[Federal Register Volume 89, Number 33 (Friday, February 16, 2024)]
[Rules and Regulations]
[Pages 12634-12663]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-02330]



[[Page 12633]]

Vol. 89

Friday,

No. 33

February 16, 2024

Part IV





 Department of Transportation





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 Federal Aviation Administration





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14 CFR Parts 21, 38, 121, et al.





Airplane Fuel Efficiency Certification; Final Rule

  Federal Register / Vol. 89, No. 33 / Friday, February 16, 2024 / 
Rules and Regulations  

[[Page 12634]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21, 38, 121, and 125

[Docket No.: FAA-2022-0241 Amdt. No. 121-391, 125-75, 38-1, 21-107]
RIN 2120-AL54


Airplane Fuel Efficiency Certification

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Final rule.

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SUMMARY: This action adopts fuel efficiency requirements for 
certification of certain airplanes. These certification requirements 
implement the emissions standards adopted by the Environmental 
Protection Agency (EPA) to allow manufacturers to certificate their 
airplanes for fuel efficiency in the United States. This action also 
fulfills the FAA's Clean Air Act obligations to enforce implementation 
of EPA's aircraft emissions standards for greenhouse gas emissions.

DATES: Effective April 16, 2024.
    The incorporation by reference of a certain publication listed in 
this rule is approved by the Director of the Federal Register as of 
April 16, 2024.

ADDRESSES: For information on where to obtain copies of rulemaking 
documents and other information related to this final rule, see ``How 
to Obtain Additional Information'' in the SUPPLEMENTARY INFORMATION 
section of this document.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this action, contact Ralph Iovinelli, Office of Policy, International 
Affairs, & Environment, Emissions Division (AEE-300), Federal Aviation 
Administration, 800 Independence Avenue SW, Washington, DC 20591; 
telephone 202-267-3566; email [email protected].

SUPPLEMENTARY INFORMATION:

I. Executive Summary

A. Purpose of the Regulatory Action

    As a signatory State to the Chicago Convention, the United States 
must establish minimum standards consistent with those prescribed by 
the International Civil Aviation Organization (ICAO) on a wide range of 
aviation-related matters, including aircraft emissions, or file a 
difference. The United States' adoption of the 2017 ICAO carbon dioxide 
(CO2) emission standards for certain airplanes aligns United 
States law with the ICAO standards.
    Moreover, the Clean Air Act Amendments of 1970 (Clean Air Act) 
direct the U.S. Environmental Protection Agency (EPA) to adopt 
standards applicable to the emission of any air pollutant from any 
class of aircraft engines. The Clean Air Act also directs the Secretary 
of Transportation (and by delegation, the Administrator of the FAA) to 
implement the standards adopted by the EPA.\1\ On January 11, 2021, the 
EPA published a final rule adopting new domestic airplane greenhouse 
gas (GHG) emissions standards in 40 Code of Federal Regulations (CFR) 
part 1030.\2\ As required by the Clean Air Act \3\, the FAA is 
implementing those EPA standards through this final rule by adopting 
new certification regulations in 14 CFR part 38 for fuel efficiency for 
certain covered airplanes. The applicability of these regulations and 
the regulatory emissions limits are the same as those adopted by ICAO 
in its airplane CO2 emission standards.
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    \1\ ``The Secretary of Transportation, after consultation with 
the Administrator, shall prescribe regulations to insure compliance 
with all standards prescribed under section 7571 of this title by 
the Administrator. The regulations of the Secretary of 
Transportation shall include provisions making such standards 
applicable in the issuance, amendment, modification, suspension, or 
revocation of any certificate authorized by part A of subtitle VII 
of title 49 or the Department of Transportation Act.'' 42 U.S.C. 
7572
    \2\ Federal Register Vol. 86, No. 6, Final Rule, 40 CFR parts 87 
and 1030 ``Control of Air Pollution from Airplanes and Airplane 
Engines: GHG Emission Standards and Test Procedures,'' Environmental 
Protection Agency, pp. 2136-2174.
    \3\ 42 U.S.C. 7571
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    This rulemaking establishes fuel efficiency certification 
requirements for certain subsonic jet airplanes with a maximum takeoff 
mass greater than 5,700 kilograms and for certain propeller-driven 
airplanes with a maximum takeoff mass greater than 8,618 kilograms. 
Under this final rule, an airplane is subject to these certification 
requirements: (1) at new (original) type certification; (2) upon 
manufacture of any covered airplane after January 1, 2028; or (3) when 
a modification to a covered airplane meets change criteria specified in 
the regulations. This rulemaking excepts from applicability airplanes 
used for firefighting, amphibious airplanes, airplanes lower than 
specific masses, reciprocating engine airplanes, non-pressurized 
airplanes, and certain specialized operations airplanes.
    For covered airplanes, a certification applicant must demonstrate 
that the airplane meets these new part 38 requirements. The new part 38 
requirements established by this rulemaking prescribe fuel efficiency 
limits, which are the emission standards adopted by the EPA. This 
rulemaking expresses fuel efficiency limits as maximum permitted fuel 
efficiency metric (FEM) values that are determined by the maximum 
takeoff mass of the airplane. Thus, the applicant must determine an FEM 
value to demonstrate compliance against the applicable fuel efficiency 
limit. The two certifiable components of the FEM are the specific air 
range (SAR) and the reference geometric factor (RGF). The SAR 
represents the distance an airplane can travel per unit of fuel 
consumed and is determined by direct flight test measurement or use of 
a validated performance model. The RGF is a representation of airplane 
fuselage size based on the floor area of pressurized space in an 
airplane. The technical detail needed to determine the FEM value of an 
airplane is included in Appendix A to part 38. An applicant must 
receive FAA approval for all information the applicant uses to 
calculate the FEM value of an airplane. To comply with part 38, the FEM 
value must not exceed the airplane's applicable fuel efficiency limit.
    In addition, to fully implement the EPA standards through the FAA's 
certification process, this rulemaking makes corresponding changes to 
the FAA certification procedures in part 21 to include compliance with 
part 38 as a certification requirement. Moreover, this rulemaking 
requires that the FEM value of the airplane, along with other part 38 
compliance information, be placed in an FAA-approved section of the 
flight manual of the airplane.
    The FAA's adoption of these certification requirements implements 
the emissions standards adopted by the EPA, allows manufacturers to 
certificate their airplane for fuel efficiency in the United States, 
and fulfills the statutory obligations of the FAA under the Clean Air 
Act. The FAA's promulgation of this Airplane Fuel Efficiency regulation 
is the final step for the United States in implementing the 2017 ICAO 
carbon dioxide (CO2) emission standards for certain 
airplanes promulgated in Annex 16 Volume III under the Chicago 
Convention.

B. Changes Made in This Final Rule

    The FAA has adopted part 38 and sections of parts 21, 121, and 125 
largely as they were proposed in a notice of proposed rulemaking (NPRM) 
that was published on June 15, 2022.\4\
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    \4\ Federal Register Vol. 87, No. 115, Notice of Proposed 
Rulemaking, 14 CFR parts 21, 38, 121, and 125 ``Airplane Fuel 
Efficiency Certification,'' Federal Aviation Administration, pp. 
36076-36091.

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[[Page 12635]]

    The FAA considered the public comments it received on its proposal 
and the adopted rule reflects consideration of those comments. The FAA 
received over 60 comments on the NPRM, ranging from suggested 
typographical and grammatical edits to substantive comments on proposed 
regulatory text and language in the NPRM preamble. As a result of these 
comments, the FAA made changes throughout the regulatory text. For 
instance, the FAA revised the language in the applicability and change 
criteria sections (Sec. Sec.  38.1 and 38.19) to clarify the 
applicability of part 38 to newly built airplanes and modifications to 
airplanes. These revisions clarify this final rule is not applicable to 
modifications of in-service airplanes that have not previously shown 
compliance to part 38 prior to the modification, except for 
manufacturers who are required to comply with part 38 for in-production 
airplanes that have not received their first certificate of 
airworthiness as provided in the applicability section of this rule. 
The FAA also made edits to several technical requirements in Appendix A 
(e.g., center of gravity, airplane weight, fuel samples, flight test 
procedures, and calculations and corrections of test data). Revisions 
to sections within parts 21 and 121 include: the inadvertent omission 
of the reference to these new fuel efficiency certification 
requirements in the certification provisions (Sec.  21.21), consistency 
edits (Sec.  21.93), and correction of an error (Sec.  121.141).

II. Authority for This Rulemaking

    The FAA's authority to issue rules on aviation safety is found in 
Title 49 of the United States Code (49 U.S.C.). Subtitle I, Section 106 
describes the authority of the FAA Administrator.
    The Clean Air Act, 42 U.S.C. 7572, authorizes the Secretary of 
Transportation to implement aviation emission standards adopted by the 
EPA to insure compliance with the same. Furthermore, 49 CFR 1.83(c) 
delegates to the FAA Administrator the authority to carry out the 
functions of this section of the Clean Air Act.
    This rulemaking adopts regulations to insure compliance with the 
standards adopted by the EPA under the Clean Air Act in 40 CFR part 
1030 to control the emissions of certain GHG emissions from airplanes. 
This rulemaking is issued under the authority described in 42 U.S.C. 
7572 and 49 CFR 1.83(c).

III. Background

A. General Background

    As a signatory State to the Chicago Convention, the United States 
must establish minimum standards consistent with those prescribed by 
ICAO or file a difference with ICAO if the United States' standards 
differ from them in any particular respect. The Committee on Aviation 
Environmental Protection (CAEP) is a technical committee of the ICAO 
Council that assists in formulating ICAO policy and adopting Standards 
and Recommended Practices related to aircraft noise and emissions. The 
FAA represents the United States on CAEP, attending annual Steering 
Group meetings and CAEP triennial meetings, and contributing technical 
expertise to CAEP's many working groups. The EPA serves as an advisor 
to the United States member of CAEP at the annual and triennial 
meetings and contributes technical expertise to the FAA and CAEP's 
working groups on aviation emissions, pollution control technology, and 
environmental policy. Within CAEP, the FAA assists and advises the EPA 
on aviation-specific environmental issues, airplane and engine 
technologies, and airworthiness certification matters.
    In 2009, the ICAO Council and its Group on International Aviation 
and Climate Change (GIACC) developed a ``Programme of Action'' to limit 
or reduce the impact of aviation on the climate. The program's ``basket 
of measures'' included the reduction of the carbon footprint of 
international civil aviation, beginning with the development of a 
technology-based certification standard for CO2 emissions 
from subsonic airplanes.
    The CO2 standard-setting process included input from 
governments, airplane and engine manufacturers, non-governmental 
environmental organizations, research institutions, and academics 
worldwide. The standard-setting process occurred in two 3-year phases. 
The first phase focused on the development of the CO2 
certification requirement (i.e., a CO2 metric, test 
procedures, and measurement methodology). The second phase focused on 
the development of the CO2 standard itself (i.e., 
establishing regulatory limits, applicability, and assessments of cost 
effectiveness). The principles and key criteria that guided the process 
included the concepts that:

--No certification requirements should be imposed that compromise 
airplane safety;
--Airplane CO2 emissions should be reduced through the 
integration of fuel efficient technologies in airplane type designs;
--Airplanes that incorporate differing generations of CO2 
reduction technologies should be treated fairly and equitably;
--Any adopted standard should be independent of airplane size, purpose 
or utilization;
--The metric used should be robust and minimize unintended airplane and 
system design consequences;
--Any adopted standard should use industry standard practices of 
measurement and correction; and
--The implementation of any adopted standard should reflect a 
manageable and appropriate level of resources to be expended by 
national airworthiness authorities and manufacturers.

