6324 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 87, 1030, and 1031 

[EPA–HQ–OAR–2019–0660; FRL–7558–01– 

OAR] 

RIN 2060–AU69 

Control of Air Pollution From Aircraft 

Engines: Emission Standards and Test 

Procedures 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing particulate 

matter (PM) emission standards and test 

procedures applicable to certain classes 

of engines used by civil subsonic jet 

airplanes (those engines with rated 

output of greater than 26.7 kilonewtons 

(kN)) to replace the existing smoke 

standard for aircraft. These proposed 

standards and test procedures are 

equivalent to the engine standards 

adopted by the United Nations’ 

International Civil Aviation 

Organization (ICAO) in 2017 and 2020 

and would apply to both new type 

design aircraft engines and inproduction aircraft engines. The EPA, as 

well as the United States Federal 

Aviation Administration (FAA), actively 

participated in the ICAO proceedings in 

which these requirements were 

developed. These proposed standards 

would reflect the importance of the 

control of PM emissions and U.S. efforts 

to secure the highest practicable degree 

of uniformity in aviation regulations 

and standards. Additionally, the EPA is 

proposing to migrate, modernize, and 

streamline the existing regulations into 

a new part. As part of this update, the 

EPA is also proposing to align with 

ICAO by applying the smoke number 

standards to engines less than or equal 

to 26.7 kilonewtons rated output used in 

supersonic airplanes. 

DATES: Comments on this proposal must 

be received on or before April 4, 2022. 

Public hearing: EPA will announce 

the public hearing date and location for 

this proposal in a supplemental Federal 

Register document. 

ADDRESSES: 

Comments: EPA solicits comments on 

all aspects of the proposed standards. 

Written comments: Submit your 

comments, identified by Docket ID No. 

EPA–HQ–OAR–2019–0660, at https://

www.regulations.gov. Follow the online 

instructions for submitting comments. 

Once submitted, comments cannot be 

edited or removed from Regulations.gov. 

The EPA may publish any comment 

received to its public docket. Do not 

submit electronically any information 

you consider to be Confidential 

Business Information (CBI) or other 

information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). For 

additional submission methods, the full 

EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. 

The EPA is temporarily suspending 

its Docket Center and Reading Room for 

public visitors, with limited exceptions, 

to reduce the risk of transmitting 

COVID–19. Our Docket Center staff will 

continue to provide remote customer 

service via email, phone, and webform. 

We encourage the public to submit 

comments via https://

www.regulations.gov as there may be a 

delay in processing mail and faxes. For 

further information and updates on EPA 

Docket Center services, please visit us 

online at https://www.epa.gov/dockets. 

The EPA continues to carefully and 

continuously monitor information from 

the Centers for Disease Control and 

Prevention (CDC), local area health 

departments, and our Federal partners 

so that we can respond rapidly as 

conditions change regarding COVID–19. 

Docket: EPA has established a docket 

for the action under Docket ID No. EPA– 

HQ–OAR–2019–0660. All documents in 

the docket are listed on the 

www.regulations.gov website. Although 

listed in the index, some information is 

not publicly available, e.g., confidential 

business information or other 

information whose disclosure is 

restricted by statute. Certain other 

material, such as copyrighted material is 

not placed on the internet and will be 

publicly available only in hard copy 

form. Publicly available docket 

materials are available either 

electronically through 

www.regulations.gov or in hard copy at 

the following location: 

Air and Radiation Docket and 

Information Center, EPA Docket Center, 

EPA/DC, EPA WJC West Building, 1301 

Constitution Ave. NW, Room 3334, 

Washington, DC. 

Out of an abundance of caution for 

members of the public and our staff, the 

EPA Docket Center and Reading Room 

was closed to public visitors on March 

31, 2020, to reduce the risk of 

transmitting COVID–19. Our Docket 

Center staff will continue to provide 

remote customer service via email, 

phone, and webform. We encourage the 

public to submit comments via https:// 

www.regulations.gov or email, as there 

is a temporary suspension of mail 

delivery to EPA, and no hand deliveries 

are currently accepted. For further 

information on EPA Docket Center 

services and the current status, please 

visit us online at https://www.epa.gov/ 

dockets. 

FOR FURTHER INFORMATION CONTACT: 

Bryan Manning, Office of 

Transportation and Air Quality, 

Assessment and Standards Division 

(ASD), Environmental Protection 

Agency, 2000 Traverwood Drive, Ann 

Arbor, MI 48105; telephone number: 

(734) 214–4832; email address: 

manning.bryan@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. General Information 

A. Does this action apply to me? 

B. Executive Summary 

1. Summary of the Major Provisions of the 

Proposed Regulatory Action 

2. Purpose of the Proposed Regulatory 

Action 

3. Environmental Justice 

II. Introduction: Context for This Proposed 

Action 

A. EPA Statutory Authority and 

Responsibilities Under the Clean Air Act 

B. The Role of the United States in 

International Aircraft Agreements 

C. The Relationship Between EPA’s 

Regulation of Aircraft Engine Emissions 

and International Standards 

III. Particulate Matter Impacts on Air Quality 

and Health 

A. Background on Particulate Matter 

B. Health Effects of Particulate Matter 

C. Environmental Effects of Particulate 

Matter 

1. Deposition of Metallic and Organic 

Constituents of PM 

2. Materials Damage and Soiling 

D. Near-Source Impacts on Air Quality and 

Public Health 

E. Contribution of Aircraft Emissions to PM 

in Selected Areas 

F. Other Pollutants Emitted by Aircraft 

G. Environmental Justice 

IV. Details for the Proposed Rule 

A. PM Mass Standards for Aircraft Engines 

1. Applicability of Standards 

2. New Type nvPM Mass Numerical 

Emission Limits for Aircraft Engines 

3. In Production nvPM Mass Numerical 

Emission Limits for Aircraft Engines 

4. Graphical representation of nvPM Mass 

Numerical Emission Limits 

B. PM Number Standards for Aircraft 

Engines 

1. Applicability of Standards 


khammond on DSKJM1Z7X2PROD with PROPOSALS3
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6325 

1The implementation date for ICAO’s PM 

maximum mass concentration standards is on or 

after January 1, 2020. The final rulemaking that 

would follow this proposed rulemaking for these 

standards is expected to be completed before 

January 1, 2023. Thus, the standards would have an 

implementation date of January 1, 2023 (instead of 

January 1, 2020). 

2. New Type nvPM Number Numerical 

Emission Limits for Aircraft Engines 

3. In Production nvPM Number Numerical 

Emission Limits for Aircraft Engines 

4. Graphical representation of nvPM 

Number Numerical Emission Limits 

C. PM Mass Concentration Standard for 

Aircraft Engines 

1. PM Mass Concentration Standard 

2. Graphical Representation of nvPM Mass 

Concentration Numerical Emission Limit 

D. Test and Measurement Procedures 

1. Aircraft Engine PM Emissions Metrics 

2. Test Procedure 

3. Test Duty Cycles 

4. Characteristic Level 

5. Derivative Engines for Emissions 

Certification Purposes 

E. Annual Reporting Requirement 

V. Aggregate PM Inventory Impacts 

A. Aircraft Engine PM Emissions for 

Modeling 

1. Baseline PM Emission Indices 

2. Measured nvPM EIs for Inventory 

Modeling 

3. Improvements to Calculated EIs 

B. Baseline PM Emission Inventory 

C. Projected Reductions in PM Emissions 

VI. Technological Feasibility and Economic 

Impacts 

A. Market Considerations 

B. Conceptual Framework for Technology 

C. Technological Feasibility 

D. Costs Associated With the Proposed 

Rule 

E. Summary of Benefits and Costs 

VII. Technical Amendments 

A. Migration of Regulatory Text to New 

Part 

B. Deletion of Unnecessary Provisions 

C. Other Technical Amendments and 

Minor Changes 

VIII. Statutory Authority and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

B. Paperwork Reduction Act (PRA) 

C. Regulatory Flexibility Act (RFA) 

D. Unfunded Mandates Reform Act 

(UMRA) 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution or Use 

I. National Technology Transfer and 

Advancement Act (NTTAA) 

J. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

I. General Information 

A. Does this action apply to me? 

This proposed action would affect 

companies that design and or 

manufacture civil subsonic jet aircraft 

engines with a rated output of greater 

than 26.7 kN and those that design and 

or manufacturer civil jet engines for use 

on supersonic airplanes with a rated 

output at or below 26.7 kN. These 

affected entities include the following: 

Category NAICS code a Examples of potentially affected entities 

Industry ..................................................... 336412 Manufacturers of new aircraft engines. 

a North American Industry Classification System (NAICS). 

This table lists the types of entities 

that EPA is now aware could potentially 

be affected by this action. Other types of 

entities not listed in the table could also 

be regulated. To determine whether 

your activities are regulated by this 

action, you should carefully examine 

the relevant applicability criteria in 40 

CFR parts 87 and 1031. If you have any 

questions regarding the applicability of 

this action to a particular entity, consult 

the person listed in the preceding FOR

FURTHER INFORMATION CONTACT section. 

For consistency purposes across the 

United States Code of Federal 

Regulations (CFR), common definitions 

for the words ‘‘airplane,’’ ‘‘aircraft,’’ 

‘‘aircraft engine,’’ and ‘‘civil aircraft’’ are 

found in Title 14 CFR part 1, and are 

used as appropriate throughout this new 

proposed regulation under 40 CFR parts 

87 and 1031. 

B. Executive Summary 

1. Summary of the Major Provisions of 

the Proposed Regulatory Action 

The EPA is proposing to regulate PM 

emissions from covered aircraft engines 

through the adoption of domestic PM 

regulations that match the ICAO PM 

standards, which would be 

implemented and enforced in the U.S. 

The proposed standards would apply to 

new type design and in-production 

aircraft engines with rated output 

(maximum thrust available for takeoff) 

of greater than 26.7 kN used by civil 

subsonic jet airplanes: Those engines 

generally used in commercial passenger 

and freight aircraft, as well as larger 

business jets. The EPA is proposing to 

adopt three different forms of PM 

standards: A PM mass standard in 

milligrams per kilonewton (mg/kN), a 

PM number standard in number of 

particles per kilonewton (#/kN), and a 

PM mass concentration standard in 

micrograms per cubic meter (mg/m3). 

The applicable dates and coverage of 

these standards would vary, as 

described in the following paragraphs, 

and more fully in in IV.A, IV.B, and 

IV.C respectively. 

First, the EPA is proposing PM engine 

emissions standards, in the form of both 

PM mass (mg/kN) and PM number (#/ 

kN), for new type designs and inproduction aircraft turbofan and turbojet 

engines with rated output greater than 

26.7 kN. The proposed standards for inproduction engines would apply to 

those engines that would be 

manufactured on or after January 1, 

2023, even if type certificated before 

that date. The proposed standards for 

new type designs would apply to those 

engines whose initial type certification 

application was submitted on or after 

January 1, 2023. The in-production 

standards would have different 

emission levels limits than would the 

standards for new type designs. The 

different emission levels limits for new 

type designs and in-production engines 

would depend on the rated output of the 

engines. Compliance with the proposed 

PM mass and number standards would 

be done in accordance with the standard 

landing and take-off (LTO) test cycle, 

which is currently used for 

demonstrating compliance with gaseous 

emission standards (oxides of nitrogen 

(NOX), hydrocarbons (HC), and carbon 

monoxide (CO) standards) for the 

covered engines. 

Second, the EPA is proposing a PM 

engine emissions standard in the form 

of maximum mass concentration (mg/ 

m3) for in-production aircraft turbofan 

and turbojet engines with rated output 

greater than 26.7 kN manufactured on or 

after January 1, 2023.1 Compliance with 

the PM mass concentration standard 

would be done using the same test data 

that is developed to demonstrate 

compliance with the LTO-based PM 

mass and number standards. The 

proposed PM mass concentration 

standard would apply to the highest 

concentration of PM measured across 

the engine operating thrust range, not 


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6326 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

2 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017. Available at 

https://www.icao.int/publications/catalogue/cat_

2021_en.pdf (last accessed November 15, 2021). The 

ICAO Annex 16 Volume II is found on page 17 of 

the ICAO Products & Services Catalog, English 

Edition of the 2021 catalog, and it is copyright 

protected; Order No. AN16–2. The ICAO Annex 16, 

Volume II, Fourth Edition, includes Amendment 10 

of January 1, 2021. Amendment 10 is also found on 

page 17 of this ICAO catalog, and it is copyright 

protected; Order No. AN 16–2/E/12. 

just at one of the four LTO thrust 

settings. 

The proposed PM mass concentration 

standard was developed by ICAO to 

provide, through a PM mass 

measurement, the equivalent smoke 

opacity or visibility control as afforded 

by the existing smoke number standard 

for the covered engines. Thus, the EPA 

is also proposing to no longer apply the 

existing smoke number standard for 

new engines that would be subject to 

the proposed PM mass concentration 

standard after January 1, 2023, but the 

EPA is maintaining smoke number 

standards for new engines not covered 

by the PM mass concentration standard 

(e.g., in-production aircraft turbofan and 

turbojet engines with rated output less 

than or equal to 26.7 kN) and for 

engines already manufactured. This 

proposed approach would essentially 

change the existing standard for covered 

engines from being based on a smoke 

measurement to a PM measurement. 

Third, the EPA is proposing testing 

and measurement procedures for the PM 

emission standards and various updates 

to the existing gaseous exhaust 

emissions test procedures. These 

proposed test procedure provisions 

would implement the recent additions 

and amendments to ICAO’s regulations, 

which are codified in ICAO Annex 16, 

Volume II. As we have historically 

done, we propose to incorporate these 

test procedure additions and 

amendments to the ICAO Annex 16, 

Volume II into our regulations by 

reference. 

The proposed aircraft engine PM 

standards, test procedures and 

associated regulatory requirements are 

equivalent to the international PM 

standards and test procedures adopted 

by ICAO in 2017 and 2020 and 

promulgated in Annex 16, Volume II.2

The United States and other member 

States of ICAO, as well as the world’s 

aircraft engine manufacturers and other 

interested stakeholders, participated in 

the deliberations leading up to ICAO’s 

adoption of the international aircraft 

engine PM emission standards. 

In addition to the PM standards just 

discussed, the EPA is proposing to 

migrate the existing aircraft engine 

emissions regulations from 40 CFR part 

87 to a new 40 CFR part 1031, and all 

the aircraft engine standards and 

requirements described earlier would be 

specified in this new part 1031. Along 

with this migration, the EPA is 

proposing to restructure the regulations 

to allow for better ease of use and allow 

for more efficient future updates. The 

EPA is also proposing to delete some 

unnecessary definitions and regulatory 

provisions. Finally, the EPA is 

proposing several other minor technical 

amendments to the regulations, 

including applying smoke number 

standards to engines of less than or 

equal to 26.7 kilonewtons (kN) rated 

output used in supersonic airplanes. 

2. Purpose of the Proposed Regulatory 

Action 

In developing these proposed 

standards, the EPA took into 

consideration the importance of both 

controlling PM emissions and 

international harmonization of aviation 

requirements. In addition, the EPA gave 

significant weight to the U.S.’s treaty 

obligations under the Chicago 

Convention, as discussed in Section 

II.B, in determining the need for and 

appropriate levels of PM standards. 

These considerations led the EPA to 

propose standards for PM emissions 

from certain classes of covered aircraft 

engines that are equivalent in scope, 

stringency, and effective date to the PM 

standards adopted by ICAO. 

The new ICAO aircraft PM emission 

standards will take effect on January 1, 

2023 but will not apply in the U.S. 

unless adopted into domestic law. One 

of the core functions of ICAO is to adopt 

Standards and Recommended Practices 

on a wide range of aviation-related 

matters, including aircraft emissions. As 

a member State of ICAO, the United 

States actively participates in the 

development of new environmental 

standards, within ICAO’s Committee on 

Aviation Environmental Protection 

(CAEP), including the PM standards 

adopted by ICAO in both 2017 and 

2020. Due to the international nature of 

the aviation industry, there is an 

advantage to working within ICAO, in 

order to secure the highest practicable 

degree of uniformity in international 

aviation regulations and standards. 

Uniformity in international aviation 

regulations and standards is a goal of 

the Chicago Convention, because it 

ensures that passengers and the public 

can expect similar levels of protection 

for safety and human health and the 

environment regardless of manufacturer, 

airline, or point of origin of a flight. 

Further, it helps reduce barriers in the 

global aviation market, benefiting both 

U.S. aircraft engine manufacturers and 

consumers. 

When developing new emissions 

standards, ICAO/CAEP seeks to capture 

the technological advances made in the 

control of emissions through the 

adoption of anti-backsliding standards 

reflecting the current state of 

technology. The PM standards the EPA 

is proposing were developed using this 

approach. Thus, the adoption of these 

aviation standards into U.S. law would 

simultaneously prevent aircraft engine 

PM levels from increasing beyond their 

current levels, align U.S. domestic 

standards with the ICAO standards for 

international harmonization, and help 

the U.S. meet its treaty obligations 

under the Chicago Convention. 

These proposed standards would also 

allow U.S. manufacturers of covered 

aircraft engines to remain competitive in 

the global marketplace (as described 

later in the introductory text of Section 

IV). In the absence of U.S. standards 

implementing the ICAO aircraft engine 

PM emission standards, U.S. civil 

aircraft engine manufacturers could be 

forced to seek PM emissions 

certification from an aviation 

certification authority of another 

country (not the FAA) in order to 

market and operate their aircraft engines 

internationally. U.S. manufacturers 

could be at a significant disadvantage if 

the U.S. fails to adopt standards that are 

at least as stringent as the ICAO 

standards for PM emissions. The ICAO 

aircraft engine PM emission standards 

have been or are being adopted by other 

ICAO member states that certify aircraft 

engines. The proposed action to adopt 

in the U.S. PM standards that match the 

ICAO standards would help ensure 

international consistency and 

acceptance of U.S. manufactured 

engines worldwide. 

3. Environmental Justice 

Executive Orders 12898 (59 FR 7629, 

February 16, 1994) and 14008 (86 FR 

7619, February 1, 2021) direct federal 

agencies, to the greatest extent 

practicable and permitted by law, to 

make achieving environmental justice 

(EJ) part of their mission by identifying 

and addressing, as appropriate, 

disproportionately high and adverse 

human health or environmental effects 

of their programs, policies, and 

activities on minority populations and 

low-income populations in the United 

States. Section III.G discusses these 

executive orders in greater detail, along 

with the potential environmental justice 

concerns associated with exposure to 

aircraft PM near airports. EPA defines 

environmental justice as the fair 


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Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6327 

3The U.S. Court of Appeals for the D.C. Circuit 

has held that CAA section 231 confers an 

‘‘extraordinarily broad’’ degree of discretion on EPA 

to ‘‘weigh various factors’’ and adopt aircraft engine 

emission standards as the Agency determines are 

reasonable. Nat’l Ass’n of Clean Air Agencies v. 

EPA, 489 F.3d 1221, 1229–30 (D.C. Cir. 2007) 

(NACAA). 

4See 70 FR 69664, 69676 (November 17, 2005). 

5 ICAO, 2006: Convention on International Civil 

Aviation, Ninth Edition, Document 7300/9. 

Available at: https://www.icao.int/publications/ 

Documents/7300_9ed.pdf (last accessed July 20, 

2021). 

6Members of ICAO’s Assembly are generally 

termed member States or contracting States. These 

terms are used interchangeably throughout this 

preamble. 

7There are currently 193 contracting states 

according to ICAO’s website: https://www.icao.int/ 

MemberStates/Member%20States.English.pdf (last 

accessed July 12, 2021). 

treatment and meaningful involvement 

of all people regardless of race, color, 

national origin, or income with respect 

to the development, implementation, 

and enforcement of environmental laws, 

regulations, and policies. 

Studies have reported that many 

communities in close proximity to 

airports are disproportionately 

represented by people of color and lowincome populations (as described later 

in Section III.G). In an action separate 

from this proposed rulemaking, EPA 

will be conducting an analysis of the 

communities residing near airports 

where jet aircraft operate in order to 

more fully understand 

disproportionately high and adverse 

human health or environmental effects 

on people of color, low-income 

populations and/or indigenous peoples. 

The results of this analysis could help 

inform additional policies to reduce 

pollution in communities living in close 

proximity to airports. 

As described in Section V.C, while 

newer aircraft engines typically have 

significantly lower emissions than 

existing aircraft engines, the proposed 

standards in this action are technologyfollowing in order to align with ICAO’s 

standards and are not expected to, in 

and of themselves, result in further 

reductions in PM from these engines. 

Therefore, we do not anticipate an 

improvement in air quality for those 

who live near airports where these 

aircraft operate. 

II. Introduction: Context for This 

Proposed Action 

EPA has been regulating PM 

emissions from aircraft engines since 

the 1970s when the first smoke number 

standards were adopted. This section 

provides context for the proposed rule, 

which proposes three PM standards for 

aircraft engines. This section includes a 

description of EPA’s statutory authority, 

the United States’ role in ICAO and 

developing international emission 

standards, and the relationship between 

United States’ standards and ICAO’s 

international standards. 

A. EPA Statutory Authority and 

Responsibilities Under the Clean Air Act 

Section 231(a)(2)(A) of the Clean Air 

Act (CAA) directs the Administrator of 

EPA to, from time to time, propose 

aircraft engine emission standards 

applicable to the emission of any air 

pollutant from classes of aircraft engines 

which in his or her judgment causes or 

contributes to air pollution that may 

reasonably be anticipated to endanger 

public health or welfare. (See 42 U.S.C. 

7571(a)(2)(A)). CAA section 231(a)(2)(B) 

directs the EPA to consult with the 

Administrator of the Federal Aviation 

Administration (FAA) on such 

standards, and it prohibits the EPA from 

changing aircraft emission standards if 

such a change would significantly 

increase noise and adversely affect 

safety. (See 42 U.S.C. 7571(a)(2)(B)(i)– 

(ii)). CAA section 231(a)(3) provides that 

after we provide notice and an 

opportunity for a public hearing on 

standards, the Administrator shall issue 

such standards ‘‘with such 

modifications as he deems appropriate.’’ 

(See 42 U.S.C. 7571(a)(3)). In addition, 

under CAA section 231(b) the EPA is 

required to ensure, in consultation with 

the U.S. Department of Transportation 

(DOT), that the effective date of any 

standard provides the necessary time to 

permit the development and application 

of the requisite technology, giving 

appropriate consideration to the cost of 

compliance. (See 42 U.S.C. 7571(b)). 

Consistent with its longstanding 

approach and D.C. Circuit precedent,3

the EPA interprets its authority under 

CAA section 231 as providing the 

Administrator wide discretion in 

determining what standards are 

appropriate, after consideration of the 

factors specified in the statute and other 

relevant factors, such as applicable 

international standards. We are not 

compelled under CAA section 231 to 

obtain the ‘‘greatest degree of emission 

reduction achievable’’ as per sections 

213(a)(3) and 202(a)(3)(A) of the CAA, 

and so the EPA does not interpret the 

Act as requiring the agency to give 

subordinate status to factors such as 

cost, safety, and noise in determining 

what standards are reasonable for 

aircraft engines. Rather, the EPA has 

greater flexibility under section 231 in 

determining what standard is most 

reasonable for aircraft engines. Thus, as 

in past rulemakings, EPA notes its 

authority under the CAA to issue 

reasonable aircraft engine standards 

with either technology-following or 

technology-forcing results, provided 

that, in either scenario, the Agency has 

a reasonable basis after considering all 

the relevant factors for setting the 

standard.4 Once EPA adopts standards, 

CAA section 232 then directs the 

Secretary of Transportation to prescribe 

regulations to ensure compliance with 

the EPA’s standards. (See 42 U.S.C. 

7572). Finally, section 233 of the CAA 

vests the authority to promulgate 

emission standards for aircraft or 

aircraft engines only in the Federal 

Government. States are preempted from 

adopting or enforcing any standard 

respecting aircraft or aircraft engine 

emissions unless such standard is 

identical to the EPA’s standards. (See 42 

U.S.C. 7573). 

B. The Role of the United States in 

International Aircraft Agreements 

The Convention on International Civil 

Aviation (commonly known as the 

‘Chicago Convention’) was signed in 

1944 at the Diplomatic Conference held 

in Chicago. It was ratified by the United 

States on August 9, 1946. The Chicago 

Convention establishes the legal 

framework for the development of 

international civil aviation. The primary 

objective is ‘‘that international civil 

aviation may be developed in a safe and 

orderly manner and that international 

air transport services may be established 

on the basis of equality of opportunity 

and operated soundly and 

economically.’’ 5 In 1947, ICAO was 

established, and later in that same year, 

ICAO became a specialized agency of 

the United Nations (UN). ICAO sets 

international standards for aviation 

safety, security, efficiency, capacity, and 

environmental protection and serves as 

the forum for cooperation in all fields of 

international civil aviation. ICAO works 

with the Chicago Convention’s member 

States and global aviation organizations 

to develop international Standards and 

Recommended Practices (SARPs), 

which member States reference when 

developing their domestic civil aviation 

regulations. The United States is one of 

193 currently participating ICAO 

member States.6 7 ICAO standards are 

not self-implementing. They must first 

be adopted into domestic law to be 

legally binding in any member State. 

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 


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6328 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

8 ICAO, 2006: Convention on International Civil 

Aviation, Article 37, Ninth Edition, Document 

7300/9. Available at https://www.icao.int/ 

publications/Documents/7300_9ed.pdf (last 

accessed July 20, 2021). 

9 ICAO, 2006: Doc 7300-Convention on 

International Civil Aviation, Ninth Edition, 

Document 7300/9. Available at https://

www.icao.int/publications/Documents/7300_

9ed.pdf (last accessed July 20, 2021). 

10 ICAO, 2006: Convention on International Civil 

Aviation, Article 33, Ninth Edition, Document 7300/ 

9. Available at https://www.icao.int/publications/ 

Documents/7300_9ed.pdf (last accessed July 20, 

2021). 

11 ICAO, 2006: Convention on International Civil 

Aviation, Article 33, Ninth Edition, Document 7300/ 

9. Available at https://www.icao.int/publications/ 

Documents/7300_9ed.pdf (last accessed July 20, 

2021). 

12 ICAO, 2006: Convention on International Civil 

Aviation, Article 38, Ninth Edition, Document 7300/ 

9. Available at https://www.icao.int/publications/ 

Documents/7300_9ed.pdf (last accessed July 20, 

2021). 

13 ICAO: CAEP Terms of Reference. Available at 

https://www.icao.int/environmental-protection/ 

Pages/Caep.aspx#ToR (last accessed July 20, 2021). 

