rule
    A. PM Mass Standards for Aircraft Engines
    B. PM Number Standards for Aircraft Engines
    C. PM Mass Concentration Standard for Aircraft Engines
    D. Test and Measurement Procedures
    E. Annual Reporting Requirement
    F. Response to Key Comments
V. Aggregate PM Inventory Methodology and Impacts
    A. Aircraft Engine PM Emissions Modeling Methodologies
    B. 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 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) and 
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act

I. General Information

A. Does this action apply to me?

    This action will potentially 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 manufacture civil jet 
engines with a rated output at or below 26.7 kN for use on supersonic 
airplanes. These potentially 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).

[[Page 72313]]

    This table lists the types of entities that the 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, 1030, 
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 U.S. Code of Federal 
Regulations (CFR), common definitions for the words ``airplane,'' 
``aircraft,'' ``aircraft engine,'' and ``civil aircraft'' are found at 
14 CFR 1.1 and are used as appropriate throughout this new regulation 
under 40 CFR parts 87, 1030, and 1031.

B. Executive Summary

1. Summary of the Major Provisions of the Regulatory Action
    The EPA is regulating PM emissions from certain aircraft engines 
through the adoption of domestic PM regulations that match the ICAO PM 
standards, which will be implemented and enforced in the United States. 
The covered engines are subsonic turbofan and turbojet aircraft engines 
with rated output (maximum thrust available for takeoff) of greater 
than 26.7 kN. These aircraft engines are used by civil subsonic jet 
airplanes generally for the purpose of commercial passenger and freight 
aircraft, as well as larger business jets. The EPA is adopting 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 ([micro]g/m\3\). The applicable dates and coverage of 
these standards vary, as described in the following paragraphs, and 
more fully in sections IV.A, IV.B, and IV.C respectively.
    First, the EPA is finalizing PM engine emission standards, in the 
form of both PM mass (mg/kN) and PM number (#/kN), for both new type 
design and in-production covered engines. The standards for in-
production engines apply to those engines that are manufactured on or 
after January 1, 2023. The standards for new type designs apply to 
those engines whose initial type certification application is submitted 
on or after January 1, 2023. The in-production standards have different 
emission levels limits than the standards for new type designs. The 
different emission limits for new type designs and in-production 
engines depend on the rated output of the engines. Compliance with the 
PM mass and number standards will 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 adopting a PM engine emission standard in the 
form of maximum mass concentration ([micro]g/m\3\) for covered engines 
manufactured on or after January 1, 2023.\1\ Compliance with the PM 
mass concentration standard will be done using the same test data that 
is developed to demonstrate compliance with the LTO-based PM mass and 
number standards. The PM mass concentration standard applies to the 
highest concentration of PM measured across the engine operating thrust 
range, not 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 PM 
maximum mass concentration standards finalized in this action will 
have an implementation date of January 1, 2023 (instead of January 
1, 2020).
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    The 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 no longer applying the 
existing smoke number standard for new engines that will be subject to 
the 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 approach will 
essentially change the existing standard for covered engines from being 
based on a smoke measurement to a PM measurement.
    Third, the EPA is finalizing testing and measurement procedures for 
the PM emission standards and various updates to the existing gaseous 
exhaust emissions test procedures. These test procedure provisions will 
implement the recent additions and amendments to the ICAO's 
regulations, which are codified in ICAO Annex 16, Volume II. As we have 
historically done, we are incorporating these test procedure additions 
and amendments to the ICAO Annex 16, Volume II into our regulations by 
reference.
    The 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_2022_en.pdf (last accessed 
October 31, 2022). The ICAO Annex 16 Volume II is found on page 17 
of the ICAO Products & Services Catalog, English Edition of the 2022 
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 
migrating most of 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 are specified in this new 40 CFR part 
1031. Along with this migration, the EPA is restructuring the 
regulations to allow for better ease of use and allow for more 
efficient future updates. The EPA is also deleting some unnecessary 
definitions and regulatory provisions. Finally, the EPA is adopting 
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 Regulatory Action
    In developing these standards, the EPA took into consideration the 
Agency's legal authority and the explicit requirements under CAA 
section 231, including those relating to safety, noise, lead time and 
costs. The EPA further considered the importance of controlling PM 
emissions, international harmonization of aviation requirements, and 
the international nature of the aircraft industry and air travel. In 
addition, the EPA gave significant weight to the United States' 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 conclude that adopting standards 
for PM emissions from certain classes of

[[Page 72314]]

covered aircraft engines that are equivalent in scope, stringency, and 
effective date to the PM standards adopted by ICAO are appropriate at 
this time.
    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 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 emission 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 that the EPA is adopting were developed 
using this approach. Thus, the adoption of these aviation standards 
into U.S. law will 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 
meet the United States' treaty obligations under the Chicago 
Convention.
    These standards will also allow U.S. manufacturers of covered 
aircraft engines to remain competitive in the global marketplace (as 
described in 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) to market and operate their aircraft engines internationally. U.S. 
manufacturers could be at a significant disadvantage if the United 
States 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 adopted by other ICAO member states that certify 
aircraft engines.\3\ The action to adopt in the U.S. PM standards that 
match the ICAO standards will help ensure international consistency and 
acceptance of U.S.-manufactured engines worldwide.
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    \3\ Aside from the FAA in the United States, the only other 
civil aviation authorities that routinely certify airplane engines 
are Transport Canada and the European Union Aviation Safety Agency, 
both of which have already adopted the ICAO airplane engine 
particulate matter emission standards.
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3. Environmental Justice
    The 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. Section III.G discusses the potential environmental justice 
concerns associated with exposure to aircraft PM near airports.
    Studies have reported that many communities in close proximity to 
airports are disproportionately represented by people of color and low-
income populations (as described in Section III.G). Separate from this 
rulemaking, the EPA is conducting an analysis of communities residing 
near airports where jet aircraft operate 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 
standards in this final rule are technology-following 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 the standards to result in an improvement in air quality for 
those who live near airports where these aircraft operate.

C. EPA Future Work on Aircraft Engine PM Standards Beyond the Scope of 
This Final Rule

    While the EPA believes that adopting PM standards that match those 
developed and adopted by ICAO is the proper course of action in this 
final rule, the EPA views the standards adopted in this action as just 
one appropriate step in our efforts to control PM emissions from 
aircraft engines. Consistent with our statutory authority, which 
directs the EPA to issue, and permits the EPA to revise, standards 
``from time to time,'' CAA section 231(a)(2)(A) and (a)(3), after 
consultation with the FAA (CAA section 231(a)(2)(B)(i)), the EPA views 
our regulation of aircraft PM emissions as a long-term process, with 
the potential for successive standards of increasing stringency. Future 
stringencies may include technology-forcing standards, where 
appropriate, provided that such standards do not significantly increase 
noise and adversely affect safety in accordance with CAA section 
231(a)(2)(B)(ii). The EPA intends to continue to assess available 
emission control technologies and associated lead times, so that if the 
EPA were to pursue more stringent standards in the future, the EPA 
would provide the necessary time to permit the development and 
application of the requisite technology--giving appropriate 
consideration to the cost of compliance within such period.
    The EPA continues to believe that ICAO is the most appropriate 
venue in which to undertake such work. To that end, the U.S. delegation 
to ICAO/CAEP, with significant input from EPA, developed a position 
paper to the CAEP/12 meeting in February 2022.\4\ In this paper, the 
United States proposed several topics for CAEP to consider for future 
work on emissions items. Among the U.S. proposals was a call to update 
the PM standards beyond those already adopted by CAEP that would 
reflect best available technologies for future, to-be-developed, 
standards. The United States also proposed work to develop an updated 
metric to improve the effectiveness of future NOX emission 
standards, as well as an integrated standards-setting process to 
simultaneously update both PM and NOX standards for aircraft 
engines given the strong interdependency between engine NOX 
and PM levels.\5\ The EPA also advocated for improved modeling 
techniques that would better reflect the costs and emission reductions 
and better inform decision making around proposed CAEP emission 
standard levels.
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    \4\ U.S. EPA, Mueller, J. Memorandum to Docket ID No. EPA-HQ-
OAR-2019-0660, ``United States Position Papers to CAEP/12 Meeting,'' 
August 19, 2022.
    \5\ In this context, the metric is the form of the standard (in 
this case, mass of pollutant per unit of thrust), as well as the 
form of the regulatory limit line and any correlating parameters 
included. In the case of aircraft engine NOX, the 
regulatory limit line is a function of engine overall pressure 
ratio.

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[[Page 72315]]

    CAEP did not accept the U.S. request to work on updated aircraft 
engine NOX and PM standards during the current CAEP/13 cycle 
due to concerns that the resources needed for such work would 
negatively impact efforts to update the international airplane 
CO2 and noise standards. However, work on an improved 
NOX metric was approved and is underway this CAEP cycle, 
with an understanding that it is laying the groundwork for a potential 
update of the NOX and PM standards during the next CAEP 
cycle.\6\ Further, improving the cost and emission reduction modeling 
methodology has been agreed to as a work item for this CAEP cycle. The 
EPA is actively working within CAEP on both these efforts, and the EPA 
will continue to advocate for efforts in CAEP that will result in the 
development of future PM emission standards which reflect best 
available technologies.
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    \6\ ICAO, 2022: Committee on Aviation Environmental Protection 
(CAEP), Report of the Twelfth Meeting, Montreal, February 7-17, 
2022, Doc 10176, CAEP/12.
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D. Judicial Review, Administrative Reconsideration, and Severability

    This final action is ``nationally applicable'' within the meaning 
of CAA section 307(b)(1) because it is expressly listed in the section 
(i.e., ``any standard under section [231] of this title''). Under CAA 
section 307(b)(1), petitions for judicial review of this action must be 
filed in the U.S. Court of Appeals for the District of Columbia Circuit 
within 60 days from the date this final action is published in the 
Federal Register. Filing a petition for reconsideration by the 
Administrator of this final action does not affect the finality of the 
action for the purposes of judicial review, nor does it extend the time 
within which a petition for judicial review must be filed and shall not 
postpone the effectiveness of such rule or action. Under CAA section 
307(b)(2), the requirements established by this final rule may not be 
challenged separately in any civil or criminal proceedings brought by 
the EPA to enforce the requirements.
    CAA section 307(d)(7)(B) further provides that only an objection to 
a rule or procedure which was raised with reasonable specificity during 
the period for public comment (including any public hearing) may be 
raised during judicial review. This section also provides a mechanism 
for the EPA to reconsider the rule if the person raising an objection 
can demonstrate to the Administrator that it was impracticable to raise 
such objection within the period for public comment or if the grounds 
for such objection arose after the period for public comment (but 
within the time specified for judicial review) and if such objection is 
of central relevance to the outcome of the rule. Any person seeking to 
make such a demonstration should submit a Petition for Reconsideration 
to the Office of the Administrator, U.S. EPA, Room 3000, WJC South 
Building, 1200 Pennsylvania Ave. NW, Washington, DC 20460, with a copy 
to both the person listed in the FOR FURTHER INFORMATION CONTACT 
section, and the Associate General Counsel for the Air and Radiation 
Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200 
Pennsylvania Ave. NW, Washington, DC 20460. In addition, the EPA 
requests that an electronic copy of the Petition for Reconsideration 
also be sent to the person listed in the FOR FURTHER INFORMATION 
CONTACT section.
    The following portions of this rulemaking are mutually severable 
from each other: (1) the PM mass concentration standard in Section 
IV.C; (2) the PM mass and number standards in sections IV.A and IV.B; 
(3) the test and measurement procedures in Section IV.D; (4) the 
reporting requirements in Section IV.E; (5) those changes to 40 CFR 
parts 87 and 1031 described in Section VII that are not intended solely 
to implement the new PM standards; and (6) the changes to 40 CFR part 
1030 described in Section VII.C.\7\ The PM mass concentration standard 
and the PM mass and number standards serve different purposes, as 
described in more detail in Section IV. The reporting requirements 
(including those for PM) in Section IV.E predate this final rule as 
they were established by a prior Information Collection Request and are 
simply being added to the CFR in this action for the convenience of the 
entity required to provide a production report. Similarly, while the 
test and measurement procedures in Section IV.D will be used in 
determining compliance with the new PM standards, they are not 
dependent on the PM standards, and they are also required to be used to 
comply with the reporting requirements separate from the actual PM 
standards. The regulatory migration and other technical amendments in 
Section VII are not related to the implementation of the new PM 
standards. If any of the portions of this rule the EPA has identified 
as mutually severable from each other are vacated by a reviewing court, 
the EPA intends for the portions of this rule which are not vacated by 
a reviewing court to remain effective, and would only take action to 
remove the portions of the rule which are vacated from the CFR, leaving 
the other portions of the rule in effect.\8\ Finally, if a reviewing 
court were to vacate the PM mass concentration standard in Section 
IV.C, the EPA intends to reinstate the smoke number standard contained 
in 40 CFR 1031.60(a)(5) for engines with a rated output of greater than 
26.7 kN, such that the smoke number standard would go back into effect 
for those engines.
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    \7\ Certain portions may also be internally severable.
    \8\ The EPA considers those sections of regulatory text which 
are included only to implement the new PM standards to all be within 
40 CFR part 1031. Specifically, the regulatory text solely related 
to implementing the PM mass concentration standard is contained in 
Sec. Sec.  1031.30(a)(2)(ii), 1031.60(a)(6), and 1031.130(c)(1)(v), 
as well as the phrase ``before January 1, 2023'' in Sec.  
1031.60(a)(5), while the regulatory text solely related to 
implementing the PM mass and number standards is contained in 
Sec. Sec.  1031.30(a)(2)(iii) and (iv), 1031.60(b), and 
1031.130(c)(1)(vi) and (vii). All other regulatory changes are 
severable from the PM standards and are intended to remain in effect 
if any of the PM standards were to be set aside by a reviewing 
court.
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II. Introduction: Context for This Action

    The 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 final rule, which adopts three PM 
standards for aircraft engines (a PM mass standard, a PM number 
standard, and a PM mass concentration standard). This section includes 
a description of the EPA's statutory authority, the U.S. role in ICAO 
and developing international emission standards, and the relationship 
between the U.S. standards and the ICAO international standards.

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

    CAA section 231(a)(2)(A) directs the Administrator of the 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.\9\ 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.\10\ 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

[[Page 72316]]

appropriate.'' \11\ 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 within such period.\12\
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    \9\ 42 U.S.C. 7571(a)(2)(A).
    \10\ 42 U.S.C. 7571(a)(2)(B)(i)-(ii).
    \11\ 42 U.S.C. 7571(a)(3).
    \12\ 42 U.S.C. 7571(b).
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    Consistent with its longstanding approach \13\ and the District of 
Columbia (D.C.) Circuit precedent,\14\ 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 
statute and other relevant factors, such as applicable international 
standards. While the statutory language of CAA section 231 is not 
identical to other provisions of Title II of the CAA that direct the 
EPA to establish technology-based standards for various types of mobile 
sources, the EPA interprets its authority under CAA section 231 to be 
similar to those provisions that authorize us to identify a reasonable 
balance of specified emissions reduction, cost, safety, noise, and 
other factors.\15\ However, we are not compelled under CAA section 231 
to obtain the ``greatest degree of emission reduction achievable'' as 
per CAA sections 202(a)(3)(A) and 213(a)(3). The EPA does not interpret 
the Act as requiring the agency to give subordinate status to other 
factors such as cost, safety, and noise in determining what standards 
are reasonable for aircraft engines.\16\ Rather, the EPA has great 
flexibility under CAA section 231 in determining what standard is most 
reasonable for aircraft engines. Moreover, in light of the U.S. 
ratification of the Chicago Convention, EPA has historically given 
significant weight to uniformity with international requirements as a 
factor in setting aircraft engine standards. The fact that most 
airplanes already meet the standards does not in itself mean that the 
standards are inappropriate, provided the agency has a reasonable basis 
after considering all the relevant factors. By the same token, a 
technology-forcing standard would not be precluded by CAA section 231, 
in light of the forward-looking language of CAA section 231(b).\17\
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    \13\ See 70 FR 69664, 69676 (November 17, 2005); 86 FR 2136, 
2157 (January 11, 2021).
    \14\ The U.S. Court of Appeals for the D.C. Circuit has held 
that CAA section 231 confers an unusually ``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).
    \15\ See, e.g., Husqvarna AB v. EPA, 254 F.3d 195 (D.C. Cir. 
2001) (upholding the EPA's promulgation of technology-based 
standards for small non-road engines under CAA section 213(a)(3)).
    \16\ Cf. Sierra Club v. EPA, 325 F.3d 374, 378-380 (D.C. Cir. 
2003) (holding that even a Clean Air Act provision requiring the 
``greatest emission reduction achievable'' did not bind the Agency 
to weigh ``pure technological capability'' to the exclusion of other 
factors like cost, lead time, safety nor ``resolve how [the EPA] 
should weigh all these factors'').
    \17\ See 38 FR19088 (July 17, 1973); 41 FR 34722 (August 16, 
1976); see also NACAA, 489 F.3d at 1229-30.
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    Thus, as in past rulemakings, the 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.\18\ Once the EPA 
adopts standards, CAA section 232 then directs the Secretary of 
Transportation to prescribe regulations to ensure compliance with the 
EPA's standards.\19\ Finally, CAA section 233 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.\20\
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    \18\ See 70 FR 69664, 69676 (November 17, 2005); 86 FR 2136, 
2139-2140 (January 11, 2021).
    \19\ 42 U.S.C. 7572.
    \20\ 42 U.S.C. 7573.
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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.'' \21\ 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.22 23 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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    \21\ ICAO, 2006: Convention on International Civil Aviation, 
Ninth Edition, Document 7300/9. Available at: http://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed October 31, 
2022).
    \22\ Members of ICAO's Assembly are generally termed member 
States or contracting States.
    \23\ There are currently 193 contracting States (member States) 
according to ICAO's website. The list of ICAO member States is 
available in the docket for this rulemaking under document 
identification number EPA-HQ-OAR-2019-0660-0011.
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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 air navigation.'' \24\ 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.\25\
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    \24\ ICAO, 2006: Convention on International Civil Aviation, 
Article 37, Ninth Edition, Document 7300/9.
    \25\ Id.
---------------------------------------------------------------------------