    In February 2016, CAEP agreed on a new CO2 emission 
standard for certain airplanes. ICAO adopted this new standard, set out 
in Annex 16, Volume III, in March 2017.\5\
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    \5\ Annex 16 to the Convention on International Civil Aviation, 
Environmental Protection, Volume III, ``Aeroplane CO2 Emissions,'' 
First Edition, July 2017. https://store.icao.int/collections/annex-16-environmental-protection/products/annex-16-environmental-protection-volume-iii-aeroplane-co2-emissions.
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    In the United States, the Clean Air Act directs the EPA to adopt 
standards applicable to the emission of any air pollutant from any 
class of aircraft engines, which in the EPA Administrator's judgment 
causes, or contributes to, air pollution which may reasonably be 
anticipated to endanger public health or welfare. The Clean Air Act 
also directs the Secretary of Transportation (and by delegation, the 
Administrator of the FAA) to implement the standards adopted by the 
EPA. The FAA implements these EPA standards by prescribing regulations 
in title 14 CFR that require the certification of aircraft and aircraft 
engines to the EPA standards.
    On January 11, 2021, the EPA published a final rule \6\ adopting 
new domestic airplane GHG emission standards in 40 CFR part 1030. In 
accordance with the Clean Air Act, the FAA is adopting new 
certification regulations for certain airplanes to insure compliance 
with the EPA standards. The FAA also supports the adoption of these 
standards because they are aligned with the principles and key criteria 
that guided the ICAO process. The applicability of these

[[Page 12636]]

regulations and the regulatory emissions limits in the United States 
are the same as those adopted by ICAO as its airplane CO2 
emission standard in Annex 16, Volume III.
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    \6\ Federal Register Vol. 86, No. 6, Final Rule, 40 CFR parts 87 
and 1030 ``Control of Air Pollution from Airplanes and Airplane 
Engines: GHG Emission Standards and Test Procedures,'' Environmental 
Protection Agency, pp. 2136-2174.
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    The FAA, EPA, and ICAO each use different terminology to reference 
the same standards. In Annex 16 Volume III, ICAO references its 
standard as CO2 emissions because the amount of 
CO2 emitted is directly proportional to the amount of fuel 
burned by an airplane at cruise speed and altitude. ``Airplane 
CO2 emissions'' is a commonly used term that fits well 
within ICAO's international goals to reduce the carbon footprint of 
aviation. More specifically, Part II of Annex 16 Volume III is titled 
``Certification Standard for Aeroplane CO2 Emissions Based 
on the Consumption of Fuel.''
    Domestically, the EPA issued an endangerment finding for GHG 
emissions from airplane engines,\7\ which, in turn, required the EPA to 
issue GHG standards for airplane engines. The EPA rule establishes 
standards for GHGs in recognition of airplane engine emissions of 
CO2 and another GHG, nitrous oxide (N2O).\8\ The 
EPA did not set limits on N2O emissions, noting that they 
are small and are proportionally reduced as fuel consumption is 
reduced. Accordingly, the EPA adopted the fuel efficiency metric 
established by ICAO, which effectively limits both CO2 and 
N2O GHGs emitted by airplane engines.
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    \7\ Federal Register Vol. 81, No. 7, Final Rule, 40 CFR parts 87 
and 1068 ``Finding that Greenhouse Gas Emissions From Aircraft Cause 
or Contribute to Air Pollution That May be Reasonably Be Anticipated 
To Endanger Public Health and Welfare.'' Environmental Protection 
Agency pp. 54422-54475.
    \8\ Both CO2 and N2O are constituents of 
EPA's defined term ``greenhouse gases,'' which means an air 
pollutant that is the aggregate group of six greenhouse gases: 
CO2, N2O, methane, hydrofluorocarbons, 
perfluorocarbons, and sulfur hexafluoride. See 40 CFR 1030.105.
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    The FAA describes these same limits and procedures as measures of 
fuel efficiency, since this final rule prescribes a measurement of 
airplane performance determined by the SAR parameter to determine fuel 
efficiency. This measurement is akin to the fuel-burn-based ICAO 
standard. The FAA intends that the fuel efficiency standards be the 
same as the standards that the EPA adopted in 40 CFR part 1030.
    In summary, it is the FAA's intent that the three standards--FAA's 
fuel efficiency regulations in 14 CFR part 38, the EPA's GHG emission 
standards in 40 CFR part 1030, and ICAO's CO2 emissions 
standards--be considered equivalent for purposes of implementation.
    The FAA is making final guidance material for part 38 available at 
the same time as this final rule and has placed the final Advisory 
Circular 38 (AC38) in the docket.

B. Summary of the NPRM

    On June 15, 2022, the FAA published the NPRM titled ``Airplane Fuel 
Efficiency Certification.'' At the same time, the FAA also posted for 
comment in the NPRM docket draft guidance material for the proposal in 
the form of a draft AC38.
    In its NPRM, the FAA proposed the adoption of the EPA's GHG 
standards as fuel efficiency standards for airplanes in a new 14 CFR 
part 38. The FAA-proposed standards would impose requirements when an 
applicant seeks type certification. In general, the proposal applied to 
certain subsonic jet airplanes and certain propeller-driven airplanes 
above a specified mass. The FAA's proposal also provided for use of the 
existing part 11 exemption process.
    Importantly, the NPRM provided the requirements for determining the 
fuel efficiency value for subsonic airplanes at certification. The 
proposal then established fuel efficiency limits as adopted by the EPA. 
For an airplane, the fuel efficiency limit would be based on a fuel 
efficiency value calculated using two primary parameters: the SAR and 
the RGF. The FAA proposal included an Appendix A, which contained the 
technical detail needed to determine the FEM value. For an airplane to 
comply with part 38, under the NPRM, the FEM value could not exceed the 
applicable fuel efficiency limit.
    In addition, to fully implement the EPA standards through the FAA's 
certification process, for applicable airplanes the proposal included 
amendments to part 21 to include compliance with part 38, and to the 
operating regulations to ensure that flight manuals contained fuel 
efficiency certification information. The FAA solicited public comments 
on the NPRM and draft AC38 for a period of 61 days. The comment period 
on the NPRM closed on August 15, 2022.

C. General Overview of Comments

    The FAA received 62 comments on the NPRM and the draft AC38. One of 
these comments was received and considered after the comment period 
closed.
    Most comments were from individuals. In addition, the agency 
received comments from several airplane and engine manufacturers and 
industry groups: Aerospace Industries Association (AIA), Airbus, 
Airlines for America (A4A), Airlines Pilots Association (ALPA), Avions 
de Transport Regional (ATR), Boeing, Embraer S.A. (Embraer), FedEx 
Corporation (FedEx), General Electric Aviation (GE), General Aviation 
Manufacturers Association (GAMA), Gulfstream Aerospace Corporation 
(Gulfstream), Modification and Replacement Parts Association (MARPA), 
National Business Aviation Association (NBAA), and the Port of Seattle.
    The FAA received nine comments generally supporting the rule as 
proposed. These commenters included ALPA, ATR, Port of Seattle, and 
some individuals. Fourteen commenters, including Boeing, AIA, A4A, 
Airbus, FedEx, GE, MARPA, Gulfstream, NBAA, GAMA, Embraer, and some 
individuals supported the rule generally but offered requests for 
clarifications, changes, or additional provisions. The FAA received 
comments from 39 individuals who opposed the proposed rule.
    The commenters raised overarching issues on the NPRM related to the 
FAA's authority to issue the rule, the applicability of the rule, and 
potential costs of the rule. Commenters also requested clarifications 
and raised several technical issues. A discussion of comments 
requesting specific clarifications, changes, or revisions to the NPRM 
and the FAA's responses to these requests is in Section IV, 
``Discussion of Comments and the Final Rule.''

IV. Discussion of Comments and the Final Rule

    The following summarizes the comments received to the NPRM and the 
FAA's responses to these comments.

A. FAA's Part 38 Authority

    Comments: Several individuals commented that the proposed rule 
exceeded the FAA's authority or was otherwise unnecessary for a wide 
variety of reasons. Conversely, other commenters indicated the proposed 
rule is needed to allow manufacturers to certificate their airplanes 
for fuel efficiency in the United States and would fulfill the FAA's 
Clean Air Act statutory obligations.
    Response: The FAA disagrees with those commenters who indicated 
that the FAA exceeded its authority or that the rule was unnecessary. 
The proposed rule falls well within the FAA's statutory mandate and is 
required by Section 7572 of the Clean Air Act. The Clean Air Act vests 
authority to regulate airplane emissions with both the EPA and the FAA. 
Section 7571 of the Clean

[[Page 12637]]

Air Act directs the EPA to adopt standards applicable to the emission 
of any air pollutant from any class of aircraft engines, which in the 
EPA Administrator's judgment causes, or contributes to, air pollution 
that may reasonably be anticipated to endanger public health or 
welfare. Further, the EPA must consult with the FAA on these aircraft 
engine emissions standards. The EPA adopts these standards in title 40 
of the CFR.
    After the EPA adopts the standards, section 7572 of the Clean Air 
Act directs the Secretary of Transportation (and by delegation, the 
Administrator of the FAA) \9\ to implement the standards adopted by the 
EPA. The FAA implements these standards by adopting regulations in 
title 14 of the CFR that allow the certification of aircraft and 
aircraft engines to the EPA standards. In addition, the proposed rule 
is consistent with the FAA's own statutes (49 U.S.C. 106) that 
authorize the Administrator to issue regulations.
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    \9\ Boeing commented that the proposed rule should update the 
DOT regulations in 49 CFR 1.83(c) that delegate this authority to 
the FAA Administrator to reflect the new 40 CFR part 1030. Paragraph 
1.83(c) delegates to FAA the authority to implement the standards 
adopted by the EPA under 42 U.S.C. 7572. The FAA does not have the 
authority to amend 49 CFR 1.83(c) but will raise the issue to DOT.
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    On January 11, 2021,\10\ the EPA published a final rule adopting 
GHG emissions standards applicable to certain aircraft engines and 
airplanes in 40 CFR part 1030. In accordance with the mandate under 
Section 7572, the FAA adopts this rule through new certification 
regulations in part 38 for certain airplanes to insure compliance with 
the EPA standards in 40 CFR part 1030.
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    \10\ Federal Register Vol. 86, No. 6, Final Rule, 40 CFR parts 
87 and 1030 ``Control of Air Pollution from Airplanes and Airplane 
Engines: GHG Emission Standards and Test Procedures,'' Environmental 
Protection Agency, pp. 2136-2174.
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B. FAA's Role in Establishing Fuel Efficiency Standards