14 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017. Available at 

https://www.icao.int/publications/catalogue/cat_

2021_en.pdf (last accessed November 15, 2021). The 

ICAO Annex 16 Volume II is found on page 17 of 

the ICAO Products & Services English Edition of the 

2021 catalog, and it is copyright protected; Order 

No. AN16–2. The ICAO Annex 16, Volume II, 

Fourth Edition, includes Amendment 10 of January 

1, 2021. Amendment 10 is also found on page 17 

of this ICAO catalog, and it is copyright protected; 

Order No. AN 16–2/E/12. 

15CAEP develops new emission standards based 

on an assessment of the technical feasibility, cost, 

and environmental benefit of potential 

requirements. 

16 ICAO, 2017: Aircraft Engine Emissions: 

Foreword, International Standards and 

Recommended Practices, Environmental Protection, 

Annex 16, Volume II, Fourth Edition, July 2017. 

Available at https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). The ICAO Annex 16 Volume II is found 

on page 17 of the ICAO Products & Services English 

Edition 2021 catalog and is copyright protected; 

Order No. AN16–2. The ICAO Annex 16, Volume 

II, Fourth Edition, includes Amendment 10 of 

January 1, 2021. Amendment 10 is also found on 

page 17 of this ICAO catalog, and it is copyright 

protected; Order No. AN 16–2/E/12. 

17CAEP 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. 

air navigation.’’ 8 The Chicago 

Convention also recognizes that member 

States may adopt national standards that 

are more or less stringent than those 

agreed upon by ICAO or standards that 

are different in character or that comply 

with the ICAO standards by other 

means. Any member State that finds it 

impracticable to comply in all respects 

with any international standard or 

procedure, or that determines it is 

necessary to adopt regulations or 

practices differing in any particular 

respect from those established by an 

international standard, is required to 

give notification to ICAO of the 

differences between its own practice 

and that established by the international 

standard.9

ICAO’s work on the environment 

focuses primarily on those problems 

that benefit most from a common and 

coordinated approach on a worldwide 

basis, namely aircraft noise and engine 

emissions. SARPs for the certification of 

aircraft noise and aircraft engine 

emissions are covered by Annex 16 of 

the Chicago Convention. To continue to 

address aviation environmental issues, 

in 2004, ICAO established three 

environmental goals: (1) Limit or reduce 

the number of people affected by 

significant aircraft noise; (2) limit or 

reduce the impact of aviation emissions 

on local air quality; and (3) limit or 

reduce the impact of aviation 

greenhouse gas (GHG) emissions on the 

global climate. 

The Chicago Convention has a 

number of other features that govern 

international commerce. First, member 

States that wish to use aircraft in 

international transportation must adopt 

emission standards that are at least as 

stringent as ICAO’s standards if they 

want to ensure recognition of their 

airworthiness certificates by other 

member States. Member States may ban 

the use of any aircraft within their 

airspace that does not meet ICAO 

standards.10 Second, the Chicago 

Convention indicates that member 

States are required to recognize the 

airworthiness certificates issued or 

rendered valid by the contracting State 

in which the aircraft is registered 

provided the requirements under which 

the certificates were issued are equal to 

or above ICAO’s minimum standards.11

Third, to ensure that international 

commerce is not unreasonably 

constrained, a member State that cannot 

meet or deems it necessary to adopt 

regulations differing from the 

international standard is obligated to 

notify ICAO of the differences between 

its domestic regulations and ICAO 

standards.12

ICAO’s Committee on Aviation 

Environmental Protection (CAEP), 

which consists of members and 

observers from States, 

intergovernmental and nongovernmental organizations 

representing the aviation industry and 

environmental interests, undertakes 

ICAO’s technical work in the 

environmental field. The Committee is 

responsible for evaluating, researching, 

and recommending measures to the 

ICAO Council that address the 

environmental impacts of international 

civil aviation. CAEP’s terms of reference 

indicate that ‘‘CAEP’s assessments and 

proposals are pursued taking into 

account: Technical feasibility; 

environmental benefit; economic 

reasonableness; interdependencies of 

measures (for example, among others, 

measures taken to minimize noise and 

emissions); developments in other 

fields; and international and national 

programs.’’ 13 The ICAO Council 

reviews and adopts the 

recommendations made by CAEP. It 

then reports to the ICAO Assembly, the 

highest body of the organization, where 

the main policies on aviation 

environmental protection are adopted 

and translated into Assembly 

Resolutions. If ICAO adopts a CAEP 

proposal for a new environmental 

standard, it then becomes part of ICAO 

standards and recommended practices 

(Annex 16 to the Chicago 

Convention).14 15

The FAA plays an active role in 

ICAO/CAEP, including serving as the 

representative (member) of the United 

States at annual ICAO/CAEP Steering 

Group meetings, as well as the ICAO/ 

CAEP triennial meetings, and 

contributing technical expertise to 

CAEP’s working groups. The EPA serves 

as an advisor to the U.S. member at the 

annual ICAO/CAEP Steering Group and 

triennial ICAO/CAEP meetings, while 

also contributing technical expertise to 

CAEP’s working groups and assisting 

and advising the FAA on aviation 

emissions, technology, and 

environmental policy matters. In turn, 

the FAA assists and advises the EPA on 

aviation environmental issues, 

technology, and airworthiness 

certification matters. 

CAEP’s predecessor at ICAO, the 

Committee on Aircraft Engine Emissions 

(CAEE), adopted the first international 

SARPs for aircraft engine emissions 

which were proposed in 1981.16 These 

standards limited aircraft engine 

emissions of hydrocarbons (HC), carbon 

monoxide (CO), and oxides of nitrogen 

(NOX). The 1981 standards applied to 

newly manufactured engines, which are 

those engines manufactured after the 

effective date of the regulations—also 

referred to as in-production engines. In 

1993, ICAO adopted a CAEP/2 proposal 

to tighten the original NOX standard by 

20 percent and amend the test 

procedures.17 These 1993 standards 

applied both to newly certificated 

turbofan engines (those engine models 

that received their initial type certificate 

after the effective date of the 


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18CAEP/5 did not address new aircraft engine 

emission standards. 

19 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017. Available at 

https://www.icao.int/publications/catalogue/cat_

2021_en.pdf (last accessed June 16, 2021). The 

ICAO Annex 16 Volume II is found on page 17 of 

the ICAO Products & Services Catalog, English 

Edition of the 2021 catalog, and it is copyright 

protected; Order No. AN16–2. The ICAO Annex 16, 

Volume II, Fourth Edition, includes Amendment 10 

of January 1, 2021. Amendment 10 is also found on 

page 17 of this ICAO catalog, and it is copyright 

protected; Order No. AN 16–2/E/12. 

20CAEP/7 did not address new aircraft engine 

emission standards. 

21 ICAO, 2010: Committee on Aviation 

Environmental Protection (CAEP), Report of the 

Eighth Meeting, Montreal, February 1–12, 2010, 

CAEP/8–WP/80 Available in Docket EPA–HQ– 

OAR–2010–0687. 

22 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017, Amendment 

10. CAEP/8 corresponds to Amendment 7 effective 

on July 18, 2011. Available at https://www.icao.int/ 

publications/catalogue/cat_2021_en.pdf (last 

accessed November 15, 2021). The ICAO Annex 16 

Volume II is found on page 17 of the ICAO Products 

& Services Catalog, English Edition of the 2021 

catalog, and it is copyright protected; Order No. 

AN16–2. The ICAO Annex 16, Volume II, Fourth 

Edition, includes Amendment 10 of January 1, 

2021. Amendment 10 is also found on page 17 of 

this ICAO catalog, and it is copyright protected; 

Order No. AN 16–2/E/12. 

23More specifically, the international PM 

standard applies to all turbofan and turbojet engines 

of a type or model, and their derivative versions, 

with a rated output greater than 26.7 kN and whose 

date of manufacture of the individual engine is on 

or after January 1, 2020 (or those engines 

manufactured on or after January 1, 2020). 

24U.S. EPA, 1973: Emission Standards and Test 

Procedures for Aircraft; Final Rule, 38 FR 19088 

(July 17, 1973). 

25The following are the most recent EPA 

rulemakings that revised these regulations. U.S. 

EPA, 1997: Control of Air Pollution from Aircraft 

and Aircraft Engines; Emission Standards and Test 

Procedures; Final Rule, 62 FR 25355 (May 8, 1997). 

U.S. EPA, 2005: Control of Air Pollution from 

Aircraft and Aircraft Engines; Emission Standards 

and Test Procedures; Final Rule, 70 FR 69664 

(November 17, 2005). U.S. EPA, 2012: Control of 

Air Pollution from Aircraft and Aircraft Engines; 

Emission Standards and Test Procedures; Final 

Rule, 77 FR 36342 (June 18, 2012). U.S. EPA, 2021: 

Control of Air Pollution From Airplanes and 

Airplane Engines: GHG Emission Standards and 

Test Procedures; Final Rule, 86 FR 2136 (January 

11, 2021). 

26 ICAO: CAEP Terms of Reference. Available at 

https://www.icao.int/environmental-protection/ 

Pages/Caep.aspx#ToR (last accessed July 20, 2021). 

27 ICAO, 2019: Report of the Eleventh Meeting, 

Montreal, 4–15 February 2019, Committee on 

Aviation Environmental Protection, Document 

10126, CAEP11. It is found on page 26 of the 

English Edition of the ICAO Products & Services 

2021 Catalog and is copyright protected: Order No. 

10126. For purchase and available at: https://

www.icao.int/publications/catalogue/cat_2021_

en.pdf (last accessed June 21, 2021). The statement 

on technological feasibility is located in Appendix 

C of Agenda Item 3 of this report (see page 3C–4, 

paragraph 2.2). 

28U.S. EPA, 40 CFR 87.1. ‘‘Smoke means the 

matter in exhaust emissions that obscures the 

transmission of light, as measured by the test 

procedures specified in subpart G of this part.’’ 

‘‘Smoke number means a dimensionless value 

quantifying smoke emission as calculated according 

to ICAO Annex 16.’’ 

29U.S. EPA, Control of Air Pollution From 

Aircraft and Aircraft Engines; Emission Standards 

and Test Procedures, Final Rule, 47 FR 58462, 

December 30, 1982. 

30U.S. EPA, Control of Air Pollution From 

Aircraft and Aircraft Engines; Smoke Emission 

Standard, Final Rule, 49 FR 31873, August 9, 1984 

(bifurcating EPA’s smoke standard for new engines 

into two regimes—one for engines with rated output 

less than 26.7 kilonewtons and one for engines with 

rated output equal to or greater than 26.7 

kilonewtons). 

regulations, also referred to as new type 

design engines) and to in-production 

engines; the standards had different 

effective dates for newly certificated 

engines and in-production engines. In 

1995, CAEP/3 recommended a further 

tightening of the NOX standards by 16 

percent and additional test procedure 

amendments, but in 1997 the ICAO 

Council rejected this stringency 

proposal and approved only the test 

procedure amendments. At the CAEP/4 

meeting in 1998, the Committee adopted 

a similar 16 percent NOX reduction 

proposal, which ICAO approved in 

1998. Unlike the CAEP/2 standards, the 

CAEP/4 standards applied only to new 

type design engines after December 31, 

2003, and not to in-production engines, 

leaving the CAEP/2 standards 

applicable to in-production engines. In 

2004, CAEP/6 recommended a 12 

percent NOX reduction, which ICAO 

approved in 2005.18 19 The CAEP/6 

standards applied to new engine designs 

certificated after December 31, 2007, 

again leaving the CAEP/2 standards in 

place for in-production engines before 

January 1, 2013. In 2010, CAEP/8 

recommended a further tightening of the 

NOX standards by 15 percent for new 

engine designs certificated after 

December 31, 2013.20 21 The Committee 

also recommended that the CAEP/6 

standards be applied to in-production 

engines on or after January 1, 2013, 

which cut off the production of CAEP/ 

2 and CAEP/4 compliant engines with 

the exception of spare engines; ICAO 

adopted these as standards in 2011.22

At the CAEP/10 meeting in 2016, the 

Committee agreed to the first airplane 

CO2 emission standards, which ICAO 

approved in 2017. The CAEP/10 CO2

standards apply to new type design 

airplanes for which the application for 

a type certificate will be submitted on 

or after January 1, 2020, some modified 

in-production airplanes on or after 

January 1, 2023, and all applicable inproduction 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 inproduction engines on or after January 

1, 2020, and the CAEP/11 PM standards 

apply to new-type and in-production 

engines on or after January 1, 2023. In 

addition to CAEP/10 agreeing to a 

maximum PM mass concentration 

standard, CAEP/10 adopted a reporting 

requirement where aircraft engine 

manufacturers were required to provide 

PM mass concentration, PM mass, and 

PM number emissions data—and other 

related parameters—by January 1, 2020 

for in-production engines.23

C. The Relationship Between EPA’s 

Regulation of Aircraft Engine Emissions 

and International Standards 

Domestically, as required by the CAA, 

the EPA has been engaged in reducing 

harmful air pollution from aircraft 

engines for over 40 years, regulating 

gaseous exhaust emissions, smoke, and 

fuel venting from engines.24 We have 

periodically revised these regulations.25

The EPA’s actions to regulate certain 

pollutants emitted from aircraft engines 

come directly from the authority in 

section 231 of the CAA, and we have 

aligned the U.S. emissions requirements 

with those promulgated by ICAO. As 

described above in Section II.B, the 

ICAO/CAEP terms of reference includes 

technical feasibility.26 Technical 

feasibility has been interpreted by CAEP 

as technology demonstrated to be safe 

and airworthy and available for 

application over a sufficient range of 

newly certificated aircraft.27 This 

interpretation resulted in all previous 

ICAO emission standards, and the EPA’s 

standards reflecting them, being antibacksliding standards (i.e., the 

standards would not reduce aircraft PM 

emissions below current levels of engine 

emissions), which are technology 

following. 

For many years the EPA has regulated 

aircraft engine PM emissions through 

the use of smoke number standards.28

Since setting the original smoke number 

standards in 1973, the EPA has 

periodically revised these standards. 

The EPA amended its smoke standards 

to align with ICAO’s smoke standards in 

1982 29 and again in 1984.30

Additionally, EPA has amended the test 

procedures for measuring smoke 


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31U.S. EPA, Control of Air Pollution From 

Aircraft and Aircraft Engines; Emission Standards 

and Test Procedures, Final Rule, 62 FR 25356, May 

8, 1997 (harmonizing EPA procedures with recent 

amendments to ICAO test procedures); U.S. EPA, 

Control of Air Pollution From Aircraft and Aircraft 

Engines; Emission Standards and Test Procedures, 

Final Rule, 70 FR 69664, November 17, 2005 

(same); U.S. EPA, Control of Air Pollution From 

Aircraft and Aircraft Engines; Emission Standards 

and Test Procedures, Final Rule, 77 FR 36342, June 

18, 2012. 

32U.S. EPA, Amendment to Standards, Final 

Rule, 43 FR 12614, March 24, 1978 (setting back by 

two years the effective date for all gaseous 

emissions standards for newly manufactured 

aircraft and aircraft gas turbine engines); U.S. EPA, 

Control of Air Pollution from Aircraft and Aircraft 

Engines; Extension of Compliance Date for 

Emission Standards Applicable to JT3D Engines, 

Final Rule, 44 FR 64266, November 6, 1979 

(extending the final compliance date for smoke 

emission standards applicable to the JT3D aircraft 

engines by roughly 3.5 years); U.S. EPA, Control of 

Air Pollution from Aircraft; Amendment to 

Standards, Final Rule, 45 FR 86946, December 31, 

1980 (setting back by two years the effective date 

for all gaseous emissions standards which would 

otherwise have been effective on January 1,1981, for 

aircraft gas turbine engines); U.S. EPA, Control of 

Air Pollution from Aircraft and Aircraft Engines, 

Final Rule, 46 FR 2044, January 8, 1981 (extending 

the applicability of the temporary exemption 

provision of the standards for smoke and fuel 

venting emissions from some in-use aircraft 

engines); U.S. EPA, Control of Air Pollution From 

Aircraft and Aircraft Engines; Smoke Emission 

Standard, Final Rule, 48 FR 46481, October 12, 

1983 (staying the smoke regulations for new 

turbojet and turbofan engines rated below 26.7 kN 

thrust). 

33Also, as described in Section IV.D, the 

proposed PM standards employ a different method 

for measuring aircraft engine PM emissions 

compared to the historical smoke number emission 

standards. 

34 83 FR 44621, August 31, 2018. U.S. EPA, 

Aircraft Engines—Supplemental Information 

Related to Exhaust Emissions (Renewal), OMB 

Control Number 2060–0680, ICR Reference Number 

201809–2060–08, December 17, 2018. 

35The ICAO 2019 Environmental Report, 

Available at https://www.icao.int/environmentalprotection/Documents/ICAO-ENV-Report2019-F1- 

WEB%20(1).pdf (last accessed September 1, 2021). 

See pages 98, 100, and 101 for a description of nonvolatile 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, 

emissions 31 and modified the effective 

dates and compliance schedule for 

smoke emissions standards 

periodically.32 Now, we are proposing 

to adopt three different forms of aircraft 

engine PM standards: A PM mass 

concentration standard (mg/m3), a PM 

mass standard (mg/kN), and PM number 

standard (#/kN). These proposed aircraft 

engine PM emission standards are a 

different way of regulating and/or 

measuring 33 aircraft engine PM 

emissions in comparison to smoke 

number emission standards. 

Internationally, the EPA and the FAA 

have worked within the standard-setting 

process of ICAO (CAEP and its 

predecessor, CAEE) since the 1970’s to 

help establish international emission 

standards and related requirements, 

which individual member States adopt 

into domestic law and regulations. 

Historically, under this approach, 

international emission standards have 

first been adopted by ICAO, and 

subsequently the EPA has initiated 

rulemakings under CAA section 231 to 

establish domestic standards that are 

harmonized with ICAO’s standards. 

After EPA promulgates aircraft engine 

emission standards, CAA section 232 

requires the FAA to issue regulations to 

ensure compliance with the EPA aircraft 

engine emission standards when 

certificating aircraft pursuant to its 

authority under Title 49 of the United 

States Code. This proposed rule would 

continue this historical rulemaking 

approach. 

The EPA and FAA worked from 2009 

to 2019 within the ICAO/CAEP standard 

setting process on the development of 

the three different forms of international 

aircraft engine PM emission standards (a 

PM mass concentration standard, a PM 

mass standard, and a PM particle 

number standard). In this action, we are 

proposing to adopt PM standards 

equivalent to ICAO’s three different 

forms of aircraft engine PM emission 

standards. Adoption of the proposed 

standards would meet the United States’ 

obligations under the Chicago 

Convention and would also ensure 

global acceptance of FAA airworthiness 

certification. 

In December 2018, the EPA issued an 

information collection request (ICR) that 

matches the CAEP/10 p.m. reporting 

requirements described earlier.34 In 

addition to the PM standards, the 

proposed rulemaking would codify the 

reporting requirements implemented by 

this 2018 EPA ICR into the EPA 

regulations, as described later in Section 

IV.E. Also, in a similar time frame as 

this proposed rulemaking, EPA will be 

renewing this ICR (the ICR needs to be 

renewed triennially). 

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 (mm, or 10¥6

meter) in diameter (for reference, a 

typical strand of human hair is 70 mm 

in diameter and a grain of salt is about 

100 mm). 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 mm (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 mm), and ‘‘thoracic’’ particles 

(PM10; particles with a nominal mean 

aerodynamic diameter less than or equal 

to 10 mm). 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 mm and greater than 2.5 mm). 

Particles span many sizes and shapes 

and may consist of hundreds of different 

chemicals. Particles are emitted directly 

from sources and are also formed 

through atmospheric chemical reactions 

between PM precursors; the former are 

often referred to as ‘‘primary’’ particles, 

and the latter as ‘‘secondary’’ particles. 

Particle concentration and composition 

varies by time of year and location, and, 

in addition to differences in source 

emissions, is affected by several 

weather-related factors, such as 

temperature, clouds, humidity, and 

wind. Ambient levels of PM are also 

impacted by particles’ ability to shift 

between solid/liquid and gaseous 

phases, which is influenced by 

concentration, meteorology, and 

especially temperature. 

Fine particles are produced primarily 

by combustion processes and by 

transformations of gaseous emissions 

(e.g., sulfur oxides (SOX), nitrogen 

oxides (NOX) and volatile organic 

compounds (VOCs)) in the atmosphere. 

The chemical and physical properties of 

PM2.5 may vary greatly with time, 

region, meteorology, and source 

category. Thus, PM2.5 may include a 

complex mixture of different 

components including sulfates, nitrates, 

organic compounds, elemental carbon, 

and metal compounds. These particles 

can remain in the atmosphere for days 

to weeks and travel through the 

atmosphere hundreds to thousands of 

kilometers. 

Particulate matter is comprised of 

both volatile and non-volatile PM. PM 

emitted from the engine is known as 

non-volatile PM (nvPM), and PM 

formed from transformation of an 

engine’s gaseous emissions are defined 

as volatile PM.35 Because of the 


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gas turbine engines emit non-volatile particles of 

smaller mean diameter. Their characteristic size 

ranges roughly from 15 to 60 nanometers (nm; 1nm 

= 1/100,000 of a millimeter). These particles are 

invisible to the human eye and are ultrafine.’’ (See 

page 98.) 

‘‘Additionally, gaseous emissions from engines 

can also condense to produce new particles (i.e., 

volatile particulate matter—vPM) or coat the 

emitted soot particles. Gaseous emissions species 

react chemically with ambient chemical 

constituents in the atmosphere to produce the so 

called secondary particulate matter. Volatile 

particulate matter is dependent on these gaseous 

precursor emissions. While these precursors are 

controlled by gaseous emission certification and the 

fuel composition (e.g., sulfur content) for aircraft 

gas turbine engines, the volatile particulate matter 

is also dependent on the ambient air background 

composition.’’ (See pages 100 and 101.) 

36U.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. 

37The 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). 

38Short term exposures are usually defined as 

less than 24 hours duration. 

39Cook, R. Memorandum to Docket EPA–HQ– 

OAR–2019–0660, ‘‘Health and environmental 

effects of non-GHG pollutants emitted by turbine 

engine aircraft,’’ August 23, 2021. 

40U.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. 

41See Section 169(a) of the Clean Air Act. 

42 In the 2012 review of the PM NAAQS, the EPA 

eliminated the option for spatial averaging for the 

24-hour PM2.5 standard (78 FR 3086, January 15, 

2013). 

43https://www.epa.gov/newsreleases/epareexamine-health-standards-harmful-soot-previousadministration-left-unchanged. 

44U.S. Environmental Protection Agency (U.S. 

EPA). 2018. Integrated Science Assessment (ISA) for 

Oxides of Nitrogen, Oxides of Sulfur and Particulate 

Matter Ecological Criteria Second External Review 

Draft). EPA–600–R–18–097. Washington, DC. 

December. Available on the internet at https://

cfpub.epa.gov/ncea/isa/ 

recordisplay.cfm?deid=340671. 

difficulty in measuring volatile PM, 

which is formed in the engine’s exhaust 

plume and is significantly influenced by 

ambient conditions, the EPA is 

proposing standards only for the 

emission of nvPM. 

B. Health Effects of Particulate Matter 

Scientific studies show exposure to 

ambient PM is associated with a broad 

range of health effects. These health 

effects are discussed in detail in the 

Integrated Science Assessment for 

Particulate Matter (PM ISA), which was 

finalized in December 2019.36 The PM 

ISA concludes that human exposures to 

ambient PM2.5 are associated with a 

number of adverse health effects and 

characterizes the weight of evidence for 

broad health categories (e.g., 

cardiovascular effects, respiratory 

effects, etc.).37 The PM ISA additionally 

notes that stratified analyses (i.e., 

analyses that directly compare PMrelated health effects across groups) 

provide strong evidence for racial and 

ethnic differences in PM2.5 exposures 

and in PM2.5-related health risk. As 

described in Section III.D, 

concentrations of PM increase with 

proximity to an airport. Further, studies 

described in Section III.G report that 

many communities in close proximity to 

airports are disproportionately 

represented by people of color and lowincome populations. 

EPA has concluded that recent 

evidence in combination with evidence 

evaluated in the 2009 p.m. ISA supports 

a ‘‘causal relationship’’ between both 

long- and short-term exposures to PM2.5

and mortality and cardiovascular effects 

and a ‘‘likely to be causal relationship’’ 

between long- and short-term PM2.5

exposures and respiratory effects.38

Additionally, recent experimental and 

epidemiologic studies provide evidence 

supporting a ‘‘likely to be causal 

relationship’’ between long-term PM2.5

exposure and nervous system effects, 

and long-term PM2.5 exposure and 

cancer. In addition, EPA noted that 

there was more limited and uncertain 

evidence for long-term PM2.5 exposure 

and reproductive and developmental 

effects (i.e., male/female reproduction 

and fertility; pregnancy and birth 

outcomes), long- and short-term 

exposures and metabolic effects, and 

short-term exposure and nervous system 

effects resulting in the ISA concluding 

‘‘suggestive of, but not sufficient to 

infer, a causal relationship.’’ 

More detailed information on the 

health effects of PM can be found in a 

memorandum to the docket.39

C. Environmental Effects of Particulate 

Matter 

Environmental effects that can result 

from particulate matter emissions 

include visibility degradation, plant and 

ecosystem effects, deposition effects, 

and materials damage and soiling. These 

effects are briefly summarized here and 

discussed in more detail in the memo to 

the docket cited above. 

PM2.5 emissions also adversely impact 

visibility.40 In the Clean Air Act 

Amendments of 1977, Congress 

recognized visibility’s value to society 

by establishing a national goal to protect 

national parks and wilderness areas 

from visibility impairment caused by 

manmade pollution.41 In 1999, EPA 

finalized the regional haze program (64 

FR 35714) to protect the visibility in 

Mandatory Class I Federal areas. There 

are 156 national parks, forests and 

wilderness areas categorized as 

Mandatory Class I Federal areas (62 FR 

38680–38681, July 18, 1997). These 

areas are defined in CAA section 162 as 

those national parks exceeding 6,000 

acres, wilderness areas and memorial 

parks exceeding 5,000 acres, and all 

international parks which were in 

existence on August 7, 1977. EPA has 

also concluded that PM2.5 causes 

adverse effects on visibility in other 

areas that are not targeted by the 

Regional Haze Rule, such as urban 

areas, depending on PM2.5

concentrations and other factors such as 

dry chemical composition and relative 

humidity (i.e., an indicator of the water 

composition of the particles). EPA 

established the secondary 24-hour PM2.5

NAAQS in 1997 and has retained the 

standard in subsequent reviews.42 This 

standard is expected to provide 

protection against visibility effects 

through attainment of the existing 

secondary standards for PM2.5. EPA is 

reconsidering the 2020 decision, as 

announced on June 10, 2021.43

1. Deposition of Metallic and Organic 

Constituents of PM 

Several significant ecological effects 

are associated with deposition of 

chemical constituents of ambient PM 

such as metals and organics.44 Like all 

internal combustion engines, turbine 

engines covered by this rule may emit 

trace amounts of metals due to fuel 

contamination or engine wear. 