    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

[[Page 72317]]

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.\26\ 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.\27\ 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.\28\
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    \26\ Id., Article 33.
    \27\ Id.
    \28\ Id., Article 38.
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    ICAO's Committee on Aviation Environmental Protection (CAEP), which 
consists of members and observers from States as well as 
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.'' \29\ 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).30 31
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    \29\ ICAO: CAEP Terms of Reference. A copy of the CAEP Terms of 
reference is available in the docket for this rulemaking under 
document identification number EPA-HQ-OAR-2019-0660-0006.
    \30\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017. The ICAO Annex 16 Volume 
II is found on page 17 of the ICAO Products & Services English 
Edition of the 2022 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.
    \31\ 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.\32\ These standards 
limited aircraft engine emissions of HC, CO, and 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.\33\ 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 
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 
2005.34 35 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, 2013.36 37 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.\38\
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    \32\ ICAO, 2017: Aircraft Engine Emissions: Foreword, 
International Standards and Recommended Practices, Environmental 
Protection, Annex 16, Volume II, Fourth Edition, July 2017. The ICAO 
Annex 16, Volume II, Fourth Edition, includes Amendment 10 of 
January 1, 2021.
    \33\ 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.
    \34\ CAEP/5 did not address new aircraft engine emission 
standards.
    \35\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017. The ICAO Annex 16, Volume 
II, Fourth Edition, includes Amendment 10 of January 1, 2021.
    \36\ CAEP/7 did not address new aircraft engine emission 
standards.
    \37\ 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.
    \38\ 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. The ICAO 
Annex 16, Volume II, Fourth Edition, includes Amendment 10 of 
January 1, 2021.
---------------------------------------------------------------------------

    At the CAEP/10 meeting in 2016, the Committee agreed to the first 
airplane

[[Page 72318]]

carbon dioxide (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.\39\
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    \39\ More specifically, the international PM maximum mass 
concentration 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 the 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.\40\ We have periodically revised these regulations.\41\ The 
EPA's actions to regulate certain pollutants emitted from aircraft 
engines come directly from the authority in CAA section 231, and we 
have aligned the U.S. emission requirements with those adopted by ICAO. 
As described in Section II.B, the ICAO/CAEP terms of reference includes 
technical feasibility.\42\ 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.\43\ 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 engine emission levels), which are 
technology-following.
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    \40\ Emission Standards and Test Procedures for Aircraft; Final 
Rule, 38 FR 19088 (July 17, 1973).
    \41\ The following are the most recent EPA rulemakings that 
revised these regulations. Control of Air Pollution from Aircraft 
and Aircraft Engines; Emission Standards and Test Procedures; Final 
Rule, 62 FR 25355 (May 8, 1997); Control of Air Pollution from 
Aircraft and Aircraft Engines; Emission Standards and Test 
Procedures; Final Rule, 70 FR 69664 (November 17, 2005); Control of 
Air Pollution from Aircraft and Aircraft Engines; Emission Standards 
and Test Procedures; Final Rule, 77 FR 36342 (June 18, 2012); 
Control of Air Pollution From Airplanes and Airplane Engines: GHG 
Emission Standards and Test Procedures; Final Rule, 86 FR 2136 
(January 11, 2021).
    \42\ ICAO: CAEP Terms of Reference. Available in the docket for 
this rulemaking under document identification number EPA-HQ-OAR-
2019-0660-0006.
    \43\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP/11. It is found on page 27 of the English 
Edition of the ICAO Products & Services 2022 Catalog and is 
copyright protected: Order No. 10126. 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 
with smoke number standards.\44\ 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 \45\ and again in 1984.\46\ Additionally, the 
EPA has amended the test procedures for measuring smoke emissions \47\ 
and modified the effective dates and compliance schedule for smoke 
emission standards periodically.\48\ Now, we are adopting 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 aircraft engine PM emission standards are 
a different way of regulating and/or measuring \49\ aircraft engine PM 
emissions in comparison to smoke number emission standards.
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    \44\ See 40 CFR 87.1 (July 1, 2021). ``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.''
    \45\ Control of Air Pollution From Aircraft and Aircraft 
Engines; Emission Standards and Test Procedures, Final Rule, 47 FR 
58462 (December 30, 1982).
    \46\ 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).
    \47\ 62 FR 25356 (harmonizing EPA procedures with recent 
amendments to ICAO test procedures); 70 FR 69664 (same); 77 FR 
36342.
    \48\ Amendment to Standards, Final Rule, 43 FR 12614 (March 24, 
1978) (setting back by two years the effective date for all gaseous 
emission standards for newly manufactured aircraft and aircraft gas 
turbine engines); 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); 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 
emission standards which would otherwise have been effective on 
January 1,1981, for aircraft gas turbine engines); 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); 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).
    \49\ Also, as described in Section IV.D, the final PM standards 
employ a different method for measuring aircraft engine PM emissions 
compared to the historical smoke number emission standards.
---------------------------------------------------------------------------

    Internationally, the EPA and the FAA have worked within the 
standard-setting process of ICAO (CAEP and its predecessor, CAEE) since 
the 1970s 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 the 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 U.S. Code. 
This rulemaking will 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 adopting PM standards equivalent to 
ICAO's three different forms of aircraft engine PM emission standards. 
Adoption of these standards will meet

[[Page 72319]]

the United States' obligations under the Chicago Convention and will 
also help ensure global acceptance of FAA airworthiness certification.
    In December 2018, the EPA issued an information collection request 
(ICR) that matches the CAEP/10 PM reporting requirements described in 
Section II.B.\50\ In addition to the PM standards, this rulemaking 
codifies the reporting requirements implemented by this 2018 EPA ICR 
into the EPA regulations, as described in Section IV.E. Also, in a 
similar time frame as this rulemaking, the EPA will be renewing this 
ICR (the ICR needs to be renewed triennially).
---------------------------------------------------------------------------

    \50\ Information Collection Request Submitted to OMB for Review 
and Approval; Comment Request; Aircraft Engines--Supplemental 
Information Related to Exhaust Emissions (Renewal), 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 ([micro]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), 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.\51\ Because of the difficulty in measuring 
volatile PM, which is formed in the engine's exhaust plume and is 
significantly influenced by ambient conditions, the EPA is adopting 
standards only for the emission of nvPM.
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    \51\ ICAO 2019 Environmental Report. This document is available 
in the docket for this rulemaking under document identification 
number EPA-HQ-OAR-2019-0660-0022. 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. . . . These particles are invisible to the human eye and 
are ultrafine.'' (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 
emissions 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.'' (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 U.S. EPA's Integrated Science Assessment for Particulate 
Matter (PM ISA), which was finalized in December 2019 (2019 PM ISA), 
with a more targeted evaluation of studies published since the 
literature cutoff date of the 2019 PM ISA in the Supplement to the 
Integrated Science Assessment for PM (Supplement).52 53 
Further discussion of PM-related health effects can also be found in 
the 2022 Policy Assessment for the review of the PM National Ambient 
Air Quality Standards (NAAQS).54 55
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    \52\ 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.
    \53\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-22/028, 
2022.
    \54\ U.S. EPA. Policy Assessment for the Reconsideration of the 
National Ambient Air Quality Standards for Particulate Matter (Final 
Report, 2022). U.S. Environmental Protection Agency, Washington, DC, 
EPA-452/R-22-004, 2022.
    \55\ 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.
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    The 2019 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.).\56\ The 2019 
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. Recent studies 
evaluated in the Supplement support the conclusion of the 2019 PM ISA 
with respect to disparities in both PM2.5 exposure and 
health risk by race and ethnicity and provide additional support for

[[Page 72320]]

disparities for lower socioeconomic status populations. 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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    \56\ 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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    The EPA has concluded that recent evidence in combination with 
evidence evaluated in the 2009 PM 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.\57\ 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. Because of remaining 
uncertainties and limitations in the evidence base, the EPA determined 
a ``suggestive of, but not sufficient to infer, a causal relationship'' 
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.
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    \57\ 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.\58\ The EPA is reconsidering a 2020 
decision to retain the PM NAAQS.\59\
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    \58\ U.S. EPA, Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-
0660, ``Health and environmental effects of non-GHG pollutants 
emitted by turbine engine aircraft--final rule version,'' August 11, 
2022.
    \59\ Id., p. 6.
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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 in Section III.B.
    PM2.5 emissions also adversely impact visibility.\60\ 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.\61\ In 1999, the EPA finalized the regional haze program to 
protect the visibility in Mandatory Class I Federal areas.\62\ There 
are 156 national parks, forests and wilderness areas categorized as 
Mandatory Class I Federal areas.\63\ 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. The 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). The secondary 
(welfare-based) PM NAAQS provide protection against visibility effects. 
In recent PM NAAQS reviews, EPA evaluated a target level of protection 
for visibility impairment that is expected to be met through attainment 
of the existing secondary PM standards.\64\
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    \60\ 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.
    \61\ See CAA section 169(a).
    \62\ Regional Haze Regulations; Final Rule, 64 FR 35714 (July 1, 
1999).
    \63\ National Ambient Air Quality Standards for Particulate 
Matter; Final Rule, 62 FR 38652 (July 18, 1997).
    \64\ Cook, op. cit., p. 6.
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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.\65\ 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.\66\
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    \65\ 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.
    \66\ 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.
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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 
deteriorating building materials such as stone, concrete and 
marble.\67\
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    \67\ 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.
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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.\68\ 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 activity at 
airports.\69\ 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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    \68\ 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.
    \69\ 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.
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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.\70\ The

[[Page 72321]]

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.'' \71\
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    \70\ 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.
    \71\ Id.
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    Furthermore, the report states 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).'' \72\ Finally, the report concludes that 
PM2.5 dominates overall health risks posed by airport 
emissions.\73\ 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.\74\
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    \72\ Id. at 40.
    \73\ Id. at 41.
    \74\ 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(4).
---------------------------------------------------------------------------

    Since the publication of the 2015 ACRP literature review, a number 
of studies conducted in the United States 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.\75\ In another study in the 
vicinity of Logan airport, Hudda et al. analyzed PNC impacts of 
aviation activities.\76\ 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.\77\ Similar findings have been 
published from European studies.78 79 80 81 82 83 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.\84\ The PM 
associated with aircraft landing activity was also smaller in size, 
with lower black carbon concentrations than near-roadway samples. As 
discussed in Section III.B, 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.85 86 For example, He et al. (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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    \75\ 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: 
pp. 1765-1772.
    \76\ 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: pp. 8514-8521.
    \77\ Stacey, B. 2019. Measurement of ultrafine particles at 
airports: A review. Atmos. Environ. 198: pp. 463-477.
    \78\ Masiol M., Harrison R.M. Quantification of air quality 
impacts of London Heathrow Airport (UK) from 2005 to 2012. Atmos 
Environ 2017; 116:308-19.
    \79\ 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: pp. 132-142.
    \80\ 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.
    \81\ Stacey, B., Harrison, R.M., Pope, F., 2020. Evaluation of 
ultrafine particle concentrations and size distributions at London 
Heathrow Airport. Atmos. Environ., 222: 117148.
    \82\ 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: pp. 3763-3775.
    \83\ 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: pp. 14161-14171.
    \84\ University of Washington. 2019. Mobile Observations of 
Ultrafine Particles: The Mov-UP study report.
    \85\ 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: 
pp. 48-59.
    \86\ 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, pp. 997-100.
---------------------------------------------------------------------------

    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.\87\ The systematic review identified seventy studies for 
evaluation. These studies consistently showed that particulate matter, 
in the form of 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 deoxyribonucleic acid (DNA) damage 
and childhood leukemia. As indicated in the proposal, 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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    \87\ 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.
---------------------------------------------------------------------------

    A systematic review of health effects associated with exposure to 
jet engine emissions in the vicinity of airports was also recently 
published.\88\ 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.\89\
---------------------------------------------------------------------------

    \88\ 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.
    \89\ 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.

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[[Page 72322]]

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 FAA Air 
Traffic Data System (ATADS). 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).\90\ Inventory estimates for turbine 
engine aircraft were adjusted to account for an improved methodology 
for estimating PM from nvPM measurements. This adjustment is described 
in detail in Section V.B. 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.\91\ At the county level, 
contributions to total mobile source PM2.5 emissions range 
from less than 1 to about 16 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 about 
0.5 to 3 percent. Details of this analysis are described in a 
memorandum to the docket.\92\
---------------------------------------------------------------------------

    \90\ 2017 National Emissions Inventory: Aviation Component, 
Eastern Research Group, Inc., June 25, 2020, 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. 
It should be noted that while identification of the 25 airports with 
the greatest commercial activity uses 2017 ATADS data, the 2017 NEI 
relies on 2014 ATADS data.
    \91\ 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 final PM standards is based 
on the ratio of total PM emissions from flights by engines with 
thrust rating greater than 26.7 kN compared to PM emissions from the 
whole fleet at each airport.
    \92\ U.S. EPA, Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-
0660, ``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--Final 
Rule,'' June 14, 2022.
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BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TR23NO22.165

Figure III-1

[[Page 72323]]

[GRAPHIC] [TIFF OMITTED] TR23NO22.166

BILLING CODE 6560-50-C
Figure III-2

F. Other Pollutants Emitted by Aircraft

    In addition to particulate matter, a number of other criteria 
pollutants are emitted by the aircraft subject to this final rule. 
These pollutants, which are not covered by the rule, include 
NOX, including nitrogen dioxide (NO2), VOC, 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.\93\
---------------------------------------------------------------------------

    \93\ 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.
---------------------------------------------------------------------------

    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.\94\ 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 in Section 
III.B.
---------------------------------------------------------------------------

    \94\ U.S. EPA, Air Toxics Screening Assessment.
---------------------------------------------------------------------------

G. Environmental Justice

    The 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.\95\ The 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.\96\
---------------------------------------------------------------------------

    \95\ ``Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis.'' Environmental Protection Agency (June 2016).
    \96\ 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.
---------------------------------------------------------------------------

    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

[[Page 72324]]

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.
    The 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, the EPA is committed to conducting environmental justice 
analysis for rulemakings based on a framework similar to what is 
outlined in the EPA's Technical Guidance, in addition to investigating 
ways to further weave environmental justice into the fabric of the 
rulemaking process.
    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.\97\ \98\ \99\ \100\ \101\
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    \97\ Rowangould, G.M. (2013) A census of the near-roadway 
population: public health and environmental justice considerations. 
Trans Res D 25: pp. 59-67.
    \98\ Marshall, J.D., Swor, K.R., Nguyen, N.P. (2014) 
Prioritizing environmental justice and equality: diesel emissions in 
Southern California. Environ Sci Technol 48: pp. 4063-4068.
    \99\ Marshall, J.D. (2000) Environmental inequality: air 
pollution exposures in California's South Coast Air Basin. Atmos 
Environ 21: pp. 5499-5503.
    \100\ 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.
    \101\ Mohai, P., Pellow, D., Roberts Timmons, J. (2009) 
Environmental justice. Annual Reviews 34: pp. 405-430.
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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.\102\ 
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.\103\
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    \102\ Henry, R.C., Mohan, S., Yazdani, S. (2019) Estimating 
potential air quality impact of airports on children attending the 
surrounding schools. Atmospheric Environment, 212: pp. 128-135.
    \103\ 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: pp. 234-247.
---------------------------------------------------------------------------

    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.\104\ 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.\105\
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    \104\ McNair, A. (2020) Investigation of environmental justice 
analysis in airport planning practice from 2000 to 2010. Transp. 
Research Part D 81:102286.
    \105\ Woodburn, A. (2017) Investigating neighborhood change in 
airport-adjacent communities in multiairport regions from 1970 to 
2010. Journal of the Transportation Research Board, 2626, pp. 1-8.
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    Although not being conducted as part of this rulemaking, the EPA is 
conducting a demographic analysis to explore whether populations living 
nearest the busiest runways show patterns of racial and socioeconomic 
disparity.\106\ 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.
---------------------------------------------------------------------------

    \106\ EPA anticipates that the results of the study will be 
released publicly in a separate document from the final rule.
---------------------------------------------------------------------------

    The final in-production standards for both PM mass and PM number 
are levels that all aircraft engines in production currently meet to 
align with ICAO's standards. Thus, the final standards are not expected 
to result in emission reductions, beyond the business-as-usual fleet 
turnover that would occur absent the final standards. Therefore, we do 
not anticipate an improvement in air quality for those who live near 
airports where these aircraft operate, beyond what may occur as a 
result of fleet turnover and from any reductions in emissions from 
other sectors contributing to air quality near airports.
    Response to comments on Section III of this action can be found in 
the Response to Comments document. In addition, all website addresses 
for references cited in this section are provided in a memorandum to 
the docket.\107\
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    \107\ U.S. EPA, Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-
0660, ``Web addresses for references cited in Section III of the 
preamble for Control of Air Pollution from Aircraft Engines: 
Emission Standards and Test Procedures; Final Rule,'' November 9, 
2022.
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IV. Details of the Final Rule