    Comments: Several commenters opined that the proposal was 
unrealistic or that the FAA was ``simply bowing to'' the EPA. Others 
said that the FAA should focus on other matters, such as safety.
    Response: As described in the ``General Background,'' the FAA and 
the EPA both participated heavily in the ICAO working group and CAEP 
that established ICAO's Aeroplane CO2 standard. Other 
entities also provided significant input into the process, including 
the affected global aviation industry and many other representatives. 
The standard that ICAO ultimately established was based on a process 
that considered views from all participants. This process resulted in 
the adoption of technology-following certification requirements that 
also prevent backsliding to less fuel-efficient airplanes. For the same 
reasons articulated in the principles and key criteria that guided the 
ICAO standard development process, the FAA supported and continues to 
support the adoption of the ICAO and EPA standards.
    Finally, as described in ``FAA's Part 38 Authority,'' the FAA is 
statutorily obligated to adopt the EPA standard.
    Comments: Other commenters suggested that the goals of the proposed 
regulation may already be met by the existing body of regulations or 
that industry was already incentivized to achieve fuel efficiency 
through market forces or otherwise. Some suggested that the industry 
had already achieved low emissions.
    Response: The CO2 standard-setting process at ICAO 
included input from many stakeholders, including airplane and engine 
manufacturers. In addition, the FAA received comments from several 
airplane and engine manufacturers, including Boeing, Gulfstream, 
Airbus, GE, Embraer, and ATR, as well as industry groups that represent 
the broader aviation manufacturers and airlines such as GAMA, AIA, A4A, 
and NBAA. In their comments on the proposed rule, these entities 
recognized the domestic and international need of expeditiously 
adopting these standards in order to establish a global fuel efficiency 
certification scheme for airplanes. The aviation industry has shown 
strong support for the standard, which is the first aviation standard 
aimed at improving airplane fuel efficiency and reducing CO2 
emissions.

C. Consideration of Other Alternatives

    Comment: A number of comments went beyond the scope of the proposed 
rule to suggest that the FAA should instead consider alternative means 
of achieving decreased CO2 emissions, such as adding a tax on fuel 
sales; increasing airplane registration fees; changing flight 
procedures; creating incentives to encourage operators to purchase 
newer, more fuel-efficient airplanes; restricting business jets; 
developing alternative fuels; or increasing the availability of 
alternative fuels. Other commenters indicated that the rule was not 
going far enough to improve fuel efficiency.
    Response: The FAA reiterates that part 38 is consistent with the 
FAA's authority under its own statutes and the Clean Air Act. In 
particular, the purpose of this rule is to implement EPA's GHG 
standards through the FAA certification process. Comments received 
requesting that FAA take an alternative approach to address fuel 
efficiency are not within the scope of the proposed rule.\11\
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    \11\ In California v. EPA, a number of states and environmental 
organizations challenged EPA's adoption of the standards in 40 CFR 
part 1030. The District of Columbia Circuit Court of Appeals held 
that the rule was within EPA's authority under 42 U.S.C. 7571 and 
that the agency reasonably explained its decision to harmonize its 
regulation with the ICAO standards. The Court also held that as the 
EPA had made the policy choice to align with ICAO standards, the EPA 
did not have a need to examine alternatives departing from the ICAO 
standards. 72 F.4th 308 (D.C. Cir. 2023).
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    Comment: Other commenters were concerned that the proposed rule 
would result in manufacturers' transitioning to alternative fuels, such 
as biofuels, or wanted clarity on the applicability of the proposed 
rule to hybrid airplanes or airplanes using alternative fuels.
    Response: This rule is a technology-based standard, aiming at 
measuring the performance of the airplane in terms of fuel efficiency, 
predicated on the ability of manufacturers to improve engine propulsion 
efficiency, aerodynamics, and airplane weight--all elements of the SAR 
parameter in the FEM. Neither the SAR nor the RGF parameters are 
affected by the type of fuel used in the airplane. Therefore, the FEM 
value does not change based on the fuel used in the airplane.
    As a general matter, the rule could apply to any airplanes meeting 
the applicability criteria of Sec.  38.1, including hybrids or those 
using alternative fuels as long as those fuel(s) meet the applicable 
specifications in Appendix A. The FAA wants to clarify that the use of 
alternative fuels does not exempt covered airplanes from compliance 
with this rule.

D. General Applicability (Sec.  38.1(a) and (b))

    In the NPRM, the FAA proposed that part 38 would apply to certain 
subsonic jet airplanes and propeller-driven airplanes at three 
applicability points. These three points are airplanes (1) receiving 
original type certification on or after January 11, 2021; (2) 
manufactured after January 1, 2028, regardless of the date of type 
certification; and (3) type-certificated before the applicable 
compliance date but where a modification is made that would affect the 
fuel efficiency of the airplane after January 1, 2023.
1. Discussion of Final Rule
    The FAA adopts the applicability requirements for part 38 in Sec.  
38.1(a) and

[[Page 12638]]

(b). These paragraphs remain largely as proposed and have the same 
applicability as the EPA regulations. These paragraphs continue to 
provide for the applicability of these standards to certain subsonic 
jet airplanes and propeller-driven airplanes at three applicability 
points. After consideration of public comments, the FAA is revising the 
regulation to clarify the applicability of part 38 to the currently 
flying in-service airplanes as well as to proposed modifications to 
covered \12\ airplanes that have received their type certificate. The 
regulation was also revised to make some other non-substantive changes 
to the text. These changes are discussed in this section.
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    \12\ For the purpose of FAA's final rule, ``covered airplanes'' 
are defined the same as EPA's definition in their final rule: 
``Civil subsonic jet airplanes (those powered by turbojet or 
turbofan engines and with a MTOM greater than 5,700 kilograms), as 
well as larger civil subsonic propeller driven airplanes (those 
powered by turboprop engines and with a MTOM greater than 8,618 
kilograms).'' 86 FR 2136 (Jan. 11, 2021).
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    As developed by ICAO, the standards adopted by the EPA include 
three occasions on which an airplane becomes subject to the 40 CFR 1030 
standards. These same applicability points are included in Sec.  
38.1(a) and (b): (1) at new (original) type certification; (2) the 
manufacture of any covered airplane after January 1, 2028; or (3) a 
modification to a covered airplane that meets the change criteria of 
Sec.  38.19. These change criteria pertaining to airplane modifications 
are described in further detail in Sec.  38.19. The applicability 
points include:
     New (Original) Type Certification Applicability: 
Paragraphs 38.1(a)(1)-(3) describe airplanes whose applications for 
original type certification were submitted after January 11, 2021. 
Although the ICAO standard on which these regulations are based was 
effective on January 1, 2020, for certifications of new type designs, 
the effective date of the EPA regulation was January 11, 2021, for 
certifications of new type designs. Except for the effective date, the 
EPA and the FAA regulations have the same applicability as the ICAO 
standard. The difference in effective dates between the ICAO and EPA 
standards has no practical effect in the United States. In the twelve 
months between the effective date of the ICAO standard and the 
effective date of the EPA standards, the FAA received no applications 
for new type certification that would meet the applicability criteria 
of this rule. Although EPA's GHG emissions standards are now applicable 
in the United States through 40 CFR part 1030, the FAA did not receive 
an application for new type certification before the adoption of either 
EPA's rule or the FAA's rule. Once an airplane is type-certificated for 
fuel efficiency in accordance with this rule, all airplanes produced 
under that type certificate must comply with the fuel efficiency 
standards.
     Manufacture of covered airplanes after January 1, 2028: 
Paragraphs 38.1(a)(6)-(7) describe the second instance of applicability 
for covered airplanes manufactured after January 1, 2028. These 
paragraphs address covered airplanes that are newly built after January 
1, 2028, regardless of the date of type certification. Airplanes 
manufactured after this date would not be eligible for a first 
certificate of airworthiness unless compliance with part 38 has been 
shown.
     A modification to a covered airplane that meets the change 
criteria of Sec.  38.19: Paragraphs 38.1(a)(4)-(5) address 
modifications to covered airplanes whose type designs were not 
certified under this rule, where an application by the type certificate 
holder for a type design change is submitted on or after January 1, 
2023, and the first certificate of airworthiness is issued with the 
modified type design that exceeds the change criteria in Sec.  
38.19(c). In determining applicability under these paragraphs, a 
certification applicant must consider Sec.  38.1(b), which addresses 
modifications made to covered airplanes and directs the reader to the 
change criteria in Sec.  38.19. See section IV.N for a discussion on 
the change criteria in Sec.  38.19.
    As noted, the FAA made a few non-substantive changes to the 
applicability provisions. The FAA added levels of designation to 
paragraph (a)(1) at the suggestion of the Federal Register to help 
clarify the two independent applicability provisions in Sec.  
38.1(a)(1). The FAA also fixed a minor typographical error in Sec.  
38.1(a)(6)(ii) and changed the order of the agencies identified in 
Sec.  38.1(a)(4) to reflect that the FAA is issuing this rule.
2. Public Comments and FAA Response
    Comments: Multiple commenters, such as A4A, AIA, Boeing, Airbus, 
FedEx, NBAA, and some individuals, requested clarification that the 
rule would not apply to in-service airplanes, consistent with the 
related EPA regulation and the applicable ICAO standard. These 
comments, summarized in the following sentences, included specific 
statements and questions related to the applicability of the rule to 
current in-service airplanes and modifications to such airplanes. 
Boeing requested clarity that individual in-service airplanes, whose 
type designs have not been previously certificated to part 38, and to 
which modifications are made by the owners/operators or other third 
parties, do not need to demonstrate compliance with part 38. Similarly, 
some of the commenters, including A4A, Airbus, and Boeing, requested 
that the FAA clarify the part 38 applicability provisions regarding 
modified type designs and modified versions of airplanes to more 
clearly state that part 38 applies only when a type-certificate holder 
changes the type design of an airplane mid-production by applying for 
FAA approval of a modified type design. To clarify these concepts, the 
AIA, A4A, Airbus, and Boeing specifically requested that the FAA modify 
Sec.  38.1(a)(4)(iii) and (a)(5)(iii) to add ``by the holder of the 
type certificate'' to explain that a third party would not be required 
to show compliance to part 38 when requesting a supplemental type 
certificate that aims to modify one or more individual in-service 
airplanes.
    In addition, Airbus requested that the FAA clarify the regulatory 
text in Sec.  38.1(b) by changing ``prior version'' to ``prior non-
modified version'' to emphasize that the prior version of the airplane 
is the one that does not include the modification.
    Response: The FAA intends this rule to have the same applicability 
as the related EPA regulation and the ICAO standard. As such, this 
final rule is not applicable to current in-service airplanes. Where a 
type certificate holder submits an application for a change in type 
design after January 1, 2023, and the change meets the requirements of 
Sec.  38.19(c), part 38 will apply to a newly built airplane 
incorporating this change in order to receive its first certificate of 
airworthiness. After January 1, 2028, part 38 will apply to all newly 
built airplanes receiving their first certificate of airworthiness.
    The FAA recognizes that determining the applicability of this rule 
to a specific airplane requires consideration of multiple sections in 
part 38. Although Sec.  38.1 addresses applicability in general, when 
an applicant requests a change in type design, it must also consider 
Sec.  38.19's change criteria to determine the applicability of part 
38. Sections 38.1(a)(1) through (3) address newly built airplanes whose 
applications for original type certification were submitted after the 
specified dates. Sections 38.1(a)(4) and (5) provide applicability 
requirements for a modified version of an airplane whose type design 
was not certificated under part 38. Further, Sec.  38.1(a)(4) and (5)