Ecological effects of PM include direct 

effects to metabolic processes of plant 

foliage; contribution to total metal 

loading resulting in alteration of soil 

biogeochemistry and microbiology, 

plant and animal growth and 

reproduction; and contribution to total 

organics loading resulting in 

bioaccumulation and biomagnification. 

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 


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6332 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

45U.S. Environmental Protection Agency (U.S. 

EPA). 2018. Integrated Science Assessment (ISA) for 

Oxides of Nitrogen, Oxides of Sulfur and Particulate 

Matter Ecological Criteria Second External Review 

Draft). EPA–600–R–18–097. Washington, DC. 

December. Available on the internet at https://

cfpub.epa.gov/ncea/isa/ 

recordisplay.cfm?deid=340671. 

46 Yim, S.H.L., Lee, G.L., Lee, I.H., Allrogen, F., 

Ashok, A., Caiazzo, F., Eatham, S.D., Malina, R., 

Barrett, S. R.H. 2015. Global, regional, and local 

health impacts of civil aviation emissions. Environ. 

Res. Lett. 10: 034001. https://iopscience.iop.org/ 

article/10.1088/1748-9326/10/3/034001. 

47Brunelle-Yeung, E., Masek, T., Rojo, J., Levy, J., 

Arunachalam, S., Miller, S., Barrett, S., Kuhn, S., 

Waitz, I. 2014. Assessing the impact of aviation 

environmental policies on public health. Transport 

Policy 34: 21–28. https://www.sciencedirect.com/

science/article/pii/ 

S0967070X14000468?via%3Dihub. 

48 Kim, B., Nakada, K., Wayson, R., Christie, S., 

Paling, C., Bennett, M., Raper, D., Raps, V., Levy, 

J., Roof, C. 2015. Understanding Airport Air Quality 

and Public Health Studies Related to Airports. 

Airport Cooperative Research Program, ACRP 

Report 135. https://trid.trb.org/view/1364659. 

49 Kim, B., Nakada, K., Wayson, R., Christie, S., 

Paling, C., Bennett, M., Raper, D., Raps, V., Levy, 

J., Roof, C. 2015. Understanding Airport Air Quality 

and Public Health Studies Related to Airports. 

Airport Cooperative Research Program, ACRP 

Report 135, p. 39. https://trid.trb.org/view/1364659. 

50Wing, S.E., Larson, T.V., Hudda, N., 

Boonyarattaphan, S., Fruin, S., Ritz, B. 2020. 

Preterm birth among infants exposed to in utero 

ultrafine particles from aircraft emissions. Environ. 

Health Perspect. 128, https://doi.org/10.1289/ 

EHP5732. 

51Hudda, N., Simon, N.C., Zamore, W., Durant, 

J.L. 2018. Aviation-related impacts on ultrafine 

number concentrations outside and inside 

residences near an airport. Environ. Sci. Technol. 

52: 1765–1772. https://pubs.acs.org/doi/abs/ 

10.1021/acs.est.7b05593. 

52Hudda, N., Simon, M.C., Zamore, W., Brugge, 

D., Durant, J.L. 2016. Aviation emissions impact 

ultrafine particle concentrations in the greater 

Boston area. Environ. Sci. Technol. 50: 8514–8521. 

https://pubs.acs.org/doi/abs/10.1021/ 

acs.est.6b01815. 

53Stacey, B. 2019. Measurement of ultrafine 

particles at airports: A review. Atmos. Environ. 198: 

463–477. https://www.sciencedirect.com/science/ 

article/pii/S1352231018307313. 

54Masiol M, Harrison RM. Quantification of air 

quality impacts of London Heathrow Airport (UK) 

from 2005 to 2012. Atmos Environ 2017;116:308– 

19. https://doi.org/10.1016/j.atmosenv.2015.06.048. 

55 Keuken, M.P., Moerman, M., Zandveld, P., 

Henzing, J.S., Hoek, G., 2015. Total and sizeresolved particle number and black carbon 

concentrations in urban areas near Schiphol airport 

(the Netherlands). Atmos. Environ. 104: 132–142. 

https://www.sciencedirect.com/science/article/pii/ 

S1352231015000175?via%3Dihub. 

56Pirhadi, M., Mousavi, A., Sowlat, M.H., 

Janssen, N.A.H., Cassee, F.R., Sioutas, C., 2020. 

Relative contributions of a major international 

airport activities and other urban sources to the 

particle number concentrations (PNCs) at a nearby 

monitoring site. Environ. Pollut, 260: 114027. 

https://www.sciencedirect.com/science/article/pii/ 

S0269749119344987?via%3Dihub. 

57Stacey, B., Harrison, R.M., Pope, F., 2020. 

Evaluation of ultrafine particle concentrations and 

size distributions at London Heathrow Airport. 

Atmos. Environ., 222: 117148. https://

www.sciencedirect.com/science/article/pii/ 

S1352231019307873?via%3Dihub. 

58Ungeheuer, F., Pinxteren, D., Vogel, A. 2021. 

Identification and source attribution of organic 

compounds in ultrafine particles near Frankfurt 

International Airport. Atmos. Chem. Phys. 21: 

3763–3775. https://doi.org/10.5194/acp-21-3763- 

2021. 

59Zhang, X., Karl, M. Zhang, L. Wang, J., 2020. 

Influence of Aviation Emission on the Particle 

Number Concentration near Zurich Airport. 

Environ. Sci. Technol. 54: 14161–14171. https://

doi.org/10.1021/acs.est.0c02249. 

60University of Washington. 2019. Mobile 

Observations of Ultrafine Particles: The Mov-UP 

study report. https://deohs.washington.edu/movup. 

61Habre. R., Zhou, H., Eckel, S., Enebish, T., 

Fruin, S., Bastain, T., Rappaport, E. Gilliland, F. 

2018. Short-term effects of airport-associated 

ultrafine particle exposure on lung function and 

inflammation in adults with asthma. Environment 

International 118: 48–59. https://doi.org/10.1016/ 

j.envint.2018.05.031. 

62He, R.W., Shirmohammadi, F., Gerlofs-Nijland, 

M.E., Sioutas, C., & Cassee, F.R. 2018. Prodeteriorating building materials such as 

stone, concrete and marble.45

D. Near-Source Impacts on Air Quality 

and Public Health 

Airport activity can adversely impact 

air quality in the vicinity of airports. 

Furthermore, these adverse impacts may 

disproportionately impact sensitive 

subpopulations. A recent study by Yim 

et al. (2015) assessed global, regional, 

and local health impacts of civil 

aviation emissions, using modeling 

tools that address environmental 

impacts at different spatial scales.46 The 

study attributed approximately 16,000 

premature deaths per year globally to 

global aviation emissions, with 87 

percent attributable to PM2.5. The study 

concludes that about a third of these 

mortalities are attributable to PM2.5

exposures within 20 kilometers of an 

airport. Another study focused on the 

continental United States estimated 210 

deaths per year attributable to PM2.5

from aircraft.47 While there are 

considerable uncertainties associated 

with such estimates, these results 

suggest that in addition to the 

contributions of PM2.5 emissions to 

regional air quality, impacts on public 

health of these emissions in the vicinity 

of airports are an important public 

health concern. 

A significant body of research has 

addressed pollutant levels and potential 

health effects in the vicinity of airports. 

Much of this research was synthesized 

in a 2015 report published by the 

Airport Cooperative Research Program 

(ACRP), conducted by the 

Transportation Research Board.48 The 

report concluded that PM2.5

concentrations in and around airports 

vary considerably, ranging from 

‘‘relatively low levels to those that are 

close to the NAAQS, and in some cases, 

exceeding the standards.’’ 49

Furthermore, the report states (p. 40) 

that ‘‘existing studies indicate that 

ultrafine particle concentrations are 

highly elevated at an airport (i.e., near 

a runway) with particle counts that can 

be orders of magnitude higher than 

background with some persistence 

many meters downwind (e.g., 600 m). 

Finally, the report concludes that PM2.5

dominates overall health risks posed by 

airport emissions. Moreover, one 

recently published study concluded that 

emissions from aircraft play an etiologic 

role in pre-term births, independent of 

noise and traffic-related air pollution 

exposures.50

Since the publication of the 2015 

ACRP literature review, a number of 

studies conducted in the U. S. have 

been published which concluded that 

ultrafine particle number concentrations 

were elevated downwind of commercial 

airports, and that proximity to an airport 

also increased particle number 

concentrations within residences. 

Hudda et al. investigated ultrafine 

particle number concentrations (PNC) 

inside and outside 16 residences in the 

Boston metropolitan area. They found 

elevated outdoor PNC within several 

kilometers of the airport. They also 

found that aviation-related PNC 

infiltrated indoors and resulted in 

significantly higher indoor PNC.51 In 

another study in the vicinity of Logan 

airport, Hudda et al. analyzed PNC 

impacts of aviation activities.52 They 

found that, at sites 4.0 and 7.3 km from 

the airport, average PNCs were 2 and 

1.33-fold higher, respectively, when 

winds were from the direction of the 

airport compared to other directions, 

indicating that aviation impacts on PNC 

extend many kilometers downwind of 

Logan airport. Stacey (2019) conducted 

a literature survey and concluded that 

the literature consistently reports that 

particle numbers close to airports are 

significantly higher than locations 

distant and upwind of airports, and that 

the particle size distribution is different 

from traditional road traffic, with more 

extremely fine particles.53 Similar 

findings have been published from 

European studies.54 55 56 57 58 59 Results of 

a monitoring study of communities near 

Seattle-Tacoma International Airport 

also found higher levels of ultrafine PM 

near the airport, and an impacted area 

larger than at near-roadway sites.60 The 

PM associated with aircraft landing 

activity was also smaller in size, with 

lower black carbon concentrations than 

near-roadway samples. As discussed 

above, PM2.5 exposures are associated 

with a number of serious, adverse health 

effects. Further, the PM attributable to 

aircraft emissions has been associated 

with potential adverse health 

impacts.61 62 For example, He et al. 


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Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6333 

inflammatory responses to PM(0.25) from airport 

and urban traffic emissions. The Science of the total 

environment, 640–641, 997–100. https://

www.sciencedirect.com/science/article/pii/ 

S0048969718320394?via%3Dihub. 63Riley, K., Cook, R., Carr, E., Manning, B. 2021. 

A Systematic Review of The Impact of Commercial 

Aircraft Activity on Air Quality Near Airports. City 

and Environment Interactions, 100066. https://

doi.org/10.1016/j.cacint.2021.100066. 64Bendtsen, K. M., Bengtsen, E., Saber, A., Vogel, 

U. 2021. A review of health effects associated with 

exposure to jet engine emissions in and around 

airports. Environ. Health 20:10. https://doi.org/ 

10.1186/s12940-020-00690-y. 

65Health Effects institute. ‘‘Special Report 17: A 

Special Report of the Institute’s Panel on the Health 

Effects of Traffic-Related Air Pollution.’’ January, 

2010. https://www.healtheffects.org/publication/ 

traffic-related-air-pollution-critical-reviewliterature-emissions-exposure-and-health. 

66https://aspm.faa.gov/opsnet/sys/main.asp. 

67 2017 National Emissions Inventory: Aviation 

Component, Eastern Research Group, Inc., July 25, 

2019, EPA Contract No. EP–C–17–011, Work Order 

No. 2–19. Available at https://www.epa.gov/airemissions-inventories/2017-national-emissionsinventory-nei-data (last accessed on June 27, 2021). 

See section 3.2 for airports and aircraft related 

emissions in the Technical Supporting Document 

for the 2017 National Emissions Inventory, January 

2021 Updated Release. Available at https://

www.epa.gov/sites/production/files/2021-02/ 

documents/nei2017_tsd_full_jan2021.pdf (last 

accessed on June 27, 2021). 

68These data were obtained using radar-informed 

data from the FAA Enhanced Traffic Management 

System (ETMS). The annual fuel burn and 

emissions inventories at selected top US airports 

were based on the 2015 FAA flight operations 

database. The fraction of total PM emissions from 

aircraft covered by the proposed PM standards is 

based on the ratio of total PM emissions from flights 

by engines with thrust rating >26.7 kN compared 

to PM emissions from the whole fleet at each 

airport. 

69Cook, R. Memorandum to Docket EPA–HQ– 

OAR–2019–0660, July 28, 2021, ’’ Estimation of 

2017 Emissions Contributions of Turbine Aircraft 

>26.7 kN to NOX and PM2.5 as a Percentage of All 

Mobile PM2.5 for the Counties and MSAs in Which 

the Airport Resides, 25 Largest Carrier Operations.’’ 

(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. 

Because of these potential impacts, a 

systematic literature review was 

recently conducted to identify peerreviewed literature on air quality near 

commercial airports and assess the 

quality of the studies.63 The systematic 

review identified seventy studies for 

evaluation. These studies consistently 

showed that particulate matter, in the 

form of ultrafine PM (UFP), is elevated 

in and around airports. Furthermore, 

many studies showed elevated levels of 

black carbon, criteria pollutants, and 

polycyclic aromatic hydrocarbons as 

well. Finally, the systematic review, 

while not focused on health effects, 

identified a limited number of 

references reporting adverse health 

effects impacts, including increased 

rates of premature death, pre-term 

births, decreased lung function, 

oxidative DNA damage and childhood 

leukemia. More research is needed 

linking particle size distributions to 

specific airport activities, and proximity 

to airports, characterizing relationships 

between different pollutants, evaluating 

long-term impacts, and improving our 

understanding of health effects. 

A systematic review of health effects 

associated with exposure to jet engine 

emissions in the vicinity of airports was 

also recently published.64 This study 

concluded that literature on health 

effects was sparse, but jet engine 

emissions have physicochemical 

properties similar to diesel exhaust 

particles, and that exposure to jet engine 

emissions is associated with similar 

adverse health effects as exposure to 

diesel exhaust particles and other traffic 

emissions. A 2010 systematic review by 

the Health Effects Institute (HEI) 

concluded that evidence was sufficient 

to support a causal relationship between 

exposure to traffic-related air pollution 

and exacerbation of asthma among 

children, and suggestive of a causal 

relationship for childhood asthma, nonasthma respiratory symptoms, impaired 

lung function and cardiovascular 

mortality.65

E. Contribution of Aircraft Emissions to 

PM in Selected Areas 

This section provides background on 

the contribution of aircraft engine 

emissions to local PM concentrations. In 

some areas with large commercial 

airports, turbine engine aircraft can 

make a significant contribution to 

ambient PM2.5. To evaluate these 

potential impacts, we identified the 25 

airports where commercial aircraft 

operations are the greatest, based on 

data for 2017 from the Federal Aviation 

Administration (FAA) Air Traffic Data 

System (ATADS).66 These 25 

commercial airports are located in 24 

counties and 22 metropolitan statistical 

areas (MSAs). We compared the 

contributions of these airports to 

emissions at both the county and MSA 

levels. Comparisons at both scales 

provide a fuller picture of how airports 

are impacting local air quality. Figure 

III–1 depicts the contribution to countylevel PM2.5 direct emissions from all 

turbine aircraft in that county with rated 

output of greater than 26.7 kN. 

Emissions data were obtained from the 

EPA 2017 National Emissions Inventory 

(NEI).67 The contributions of engines 

greater than 26.7 kN rated output to 

total turbine engine emissions at 

individual airports were estimated 

based on FAA data.68 At the county 

level, contributions to total mobile 

source PM2.5 emissions range from less 

than 1 to almost 14 percent. However, 

it should be noted that two airports 

cross county lines—Hartsfield-Jackson 

Atlanta International Airport (Clayton 

and Fulton counties) and O’Hare (Cook 

and DuPage counties). For those 

airports, percentages are calculated for 

the sum of the two counties. In addition, 

five of these counties are in 

nonattainment for either the PM2.5 or 

PM10 standard. When emissions from 

these airports are considered as part of 

the entire MSA, the contribution is 

much smaller. Figure III–2 depicts the 

contributions at the metropolitan 

statistical area (MSA) instead of the 

county level, and contributions across 

airports range from 0.4 to 3 percent. 

Details of this analysis are described in 

a memorandum to the docket.69

BILLING CODE 6560–50–P 


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khammond on DSKJM1Z7X2PROD with PROPOSALS3EP03FE22.027</GPH> EP03FE22.028</GPH>

10.00 

-

C 

Q) 

u 8.00 ... 

(I) 

Q. 

6.00 

4.00 

3.50 

3.00 

2.50 

.... 

C 2.00 Q) 

u 

... 

Q) 

Q. 1.50 

1.00 

0.50 

0.00 

2017 Turbine Aircraft >26.7 kN PM2.5 as a Percent of All Mobile PM2.5 

for the County or Counties in Which the Airport Resides, 25 Largest Carrier 

Operations 

"""" 

Figure 111-1 

2017 Turbine Aircraft >26.7 kN PM2.5 as a Percent of All Mobile PM2.5 

for the MSA in Which the Airport Resides, 

25 Largest Carrier Operations 

''"""''"'' ''"'""" 

Figure 111-2 
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6335 

70 Kinsey, J.S., Hays, M.D., Dong, Y., Williams, 

D.C. Logan, R. 2011. Chemical characterization of 

the fine particle emissions from commercial aircraft 

engines during the aircraft particle emissions 

experiment (APEX) 1–3. Environ. Sci. Technol. 

45:3415–3421. https://pubs.acs.org/doi/10.1021/ 

es103880d. 

71https://www.epa.gov/national-air-toxicsassessment. 

72Fair treatment means that ‘‘no group of people 

should bear a disproportionate burden of 

environmental harms and risks, including those 

resulting from the negative environmental 

consequences of industrial, governmental and 

commercial operations or programs and policies.’’ 

Meaningful involvement occurs when ‘‘(1) 

potentially affected populations have an 

appropriate opportunity to participate in decisions 

about a proposed activity [e.g., rulemaking] that 

will affect their environment and/or health; (2) the 

public’s contribution can influence [the EPA’s 

rulemaking] decision; (3) the concerns of all 

participants involved will be considered in the 

decision-making process; and (4) [the EPA will] 

seek out and facilitate the involvement of those 

potentially affected’’ A potential EJ concern is 

defined as ‘‘the actual or potential lack of fair 

treatment or meaningful involvement of minority 

populations, low-income populations, tribes, and 

indigenous peoples in the development, 

implementation and enforcement of environmental 

laws, regulations and policies.’’ See ‘‘Guidance on 

Considering Environmental Justice During the 

Development of an Action.’’ Environmental 

Protection Agency, https://www.epa.gov/ 

environmentaljustice. 

73 ‘‘Technical Guidance for Assessing 

Environmental Justice in Regulatory Analysis.’’ 

Epa.gov, Environmental Protection Agency, https:// 

www.epa.gov/sites/production/files/2016-06/ 

documents/ejtg_5_6_16_v5.1.pdf (June 2016). 

BILLING CODE 6560–50–C 

F. Other Pollutants Emitted by Aircraft 

In addition to particulate matter, a 

number of other criteria pollutants are 

emitted by the aircraft which are the 

subject of this proposed rule. These 

pollutants, which are not covered by the 

rule, include nitrogen oxides (NOX), 

including nitrogen dioxide (NO2), 

volatile organic compounds (VOC), 

carbon monoxide (CO), and sulfur 

dioxide (SO2). Aircraft also contribute to 

ambient levels of hazardous air 

pollutants (HAP), compounds that are 

known or suspected human or animal 

carcinogens, or that have noncancer 

health effects. These compounds 

include, but are not limited to, benzene, 

1,3-butadiene, formaldehyde, 

acetaldehyde, acrolein, polycyclic 

organic matter (POM), and certain 

metals. Some POM and HAP metals are 

components of PM2.5 mass measured in 

turbine engine aircraft emissions.70

The term polycyclic organic matter 

(POM) defines a broad class of 

compounds that includes the polycyclic 

aromatic hydrocarbon compounds 

(PAHs). POM compounds are formed 

primarily from combustion and are 

present in the atmosphere in gas and 

particulate form. Metal compounds 

emitted from aircraft turbine engine 

combustion include chromium, 

manganese, and nickel. Several POM 

compounds, as well as hexavalent 

chromium, manganese compounds and 

nickel compounds are included in the 

National Air Toxics Assessment, based 

on potential carcinogenic risk.71 In 

addition, as mentioned previously, 

deposition of metallic compounds can 

have ecological effects. Impacts of POM 

and metals are further discussed in the 

memorandum to the docket referenced 

above. 

G. Environmental Justice 

Executive Order 12898 (59 FR 7629, 

February 16, 1994) establishes federal 

executive policy on environmental 

justice. It directs federal agencies, to the 

greatest extent practicable and 

permitted by law, to make achieving 

environmental justice part of their 

mission by identifying and addressing, 

as appropriate, disproportionately high 

and adverse human health or 

environmental effects of their programs, 

policies, and activities on minority 

populations and low-income 

populations in the United States. EPA 

defines environmental justice as the fair 

treatment and meaningful involvement 

of all people regardless of race, color, 

national origin, or income with respect 

to the development, implementation, 

and enforcement of environmental laws, 

regulations, and policies.72

Executive Order 14008 (86 FR 7619, 

February 1, 2021) also calls on federal 

agencies to make achieving 

environmental justice part of their 

missions ‘‘by developing programs, 

policies, and activities to address the 

disproportionately high and adverse 

human health, environmental, climaterelated and other cumulative impacts on 

disadvantaged communities, as well as 

the accompanying economic challenges 

of such impacts.’’ It also declares a 

policy ‘‘to secure environmental justice 

and spur economic opportunity for 

disadvantaged communities that have 

been historically marginalized and 

overburdened by pollution and underinvestment in housing, transportation, 

water and wastewater infrastructure and 

health care.’’ Under Executive Order 

13563, federal agencies may consider 

equity, human dignity, fairness, and 

distributional considerations, where 

appropriate and permitted by law. 

EPA’s June 2016 ‘‘Technical Guidance 

for Assessing Environmental Justice in 

Regulatory Analysis’’ provides 

recommendations on conducting the 

highest quality analysis feasible, 

recognizing that data limitations, time 

and resource constraints, and analytic 

challenges will vary by media and 

regulatory context.73

When assessing the potential for 

disproportionately high and adverse 

health or environmental impacts of 

regulatory actions on minority 

populations, low-income populations, 

tribes, and/or indigenous peoples, the 

EPA strives to answer three broad 

questions: (1) Is there evidence of 

potential EJ concerns in the baseline 

(the state of the world absent the 

regulatory action)? Assessing the 

baseline will allow the EPA to 

determine whether pre-existing 

disparities are associated with the 

pollutant(s) under consideration (e.g., if 

the effects of the pollutant(s) are more 

concentrated in some population 

groups). (2) Is there evidence of 

potential EJ concerns for the regulatory 

option(s) under consideration? 

Specifically, how are the pollutant(s) 

and its effects distributed for the 

regulatory options under consideration? 

And, (3) do the regulatory option(s) 

under consideration exacerbate or 

mitigate EJ concerns relative to the 

baseline? It is not always possible to 

quantitatively assess these questions. 

EPA’s 2016 Technical Guidance does 

not prescribe or recommend a specific 

approach or methodology for 

conducting an environmental justice 

analysis, though a key consideration is 

consistency with the assumptions 

underlying other parts of the regulatory 

analysis when evaluating the baseline 

and regulatory options. Where 

applicable and practicable, the Agency 

endeavors to conduct such an analysis. 

Going forward, EPA is committed to 

conducting environmental justice 

analysis for rulemakings based on a 

framework similar to what is outlined in 

EPA’s Technical Guidance, in addition 

to investigating ways to further weave 

environmental justice into the fabric of 

the rulemaking process. 


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74Rowangould, G.M. (2013) A census of the nearroadway population: Public health and 

environmental justice considerations. Trans Res D 

25: 59–67. https://dx.doi.org/10.1016/ 

j.trd.2013.08.003. 

75Marshall, J.D., Swor, K.R., Nguyen, N.P. (2014) 

Prioritizing environmental justice and equality: 

Diesel emissions in Southern California. Environ 

Sci Technol 48: 4063–4068. https://doi.org/10.1021/ 

es405167f. 

76Marshall, J.D. (2000) Environmental inequality: 

Air pollution exposures in California’s South Coast 

Air Basin. Atmos Environ 21: 5499–5503. https:// 

doi.org/10.1016/j.atmosenv.2008.02.005. 

77Tessum, C.W., Paolella, D.A., Chambliss, SE, 

Apte, J.S., Hill, J.D., Marshall, J.D. (2021) PM2.5

polluters disproportionately and systemically affect 

people of color in the United States. Science 

Advances 7:eabf4491. https://www.science.org/doi/ 

10.1126/sciadv.abf4491. 

78Mohai, P., Pellow, D., Roberts Timmons, J. 

(2009) Environmental justice. Annual Reviews 34: 

405–430. https://doi.org/10.1146/annurev-environ082508-094348. 

79Henry, R.C., Mohan, S., Yazdani, S. (2019) 

Estimating potential air quality impact of airports 

on children attending the surrounding schools. 

Atmospheric Environment, 212: 128–135. https://

www.sciencedirect.com/science/article/pii/ 

S1352231019303516?via%3Dihub. 

80Rissman, J., Arunachalam, S., BenDor, T., West, 

J.J. (2013) Equity and health impacts of aircraft 

emissions at the Hartfield-Jackson Atlanta 

International Airport, Landscape and Urban 

Planning 120: 234–247. https://

www.sciencedirect.com/science/article/pii/ 

S0169204613001382. 

81McNair, A. (2020) Investigation of 

environmental justice analysis in airport planning 

practice from 2000 to 2010. Transp. Research Part 

D 81:102286. https://www.sciencedirect.com/

science/article/pii/S1361920919311149?

via%3Dihub. 

82Woodburn, A. (2017) Investigating 

neighborhood change in airport-adjacent 

communities in multiairport regions from 1970 to 

2010. Journal of the Transportation Research Board, 

2626, 1–8. 

83EPA anticipates that the results of the study 

will be released publicly in a separate document 

from the final rule. 