    In determining what final PM standards are appropriate under CAA 
section 231 and after consultation with FAA, the EPA considered the 
level of standards that could be met with the application of requisite 
technology within the necessary period of time that would allow the 
United States to meet its obligations under the Chicago Convention to 
at least match the ICAO standards, and gave appropriate consideration 
to the cost of compliance within this period. This determination also 
took into account the requirement that EPA's revised standards not 
significantly increase noise and adversely affect safety. The EPA 
considered the statutory requirements in CAA section 231 and other 
relevant factors as described in Section VI of both the proposed rule 
and this final rule, and we concluded that it was reasonable and 
appropriate to finalize the new PM standards that match the 
international standards in scope, stringency, and effective date. The 
EPA has consulted with FAA and believes sufficient lead time has been 
provided since the technology has already been developed and 
implemented by manufacturers to comply with the new PM standards. Also, 
as described in Section IV.F.1, the EPA is confident that the final 
standards will not significantly increase noise and adversely affect

[[Page 72325]]

safety. Further, as described in Section VI.D, the EPA does not project 
any costs associated with these standards because all in-production 
engines meet the in-production standards, nearly all in-production 
engines meet the new type design standard, and future new type designs 
are expected to meet the new type design standard. In addition to the 
statutory requirements of CAA section 231, the EPA, after consultation 
with FAA, also took into consideration the importance of controlling PM 
emissions, international harmonization of aviation requirements, and 
the international nature of the aircraft industry. The EPA gave 
significant weight to the United States' treaty obligations under the 
Chicago Convention in determining the need for and appropriate levels 
of PM standards. U.S. manufacturers could be at a significant 
disadvantage if the United States fails to adopt standards by the 
international implementation date. Also, given the short timeframe from 
this final action and the international implementation date, there 
would not be enough lead time for manufacturers to respond to more 
stringent standards that would require them to develop and implement 
new technologies.
    These considerations led the EPA to determine that adopting 
aircraft engine PM standards based on engine standards adopted by ICAO 
is appropriate at this time. When developing the PM standards, ICAO 
adopted 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 emission standards for other sectors. The second is 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.
    The EPA's final action will apply to subsonic turbofan and turbojet 
engines of a type or model with a rated output (maximum thrust 
available for takeoff) greater than 26.7 kN, hereinafter referred to as 
covered engines, and consists of three key parts: (1) PM mass and 
number emission standards for covered engines, (2) a change in test 
procedure and form of the existing standards for covered engines--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 final mass, number, and 
mass concentration standards for aircraft engines. Section IV.D 
describes the test procedures and measurement procedures associated 
with the PM standards. Section IV.E presents information related to the 
reporting requirements.
    As discussed in Section III.A, PM2.5 consists of both 
volatile and non-volatile PM (nvPM), although only non-volatile PM will 
be covered by the adopted standards. Only non-volatile 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. To directly measure non-volatile 
PM, ICAO agreed to adopt a measurement procedure, as described in 
Section IV.D, which is based on conditions that prevent the formation 
of volatile PM upstream of the measurement instruments. The intent of 
this approach is to improve the consistency and repeatability of the 
non-volatile PM measurement procedure.
    Due to the international nature of the aviation industry, there is 
an advantage to working within ICAO 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 emission 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 adopting were developed using 
this approach. Thus, the adoption of these aircraft engine standards 
into U.S. law will simultaneously prevent aircraft engine PM levels 
from increasing beyond their current levels, align U.S. domestic 
standards with the ICAO standards for international harmonization, meet 
the United States' treaty obligations under the Chicago Convention.
    These standards will 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 United States 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 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 United States does not 
adopt standards that are at least as stringent as the ICAO standards 
for PM emissions. This action to adopt, in the United States, PM 
standards that match the ICAO standards will 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. See 87 FR 6324, 6337 (February 3, 2022). As noted 
in the preceding paragraphs, the EPA, after consultation with FAA, 
considered the statutory requirements under CAA section 231, the 
importance of controlling PM emissions, international harmonization of 
aviation requirements, the international nature of the aircraft 
industry and air travel, and the United States' obligations under the 
Chicago Convention in evaluating which stringency of standards to 
propose. These considerations have historically led the EPA to adopt 
international standards developed through ICAO. The EPA concluded that 
proposing and now adopting standards equivalent to 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 standards. This is especially true for these final 
standards because they change our approach to regulating aircraft PM 
emissions from past smoke measurements to the measurement of nvPM mass 
concentration, nvPM mass, and nvPM number for the first time. It is

[[Page 72326]]

appropriate to gain experience from the implementation of these nvPM 
standards before considering whether to adopt more stringent nvPM mass 
and/or nvPM 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, through the FAA, 
State Department, and the EPA, played a significant role in the 
development of these standards through a multi-year process. The EPA 
believes that international cooperation on aircraft emissions brings 
substantial benefits overall to the United States. Given that the EPA 
and FAA invested significant effort and considerable resources 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 emission standards. For these 
reasons, the EPA placed significant weight on international regulatory 
uniformity and certainty and is finalizing standards that match the 
standards which the EPA worked to develop and adopt at ICAO.

A. PM Mass Standards for Aircraft Engines

1. Applicability of Standards
    These standards for PM mass, like the ICAO standards, will apply to 
covered engines whose date of manufacture is on or after January 1, 
2023.\108\ These standards will not apply to engines manufactured prior 
to this applicability date.
---------------------------------------------------------------------------

    \108\ 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. The 
ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of 
January 1, 2021.
    \109\ In most cases, the engine manufacturer applies to the FAA 
for the type certification; however, in some cases the applicant may 
be different than the manufacturer (e.g., designer).
---------------------------------------------------------------------------

    The level of the standard will vary based on when the initial type 
certification application is submitted.\109\ Covered engines for which 
the type certificate application was first submitted on or after 
January 1, 2023 will be subject to the new type level in Section 
IV.A.2. These engines are new engines that have not been previously 
certificated.
    Covered engines manufactured on or after January 1, 2023 will be 
subject to the in-production level, in Section IV.A.3.
2. New Type nvPM Mass Numerical Emission Limits for Aircraft Engines
    Covered engines 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 milligram (mg) of PM, as determined over 
the LTO cycle, divided by kN of rated output (rO).
[GRAPHIC] [TIFF OMITTED] TR23NO22.167

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

    Covered engines that are manufactured on or after January 1, 2023 
shall not exceed the level, as defined by Equation IV-2.
[GRAPHIC] [TIFF OMITTED] TR23NO22.168

4. Graphical Representation of nvPM Mass Numerical Emission Limits
    Figure IV-1 shows how the nvPM mass emission limits compare to 
known in-production engines. Data shown in this figure is from the ICAO 
Engine Emissions Databank (EEDB) \110\.
---------------------------------------------------------------------------

    \110\ 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.
---------------------------------------------------------------------------

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[[Page 72327]]

[GRAPHIC] [TIFF OMITTED] TR23NO22.169

Figure IV-1--nvPM mass standards compared to in-production engine LTO 
emission rates

B. PM Number Standards for Aircraft Engines

1. Applicability of Standards
    These standards for PM number, like the ICAO standards, will apply 
to covered engines whose date of manufacture is on or after January 1, 
2023.\111\ These standards will not apply to engines manufactured prior 
to this applicability date.
---------------------------------------------------------------------------

    \111\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-4pp. The ICAO Annex 
16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 
2021.
---------------------------------------------------------------------------

    The level of the standard will vary based on when the initial type 
certification application is submitted. Covered engines for which the 
type certificate application was first submitted on or after January 1, 
2023 will be subject to the new type level in Section IV.B.2. These are 
new engines that have not been previously certificated.
    Covered engines manufactured on or after January 1, 2023 will be 
subject to the in-production level, in Section IV.B.3.
2. New Type nvPM Number Numerical Emission Limits for Aircraft Engines

    Covered engines 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, as determined over 
the LTO cycle, divided by kN of rO.
[GRAPHIC] [TIFF OMITTED] TR23NO22.170

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

    Covered engines that are manufactured on or after January 1, 2023 
shall not exceed the level, as defined by Equation IV-4.

[[Page 72328]]

[GRAPHIC] [TIFF OMITTED] TR23NO22.171

4. Graphical Representation of nvPM Number Numerical Emission Limits

    Figure IV-2 shows how the nvPM number emission limits compare to 
known in-production engines. Data shown in this figure is from the ICAO 
Engine Emissions Databank (EEDB).\112\
---------------------------------------------------------------------------

    \112\ ICAO Aircraft Engine Emissions Databank, July 20, 2021, 
``edb-emissions-databank v28C (web).xlsx,'' European Union Aviation 
Safety Agency (EASA).
[GRAPHIC] [TIFF OMITTED] TR23NO22.172

---------------------------------------------------------------------------
BILLING CODE 6560-50-C

Figure IV-2--nvPM number standards compared to in-production engine LTO 
emission rates

C. PM Mass Concentration Standard for Aircraft Engines

    The previous 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.\113\ 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 p.m. 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. 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.
---------------------------------------------------------------------------

    \113\ ICAO, 2016: Tenth Meeting Committee on Aviation 
Environmental Protection Report, Doc 10069, CAEP/10.
---------------------------------------------------------------------------

    While the ICAO PM mass concentration standard was intended to have 
equivalent visibility control as the existing smoke number 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

[[Page 72329]]

during the process, and ultimately concurred with the results.\114\ 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.
---------------------------------------------------------------------------

    \114\ ICAO, 2019: Report of Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP/11. 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 adopting a PM mass concentration standard for all 
covered engines manufactured on or after January 1, 2023.\115\ This 
standard has the same form, test procedures, and stringency as the 
CAEP/10 p.m. mass concentration standard adopted by ICAO in 2017. Note, 
the applicability date of the mass concentration standard, finalized in 
this action, represents a delay from the January 1, 2020 date agreed to 
by ICAO \116\. The 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 previous 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 in Section IV.A and Section IV.B (and described in 
the introductory paragraphs of Section IV), this is based on the 
measurement of nvPM only, not total PM emissions.
---------------------------------------------------------------------------

    \115\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-3. The ICAO Annex 
16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 
2021.
    \116\ A second component of the CAEP/10 agreement was data 
collection by January 1, 2020, so the EPA implemented domestically 
by updating the Aircraft Engine Emission ICR (EPA ICR Number 
2427.04, OMB Control Number 2060-0680) on December 31, 2018 to 
include PM emission data.
---------------------------------------------------------------------------

    To determine compliance with the PM mass concentration standard, 
the maximum nvPM mass concentration [[mu]g/m\3\] will be obtained from 
measurements at sufficient thrust settings such that the emission 
maximum can be determined. The maximum value will 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] TR23NO22.178

    Engines certificated under the new PM mass concentration standard 
will not need to certify smoke number values and will not be subject to 
in-use smoke standards. It is important to note that other smoke number 
standards remain in effect for turbofan and turbojet aircraft engines 
at or below 26.7 kN rated output and for 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. In this final rule, the EPA did not reexamine or reopen the 
existing smoke number standards. Any comments we received on the 
existing smoke number standards are beyond the scope of this 
rulemaking.\117\
---------------------------------------------------------------------------

    \117\ The EPA proposed to extend the applicability of the smoke 
standards to engines of less than or equal to 26.7 kilonewtons (kN) 
rated output used in supersonic airplanes, and so the single comment 
received on the extended applicability is within the scope of this 
rulemaking and is responded to in the Response to Comments document.
---------------------------------------------------------------------------

2. Graphical Representation of nvPM Mass Concentration Numerical 
Emission Limit
    Figure IV-3 shows how the nvPM mass concentration emission limits 
compare to known in-production engines, which all were certified to the 
previous smoke standard. Data shown in this figure is from the ICAO 
Engine Emissions Databank (EEDB).\118\
---------------------------------------------------------------------------

    \118\ ICAO Aircraft Engine Emissions Databank, July 20, 2021, 
``edb-emissions-databank v28C (web).xlsx,'' European Union Aviation 
Safety Agency (EASA).

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[[Page 72330]]

[GRAPHIC] [TIFF OMITTED] TR23NO22.173

BILLING CODE 6560-50-C

Figure IV-3--nvPM Mass Concentration Standard

D. Test and Measurement Procedures

1. Aircraft Engine PM Emissions Metrics
    When developing the PM standards, ICAO adopted 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. The second is 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 is incorporating 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] TR23NO22.174

    The EPA is adopting the PM mass concentration standard based on the 
maximum mass concentration, in micrograms per meter cubed, produced by 
the engine at any thrust setting.
    Regulatory compliance with the emission standards is based on the 
product of Equation IV-6 or Equation IV-7 or mass concentration divided 
by the appropriate factor from Table IV-2, to obtain the characteristic 
level that is used to determine compliance with emission standards (see 
Section IV.D.4).
2. Test Procedure
    The EPA is incorporating by reference the PM test and measurement 
procedures in ICAO Annex 16, Volume II. These procedures were developed 
in conjunction with the Society of Automotive Engineers (SAE) E-31 
Aircraft Exhaust Emissions

[[Page 72331]]

Measurement Committee \119\ in close consultation between government 
and industry, and subsequently they were adopted by ICAO and 
incorporated into ICAO Annex 16, Volume II.
---------------------------------------------------------------------------

    \119\ The E-31 Committee develops and maintains standards for 
measurement of emissions from aircraft engines. (See https://www.sae.org/works/committeeHome.do?comtID=TEAE31, last accessed 
October 31, 2022).
---------------------------------------------------------------------------

    These procedures build off the existing ICAO Annex 16, Volume II 
aircraft engine measurement procedures for gaseous pollutants. As 
described in the Annex 16, at least three engine tests need to be 
conducted to determine the emissions rates. These tests can be 
conducted on a single engine or multiple engines.\120\ 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.
---------------------------------------------------------------------------

    \120\ For example, 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 
certain other EPA test procedures for mobile source PM2.5 
standards in two ways. First, as discussed in the introductory 
paragraphs of Section IV, the procedure is designed to measure only the 
non-volatile 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 from 
aircraft engines has proved challenging. Therefore, the development of 
a procedure for measuring nvPM was prioritized by ICAO and SAE E-31and 
the result is adopted in this final rule.
    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 procedures now incorporated by reference by the EPA 
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 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 in Section V.A.2.
3. Test Duty Cycles
    Mass and number PM emissions are measured over the LTO cycle shown 
in Table IV-1. This is the same duty cycle used 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. 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
                                  \121\
------------------------------------------------------------------------
                                                              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 previous 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 number, the number of tests needed 
can be reduced, and mass concentration data can be collected 
concurrently with other PM measurements. Like the previous smoke 
standard, the PM mass concentration standard is be based on the maximum 
value at any thrust setting. The engine(s) will 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 in Table IV-1.
---------------------------------------------------------------------------

    \121\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, III-4-2. The ICAO Annex 
16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 
2021.
---------------------------------------------------------------------------

    The EPA is incorporating by reference ICAO's Annex 16 to the 
Convention on International Civil Aviation, Environmental Protection, 
Volume II--Aircraft Engine Emissions, Fourth Edition, July 2017.
4. Characteristic Level
    EPA is incorporating by reference Appendix 6 to ICAO Annex 16, 
Volume II--International Standards and Recommended Practices for 
correcting engine measurements to characteristic value. Like existing 
gaseous standards, compliance with the PM standards adopted in this 
action is based on the characteristic level of the engine. The 
characteristic level is a statistical

[[Page 72332]]

method of accounting for engine-to-engine variation in the measurement 
based on the number of engines tested. A minimum of three engine 
emissions tests is needed to determine the engine type's emissions 
rates for compliance with emission 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 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.\122\ 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.
---------------------------------------------------------------------------

    \122\ ICAO, 2017: Aircraft Engine Emissions, International 
Standards and Recommended Practices, Environmental Protection, Annex 
16, Volume II, Fourth Edition, July 2017, App 6-2pp. The ICAO Annex 
16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 
2021.
[GRAPHIC] [TIFF OMITTED] TR23NO22.177

    For PM mass and PM number, the characteristic level is 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 is 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.
    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 139.005 mg/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 72333]]

5. Derivative Engines for Emissions Certification Purposes
    Aircraft engine types can remain in production for many years and 
be subject to numerous modifications during their production life. As 
part of the certification process for any change, the type certificate 
applicant will need to show if the change will have an 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 applicant and 
certification authorities, ICAO developed criteria to determine whether 
there has been an emissions change that requires new testing. Such 
criteria already exist at ICAO and in the EPA regulations for gaseous 
and smoke standards.
    ICAO recommends \123\ 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 applicant 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. The EPA is implementing these ICAO recommended 
practices in this final rule as the regulatory standard in the United 
States.
---------------------------------------------------------------------------

    \123\ ICAO, 2020, Environmental Technical Manual, Doc 9501, 
Volume II--Procedures for the Emissions Certification of aircraft 
Engines, Fourth Edition, Section 2, Part III, Chapter 2.
---------------------------------------------------------------------------

    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. The EPA is adopting 
these ICAO criteria in this final rule.\124\
---------------------------------------------------------------------------

    \124\ Id.
---------------------------------------------------------------------------

    For PM mass measurements described in Section IV.A, the following 
values 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 in Section IV.B, the 
following values apply:
     4x10\14\ particles/kN if the characteristic level for 
nvPMnum emissions is below 2x10\15\ particles/kN.
     20% of the characteristic level if the 
characteristic level for nvPMnum emissions is greater than 
or equal to 2x10\15\ particles/kN.
    For PM mass concentration measurements described in Section IV.C, 
the following values apply:
     200 [mu]g/m\3\ if the characteristic level of 
maximum nvPM mass concentration is below 1,000 [mu]g/m\3\.
     20% of the characteristic level if the 
characteristic level for maximum nvPM mass concentration is at or above 
1,000 [mu]g/m\3\.
    If a type certificate applicant can demonstrate that the engine's 
emissions are within these ranges, then new emissions rates will not 
need to be developed and the proposed derivative engine for emissions 
certification purposes will keep the existing emissions rates.
    If the engine is not determined to be a derivative engine for 
emissions certification purposes, the type certificate applicant will 
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.\125\ 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.126 127 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 rulemaking), and the EPA is including as part of 
that effort some additional data elements to the ICR (specifically, the 
emission indices for HC, CO, and NOX at each mode of the LTO 
cycle).128 129 The EPA is now formally 
incorporating all aspects of that ICR, as proposed to be renewed, into 
40 CFR 1031.150. It is important to note that the incorporation of the 
PM reporting requirements into the CFR will not create a new 
requirement for the manufacturers of aircraft engines. Rather, it will 
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.
---------------------------------------------------------------------------

    \125\ 77 FR 36342 (June 18, 2012).
    \126\ 83 FR 44621 (August 31, 2018).
    \127\ 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 June 8, 2022.
    \128\ Proposed Information Collection Request; Comment Request; 
Air Emissions Reporting Requirements (Renewal); EPA ICR No. 2170.08, 
OMB Control No. 2060-0580, 86 FR 24614 (May 7, 2021).
    \129\ Documentation and Public comments are available at: 
https://www.regulations.gov/docket/EPA-HQ-OAR-2016-0546, last 
accessed June 8, 2022.
---------------------------------------------------------------------------

    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 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 finalizing the proposal to 
migrate the existing 40 CFR part 87 regulatory text to a new 40 CFR 
part 1031. This effort includes clarifying portions of the regulatory 
text for ease of use. In the old 40 CFR 87.42(c)(6), the regulatory 
text did not specifically spell out some required data, but instead 
relied on incorporation by reference of ICAO Annex 16, Volume II's data 
reporting requirements and listed the data from this Annex that is not 
required by the EPA's reporting requirement. For future ease of use, 40 
CFR 1031.150 explicitly lists all the required items rather than 
continuing the incorporation by reference approach in the existing 
reporting regulations. Finally, the EPA is incorporating by reference 
Appendix 8 of Annex 16, Volume II, which outlines procedures used to 
estimate measurement system losses, which are a required element of the 
reporting provisions.