[[Page 12639]]

relate to a newly built airplane, receiving its first certificate of 
airworthiness, based on a type design change submitted by the type 
certificate holder on or after January 1, 2023, that exceeds the change 
criteria in Sec.  38.19(c). On or after January 1, 2028, all newly 
built covered airplanes that meet the requirements of Sec.  38.1(a)(6) 
and (7) must comply with part 38 to receive their first certificate of 
airworthiness.
    Section 38.1(b) makes the important connection to the Sec.  38.19 
change criteria. In Sec.  38.1(b), part 38 applies to an airplane where 
an applicant requests a change in type design that meets the change 
criteria of Sec.  38.19. Airplanes that have demonstrated compliance to 
this rule (i.e., those that do not fall in Sec.  38.1(a)(4) and (5)) 
and subsequently undergo modifications will need to re-demonstrate 
compliance according to the change criteria shown in Sec.  38.19(a) and 
(b).
    With the applicability context described in the previous 
paragraphs, the FAA agrees to revise the proposed Sec. Sec.  38.1 and 
38.19 to clarify part 38 applicability to individual in-service 
airplanes and modifications to airplanes. The FAA recognizes that Sec.  
38.1(a)(4)(iii) and (5)(iii) in the NPRM may have been interpreted, as 
commenters suggested, to require compliance with part 38 for any 
modifications to an airplane, even a currently in-service airplane. The 
FAA does not intend this applicability. This final rule slightly 
updates these paragraphs to clarify that this specific set of 
applicability requirements are for applications for a change in type 
design made by the type certificate holder. Specifically, in response 
to comments requesting clarity on modifications to airplanes under 
these specific applicability requirements, this rule revises Sec.  
38.1(a)(4)(iii) and (5)(iii) to state that compliance is required when 
``an application by the type certificate holder for a type design 
change is submitted on or after January 1, 2023.'' In combination with 
the rest of the requirements under Sec.  38.1(a)(4) and (5), the part 
38 now reads clearly that it does not apply to a type design change 
application for a currently in-service airplane that has not previously 
shown compliance to part 38. Only a newly built airplane with a change 
in type design by the type certificate holder, applied for on or after 
January 1, 2023, and exceeding change criteria in Sec.  38.19(c), would 
be required to comply with part 38. Therefore, the final rule clarifies 
that part 38 does not apply to currently in-service airplanes, 
including modifications, and instead focuses on newly built airplanes 
that incorporate modifications.
    Further, in proposed Sec.  38.1(a)(4)(iv) and (a)(5)(iv), the words 
``for an airplane built'' were redundant with the introductory text of 
Sec.  38.1(a)(4) and (5), which already stated, ``A subsonic jet 
airplane--'' and ``A propeller-driven airplane--'', respectively. To 
correct this redundancy, this final rule removes ``for an airplane 
built'' from Sec.  38.1(a)(4)(iv) and (a)(5)(iv). Also, this change is 
consistent with other changes FAA made to Sec.  38.1(a)(4) and (5) to 
clarify to the applicability. This change does not alter the meaning of 
the paragraph.
    For consistency with and to fully respond to the comments on Sec.  
38.1(a), the FAA updates the proposed Sec.  38.1(b) to reflect that 
part 38 applies to modifications that are based on an application for a 
change in type design and meet the change criteria of Sec.  38.19. As 
part of these updates, the FAA moves the Sec.  38.19 reference earlier 
in the paragraph to incorporate the change criteria more clearly in 
Sec.  38.1(b). Also, the FAA revises Sec.  38.1(b) to explicitly state 
that the applicability is tied to an application for a change in the 
type design. This better aligns with the text of Sec.  38.1(a)(4) and 
(5).
    In response to Airbus' request that to change ``prior version'' to 
``prior non-modified version,'' the FAA recognizes that ``prior 
version'' of an airplane may not have been described with sufficient 
detail. Based on these considerations, this rule also revises Sec.  
38.1(b) for consistency with Sec.  38.1(a) to more accurately describe 
the state of an airplane before or after modifications, rather than 
using ``prior version,'' and to highlight the connection to the change 
criteria in Sec.  38.19.
    Finally, because Sec.  38.19(b) and (c) also use ``prior version,'' 
this rule makes similar consistency changes to these paragraphs.
    In summary, these edits to Sec. Sec.  38.1(a) and (b) and 38.19(b) 
and (c) clarify that part 38 does not apply to current in-service 
airplanes.
    Comments: Airbus, A4A, and Boeing also recommended that table 1 in 
the NPRM be clarified to avoid the implication that part 38 be applied 
to in-service airplanes.
    Response: In lieu of providing an updated table 1 from the NPRM to 
provide a quick reference for applicability with examples, the FAA has 
provided a much more detailed discussion here to clarify applicability 
of part 38 to in-service airplanes in this section.
    Comments: Similar to comments requesting clarity on prior version 
of an airplane, Boeing, AIA, and A4A requested a definition of 
``subsequent version,'' a term that appears in Sec.  38.19, to clarify 
that modifications to individual in-service airplanes do not require 
application of the fuel efficiency standards.
    Response: This rule's changes to Sec.  38.1 address the fact that 
current in-service airplanes, or modification to such airplanes, do not 
require compliance with this rule. Therefore, the FAA does not see a 
need to add a definition for the term ``subsequent version.''
    Comments: Boeing requested that the FAA add a definition of 
``modified type design,'' which is used in Sec.  38.1(a)(4)(iv) and 
(5)(iv), because it was concerned that the lack of a definition could 
create potential ambiguity when the text is read together with the 
well-established aircraft certification regulations in part 21 that 
address `changes in type design.'
    Response: The FAA notes that the term ``modified type design'' in 
the context of Sec.  38.1(a)(4)(iv) and (5)(iv), where it appears, 
refers to the final modified configuration of an airplane receiving its 
first certificate of airworthiness.
    The FAA is using the word modified for consistency with EPA's 
regulations. For the purposes of part 38, the FAA uses the words 
``changed'' and ``modified'' interchangeably.
    Comment: Airbus recommended that the four (4) applicability 
requirements listed under Sec.  38.1(a)(4) and (a)(5) should be joined 
by adding the conjunction ``and'' after each individual requirement to 
clarify that applicability to this rule consists of all four 
requirements in total.
    Response: The FAA reviewed the grammatical structure of Sec.  
38.1(a)(4) and (a)(5). As proposed, the four applicability requirements 
listed under each of these sections are separated by a semicolon in a 
list from (i) to (iv) with the conjunction ``and'' between the final 
two provisions (iii) and (iv), signifying that the ``and'' applies to 
all requirements in this list. This format follows the Office of the 
Federal Register (OFR) formatting practices, and, therefore, the 
repetition of ``and'' between each requirement is not required. The FAA 
believes this is the correct structure and will not incorporate 
Airbus's recommendation to add an ``and'' after each requirement.
    Comment: Airbus further commented on several items such as changing 
the following text from the proposed rule: ``. . . an application . . 
.'' to ``. . . the application . . .'' in paragraph (a)(4)(iii); ``. . 
. type design is submitted . . .'' to ``. . . type design was submitted 
. . .'' in paragraph (a)(4)(iii);

[[Page 12640]]