Numerous studies have found that 

environmental hazards such as air 

pollution are more prevalent in areas 

where people of color and low-income 

populations represent a higher fraction 

of the population compared with the 

general population, including near 

transportation sources.74 75 76 77 78

As described in Section III.D, 

concentrations of PM increase with 

proximity to an airport. Air pollution 

can disproportionately impact sensitive 

subpopulations near airports. Henry et 

al. (2019) studied impacts of several 

California airports on surrounding 

schools and found that over 65,000 

students spend 1 to 6 hours a day 

during the academic year being exposed 

to airport pollution, and the percentage 

of impacted students was higher for 

those who were economically 

disadvantaged.79 Rissman et al. (2013) 

studied PM2.5 at the Hartsfield-Jackson 

Atlanta International Airport and found 

that the relationship between minority 

population percentages and aircraftderived PM was found to grow stronger 

as concentrations increased.80

Additional studies have reported that 

many communities in close proximity to 

airports are disproportionately 

represented by minorities and lowincome populations. McNair (2020) 

describes nineteen major airports that 

underwent capacity expansion projects 

between 2000 and 2010, thirteen of 

which met characteristics of race, 

ethnicity, nationality and/or income 

that indicate a disproportionate impact 

on these residents.81 Woodburn (2017) 

reports on changes in communities near 

airports from 1970–2010, finding 

suggestive evidence that at many hub 

airports over time, the presence of 

marginalized groups residing in close 

proximity to airports increased.82

Although not being conducted as part 

of this rulemaking, EPA is conducting a 

demographic analysis to explore 

whether populations living nearest the 

busiest runways show patterns of racial 

and socioeconomic disparity.83 This 

will help characterize the state of 

environmental justice concerns and 

inform potential future actions. Finely 

resolved population data (i.e., 30 square 

meters) will be paired with census block 

group demographic characteristics to 

evaluate if people of color, children, 

indigenous populations, and lowincome 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. 

In summary, the proposed inproduction standards for both PM mass 

and PM number are levels that all 

aircraft engines in production currently 

meet in order to align with ICAO’s 

standards. Thus, the proposed standards 

are not expected to result in emission 

reductions, beyond the business-asusual fleet turnover that would occur 

absent of the proposed standards. 

Therefore, we do not anticipate an 

improvement in air quality for those 

who live near airports where these 

aircraft operate. 

IV. Details for the Proposed Rule 

In considering what PM emissions 

standards for aircraft engines are 

appropriate to adopt under section 231 

of the CAA, EPA, after consultation with 

FAA, took into consideration the 

importance of both controlling PM 

emissions and international 

harmonization of aviation requirements. 

In addition, the EPA gave significant 

weight to the U.S.’s treaty obligations 

under the Chicago Convention in 

determining the need for and 

appropriate levels of PM standards. 

These considerations led the EPA to 

propose aircraft engine PM standards 

based on engine standards adopted by 

ICAO. When developing the PM 

standards, ICAO looked at three 

different methods of measuring the 

amount of PM emitted. The first is PM 

mass, or a measure of the total weight 

of the particles produced over the test 

cycle. This is how the EPA has 

historically set PM emissions standards 

for other sectors. Second, ICAO 

considered PM number, or the number 

of particles produced by the engine over 

the test cycle. These are two different 

methods of measuring the same 

pollutant, PM, but each provides 

distinct and valuable information. 

Third, ICAO developed PM mass 

concentration standards, as a 

replacement to the existing standards 

based on smoke number. 

EPA’s proposed action consists of 

three key parts: (1) A proposal for PM 

mass and number emissions standards 

for aircraft gas turbine engines, (2) a 

change in test procedure and form of the 

existing standards—from smoke number 

to PM mass concentration, and (3) new 

testing and measurement procedures for 

the PM emission standards and various 

updates to the existing gaseous exhaust 

emissions test procedures. 

Sections IV.A through IV.C describe 

the proposed mass, number, and mass 

concentration standards for aircraft 

engines. Section IV.D describes the 

proposed test procedures and 

measurement procedures associated 

with the PM standards. Section IV.E 

presents information related to the 

proposed reporting requirements. 

As discussed above in Section III.A, 

PM2.5 consists of both volatile and 

nonvolatile PM, although only 

nonvolatile PM would be covered by the 

proposed standards. Only nonvolatile 

PM is present at the engine exit because 

the exhaust temperature is too high for 

volatile PM to form. The volatile PM (or 

secondary PM) is formed as the engine 

exhaust plume cools and mixes with the 

ambient air. The result of this is that the 

volatile PM is significantly influenced 

by the ambient conditions (or ambient 

air background composition). Because of 

this complexity, a test procedure to 

measure volatile PM has not yet been 

developed for aircraft engines. In order 

to directly measure nonvolatile PM, 

ICAO agreed to adopt a measurement 

procedure, as described below in 

Section IV.D, which is based on 

conditions that prevent the formation of 

volatile PM upstream of the 

measurement instruments. The intent of 


khammond on DSKJM1Z7X2PROD with PROPOSALS3
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6337 

84 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017, III–4–3 & III– 

4–4pp. Available at https://www.icao.int/ 

publications/catalogue/cat_2021_en.pdf (last 

accessed November 15, 2021). The ICAO Annex 16 

Volume II is found on page 17 of the ICAO Products 

& Services Catalog, English Edition of the 2021 

catalog, and it is copyright protected; Order No. 

AN16–2. The ICAO Annex 16, Volume II, Fourth 

Edition, includes Amendment 10 of January 1, 

2021. Amendment 10 is also found on page 17 of 

this ICAO catalog, and it is copyright protected; 

Order No. AN 16–2/E/12. 

85 In most cases, the engine manufacturer applies 

to FAA for the type certification; however, in some 

cases the applicant may be different than the 

manufacturer (e.g., designer). 

this approach is to improve the 

consistency and repeatability of the 

nvPM measurement procedure. 

Due to the international nature of the 

aviation industry, there is an advantage 

to working within ICAO, in order to 

secure the highest practicable degree of 

uniformity in international aviation 

regulations and standards. Uniformity 

in international aviation regulations and 

standards is a goal of the Chicago 

Convention, because it ensures that 

passengers and the public can expect 

similar levels of protection for safety 

and human health and the environment 

regardless of manufacturer, airline, or 

point of origin of a flight. Further, it 

helps prevent barriers in the global 

aviation market, benefiting both U.S. 

aircraft engine manufacturers and 

consumers. 

When developing new emissions 

standards, ICAO/CAEP seeks to capture 

the technological advances made in the 

control of emissions through the 

adoption of anti-backsliding standards 

reflecting the current state of 

technology. The PM standards the EPA 

is proposing were developed using this 

approach. Thus, the adoption of these 

aircraft engine standards into U.S. law 

would simultaneously prevent aircraft 

engine PM levels from increasing 

beyond their current levels, align U.S. 

domestic standards with the ICAO 

standards for international 

harmonization, and help the U.S. meet 

its treaty obligations under the Chicago 

Convention. 

These proposed standards would also 

allow U.S. manufacturers of covered 

aircraft engines to remain competitive in 

the global marketplace. The ICAO 

aircraft engine PM emission standards 

have been, or are being, adopted by 

other ICAO member states that certify 

aircraft engines. In the absence of U.S. 

standards implementing the ICAO 

aircraft engine PM emission standards, 

the U.S. would not be able to certify 

aircraft engines to the PM standards. In 

this case, U.S. civil aircraft engine 

manufacturers could be forced to seek 

PM emissions certification from an 

aviation certification authority of 

another country in order to market and 

operate their aircraft engines 

internationally. Foreign certification 

authorities may not have the resources 

to certify aircraft engines from U.S. 

manufacturers in a timely manner, 

which could lead to delays in these 

engines being certified. Thus, U.S. 

manufacturers could be at a 

disadvantage if the U.S. does not adopt 

standards that are at least as stringent as 

the ICAO standards for PM emissions. 

The proposed action to adopt in the U.S. 

PM standards that match the ICAO 

standards would help ensure 

international consistency and 

acceptance of U.S. manufactured 

engines worldwide. 

The EPA considered whether to 

propose standards more stringent than 

the ICAO standards. As noted above, the 

EPA considered both the need for 

emissions reductions and the 

international nature of the aircraft 

industry and air travel in evaluating 

whether to propose more stringent 

standards. These considerations have 

historically led the EPA to adopt 

international standards developed 

through ICAO. The EPA concluded that 

proposing to adopt the ICAO PM 

standards in place of more stringent 

standards is appropriate in part because 

international uniformity and regulatory 

certainty are important elements of 

these proposed standards. This is 

especially true for these proposed 

standards because they change our 

approach to regulating aircraft PM 

emissions from past smoke 

measurements to the measurement of 

nvPM mass and number for the first 

time. It is appropriate to gain experience 

from the implementation of these nvPM 

standards before considering whether to 

adopt more stringent nvPM mass and/or 

number standards, or whether another 

approach to PM regulation would better 

address the health risks of PM emissions 

from aircraft engines. Additionally, the 

U.S. Government played a significant 

role in the development of these 

proposed standards. The EPA believes 

that international cooperation on 

aircraft emissions brings substantial 

benefits overall to the United States. 

Having invested significant effort to 

develop these standards and obtain 

international consensus for ICAO to 

adopt these standards, a decision by the 

United States to deviate from them 

might well undermine future efforts by 

the United States to seek international 

consensus on aircraft emissions 

standards. For these reasons, EPA 

placed significant weight on 

international regulatory uniformity and 

certainty and is proposing standards 

that match the standards which EPA 

worked to develop and adopt at ICAO, 

and is not proposing more stringent 

standards. 

A. PM Mass Standards for Aircraft 

Engines 

1. Applicability of Standards 

These proposed standards for PM 

mass, like the ICAO standards, would 

apply to all subsonic turbofan and 

turbojet engines of a type or model with 

a rated output (maximum thrust 

available for takeoff) greater than 26.7 

kN whose date of manufacture is on or 

after January 1, 2023.84 These proposed 

standards would not apply to engines 

manufactured prior to this applicability 

date. 

The level of the proposed standard 

would vary based on when the initial 

type certification application is 

submitted.85 Engines for which the type 

certificate application was first 

submitted on or after January 1, 2023 

would be subject to the new type level 

in Section IV.A.2 below. These engines 

are new engines that have not been 

previously certificated. 

Engines manufactured on or after 

January 1, 2023 would be subject to the 

in-production level, in Section IV.A.3 

below. 


khammond on DSKJM1Z7X2PROD with PROPOSALS3
6338 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

86 ICAO Aircraft Engine Emissions Databank, July 

20, 2021, ‘‘edb-emissions-databank v28C 

(web).xlsx’’, European Union Aviation Safety 

Agency (EASA), https://www.easa.europa.eu/

domains/environment/icao-aircraft-engineemissions-databank. 

87Note, EPA ICR number 2427.06 ‘‘Aircraft 

Engines—Supplemental information related to 

Exhaust Emissions’’ also collects aircraft nvPM 

data. In the interest of using the most up to date 

information, the ICAO EDB was used because it has 

been updated more recently than EPA data. The 

EPA should be receiving new data from this ICR in 

Feb. 2022. 

2. New Type nvPM Mass Numerical 

Emission Limits for Aircraft Engines 

Aircraft engines with a rated output 

(rO), maximum thrust available for takeoff, greater than 26.7 kN and whose 

initial type certification application is 

submitted to the FAA on or after 

January 1, 2023 shall not exceed the 

level, as defined by Equation IV–1. As 

described in Section IV.D, the nvPM 

Mass limit is based on mg of PM 

divided by kN of thrust, as determined 

over the LTO cycle. 

3. In Production nvPM Mass Numerical 

Emission Limits for Aircraft Engines 

Aircraft engines that are 

manufactured on or after January 1, 

2023 shall not exceed the level, as 

defined by Equation IV–2. 

4. Graphical Representation of nvPM 

Mass Numerical Emission Limits 

Figure IV–1 shows how the proposed 

nvPM mass emission limits compare to 

known in-production engines. 

Data shown in this figure is from the 

ICAO Engine Emissions Databank 

(EEDB).86 87

B. PM Number Standards for Aircraft 

Engines 

1. Applicability of Standards 

These proposed standards for PM 

number, like the ICAO standards, would 

apply to all subsonic turbofan and 

turbojet engines of a type or model with 

a rated output greater than 26.7 kN 

whose date of manufacture is on or after 

January 1, 2023.88 These proposed 

standards would not apply to engines 

manufactured prior to this applicability 

date. 

The level of the proposed standard 

would vary based on when the initial 

type certification application is 

submitted. Engines for which the type 


khammond on DSKJM1Z7X2PROD with PROPOSALS3EP03FE22.029</GPH> EP03FE22.030</GPH> EP03FE22.031</GPH>

l'M {1251.1- 6. 914 • rO, 26, 7 < rO :S 150.klV 

n~ - = 214. 0, rO > 1SOlrN 

Equation IV-1 

P;.,. f4646,9-21.497 * rO, 26.7 < rO S 200lcN 

B'P ""'Nuill = l 347.5, rO > 200lcN 

Equation IV-2 

3000 

2500 

2000 

z 

1 

~ 1500 

:;; 

:;; 

'l; 

C: 

1000 

500 

0 

-· 

• 

-· 

• 

\ ! 

nvPM Mass vs. Rated Output 

(Current Production Engines) 

~ .... , 

! I I 

. ' I \I , ___ J_ ----- Mass Std - In Production 

,1 - Mass Std - New Type \ . ----- I' I • Engine Test Data '\ I \ I ' I • 

' ' ' ' ' ' I ' ' ' l 

' ' ' ' 

I 

I 

I 

' I 

I ·----···-1 I 

I 

I 

I 7 

I 

I --;~ ' ' l 

' I 

• ' ' ' I ' ' - II. ' ' ;--- ! 

I 

\i 

----------~---------- ,________ ---------- • l -. I , I 

... I I -· I • I I ,, I ~-- -· - a,1 • ' 0 100 200 300 400 500 600 

Rated Output (kN) 

Figure IV-1- nvPM mass standards compared to in-production engine LTO emission rates 
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6339 

88 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017, III–4–4pp. 

Available at https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). The ICAO Annex 16 Volume II is found 

on page 17 of the ICAO Products & Services Catalog, 

English Edition of the 2021 catalog, and it is 

copyright protected; Order No. AN16–2. The ICAO 

Annex 16, Volume II, Fourth Edition, includes 

Amendment 10 of January 1, 2021. Amendment 10 

is also found on page 17 of this ICAO catalog, and 

it is copyright protected; Order No. AN 16–2/E/12. 

89 ICAO Aircraft Engine Emissions Databank, July 

20, 2021, ‘‘edb-emissions-databank v28C 

(web).xlsx’’, European Union Aviation Safety 

Agency (EASA), https://www.easa.europa.eu/ 

domains/environment/icao-aircraft/-engineemissions/-databank (last accessed November 15, 

2021). 

certificate application was first 

submitted on or after January 1, 2023 

would be subject to the new type level 

in Section IV.B.2 below. These are new 

engines that have not been previously 

certificated. 

Engines manufactured on or after 

January 1, 2023 would be subject to the 

in-production level, in IV.B.3 below. 

2. New Type nvPM Number Numerical 

Emission Limits for Aircraft Engines 

Aircraft engines with a rated output 

greater than 26.7 kN and whose initial 

type certification application is 

submitted to the FAA on or after 

January 1, 2023 shall not exceed the 

level, as defined by Equation IV–3. As 

described in Section IV.D, the nvPM 

number limit is based on number of 

particles divided by kN of thrust, as 

determined over the LTO cycle. 

3. In Production nvPM Number 

Numerical Emission Limits for Aircraft 

Engines 

Aircraft engines that are 

manufactured on or after January 1, 

2023 shall not exceed the level, as 

defined by Equation IV–4. 

4. Graphical Representation of nvPM 

Number Numerical Emission Limits 

Figure IV–2 shows how the proposed 

nvPM number emission limits compare 

to known in-production engines. Data 

shown in this figure is from the ICA O 

Engine Emissions Databank (EEDB).89


khammond on DSKJM1Z7X2PROD with PROPOSALS3EP03FE22.032</GPH> EP03FE22.033</GPH> EP03FE22.034</GPH>

{1.499 * 1016 - 8. 080 * 101.

3 * rO, 26. 7 < rO S 150kN 

n.vPM11:111111 = z. '180 * 1015, rO > :ISOlcN 

Equation IV-3 

r. 669 * 1016 - 1.126 * 101.

4 * rO., 26.. 7 < rO S 200kN 

n11PM:mrm = li -o > .,,00,.N . 4. t 70 * 10 , • c. " 

Equation IV-4 

3.0E+16 

2.SE+16 

~2.0E+16 

~ 

~ ~ 

QI t 1.5E+16 ::, 

z 

~ 

'l; 

c 1.0E+16 

5.0E+15 

O.OE+OO 

' i 

' I 

' i ' ' I ' I 

' ! .. ' ' i 

' l 8 ' ,, l 

• , . 

', 

' .. 

' ' 

nvPM Number vs. Rated Output 

(Current Production Engines) 

I i 

----· Number Std - In Production 

--Number Std - New Type 

• Engine Test Data 

I 

I 

I " ' I ' 

~t\.. 

', 

' ' ' ' ' ' '· 

1---

!'\.. e ,----------~----------~----------~---------· C!II 1 •• _ i I l ( 

I 

_. _..= e l'nlll 1.I • I I ,,~-- • ei • 

0 100 200 300 400 500 600 

Rated Output (kN) 

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

rates 
6340 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

90 ICAO, 2019: Report of Eleventh Meeting, 

Montreal, 4–15 February 2019, Committee on 

Aviation Environmental Protection, Document 

10126, CAEP/11. It is found on page 26 of the 

English Edition of the ICAO Products & Services 

2021 Catalog and is copyright protected; Order No. 

10126. For purchase available at: https://

www.icao.int/publications/Pages/catalogue.aspx 

(last accessed November 15, 2021). The analysis 

performed to confirm the equivalence of the PM 

mass concentration standard and the SN standard 

is located in Appendix C (starting on page 3C–33) 

of this report. 

91 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017, III–4–3. 

Available at https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). The ICAO Annex 16 Volume II is found 

on page 17 of the ICAO Products & Services Catalog, 

English Edition of the 2021 catalog, and it is 

copyright protected; Order No. AN16–2. The ICAO 

Annex 16, Volume II, Fourth Edition, includes 

Amendment 10 of January 1, 2021. Amendment 10 

is also found on page 17 of this ICAO catalog, and 

it is copyright protected; Order No. AN 16–2/E/12. 

92 ICAO Aircraft Engine Emissions Databank, July 

20, 2021, ‘‘edb-emissions-databank v28C 

(web).xlsx’’, European Union Aviation Safety 

Agency (EASA), https://www.easa.europa.eu/ 

domains/environment/icao-aircraft/-engineemissions/-databank. 

C. PM Mass Concentration Standard for 

Aircraft Engines 

The current smoke number-based 

standards were adopted to reduce the 

visible smoke emitted by aircraft 

engines. Smoke number is quantified by 

measuring the opacity of a filter after 

soot has been collected upon it during 

the test procedure. Another means of 

quantifying the smoke from an engine 

exhaust is through PM mass 

concentration (PMmc). 

ICAO developed a PM mass 

concentration standard during the 

CAEP/10 cycle and adopted it in 2017. 

This PM mass concentration standard 

was developed to provide equivalent 

exhaust visibility control as the existing 

smoke number standard starting on 

January 1, 2020. With the EPA’s 

involvement, the ICAO PM mass 

concentration limit line was developed 

using measured smoke number and PM 

mass concentration data from several 

engines to derive a smoke number-toPM mass concentration correlation. This 

correlation was then used to transform 

the existing smoke number-based limit 

line into a generally equivalent PM mass 

concentration limit line, which was 

ultimately adopted by ICAO as the 

CAEP/10 PM mass concentration 

standard. The intention when the 

equivalent PM mass concentration 

standard was adopted was that 

equivalent visibility control would be 

maintained and testing would coincide 

with the PM mass and PM number 

measurement, thus removing the need 

to separately test and measure smoke 

number. 

While the ICAO PM mass 

concentration standard was intended to 

have equivalent visibility control as the 

existing SN standard, the method used 

to derive it was based on limited data 

and needed to be confirmed for 

regulatory purposes. Additional analysis 

was conducted during the CAEP/11 

cycle to confirm this equivalence. The 

EPA followed this work as it progressed, 

provided input during the process, and 

ultimately concurred with the results.90

The analysis, based on aerosol optical 

theory and visibility criterion, 

demonstrated with a high level of 

confidence that the ICAO PM mass 

concentration standard did indeed 

provide equivalent visibility control as 

the existing smoke number standard. 

This provided the justification for ICAO 

to agree to end applicability of the 

existing smoke number standard for 

engines subject to the PM mass 

concentration standard, effective 

January 1, 2023. 

1. PM Mass Concentration Standard 

The EPA is proposing to adopt a PM 

mass concentration standard for all 

aircraft engines with rated output 

greater than 26.7 kN and manufactured 

on or after January 1, 2023.91 This 

proposed standard has the same form, 

test procedures, and stringency as the 

CAEP/10 PM mass concentration 

standard adopted by ICAO in 2017. 

However, the applicability date 

proposed here is different than that 

agreed to by ICAO. The proposed PM 

mass concentration standard is based on 

the maximum concentration of PM 

emitted by the engine at any thrust 

setting, measured in micrograms (mg) 

per meter cubed (m3). This is similar to 

the current smoke standard, which is 

also based on the measured maximum at 

any thrust setting. Section IV.D 

describes the measurement procedure. 

Like the LTO-based PM mass and PM 

number standards discussed above, this 

is based on the measurement of nvPM 

only, not total PM emissions. 

To determine compliance with the 

proposed PM mass concentration 

standard, the maximum nvPM mass 

concentration [mg/m3] would be 

obtained from measurement at sufficient 

thrust settings such that the emission 

maximum can be determined. The 

maximum value would then be 

converted to a characteristic level in 

accordance with the procedures in 

ICAO Annex 16, Volume II, Appendix 6. 

The resultant characteristic level must 

not exceed the regulatory level 

determined from the following formula: 

Engines certificated under the new 

PM mass concentration standard would 

not need to certify smoke number values 

and would not be subject to in-use 

smoke standards. It is important to note 

that other smoke number standards 

remain in effect for in-production 

aircraft turbofan and turbojet engines at 

or below 26.7 kN rated output and for 

in-production turboprop engines. Also, 

the in-use smoke standards will 

continue to apply to some already 

manufactured aircraft engines that were 

certified to smoke number standards. 

2. Graphical Representation of nvPM 

Mass Concentration Numerical 

Emission Limit 

Figure IV–3 shows how the proposed 

nvPM mass concentration emission 

limits compare to known in-production 

engines. Data shown in this figure is 

from the ICAO Engine Emissions 

Databank EEDB).92


khammond on DSKJM1Z7X2PROD with PROPOSALS3EP03FE22.035</GPH>

Equation IV-5 
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6341 

D. Test and Measurement Procedures 

1. Aircraft Engine PM Emissions Metrics 

When developing the PM standards, 

ICAO looked at three different methods 

of measuring the amount of PM emitted. 

The first is PM mass, or a measure of the 

total weight of the particles produced 

over the test cycle. This is how the EPA 

has historically measured PM emissions 

subject to standards for other sectors. 

Second, ICAO considered PM number, 

or the number of particles produced by 

the engine over the test cycle. These are 

two different methods of measuring the 

same pollutant, PM, but each provides 

valuable information. Third, ICAO 

developed PM mass concentration 

standards, as an alternative to the 

existing visibility standards based on 

smoke. 

The EPA proposes to incorporate by 

reference the metrics agreed at ICAO 

and incorporated into Annex 16 Volume 

II, to measure PM mass (Equation IV–6) 

and PM number (Equation IV–7). These 

metrics are based on a measurement of 

the nvPM emissions, as measured at the 

instrument, over the LTO cycle and is 

normalized by the rated output of the 

engine (rO). 

The EPA proposes the PM mass 

concentration standard be based on the 

maximum mass concentration, in 

micrograms per meter cubed, produced 

by the engine at any thrust setting. 

Regulatory compliance with the 

emissions standards is based on the 

product of Equation IV–6 or Equation 


khammond on DSKJM1Z7X2PROD with PROPOSALS3EP03FE22.036</GPH> EP03FE22.037</GPH>

10000 

9000 

8000 

m 

1= 1000 

} 

§ 6000 

:;::; 

~ ..... 

C: 

~ C: 

0 

u 

~ 4000 ro 

2 

2 

Ci.. 

> C: 

3000 

2000 

1000 

0 

• 

0 

nvPM Mass Concentration vs. 

rrent Produ on E n 

100 200 

Output 

e Engine Test Data 1-,.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,"",,,1 

- Mass Cone. Std 

400 500 600 

Figure IV-3 - nvPM Mass Concentration Standard 

Equation IV-6 

Equation IV-7 
6342 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

93 ‘‘E–31 Committee was formed to develop and 

maintain cognizance of standards for measurement 

of emissions from aircraft powerplants and to 

promote a rational and uniform approach to the 

measurement of emissions form aircraft engines and 

combustion systems to support the practical 

assessment of the industry. The E–31 Committee, in 

its operation uses an Executive Committee, 

Membership Panel, Subcommittees and working 

technical panels as required to achieve its 

objectives.’’ 

(See https://www.sae.org/works/ 

committeeHome./do?comtID=TEAE31, last accessed 

November 15, 2021). 94All 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. 95 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017, III–4–2. 

Available at https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). The ICAO Annex 16 Volume II is found 

on page 17 of the ICAO Products & Services Catalog, 

English Edition of the 2021 catalog, and it is 

copyright protected; Order No. AN16–2. The ICAO 

Annex 16, Volume II, Fourth Edition, includes 

Amendment 10 of January 1, 2021. Amendment 10 

is also found on page 17 of this ICAO catalog, and 

it is copyright protected; Order No. AN 16–2/E/12. 

IV–7 or mass concentration divided by 

a correction factor in Table IV–2, to 

obtain the characteristic level that is 

used to determine compliance with 

emissions standards (see IV.D.4 below). 

2. Test Procedure 

The emission test and measurement 

procedures adopted by ICAO were 

produced in conjunction with the 

Society of Automotive Engineers (SAE) 

E–31 Aircraft Exhaust Emissions 

Measurement Committee.93 These 

procedures were developed in SAE E– 

31 in close consultation between 

government and industry, and 

subsequently they were adopted by 

ICAO and incorporated into ICAO 

Annex 16, Volume II. 

These procedures build off the 

existing aircraft engine measurement 

system for gaseous pollutants. At least 3 

engine tests need to be conducted to 

determine the emissions rates. These 

tests can be conducted on a single 

engine or multiple engines.94 A 

representative sample of the engine 

exhaust is sampled at the engine 

exhaust exit. The exhaust then travels 

through a heated sample line where it 

is diluted and kept at a constant 

temperature prior to reaching the 

measurement instruments. 

The methodology for measuring PM 

from aircraft engines differs from other 

test procedures for mobile source PM2.5

standards in two ways. First, as 

discussed above, the procedure is 

designed to measure only the 

nonvolatile component of PM. The 

measurement of volatile PM is very 

dependent on the environment where it 

is measured. The practical development 

of a standardized method of measuring 

volatile PM has proved challenging. 