F. Response to Key Comments

    The EPA received numerous comments on the proposed rulemaking

[[Page 72334]]

which are summarized in the Response to Comments document along with 
the EPA's responses to those comments. Comments in their entirety are 
available in the docket for this rulemaking action. The following 
sections summarize the comments related to the stringency of the 
standards and the EPA's response to these comments. Some adverse 
comments are addressed more fully in the Response to Comments document.
1. Comments in Support of the Proposed Standards
    Comment summary: Some commenters stated that the proposed standards 
adhere to the statutory requirements of CAA section 231. They say that 
the proposed standards are well supported by an extensive 
administrative record. The commenters point out that the D.C. Circuit 
ruled in 2007 that CAA section 231 confers a broad degree of discretion 
on the EPA in setting aircraft engine emission standards.\130\
---------------------------------------------------------------------------

    \130\ National Association of Clean Air Agencies v. EPA, 489 
F.3d 1221, 1229-30 (D.C. Cir. 2007) (``When Congress enacted Sec.  
231 providing that the Administrator could, `from time to time,' act 
`in his judgment,' as `he deems appropriate,' it conferred broad 
discretion to the Administrator to weigh various factors in arriving 
at appropriate standards.'').
---------------------------------------------------------------------------

    Response: EPA is finalizing the standards as proposed. We agree 
that the proposed standards, as well as the final standards, satisfy 
our statutory obligations and are well-supported. The EPA acknowledges 
that the D.C. Circuit recognized the EPA's broad authority in CAA 
section 231 in National Association of Clean Air Agencies v. EPA, 489 
F.3d 1221, 1229-30 (D.C. Cir. 2007) (NACAA).
    Comment summary: Several commenters expressed their support of the 
EPA adopting PM standards that match the international PM standards 
because doing so is vital to the competitiveness of U.S. industry and 
regulatory certainty. They say it would protect U.S. jobs and 
strengthen the U.S. aviation industry by ensuring the global acceptance 
of U.S.-manufactured aircraft engines. They also say it will make sure 
U.S.-manufactured aircraft engines are available to aircraft 
manufacturers and U.S. airlines, while enabling U.S. airlines to obtain 
aircraft and aircraft engines at market-driven, competitive prices.
    Response: The EPA agrees this rule has the benefit of helping to 
ensure the acceptance of U.S.-manufactured aircraft engines by member 
States, aircraft (airframe) manufacturers, and airlines around the 
world. The EPA notes that under the terms of the Chicago Convention, 
ICAO member States must recognize as valid certificates of 
airworthiness issued by other ICAO member States, provided the 
requirements under which such certificates were issued are as least as 
stringent as the minimum ICAO standards.\131\
---------------------------------------------------------------------------

    \131\ ICAO, 2006: Convention on International Civil Aviation, 
Article 33, Ninth Edition, Document 7300/9.
---------------------------------------------------------------------------

    Comment summary: Some commenters urged the EPA to promptly issue 
the final rule with the standards matching the international standards. 
They say that this EPA rulemaking and the subsequent FAA certification 
rulemaking must be completed to start the certification process in the 
United States. Thus, they believe that prompt EPA action is necessary 
to provide sufficient time for FAA to promulgate their certification 
rulemaking and U.S. aircraft engine manufacturers to conduct the 
lengthy and expensive steps to demonstrate compliance with the 
standards, for all aircraft engines that will be in-production in 2023. 
They note that January 1, 2023, is the implementation date for the ICAO 
standards.
    Response: The EPA acknowledges that the international effective 
date for the ICAO mass concentration standards was January 1, 2020, and 
that the international effective date for the mass and number standards 
is January 1, 2023. The EPA also acknowledges that FAA will need to 
conduct a separate, subsequent certification rulemaking process to 
implement the EPA's PM standards finalized in this action.
    In this action, the EPA is aiming to minimize disruption by 
finalizing this action before the January 1, 2023, the international 
effective date of the PM mass and number standards.
    For comparison, the EPA notes the EPA finalized the domestic GHG 
standards for airplanes on January 11, 2021, after the international 
effective date for new type planes; \132\ however, disruption was 
avoided in practice because no manufacturers applied to FAA for a type 
certificate for a new type design airplane between January 1, 2020, and 
January 11, 2021.
---------------------------------------------------------------------------

    \132\ CAEP/10 airplane CO2 standards apply to new 
type design airplanes for which the application for a type 
certificate was or 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.
---------------------------------------------------------------------------

    Comment summary: Some commenters state that the proposed standards 
are identical to ICAO's aircraft engine PM standards and that adopting 
them is consistent with the 1944 Chicago Convention treaty obligations. 
They say that these standards continue the long collaborative tradition 
between the EPA and ICAO. The commenters say that the objective of the 
Chicago Convention is to foster global cooperation and encourage an 
atmosphere where international civil aviation could be developed in a 
safe and orderly manner, while being operated soundly and economically. 
The commenters say that, with both the FAA and the EPA playing key 
leadership roles, it was only after significant deliberation and 
technical and economic analyses that CAEP agreed to the ICAO PM 
standards. The commenters say that the EPA's adoption of standards that 
align with ICAO standards supports international harmonization and 
regulatory uniformity.
    Response: The EPA agrees adopting the PM standards in this action 
satisfies the United States' treaty obligations under the Chicago 
Convention. The EPA also agrees that the EPA and the FAA had key 
leadership roles in the ICAO PM standard-setting process, and the EPA 
recognizes the significant deliberations and economic analyses that 
occurred in CAEP. The EPA agrees that this action promotes 
international cooperation and harmonization.
    Comment summary: Some commenters say that the standards are 
consistent with the CAEP terms of reference which provide that 
standards be technologically feasible, economically reasonable, 
environmentally beneficial, and balanced against interdependencies 
(aircraft noise and competing emission reductions of other pollutants, 
such as NOX). The commenters say that the CAEP terms of 
reference align well with the considerations in CAA section 231, and 
ICAO's assessment of each of the criteria of the terms of reference is 
directly related to the decisions the EPA must make when issuing 
aircraft engine emission standards. The commenters assert that CAA 
section 231(b) requires that aircraft engine emission standards allow 
sufficient lead time for the development of the necessary technology, 
while giving consideration of the cost to comply within this time 
period.
    Response: The EPA agrees that the final standards are consistent 
with the CAEP terms of reference and that the standards also meet the 
requirements of CAA section 231. The EPA would not adopt ICAO standards 
domestically without exercising the Agency's own independent evaluation 
of appropriate domestic standards under CAA section 231, which is what 
the EPA has done in

[[Page 72335]]

this rulemaking. Any domestic aircraft engine standards adopted by the 
EPA must comport with the requirements in CAA section 231.
    Comment summary: Some commenters say that CAA section 
231(a)(2)(B)(ii) expressly prohibits changes in aircraft engine 
emission standards that ``would significantly increase noise and 
adversely affect safety.'' The commenters point out that, as the EPA 
describes in the proposed rulemaking, ICAO/CAEP evaluates 
``technological feasibility'' using the Technology Readiness Level 
(``TRL'') scale and deems technologies that have attained TRL8 (defined 
as the ``actual system completed and `flight qualified' through test 
and demonstration'') to be ``technologically feasible.'' Therefore, the 
commenters conclude, the use of TRL8 to evaluate ``technological 
feasibility'' makes sure aircraft engine emission standards reflect 
what technologies can safely deliver, instead of hypothetical 
``technology forcing'' standards that could pose a potential threat to 
air safety.\133\
---------------------------------------------------------------------------

    \133\ Any reference to technology-forcing standards in this 
rulemaking is not based on the level of the final PM standards, but 
it is intended to respond to comments.
---------------------------------------------------------------------------

    Response: The EPA agrees that TRL8 \134\ is an adequate and 
appropriate criteria for identifying proven technologies that are 
demonstrably safe and of an acceptable noise level for purposes of this 
rulemaking. The EPA relies on TRL8 to support the PM standards 
finalized in this rule because TRL8 was used to justify the PM 
standards by ICAO, as described in Section VI.B. ICAO treats TRL8 as a 
proxy for what is technologically feasible in the course of 
establishing new international standards. This conservative approach 
allows ICAO to ensure that all technology being considered is safe and 
of acceptable noise level without having to conduct additional 
evaluation of specific technologies. The EPA agrees this use of TRL8 is 
a valid means for ICAO to develop standards that will, by definition, 
be based on technologies that have been proven safe, of acceptable 
noise level, and technologically feasible. The EPA also agrees that 
ICAO's use of TRL8 means that technologies considered have been proven 
safe and of an acceptable noise level, and therefore, that the final PM 
standards do not adversely affect safety and do not significantly 
increase noise. In setting the international standards, ICAO 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. Thus, the technology was already 
demonstrated to be safe and of acceptable noise levels for these 
standards, and ICAO did not view that a new safety and noise analysis 
was necessary.
---------------------------------------------------------------------------

    \134\ As described in Section VI.B, 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.
---------------------------------------------------------------------------

    However, in the EPA's view, ICAO's use of TRL8 to define 
technological feasibility is not the only means to ensure a standard 
does not adversely affect safety and does not significantly increase 
noise. The EPA does not view TRL8 to represent the most stringent level 
of technology that could be required in an EPA aircraft standard 
setting rulemaking. Nor does the EPA agree with the premise that 
standards based on technology below TRL8 would necessarily be 
technology forcing or inherently have a negative effect on safety and 
noise. In establishing U.S. aircraft engine emission standards, the EPA 
is not constrained to ICAO's definition of technological feasibility in 
assessing appropriate aircraft engine standards under CAA section 
231(a). See NACAA, 489 F.3d at 1229-30. In fact, the EPA has adopted 
technology-forcing standards under CAA section 231 in the past and 
found them to be safe and not to significantly increase noise.\135\ In 
the future, if the EPA were to consider setting emission standards 
based on technology that was not yet at TRL8 or not expected to be at 
TRL8 by the implementation date of the standards,\136\ the Agency, just 
as it did in this action, in consultation with the FAA, would evaluate 
the safety and noise impact (also lead time and cost) of such standards 
before making a determination in this regard. CAA section 231(a)(2)(B) 
and (a)(3). Any assessment of safety and noise (also lead time and 
cost) in the context of hypothetical technology-forcing standards would 
have to occur in the context of the specific standards under 
consideration.
---------------------------------------------------------------------------

    \135\ See 38 FR 19088 (July 17, 1973); 41 FR 34722 (August 16, 
1976).
    \136\ As described in Section VI.B, for the ICAO PM standard 
setting, ICAO referred to technical feasibility as any technology 
demonstrated to be safe and airworthy proven to Technology Readiness 
Level 8 and available for application over a sufficient range of 
newly certificated aircraft. This means that the ICAO analysis that 
informed the international standard considered the emissions 
performance of aircraft engines assumed to be in-production on the 
ICAO implementation date for the PM mass and number standards, 
January 1, 2023.
---------------------------------------------------------------------------

2. Comments in Support of More Stringent Standards
    Comment summary: Several commenters were dissatisfied with the 
level of stringency of the PM standards. One commenter argued that CAA 
section 231 requires the EPA to adopt technology-forcing standards. 
Other comments argued CAA section 231 requires the EPA to set standards 
according to expectations of the development of technology over time. 
Some commenters say that, at a minimum, the EPA should establish 
standards that reduce emissions based on available engine technology. A 
number of commenters supported these arguments by pointing to the text 
of the statute, the underlying legislative intent, legislative history, 
and the purpose of the CAA.
    Response: The statutory-based arguments presented by commenters 
that the level of stringency of the PM standards are not authorized by 
CAA section 231 import requirements into the statute that do not exist.
    As described in Section II.A, CAA section 231(a)(2)(A) directs the 
Administrator of the 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 the Administrator's judgment 
causes or contributes to air pollution that may reasonably be 
anticipated to endanger public health or welfare. CAA section 231(a)(3) 
provides that after the EPA proposes standards, the Administrator shall 
issue such standards ``with such modifications as he deems 
appropriate.'' CAA section 231(b) requires that any emission standards 
``take effect after such period as the Administrator finds necessary . 
. . to permit the development and application of the requisite 
technology, giving appropriate consideration to the cost of compliance 
during such period.'' The D.C. Circuit has held that the delegation of 
authority in CAA section 231 ``is both explicit and extraordinarily 
broad'' and that the text confers ``broad discretion . . . to weigh 
various factors in arriving at appropriate standards.'' NACAA, 489 F.3d 
1221, 1229-30.
    The statutory language of CAA section 231 is not identical to other 
provisions in the CAA that direct the EPA to establish technology-based 
standards. CAA section 231(a) states that the EPA must ``issue proposed 
emission standards applicable to the emission of any air pollutant'' 
from aircraft engines

[[Page 72336]]

and to finalize ``such regulations'' with those modifications the EPA 
``deems appropriate.'' CAA section 231(a)(2)(A) and (a)(3). This 
language is in contrast to Congress' direction in other parts of the 
Act, where it required the EPA to set standards that achieve a 
particular degree of emission reduction or environmental or public 
health protection. For example, in setting technology-based emission 
standards for hazardous air pollutants under CAA section 112(d)(2) and 
(3), the EPA must ``require the maximum degree of reduction . . . that 
the Administrator . . . determines is achievable,'' taking into account 
cost and non-air quality health and environmental impacts. CAA section 
112(d)(2). Those standards also ``shall not be less stringent than'' 
explicitly prescribed levels. CAA section 112(d)(3). Health- and 
environmental quality-based NAAQS under CAA section 109 must be set at 
levels ``requisite to protect the public health'' and ``requisite to 
protect the public welfare from any known or anticipated adverse 
effects associated with the presence of [the] air pollutant in the 
ambient air.'' CAA section 109(b)(1) and (2). When regulating certain 
pollutants from motor vehicles and nonroad engine emissions under CAA 
sections 202(a)(3) and 213(a)(3) and (5), the EPA's standards must 
``reflect the greatest degree of emission reduction achievable . . . , 
giving appropriate consideration to cost, energy, and safety factors 
associated with the application of such technology.'' CAA sections 
202(a)(3) and 213(a)(3) and (5).
    CAA section 231 lacks comparable language requiring it to meet a 
particular threshold of protectiveness, emission reduction, or 
technological stringency, despite this clear evidence that Congress 
knew how to impose such obligations when it wished. See generally CAA 
section 231. ``Where Congress uses certain language in one part of a 
statute and different language in another, it is generally presumed 
that Congress acts intentionally.'' Nat'l Fed'n of Indep. Bus. v. 
Sebelius, 567 U.S. 519, 544 (2012); Sosa v. Alvarez-Machain, 542 U.S. 
692, 711 n.9 (2004) (citing a treatise on statutory construction and 
calling this principle the ``usual rule'' of judicial interpretation). 
In certain respects, the EPA's authority is broader than it is under 
other CAA provisions, in that the EPA is not required in setting 
aircraft emission standards to achieve a specified degree of emissions 
reduction.
    Some commenters also presented a textual comparison of the House 
and Senate bills to conclude that Congress intended for CAA section 231 
to be based on a consideration of pollution impacts and technological 
feasibility because the final CAA section 231(a)(1) required the EPA to 
conduct a study within 90 days after December 31, 1970 of air 
pollutants from aircraft to determine impact on air quality and 
technological feasibility of controlling such pollutants. S. Rep. No. 
91-1196, at 24, 1 Leg. Hist. at 424; H.R. Rep. No. 91-1783, at 55 
(Conf. Rep.). One commenter alleged this means ``the necessary premise 
[is] that such study should inform the standards themselves.'' \137\ 
However, the study requirement in CAA section 231(a)(1) does not 
establish a requirement for aircraft engine standards to be forward-
looking technology-based regulation. That provision required EPA to 
conduct a one-time ``study and investigation'' ``to determine'' the 
extent of aircraft emissions' impacts on air quality and the 
feasibility of controlling them ``[w]ithin 90 days after December 31, 
1970.'' The single study required in CAA section 231(a)(1) is not a 
continuing obligation that pertains to each exercise of the standard-
setting authority under CAA section 231(a)(2) and (3), which contain no 
discussion of technological feasibility and under which standards are 
set and may be revised ``from time to time.'' Cf. Sierra Club, 325 F.3d 
374, 377 (D.C. Cir. 2003) (holding that a provision requiring EPA to 
set standards ``based on'' such a study did not make the validity of 
the standards dependent on their connection to that study).
---------------------------------------------------------------------------