and ``. . . for an airplane built . . .'' to ``. . . for that airplane 
built . . .'' in paragraph (a)(4)(iv).
    Response: The FAA does not agree with these suggestions. The FAA 
wrote this rule to apply to a wide range of civil airplanes and 
changing words to ``that airplane'' or ``the application'' adds a level 
of specificity that is not needed for this rule. The suggested change 
to ``for that airplane built with'' is not necessary because the FAA 
removed this phrase from Sec. Sec.  38.1(a)(4)(iv) and (a)(5)(iv) in 
response to previously addressed comments. Regarding the change from 
``is'' to ``was,'' the FAA notes that the verb tense of this rule is 
written in present tense.
    Comment: Airbus commented on Sec.  38.1(a)(6) and (a)(7) that the 
words ``An individual . . .'' should be added to the beginning of these 
applicability paragraphs to reinforce that these requirements apply to 
individual airplanes. Airbus states this would be similar to the 
applicability language in ICAO Annex 16 Vol III, Part II, Chapter 2, 
Sec.  2.1.1(f)&(g).
    Response: The applicability language in Sec.  38.1(a)(6) and (a)(7) 
has the same meaning as the ICAO Annex 16 Vol III language even if the 
terminology is slightly different. The applicability language in Sec.  
38.1(a)(6) and (a)(7) is written in singular form starting with: ``A 
subsonic jet airplane . . .'' and ``A propeller-driven airplane . . .'' 
that has ``Its first certificate of airworthiness issued on or after 
January 1, 2028.'' The word ``a'' already places the subject in 
singular form that clearly represents an individual airplane, which is 
consistent with the ICAO Annex 16 Vol III. For these reasons, it is not 
necessary to reinforce that these paragraphs apply to ``individual'' 
airplanes.
    Comment: The GAMA commented that the applicability requirements for 
propellor-driven airplanes with maximum takeoff mass (MTOM) greater 
than 8,618 kilograms (kg), as used in the proposed rule, could include 
airplanes with maximum takeoff weight (MTOW) greater than 18,999.45 lbs 
when 8,618 kilograms are converted to pounds. The GAMA noted that the 
mathematical conversion of an MTOM of 8,618 kg equates to 18,999.45 
lbs, which is less then what is used for the MTOW limits of parts 21 
and 23 for normal category airplanes. Therefore, the GAMA argues the 
proposed part 38 fuel efficiency standards would apply to FAA type 
certificated part 23 airplanes at the maximum allowable MTOW of 19,000 
lbs. The GAMA suggested two alternative approaches to address this 
potential unit conversion issue in Sec.  38.1 MTOM references: (1) use 
8,619 kg in all instances for MTOM threshold for propeller-driven 
airplanes instead of 8,618 kg; or (2) list both the applicable MTOM 
(mass) of 8,618 kg and MTOW (weight) 19,000 lbs.
    Response: The FAA acknowledges that conversion from 8,618 kg to lbs 
equates to a weight that is approximately 0.5 lbs less than the 19,000 
lbs threshold of other FAA regulations. However, when applying the 
conversion in reverse, going from 19,000 lbs to kg, the result is 0.25 
kg greater than 8,618 kg. This difference of less than 1 lb or 1 kg is 
extremely small; it is unlikely that an airplane would fall within this 
conversion difference. Importantly, differences less than 1 lb or 1 kg 
would not be reflected in either a TCDS or an airplane flight manual. 
Additionally, the use of kilograms as the applicability threshold is 
consistent with the EPA standards. For these reasons, the FAA finalizes 
the threshold as proposed in Sec.  38.1(a)(3)(i).
    Comments: The MARPA requested that the FAA clarify that part 38 
does not apply to parts manufactured by holders of a Parts Manufacturer 
Approval (PMA). In particular, the MARPA asked that the FAA include 
text in the preamble to the final rule stating that the rule applies 
only to the design and approval of type certificated products. In 
addition, the MARPA wanted this text to also state that the proposed 
rule does not apply to Parts Manufacturer Approval (PMA) manufacturers 
of modification and replacement parts under part 21 subpart K.
    Response: The FAA disagrees with adding the suggested text to the 
preamble. The applicability section does not apply to parts 
manufactured by holders of a PMA. Because these parts have the same 
fit, form, and function of the parts they replace they are not 
considered a change in type design.
    Comment: One individual thought that this rule would benefit those 
who use private airplanes for travel, implicitly indicating that those 
types of planes would not need to comply with part 38.
    Response: The FAA disagrees as the applicability of this rule 
includes all airplanes that meet the applicability requirements 
regardless of who is using the airplane or whether they are privately 
owned. The type of airplanes described by the commenter are not 
necessarily exempted from the rule.

E. Exceptions to Applicability (Sec.  38.1)

    In the NPRM, the FAA proposed several exclusions to the 
applicability of part 38. Part 38 would not apply to airplanes with 
lesser MTOMs than those specified in Sec.  38.1(a). Part 38 also would 
exclude airplanes that are designed for specialized operations 
(including the presence of unique design features to carry out those 
operations). The NPRM also would exclude amphibious airplanes, 
airplanes that have no pressurized areas, airplanes designed for 
firefighting, and airplanes powered by reciprocating aircraft engines.
1. Discussion of the Final Rule
    In Sec.  38.1(c), the FAA is adopting the same exclusions to part 
38 that were adopted by the EPA and ICAO. The section is remaining as 
proposed, except for one minor non-substantive change in Sec.  
38.1(c)(4) where the FAA switched the EPA and FAA references so that 
the FAA is identified first as the agency is issuing this rule.
    As finalized, part 38 does not apply to airplanes with lower MTOMs 
than those specified in Sec.  38.1(a) and Sec.  38.1(c)(1) and (2)). 
The rule also excludes airplanes that are initially designed, or 
modified and used, for specialized operations (including the presence 
of unique design features to carry out those operations) from part 38, 
subject to a determination that a design for specialized operation is 
detrimental to fuel efficiency. The FAA and the EPA would make this 
determination at the time an airplane is presented for certification. 
Examples of such airplanes could include specialized cargo features, 
specialized missions, or crop dusting (Sec.  38.1(c)(4)). The rule 
excludes from part 38 the following: amphibious airplanes (as defined 
in Sec.  38.3); airplanes that have no pressurized areas (described as 
having zero reference geometric factor (RGF)); airplanes designed for, 
or modified and used for, firefighting; and airplanes powered by 
reciprocating aircraft engines (Sec.  38.1(c)(3), (5), (6), and (7)).
2. Public Comments and FAA Response
    Comments: Commenters, including Boeing and AIA (echoed by GE \13\), 
requested that the FAA clarify and revise the regulatory text to 
explicitly state that the rule only applies to civil airplanes and not 
military airplanes. The AIA specifically requested clarification that 
part 38 did not apply to state airplanes, such as those used by 
military, customs, and police services,

[[Page 12641]]

or other types of airplanes, such as rotorcraft or piston-engine 
airplanes. Boeing requested that the FAA clarify the language in Sec.  
38.1(a) so that the regulation explicitly stated that part 38 only 
applied to civil airplanes as defined in 14 CFR 1.1.
---------------------------------------------------------------------------

    \13\ GE specifically incorporated by reference Boeing's 
substantive, non-technical comments on the NPRM, including comments 
on the applicability to military aircraft and other requested 
changes for alignment with EPA and ICAO standards. GE also 
specifically incorporated by reference AIA's substantive comments on 
the proposed rule, including comments on the inapplicability of the 
rule to state aircraft and modifications to an in-service aircraft.
---------------------------------------------------------------------------

    Boeing further requested a change in Sec.  38.1(a) from original 
type certification to original civil certification. Boeing believed 
this change and other consistency changes would remove any ambiguity 
and clarify that only airplanes seeking civil certification are subject 
to the rule. GE supported Boeing and AIA comments on this issue.
    Response: The FAA disagrees with the request to explicitly revise 
the regulatory text to state that the rule only applies to civil 
airplanes and not military airplanes. This rule addresses the 
certification of fuel efficiency for subsonic, civil airplanes.\14\ As 
defined in 14 CFR 1.1, civil aircraft are aircraft other than public 
aircraft. Public aircraft is an operational status under the statute, 
not a certification status, since any airplane operated by a valid 
government entity could be a public aircraft depending on its use. 49 
U.S.C. 40102(a)(41), 40125. Because the FAA cannot predict whether a 
type certificated airplane may be used for a public aircraft operation, 
and the status of that airplane may change from civil to public and 
back on a flight-by-flight basis, the FAA finds that this distinction 
is not appropriate for purposes of this rule.
---------------------------------------------------------------------------

    \14\ 87 FR at 36082.
---------------------------------------------------------------------------

    Further, the FAA disagrees with Boeing's suggested change to 
original civil certification. The FAA does not reference its 
airworthiness certificates as ``civil certificates.'' The FAA uses 
terminology such as ``original type certificates,'' consistent with 
part 21.
    Thus, the FAA declines to modify Sec.  38.1 as suggested by 
commenters.
    Comments: Commenters also suggested the FAA clarify that part 38 
does not apply to airplanes that are initially certificated as civil 
airplanes during the production process but immediately used for 
military operations. Both AIA and Boeing explicitly requested that the 
FAA add these types of airplanes to the list of airplanes not covered 
by the rule in Sec.  38.1(c). Boeing also requested corresponding 
changes to the draft Advisory Circular. These commenters indicated that 
these changes are consistent with the ICAO standards. In particular, 
they referenced the ICAO Environmental Technical Manual (ETM) \15\ and 
its inclusion of these types of airplanes in a list of examples of 
specialized operational requirements. Because the FAA had included 
language in the NPRM to propose the same exclusions adopted by ICAO, 
Boeing stated the FAA should include language excluding these types of 
airplanes from coverage under part 38. Boeing stated the exception 
would be consistent with the examples for these airplanes in the ICAO 
guidelines (the ETM). Boeing also indicated that this exception would 
be consistent with past EPA and Department of Defense (DOD) practice, 
citing to the EPA's 2012 Final Rule adopting new aircraft engine 
emissions standards for nitrogen oxides.
---------------------------------------------------------------------------

    \15\ Volume III--Procedures for the CO2 Emissions 
Certification of Airplanes, Sec.  2.1.3.
---------------------------------------------------------------------------

    Response: Commenters indicated that to be consistent with the ICAO 
standards, the FAA needs to exclude from part 38 a civil-certificated 
airplane immediately converted to military use. The FAA disagrees with 
the underlying premise that part 38 does not apply to civil 
certificated airplanes immediately converted to military use. The FAA 
regulations are consistent with ICAO Annex 16 Volume III standards, 
which contain no such exemption. The ICAO language suggesting the 
exception of military airplanes from CO2 applicability is in 
ICAO guidance (i.e., the ETM guidance document to Annex 16 Volume III), 
not in the ICAO standards (i.e., Annex 16 Volume III).\16\ The FAA is 
not obligated to include in its standards any exception suggested in 
ICAO guidance that is not in the ICAO standard.
---------------------------------------------------------------------------

    \16\ The FAA inadvertently included guidance from ICAO's 
Environmental Technical Manual in the draft AC38 that was included 
in the docket for review with the NPRM. The exception has never been 
included in the part 38 rule text, and for the reasons discussed it 
has been removed from the final AC38.
---------------------------------------------------------------------------

    The FAA has no authority over military airplanes involved in public 
aircraft operations, and its regulations do not apply to airplanes 
produced for the armed services. The FAA certification regulations 
apply only to airplanes that seek civil certification in the United 
States. When an airplane is produced, the FAA issues an airworthiness 
certificate for that airplane if it conforms to the type design and 
complies with all applicable civil regulations. FAA regulations do not 
consider intended use or conversion involved in airplane 
certification--either the airplane complies with all regulatory 
requirements and is eligible for a civil airworthiness certificate, or 
it does not.
    A manufacturer may produce airplanes and parts for the military 
without involving the FAA. If an applicant requests civil certification 
from the FAA, the applicant must satisfy all applicable regulations for 
that airplane regardless of the potential for that airplane's use for 
military operations.
    In the United States, the FAA has no statutory authority over 
military airplanes involved in public aircraft operations. Part 38 does 
not apply to these airplanes; accordingly, these airplanes cannot be 
exempted or excluded from something that does not apply in the first 
place. For these reasons, the FAA does not see the need to modify Sec.  
38.1(c) in this respect.