Therefore, the development of a 

procedure for nvPM was prioritized and 

the result is proposed here today. 

Second, the sample is measured 

continuously rather than being collected 

on a filter and measured after the test. 

This approach was taken primarily for 

the practical reasons that, due to high 

dilution rates leading to relatively low 

concentrations of PM in the sample, 

collecting enough particulate on a filter 

to analyze has the potential to take 

hours. Given the high fuel flow rates of 

these engines, such lengthy test modes 

would be very expensive. Additionally, 

because of the high volume of air 

required to run a jet engine and the 

extreme engine exhaust temperatures, it 

is not possible to collect the full exhaust 

stream in a controlled manner as is done 

for other mobile source PM2.5

measurements. 

Included in the proposed procedures, 

to be incorporated by reference, are 

measurement system specifications and 

requirements, instrument specifications 

and calibration requirements, fuel 

specifications, and corrections for fuel 

composition, dilution, and 

thermophoretic losses in the collection 

part of the sampling system. 

To create a uniform sampling system 

design that works across gas turbine 

engine testing facilities, the test 

procedure calls for a 35-meter sample 

line. This results in a significant portion 

of the PM being lost in the sample lines, 

on the order of 50 percent for PM mass 

and 90 percent for PM number. These 

particle losses in the sampling system 

are not corrected for in the regulatory 

compliance levels (standards). 

Compliance with the standard is based 

on the measurement at the instruments 

rather than the exit plane of the engine 

(instruments are 35 meters from engine 

exit). This is due to the lack of 

robustness of the sampling system 

particle loss correction methodology 

and that a more stringent standard at the 

instrument will lead to a reduction in 

the nvPM emissions at the engine exit 

plane. A correction methodology has 

been developed to better estimate the 

actual PM emitted into the atmosphere. 

This correction is described below in 

Section V.A.2. 

3. Test Duty Cycles 

Mass and number PM emissions are 

proposed to be measured over the 

Landing and Take-Off (LTO) cycle 

shown in Table IV–1. This is the same 

duty cycle used today to measure 

gaseous emissions from aircraft engines 

and is intended to represent operations 

and flight under an altitude of 3,000 feet 

near an airport. Due to challenges in 

measuring at these exact conditions and 

atmospheric and fuel corrections that 

need to be applied after testing; it is not 

necessary to measure exactly at these 

points. Emissions rates for each mode 

can be calculated by testing the 

engine(s) over a sufficient range of 

thrust settings such that the emission 

rates at each condition in Table IV–1 

can be determined. 

TABLE IV–1—LANDING AND TAKE-OFF CYCLE THRUST SETTINGS AND TIME IN MODE 95

LTO operating mode Thrust setting 

Percent rO 

Time in 

operating 

mode 

(minutes) 

Take-off .................................................................................................................................................................... 100 0.7 

Climb ........................................................................................................................................................................ 85 2.2 

Approach .................................................................................................................................................................. 30 4.0 

Taxi/ground idle ....................................................................................................................................................... 7 26.0 

The existing smoke number standard 

was adopted to reduce the visible smoke 

emitted from aircraft engines. Smoke 

number has been determined by 

measuring the visibility or opacity of a 

filter after soot has been collected upon 

it during the test procedure. Another 

means of measuring this visibility is by 

direct measurement of the particulate 

matter mass concentration. By 

measuring visibility based on mass 

concentration rather than smoke 


khammond on DSKJM1Z7X2PROD with PROPOSALS3
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6343 

96 ICAO, 2017: Aircraft Engine Emissions, 

International Standards and Recommended 

Practices, Environmental Protection, Annex 16, 

Volume II, Fourth Edition, July 2017, App 6–2pp. 

Available at https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). The ICAO Annex 16 Volume II is found 

on page 17 of the ICAO Products & Services Catalog, 

English Edition of the 2021 catalog, and it is 

copyright protected; Order No. AN16–2. The ICAO 

Annex 16, Volume II, Fourth Edition, includes 

Amendment 10 of January 1, 2021. Amendment 10 

is also found on page 17 of this ICAO catalog, and 

it is copyright protected; Order No. AN 16–2/E/12. 

number, the number of tests needed can 

be reduced, and mass concentration 

data can be collected concurrently with 

other PM measurements. Like the 

existing smoke standard, the proposed 

PM mass concentration standard would 

be based on the maximum value at any 

thrust setting. The engine(s) would be 

tested over a sufficient range of thrust 

settings that the maximum can be 

determined. This maximum could be at 

any thrust setting and is not limited to 

the LTO thrust points. 

We are proposing to incorporate by 

reference ICAO’s International 

Standards and Recommended Practices 

for aircraft engine PM testing and 

certification—ICAO Annex 16, Volume 

II. 

4. Characteristic Level 

Like existing gaseous standards, 

compliance with the PM standards is 

proposed to be determined based on the 

characteristic level of the engine. The 

characteristic level is a statistical 

method of accounting for engine-toengine variation in the measurement 

based on the number of engines tested. 

A minimum of 3 engine emissions tests 

is needed to determine the engine type’s 

emissions rates for compliance with 

emissions standards. The more engines 

that are used for testing increases the 

confidence that the emissions rate 

measured is from a typical engine rather 

than a high or low engine. 

Table IV–2 below is reproduced from 

Annex 16 Volume II Appendix 6 Table 

A6–1 and shows how these factors 

change based on the number of engines 

tested. As the number of engines tested 

increases, the factor also increases 

resulting in a smaller adjustment and 

reflecting the increased confidence that 

the emissions rate is reflective of the 

average engine off the production line. 

In this way, there is an incentive to test 

more engines to reduce the 

characteristic adjustment while also 

increasing confidence that the measured 

emissions rate is representative of the 

typical production engine. 

TABLE IV–2—FACTORS TO DETERMINE CHARACTERISTIC VALUES 96

Number of engines 

tested (i) CO HC NOX SN nvPM mass 

concentration 

nvPM LTO 

mass 

nvPM LTO 

number 

1 ................................... 0.814 7 0.649 3 0.862 7 0.776 9 0.776 9 0.719 4 0.719 4 

2 ................................... 0.877 7 0.768 5 0.909 4 0.852 7 0.852 7 0.814 8 0.814 8 

3 ................................... 0.924 6 0.857 2 0.944 1 0.909 1 0.909 1 0.885 8 0.885 8 

4 ................................... 0.934 7 0.876 4 0.951 6 0.921 3 0.921 3 0.901 1 0.901 1 

5 ................................... 0.941 6 0.889 4 0.956 7 0.929 6 0.929 6 0.911 6 0.911 6 

6 ................................... 0.946 7 0.899 0 0.960 5 0.935 8 0.935 8 0.919 3 0.919 3 

7 ................................... 0.950 6 0.906 5 0.963 4 0.940 5 0.940 5 0.925 2 0.925 2 

8 ................................... 0.953 8 0.912 6 0.965 8 0.944 4 0.944 4 0.930 1 0.930 1 

9 ................................... 0.956 5 0.917 6 0.967 7 0.947 6 0.947 6 0.934 1 0.934 1 

10 ................................. 0.958 7 0.921 8 0.969 4 0.950 2 0.950 2 0.937 5 0.937 5 

more than 10 ................ 1–0.13059/√i 1–0.24724/√i 1–0.09678/√i 1–0.15736/√i 1–0.15736/√i 1–0.19778/√i 1–0.19778/√i 

For PM mass and PM number, the 

characteristic level would be based on 

the mean of all engines tested, and 

appropriately corrected, divided by the 

factor corresponding to the number of 

engine tests performed in Table IV–1. 

For PM mass concentration, the 

characteristic level would be based on 

the mean of the maximum values of all 

engines tested, and appropriately 

corrected, divided by the factor 

corresponding to the number of engine 

tests performed in Table IV–2. 

For example, an engine type where 

three measurements were obtained from 

the same engine has an nvPM mass 

metric value of 100 mg/kN (mean metric 

value of all engine tests). The nvPM 

LTO Mass factor (or nvPM mass 

characteristic factor) from Table IV–2 for 

three engines is 0.7194. The metric 

value, with applicable corrections 

applied, is then divided by the factor to 

obtain the characteristic level of the 

engine. Therefore, the resulting 

characteristic level for this engine type, 

to determine compliance with the nvPM 

mass standard is 139.005mg/kN. If 

instead three engines are each tested 

once, the characteristic factor would be 

0.8858 and the nvPM mass 

characteristic level to determine 

compliance with the standard would be 

112.892 mg/kN. 

An engine type’s characteristic level 

can also be further improved by testing 

additional engines. For example, if 10 

separate engines were tested of the same 

type, the nvPM mass characteristic 

factor becomes 0.9375. The resulting 

characteristic level (assuming the 

average nvPM mass metric value 

remains 100 mg/kN) would be 106.667 

mg/kN. This approach could be used if 

an engine exceeds the standard at the 

time it is initially tested or there is a 

desire to increase the margin to the 

standard for whatever reason. Table IV– 

3 shows these three different examples 

for nvPM LTO Mass. 

TABLE IV–3—IMPACT OF THE NUMBER OF ENGINES TESTED ON RESULTING CHARACTERISTIC LEVEL

Number of engines tested 

Number of 

tests per 

engine 

Measured 

nvPM LTO 

mass 

(mg/kN) 

Characteristic 

factor 

Characteristic 

level 

(mg/kN) 

1 ....................................................................................................................... 3 100 0.7194 139.005 

3 ....................................................................................................................... 1 100 0.8858 112.892 

10 ..................................................................................................................... 1 100 0.9375 106.667 


khammond on DSKJM1Z7X2PROD with PROPOSALS3
6344 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

97 77 FR 36342, June 18, 2012. 

98 83 FR 44621, August 31, 2018. 

99U.S. EPA, Aircraft Engines—Supplemental 

Information Related to Exhaust Emissions 

(Renewal), OMB Control Number 2060–0680, ICR 

Reference Number 201809–2060–08, December 17, 

2018. Available at https://www.reginfo.gov/public/ 

do/PRAViewICR?ref_nbr=201809-2060-008, last 

accessed November 15, 2021. 

100 86 FR 24614, May 7, 2021. 

101 Documentation and Public comments are 

available at: https://www.regulations.gov/docket/ 

EPA-HQ-OAR-2016-0546, last accessed November 

15, 2021. 

We are proposing to incorporate by 

reference ICAO’s International 

Standards and Recommended Practices 

for correcting engine measurements to 

characteristic value—ICAO Annex 16, 

Volume II, Appendix 6. 

5. Derivative Engines for Emissions 

Certification Purposes 

Aircraft engines can remain in 

production for many years and be 

subject to numerous modifications 

during its production life. As part of the 

certification process for any change, the 

type certificate holder will need to show 

that the change does not impact the 

engine emissions. While some of these 

changes could impact engine emissions 

rates, many of them will not. To 

simplify the certification process and 

reduce burden on both type certificate 

holder and certification authorities, 

ICAO developed criteria to determine 

whether there has been an emissions 

change that requires new testing. Such 

criteria already exist for gaseous and 

smoke standards. 

ICAO recommends that if the 

characteristic level for an engine was 

type certificated at a level that is at or 

above 80 percent of the PM mass, PM 

number, or PM mass concentration 

standard, the type certificate holder 

would be required to test the proposed 

derivative engine. If the engine is below 

80 percent of the standard, engineering 

analysis can be used to determine new 

emission rates for the proposed 

derivative engines. Today, the EPA 

proposes to adopt these ICAO 

provisions. 

Subsequently, ICAO evaluated the 

measurement uncertainty to develop 

criteria for determining if a proposed 

derivative engine’s emissions are similar 

to the previously certificated engine’s 

emissions, which are described below. 

Today, the EPA proposes to adopt these 

ICAO criteria. 

For PM Mass measurements described 

above in Section IV.A, the following 

values would apply: 

• 80 mg/kN if the characteristic level 

for nvPMmass emissions is below 400 

mg/kN. 

• ±20% of the characteristic level if 

the characteristic level for nvPMmass

emissions is greater than or equal to 400 

mg/kN. 

For PM number measurements, 

described above in Section IV.B, the 

following values would apply: 

• 4 × 10∧14 particles/kN if the 

characteristic level for nvPMnum

emissions is below 2 × 10∧15 particles/ 

kN. 

• ±20% of the characteristic level if 

the characteristic level for nvPMnum

emissions is greater than or equal to 2 

× 10∧15 particles/kN. 

For PM mass concentration 

measurements described above in 

Section IV.C, the following values 

would apply: 

• ±200 mg/m∧3 if the characteristic 

level of maximum nvPM mass 

concentration is below 1,000 mg/m∧3. 

• ±20% of the characteristic level if 

the characteristic level for maximum 

nvPM mass concentration is at or above 

1,000 mg/m∧3. 

If a type certificate holder can 

demonstrate that the engine’s emissions 

are within these ranges, then new 

emissions rates would not need to be 

developed and the proposed derivative 

engine for emissions certification 

purposes could keep the existing 

emissions rates. 

If the engine is not determined to be 

a derivative engine for emissions 

certification purposes, the certificate 

holder would need to certify the new 

emission rates for the engine. 

E. Annual Reporting Requirement 

In 2012, the EPA adopted an annual 

reporting requirement as part of a 

rulemaking to adopt updated aircraft 

engine NOX standards.97 This provision, 

adopted into 40 CFR 87.42, requires the 

manufacturers of covered engines to 

annually report data to the EPA which 

includes information on engine 

identification and characteristics, 

emissions data for all regulated 

pollutants, and production volumes. In 

2018, the EPA issued an information 

collection request (ICR) which renewed 

the existing ICR and added PM 

information to the list of required 

data.98 99 However, that 2018 ICR was 

not part of a rulemaking effort, and the 

new PM reporting requirements were 

not incorporated into the CFR at that 

time. Further, that 2018 ICR is currently 

being renewed (in an action separate 

from this proposal), and the EPA is 

proposing as part of that effort to add 

some additional data elements to the 

ICR (specifically, the emission indices 

for HC, CO, and NOX at each mode of 

the LTO cycle).100 101 The EPA is now 

proposing to formally incorporate all 

aspects of that ICR, as proposed to be 

renewed, into the CFR in the proposed 

section 1031.150. It is important to note 

that the incorporation of the PM 

reporting requirements into the CFR 

would not create a new requirement for 

the manufacturers of aircraft engines. 

Rather, it would simply incorporate the 

existing reporting requirements (as 

proposed to be amended and renewed 

in a separate action) into the CFR for 

ease of use by having all the reporting 

requirements readily available in the 

CFR. 

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 standardsetting actions. The information enables 

the EPA to further understand the 

characteristics of aircraft engines that 

are subject to emission standards—and 

engines proposed to be subject to the 

PM emission standards—and engines 

impact on emission inventories. In 

addition, the information helps the EPA 

set appropriate and achievable emission 

standards and related requirements for 

aircraft engines. Annually updated 

information helps in assessing 

technology trends and their impacts on 

national emissions inventories. Also, it 

assists the EPA to stay abreast of 

developments in the aircraft engine 

industry. 

As discussed in Section VII, the EPA 

is proposing to migrate the existing 40 

CFR part 87 regulatory text to a new 40 

CFR part 1031. Part of that effort 

includes clarifying portions of the 

regulatory text for ease of use. In the 

existing 40 CFR 87.42(c)(6), the 

regulatory text does not specifically 

spell out some required data, but 

instead relies on incorporation by 

reference for a detailed listing of 

required items. 40 CFR 87.42(c)(6) 

references the data reporting provisions 

in ICAO’s Annex 16, Volume II and lists 

the data from this Annex that is not 

required by the EPA’s reporting 

requirement. For future ease of use, the 

EPA is proposing in the new 40 CFR 

1031.150 to explicitly list all the 

required items rather than continuing 

the incorporation by reference approach 

in the existing reporting regulations. 

The reader is encouraged to consult the 

proposed 40 CFR 1031.150 text for a 

complete list of the required reporting 

items. However, as previously 

mentioned, this list contains all the 

currently required items as well as the 

HC, CO and NOX emission indices as 

proposed in the separate ICR renewal 

action. Finally, the EPA is proposing to 

incorporate by reference Appendix 8 of 


khammond on DSKJM1Z7X2PROD with PROPOSALS3
Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 6345 

102A local air quality ‘‘. . . emissions inventory 

for aircraft focuses on the emission characteristics 

of this source relative to the vertical column of air 

that ultimately affects ground level pollutant 

concentrations. This portion of the atmosphere, 

which begins at the earth’s surface and is simulated 

in air quality models, is often referred to as the 

mixing zone’’ or mixing height. (See page 137.) The 

air in this mixing height is completely mixed and 

pollutants emitted anywhere within it will be 

carried down to ground level. (See page 143.) ‘‘The 

aircraft operations of interest within the [mixing 

height] are defined as the [LTO] cycle.’’ (See page 

137.) The default mixing height in the U.S. is 3,000 

feet. (EPA, 1992: Procedures for Emission Inventory 

Preparation—Volume IV: Mobile Sources, EPA420– 

R–92–009. Available at https://nepis.epa.gov (last 

accessed June 23, 2021). 

103 ICAO: 2019, ICAO Environmental Report, 

Available at https://www.icao.int/environmentalprotection/Documents/ICAO-ENV-Repor/t2019-F1- 

WEB%20(1).pdf (last accessed on November 15, 

2021,2021). See pages 100 and 101 for a description 

of non-volatile PM and volatile PM. 

‘‘At the engine exhaust, particulate emissions 

mainly consist of ultrafine soot or black carbon 

emissions. Such particles are called ‘‘non-volatile’’ 

(nvPM). They are present at the high temperatures 

at the engine exhaust and they do not change in 

mass or number as they mix and dilute in the 

exhaust plume near the aircraft. The geometric 

mean diameter of these particles is much smaller 

than PM2.5 (geometric mean diameter of 2.5 

Microns) and ranges roughly from 15nm to 60nm 

(0.06 Microns). These are classified as ultrafine 

particles (UFP).’’ (See page 100.) ‘‘The new ICAO 

standard is a measure to control the ultrafine nonvolatile particulate matter emissions emitted at the 

engine exit . . .’’ (See page 101.) 

‘‘Additionally, gaseous emissions from engines 

can also condense to produce new particles (i.e., 

volatile particulate matter—vPM), or coat the 

emitted soot particles. Gaseous emissions species 

react chemically with ambient chemical 

constituents in the atmosphere to produce the so 

called secondary particulate matter. Volatile 

particulate matter is dependent on these gaseous 

precursor emissions. While these precursors are 

controlled by gaseous emission certification and the 

fuel composition (e.g., sulfur content) for aircraft 

gas turbine engines, the volatile particulate matter 

is also dependent on the ambient air background 

composition.’’ (See pages 100 and 101.) 

104European Monitoring and Evaluation 

Programme/European Environment Agency, Air 

Pollutant Emission Inventory Guidebook 2019; 

Available at https://www.eea.europa.eu/themes/air/ 

air-pollution-sources-1/emep-eea-air-/pollutant-/

emission-/inventory-guidebook/emep (last accessed 

June 26, 2021). 

105SAE Aerospace Information Reports, AIR5715, 

Procedure for the Calculation of Aircraft Emissions, 

2009, SAE International. 

106Wayson RL, Fleming GG, Iovinelli R. 

Methodology to Estimate Particulate Matter 

Emissions from Certified Commercial Aircraft 

Engines. J Air Waste Management Assoc. 2009 Jan 

1; 59(1). 

107 In this context, organics refers to hydrocarbons 

in the exhaust that coat on existing particles or 

condense to form new particles after the engine 

exit. 

Annex 16, Volume II, which outlines 

procedures used to estimate 

measurement system losses, which are a 

required element of the proposed 

reporting provisions. 

V. Aggregate PM Inventory Impacts 

The number of aircraft landings and 

takeoffs (LTO) affects PM emissions that 

contribute to the local air quality near 

airports. The LTO emissions are defined 

as emissions between ground level and 

an altitude of about 3,000 feet. They are 

composed of emissions during 

departure operations (from taxi-out 

movement from gate to runway, aircraft 

take-off run and climb-out to 3,000 feet), 

and during arrival operations (emissions 

from approach at or below 3,000 feet 

down to landing on the ground and taxiin from runway to gate). These LTO 

emissions directly affect the ground 

level air quality at the vicinity of the 

airport since they are within the local 

mixing height. Depending on the 

meteorological conditions, the 

emissions will be mixed with ambient 

air down to ground level, dispersed, and 

transported to areas downwind from the 

airport with elevated concentration 

levels.102

As described earlier in Section III, 

aircraft PM emissions are composed of 

both volatile and nonvolatile PM 

components.103 Starting from an air and 

fuel mixture of 16.3 percent oxygen 

(O2), 75.2 percent nitrogen (N2), and 8.5 

percent fuel, an aircraft engine yields 

combustion products of 27.6 percent 

water (H2O), 72 percent carbon dioxide 

(CO2), and ∼0.02 percent sulfur oxide 

(SOX) with only 0.4 percent incomplete 

residual products which can be broken 

down to 84 percent nitrogen oxide 

(NOX), 11.8 percent carbon monoxide 

(CO), 4 percent unburned hydrocarbons 

(UHC), 0.1 percent PM and trace amount 

of other products.104 Although the PM 

emissions are a small fraction of total 

engine exhaust, the composition and 

morphology of PM are complex and 

dynamic. While the proposed emission 

test procedures focus only on measuring 

nonvolatile PM (black carbon), our 

emissions inventory includes estimates 

for volatile PM (organic, lubrication oil 

residues and sulfuric acid) as well. 

A. Aircraft Engine PM Emissions for 

Modeling 

To quantify the aircraft PM emissions 

for the purposes of developing or 

modeling an emissions inventory for 

this proposed rulemaking (for an 

inventory in the year 2017), we used an 

approximation method as described in 

Section V.A.1. For future emission 

inventories, this approximation method 

will not be needed for newly 

manufactured engines which will have 

measured PM emission indices (EIs) 

going forward. However, to accurately 

estimate the nvPM emissions at the 

engine exit for emission inventory 

purposes, loss correction factors for 

nvPM mass and nvPM number will 

need to be applied to the measured PM 

EIs due to particle losses in the nvPM 

sampling and measurement system. An 

improved approximation method as 

described in Section V.A.3 is expected 

to be used for modeling PM emissions 

of in-service engines that do not have 

measured PM data. For the final 

rulemaking, we expect to develop an 

updated PM emissions inventory based 

on available measured PM EIs data with 

loss correction and the improved 

approximation method for engines 

without measured PM EIs. 

1. Baseline PM Emission Indices 

Measured PM data was not available 

to calculate the 2017 inventory. Thus, to 

calculate the baseline aircraft engine PM 

emissions, we used the FOA3 (First 

Order Approximation Version 3.0) 

method defined in the SAE Aerospace 

Information Reports, AIR5715.105 For 

non-volatile PM mass, the FOA3 

method is based on an empirical 

correlation of Smoke Number (SN) 

values and the non-volatile PM (nvPM) 

mass concentrations of aircraft engines. 

The nvPM mass concentration (g/m3) 

derived from SN can then be converted 

into an nvPM mass emission index (EI) 

in gram of nvPM per kg fuel using the 

method developed by Wayson et al,106

based on a set of empirically determined 

Air Fuel Ratios (AFR) and engine 

volumetric flow rates at the four ICAO 

LTO thrust settings (see Table IV–1). 

Subsequently, the nvPM mass EI can be 

used to calculate the nvPM mass for the 

four LTO modes with engine fuel flow 

rate and time-in-mode information. As 

the name suggests, the FOA3 method is 

a rough estimate, and it is only for 

nvPM mass. 

In addition, as described earlier 

(Sections III.A and IV), volatile PM and 

nvPM together make up total PM. The 

FOA3 method for volatile PM is based 

on the jet fuel organics 107 and sulfur 

content. Since the total PM inventory is 

the emissions inventory we are 

estimating for this proposed rulemaking, 

we are including the volatile PM 

emission estimates from the FOA3 

method in our emission inventory. 

2. Measured nvPM EIs for Inventory 

Modeling 

The measurement and reporting of 

engine EIs will improve the 

development of future engine emission 

inventories. As mentioned in Section 

IV, the regulatory compliance level is 

based on the amount of particulate that 

is directly measured by the instruments. 

The test procedures specify a sampling 

line that can be up to 35 meters long. 

This length results in significant particle 

loss in the measurement system, on the 


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6346 Federal Register / Vol. 87, No. 23 / Thursday, February 3, 2022 / Proposed Rules 

108Annex 16 Vol. II Appendix 8 Note 2. 

109 ICAO: Second edition, 2020: Doc 9889, 

Airport Air Quality Manual. Order Number 9889. 

See Attachment D to Appendix 1 of Chapter 3. Doc 

9889 can be ordered from ICAO website: https://

store.icao.int/en/airport-air-/quality-manual/-doc9889 (last accessed June 28, 2021). 

110Based on the newly available measurement 

data and inputs from technical experts in SAE E– 

31 Aircraft Exhaust Emissions Measurement 

Committee, CAEP has determined that a set of fixed 

geometric mean diameters (GMDs) of 20/20/40/40 

nanometers for the four LTO modes (idle-taxi/ 

approach/climbout/take-off) fits the data the best. 

Along with the assumptions of a log-normal size 

distribution, a geometric standard deviation of 1.8, 

and an effective density of 1,000 kg/m∧3 for the 

exhaust plume at the engine exit plane, nvPM mass 

EI and nvPM number EI of LTO mode k can be 

converted to each other. 

111 2017 National Emissions Inventory: Aviation 

Component, Eastern Research Group, Inc., July 25, 

2019, EPA Contract No. EP–C–17–011, Work Order 

No. 2–19. 

112See section 3.2 for airports and aircraft related 

emissions in the Technical Supporting Document 

for the 2017 National Emissions Inventory, January 

2021 Updated Release; https://www.epa.gov/sites/ 

production/files/2021-02/documents/nei2017_tsd_

full_jan2021.pdf. 

113https://www.epa.gov/air-emissions/- 

inventories/2017-/national-emissions-/inventorynei-data. 

114Air 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. 

115Title 14—Code of Federal Regulations—Part 

241 Uniform System of Accounts and Reports for 

Large Certificated Air Carriers. T–100 Segment (All 

Carriers)—Published Online by Bureau of 

Transportation Statistics. https://

www.transtats.bts.gov/Fields.asp?Table_ID=293. 

Accessed May 9, 2018. 

116Federal Aviation Administration. Terminal 

Area Forecast (TAF). https://aspm.faa.gov/main/ 

taf.asp. Accessed April 21, 2018. 

117Federal Aviation Administration. ATADS: 

Airport Operations: Standard Report. https://

aspm.faa.gov/opsnet/sys/Airport.asp. Accessed 

May 23, 2018. 