    \137\ Comments of California, Connecticut, Illinois, Maryland, 
Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Vermont, 
Washington, and Wisconsin at 13. See also Comment of Sierra Club at 
7-8.
---------------------------------------------------------------------------

    The commenters also quoted to a Senate report accompanying the CAA 
1970 amendment Senate bill to suggest CAA section 231 requires 
standards to be based on the degree of harm caused by aircraft 
pollution and the technology that can be developed in the future to 
reduce it. The statement cited by commenters from the Senate Report 
does not constrain the EPA where the plain text of the statute does 
not, and where Congress knew how, but declined, to make such 
constraints mandatory on the Agency. ``Congress' authoritative 
statement is the statutory text, not the legislative history.'' Chamber 
of Com. Of U.S. v. Whiting, 563 U.S. 582, 599 (2011) (quoting Exxon 
Mobil Corp. v. Allapattah Services, Inc., 545 U.S. 546, 568 (2005) 
(internal quotation marks omitted). Further, the NACAA Court rejected 
an argument that similar statements in the 1970 Senate Report 
established Congress' intent that the EPA prioritize forward-looking 
standards. NACAA, 489 F.3d at 1229-30; Sierra Club v. EPA, 325 F.3d 
374, 379-380 (D.C. Cir. 2003).
    The EPA's interpretation of CAA section 231 is not categorically at 
odds with the Clean Air Act's general protective purpose. The Act's 
general goal of reducing air pollution does not, in itself, prescribe 
regulatory factors for specific programs, nor does it restrict the 
EPA's discretion as to how best effectuate that goal in a specific 
action or in a regulatory program over time. Accordingly, while the 
EPA's discretion under CAA section 231 would allow it to select more 
stringent standards when appropriate, it does not mandate that the EPA 
elevate pollution reduction over all relevant factors in the 
consideration of any particular aircraft standard. See NACAA, 489 F.3d 
at 1229-30.
    The final PM standards fall squarely within the EPA's statutory 
authority under CAA section 231 to promulgate. As described in Section 
I.B.2 and the introductory text of Section IV, in proposing and 
adopting the final PM standards, the EPA considered the statutory 
requirements of CAA section 231. The EPA also took into account the 
need to control PM emissions, the importance of international 
harmonization, avoiding adverse impacts that could result from delaying 
adoption of PM standards at least as stringent as ICAO's PM standards, 
and gaining experience from the novel approach to implementing PM 
standards. Further, based on the EPA's independent view that technology 
at the TRL8 has been demonstrated to be safe and of an acceptable 
noise-level, the EPA is confident that the final standards will not 
significantly increase noise or adversely affect safety. The EPA 
reached the same conclusion as ICAO that a new noise and safety 
analysis was not necessary. For the same reasons, the EPA believes 
sufficient lead time has been provided since the technology has already 
been developed. Costs information for the standards is described in 
Section VI.D. Based on this assessment, the EPA concludes that it is 
reasonable to finalize PM standards that match the international 
standards in scope, stringency, and effective date.
    Additional legal issues raised by these comments are addressed in 
the Response to Comments document.
    Comment summary: Some commenters claim the EPA has an obligation to 
consider the feasibility, costs, and benefits of more stringent 
standards, including technology-forcing standards, or at least explain 
why it did

[[Page 72337]]

not do so. A few commenters proposed suggestions to alternative PM 
controls such as de-rated takeoff, accelerated implementation of 
Optimized Profile Descents, reduced power during taxiing, improved taxi 
time, and reduced usage of auxiliary power units (APUs).
    Response: The focused scope of the EPA's proposed PM standards was 
informed by the January 1, 2023, international effective date for the 
mass and number PM standards, as well as the other considerations 
identified elsewhere throughout this preamble. The EPA does not believe 
it would be feasible to repropose more stringent PM standards and also 
meet the international effective date of the new mass and number 
standards. Should the United States miss the January 1, 2023, deadline, 
U.S. airplane and engine manufacturers could be forced to seek PM 
emissions certification from an aviation certification of another 
country to market and operate their airplanes and engines 
internationally. The United States would also miss its obligations 
under the Chicago Convention.
    The EPA believes that the limited scope of the proposal is 
permissible under CAA section 231 and, based on the plain language of 
the statute, disagrees with the premise that the statute requires the 
Agency to propose multiple levels of stringency of standards. To the 
extent commenters identified specific alternative levels of stringency 
they would prefer, the comments did not provide sufficient information 
about safety, noise, lead time, and costs of those alternatives to 
support the EPA finalizing more stringent standards in this rulemaking. 
In light of the reasons the EPA has provided for adopting the PM 
standards as proposed, the EPA does not view these ``modifications'' 
requested by commenters to be ``appropriate'' to incorporate into the 
PM standards adopted in this rulemaking. See CAA section 231(a)(3). The 
EPA's current and intended future work related to addressing PM 
emissions from aircraft engines is described in Section I.C.
    A number of commenters also provided suggested ideas for 
alternative methods to regulating PM emissions (e.g., de-rated takeoff, 
reduced power during taxiing, and improved taxi time). The EPA has 
carefully reviewed the alternatives raised by the commenters, but has 
decided not to adopt them in this final rulemaking. The EPA does not 
believe it would be feasible to assess the legal, technical, and policy 
issues raised by suggested alternatives put forward by commenters; 
repropose standards; take public comment; and meet the international 
effective date of January 1, 2023. More specific comments related to 
suggested alternative PM controls are addressed in the Response to 
Comments document.
    Comment summary: According to some commenters, the EPA 
impermissibly factored international harmonization, adverse impacts on 
U.S. industry, or other non-statutory considerations into its rationale 
supporting the PM standards.
    Response: The EPA's past practice and the D.C. Circuit's holding in 
NACAA that the EPA's historical approach of taking international 
harmonization into account in setting domestic standards as not 
``manifestly contrary to the statute'', NACAA, 489 F.3d at 1230, affirm 
that the EPA's broad discretion includes the ability to weigh 
considerations such as international harmonization and the competitive 
effects of the EPA's standards on international aviation. Nothing in 
CAA section 231 precludes such considerations. Aircraft and their 
engines are manufactured and sold around the world, and routinely 
operate in international airspace. Furthermore, CAA section 231 does 
not list or dictate the EPA's consideration of particular factors and 
enables the EPA to identify and apply relevant considerations in 
determining what standards are ``appropriate''. CAA section 231(a)(3). 
The D.C. Circuit rejected an argument similar to the commenters' in 
NACAA: ``Finding nothing in the text or structure of the statute to 
indicate that the Congress intended to preclude the EPA from 
considering `[factors other than air quality],' we refused to infer 
from congressional silence an intention to preclude the agency from 
considering factors other than those listed in a statute.'' 489 F.3d at 
1230 (quoting George E. Warren Corp. v. EPA, 159 F.3d 61, 623-24 (D.C. 
Cir. 1998)). Moreover, the Chicago Convention, ratified by the United 
States, has the force of Federal law, and therefore, the EPA acts 
appropriately in implementing our Clean Air Act authorities in a manner 
that is harmonious and consistent with the Chicago Convention and the 
United States' international obligations under the treaty.
    Having invested significant effort and resources, working with the 
FAA and the Department of State, to gain international consensus within 
ICAO to adopt the international PM standards for aircraft engines, the 
EPA believes that meeting the United States' obligations under the 
Chicago Convention by aligning domestic standards with the ICAO 
standards, rather than adopting more stringent standards, will have 
substantial benefits for future international cooperation on aircraft 
engine emission standards, and such cooperation is the key for 
achieving worldwide emission reductions. Deviating from the 
international PM standards could undermine future efforts by the United 
States to seek international consensus on aircraft emission standards 
in general, including more stringent future standards for PM. Reaching 
this conclusion is not tantamount to a determination that it would 
never be appropriate for the EPA to adopt more stringent PM standards 
than ICAO's standards. However, at this time, the EPA finds it 
appropriate to finalize the standards as proposed.
    In addition, the ICAO applicability date of the mass and number 
standards of January 1, 2023, is fast approaching. The U.S. aircraft 
engine manufacturers, aircraft manufacturers, and airlines are urging 
the EPA to promptly promulgate this final rulemaking to adopt ICAO's 
standards, which were adopted back in 2017 and 2020, so they can build 
(and sell) or have access to U.S. engines to remain competitive in the 
global marketplace. Furthermore, the EPA understands that U.S. aircraft 
engine manufacturers need time to certify their products, after the 
subsequent FAA rulemaking to enforce the standards, to ensure the 
aircraft engines comply with standards. Also, the EPA did not conduct 
the analyses needed to support more stringent standards in the proposed 
rulemaking, or otherwise develop a sufficient record for more stringent 
standards, that would be necessary to support finalizing such standards 
in this final rule. We do not believe we could finalize more stringent 
standards without conducting significant additional analyses and 
undertaking a new round of notice and comment, which would certainly 
cause a significant delay in meeting the United States' obligations 
under the Chicago Convention. We have decided that the most appropriate 
course, under CAA section 231, is to adopt aircraft engine PM standards 
that are harmonized with the standards adopted by ICAO in 2017 and 
2020.
    In determining what final PM standards are appropriate under CAA 
section 231 and after consultation with FAA, the EPA considered the 
level of standards that could be met with the application of requisite 
technology within the necessary period of time that would allow the 
United States to meet its obligations under the Chicago Convention to 
at least match the ICAO standards, and gave appropriate consideration 
to the cost of compliance within this period. This determination also 
took into account the requirement

[[Page 72338]]

that EPA's revised standards not significantly increase noise and 
adversely affect safety.
    Comment summary: Some commenters argued that the EPA's position 
that it would be appropriate to gain experience from implementation of 
the novel approach to implementing PM standards before considering 
whether to adopt more stringent regulations is arbitrary and 
capricious.
    Response: As described the introductory paragraphs of Section IV, 
these final standards change the approach to regulating aircraft engine 
PM emissions from past smoke measurements to the measurement of mass 
and number for the first time for U.S. manufacturers, and international 
regulatory uniformity and certainty are key elements for these 
manufacturers as they become familiar with adhering to these standards 
and test procedures. Further, some manufacturers are still adapting to 
how best control aircraft engine PM since they designed recent in-
production engines to optimize NOX control, as explained in 
the succeeding paragraphs.\138\ We think that considering the novelty 
of these approaches and the industry's response to them falls well 
within our discretion. Moreover, they also pertain to the statutory 
directive to consider the lead time necessary for the development and 
application of the requisite technology. See CAA section 231(b).
---------------------------------------------------------------------------

    \138\ ICAO, 2019: Independent Expert Integrated Technology Goals 
Assessment and Review for Engines and Aircraft, Document 10127. It 
is found on page 34 of the English Edition of the ICAO Products & 
Services 2022 Catalog and is copyright protected; Order No. 10127.
---------------------------------------------------------------------------

    Comment summary: Some commenters say that proposed standards are 
far less stringent than PM emission levels that existing aircraft 
engine technologies already achieve. Some commenters assert that more 
stringent PM standards compared to the proposed standards are feasible 
for in-production and new type design aircraft engines. Some commenters 
argue that the proposed PM standards are not anti-backsliding. These 
comments say that all in-production engines already meet the proposed 
standards for in-production engines and most meet the proposed 
standards for new type design engines by a considerable margin; 
therefore, no backsliding could reasonably happen absent these 
standards.
    Response: While it may be true that more stringent PM standards 
compared to the final standards are feasible for some in-production and 
new type design aircraft engines, for the reasons explained in the 
proposal and again in this final rule the EPA does not consider more 
stringent standards than those adopted in this action, applicable to 
all in-production and new type design engines, to be appropriate at 
this time. Additionally, the EPA did not propose more stringent 
standards, and the existing record that has been developed does not 
support finalizing more stringent standards absent significant 
additional analyses.
    The EPA disagrees that the standards are not anti-backsliding. 
Although the PM mass concentration standard is replacing the smoke 
standard for some engines, the PM mass and number standards are the 
first of their kind. In that regard, PM mass and number are currently 
unregulated from aircraft engines and the standards finalized in this 
action represent a new regulatory backstop of those two forms of 
previously uncontrolled PM emissions. Further, all three PM standards 
will prevent backsliding by ensuring that all new type design and in-
production aircraft engines will not exceed those regulatory levels in 
the future.
    CAEP meets triennially, and in the future, we anticipate ICAO/CAEP 
considering more stringent aircraft engine PM standards. The U.S. 
Interagency Group on International Aviation (IGIA) facilitates 
coordinated recommendations to the Secretary of State on issues 
pertaining to international aviation (and ICAO/CAEP), and the FAA is 
the chair of IGIA. Representatives of domestic states, non-governmental 
organizations, and industry can participate in IGIA to provide input 
into future standards for ICAO/CAEP. U.S. manufacturers will be better 
prepared for any future standard change due to their experience with 
measuring nvPM mass and number for the first time for these final 
standards. The PM standards adopted in this rulemaking, within the 
larger context of international aircraft standard-setting, send an 
important signal that PM emissions is a factor that manufacturers need 
to consider when building aircraft engines now and going forward--with 
the anticipation that ICAO/CAEP will consider more stringent PM 
standards in the future.
    In response to the comments that the standards are far less 
stringent than PM emission levels of existing aircraft engine 
technologies, the EPA notes that there is a wide range of PM levels for 
in-production aircraft engines. As described in Section VI.C, for some 
manufacturers new technologies aimed at reducing aircraft engine 
NOX, which were implemented for in-production engines that 
were recently built, also resulted in an order of magnitude reduction 
in PM in comparison to most in-service engines. Specifically, the 
current lean-burn engines and some advanced Rich-Quench-Lean (RQL) 
engines developed for the purpose of achieving low NOX 
emissions coincidentally provided order of magnitude reductions in PM 
emissions in comparison to existing RQL engines.\139\ Other 
manufacturers did not develop or implement such technologies that 
resulted in such PM reduction, and thus, their recent in-production 
aircraft engines are not achieving similar PM control. The final PM 
standards are anti-backsliding for these aircraft engines by ensuring 
that they will not exceed the final standards in the future. Further, 
this information shows that available engine technology includes a wide 
range of technologies, and the EPA's final standards are standards that 
can be met by all engines expected to be in production by the 
implementation date of the PM mass and number standards, January 1, 
2023.
---------------------------------------------------------------------------

    \139\ ICAO, 2019: Independent Expert Integrated Technology Goals 
Assessment and Review for Engines and Aircraft, Document 10127. It 
is found on page 34 of the English Edition of the ICAO Products & 
Services 2022 Catalog and is copyright protected; Order No. 10127.
---------------------------------------------------------------------------

    Comment summary:  Some commenters argued that the EPA is not bound 
by the Chicago Convention to adopt standards equivalent to ICAO's 
standards, and relatedly some commenters asserted the EPA is not 
prohibited from adopting standards more stringent than ICAO's 
standards. Some comments argued that the EPA cannot allow international 
agreements to dictate its domestic regulation of PM from aircraft 
engines.
    Response: As explained in the introductory text of Section IV and 
in Section VI, and reiterated throughout the responses to comments, the 
EPA conducted its independent assessment of the appropriateness of the 
ICAO standards for domestic application in the United States and finds 
it appropriate to adopt domestic PM standards aligned with the 
international PM standards in this action. The EPA agrees that the 
United States could adopt standards at a different stringency than 
ICAO's, even more stringent standards. Under the terms of the Chicago 
Convention, ICAO member States must recognize as valid certificates of 
airworthiness issued by other ICAO member States, provided the 
requirements under which such certificates were issued are as least as

[[Page 72339]]

stringent as the minimum ICAO standards.\140\
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    \140\ ICAO, 2006: Convention on International Civil Aviation, 
Article 33, Ninth Edition, Document 7300/9.
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    The need for direct cooperation between countries gave rise to 
ICAO, an active regulatory body that sets and revises standards. As 
described in Section II.B, 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. Compliance with ICAO's standards, including its 
emission standards, is essential to ensure acceptance by other 
countries as people, aircraft, and cargo move in international 
commerce. The EPA recognizes nations have authority to vary from ICAO 
standards, provided they give the required notice. Also, the EPA has 
not concluded that the unique features of the aviation industry 
necessitate a policy to never adopt more stringent emission standards 
compared to ICAO standards. However, adopting more stringent PM 
standards than ICAO's PM standards, which change the approach to 
regulating aircraft engine PM emissions, would risk disruption to 
international cooperation. The EPA considered the timing of the ICAO PM 
mass and number standards for new type design and in-production 
engines, which have a January 1, 2023 implementation date. Given the 
limited time frame and potential implications of the EPA not adopting a 
standard, the EPA has acted reasonably in this rulemaking by giving 
significant weight to the value of international harmonization and to 
the fact that, in the EPA's judgment, international harmonization would 
promote ongoing cooperation to control global pollution of PM.
    Comment summary: Some commenters urged the EPA to withdraw the 
proposed rule and issue a proposed rule that would assess the full 
range of feasible stringency options and propose emission standards 
that reduce aircraft PM emissions.
    Response: The EPA is finalizing the PM standards as proposed. 
However, as explained in Section I.C, the EPA remains committed to 
analyzing this issue and will continue to work with the United States' 
international partners to revisit these standards in the future. We do 
not believe it would be appropriate to withdraw the proposed rule and 
issue a new proposal for the reasons stated in the preceding 
paragraphs.