F. Definitions (Sec.  38.3)

    In the NPRM, the FAA proposed several definitions for part 38. 
These definitions would be specific to fuel efficiency certification. 
The proposed definitions included: amphibious airplane; ICAO Annex 16, 
Volume III; maximum takeoff mass (MTOM); performance model; reference 
geometric factor (RGF); specific air range (SAR); subsonic; and type 
certificated maximum passenger seating capacity.
1. Discussion of the Final Rule
    The rule includes a definitions section as Sec.  38.3. The section 
is adopted, as proposed, except this rule makes modifications to the 
definition of maximum takeoff mass (MTOM) based on comments received.
2. Public Comments and FAA Response
    Comments: Some commenters suggest the FAA include additional 
definitions, such as ``subsequent version'' and ``modified type 
design.''
    Response: See responses to these comments that are discussed in 
section IV.D.
    Comments: The FAA received several comments on the definition of 
Maximum takeoff mass (MTOM) in Sec.  38.3. Specifically, Airbus 
commented that the definition of MTOM should be modified by replacing 
``maximum allowable'' with ``highest of all certified'' takeoff masses. 
Airbus stated that the proposed definition could be misinterpreted and 
suggested clarifying that the MTOM represents the highest of all of the 
certified takeoff masses in the Type Certificate Data Sheet (TCDS). 
Airbus also suggested replacing ``approved certification basis'' with 
``Type Certificate Data Sheet'' since the approved certification basis 
of a type design generally represents the set of applicable 
requirements to the type

[[Page 12642]]

design and it would be more exact to refer to the TCDS.
    Response: The FAA does not agree that ``highest of all certified'' 
should replace ``maximum allowable'' in the definition of MTOM. The 
MTOM is intended to mean the maximum takeoff mass an airplane type 
design is certified to and recorded in the TCDS. As mentioned by an 
individual commenter, the FAA agrees that the TCDS may contain several 
maximum takeoff masses for different variants of the same airplane type 
design, and the MTOM is the highest of these maximum takeoff masses. 
The comments reflected confusion around which maximum mass was meant--
maximum structural, maximum takeoff for an airplane, or the maximum 
mass of several variants of similar design. The FAA does recognize that 
the definition as proposed was not clear on this point and is changing 
``maximum allowable takeoff mass'' to ``maximum certified takeoff 
mass,'' which clarifies reference to certified MTOM values in the TCDS. 
The FAA also notes that the use of ``maximum certified takeoff weight'' 
(similar to maximum certified takeoff mass) is used in other parts of 
title 14 CFR, including parts 21, 25, and 36.
    Regarding the reference in the proposal to the ``approved 
certification basis'' and the requests to replace this phrase in the 
MTOM definition with ``TCDS,'' the FAA agrees that the TCDS is the 
appropriate document to reference in determining the maximum takeoff 
weight for FAA-certified variants of the base model. However, the FAA 
decided to remove ``approved certification basis'' from the regulatory 
text, and not replace it with ``TCDS,'' because the change to ``maximum 
certified takeoff mass,'' earlier in the definition addresses these 
concerns. Applicants may propose the use of the highest weight of an 
airplane type design to represent lower-weight variants. This allowance 
provides flexibility to applicants who may not be interested in 
certifying an individual FEM value for each lower weight variant. Such 
proposals will be considered on a case-by-case basis for FAA approval 
as provided in Sec.  38.23.
    Comment: Boeing commented that the FAA should revise its 
description of the MTOM definition to clarify that MTOM is not an 
international standard term for airplane weight expressed in kilograms. 
Boeing indicated that its expression in kilograms is not integral to 
its meaning. Boeing requested that the FAA revise its description to 
state that the MTOM is the highest of all takeoff masses for the type 
design configuration.
    Similarly, an individual commented that although MTOM needs to be 
expressed in kilograms for use in showing compliance with the proposed 
requirements, MTOM is not an international standard term for airplane 
weight expressed in kilograms. In addition, the commenter noted that 
MTOM is the highest maximum takeoff mass specified for the airplane 
type design as stated in the airplane TCDS, and that the TCDS may 
contain several maximum takeoff masses (identified as maximum takeoff 
weights in the TCDS) for different weight variants for the same 
airplane type design. The commenter concluded by stating that the MTOM 
is the highest of these maximum takeoff masses.
    Response: The FAA acknowledges that in the NPRM preamble the FAA 
described MTOM as the international standard term of airplane weight 
expressed in kilograms. The FAA recognizes that this statement is 
incorrect as MTOM is not an international standard term for airplane 
weight.
    The FAA made minor revisions for clarification and moved the 
reference to kilograms to be more closely associated with the relevant 
terms.
    As a result, the FAA has modified the definition of MTOM in this 
final rule to be:

The maximum certified takeoff mass, expressed in kilograms, for an 
airplane type design

    Comment: A commenter asked that the definition of MTOM include the 
phrase ``for the purposes of complying with the requirements of this 
part.''
    Response: The FAA notes that Sec.  38.3 already begins with the 
phrase, ``For the purpose of showing compliance with this part, the 
following terms have the specified meanings:.'' Based on that, the FAA 
has not changed the definition as suggested by the commenter.
    Comment: Airbus provided a comment on the definition of 
``Performance model'' stating that in the phrase ``using corrected 
flight test data that can be used to determine the specific air range 
values,'' the word ``corrected'' should be removed since test data in 
test conditions could also be used to validate a performance model.
    Response: The FAA disagrees with this change as it would cause a 
substantive difference between the FAA and the EPA and ICAO standards, 
both of which include the term ``corrected flight test data'' in the 
definition (See, e.g., 40 CFR 1030.105). A substantive difference would 
change the meaning, intent, or level of a particular requirement.

G. Compatibility With Airworthiness Requirements (Sec.  38.4)

    As proposed, this section addressed compatibility between 
environmental and airworthiness standards. The NPRM intended to 
prohibit the sequencing of certification tests for an airplane that has 
not met the applicability airworthiness requirements. This requirement 
would ensure that no airworthiness requirements are compromised during 
the fuel efficiency certification. In addition, the FAA proposed to 
require that all the procedures used to conduct the flights to 
demonstrate fuel efficiency compliance be conducted in compliance with 
all airworthiness regulations that apply to the airplane.
1. Discussion of the Final Rule
    The FAA received one comment on Sec.  38.4 regarding the sequencing 
of certification tests. The FAA did not make any changes to the section 
based on the comment and is adopting the section as proposed.
2. Public Comments and FAA Response
    Comment: Gulfstream asked if an applicant, when developing an aero-
propulsion model, could substantiate the score by conducting some of 
the testing (on a conforming test article) before 100% of airworthiness 
certification is complete.
    Response: The FAA recognizes that Gulfstream's comment was in 
response to a sentence in the NPRM preamble noting that Sec.  38.4 is 
intended to prohibit the sequencing of certification tests for an 
airplane that has not met the applicable airworthiness requirements. In 
response to Gulfstream's question, the FAA clarifies that testing could 
be done on a type design conforming test article before 100% of the 
airworthiness certification is complete. The airplane configuration 
conformed for fuel efficiency testing purposes must represent the 
configuration sufficiently such that the FEM is representative of the 
final type design. The FAA must approve configuration(s) not completely 
conforming to the type design prior to testing. The FAA did not revise 
the regulatory text based on this comment.

H. Exemptions (Sec.  38.5)

    In the NPRM, the FAA proposed a process for exemptions. The NPRM 
proposed that a petitioner submit petitions for exemption from any 
requirement in part 38 in accordance with 14 CFR part 11. The proposal 
also noted that the FAA would consult with the EPA on any request for 
exemption from the regulations of part 38. This proposed process is the 
same process

[[Page 12643]]

the FAA follows when it considers petitions for exemption from the 
engine emissions standards promulgated by the EPA under 40 CFR part 87 
and by the FAA in 14 CFR part 34.
1. Discussion of the Final Rule
    The FAA is adopting Sec.  38.5 as proposed. In accordance with 42 
U.S.C. 7572, 49 CFR 1.83(a)(6) and (c), and 49 U.S.C. 44701(f), the FAA 
may issue exemptions from its regulations when such exemption would be 
in the public interest. As adopted, Sec.  38.5 continues to provide for 
submittal of petitions for exemption from any requirement in part 38 in 
accordance with 14 CFR part 11. The FAA is adopting Sec.  38.5 as 
proposed.
2. Public Comments and FAA Response
    Comments: Some commenters, including AIA, A4A, Boeing, NBAA, and 
Airbus, expressed overall support for the FAA's approach to addressing 
exemption requests from part 38. In particular, Boeing supported the 
use of the public interest standard under 49 U.S.C. 44701 in 
considering exemptions. Several commenters requested clarity on the FAA 
process for exemptions in Sec.  38.5.
    Response: The FAA will follow its standard process for petitions 
for exemption that are outlined in 14 CFR part 11. Section 11.15 of 
these regulations defines a petition for exemption and Sec. Sec.  11.61 
through 11.103 contain the FAA's regulatory process for exemptions. 
Part of what must be included in a petition for exemption is an 
explanation of why the proposed action will be in the public interest 
(14 CFR 11.71). Section 38.5 adds a requirement to this process as it 
provides that the FAA consult with the EPA on each exemption petition 
before taking action. This process is the same as that followed when 
the FAA considers petitions for exemption from the engine emissions 
standards promulgated by the EPA under 40 CFR part 87 and by the FAA in 
14 CFR part 34.
    Comment: Airbus requested that the FAA provide information on the 
number of exemptions that could be granted and whether the FAA would 
follow the ICAO recommendations in granting exemptions.
    Response: How the FAA will process future exemptions under part 11 
and the possible number of exemptions the FAA could issue is outside 
the scope of this rulemaking. Although ICAO provides some guidance on 
exemptions that member countries could consider, the FAA processes each 
request for exemption on a case-by-case basis.

I. Incorporation by Reference (Sec.  38.7)

    In the NPRM, the FAA noted that it was reserving Sec.  38.7 for 
materials to be incorporated by reference into part 38. As part of the 
final rule development, FAA assessed the references to external 
documents throughout the proposed rule and is incorporating by 
reference ICAO Doc 7488/3, Manual of the ICAO Standard Atmosphere 
(extended to 80 kilometres (262 500 feet)), 1993 (Manual) in Sec.  
38.7. The Manual was identified in the part 38 Appendix and the FAA did 
not receive any comments on the Manual. Specifically, this Manual is 
referenced in sections A38.2.1.3.1, A38.5.2.2.1.9, and A38.5.2.2.1.10 
of Appendix A to part 38. In these sections, the applicant must use 
this Manual to establish certain reference specifications when 
determining SAR.
    The OFR has regulations concerning incorporation by reference (1 
CFR part 51). These regulations require that, for a final rule, 
agencies must discuss in the preamble the way in which the materials 
that the agency incorporated by reference are reasonably available to 
interested persons, and how interested parties can obtain the 
materials. In addition, in accordance with 1 CFR 51.5(b), the agency 
must summarize the material in the preamble of the final rule.
    In accordance with the OFR's requirements, the Manual provides the 
standard values of atmospheric parameters, the values of constants and 
coefficients, and the underlying equations used in the calculation of 
the atmospheric parameters. The Manual is intended for use in 
calculations in the design of airplanes, in presenting test results of 
airplanes and their components under identical conditions, and in 
facilitating standardization in the development and calibration of 
instruments.
    Interested persons can purchase this Manual from the ICAO Store at 
999 Robert-Bourassa Boulevard Montr[eacute]al (Quebec) Canada H3C 5H7, 
(www.store.icao.int).