118Federal Aviation Administration. 2009. 

Airport Master Record Form 5010. Published by 

GCR & Associates. https://www.gcr1.com/5010WEB/ 

. Accessed May 21, 2009. 

119The rationale for the use of multiple FAA 

activity databases is described in the 2017 NEI 

report (2017 National Emissions Inventory: 

Aviation Component, Eastern Research Group, Inc., 

July 25, 2019, EPA Contract No. EP–C–17–011, 

Work Order No. 2–19. See section 3.2 for airports 

and aircraft related emissions in the Technical 

Supporting Document for the 2017 National 

Emissions Inventory, January 2021 Updated 

Release; https://www.epa.gov/sites/production/ 

files/2021-02/documents/nei2017_tsd_full_

jan2021.pdf, last accessed June 26, 2021.) 

120AEDT is a software system that models aircraft 

performance in space and time to estimate fuel 

consumption, emissions, noise, and air quality 

consequences. It is available at https://aedt.faa.gov/ 

(last accessed on June 26, 2021). 

121 Ibid. 

order of 50 percent for nvPM mass and 

90 percent for nvPM number.108 Further 

the particle loss is size dependent, and 

thus the losses will be dependent on the 

engine operating condition (e.g., idle vs 

take-off thrust), engine combustor 

design, and technology. To assess the 

emissions contribution of aircraft 

engines for inventory and modeling 

purposes, and subsequently for human 

health and environmental effects, it is 

necessary to know the emissions rate at 

the engine exit. Thus, the measured PM 

mass and PM number values must be 

corrected for system losses to determine 

the engine exit emissions rate. 

The EPA led the effort within the SAE 

E–31 committee to develop the 

methodology to correct for system 

losses. This effort at E–31 resulted in the 

development and publication of AIR 

6504 and ARP 6481 describing how to 

correct for system losses. ICAO has 

incorporated this same procedure into 

Annex 16 Vol. II Appendix 8. 

The engine exit emissions rate, which 

is corrected for system losses, is specific 

to each measurement system and to 

each engine. The calculation is an 

iterative function based upon the 

measured nvPM mass and nvPM 

number values and the geometry of the 

measurement system. Manufacturers 

provide the corrected emissions values 

to the ICAO EDB and to the EPA. 

When calculating emissions 

inventories, these corrected EIs will be 

used rather than the values used to 

show compliance with emission 

standards. These measured EIs are only 

for the nonvolatile component of PM, 

and an approximation method will still 

be required for quantifying the volatile 

PM inventory. 

3. Improvements to Calculated EIs 

The new version of the approximation 

method, known as FOA4, has been 

developed by CAEP to improve nvPM 

mass estimation and to extend the 

methodology to nvPM number based on 

the newly available PM measurement 

data.109 Since PM mass and PM number 

are two different measurement metrics 

of the same pollutant, PM, they can be 

converted to each other if the size and 

density distribution of the pollutant can 

be characterized.110 FOA4 was not used 

in the baseline emission rates for this 

proposed rulemaking. 

The calculation of volatile PM has not 

changed between FOA3 and FOA4 

because no improved data or method 

has become available to inform 

improvements. 

B. Baseline PM Emission Inventory 

The baseline PM emissions inventory 

used for this proposed rule is from the 

aviation portion of EPA’s 2017 National 

Emissions Inventory (NEI).111 112 113 The 

NEI is compiled by EPA triennially 

based on comprehensive emissions data 

for criteria pollutants and hazardous air 

pollutants (HAPs) for mobile, point, and 

nonpoint sources. The mobile sources 

include aviation, marine, railroad, onroad vehicles, and nonroad engines. As 

described earlier in Section V.A, the 

aircraft emission estimates in this 2017 

NEI (or the baseline PM emissions 

inventory) are based on the FOA instead 

of measured PM emissions data from 

aircraft engines proposed to be regulated 

by this rulemaking. For the final 

rulemaking, we anticipate potentially 

having an updated baseline PM 

emissions inventory based on measured 

data from numerous in-production 

engines (we would likely have PM data 

for nearly all in-production engines 

proposed to be regulated by this 

rulemaking). 

The aviation emissions developed for 

the NEI include emissions associated 

with airport activities in commercial 

aircraft, air taxi aircraft,114 general 

aviation aircraft, military aircraft, 

auxiliary power units, and ground 

support equipment. All emissions from 

aircraft with gas turbine engines greater 

than 26.7 kN rated output from the 

aircraft categories described earlier, 

except military aircraft, are used in the 

emissions inventory for this proposed 

rule (which is a subset of the aviation 

emissions inventory). To estimate 

emissions, 2017 activity data by states 

were compiled and supplemented with 

publicly available FAA data. The FAA 

activity data included 2017 T–100 115

dataset, 2014 Terminal Area Forecast 

(TAF) 116 data, 2014 Air Traffic Activity 

Data System (ATADS) 117 data, and 2014 

Airport Master Record (form 5010) 118

data.119 The NEI used the FAA’s 

Aviation Environmental Design Tool 

(AEDT) 120 version 2d to estimate 

emissions for aircraft that were in the 

AEDT database. The NEI used a more 

general estimation methodology to 

account for emissions from aircraft 

types not available in AEDT by 

multiplying the reported activities by 

fleet-wide average emission factors of 

generic aircraft types (or by aircraft 

category—e.g., general aviation or air 

taxi).121

For aircraft PM contribution in 2017 

to total mobile PM emissions in 

counties and MSA’s for the top 25 

airports (inventories for aircraft with 

engines >26.7 kN), see Figure III–1 and 

Figure III–2 in Section III.E. 

As described earlier, the baseline 

emissions inventory is based on the 

total PM emissions, which includes 

both the nvPM and volatile PM 

components of total PM. The 2017 NEI 

does not provide inventories for these 

components of total PM. However, we 

estimate that nvPM is about 70 percent 


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122 ICAO: Second edition, 2020: Doc 9889, 

Airport Air Quality Manual. Order Number 9889. 

See Attachment D to Appendix 1 of Chapter 3. Doc 

9889 can be ordered from ICAO website: https://

store.icao.int/en/airport-air-/quality-manual-/doc9889 (last accessed June 28, 2021). 

123https://www.rolls-royce.com/products-andservices/civil-aerospace/future-products.aspx#/; 

last accessed on June 26, 2021. 

124https://aviationweek.com/mro/rolls-royce-/

considers-ultrafan-/development-pause; last 

accessed on June 26, 2021. 

(range 51 percent to 72 percent based on 

modal EIs of a sample engine) of the 

total PM.122 We intend to improve this 

estimate for the final rulemaking. 

Applying the nvPM percentage (or 

fraction) to the total fleet-wide baseline 

PM inventory, or the 2017 NEI PM 

inventory for aircraft with gas turbine 

engines greater than 26.7 kN, would 

better enable us to estimate the nvPM 

portion of the aircraft contribution to 

total mobile PM accordingly. 

C. Projected Reductions in PM 

Emissions 

Due to the technology-following 

nature of the PM standards, the 

proposed in-production and new type 

standards would not result in emission 

reductions below current levels of 

engine emissions. The proposed inproduction standards for both PM mass 

and PM number, which would be set at 

levels where all in-production engines 

meet the standards, would not affect any 

in-production engines as shown in 

Figure IV–1 and Figure IV–2. Thus, the 

proposed standards are not expected to 

produce any emission reductions, 

beyond the business-as-usual fleet turn 

over that would occur absent of the 

proposed standards. The EPA projects 

that all future new type engines would 

meet the proposed new type standards. 

There are a few in-production engines 

that do not meet the proposed new type 

standards, but since in-production 

engines would not be subject to these 

new type standards, engine 

manufacturers would not be required to 

make any improvements to these 

engines to meet the standards. 

Therefore, there would be no emission 

reductions from the proposed new type 

standards. 

Most of the in-production engines that 

do not meet the proposed new type 

standards are older engines that already 

have replacement in-production engines 

that would meet the proposed new type 

standards. There is only one newer inproduction engine (an engine that 

recently started being manufactured) 

that would not meet the proposed new 

type standards and does not currently 

have a replacement in-production 

engine. Market forces might drive the 

manufacturer of this in-production 

engine to make some improvements to 

meet the proposed new type standards, 

but even in this scenario, this 

manufacturer would still have the 

option to retest the engine and/or make 

minor adjustments or design 

modifications to improve the test result. 

The other option for this manufacturer 

would be to bring forward its next 

generation new type engine to the 

market a few years earlier than currently 

planned.123 124 Since the new type 

standards would not apply to the inproduction engines, this manufacturer 

could continue producing and selling its 

one in-production engine that does not 

meet the proposed new type standards. 

Further details on market forces are 

provided later in Section VI.A. In 

conclusion, when considering the 

proposed new type standards in the 

context of the in-production engines 

that already have a replacement engine 

or the one in-production engine that 

does not, there would be no emission 

reductions from the proposed new type 

standards. 

VI. Technological Feasibility and 

Economic Impacts 

As described earlier, we are proposing 

PM mass concentration, PM mass, and 

PM number standards that match 

ICAO’s standards. As discussed 

previously in Section V.C, for inproduction aircraft engines, the 2017 

ICAO PM maximum mass concentration 

standard and the 2020 ICAO PM mass 

and number standards are set at 

emission levels where all in-production 

engines meet these standards. Thus, 

there would not be costs or emission 

reductions associated with the proposed 

standards for in-production engines. For 

new type engines, the 2020 ICAO PM 

mass and number standards are set at 

more stringent emission levels 

compared to the PM mass and number 

standards for in-production engines, but 

nearly all in-production engines meet 

these new type standards. In addition, 

in-production engines would not be 

required to meet these new type 

standards. Only new type engines 

would need to comply with the new 

type standards. The EPA projects that 

all new type engines entering into 

service into the future will meet these 

PM mass and number standards. Thus, 

EPA expects that there would not be 

costs and emission reductions from the 

proposed standards for new type 

engines. In addition, following the final 

rulemaking for the PM standards, the 

FAA would issue a rulemaking to 

enforce compliance to these standards, 

and any anticipated certification costs 

for the PM standards would be 

accounted for in the FAA rulemaking. 

A. Market Considerations 

Aircraft and aircraft engines are sold 

around the world, and international 

aircraft emission standards help ensure 

the worldwide acceptability of these 

products. Aircraft and aircraft engine 

manufacturers make business decisions 

and respond to the international market 

by designing and building products that 

conform to ICAO’s international 

standards. However, ICAO’s standards 

need to be implemented domestically 

for products to prove such conformity. 

Domestic action through EPA 

rulemaking and subsequent FAA 

rulemaking enables U.S. manufacturers 

to obtain internationally recognized U.S. 

certification, which for the proposed PM 

standards would ensure type 

certification consistent with the 

requirements of the international PM 

emission standards. This is important, 

as compliance with the international 

standards (via U.S. type certification) is 

a critical consideration in aircraft 

manufacturer and airlines’ purchasing 

decisions. By implementing the 

requirements in the United States that 

align with ICAO standards, any question 

regarding the compliance of aircraft 

engines certificated in the United States 

would be removed. The proposed rule 

would facilitate the acceptance of U.S. 

aircraft engines by member States, 

aircraft manufacturers, and airlines 

around the world. Conversely, without 

this domestic action, U.S. aircraft engine 

manufacturers would be at a 

competitive disadvantage compared 

with their international competitors. 

In considering the aviation market, it 

is important to understand that the 

international PM emission standards 

were predicated on demonstrating 

ICAO’s concept of technological 

feasibility; i.e., that manufacturers have 

already developed or are developing 

improved technology that meets the 

ICAO PM standards, and that the new 

technology will be integrated in aircraft 

engines throughout the fleet in the time 

frame provided before the standards’ 

effective date. Therefore, the EPA 

projects that these proposed standards 

would impose no additional burden on 

manufacturers. 

B. Conceptual Framework for 

Technology 

The long-established ICAO/CAEP 

terms of reference were taken into 

account when deciding the international 

PM standards, principal among these 

being technical feasibility. For the ICAO 

PM standard setting, technical 

feasibility refers to refers to any 


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125TRL is a measure of Technology Readiness 

Level. CAEP has defined TRL8 as the ‘‘actual 

system completed and ‘flight qualified’ through test 

and demonstration.’’ TRL is a scale from 1 to 9, 

TRL1 is the conceptual principle, and TRL9 is the 

‘‘actual system ‘flight proven’ on operational 

flight.’’ The TRL scale was originally developed by 

NASA. ICF International, CO2 Analysis of CO2- 

Reducing Technologies for Aircraft, Final Report, 

EPA Contract Number EP–C–12–011, see page 40, 

March 17, 2015. 126 ICAO, 2019: Report of the Eleventh Meeting, 

Montreal, 4–15 February 2019, Committee on 

Aviation Environmental Protection, Document 

10126, CAEP11. It is found on page 26 of the 

English Edition of the ICAO Products & Services 

2021 Catalog and is copyright protected: Order No. 

10126. For purchase and available at: https://

www.icao.int/publications/catalogue/cat_2021_

en.pdf (last accessed November 15, 2021). The 

statement on technological feasibility is located in 

Appendix C of Agenda Item 3 of this report (see 

page 3C–4, paragraph 2.2). 

127 ICAO, 2019: Report of the Eleventh Meeting, 

Montreal, 4–15 February 2019, Committee on 

Aviation Environmental Protection, Document 

10126, CAEP11. It is found on page 26 of the 

English Edition of the ICAO Products & Services 

2021 Catalog and is copyright protected: Order No. 

10126. For purchase and available at: https://

www.icao.int/publications/catalogue/cat_2021_

en.pdf (last accessed November 15, 2021). The 

summary of technological feasibility and cost 

information is located in Appendix C to the report 

on Agenda Item 3 (starting on page 3C–1). 

128 Ibid. 

129 ICAO, 2019: Independent Expert Integrated 

Technology Goals Assessment and Review for 

Engines and Aircraft, Document 10127. It is found 

on page 32 of the English Edition of the ICAO 

Products & Services 2021 Catalog and is copyright 

protected; Order No. 10127. For purchase and 

available at: https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). 

130 Ibid. See page 8 of this document. 

131For lean-burn engines, ‘‘. . . enough air is 

introduced with the fuel from the injector so that 

it is never overall rich. In aviation combustors, the 

fuel is not premixed and pre-vaporized and in the 

microscopic region around each droplet, the 

mixture can be close to stoichiometric. However, 

the mixture remains lean throughout the combustor 

and temperature does not approach the 

stoichiometric value. . . . In a lean-burn 

combustor, the peak temperatures are not as high, 

so NOX is low.’’ (See pages 47 and 48.) From 

previous generation rich-burn to lean-burn 

technology, an order of magnitude improvement in 

nvPM mass and nvPM number is likely for the LTO 

cycle. (See pages 57 and 58.) 

For Rich-Quench-Lean (RQL) engines, ‘‘. . . the 

fuel first burns rich so there is little oxygen free to 

form NOX. Dilution air is introduced to take the 

mixture as quickly as possible through 

stoichiometric region (when it briefly gets very hot) 

to a cooler, lean state.’’ (See page 47.) Potentially, 

an order of magnitude improvement in nvPM mass 

and nvPM number could be achieved for the LTO 

cycle from previous generation rich-burn to 

advanced rich-burn combustor technology. (See 

pages 57 and 58.) 

ICAO, 2019: Independent Expert Integrated 

Technology Goals Assessment and Review for 

Engines and Aircraft, Document 10127. It is found 

on page 32 of the English Edition of the ICAO 

Products & Services 2021 Catalog and is copyright 

protected; Order No. 10127. For purchase and 

available at: https://www.icao.int/publications/ 

catalogue/cat_2021_en.pdf (last accessed November 

15, 2021). See pages, 47, 48, 57, and 58 of this 

document. 

132For example, the relatively small combustor 

space and section height of these engines creates 

constraints on the use of low NOX combustor 

concepts, which inherently require the availability 

of greater flow path cross-sectional area than 

conventional combustors. Also, fuel-staged 

combustors need more fuel injectors, and this need 

is not compatible with the relatively smaller total 

fuel flows of lower thrust engines. (Reductions in 

fuel flow per nozzle are difficult to attain without 

having clogging problems due to the small sizes of 

the fuel metering ports.) In addition, lower thrust 

engine combustors have an inherently greater liner 

surface-to combustion volume ratio, and this 

requires increased wall cooling air flow. Thus, less 

air will be available to obtain acceptable turbine 

inlet temperature distribution and for emissions 

control. U.S. EPA, 2012: Control of Air Pollution 

from Aircraft and Aircraft Engines; Emission 

Standards and Test Procedures; Final Rule, 77 FR 

36342, June 18, 2012. (See page 36353.) 

133 ICAO, 2019: Report of the Eleventh Meeting, 

Montreal, 4–15 February 2019, Committee on 

Aviation Environmental Protection, Document 

10126, CAEP11. It is found on page 26 of the 

English Edition of the ICAO Products & Services 

2021 Catalog and is copyright protected: Order No. 

10126. For purchase and available at: https://

www.icao.int/publications/catalogue/cat_2021_

en.pdf (last accessed November 15, 2021). See pages 

3C–17 to 3C–19 in Appendix C to the report on 

Agenda Item 3 (starting on page 3C–1). 

U.S. EPA, 2012: Control of Air Pollution from 

Aircraft and Aircraft Engines; Emission Standards 

and Test Procedures; Final Rule, 77 FR 36342, June 

18, 2012. (See pages 36375 and 36376.) 

technology demonstrated to be safe and 

airworthy proven to Technical 

Readiness Level 125 (TRL) 8 and 

available for application over a 

sufficient range of newly certificated 

aircraft.126 This means that the analysis 

that informed the international standard 

considered the emissions performance 

of aircraft engines assumed to be inproduction on the implementation date 

for the PM mass and number standards, 

January 1, 2023.127 The analysis 

included the current in-production fleet 

and engines scheduled for entry into the 

fleet by this date. (ICAO/CAEP’s 

analysis was completed in 2018 and 

considered at the February 2019 ICAO/ 

CAEP meeting.) 

C. Technological Feasibility 

The EPA and FAA participated in the 

ICAO analysis that informed the 

adoption of the international aircraft 

engine PM emission standards. A 

summary of that analysis was published 

in the report of ICAO/CAEP’s eleventh 

meeting (CAEP/11),128 which occurred 

in February 2019. However, due to the 

commercial sensitivity of much of the 

data used in the ICAO analysis, the 

publicly available, published version of 

the ICAO report of the CAEP/11 meeting 

only provides limited supporting data 

for the ICAO analysis. Separately from 

this ICAO analysis and the CAEP/11 

meeting report, information on 

technology for the control of aircraft 

engine PM emissions is provided in an 

Independent Expert Review document 

on technology goals for engines and 

aircraft, which was published in 

2019.129 Although this ICAO document 

is primarily used for setting goals, and 

is not directly related to ICAO’s 

adoption of the PM emission standards, 

information from the Independent 

Expert Review is helpful in 

understanding the state of aircraft 

engine technology. 

The 2019 ICAO Independent Expert 

Review document indicates that new 

technologies aimed at reducing aircraft 

engine NOX also resulted in an order of 

magnitude reduction in nvPM mass and 

nvPM number in comparison to most inservice engines.130 (As described earlier 

in Section IV.D.1, only nvPM emissions 

would be measured in the proposed test 

procedure for the proposed standards.) 

Specifically, the current lean-burn 

engines and some advanced RichQuench-Lean (RQL) engines 131

developed for the purpose of achieving 

low NOX emissions coincidentally 

provide order of magnitude reductions 

in nvPM emissions in comparison to 

existing RQL engines. However, 

achieving these levels of nvPM 

emissions will be more difficult for 

physically smaller-sized engines due to 

technical constraints.132 In addition, 

some previous generation engines that 

are in production meet the proposed 

new type standards, which match the 

ICAO standards, with considerable 

margin. When considering the nvPM 

emission levels for current inproduction engines and those engines 

expected to be in production by the 

effective date of the ICAO standard, 

January 1, 2023, the lean-burn, 

advanced RQL, and some previous 

generation technologies (with relatively 

low levels of nvPM emissions) of many 

of the engines demonstrate that the 

proposed standards, which match ICAO 

standards, are technologically feasible. 

D. Costs Associated With the Proposed 

Rule 

EPA does not anticipate new 

technology costs due to the proposed 

rule. Nevertheless, it is informative to 

describe the elements of cost analysis 

for technology improvements, such as 

non-recurring costs (NRC), certification 

costs, and recurring costs. As described 

in the summary of the ICAO analysis for 

the PM emission standards,133

generally, CAEP considered certain 

factors as pertinent to the non-recurring 

cost estimates of a technology level for 

engine changes for PM mass and 

number. The first technology level was 

regarded as a minor change, and it could 

include minor improvements, and 

additional testing and re-certification of 

emissions. The PM mass and number 


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134 In addition, European authorities charge fees 

to aircraft engine manufacturers for the certification 

of their engines, but FAA does not charge fees for 

certification. 

emission reductions for the first 

technology level would be from 1 to 10 

percent, and the estimated associated 

costs would be $15 million. The second 

technology level was considered a 

scaled proven technology. At this level 

an engine manufacturer applies its bestproven, combustion technology that was 

already been certificated in at least one 

other engine type to another engine 

type. This second technology level 

would include substantial modeling, 

design, combustion rig testing, 

modification and testing of development 

engines, and flight-testing. The PM mass 

and number emission reductions for the 

second technology level would be a 

minimum of 10 percent, and the 

estimated associated costs would be 

$150 million and $250 million, 

respectively for PM mass and number. 

The third technology level was regarded 

as new technology or current industry 

best practice, and it was considered 

where a manufacturer has no proven 

technology that can be scaled to provide 

a solution and some technology 

acquisition activity is required. (One or 

more manufacturers have demonstrated 

the necessary technology, while the 

remaining manufacturers would need to 

acquire the technology to catch up.) The 

PM mass and number emission 

reductions for the third technology level 

would be a minimum of 25 percent, and 

the estimated costs would be $500 

million. As described earlier, since all 

in-production engines meet the inproduction standards and nearly all inproduction engines meet these new type 

standards—even though they do not 

have to, we believe that there would not 

be costs, nor emission reductions, from 

the proposed rule. Also, because current 

in-production engines would not be 

required to make any changes under this 

proposed rule, there will not be any 

adverse impact on noise and safety of 

these engines. Likewise, the noise and 

safety of future type designs should not 

be adversely impacted by compliance 

with these proposed new type standards 

since all manufacturers currently have 

engines that meet that level. 

Following the final rulemaking for the 

PM standards, the FAA would issue a 

rulemaking to enforce compliance to 

these standards, and any anticipated 

certification costs for the PM standards 

would be estimated by FAA. The EPA 

is not making any attempt to quantify 

the costs associated with certification 

actions required by the FAA to enforce 

these standards. 

As described earlier, manufacturers 

have already developed or are 

developing technologies to respond to 

ICAO standards that are equivalent to 

the proposed standards, and they will 

comply with the ICAO standards in the 

absence of U.S. regulations. Also, 

domestic implementation of the ICAO 

standards would potentially provide for 

a cost savings to U.S. manufacturers 

since it would enable them to certify 

their aircraft engine (via subsequent 

FAA rulemaking) domestically instead 

of having to certificate with a foreign 

authority (which would occur without 

this EPA rulemaking). If the proposed 

PM standards, which would match the 

ICAO standards, are not ultimately 

adopted in the United States, U.S. civil 

aircraft engine manufacturers will have 

to certify to the ICAO standards at 

higher costs because they will have to 

move their entire certification 

program(s) to a non-U.S. certification 

authority.134 Thus, there would be no 

new certification costs for the proposed 

rule, and the proposed rule could 

potentially provide a costs savings. 

For the same reasons there would be 

no NRC and certification costs for the 

proposed rule as discussed earlier, there 

would be no recurring costs (recurring 

operating and maintenance costs) for the 

proposed rule. The elements of 

recurring costs would include 

additional maintenance, material, labor, 

and tooling costs. 

As described earlier in Section IV.E, 

the EPA is proposing to formally 

incorporate the PM aspects of the 

existing information collection request 

(ICR) into the CFR (or regulations) in the 

proposed section 1031.150. This 

proposed action would not create a new 

requirement for the manufacturers of 

aircraft engines. Instead, it would 

simply incorporate the existing 

reporting requirements into the CFR for 

ease of use by having all the reporting 

requirements readily available in the 

CFR. Thus, this proposed action would 

not create new costs. 

E. Summary of Benefits and Costs 

The proposed standards match the 

ICAO standards, and ICAO intentionally 

established its standards at a level 

which is technology following. In doing 

this, ICAO adheres to its technical 

feasibility definition for the standard 

setting process, which is meant to 

consider the emissions performance of 

existing in-production engines and 

those engines expected to be in 

production by 2023. Independent of the 

ICAO standards all engines currently 

manufactured will meet the ICAO inproduction standards, and nearly all 

these same engines will meet the new 

type standards—even though these new 

type standards do not apply to inproduction engines. Therefore, there 

would be no costs and no additional 

benefits from complying with these 

proposed standards—beyond the 

benefits from maintaining consistency 

or harmonizing with the international 

standards and preventing backsliding by 

ensuring that all in-production and new 

type engines have at least the PM 

emission levels of today’s aircraft 

engines. 

VII. Technical Amendments 

In addition to the PM-related 

regulatory provisions discussed earlier 

in this document, the EPA is proposing 

technical amendments to the regulatory 

text that apply more broadly than to just 

the proposed new PM standards. First, 

the EPA is proposing to migrate the 

existing aircraft engine emissions 

regulations from 40 CFR part 87 to a 

new 40 CFR part 1031. Along with this 

migration, the EPA is proposing to 

restructure the regulations to allow for 

better ease of use and allow for more 

efficient future updates. The EPA is also 

proposing to delete some regulatory 

provisions and definitions that are 

unnecessary, as well as make several 

other minor technical amendments to 

the regulations. Finally, as explained in 

more detail below, EPA is also 

proposing revisions to 40 CFR part 87 to 

provide continuity during the transition 

of 40 CFR part 87 to 40 CFR part 1031. 

A. Migration of Regulatory Text to New 

Part 

In the 1990s, the EPA began an effort 

to migrate all transportation-related air 

emissions regulations to new parts, such 

that all mobile source regulations are 

contained in a single group of 

contiguous parts of the CFR. In addition 

to the migration, that effort has included 

clarifications to regulations and 

improvements to the ease of use through 

plain language updates and 

restructuring. To date, the aircraft 

engine emission regulations contained 

in 40 CFR part 87 are the only mobile 

source emission regulations which have 

not undergone this migration and 

update process. 