V. Aggregate PM Inventory Methodology and Impacts

    The PM emissions inventory is presented here to provide information 
on the contribution of aircraft engine emissions to local inventories 
as context for this regulatory effort. This PM emissions inventory is 
from the aviation portion of the EPA's 2017 National Emissions 
Inventory (NEI).141 142 143 The NEI contains comprehensive 
emissions data for criteria pollutants and hazardous air pollutants for 
mobile, point, and nonpoint sources covering both natural and 
anthropogenic contribution to the overall national PM emissions 
inventory. For this PM rulemaking, we updated the aviation portion of 
the PM emissions inventory using newly available measured data reported 
for most in-production engines and an improved approximation method for 
engines without measurement data, as described in this section.
---------------------------------------------------------------------------

    \141\ 2017 National Emissions Inventory: Aviation Component, 
Eastern Research Group, Inc., June 25, 2020, EPA Contract No. EP-C-
17-011, Work Order No. 2-19.
    \142\ 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.
    \143\ U.S. EPA, 2017 National Emissions Inventory (NEI) Data.
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    The inventory is developed from using actual operations at 
airports. The number of aircraft operations or landings and takeoffs 
affects PM emissions that contribute to the local air quality near 
airports. The landing and take-off (LTO) emissions are defined as 
emissions between ground level and an altitude of about 3,000 feet. 
These LTO emissions directly affect the ground level air quality at the 
vicinity of the airport since they are within the local mixing height. 
They are composed of emissions during departure operations (taxi-out 
movement from gate to runway, aircraft take-off run and climb-out to 
3,000 feet), and during arrival operations (approach at or below 3,000 
feet down to landing on the ground and taxi-in from runway to gate). 
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.\144\
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    \144\ 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. 
(page 137.) The air in this mixing height is completely mixed and 
pollutants emitted anywhere within it will be carried down to ground 
level. (page 143.) ``The aircraft operations of interest within the 
[mixing height] are defined as the [LTO] cycle.'' (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.
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    As described in Section III.A, aircraft PM emissions are composed 
of both volatile and non-volatile PM (nvPM) components.\145\ With a 
precisely controlled air-fuel mixture, a typical aircraft engine yields 
combustion products on the order of 27.6 percent water 
(H2O), 72 percent CO2, about 0.02 percent 
SOX, and only about 0.4 percent incomplete residual 
products. These incomplete residual products can be broken down to 84 
percent NOX, 11.8 percent CO, 4 percent unburned 
hydrocarbons (UHC), 0.1 percent PM, and trace amounts of other 
products.\146\ Although the PM emissions are a small fraction of total 
engine exhaust, the composition and morphology of PM are complex and 
dynamic. While the emissions certification test procedures focus only 
on measuring non-volatile PM (black carbon), our emissions inventory 
includes estimates for volatile PM (organic, lubrication oil residues 
and sulfuric acid) as well.
---------------------------------------------------------------------------

    \145\ ICAO: 2019, ICAO Environmental Report. A copy of this 
document is available in the docket for this rulemaking under 
document identification number EPA-HQ-OAR-2019-0660-0022. 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 
emissions 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.)
    \146\ European Monitoring and Evaluation Programme/European 
Environment Agency, Air Pollutant Emission Inventory Guidebook 2019.
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A. Aircraft Engine PM Emissions Modeling Methodologies

    This section describes the nvPM approximation method we used in the 
proposed rulemaking, the use of newly available measured nvPM data, and

[[Page 72340]]

improvement to the nvPM approximation method for the final rulemaking.
1. PM Emission Indices Used in the Rulemaking
    Measured PM data were not available when the EPA first developed 
the 2017 inventory. Thus, to calculate the baseline aircraft engine PM 
emissions, we used the First Order Approximation Version 3.0 (FOA3) 
method defined in the Society of Automotive Engineers (SAE) Aerospace 
Information Report, AIR5715.\147\ For nvPM mass, the FOA3 method is 
based on an empirical correlation of Smoke Number (SN) values and the 
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.\148\ 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 
PM mass (not number).
---------------------------------------------------------------------------

    \147\ SAE Aerospace Information Report, AIR5715, Procedure for 
the Calculation of Aircraft Emissions, 2009, SAE International.
    \148\ Wayson R.L., Fleming G.G., Iovinelli R. Methodology to 
Estimate Particulate Matter Emissions from Certified Commercial 
Aircraft Engines. J Air Waste Management Assoc. 2009 Jan 1; 59(1).
---------------------------------------------------------------------------

    In addition, as described in 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 \149\ and sulfur content. Since the 
total PM is the emission inventory we are estimating for this 
rulemaking, we are including the volatile PM emission estimates from 
the FOA3 method in our emission inventory.
---------------------------------------------------------------------------

    \149\ 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 Emission Indices for Inventory Modeling
    The measurement and reporting of engine EIs allows for improved 
accuracy of engine emission inventories. As mentioned in Section 
IV.D.2, 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 order of 50 percent for nvPM mass and 90 percent for 
nvPM number.\150\ 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.
---------------------------------------------------------------------------

    \150\ Annex 16 Vol. II Appendix 8 Note 2.
---------------------------------------------------------------------------

    The EPA led the effort within the SAE E-31 committee to develop the 
methodology to correct for system losses. The EPA led the development 
of two SAE standards publications, AIR 6504 \151\ and Aerospace 
Recommended Practice (ARP) 6481,\152\ describing this methodology to 
correct for system losses. Also, the EPA funded and led test campaigns 
that verified the methodology.\153\ ICAO has incorporated this same 
procedure into Annex 16 Volume II Appendix 8.
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    \151\ SAE International. 2017. Procedure for the Calculation of 
non-volatile Particulate Matter Sampling and Measurement System 
Penetration Functions and System Loss Correction Factors. Aerospace 
Information Report 6504, Warrendale, PA, October 2017.
    \152\ SAE International. 2019. Procedure for the Calculation of 
Non-Volatile Particulate Matter Sampling and Measurement System 
Losses and System Loss Correction Factors. Aerospace Recommended 
Practice 6481, Warrendale, PA, February 2019.
    \153\ D.B. Kittelson, et al., Experimental verification of 
principal losses in a regulatory particulate matter emissions 
sampling system for aircraft turbine engines, Aerosol Science & 
Technology, 2022, 56, 1, 63-74.
---------------------------------------------------------------------------

    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 EEDB 
and to the EPA.
    When calculating emissions inventories, these corrected EIs are 
used rather than the values used to show compliance with emission 
standards as they are more reflective of what is emitted into the 
atmosphere. These measured EIs are only for the non-volatile component 
of PM, and an approximation method is still required for quantifying 
the volatile PM inventory.
3. Improvements to Calculated Emission Indices
    As described in Section V.A, an improved approximation method has 
also been developed since the EPA's 2017 NEI was first published. This 
new approximation method is needed for modeling PM emissions of in-
service engines that do not have measured PM data. 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.\154\ The 
simultaneously collected data of nvPM mass concentration and smoke 
number from test engines help define a better correlation between nvPM 
mass concentration and smoke number.\155\ The FOA4 estimated nvPM mass 
concentration tracks closely with FOA3's for some smoke numbers, but it 
is much higher for other smoke numbers. Overall, we found that 
fleetwide nvPM mass emissions using the new method (FOA4 and measured 
data when available) increase by 27 percent over the nvPM mass 
emissions reported in 2017 NEI using the FOA3 method. Note that the 
data has significant variation at the individual airport level. For the 
top airports modeled the effect on total PM ranges from a 3 percent 
decrease to a 14 percent increase relative to the modeling in the 
proposed rulemaking.
---------------------------------------------------------------------------

    \154\ 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. It is found on page 78 of the 
English Edition of the ICAO Products & Services 2022 Catalog and is 
copyright protected: Order No. 9889.
    \155\ Agarwal, A. et al., SCOPE11 Method for Estimating Aircraft 
Black Carbon Mass and Particle Number Emissions, Environmental 
Science & Technology, 2019, DOI: 10.1021/acs.est.8b04060.
---------------------------------------------------------------------------

    Recognizing that the development of the first order approximation 
method is not static and continues to evolve, while more accurate 
measurement data and better understanding of the underlying mechanisms 
will certainly help to improve the estimate further, FOA4 represents 
the state of the science today. It has been used to update the nvPM 
baseline emission rates for this final rule.
    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. PM Emission Inventory

    As discussed in the introductory paragraphs of Section V, the PM

[[Page 72341]]

emissions inventory used for this rule is from the aviation portion of 
the EPA's 2017 National Emissions Inventory 
(NEI).156 157 158 The NEI is compiled by the EPA triennially 
based on comprehensive emissions data for criteria pollutants and 
hazardous air pollutants for mobile, point, and nonpoint sources. The 
mobile sources in the NEI include aviation, marine, railroad, on-road 
vehicles, and nonroad engines. As described in Section V.A, the 
aircraft emission estimates in the EPA's 2017 NEI (or the baseline PM 
emissions inventory) are based on the FOA3 method instead of the newly 
developed FOA4 or measured PM emissions data. For the final rulemaking, 
we have updated the baseline PM emissions inventory based on measured 
data reported to the EPA or the European Union Aviation Safety Agency 
(EASA) for most in-production engines and FOA4 for engines without 
measurement data.
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    \156\ 2017 National Emissions Inventory: Aviation Component, 
Eastern Research Group, Inc., June 25, 2020, EPA Contract No. EP-C-
17-011, Work Order No. 2-19.
    \157\ 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.
    \158\ U.S. EPA, 2017 National Emissions Inventory (NEI) Data.
---------------------------------------------------------------------------

    The aviation emissions developed for the NEI include emissions 
associated with airport activities in commercial aircraft, air taxi 
aircraft,\159\ general aviation aircraft, military aircraft, auxiliary 
power units, and ground support equipment. All emissions from aircraft 
with gas turbine engines of rated output greater than 26.7 kN, except 
military aircraft, are used in the emissions inventory for this final 
rule (which is only a subset of the aviation emissions inventory in the 
2017 NEI). 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 \160\ dataset, 2014 Terminal Area 
Forecast (TAF) \161\ data, 2014 Air Traffic Activity Data System 
(ATADS) \162\ data, and 2014 Airport Master Record (form 5010) \163\ 
data.\164\ The NEI used the FAA's Aviation Environmental Design Tool 
(AEDT) \165\ 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, such as 
general aviation or air taxi).\166\
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    \159\ 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.
    \160\ 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.
    \161\ Federal Aviation Administration. Terminal Area Forecast 
(TAF).
    \162\ Federal Aviation Administration. ATADS: Airport 
Operations: Standard Report.
    \163\ Federal Aviation Administration. 2009. Airport Master 
Record Form 5010. Published by GCR & Associates.
    \164\ 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., June 25, 2020, 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).
    \165\ AEDT is a software system that models aircraft performance 
in space and time to estimate fuel consumption, emissions, noise, 
and air quality consequences.
    \166\ See section 4.1.2 of the 2017 National Emissions 
Inventory: Aviation Component, Eastern Research Group, Inc., June 
25, 2020, EPA Contract No. EP-C-17-011, Work Order No. 2-19.
---------------------------------------------------------------------------

    For aircraft PM contribution in 2017 to total mobile PM emissions 
in counties and MSAs 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.
    We respond to comments on the emissions inventory in Section 7 of 
the Response to Comments document.

C. Projected Reductions in PM Emissions

    Due to the technology-following nature of the PM standards, the 
final in-production and new type design standards will not result in 
emission reductions below current levels of engine emissions. The in-
production standards for both PM mass and PM number, which are set at 
levels where all in-production engines meet the standards, will not 
affect any in-production engines as shown in Figure IV-1 and Figure IV-
2. Thus, the in-production standards are not expected to produce 
emission reductions, beyond the business-as-usual fleet turn over that 
would occur in the absence of the standards. The EPA projects that all 
future new type design engines will meet the new type design standards. 
There are a few in-production engines that do not meet the new type 
design standards, but because in-production engines will not be subject 
to these new type design standards, engine manufacturers will not be 
required to make improvements to these engines to meet the standards. 
Therefore, the EPA also does not anticipate emission reductions from 
the new type design standards.
    Most of the in-production engines that do not meet the new type 
design standards are older engines that already have replacement 
engines that will meet the new type design standards. There is only one 
newer in-production engine (an engine that recently started being 
manufactured) that does not meet the new type design standards, and it 
does not currently have a replacement engine. Since the new type design 
standards will not apply to in-production engines, the manufacturer of 
this engine could continue producing and selling its one in-production 
engine that does not meet the new type design standards. Market forces 
might drive the manufacturer of this in-production engine to make some 
improvements to meet the new type design standards, or chose to bring 
forward its next generation new type design engine to the market a few 
years earlier than currently planned. The manufacturer has announced 
plans to develop the next generation of engines to improve emission 
levels compared to the previous generation of 
engines.167 168 We expect that these next generation engines 
from this manufacturer will meet the new type design standards. Further 
details on market forces are provided in Section VI.A. In conclusion, 
when considering the final new type design standards in the context of 
the in-production engines that already have a replacement engine or the 
one in-production engine that does not, the EPA expects no emission 
reductions from the new type design standards.
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    \167\ https://www.rolls-royce.com/products-and-services/civil-aerospace/future-products.aspx#/; last accessed on October 31, 2022.
    \168\ Aviation Week, Rolls-Royce Considers UltraFan Development 
Pause, Guy Norris, January 4, 2021.
---------------------------------------------------------------------------

    All website addresses for references cited in this section are 
provided in a memorandum to the docket.\169\
---------------------------------------------------------------------------

    \169\ U.S. EPA, Yen, D. Memorandum to Docket EPA-HQ-OAR-2019-
0660, ``website addresses for references cited in Section V of the 
Preamble for Control of Air Pollution from Aircraft Engines: 
Emission Standards and Test Procedures; Final Rule,'' November 9, 
2022.
---------------------------------------------------------------------------

VI. Technological Feasibility and Economic Impacts

    As described in Section IV, we are adopting PM mass concentration, 
PM mass, and PM number standards that match ICAO's standards. As 
discussed 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

[[Page 72342]]

standards are set at emission levels where all in-production engines 
meet these standards. Thus, there will not be costs or emission 
reductions associated with the final standards for in-production 
engines. For new type design 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 design standards. In addition, 
in-production engines will not be required to meet these new type 
design standards. Only new type design engines will need to comply with 
the new type design standards. The EPA projects that all new type 
design engines entering into service into the future will meet these PM 
mass and number standards. Thus, the EPA expects that there will not be 
costs and emission reductions from the standards for new type design 
engines, although the standards would likely prevent backsliding for 
some new type design engines. In addition, following this final 
rulemaking for the PM standards, the FAA will issue a rulemaking to 
enforce compliance to these standards, and any anticipated 
certification costs for the PM standards will be accounted for in the 
FAA rulemaking.
    As described in Section I.B.2, when developing new emission 
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 final 
standards that match ICAO's standards are anti-backsliding standards 
that prevent aircraft engine PM levels from increasing beyond their 
current levels. As discussed in Section IV.F.2, in that regard, PM mass 
and number are currently unregulated from aircraft engines and the 
standards finalized in this action represent a new regulatory backstop 
of those two new standards. Further, all three PM standards will 
prevent backsliding by ensuring that all new type design and in-
production aircraft engines will not exceed those regulatory levels in 
the future.
    As described in Section IV.F.2, for some manufacturers, new 
technologies aimed at reducing aircraft engine NOX, which 
were implemented for in-production engines that were recently built, 
also resulted in significant PM reductions. Other manufacturers did not 
develop or implement technologies that resulted in such PM reductions. 
In either case, the final PM standards ensure that PM emissions do not 
increase beyond the levels of these PM standards. In addition, the 
final PM standards send an important signal to manufacturers that they 
need to consider PM emissions when producing aircraft engines now and 
going forward--with the anticipation that more stringent PM standards 
will be adopted by ICAO/CAEP in the future.
    U.S. manufacturers could be at a significant disadvantage if the 
United States fails to adopt standards by the international 
implementation date, January 1, 2023. Also, given the short timeframe 
from this final action and the international implementation date, there 
would not be enough lead time for manufacturers to respond to more 
stringent standards that would require them to develop and implement 
new technologies.