J. Relationship to Other Regulations (Sec.  38.9)

    Section 38.9 in the proposed rule described the authority of the 
EPA and the FAA under the Clean Air Act to set and implement standards 
for aircraft engine emissions. In proposed Sec.  38.9, if the EPA 
changed any requirement in 40 CFR part 1030 that corresponded with a 
regulation in part 38, applicants could request a waiver for provisions 
as they appear in part 38 to comply with the changes; proposed Sec.  
38.9 also described the circumstances under which a waiver may be 
granted.
    This proposed section also provided that, unless otherwise 
specified in this part, all terminology and abbreviations in part 38, 
that are defined in 40 CFR part 1030, have the same meaning as 
specified in part 1030.
    The FAA did not receive comments on this section. However, the FAA 
did make some corrections to the text, including fixing a typographical 
error and an incorrect reference to the DOT delegations of authority to 
the FAA. Other than these corrections, the FAA is adopting this section 
as proposed.

K. Fuel Efficiency Metric (Sec.  38.11)

    The NPRM proposed that the fuel efficiency of an airplane be 
determined by the amount of fuel it uses to travel a certain distance 
under prescribed conditions. This measure was proposed as the fuel 
efficiency metric (FEM). As proposed, for each airplane subject to part 
38 (including an airplane subject to the change criteria of Sec.  
38.19), Sec.  38.11 would require the calculation of an FEM value using 
an equation identical to the one adopted by the EPA in 40 CFR 1030.20.
1. Discussion of the Final Rule
    The FAA is adopting Sec.  38.11 as proposed. This section describes 
the FEM of an airplane. The FEM value is calculated using an equation 
identical to the one adopted by the EPA. The two primary components of 
the FEM are the SAR (provided in Sec.  38.13) and the RGF (provided in 
Sec.  38.15). As described in Sec.  38.11, the FEM is ultimately 
calculated by dividing the average SAR values by RGF in a universal 
equation to denote the fuel efficiency of any airplane in a manner that 
is transport capability neutral.
2. Public Comments and FAA Response
    Comment: Gulfstream commented that the NPRM preamble description 
for Sec.  38.11 was confusing and highly simplified when it stated that 
dividing SAR by RGF results in a universal equation to denote the fuel 
efficiency of any airplane regardless of size.
    Response: The FAA notes that the preamble is not meant to reflect 
every detail of the rule, but rather summarizes its contents and 
elaborates as necessary. The statement was referring to the fuel 
efficiency metric equation, provided in Sec.  38.11, which is (1/
SAR)average divided by RGF\0.24\. In describing it as a 
universal equation, the FAA was referring to the fact that these 
parameters also comprise the metric in ICAO's international Aeroplane 
CO2 Emissions standard.

[[Page 12644]]

    Comment: An individual commented that the FEM seems to be defined 
upside down because the higher the fuel efficiency value gets, the 
worse the airplane is, efficiency-wise.
    Response: The term ``Fuel Efficiency Metric'' (FEM), as used in 
this rule, is not a measure of airplane fuel efficiency, as commonly 
understood. This rule uses a newly defined term, FEM, that represents a 
correlation to the level of GHG emissions produced by the airplane.
    The ICAO designed the FEM system (the FEM metric plotted against 
MTOM) similarly to other ICAO environmental standards, where the FEM of 
an airplane must be below a limit line to pass the standard. In order 
to achieve this result, the parameter SAR was inversed (i.e., 1/SAR).

L. Specific Air Range (Sec.  38.13)

    Section 38.13 of the NPRM proposed the requirements for determining 
SAR, one of the two primary components of the FEM.
1. Discussion of the Final Rule
    As adopted, Section 38.13 describes the SAR. The SAR is an 
aeronautical parameter used in the aviation industry to represent the 
distance an airplane can travel per unit of fuel consumed. In part 38 
it is used to represent the instantaneous fuel efficiency of an 
airplane at any point during stable cruise flight. The FAA made one 
minor revision to Sec.  38.13(a)(2)(ii) by replacing ``made'' with 
``submitted'' to be consistent with the FAA's intent. The FAA made a 
second minor revision to add the word ``or'' after Sec.  38.13(a)(1) to 
indicate the requirements more clearly. Otherwise, the FAA is adopting 
this section as proposed.
2. Public Comments and FAA Response
    Comment: Boeing suggested that Sec.  38.13(b), as proposed, could 
be overbroad and subject to misinterpretation as it could limit SAR 
calculations until the performance model is approved by the FAA. Boeing 
requested that the FAA change ``are made'' to ``are submitted.''
    Response: The FAA agrees that this requirement could be read to 
mean applicants may not make SAR calculations, whether for compliance 
or not, until the performance model is approved by the FAA. That was 
not the intent of this requirement. In the final regulatory text, the 
word ``made'' is changed to ``submitted.''
    Comment: Boeing commented that the SAR should be multiplied by the 
airplane's instantaneous weight in order to be used as a measurement of 
fuel efficiency. Boeing suggested clarifying that in part 38, the term 
``efficiency'' is used to represent the instantaneous fuel efficiency 
of an airplane at any point during stable cruise flight. Other 
individual commenters agreed with Boeing's assertion that SAR alone 
does not measure the fuel efficiency of an airplane.
    Response: The FAA recognizes that the parameter SAR does not 
``measure'' the instantaneous fuel efficiency. As stated above, SAR is 
the distance an airplane can travel per unit of fuel consumed to 
represent instantaneous fuel efficiency. Inherently, the determination 
of instantaneous SAR already includes the instantaneous weight of the 
airplane (i.e., structural efficiency in context of this rule), as well 
as the airplane aerodynamic and propulsive efficiencies of the 
airplane. The FAA agrees that, in this part, SAR is used to represent 
the instantaneous fuel efficiency of an airplane at any point during 
stable cruise flight.
    Comment: Gulfstream requested clarification of the FAA's 
expectations for substantiation of the performance model and allowances 
for weight increases.
    Response: Although models may be built with first principles 
analysis or wind tunnel data, the model used to show compliance must be 
validated by flight test data and approved by the FAA. The FAA must 
also approve any allowances regarding models. See section 38.13. The 
AC38 contains additional related guidance.
    Comment: An individual commenter questioned the need for the 
statement to exclude auxiliary power units (APU) from the 1/SAR 
calculation in Sec.  38.13(c), stating that they would not normally 
need to be included. The commenter noted that if there was ever a 
design where they did need to be included for some reason, this 
requirement would preclude that. Another commenter said that APU usage 
for traditional airplanes should be included because the goal is to 
reduce the consumption of hydrocarbons rather than potentially shifting 
the location where hydrocarbons are burned from a place where they are 
included to one where they are not.
    Response: Section 38.13 specifically excludes APUs from the SAR 
calculation. The EPA's standard in 40 CFR 1030.23 also contains this 
exclusion and this is a key component of the standards. To comply with 
42 U.S.C. 7572 and maintain consistency with EPA's standards in 40 CFR 
part 1030, the FAA is adopting this paragraph as proposed.

M. Reference Geometric Factor (Sec.  38.15)

    Section 38.15 of the NPRM proposed the requirements for determining 
RGF, one of the two primary components of the FEM.
1. Discussion of the Final Rule
    As adopted, Sec.  38.15 describes the RGF. The RGF is a 
representation of airplane fuselage size based on the floor area of 
pressurized space in an airplane and is flexible enough to account for 
single or multi-deck airplanes. This rule adopts changes from 
``cockpit'' to ``flight deck'' to provide gender-neutral language 
without changing the meaning or intent. Other than this change, the FAA 
is adopting this section as proposed.
2. Public Comments and FAA Response
    Comments: Some commenters, including A4A and Boeing, requested 
clarifications on FAA's descriptions of the RGF. Specifically, they 
requested that the preamble state that the RGF is a representation of 
airplane fuselage size based on the floor area of pressurized space in 
an airplane and is flexible enough to account for single or multi-deck 
airplanes. They further stated that dividing SAR by RGF results in a 
universal equation to denote the fuel efficiency of any airplane in a 
manner that is transport capability neutral (which is the FEM). Boeing 
stated that this change was needed because RGF was not developed to 
account for productivity and load carrying capability, noting that RGF 
was included to achieve the aim of having a transport-capability-
neutral metric.
    Response: The FAA agrees with A4A and Boeing's characterization of 
RGF, specifically its purpose to create a transport capability neutral 
FEM, and the FAA believes the regulatory text is consistent with this 
description. As a result, FAA has determined that no changes to Sec.  
38.15 are necessary based on this comment.
    Comment: An individual commenter questioned the appropriateness of 
RGF. The commenter proposed an example to show that a poorly designed 
airplane could have a similar FEM value as a better-designed airplane. 
The commenter also questioned the value of the RGF concept when 
passengers or payload transported over a given distance, per unit of 
energy input could be considered instead.
    Response: The FAA disagrees. A specific goal of the standards are 
to avoid unintentionally incentivizing airplane manufacturers to design 
airplanes for specific operational objectives, such as payload-carrying

[[Page 12645]]

capability or mission range. The RGF is not intended to account for an 
airplane's transport capabilities (e.g., its productivity or payload-
carrying capability). Instead, the use of RGF in this regulation 
creates a transport capability neutral fuel efficiency metric. The FAA 
asserts that RGF is appropriate.
    The FEM system is designed to account for aerodynamic, structural 
(i.e., airplane weight), and propulsive efficiencies using its SAR 
parameter, and utilizes RGF to normalize those efficiencies across a 
broad range of MTOMs. If two airplanes have the same efficiencies in 
these three categories as well as in RGF, as described in the 
commenter's example, then the FEM will be the same--regardless of 
whether the interior layout or sub-weight components of MTOM result in 
a poor design with respect to a particular operational purpose.