The current 40 CFR part 87 was 

initially drafted in the early 1970s and 

has seen numerous updates and 

revisions since then. This has led to a 

set of aircraft engine emission 

regulations that is difficult to navigate 

and contains numerous unnecessary 

provisions. Further, the current 

structure of the regulations would make 

the adoption of the PM standards 

proposed in this document, as well as 

any future standards the EPA may 


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propose, difficult to incorporate into the 

existing regulatory structure. 

Therefore, the EPA is proposing to 

migrate the existing aircraft engine 

regulations from 40 CFR part 87 to a 

new 40 CFR part 1031, directly after the 

airplane GHG standards contained in 40 

CFR part 1030. In the process, the EPA 

is proposing to restructure, streamline 

and clarify the regulatory provisions for 

ease of use and to facilitate more 

efficient future updates. Finally, the 

EPA is proposing to delete unnecessary 

regulatory provisions, which are 

discussed in detail in the next section. 

This regulatory migration and 

restructuring effort is not intended to 

change any substantive provision of the 

existing regulatory provisions. Thus, the 

EPA is not seeking comment on the 

proposed migration and restructuring, 

except in cases where a commenter 

believes that the proposed structure 

unintentionally changes the meaning of 

the regulatory text. The following two 

sections on the deletion of unnecessary 

provisions and additional technical 

amendments specify areas where the 

EPA invites comment on proposed 

changes to the regulations separate from 

the proposed migration and 

restructuring. 

As is noted in the amendatory text to 

the proposed regulations, the EPA is 

proposing to make this transition 

effective on January 1, 2023. The new 40 

CFR part 1031 would become effective 

(i.e., be incorporated into the Code of 

Federal Regulations) 30 days following 

the publication of the final rule in the 

Federal Register. However, the 

applicability language in the proposed 

section 1031.1 indicates that the new 40 

CFR part 1031 would apply to engines 

subject to the standards beginning 

January 1, 2023. Prior to January 1, 

2023, the existing 40 CFR part 87 would 

continue to apply. On January 1, 2023, 

the existing 40 CFR part 87 would be 

replaced with a significantly 

abbreviated version of 40 CFR part 87 

whose sole purpose would be to direct 

readers to the new 40 CFR part 1031. 

Additionally, a reference in the current 

40 CFR part 1030 to 40 CFR part 87 

would be updated to reference 40 CFR 

part 1031 at that time. The purpose of 

the abbreviated 40 CFR part 87 is to 

accommodate any references to 40 CFR 

part 87 that currently exist in the type 

certification documentation and 

advisory circulars issued by the FAA, as 

well as any other references to 40 CFR 

part 87 that currently exist elsewhere. 

Since it would be extremely difficult to 

identify and update all such documents 

prior to January 1, 2023, the EPA is 

instead proposing to adopt language in 

40 CFR part 87 that simply states the 

provisions relating to a particular 

section of the 40 CFR part 87 apply as 

described in a corresponding section of 

the proposed new 40 CFR part 1031. 

B. Deletion of Unnecessary Provisions 

As previously mentioned, the existing 

aircraft engine emissions regulations 

contain some unnecessary provisions 

which the EPA proposes to delete. 

These proposed deletions include 

transitional exemption provisions that 

are no longer available, several 

definitions, and some unnecessary 

language regarding the Secretary of the 

Department of Transportation, as 

detailed in the following paragraphs. 

The EPA is proposing to not migrate 

the current 40 CFR 87.23(d)(1) and (3) 

to the new 40 CFR part 1031. Both these 

paragraphs contain specific phase-in 

provisions available for a short period 

after the Tier 6 NOX standards began to 

apply, and their availability as 

compliance provisions ended on August 

31, 2013. Thus, they are no longer 

needed. It should be noted that while 

the EPA is proposing to effectively 

delete these provisions by not migrating 

them to the proposed new 40 CFR part 

1031, the underlying standards referred 

to in these provisions (i.e., the Tier 4 

and 6 NOx standards) are proposed to 

remain unchanged. Thus, the 

underlying certification basis for any 

engines certificated under these 

provisions will remain intact. 

The EPA is also proposing to delete a 

number of definitions from the current 

40 CFR part 87 as it is migrated to the 

new proposed Part 1031 for two reasons. 

First, in the effort to streamline and 

clarify the regulations, some of these 

definitions have effectively been 

incorporated directly into the regulatory 

text where they are used, making a 

standalone definition unnecessary and 

redundant. Second, some of these 

definitions are simply not needed for 

any regulatory purpose and are likely 

artifacts of previous revisions to the 

regulations (e.g., where a regulatory 

provision was deleted but the associated 

definition was not). 

The definitions that the EPA proposes 

to delete and the reasons for the 

proposed deletions are listed in Table 

VII–1. 

TABLE VII–1—LIST OF TERMS FOR WHICH DEFINITIONS ARE PROPOSED TO BE DELETED

Term Reason for proposed deletion 

Act ................................................... Not used in the regulatory text. 

Administrator ................................... No longer needed as not used in proposed revised and streamlined regulatory text. 

Class TP ......................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Class TF .......................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Class T3 .......................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Class T8 .......................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Class TSS ....................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Commercial aircraft ......................... No longer needed as not used in proposed revised and streamlined regulatory text. 

Commercial aircraft gas turbine engine.No longer needed as not used in proposed revised and streamlined regulatory text. 

Date of introduction ......................... Unnecessary definition that is not used in existing regulatory text and not needed in revised regulatory text. 

Engine ............................................. For regulatory purposes, definition of engine not needed given existing definitions of Aircraft engine, Engine model, and Engine sub-model. 

In-use aircraft gas turbine engine ... No longer needed in light of proposed deletion of unnecessary provisions and technical amendments to 

fuel venting requirements. 

Military aircraft ................................. Not needed as regulatory text applies to commercial engines. 

Operator .......................................... No longer needed as not used in proposed revised and streamlined regulatory text. 

Production cutoff or the date of production cutoff.No longer needed with proposed deletion of unnecessary exemption provisions and streamlining of exemption regulatory text. 

Tier 0 ............................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Tier 2 ............................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Tier 4 ............................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Tier 6 ............................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 

Tier 8 ............................................... No longer needed as definition was effectively incorporated into regulatory text during proposed migration. 


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135 77 FR 36342, June 18, 2012. 

TABLE VII–1—LIST OF TERMS FOR WHICH DEFINITIONS ARE PROPOSED TO BE DELETED—Continued 

Term Reason for proposed deletion 

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

The EPA is also proposing to not 

migrate the current 40 CFR 87.3(b) to 

the new 40 CFR part 1031, which in 

effect will result in its deletion. This 

paragraph is simply a restatement of an 

obligation directly imposed under the 

Clean Air Act the Secretary shall issue 

regulations to assure compliance with 

the regulations issued under the Act. 

This is not a regulatory requirement 

related to the rest of the part, and as 

such it is not needed in the proposed 40 

CFR part 1031. 

C. Other Technical Amendments and 

Minor Changes 

In addition to the migration of the 

regulations to a new part and the 

removal of unnecessary provisions just 

discussed, the EPA is proposing some 

minor technical amendments to the 

regulations. 

The EPA is proposing to add 

definitions for ‘‘Airplane’’ and 

‘‘Emission index.’’ Both these terms are 

used in the current aircraft engine 

emissions regulations, but they are 

currently undefined. The new proposed 

definitions would help provide clarity 

to the provisions that utilize those 

terms. 

The EPA proposes to modify the 

definitions for ‘‘Exception’’ and 

‘‘Exemption.’’ The current definitions of 

these terms in Part 87.1 go beyond 

simply defining the terms and contain 

what could more accurately be 

described as regulatory requirements 

stating what provisions an excepted or 

exempted engine must meet. These 

portions of the definitions, which are 

more accurately described as regulatory 

requirements, are proposed to be moved 

to the introductory text in 1031.15 and 

1031.20, as applicable. These proposed 

changes are in no way intended to 

change any regulatory requirement 

applicable to excepted or exempted 

engines. Rather, they are proposed 

simply to more clearly separate 

definitions from the related regulatory 

requirements. 

The EPA is proposing to not migrate 

the existing 87.42(d) to the proposed 

new Part 1031, which in effect will 

result in the deletion of this provision. 

This paragraph in the annual 

production report section regards the 

identification and treatment of 

confidential business information (CBI) 

in manufacturers’ annual production 

reports. The EPA is instead relying on 

the existing CBI regulations in 40 CFR 

1068.10 (as referenced in the proposed 

1031.170). This proposed change would 

have no impact on the ability of 

manufacturers to make claims of CBI, or 

in the EPA’s handling of such claims. 

However, it would assure a more 

consistent treatment of CBI across 

mobile source programs. 

The EPA is proposing a minor change 

to the existing emissions requirements 

for spare engines, as found in 

87.50(c)(2). In the proposed regulatory 

text for 1031.20(a), the EPA is proposing 

to delete the existing provision that a 

spare engine is required to meet 

standards applicable to Tier 4 or later 

engines (currently contained in 40 CFR 

87.50(c)(2)). The EPA is proposing to 

retain and migrate to part 1031 the 

requirement in 40 CFR 87.50(c)(3) such 

that a spare engine would need to be 

certificated to emission standards equal 

to or lower than those of the engines 

they are replacing, for all regulated 

pollutants. This proposed deletion of 40 

CFR 87.50(c)(2) would align with 

ICAO’s current guidance on the 

emissions of spare engines and is 

consistent with U.S. efforts to secure the 

highest practicable degree of uniformity 

in aviation regulations and standards. 

The EPA does not believe this proposed 

change would have any impact on 

current industry practices. Deleting the 

provision currently in 40 CFR 

87.50(c)(2) would leave in place the 

requirement that any new engine 

manufactured as a spare would need to 

be at least as clean as the engine it is 

replacing (as stated in the current 40 

CFR 87.50(c)(3)), but with no 

requirement that it meet standards 

applicable to Tier 4 or later engines. 

Thus, under this proposed deletion a 

new spare engine could, in theory, be 

manufactured that only met pre-Tier 4 

standards. The Tier 4 standards became 

effective in 2004, so the proposed 

deletion would only impact spare 

engines manufactured to replace 

engines manufactured roughly before 

2004. It is extremely unlikely that a 

manufacturer would build a new engine 

as a replacement for such an old design 

as it would be very disruptive to the 

manufacturing of current designs for 

new aircraft. Rather, it is common 

practice that spares for use in replacing 

older engines would not be newly 

manufactured engines of an old design, 

but engines that have been taken from 

similar aircraft that have been retired. 

The EPA does not believe that any 

engines would be manufactured to preTier 4 designs for use as spare engines 

given current practices. Thus, the EPA 

does not believe that this proposed 

deletion of 40 CFR 87.50(c)(2) for the 

purposes of uniformity would have any 

practical impact on current industry 

practices. 

The EPA is proposing to align the 

applicability of smoke number 

standards for engines used in 

supersonic airplanes with ICAO’s 

applicability. The EPA adopted 

emission standards for engines used on 

supersonic airplanes in 2012.135 Those 

standards were equivalent to ICAO’s 

existing standards with one exception. 

ICAO’s emission standards fully apply 

to all engines to be used on supersonic 

airplanes, regardless of rated output. In 

an apparent oversight, the EPA only 

applied the smoke number standards to 

engines of greater than or equal to 26.7 

kN rated output. Thus, the EPA is 

proposing to apply smoke number 

standards to include engines below 26.7 

kN rated output for use on supersonic 

airplanes which are equivalent to 

ICAO’s provisions. This change is 

proposed consistent with U.S. efforts to 

secure the highest practicable degree of 

uniformity in aviation regulations and 

standards and would have no practical 

impact on engine manufacturers. The 

EPA is currently unaware of any engines 

in production which could be used on 

supersonic airplanes, and those being 

developed for application to future 

supersonic airplanes are expected to be 

well above 26.7 kN rated output, and 

thus, they would be covered by the 

existing smoke number standard. 

Throughout its regulations, the EPA is 

proposing to align with ICAO regarding 

a common rated output threshold for 

emission regulations. The applicability 

and/or stringency of several aircraft 

engine emission standards can be 

different depending on whether an 

engine’s rated output is above or below 

26.7 kN. In the ICAO regulations, the 

threshold is consistently stated as either 

greater than, or less than or equal to 26.7 

kN. In the current 40 CFR part 87, the 

equal to portion of the threshold is 

applied inconsistently. In some cases, it 


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

is expressed as less than, and greater 

than or equal to. In other cases, it is 

expressed as greater than, and less than 

or equal to. The proposal is to make all 

instances in the proposed Part 1031 

consistent with ICAO, i.e., greater than, 

and less than or equal to. As there are 

no current engines with a rated output 

of exactly at 26.7 kN, this proposed 

change would have no practical impact. 

However, it is consistent with U.S. 

efforts to secure the highest practicable 

degree of uniformity in aviation 

regulations and standards. 

The EPA is proposing to incorporate 

by reference Appendix 1 of ICAO’s 

Annex 16, Volume II. This appendix 

deals with the determination of a test 

engine’s reference pressure ratio, and its 

exclusion from the U.S. regulations was 

an oversight. Other Annex 16, Volume 

II appendices which contain test 

procedures, fuel specifications, and 

other compliance-related provisions 

have been incorporated by reference 

into the U.S. regulations for many years, 

and it is important to correct this 

oversight so that the complete testing 

and compliance provisions are clear. 

The EPA is proposing to streamline, 

restructure, and update the exemption 

provisions currently in 40 CFR 87.50. 

First, this section contains provisions 

regarding exemptions, exceptions, and 

annual reporting provisions relating to 

exempted and excepted engines. The 

EPA is proposing to migrate the 

exceptions section concerning spare 

engines (87.50(c)) to its own new 

section 1031.20(a), with the proposed 

changes discussed earlier in this 

section. The provisions regarding the 

annual reporting of exempted and 

excepted engines are proposed to be 

incorporated into the new annual 

reporting section 1031.150. These 

reporting provisions otherwise remain 

unchanged. Section 87.50(a), regarding 

engines installed on new aircraft, and 

section 87.50(b), regarding temporary 

exemptions based on flights for short 

durations at infrequent intervals, are 

proposed to be migrated to a new 

section 1031.15. The temporary 

exemptions provisions remain 

unchanged, with the exception of the 

addition of ‘‘of Transportation’’ after 

‘‘Secretary’’ in 1031.15(b)(4) to provide 

additional clarity. The proposed 

changes to the exemptions for engines 

installed on new aircraft are a bit more 

extensive, as discussed in the next 

paragraph. 

In 2012, the EPA adopted new 

exemption provisions specifically to 

provide flexibility during the transition 

to Tier 6 and Tier 8 NOX standards.136

These provisions were only available 

through December 31, 2016 and are 

proposed to be deleted, as previously 

discussed. However, during the 

adoption of those transitional 

flexibilities, the EPA inadvertently 

replaced the existing exemption 

provisions with the new transitional 

provisions rather than appending the 

transitional provisions to the existing 

ones. This left 87.50 with no general 

exemption language, only those 

provisions specific to the newly adopted 

NOX standards. Given that the 

transitional NOX exemption provisions 

have expired and are now obsolete, the 

EPA is proposing to delete them rather 

than migrate them to the new 1031.15. 

The EPA is further proposing to restore 

the general exemption authority that 

was inadvertently removed in 2012. In 

a recent action which established GHG 

standards for airplanes, the EPA 

adopted much more streamlined 

exemption provisions for airplanes in 

consultation with the FAA.137 The EPA 

is proposing to adopt similarly 

streamlined general exemption 

provisions for aircraft engines as well, 

as contained in the proposed 1031.15(a). 

The EPA is proposing some changes 

relative to the prohibition on fuel 

venting. The fuel venting standard is 

intended to prevent the discharge of fuel 

to the atmosphere following engine 

shutdown, as explicitly stated in 40 CFR 

87.11(a). The existing definition for fuel 

venting emissions in 87.1 defines fuel 

venting emissions as fuel discharge 

during all normal ground and flight 

operations. As the standard section 

itself limits the applicability only to 

venting that occurs following engine 

shutdown, consistent with ICAO’s fuel 

venting provisions, the EPA is 

proposing to delete the definition for 

fuel venting emissions as both 

unnecessary and contradictory to the 

actual requirement. Further, the EPA is 

proposing to add the word ‘‘liquid’’ 

before fuel in the fuel venting 

requirements, consistent with the ICAO 

fuel venting provisions. Neither of these 

proposed changes would have any 

practical effect on the requirements on 

engine manufacturers, but these changes 

both clarify the requirements and fully 

align with ICAO standards and 

recommended practices, consistent with 

U.S. efforts to secure the highest 

practicable degree of uniformity in 

aviation regulations and standards. 

The EPA is proposing to modify the 

applicability date language associated 

with the standards applicable to Tier 8 

engines, as contained in the proposed 

1031.60(e)(2). The applicability of new 

type standards has traditionally been 

linked to the date of the first individual 

production engine of a given type, both 

for EPA regulations and ICAO 

regulations. This approach has been 

somewhat cumbersome in the past 

because a manufacturer would have to 

estimate what standards would be in 

effect when actual production of a new 

type began in order to determine to 

what standards a new type engine 

would be subject. Given that the engine 

type certification process can take up to 

three years, this approach has proven 

problematic during periods of transition 

from one standard to another. To 

address this concern, ICAO agreed at the 

CAEP/11 meeting in 2019 to transition 

from the date of manufacture of the first 

production engine to the date of 

application for a type certificate to 

determine standards applicability for 

new types. The EPA was actively 

involved in the deliberations that led to 

this agreement and supported the 

transition from date of first individual 

production model to date of application 

for type certification as the basis for 

standards applicability in the future. 

This approach is reflected in the 

applicability date provisions of the 

proposed PM standards, consistent with 

ICAO. The EPA is also proposing to 

adopt it for existing standards 

applicable to Tier 8 engines as well. 

This proposed change would have no 

impact on manufacturers as the existing 

standards applicable to Tier 8 engines 

have been in place since 2014, and there 

are no new gaseous or smoke number 

standards set to take effect for such 

engines. Thus, this proposed change is 

solely intended to improve consistency 

with ICAO and to structure the 

regulations such that the adoption of 

any future standards using this 

applicability date approach would be 

straightforward. 

The EPA is proposing to revise the 

definition of ‘‘date of manufacture’’ by 

replacing ‘‘competent authority’’ with 

‘‘recognized airworthiness authority’’ in 

two places. The term ‘‘competent’’ has 

no specific meaning in the context of 

either the EPA’s or the FAA’s 

regulations. However, the FAA does 

recognize other airworthiness 

authorities for engines certificated 

outside the United States, as indicated 

through existing bilateral agreements 

with such authorities. Also, the EPA is 

proposing to update its definition of 

‘‘supersonic’’ by replacing it with a new 

definition of ‘‘supersonic airplane.’’ The 

proposed new definition for 

‘‘supersonic airplane’’ is based on a 

revised definition for such proposed by 

the FAA in a recent proposed action 


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138 85 FR 20431, April 13, 2020. 

139 86 FR 2136, January 11, 2021. 

140U.S. EPA, 2021: Determination of no SISNOSE 

for Proposed Aircraft Engine Emission Standards, 

Memorandum to Docket ID No. EPA–HQ–OAR– 

2019–0660. This memorandum describes that the 

only small entity is Williams Int’l, which only make 

engines below 26.7 kN. Thus, they are not subject 

to the proposed standards. 

regarding noise regulations for 

supersonic airplanes.138 This proposed 

new definition would provide greater 

assurance that the proposed standards 

applicable to engines used on 

supersonic airplanes would apply to the 

engines for which they are intended. 

The EPA is proposing to update 

several definitions and align them with 

definitions included in the recent 

airplane GHG regulations.139 The 

definitions proposed to be updated are 

for ‘‘Aircraft,’’ ‘‘Aircraft engine,’’ 

‘‘Airplane,’’ ‘‘Exempt,’’ and ‘‘Subsonic.’’ 

These definitions are proposed to be 

updated in the aircraft engine 

regulations simply for consistency with 

the airplane GHG regulations and with 

FAA regulations. The changes being 

proposed would not have any impact on 

the regulatory requirements related to 

the definitions. 

The EPA is also proposing to address 

an unintentional applicability gap 

related to EPA’s airplane GHG standards 

that could potentially exclude some 

airplanes from being subject to the 

standards. The intention of the 

international standards was to cover all 

jet airplanes with an MTOM greater 

than 5,700 kg. At ICAO it was agreed 

that airplanes with an MTOM less than 

60,000 kg and with 19 seats or fewer 

could have extra time to comply with 

the standards (incorporated at 40 CFR 

1030.1(a)(2)). With that in mind, 40 CFR 

1030.1(a)(1) was written to cover 

airplanes with 20 or more seats and an 

MTOM greater than 5,700 kg. However, 

this means that airplanes with 19 seats 

or fewer and an MTOM greater than 

60,000 kg are not covered by the current 

regulations but would be covered by the 

ICAO CO2 standard. While the EPA is 

not aware of any airplanes in this size 

range, the intent of the EPA’s GHG rule 

was to cover all jet airplanes with 

MTOM greater than 5,700 kg. The EPA 

is proposing to adopt new language at 

40 CFR 1030.1(a)(1)(iv)–(vi) to cover 

these airplanes, should they be 

produced. This proposed change would 

expand the current applicability of the 

GHG standards on the date this final 

rulemaking goes into effect. However, 

airplanes in this size category were 

considered as part of the GHG standard 

setting process and had been intended 

to be subject to the GHG standards. 

The EPA is proposing to correct the 

effective date of new type design GHG 

standards for turboprop airplanes (with 

a maximum takeoff mass greater than 

8,618 kg), which is currently specified 

in 40 CFR 1030.1(a)(3)(ii) as January 1, 

2020. The EPA did not intend to 

retroactively apply these standards 

using the ICAO new type start date for 

these airplanes. Rather, this effective 

date should have been January 11, 2021, 

to be consistent with the effective date 

of new type standards for other 

categories of airplanes in this part (e.g., 

40 CFR 1030.1(a)(1)). Based on 

consultations with the FAA, this 

proposed change to part 1030 will not 

impact any airplanes. 

Finally, the EPA is proposing a minor 

word change to the existing 

applicability language in 40 CFR part 

1030 in order to make it consistent with 

the current applicability language in the 

EPA’s airplane engine regulations as 

well as FAA regulations. Specifically, 

the current language in 40 CFR 

1030.1(c)(7) refers to airplanes powered 

with piston engines. The EPA is 

proposing to replace the word ‘‘piston’’ 

with ‘‘reciprocating’’ in 40 CFR 

1030.1(c)(7) to align it with the existing 

40 CFR 87.3(a)(1), the proposed 

language in 40 CFR 1031.1(b)(1), and 

existing FAA regulations in 14 CFR 

parts 1 and 33. This proposed change is 

for consistency among federal 

regulations and to avoid any confusion 

that may be caused by the use of two 

different terms. This proposed change 

would have no material impact on the 

meaning of the regulatory text. 

VIII. Statutory Authority and Executive 

Order Reviews 

Additional information about these 

statutes and Executive orders can be 

found at https://www.epa.gov/lawsregulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

This action is a significant regulatory 

action that was submitted to the Office 

of Management and Budget (OMB) for 

review. This action raises ‘‘. . . novel 

legal or policy issues arising out of legal 

mandates, the President’s priorities, or 

the principles set forth in this Executive 

Order.’’ This action promulgates new 

aircraft engine emissions regulations 

and as such, requires consultation and 

coordination with the Federal Aviation 

Administration (FAA). Accordingly, the 

EPA submitted this action to the OMB 

for review under E.O. 12866 and E.O. 

13563. Any changes made in response 

to OMB recommendations have been 

documented in the docket. Section VI.E 

of this preamble summarizes the cost 

and benefits of this action. 

B. Paperwork Reduction Act (PRA) 

This action does not impose any new 

information collection burden under the 

PRA. OMB has previously approved the 

information collection activities 

contained in the existing regulations 

and has assigned OMB control number 

2060–0680. This proposed rule would 

codify that existing collection by 

including the current nvPM data 

collection in the proposed regulatory 

text, but it would not add any new 

reporting requirements. 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. Among the potentially 

affected entities (manufacturers of 

aircraft engines) there is only one small 

entity, and that aircraft engine 

manufacturer does not make engines in 

the category subject to the proposed 

new provisions contained in this 

document (i.e., engines greater than 26.7 

kN rated output) and has not indicated 

any plans to begin such production. 

Therefore, this action will not impose 

any requirements on small entities. 

Supporting information can be found in 

the docket.140

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain any 

unfunded mandate as described in 

UMRA, 2 U.S.C. 1531–1538, and does 

not significantly or uniquely affect small 

governments. The action imposes no 

enforceable duty on any state, local or 

tribal governments or the private sector. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the national 

government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have tribal 

implications as specified in Executive 

Order 13175. This action regulates the 

manufacturers of aircraft engines and 

will not have substantial direct effects 

on one or more Indian tribes, on the 

relationship between the Federal 

Government and Indian tribes, or on the 

distribution of power and 


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responsibilities between the Federal 

Government and Indian tribes. Thus, 

Executive Order 13175 does not apply 

to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

This action is not subject to Executive 

Order 13045 because it is not 

economically significant as defined in 

Executive Order 12866. This action’s 

health and risk assessments are 

contained in Section III. 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution or Use 

This action is not a ‘‘significant 

energy action’’ because it is not likely to 

have a significant adverse effect on the 

supply, distribution or use of energy. 

These aircraft engine emissions 

regulations are not expected to result in 

any changes to aircraft fuel 

consumption. 

I. National Technology Transfer and 

Advancement Act (NTTAA) 

This action involves technical 

standards for testing emissions for 

aircraft gas turbine engines. EPA is 

proposing to use test procedures 

contained in ICAO’s International 

Standards and Recommended Practices 

Environmental Protection, Annex 16, 

Volume II along with the modifications 

contained in this rulemaking as 

described in Section IV. These 

procedures are currently used by all 

manufacturers of aircraft gas turbine 

engines to demonstrate compliance with 

ICAO emissions standards. 

In accordance with the requirements 

of 1 CFR 51.5, we are incorporating by 

reference the use of test procedures 

contained in ICAO’s International 

Standards and Recommended Practices 

Environmental Protection, Annex 16, 

Volume II, along with the modifications 

contained in this rulemaking. This 

includes the following standards and 

test methods: 

Standard or test method Regulation Summary 

ICAO 2017, Aircraft Engine Emissions, Annex 

16, Volume II, Fourth Edition, July 2017, as 

amended by Amendment 10, January 1, 

2021.

40 CFR 1031.140(a), (b), (f), (g), and (h), and 

40 CFR 1031.205.

Test method describes how to measure PM, 

gaseous and smoke emissions from aircraft 

engines. 