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 the EPA rulemaking and subsequent FAA 
rulemaking enables U.S. manufacturers to obtain internationally 
recognized U.S. certification, which for the final PM standards will 
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 will 
be removed. The rulemaking will help ensure 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 likely 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 final standards will 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 any technology demonstrated to be safe 
and airworthy proven to Technology Readiness Level \170\ (TRL) 8 and 
available for application over a sufficient range of newly certificated 
aircraft.\171\ This means that the analysis that informed the 
international standard considered the emissions performance of aircraft 
engines assumed to be in-production on the ICAO/CAEP implementation 
date for the PM mass and number standards, January 1, 2023.\172\ 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.)
---------------------------------------------------------------------------

    \170\ 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.
    \171\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15 
February 2019, Committee on Aviation Environmental Protection, 
Document 10126, CAEP/11. It is found on page 27 of the English 
Edition of the ICAO Products & Services 2022 Catalog and is 
copyright protected: Order No. 10126. The statement on technological 
feasibility is located in Appendix C of Agenda Item 3 of this report 
(see page 3C-4, paragraph 2.2).
    \172\ Id., 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),\173\ 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

[[Page 72343]]

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.\174\ 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.
---------------------------------------------------------------------------

    \173\ Id.
    \174\ ICAO, 2019: Independent Expert Integrated Technology Goals 
Assessment and Review for Engines and Aircraft, Document 10127. It 
is found on page 34 of the English Edition of the ICAO Products & 
Services 2022 Catalog and is copyright protected; Order No. 10127.
---------------------------------------------------------------------------

    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 non-volatile PM (nvPM) 
mass and nvPM number in comparison to most in-service engines.\175\ (As 
described in Section IV.D.2, only nvPM emissions will be measured in 
the final test procedure for the final standards.) Specifically, the 
current lean-burn engines and some advanced Rich-Quench-Lean (RQL) 
engines 176 177 developed for the purpose of achieving low 
NOX emissions coincidentally provide order of magnitude 
reductions in nvPM emissions in comparison to existing RQL 
engines.\178\ However, achieving these levels of nvPM emissions is more 
difficult for physically smaller-sized engines due to technical 
constraints.\179\ In addition, some previous generation engines that 
are in production meet the final new type design 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 final standards, 
which match ICAO standards, are technologically feasible.
---------------------------------------------------------------------------

    \175\ See id. at 8.
    \176\ See id. at 47 and 48. For lean-burn engines (or 
combustors), enough air is introduced with the fuel from the 
injector so it is never overall rich. For aviation combustors, the 
fuel is not premixed and pre-vaporized, and in the microscopic 
region around each droplet, the mixture can be near to 
stoichiometric. Yet, the mixture remains lean throughout the 
combustor, and the temperature does not approach the stoichiometric 
value. For a lean-burn combustor, the peak temperatures are not as 
high, and thus, the NOX is low.
    \177\ See id. at 47. For Rich-Quench-Lean (RQL) engines (or 
combustors), the fuel first burns rich, and thus, there is little 
oxygen free to form NOX. Dilution air is introduced to 
take the mixture as quickly as possible through the stoichiometric 
region (when it briefly becomes very hot) to a cooler, lean state.
    \178\ See id. at 57 and 58. 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. Also, 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.
    \179\ 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 
emission control. See 77 FR 36342, 36353 (June 18, 2012).
---------------------------------------------------------------------------

D. Costs Associated With the Rule

    The EPA does not anticipate new technology costs (non-recurring 
costs) due to the final rule. As described in the introductory 
paragraph of Section VI, since all in-production engines meet the in-
production standards and nearly all in-production engines meet these 
new type design standards, we project there will not be costs, nor 
emission reductions, from the final rule. Also, because current in-
production engines will not be required to make any changes under this 
final 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 final new 
type design standards since all manufacturers currently have engines 
that meet that level.
    Following this final rulemaking for the PM standards, the FAA will 
issue a rulemaking to enforce compliance to these standards, and any 
anticipated certification costs for the PM standards will be estimated 
by FAA.
    As described in Section VI.A, manufacturers have already developed 
or are developing technologies to respond to ICAO standards that are 
equivalent to the final standards, and they will comply with the ICAO 
standards in the absence of U.S. regulations. Also, domestic 
implementation of the ICAO standards will potentially provide for cost 
savings to U.S. manufacturers since it will enable them to certify 
their aircraft engine (via subsequent FAA rulemaking) domestically 
instead of having to certificate with a foreign authority (which will 
occur without this EPA rulemaking). If the final PM standards, which 
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.\180\ Any potential costs or cost savings related to 
certification will be estimated by FAA.
---------------------------------------------------------------------------

    \180\ 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 will be no non-recurring and 
certification costs for the rule, there also will be no recurring costs 
(recurring operating and maintenance costs) for the rule. The elements 
of recurring costs include additional maintenance, material, labor, and 
tooling costs.
    As described in Section IV.E, the EPA is formally incorporating the 
PM aspects of the existing information collection request (ICR) into 
the CFR (or regulations) in 40 CFR 1031.150 and 1031.160. This action 
will not create a new requirement for the manufacturers of aircraft 
engines. Instead, it will 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 action will not 
create new costs.

E. Summary of Benefits and Costs

    The final standards match the ICAO standards, and as discussed in 
Section II.C and Section IV.F.1 of this preamble, ICAO intentionally 
established its standards at a level which is technology following. The 
final rule takes an appropriate step in controlling aircraft engine PM 
emissions and prevents backsliding by ensuring that all in-production 
and new type design engines have at least the PM emission levels of 
today's aircraft engines. Additionally, this final rule maintains 
consistency or harmonizes with the international standards and meets 
the United States' treaty obligations under the Chicago Convention. 
Also, it allows U.S. manufacturers of covered aircraft engines to 
remain competitive in the global marketplace by ensuring the acceptance 
of their engines worldwide (which benefits U.S. manufacturers and 
consumers), provides uniformity and

[[Page 72344]]

certainty to U.S. manufacturers as they become familiar with the new 
approach to adhering to these PM standards and test procedures,\181\ 
and prevents U.S. manufacturers from having to seek PM emissions 
certification from an aviation certification authority of another 
country (not the FAA) to market and operate their aircraft engines 
internationally. All engines currently manufactured will meet the ICAO 
in-production standards, and nearly all these same engines will meet 
the new type design standards--even though these new type design 
standards do not apply to in-production engines. Therefore, as further 
described in the introductory paragraph of Section VI and in Section 
VI.C, there will be no costs and no emission reductions from complying 
with these final standards.
---------------------------------------------------------------------------

    \181\ The final standards change the approach to regulating 
aircraft engine PM emissions from past smoke measurements to the 
measurement of mass and number for the first time for U.S. 
manufacturers.
---------------------------------------------------------------------------

VII. Technical Amendments

    In addition to the PM-related regulatory provisions discussed in 
Section IV, the EPA is finalizing technical amendments to the 
regulatory text that apply more broadly than to just the new PM 
standards. First, the EPA is migrating 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 restructuring the regulations to 
allow for better ease of use and allow for more efficient future 
updates. The EPA is also deleting some regulatory provisions and 
definitions that are unnecessary, as well as making several other minor 
technical amendments to the regulations. Finally, the EPA is also 
revising 40 CFR part 87 to provide continuity during the transition of 
40 CFR part 87 to 40 CFR part 1031. In this final rule, the EPA did not 
reexamine or reopen the substantive provisions of 40 CFR part 87 that 
were merely migrated to the new 40 CFR part 1031 and streamlined or the 
substantive provisions of 40 CFR part 1030 and 40 CFR part 1031 beyond 
those specially discussed in the proposed rule. Any comments we 
received on the substance of the provisions migrated from 40 CFR part 
87 to 40 CFR part 1031 provisions, as opposed to comments pointing out 
typos or inadvertent impacts on substantive provisions caused by the 
regulatory streamlining, are beyond the scope of this rulemaking.

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 finalized in this document, as well as any future standards 
the EPA may adopt, difficult to incorporate.
    Therefore, the EPA is migrating 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 restructuring, streamlining, and clarifying the 
regulatory provisions for ease of use and to facilitate more efficient 
future updates. Finally, the EPA is deleting 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.
    As noted in the amendatory instructions in the regulations, the EPA 
is making this transition effective on January 1, 2023. The new 40 CFR 
part 1031 will become effective (i.e., be incorporated into the Code of 
Federal Regulations) 30 days following the publication of this final 
rule in the Federal Register. However, the applicability language in 40 
CFR 1031.1 indicates that the new 40 CFR part 1031 will apply to 
engines subject to the standards beginning January 1, 2023. Prior to 
January 1, 2023, the existing 40 CFR part 87 will continue to apply. On 
January 1, 2023, the existing 40 CFR part 87 will be replaced with a 
significantly abbreviated version of 40 CFR part 87 whose sole purpose 
will 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 will 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 adopting language in 40 
CFR part 87 that simply states the provisions relating to a particular 
section of 40 CFR part 87 apply as described in a corresponding section 
of the new 40 CFR part 1031.
    The EPA received a comment regarding some existing equations being 
incorrectly migrated from 40 CFR part 87 to the new 40 CFR part 1031. 
Specifically, the equations in the proposed 40 CFR 1031.40(a)(1), 
1031.50(a)(1), and 1031.90(a)(1), (b) and (c) contained terms that 
should have been exponents but were instead expressed as multiplicative 
terms. Given that the EPA's stated intent with the proposed migration 
from 40 CFR part 87 to 40 CFR part 1031 was to move, restructure, 
streamline and clarify the existing regulations without changing the 
underlying regulatory requirements, the equations contained in the 
paragraphs in 40 CFR part 1031 should have aligned with the 
corresponding equations in 40 CFR part 87. Thus, these equations in 40 
CFR part 1031 have been accordingly corrected in this final rule.

B. Deletion of Unnecessary Provisions

    As previously mentioned, the existing aircraft engine emission 
regulations contain some unnecessary provisions which the EPA is 
deleting. These 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 not migrating 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 effectively 
deleting these provisions by not migrating them to the new 40 CFR part 
1031, the underlying standards referred to in these provisions (i.e., 
the Tier 4 and 6 NOX standards) remain unchanged. Thus, the 
underlying certification basis for any engines

[[Page 72345]]

certificated under these provisions will remain intact.
    The EPA is also deleting several definitions from the current 40 
CFR part 87 as it is migrated to the new 40 CFR 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 stand-alone definition unnecessary. 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 is deleting and the reasons for the 
deletions are listed in Table VII-1.

  Table VII-1--List of Terms for Which Definitions Will Be Deleted From
                                 the CFR
------------------------------------------------------------------------
                  Term                         Reason for deletion
------------------------------------------------------------------------
Act....................................  Not used in the regulatory
                                          text.
Administrator..........................  No longer needed as not used in
                                          revised and streamlined
                                          regulatory text.
Class TP...............................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Class TF...............................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Class T3...............................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Class T8...............................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Class TSS..............................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Commercial aircraft....................  No longer needed as not used in
                                          revised and streamlined
                                          regulatory text.
Commercial aircraft gas turbine engine.  No longer needed as not used in
                                          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
                                          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
                                          revised and streamlined
                                          regulatory text.
Production cutoff or the date of         No longer needed with deletion
 production cutoff.                       of unnecessary exemption
                                          provisions and streamlining of
                                          exemption regulatory text.
Tier 0.................................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Tier 2.................................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Tier 4.................................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Tier 6.................................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
Tier 8.................................  No longer needed as definition
                                          was effectively incorporated
                                          into regulatory text during
                                          migration.
U.S.-registered aircraft...............  Unnecessary term that is not
                                          used in the regulatory text.
------------------------------------------------------------------------

    The EPA is also not migrating the current 40 CFR 87.3(b) to the new 
40 CFR part 1031, which in effect results in its deletion. This 
paragraph is simply a restatement of an obligation directly imposed 
under the Clean Air Act that 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 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 
adopting some minor technical amendments to the regulations.
    The EPA is adding 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 
definitions will help provide clarity to the provisions that utilize 
those terms.
    The EPA is modifying the definitions for ``Exception'' and 
``Exemption.'' The current definitions of these terms in 40 CFR 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 being moved to the introductory text in 1031.15 and 
1031.20, as applicable. These changes are in no way intended to change 
any regulatory requirement applicable to excepted or exempted engines. 
Rather, they are intended simply to more clearly separate definitions 
from the related regulatory requirements.
    The EPA is not migrating the existing 40 CFR 87.42(d) to the new 40 
CFR part 1031, which in effect results in the deletion of this 
provision. This paragraph related to the annual production report 
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 40 CFR 1031.170). This change will have no impact on 
the ability of manufacturers to make claims of CBI, or in the EPA's 
handling of such claims. However, it will assure a more consistent 
treatment of CBI across mobile source programs.
    The EPA is adopting a minor change to the existing emission 
requirements

[[Page 72346]]

for spare engines, as found in the existing 40 CFR 87.50(c)(2). In the 
regulatory text for 40 CFR 1031.20(a), the EPA is deleting 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 retaining and migrating to 40 CFR part 1031 the requirement 
in 40 CFR 87.50(c)(3) such that a spare engine will need to be 
certificated to emission standards equal to or lower than those of the 
engines they are replacing, for all regulated pollutants. This deletion 
of 40 CFR 87.50(c)(2) aligns 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 change will 
have any impact on current industry practices. Deleting the provision 
currently in 40 CFR 87.50(c)(2) will leave in place the requirement 
that any new engine manufactured as a spare will 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 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 
deletion will 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 effective deletion of 40 CFR 87.50(c)(2) for the purposes of 
uniformity will have any practical impact on current industry 
practices.
    The EPA is aligning 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.\182\ 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 
in that 2012 action. Thus, the EPA is applying 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 
consistent with U.S. efforts to secure the highest practicable degree 
of uniformity in aviation regulations and standards and will 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 will be covered by the existing smoke number 
standard. Throughout its regulations, the EPA is aligning with ICAO 
regarding a common rated output threshold for emission regulations. The 
applicability and 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 
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 
EPA is making all instances in the new 40 CFR 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 change 
will 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.
---------------------------------------------------------------------------

    \182\ 77 FR 36342 (June 18, 2012).
---------------------------------------------------------------------------

    The EPA is incorporating by reference Appendix 1 of ICAO 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 the complete testing and compliance provisions are 
clear.
    The EPA is streamlining, restructuring, and updating 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 
migrating the exceptions section concerning spare engines (40 CFR 
87.50(c)) to 40 CFR 1031.20(a), with the changes discussed in the 
preceding paragraphs. The provisions regarding the annual reporting of 
exempted and excepted engines are being incorporated into the new 
annual reporting 40 CFR 1031.150. These reporting provisions otherwise 
remain unchanged. Section 87.50(a), regarding engines installed on new 
aircraft, and 40 CFR 87.50(b), regarding temporary exemptions based on 
flights for short durations at infrequent intervals, are being migrated 
to a new 40 CFR 1031.15. The temporary exemptions provisions remain 
unchanged, with the exception of adding ``of Transportation'' after 
``Secretary'' in 40 CFR 1031.15(b)(4) to improve clarity. The 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.\183\ These provisions were only available 
through December 31, 2016, and they are being deleted in this action. 
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 40 CFR 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 
deleting them rather than migrating them to the new 40 CFR 1031.15. The 
EPA is further restoring the general exemption provisions that were 
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.\184\ 
The EPA is adopting similarly streamlined general exemption provisions 
for aircraft engines as well, as contained in 40 CFR 1031.15(a).
---------------------------------------------------------------------------

    \183\ 77 FR 36342 (June 18, 2012).
    \184\ 86 FR 2136 (January 11, 2021).
---------------------------------------------------------------------------

    The EPA is adopting some changes relative to the prohibition on 
fuel venting. The fuel venting standard is

[[Page 72347]]

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 40 CFR 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 deleting the definition for 
fuel venting emissions as both unnecessary and contradictory to the 
actual requirement.
    The EPA is adding the word `liquid' in front of the phrase ``fuel 
emissions'' in 40 CFR 1031.30(b)(2). That phrase has been interpreted 
internationally in significantly different ways. Some have interpreted 
the word ``emissions'' to mean any emission of pollutants from the 
combustion process. The EPA's rule that promulgated the requirement to 
control fuel venting emissions, however, dates to 1973 and was intended 
to address the issue of liquid fuel being released from an aircraft 
engine after engine shutdown when no combustion processes are 
occurring.\185\ This term addresses both liquid fuel that reaches the 
ground, and liquid fuel released from the engine after shutdown that 
comes into contact with hot engine parts and begins to vaporize or 
evaporate into the atmosphere rather than combust. In the latter 
situation, fuel venting emissions may be observed visually and may look 
like an engine is smoking. To reduce confusion, the EPA is adding the 
word ``liquid'' to this description. Nothing about the intent of the 
fuel venting rule is changed by this addition. The change is intended 
only to better describe the phenomenon of fuel venting emissions and 
will harmonize U.S. regulations with the term as used in ICAO Annex 16 
Volume II.
---------------------------------------------------------------------------

    \185\ See 38 FR 19088 (July 17, 1973).
---------------------------------------------------------------------------

    The EPA is modifying the applicability date language associated 
with the standards applicable to Tier 8 engines, as contained in 
1031.60(e)(2). The applicability of new type design standards has 
traditionally been linked to the date of the first individual 
production engine of a given type, both for the 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 design began to 
determine to what standards a new type design 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 
type designs. 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 to establish the 
certification basis for type certification in the future. This approach 
is reflected in the applicability date provisions of the PM standards 
being adopted in this action, consistent with ICAO. The EPA is also 
adopting it in 40 CFR 1031.60(e)(5) for existing standards applicable 
to Tier 8 engines as well. This change will only impact engines for 
which an application for an original or amended type certificate is 
submitted to the FAA in or after January 1, 2023. This change will 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 change in applicability will not result in a change in standards 
for any engines, and it 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 will be 
straightforward.
    The EPA is revising 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 verify compliance of engines certificated outside 
the United States, as indicated through existing bilateral agreements 
with such authorities. Also, the EPA is updating its definition of 
``supersonic'' by replacing it with a new definition of ``supersonic 
airplane.'' The new definition for ``supersonic airplane'' is based on 
a revised definition for such proposed by the FAA in a recent proposed 
action regarding noise regulations for supersonic airplanes.\186\ This 
new definition will provide greater assurance that the standards 
applicable to engines used on supersonic airplanes will apply to the 
engines for which they are intended.
---------------------------------------------------------------------------