The version of the ICAO Annex 16, 

Volume II that is proposed to be 

incorporated into the new 40 CFR part 

1031 is the same version that is 

currently incorporated by reference in 

40 CFR 87.1, 40 CFR 87.42(c), and 40 

CFR 87.60(a) and (b). 

The referenced standards and test 

methods may be obtained through the 

International Civil Aviation 

Organization, Document Sales Unit, 999 

University Street, Montreal, Quebec, 

Canada H3C 5H7, (514) 954–8022, 

www.icao.int, or sales@icao.int. 

J. Executive Order 12898: Federal 

Actions to Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

The EPA believes that this action does 

not have disproportionately high and 

adverse human health or environmental 

effects on minority populations, lowincome populations and/or indigenous 

peoples, as specified in Executive Order 

12898 (59 FR 7629, February 16, 1994). 

This proposed action would not achieve 

emission reductions and would 

therefore result in no improvement in 

per-aircraft emissions for all 

communities living near airports. EPA 

describes in Section III.G the existing 

literature reporting on disparities in 

potential exposure to aircraft emissions 

for people of color and low-income 

populations. EPA, in an action separate 

from this proposed rulemaking, will be 

conducting an analysis of the 

communities residing near airports 

where jet aircraft operate in order to 

more fully understand 

disproportionately high and adverse 

human health or environmental effects 

on people of color, low-income 

populations and/or indigenous peoples, 

as specified in Executive Order 12898. 

The results of this analysis could help 

inform additional policies to reduce 

pollution in communities living in close 

proximity to airports. 

List of Subjects 

40 CFR Parts 87 and 1031 

Environmental protection, Air 

pollution control, Aircraft, 

Incorporation by reference. 

40 CFR Part 1030 

Environmental protection, Air 

pollution control, Aircraft, Greenhouse 

gases. 

Michael S. Regan, 

Administrator. 

For the reasons set forth in the 

preamble, EPA proposes to amend 40 

CFR parts 87, 1030, and 1031 as follows: 

PART 87—CONTROL OF AIR 

POLLUTION FROM AIRCRAFT AND 

AIRCRAFT ENGINES 

■ 1. Revise part 87 to read as follows: 

PART 87—CONTROL OF AIR 

POLLUTION FROM AIRCRAFT AND 

AIRCRAFT ENGINES 

87.1 Definitions. 

87.2 Abbreviations. 

87.3 General applicability and 

requirements. 

87.10 Applicability—fuel venting. 

87.11 Standard for fuel venting emissions. 

87.20 Applicability—exhaust emissions. 

87.21 Exhaust emission standards for Tier 4 

and earlier engines. 

87.23 Exhaust emission standards for Tier 6 

and Tier 8 engines. 

87.31 Exhaust emission standards for in-use 

engines. 

87.48 Derivative engines for emissions 

certification purposes. 

87.50 Exemptions and exceptions. 

87.60 Testing engines. 

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

§ 87.1 Definitions. 

Definitions apply as described in 40 

CFR 1031.205. 

§ 87.2 Abbreviations. 

Abbreviations apply as described in 

40 CFR 1031.200. 

§ 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. 


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§ 87.10 Applicability—fuel venting. 

Fuel venting standards apply to 

certain aircraft engines as described in 

40 CFR 1031.30(b). 

§ 87.11 Standard for fuel venting 

emissions. 

Fuel venting standard apply as 

described in 40 CFR 1031.30(b). 

§ 87.20 Applicability—exhaust emissions. 

Exhaust emission standards apply to 

certain aircraft engines as described in 

40 CFR 1031.40 through 1031.90. 

§ 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. 

§ 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 inproduction aircraft engines as described 

in 40 CFR 1031.60. 

§ 87.31 Exhaust emission standards for inuse engines. 

Exhaust emission standards apply to 

in-use aircraft engines as described in 

40 CFR 1031.60. 

§ 87.48 Derivative engines for emissions 

certification purposes. 

Provisions related to derivative 

engines apply as described in 40 CFR 

1031.130. 

§ 87.50 Exemptions and exceptions. 

Provisions related to exceptions apply 

as described in 40 CFR 1031.11. 

Provisions related to exemptions apply 

as described in 40 CFR 1031.10. 

§ 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 

■ 2. The authority citation for part 1030 

continues to read as follows: 

Authority: 42 U.S.C. 7401–7671q. 

■ 3. Amend § 1030.1 by: 

■ a. Revising paragraphs (a) 

introductory text and (a)(1)(iii); 

■ b. Adding paragraphs (a)(1)(iv) 

through (vi); 

■ c. Revising paragraphs (a)(3)(ii) and 

(c)(7). 

The revisions and additions read as 

follows: 

§ 1030.1 Applicability. 

(a) Except as provided in paragraph 

(c) of this section, when an aircraft 

engine subject to 40 CFR part 1031 is 

installed on an airplane that is 

described in this section and subject to 

title 14 of the Code of Federal 

Regulations, the airplane may not 

exceed the Greenhouse Gas (GHG) 

standards of this part when original 

civil certification under title 14 is 

sought. 

(1) * * * 

(iii) An application for original type 

certification that is submitted on or after 

January 11, 2021; or 

(iv) A type-certificated maximum 

passenger seating capacity of 19 seats or 

fewer, and 

(v) A MTOM greater than 60,000 kg, 

and 

(vi) An application for original type 

certification that is submitted on or after 

[DATE OF PUBLICATION OF FINAL 

RULE IN THE FEDERAL REGISTER]. 

* * * * * 

(3) * * * 

(ii) An application for original type 

certification that is submitted on or after 

January 11, 2021. 

* * * * * 

(c) * * * 

(7) Airplanes powered by 

reciprocating engines. 

■ 4. Add part 1031 to read as follows: 

PART 1031—CONTROL OF AIR 

POLLUTION FROM AIRCRAFT 

ENGINES 

Subpart A—Scope and Applicability 

1031.1 Applicability. 

1031.5 Engines installed on domestic and 

foreign aircraft. 

1031.10 State standards and controls. 

1031.15 Exemptions. 

1031.20 Exceptions. 

Subpart B—Emission Standards and 

Measurement Procedures 

1031.30 Overview of emission standards 

and general requirements. 

1031.40 Turboprop engines. 

1031.50 Subsonic turbojet and turbofan 

engines at or below 26.7 kN thrust. 

1031.60 Subsonic turbojet and turbofan 

engines above 26.7 kN thrust. 

1031.90 Supersonic Engines. 

1031.130 Derivative engines for emissions 

certification purposes. 

1031.140 Test procedures 

Subpart C—Reporting and Recordkeeping 

1031.150 Production reports. 

1031.160 Recordkeeping. 

1031.170 Confidential business 

information. 

Subpart D—Reference Information 

1031.200 Abbreviations. 

1031.205 Definitions. 

1031.210 Incorporation by reference. 

Authority: –42 U.S.C. 7401–7671q. 

Subpart A—Scope and Applicability 

§ 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. 

§ 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. 

§ 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. 

§ 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 


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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. 

§ 1031.20 Exceptions. 

Individual engines may be excepted 

from current standards as described in 

this section. Excepted engines must 

conform to regulatory conditions 

specified for an exception in this part 

and other applicable regulations. 

Excepted engines are deemed to be 

‘‘subject to’’ the standards of this part 

even though they are not required to 

comply with the otherwise applicable 

requirements. Engines excepted with 

respect to certain standards must 

comply with other standards from 

which they are not excepted. 

(a) Spare engines. Newly 

manufactured engines meeting the 

definition of ‘‘spare engine’’ are 

automatically excepted as follows: 

(1) This exception allows production 

of a newly manufactured engine for 

installation on an in-use aircraft. It does 

not allow for installation of a spare 

engine on a new aircraft. 

(2) Spare engines excepted under this 

paragraph (a) may be used only if they 

are certificated to emission standards 

equal to or lower than those of the 

engines they are replacing, for all 

regulated pollutants. 

(3) Engine manufacturers do not need 

to request approval to produce spare 

engines, but must include information 

about spare engine production in the 

annual report specified in § 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 

§ 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 

§§ 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 mg/ 

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 § 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 § 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. 

§ 1031.40 Turboprop engines. 

The following standards apply to 

turboprop engines with rated output at 

or above 1,000 kW: 

(a) Smoke. (1) Engines of a type or 

model for which the date of 

manufacture of the individual engine is 

on or after January 1, 1984, may not 

have a characteristic level for smoke 

number exceeding the following value: 

SN = 187·rO¥0.168 

(2) [Reserved] 

(b) [Reserved] 

§ 1031.50 Subsonic turbojet and turbofan 

engines at or below 26.7 kN thrust. 

The following standards apply to new 

turbofan or turbojet aircraft engines with 

rated output at or below 26.7 kN thrust 

that are installed in subsonic aircraft: 

(a) Smoke. (1) Engines of a type or 

model for which the date of 


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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·rO¥0.274 

(2) [Reserved] 

(b) [Reserved] 

§ 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·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·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 · 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 mg/m∧3 exceeding the 

following emission standard: 

nvPMMC = 10(3∂2.9·rO−0.274)

(b) LTO nvPM mass and number. An 

engine’s characteristic level for nvPM 

mass and nvPM number may not exceed 

emission standards as follows: 

(1) Tier 11 new type. The following 

emission standards apply to engines of 

a type or model for which an 

application for original type 

certification is submitted on or after 

January 1, 2023 and for engines covered 

by an earlier type certificate if they do 

not qualify as derivative engines for 

emission purposes as described in 

§ 1031.130: 

TABLE 1 TO § 1031.60(b)(1)—TIER 11 NEW TYPE nvPM STANDARDS

Rated output (rO) in kN nvPMmass in milligrams/kN nvPMnum in particles/kN 

26.7 < rO ≤ 150 ................................................. 1251.1¥6.914·rO ............................................. 1.490·10∧16¥8.080·10∧13·rO 

rO > 150 ............................................................ 214.0 ................................................................. 2.780·10∧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 § 1031.60(b)(2)—TIER 11 IN-PRODUCTION nvPM STANDARDS

Rated output (rO) in kN nvPMmass in milligrams/kN nvPMnum in particles/kN 

26.7 < rO ≤ 200 ................................................. 4646.9¥21.497·rO ........................................... 2.669·10∧16¥1.126·10∧14·rO 

rO > 200 ............................................................ 347.5 ................................................................. 4.170·10∧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(rPR)) g/kN 

(2) Tier 2. The following NOX

emission standards apply to engines of 

a type or model for which the date of 

manufacture of the first individual 

production model was after December 

31, 1995 or for which the date of 

manufacture of the individual engine 

was on or after December 31, 1999 and 

before December 31, 2003: 

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

(3) Tier 4 new type. The following 

NOX emission standards apply to 

engines of a type or model for which the 

date of manufacture of the first 

individual production model was after 

December 31, 2003 and before July 18, 

2012: 

TABLE 3 TO § 1031.60(e)(3)—TIER 4 NEW TYPE NOX STANDARDS

If the rated pressure ratio (rPR) is— and the rated output (kN) is— the NOX emission standard (g/kN) is— 

(i) rPR ≤ 30 ..................................... (A) 26.7 < rO ≤ 89 ......................... 37.572 + 1.6(rPR)¥0.2087(rO) 

(B) rO > 89 .................................... 19 + 1.6·rPR 


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TABLE 3 TO § 1031.60(e)(3)—TIER 4 NEW TYPE NOX STANDARDS—Continued 

If the rated pressure ratio (rPR) is— and the rated output (kN) is— the NOX emission standard (g/kN) is— 

(ii) 30 < rPR < 62.5 ......................... (A) 26.7 < rO ≤ 89 ......................... 42.71 + 1.4286(rPR)¥0.4013(rO) + 0.00642(rPR × rO) 

(B) rO > 89 .................................... 7 + 2·rPR 

(iii) rPR ≥ 82.6 ................................. All ................................................... 32 + 1.6·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 § 1031.60(e)(4)—TIER 6 IN-PRODUCTION NOX STANDARDS

If the rated pressure ratio (rPR) is— and the rated output (kN) is— the NOX emission standard (g/kN) is— 

(i) rPR ≤ 30 ..................................... (A) 26.7 < rO ≤ 89 ......................... 38.5486 + 1.6823·rPR¥0.2453·rO¥0.00308·rPR·rO 

(B) rO > 89 .................................... 16.72 + 1.4080·rPR 

(ii) 30 < rPR < 82.6 ......................... (A) 26.7 < rO ≤ 89 ......................... 46.1600 + 1.4286·rPR¥0.5303·rO + 0.00642·rPR·rO 

(B) rO > 89 .................................... ¥1.04 + 2.0·rPR 

(iii) rPR ≥ 82.6 ................................. All ................................................... 32 + 1.6·rPR 

(5) Tier 8 new type. The following 

NOX standards apply to engines of a 

type or model for which the date of 

manufacture of the first individual 

production model was on or after 

January 1, 2014; or for which an 

application for original type 

certification is submitted on or after 

January 1, 2023; or for engines covered 

by an earlier type certificate if they do 

not qualify as derivative engines for 

emission purposes as described in 

§ 1031.130: 

TABLE 5 TO § 1031.60(e)(5)—TIER 8 NEW TYPE NOX STANDARDS

If the rated pressure ratio (rPR) is— and the rated output (kN) is— the NOX emission standard (g/kN) is— 

(i) rPR ≤ 30 ........................................................ (A) 26.7 < rO ≤ 89 ............................................ 40.052 + 

1.5681·rPR¥0.3615·rO¥0.0018·rPR·rO 

(B) rO > 89 ....................................................... 7.88 + 1.4080·rPR 

(ii) 30 < rPR < 104.7 ......................................... (A) 26.7 < rO ≤ 89 ............................................ 41.9435 + 1.505·rPR¥0.5823·rO + 

0.005562·rPR·rO 

(B) rO > 89 ....................................................... ¥9.88 + 2.0·rPR 

(iii) rPR ≥ 104.7 ................................................. All ...................................................................... 32 + 1.6·rPR 

§ 1031.90 Supersonic engines. 

The following standards apply to new 

engines installed in supersonic 

airplanes: 

(a) Smoke. (1) Engines of a type or 

model for which the date of 

manufacture was on or after January 1, 

1984, may not have a characteristic level 

for smoke number exceeding an 

emission standard that is the lesser of 50 

or the following: 

SN = 83.6·rO¥0.274 

(2) [Reserved] 

(b) [Reserved] 

(c) HC. Engines of a type or model for 

which the date of manufacture was on 

or after January 1, 1984, may not have 

a characteristic level for HC exceeding 

the following emission standard in g/kN 

rated output: 

HC = 140·0.92rPR 

(d) CO. Engines of a type or model for 

which the date of manufacture was on 

or after July 18, 2012, may not have a 

characteristic level for CO exceeding the 

following emission standard in g/kN 

rated output: 

CO = 4550·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·rPR 

§ 1031.130 Derivative engines for 

emissions certification purposes. 

(a) Overview. FAA may approve a 

type certificate holder’s request for an 

engine configuration to be considered a 

derivative engine for emission purposes 

under this part if the type certificate 

holder demonstrates the engine 

configuration is similar in design to a 

previously certificated (original) engine 

for purposes of compliance with 

exhaust emission standards and at least 

one of the following circumstances 

applies: 

(1) The FAA determines that a safety 

issue requires an engine modification. 

(2) All regulated emissions from the 

proposed derivative engine are lower 

than the corresponding emissions from 

the previously certificated engine. 

(3) The FAA determines that the 

proposed derivative engine’s emissions 

are similar to the previously certificated 

engine’s emissions as described in 

paragraph (c) of this section. 

(b) Determining emission rates. To 

determine new emission rates for a 

derivative engine for demonstrating 

compliance with emission standards 

under § 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 


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previously certificated engine, including 

those approved for previous derivative 

engines. 

(c) Emissions similarity. (1) A 

proposed derivative engine’s emissions 

are similar to the previously certificated 

engine’s emissions if the type certificate 

holder demonstrates that the engine 

meets the applicable emission standards 

and differ from the previously 

certificated engine’s emissions only 

within the following ranges: 

(i) ±3.0 g/kN for NOX. 

(ii) ±1.0 g/kN for HC. 

(iii) ±5.0 g/kN for CO. 

(iv) ±2.0 SN for smoke number. 

(v) The following values apply for 

nvPMMC: 

(A) ±200 mg/m∧3 if the characteristic 

level of maximum nvPMMC is below 

1,000 mg/m∧3. 

(B) ±20% of the characteristic level if 

the characteristic level for maximum 

nvPMMC is at or above 1,000 mg/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 × 10∧14 particles/kN if the 

characteristic level for nvPMnum

emissions is below 2 × 10∧15 particles/ 

kN. 

(B) ±20% of the characteristic level if 

the characteristic level for nvPMnum

emissions is greater than or equal to 2 

× 10∧15 particles/kN. 

(2) In unusual circumstances, the 

FAA may adjust the ranges specified in 

paragraph (c)(1) of this section to 

evaluate a proposed derivative engine, 

after consulting with the EPA. 

§ 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 

§ 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 gearboxmounted 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 § 1031.140(E)—LTO TEST CYCLES

Mode 

Subsonic Supersonic 

Turboprop Turbojet and turbofan 

Percent of rO Time in mode 

(minutes) Percent of rO Time in mode 

(minutes) Percent of rO Time in mode (minutes) 

Take-off .................................................... 100 0.5 100 0.7 100 1.2 

Climb ........................................................ 90 2.5 85 2.2 65 2.0 

Descent .................................................... NA NA NA NA 15 1.2 

Approach .................................................. 30 4.5 30 4.0 34 2.3 

Taxi/ground idle ....................................... 7 26.0 7 26.0 5.8 26.0 

(f) Pollutant-specific test provisions. 

Use the following provisions to 

demonstrate whether engines meet the 

applicable standards: 

(1) Smoke number. Use the equipment 

and procedures specified in ICAO 

Appendix 2 and ICAO Appendix 6. Test 

the engine at sufficient thrust settings to 

determine and compute the maximum 

smoke number. 

(2) nvPM. Use the equipment and 

procedures specified in ICAO Appendix 

7 and ICAO Appendix 6, as applicable: 

(i) Maximum nvPM mass 

concentration. Test the engine at 

sufficient thrust settings to determine 

and compute the maximum nvPM mass 

concentration produced by the engine at 

any thrust setting, according to the 

procedures of ICAO Appendix 7. 

(ii) LTO nvPM mass and number. Test 

the engine at sufficient thrust settings to 

determine the engine’s nvPM mass and 

nvPM number at the rated output 

identified in table 1 to paragraph (e) of 

this section. 

(3) HC, CO, and NOX. Use the 

equipment and procedures specified in 

ICAO Appendix 3, ICAO Appendix 5, 

and ICAO Appendix 6, as applicable. 

Test the engine at sufficient thrust 

settings to determine the engine’s HC, 

CO, and NOX emissions at the rated 

output identified in table 1 to paragraph 

(e) of this section. 

(4) CO2. Calculate CO2 emission 

values from fuel mass flow rate 

measurements in ICAO Appendix 3 and 

ICAO Appendix 5 or, alternatively, 

according to the CO2 measurement 

criteria in ICAO Appendix 3 and ICAO 

Appendix 5. 

(g) Characteristic level. The 

compliance demonstration consists of 

establishing a mean value from testing 

some number of engines, then 

calculating a ‘‘characteristic level’’ by 

applying a set of statistical factors in 

ICAO Appendix 6 that take into account 

the number of engines tested. Round 

each characteristic level to the same 

number of decimal places as the 

corresponding standard. Engines 


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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 

§ 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 submodel 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 submodel, where more than one type of 

combustor is available. 

(4) The calendar-year production 

volume of engines from the sub-model 

that are covered by an FAA type 

certificate. Record zero for sub-models 

with no engines manufactured during 

the calendar year, or state that the 

engine model is no longer in production 

and list the date of manufacture (month 

and year) of the last engine 

manufactured. Specify the number of 

these engines that are intended for use 

on new aircraft and the number that are 

intended for use as non-exempt engines 

on in-use aircraft. For engines delivered 

without a final sub-model status and for 

which the manufacturer has not 

ascertained the engine’s sub-model 

when installed before submitting its 

production report, the manufacturer 

may do any of the following in its initial 

report, and amend it later: 

(i) List the sub-model that was 

shipped or the most probable submodel. 

(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 submodel 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. 

§ 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. 

§ 1031.170 Confidential business 

information. 

The provisions of 40 CFR 1068.10 

apply for information you consider 

confidential. 

Subpart D—Reference Information 

§ 1031.200 Abbreviations. 

The abbreviations used in this part 

have the following meanings: 

° 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 

Mg microgram 

NOX oxides of nitrogen 

Num number 

nvPM nonvolatile particulate matter 

nvPMmass nonvolatile particulate 

matter mass 

nvPMnum nonvolatile particulate 

matter number 

nvPMMC nonvolatile particulate matter 

mass concentration 


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rO rated output 

rPR rated pressure ratio 

SN smoke number 

§ 1031.205 Definitions. 

The following definitions apply to 

this part. Any terms not defined in this 

section have the meaning given in the 

Clean Air Act (42 U.S.C. 7401–7671q). 

The definitions follow: 

Aircraft has the meaning given in 14 

CFR 1.1, a device that is used or 

intended to be used for flight in the air. 

Aircraft engine means a propulsion 

engine that is installed on or that is 

manufactured for installation on an 

airplane for which certification under 

14 CFR is sought. 

Aircraft gas turbine engine means a 

turboprop, turbojet, or turbofan aircraft 

engine. 

Airplane has the meaning given in 14 

CFR 1.1, an engine-driven fixed-wing 

aircraft heavier than air, that is 

supported in flight by the dynamic 

reaction of the air against its wings. 

Characteristic level has the meaning 

given in Appendix 6 of ICAO Annex 16 

(incorporated by reference, see 

§ 1031.210). The characteristic level is a 

calculated emission level for each 

pollutant based on a statistical 

assessment of measured emissions from 

multiple tests. 

Date of manufacture means the date 

on which a manufacturer is issued 

documentation by FAA (or other 

recognized airworthiness authority for 

engines certificated outside the United 

States) attesting that the given engine 

conforms to all applicable requirements. 

This date may not be earlier than the 

date on which engine assembly is 

complete. Where the manufacturer does 

not obtain such documentation from 

FAA (or other recognized airworthiness 

authority for engines certificated outside 

the United States), date of manufacture 

means the date of final engine assembly. 

Derivative engine for emissions 

certification purposes means an engine 

that has the same or similar emissions 

characteristics as an engine covered by 

a U.S. type certificate issued under 14 

CFR part 33. These characteristics are 

specified in § 1031.130. 

Designated EPA Program Officer 

means the Director of the Assessment 

and Standards Division, 2000 

Traverwood Drive, Ann Arbor, 

Michigan 48105. 

Emission index means the quantity of 

pollutant emitted per unit of fuel mass 

used. 

Engine model means an engine 

manufacturer’s designation for an 

engine grouping of engines and/or 

engine sub-models within a single 

engine type certificate family, where 

such engines have similar design, 

including being similar with respect to 

the core engine and combustor designs. 

Engine sub-model means a 

designation for a grouping of engines 

with essentially identical design, 

especially with respect to the core 

engine and combustor designs and other 

emission-related features. Engines from 

an engine sub-model must be contained 

within a single engine model. For 

purposes of this part, an original engine 

model configuration is considered a 

sub-model. For example, if a 

manufacturer initially produces an 

engine model designated ABC and later 

introduces a new sub-model ABC–1, the 

engine model consists of two submodels: ABC and ABC–1. 

Engine type certificate family means a 

group of engines (comprising one or 

more engine models, including submodels 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 § 1031.11 and that the term 

‘‘except’’ has its plain meaning in other 

contexts. 

Exempt means to allow, through a 

formal case-by-case process, an engine 

to be certificated and sold that does not 

meet the applicable standards of this 

part. 

Exhaust emissions means substances 

emitted to the atmosphere from exhaust 

discharge nozzles, as measured by the 

test procedures specified in § 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 

§ 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 °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 

§ 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 § 1031.11. 

Standard day conditions means the 

following ambient conditions: 

Temperature = 15 °C, specific humidity 

= 0.00634 kg H2O/kg dry air, and 

pressure = 101.325 kPa. 

Subsonic means relating to an aircraft 

that has not been certificated under 14 

CFR to exceed Mach 1 in normal 

operation. 

Supersonic airplane means an 

airplane for which the maximum 

operating limit speed exceeds a Mach 

number of 1. 

System losses means the loss of 

particles during transport through a 

sampling or measurement system 

component or due to instrument 

performance. Sampling and 

measurement system loss is due to 

various deposition mechanisms, some of 

which are particle-size dependent. 

Determining an engine’s actual emission 

rate depends on correcting for system 

losses in the nvPM measurement. 

Turbofan engine means a gas turbine 

engine designed to create its propulsion 

from exhaust gases and from air that 

bypasses the combustion process and is 

accelerated in a ducted space between 

the inner (core) engine case and the 

outer engine fan casing. 

Turbojet engine means a gas turbine 

engine that is designed to create its 

propulsion entirely from exhaust gases. 

Turboprop engine means a gas turbine 

engine that is designed to create most of 


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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. 

§ 1031.210 Incorporation by reference. 

(a) Certain material is incorporated by 

reference into this part with the 

approval of the Director of the Federal 

Register under 5 U.S.C. 552(a) and 1 

CFR part 51. To enforce any edition 

other than that specified in this section, 

the Environmental Protection Agency 

must publish a document in the Federal 

Register and the material must be 

available to the public. All approved 

material is available for inspection at 

U.S. EPA, Air and Radiation Docket 

Center, WJC West Building, Room 3334, 

1301 Constitution Ave NW, 

Washington, DC 20004, www.epa.gov/ 

dockets, (202) 202–1744, and is 

available from the sources listed in this 

section. It is also available for 

inspection at the National Archives and 

Records Administration (NARA). For 

information on the availability of this 

material at NARA, email fr.inspection@

nara.gov or go to www.archives.gov/ 

federal-register/cfr/ibr-locations.html. 

(b) International Civil Aviation 

Organization, Document Sales Unit, 999 

University Street, Montreal, Quebec, 

Canada H3C 5H7, (514) 954–8022, 

www.icao.int, or sales@icao.int. 

(1) Annex 16 to the Convention on 

International Civil Aviation, 

Environmental Protection, as follows: 

(i) Volume II—Aircraft Engine 

Emissions, Fourth Edition, July 2017, 

Including Amendment 10 of January 1, 

2021 (as indicated in footnoted pages). 

IBR approved for §§ 1031.140 and 

1031.205. 

(ii) [Reserved] 

(2) [Reserved] 

[FR Doc. 2022–01150 Filed 2–2–22; 8:45 am] 

BILLING CODE 6560–50–P 


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