    \186\ Noise Certification of Supersonic Airplanes, 85 FR 20431 
(April 13, 2020).
---------------------------------------------------------------------------

    The EPA is updating several definitions and aligning them with 
definitions included in the recent airplane GHG regulations.\187\ The 
definitions being updated are for ``Aircraft,'' ``Aircraft engine,'' 
``Airplane,'' ``Exempt,'' and ``Subsonic.'' These definitions are being 
updated in the aircraft engine regulations simply for consistency with 
the airplane GHG regulations and with FAA regulations. The changes 
being adopted will not have any impact on the regulatory requirements 
related to the definitions.
---------------------------------------------------------------------------

    \187\ 86 FR 2136 (January 11, 2021).
---------------------------------------------------------------------------

    The EPA is also addressing an unintentional applicability gap 
related to the 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 a maximum takeoff mass (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 adopting new language at 40 
CFR 1030.1(a)(1)(ii) to cover these airplanes, should they be produced. 
This change will 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 in ICAO's GHG standard-setting 
process and had been intended to be subject to the EPA's GHG standards 
as well. The structure of 40 CFR 1030.1(a)(1) being finalized is 
somewhat different than the structure that was proposed to conform to 
numbering conventions used by the Office of the Federal Register. This 
renumbering does not change the meaning or requirements from the 
language that was proposed.
    The EPA is correcting 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

[[Page 72348]]

retroactively apply these standards using the ICAO new type design 
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 design standards for other categories of airplanes in this part 
(e.g., 40 CFR 1030.1(a)(1)). Based on consultations with the FAA, this 
change to 40 CFR part 1030 will not impact any airplanes.
    The EPA is adopting a minor word change to the existing 
applicability language in 40 CFR part 1030 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 replacing 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 language in 40 CFR 1031.1(b)(1), and existing 
FAA regulations in 14 CFR parts 1 and 33. This change is for 
consistency among Federal regulations and to avoid any confusion that 
may be caused by using two different terms. This change will have no 
material impact on the meaning of the regulatory text.
    Following consultation with FAA, the EPA is finalizing some 
clarifying changes to the proposed provisions related to derivative 
engines for emissions certification purposes. None of these edits 
change the fundamental regulatory provisions at hand, but rather serve 
to clarify the requirements and improve consistency between EPA and FAA 
regulations. Thus, these changes will have no effect on obligations of 
regulated parties or on implementing these regulations. In 40 CFR 
87.48, the EPA inserted ``for emissions certification purposes'' to 
properly direct the reader to the correct section of the new 40 CFR 
part 1031. Most of these changes are in 40 CFR 1031.130(a), and include 
replacing ``type certificate holder'' with ``applicant'' to better 
reflect who would request a designation as a derivative engine for 
emissions certification purposes (this change was also made to 40 CFR 
1031.130(c)), a change from ``the FAA may approve'' to ``a type 
certificate holder may request'' to better reflect the actual process, 
the inclusion of the phrase ``derived from'' which was in both 14 CFR 
34.48 and 40 CFR 87.48, but was inadvertently left out of this 
paragraph in the proposed migration of the regulatory text, inclusion 
of the word ``type'' to clarify the design that is being referred to, 
and the replacement of ``previously certificated (original) engine for 
purposes of compliance with exhaust emission standards'' with ``an 
engine that has a type certificate issued in accordance with 14 CFR 
part 33'' to more precisely indicate that these provisions apply to 
engines previously certificated under the FAA's engine certification 
regulations. The EPA is also clarifying 40 CFR 1031.130(c)(2) by adding 
``for individual certification applications'' and ``beyond those,'' and 
clarifying that the FAA should make determinations on using ranges 
beyond those specified in the regulation consistent with good 
engineering judgement rather than following consultation with the EPA. 
Finally, the EPA is revising the proposed definition for ``derivative 
engine for emissions certification purposes'' in 40 CFR 1031.205 by 
replacing a description of the requirements of 40 CFR 1031.130 with an 
actual reference to 40 CFR 1031.130, and other editorial changes to 
make it consistent with the changes to 40 CFR 1031.130 discussed in 
this paragraph.
    The EPA is making a correction to the proposed regulatory text of 
40 CFR 87.50. In the NPRM, an incorrect reference was included to 40 
CFR 1031.11. The correct reference is 40 CFR 1031.20. The text of 40 
CFR 87.50 has been updated accordingly.
    Finally, the EPA is finalizing minor changes to the proposed 
regulatory text in 40 CFR 1031.140(f)(1) and (f)(2)(i). As stated in 
the preamble to the proposed rule, the existing smoke standards and the 
proposed PM mass concentration standard are all based on the maximum 
value measured at any thrust level across and engine's entire operating 
thrust range.\188\ While it is clear from this preamble language that 
these standards refer to the maximum value measured at any thrust level 
across an engine's operating thrust range, and not just at one of the 
four LTO points, the regulatory text referenced in this paragraph is 
perhaps less clear on this point. Thus, the EPA is finalizing slight 
modifications to the regulatory text in these sections to further 
clarify the regulatory requirement. Specifically, the EPA is adding 
``across the engine operating thrust range'' to the end of 40 CFR 
1031.140(f)(1) and is replacing the phrase ``at any thrust setting'' 
with ``across the engine operating thrust range'' in 40 CFR 
1031.140(f)(2)(i). Also in 40 CFR 1031.140, the EPA is adding ``percent 
of'' to 40 CFR 1031.140(f)(2)(ii) and (f)(3) to provide additional 
clarity without changing the underlying meaning of the regulatory text.
---------------------------------------------------------------------------

    \188\ As stated in the proposal to this rule: ``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.'' 87 FR 
6343 (February 3, 2022).
---------------------------------------------------------------------------

VIII. Statutory Authority and Executive Orders 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 final action is not a significant regulatory action and was 
therefore not submitted to the Office of Management and Budget (OMB) 
for review.

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 rule codifies that existing collection 
by including the current nvPM data collection in the regulatory text, 
but it will 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 new provisions 
contained in this document (i.e., engines greater than 26.7 kN rated 
output). Therefore, this action will not impose any requirements on 
small entities. Supporting information can be found in the docket.\189\
---------------------------------------------------------------------------

    \189\ U.S. EPA, Mueller, J. Memorandum to Docket ID No. EPA-HQ-
OAR-2019-0660, ``Determination of no SISNOSE for Final Aircraft 
Engine Emission Standards,'' August 19, 2022. This memorandum 
describes that the only small entity is Williams Int'l, which only 
make engines below 26.7 kN, and does not make engines for use in 
civil supersonic airplanes. Thus, they are not subject to the final 
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.

[[Page 72349]]

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 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. The 
EPA believes that the environmental health risks or safety risks of 
particulate matter, which is addressed by this action, may have a 
disproportionate effect on children. The 2021 Policy on Children's 
Health also applies to this action. This action's health and risk 
assessments are contained in Section III. Children make up a 
substantial fraction of the U.S. population, and often have unique 
factors that contribute to their increased risk of experiencing a 
health effect from exposures to ambient air pollutants because of their 
continuous growth and development. Children are more susceptible than 
adults to many air pollutants because they have (1) a developing 
respiratory system, (2) increased ventilation rates relative to body 
mass compared with adults, (3) an increased proportion of oral 
breathing, particularly in boys, relative to adults, and (4) behaviors 
that increase chances for exposure.

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

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR 
Part 51

    This action involves technical standards for testing emissions from 
aircraft gas turbine engines. The EPA is adopting test procedures 
contained in ICAO's Annex 16 to the Convention on International Civil 
Aviation, Environmental Protection, Volume II--Aircraft Engine 
Emissions, Fourth Edition, July 2017, 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 emission 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 1031.140(a)  Test method
 Emissions, Annex 16, Volume II,   and 1031.205.       describes how to
 Fourth Edition, July 2017, as                         measure PM,
 amended by Amendment 10,                              gaseous, and
 January 1, 2021.                                      smoke emissions
                                                       from aircraft
                                                       engines.
------------------------------------------------------------------------

    The version of the ICAO Annex 16, Volume II, that is being 
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). This final rule removes those references 
to ICAO Annex 16, Volume II.
    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

    Executive Order 12898 (59 FR 7629, February 16, 1994) directs 
Federal agencies, to the greatest extent practicable and permitted by 
law, to make 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 (people of color and/or Indigenous 
peoples) and low-income populations.
    The EPA believes that the human health or environmental conditions 
that exist prior to this action result in or have the potential to 
result in disproportionate and adverse human health or environmental 
effects on people of color, low-income populations and/or Indigenous 
peoples. The EPA provides a summary of the evidence for potentially 
disproportionate and adverse effects among people of color and low-
income populations residing near airports in Section III.G.
    The EPA believes that this action is not likely to change existing 
disproportionate and adverse effects on people of color, low-income 
populations and/or Indigenous peoples, as specified in Executive Order 
12898. The information supporting this Executive Order review is 
contained in Section III.G, and all supporting documents have been 
placed in the public docket for this action.
    This action will not achieve emission reductions and will therefore 
result in no improvement in per-aircraft emissions for all communities 
living near airports. The 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. The EPA, in 
an analysis separate from this rulemaking, is conducting an analysis of 
the communities residing near airports where jet aircraft operate 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.

[[Page 72350]]

    The EPA additionally engaged with Environment Justice organizations 
in several ways for this rulemaking, including: (1) contacting members 
of Environmental Justice organizations to provide information on pre-
registration for the public hearings for the proposed rule; (2) 
contacting members of Environmental Justice organizations when the 
proposed rule was published in the Federal Register to provide an 
overview of the proposed action and to explain methods for commenting 
on the proposal; this outreach included sessions during evening hours; 
(3) providing information on our website in both Spanish and English, 
as well as providing access to Spanish translation during the public 
hearings for the rule, if requested.

K. Congressional Review Act

    This action is subject to the CRA, and the EPA will submit a rule 
report to each House of the Congress and to the Comptroller General of 
the United States. This action is not a ``major rule'' as defined by 5 
U.S.C. 804(2).

List of Subjects

40 CFR Part 9

    Reporting and recordkeeping requirements.

40 CFR Part 87

    Environmental protection, Aircraft, Air pollution control.

40 CFR Part 1030

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

40 CFR Part 1031

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

Michael S. Regan,
Administrator.

    For the reasons set forth in the preamble, the EPA is amending 
title 40, chapter I of the Code of Federal Regulations as set forth 
below.

PART 9--OMB APPROVALS UNDER THE PAPERWORK REDUCTION ACT

0
1. The authority citation for part 9 continues to read as follows:

    Authority: 7 U.S.C. 135 et seq., 136-136y; 15 U.S.C. 2001, 2003, 
2005, 2006, 2601-2671; 21 U.S.C. 331j, 346a, 31 U.S.C. 9701; 33 
U.S.C. 1251 et seq., 1311, 1313d, 1314, 1318, 1321, 1326, 1330, 
1342, 1344, 1345 (d) and (e), 1361; E.O. 11735, 38 FR 21243, 3 CFR, 
1971-1975 Comp. p. 973; 42 U.S.C. 241, 242b, 243, 246, 300f, 300g, 
300g-1, 300g-2, 300g-3, 300g-4, 300g-5, 300g-6, 300j-1, 300j-2, 
300j-3, 300j-4, 300j-9, 1857 et seq., 6901-6992k, 7401-7671q, 7542, 
9601-9657, 11023, 11048.

0
2. Amend Sec.  9.1 in the table by adding the undesignated center 
heading entitled ``Control of Air Pollution From Aircraft Engines'' and 
entries for sections ``1031.150'' and ``1031.160'' in numerical order 
to read as follows:

Sec.  9.1  OMB approvals under the Paperwork Reduction Act.

* * * * *

------------------------------------------------------------------------
             40 CFR  citation                     OMB  control No.
------------------------------------------------------------------------
 
------------------------------------------------------------------------
                              * * * * * * *
             Control of Air Pollution From Aircraft Engines
------------------------------------------------------------------------
1031.150..................................  2060-0680
1031.160..................................  2060-0680
 
                                * * * * *
------------------------------------------------------------------------

0
3. Revise part 87 to read as follows:

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

Sec.
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.

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 for emissions 
certification purposes apply as described in 40 CFR 1031.130.

Sec.  87.50  Exemptions and exceptions.

    Provisions related to exceptions apply as described in 40 CFR 
1031.20. 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
4. The authority citation for part 1030 continues to read as follows:

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

[[Page 72351]]

0
5. Amend Sec.  1030.1 by revising paragraphs (a) introductory text, 
(a)(1), (a)(3)(ii), and (c)(7) to 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 14 CFR chapter I, the 
airplane may not exceed the Greenhouse Gas (GHG) standards of this part 
when original civil certification under 14 CFR chapter I is sought.
    (1) A subsonic jet airplane that has --
    (i) Either--
    (A) A type-certificated maximum passenger seating capacity of 20 
seats or more,
    (B) A maximum takeoff mass (MTOM) greater than 5,700 kg, and
    (C) An application for original type certification that is 
submitted on or after January 11, 2021;
    (ii) Or--
    (A) A type-certificated maximum passenger seating capacity of 19 
seats or fewer,
    (B) A MTOM greater than 60,000 kg, and
    (C) An application for original type certification that is 
submitted on or after December 23, 2022.
* * * * *
    (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
6. Add part 1031 to read as follows:

PART 1031--CONTROL OF AIR POLLUTION FROM AIRCRAFT ENGINES

Subpart A--Scope and Applicability
Sec.
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 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

[[Page 72352]]

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\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. 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\

    (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. Engines of a type or model for which the date of 
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\

    (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\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

[[Page 72353]]

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\16
                                   6.914[middot]rO.    \-
                                                       8.080[middot]10\1
                                                       3\[middot]rO
rO > 150........................  214.0.............  2.780[middot]10\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\16
                                   21.497[middot]rO.   \-
                                                       1.126[middot]10\1
                                                       4\[middot]rO
rO > 200........................  347.5.............  4.170[middot]10\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[middot]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[middot]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 +
                                 89.                1.6[middot]rPR-
                                                    0.2087[middot]rO
                                (B) rO > 89......  19 + 1.6[middot]rPR
(ii) 30 < rPR < 62.5..........  (A) 26.7 < rO <=   42.71 +
                                 89.                1.4286[middot]rPR-
                                                    0.4013[middot]rO +
                                                    0.00642[middot]rPR[m
                                                    iddot]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

[[Page 72354]]

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
----------------------------------------------------------------------------------------------------------------
                                           and the rated output (kN)     the NOX emission standard (g/kN) is--
 If the rated pressure ratio (rPR) is--               is--
----------------------------------------------------------------------------------------------------------------
(i) rPR <= 30...........................  (A) 26.7 < rO <= 89........  40.052 + 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 <= 89........  41.9435 + 1.505[middot]rPR-
                                                                        0.5823[middot]rO +
                                                                        0.005562[middot]rPR[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. 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\

    (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]0.92\rPR\

    (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. For purposes of compliance with exhaust emission 
standards of this part, a type certificate applicant may request from 
the FAA a determination that an engine configuration be considered a 
derivative engine for emissions certification purposes. The applicant 
must demonstrate that the configuration is derived from and similar in 
type design to an engine that has a type certificate issued in 
accordance with 14 CFR part 33, 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 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 applicant 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\3\ if the characteristic level of 
maximum nvPMMC is below 1,000 [mu]g/m\3\.
    (B) 20% of the characteristic level if the 
characteristic level for maximum nvPMMC is at or above 1,000 
[mu]g/m\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\14\ particles/kN if the characteristic level for 
nvPMnum emissions is below 2 x 10\15\ particles/kN.
    (B) 20% of the characteristic level if the 
characteristic level for nvPMnum emissions is greater than 
or equal to 2x10\15\ particles/kN.
    (2) In unusual circumstances, the FAA may, for individual 
certification applications, adjust the ranges beyond those specified in 
paragraph (c)(1) of this section to evaluate a proposed derivative 
engine, consistent with good engineering judgment.

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-

[[Page 72355]]

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 
across the engine operating thrust range.
    (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 across the engine operating thrust 
range, 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 
percent of 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 percent of 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 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

[[Page 72356]]

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.

    This part uses the following abbreviations:

                Table 1 to Sec.   1031.200--Abbreviations
------------------------------------------------------------------------
 
------------------------------------------------------------------------
[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
[micro]g...............................  Microgram
NOX....................................  oxides of nitrogen
Num....................................  Number
nvPM...................................  non-volatile particulate matter
nvPMmass...............................  non-volatile particulate matter
                                          mass
nvPMnum................................  non-volatile particulate matter
                                          number
nvPMMC.................................  non-volatile particulate matter
                                          mass concentration
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 chapter I 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 is derived from and similar in type design to an engine 
that has a type certificate issued in accordance with 14 CFR part 33, 
and complies with the requirements of 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

[[Page 72357]]

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.  1031.20 
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.  1031.20.
    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 chapter I 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 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.

    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 EPA 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 EPA and at the 
National Archives and Records Administration (NARA). Contact EPA 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. For information on the availability of this 
material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from International Civil Aviation Organization, Document Sales 
Unit, 999 University Street, Montreal, Quebec, Canada H3C 5H7; (514) 
954-8022; [email protected]; www.icao.int.
    (a) Annex 16 to the Convention on International Civil Aviation, 
Environmental Protection, Volume II--Aircraft Engine Emissions, Fourth 
Edition, July 2017 (including Amendment No. 10, applicable January 1, 
2021); IBR approved for Sec. Sec.  1031.140; 1031.205.
    (b) [Reserved]

[FR Doc. 2022-25134 Filed 11-22-22; 8:45 am]
BILLING CODE 6560-50-P