N. Fuel Efficiency Regulatory Limits (Sec.  38.17)

    As proposed, Sec.  38.17 incorporated, as fuel efficiency limits, 
the emission standards adopted by the EPA in 40 CFR 1030.30. Airplanes 
subject to part 38 would be required to demonstrate that the FEM value 
does not exceed the fuel efficiency limits in Sec.  38.17. Using the 
applicable provision in Sec.  38.1, the NPRM proposed calculating the 
fuel efficiency limit using the airplane's MTOM and the equations 
listed in the last column of the table in Sec.  38.17(b).
    The FAA did not receive comments on this section and is adopting it 
as proposed.

O. Change Criteria (Sec.  38.19)

    As proposed, this section would apply the fuel efficiency 
requirement at the time certain modifications were made. The NPRM would 
adopt the EPA airplane change criteria of 40 CFR 1030.35. The change 
criteria proposed in Sec.  38.19 described the modifications affecting 
compliance. The requirements differ depending on whether or not the 
airplane had previously demonstrated compliance with part 38.
1. Discussion of the Final Rule
    Section 38.19 provides the change criteria for modified airplanes. 
Section 38.19 adopts the EPA airplane change criteria of 40 CFR 
1030.35.
    As discussed in section IV.D. of this preamble, the third occasion 
when part 38 applies is at the time certain modifications are made to 
the airplane. Airplanes routinely have modifications incorporated into 
their designs. A modification may require demonstration of compliance 
to part 38, regardless of whether the airplane was required to 
previously demonstrate compliance with part 38.
    The change criteria in Sec.  38.19 describe the modifications which 
require compliance with part 38. The requirements differ depending on 
whether an airplane demonstrated compliance with part 38 before a 
modification is made, or whether an airplane was type certificated 
before January 1, 2023, and had not previously demonstrated compliance 
to this rule. The change criteria in Sec.  38.19(a) indicates that a 
compliance demonstration to this new rule is required if a modification 
to an airplane, that has been shown to comply with Sec.  38.17, will 
increase the MTOM of the airplane as written in Sec.  38.19(a)(1) or 
increases the FEM value above the thresholds provided in Sec.  
38.19(a)(2)(i) through (iii). Where an airplane has been shown to 
comply with Sec.  38.17, for a modification that does not increase 
either the MTOM or the FEM value, then under section Sec.  38.19(b) the 
airplane may retain the same FEM value as prior to modification. The 
last piece of the change criteria in Sec.  38.19(c) provides that an 
airplane, which meets the applicability provisions of Sec.  38.1(a)(4) 
or (5) on or after January 1, 2023, and before January 1, 2028, must 
demonstrate compliance if the incorporated modifications exceed 1.5% 
when comparing its FEM before and after the modifications.
    The FAA received several comments on this section. Some of these 
comments were directly related to Sec.  38.1 because of the 
relationship between the regulatory text of Sec. Sec.  38.1 and 38.19. 
As such, the FAA responded to some of the Sec.  38.19 comments in the 
related applicability responses (see IV.D. General Applicability). As a 
result of FAA responses to those comments in the general applicability 
discussion, FAA made changes to Sec.  38.19(b) and (c). As a result of 
other comments, the FAA made minor clarification changes to Sec.  
38.19(a)(2)(i) and (ii) and (b). Other than these changes, the FAA 
adopts the section as proposed.
    The FAA recognized that the change criteria as proposed in the NPRM 
may have been difficult to understand because it described the change 
criteria thresholds as ``values'' that could be confused with fuel 
efficiency metric ``values'' described in Sec.  38.11. The FAA made 
minor edits to the text in Sec.  38.19(a) to remove the potential for 
confusion by properly describing the change criteria as a threshold 
whereby changes in fuel efficiency metric values are compared to the 
thresholds in percentages.
2. Public Comments and FAA Response
    Comment: Several commenters, including Embraer, Boeing, AIA, and 
Airbus, commented on Sec.  38.19(b) that the text ``this paragraph 
(b)'' should say ``paragraph (a) of this section.''
    Response: The FAA agrees that this was a typographical error and 
has corrected the text.
    Comment: Airbus recommended that the non-cumulative (non-tracking) 
nature of changes that meet the change criteria, a core part of the 
change criteria developed by ICAO, should be mentioned in either part 
38 or AC38.
    Response: The FAA disagrees. The FAA recognizes that the ICAO 
standard and the EPA rule do not require cumulative tracking of 
airplane modifications to a type design. In kind, the FAA also does not 
have such a requirement. Since there is no requirement to track 
cumulative modifications, the FAA does not see a need to include any 
explanation of modification tracking in either part 38 or the AC38.
    Comment: Boeing asked to clarify Sec.  38.19(a)(2)(i) and (ii) by 
specifying the MTOM starting point associated with the percentage 
starting point in these two change criteria.
    Response: The FAA agrees these edits may help to clarify the 
requirement. The FAA has added the phrases ``for an airplane with a 
MTOM of 5,700 kg'' to clarify the 1.35 percent in Sec.  38.19(a)(2)(i) 
and ``for an airplane with an MTOM of 60,000 kg'' to clarify the 0.75 
percent in Sec.  39.19(a)(2)(ii).
    Comment: Gulfstream requested that the FAA provide clarification 
for documentation expectations in Sec.  38.19(c). Gulfstream noted that 
it is not clear how it is determined and what the FAA expectation will 
be to document that a modification does not increase the FEM by more 
than 1.5%.
    Response: For context, Sec.  38.19(c) requires an airplane that 
meets the criteria of Sec.  38.1(a)(4) and (5) on or after January 1, 
2023, and before January 1, 2028, to demonstrate compliance with Sec.  
38.17 if it incorporates any modification that increases the FEM value 
of the airplane by more than 1.5% prior to modification.
    Regarding the portion of Gulfstream's comment on documentation 
expectations, the FAA will determine whether part 38 applies to a 
covered airplane according to the criteria in Sec.  38.19(c) and the 
supporting documentation provided by the applicant. This determination 
is part of the type design change certification process in Sec.  
21.93(d) and FAA will decide documentation expectations on a

[[Page 12646]]

case-by-case basis depending on the complexity of the type design 
change.
    Comment: Gulfstream asked how a change in the FEM value is 
determined.
    Response: The requirements in part 38 and its appendix provide the 
detailed information required to determine a fuel efficiency metric 
value for a type design, such as corrections, tolerances, and 
confidence intervals. The AC38 provides additional detailed guidance 
and worked examples on how applicants can evaluate the FEM value for an 
airplane.
    Comment: An individual commented that the magnitude of change in 
the FEM value caused by the addition of a satellite antenna could be 
lower than in the example provided in that discussion.
    Response: The FAA acknowledges that FEM value changes due to 
modifications to airplanes could vary significantly. As provided in 
Sec.  38.19, the FEM values can increase or decrease when there are 
modifications to an airplane that impact aerodynamics.
    The NPRM discussion for Sec.  38.19 intended to focus on how the 
change criteria thresholds work, rather than the specific examples 
themselves. This comment does not require changes to the regulatory 
text.

P. FAA Approval Before Compliance Testing (Sec.  38.21)

    As proposed, Sec.  38.21 would require FAA approval of all 
procedures, weights, configurations, and other information needed to 
calculate the FEM value of an airplane. As described in the NPRM, the 
FAA would not apply this section to data an applicant submits for 
validation following fuel efficiency certification by another 
authority.
1. Discussion of the Final Rule
    As adopted, Sec.  38.21 requires FAA approval of all information 
needed to calculate the FEM value of an airplane. The FAA approvals are 
necessary and establish the airplane configuration and fuel efficiency 
certification procedures. These procedures remain unchanged before fuel 
efficiency compliance tests are conducted. This section does not apply 
to data submitted for validation following fuel efficiency 
certification by another authority. The FAA received several comments 
on proposed Sec.  38.21. The FAA adopts Sec.  38.21 as proposed.
2. Public Comments and FAA Response
    Comment: The GAMA requested that the FAA add the phrase 
``documented in compliance demonstration plans'' before ``approved by 
the FAA'' to Sec.  38.21.
    Response: The FAA finds the proposed change to be too prescriptive. 
Section 38.21 requires FAA approval of certain items prior to 
compliance testing, including procedures, weights, configurations, and 
other information. These items are used to establish the fuel 
efficiency level. Compliance demonstration plans may be one way of 
providing this information to the FAA. However, the FAA intends to 
preserve the ability for applicants to use other mechanisms to provide 
the required information to the FAA. The GAMA's proposed change would 
remove this flexibility.

Q. Manual Information and Limitations (Sec.  38.23)

    As proposed, Sec.  38.23 would require placement of the FEM value 
of the airplane, along with other part 38 compliance information, in an 
FAA-approved section of the flight manual of the airplane. Inclusion of 
this information in the approved airplane flight manual would provide 
owners, operators, and flight crew with information regarding the 
airplane's compliance with part 38. The FAA proposed that if a weight 
lower than the MTOM was used for fuel efficiency certification, then 
that lower weight becomes an operating limitation for that airplane and 
would be included in the operating limitations section of the flight 
manual. As provided in the NPRM, operators could not exceed the weight 
at which compliance with part 38 was demonstrated, even if that weight 
was lower than the MTOM for the airplane under other airworthiness 
requirements.
1. Discussion of the Final Rule
    The FAA made one change to this section in response to comments to 
specify that the manual include the fuel efficiency level as 
established in part 38. Other than the change to Sec.  38.23(a)(1), the 
FAA adopts the regulation as proposed.
2. Public Comments and FAA Response
    Comment: Boeing suggested clarifying the language in Sec.  
38.23(a)(1) to refer to compliance, as required by the part, rather 
than during certification. Boeing indicated that the proposed text 
could give rise to potential ambiguity with respect to an in-production 
airplane that complies with the fuel efficiency requirement in part 38, 
and compliance to part 38 need not be shown during type certification. 
Further, Boeing remarked that there is no reason that the compliance 
demonstration itself needs to be done during type certification and the 
FAA's regulatory language should be sufficiently flexible to 
accommodate such an approach.
    Response: The FAA concurs with the change proposed by Boeing and 
has replaced ``during type certification'' with ``as required by this 
part'' in Sec.  38.23(a). The use of ``as required by this part'' more 
specifically refers to the part 38 requirements rather than the type 
certification process.
    Comment: Airbus suggested removing the requirement to publish 
certified fuel efficiency data in the flight manual by deleting 
Sec. Sec.  38.23 and 21.5(b)(3). Airbus indicates that the adoption of 
these provisions would create de-harmonization between certification 
authorities. Airbus instead suggests relying on the ICAO CO2 
databank maintained by the FAA as well as through the EASA 
CO2 databank. Using the same justification, Airbus also 
requested that the FAA remove the proposed flight manual requirements 
from Sec. Sec.  121.141(b) and 125.75.
    Airbus was also concerned that if the certification applicant 
chooses to certify several MTOMs against the new part 38, several 
flight manual supplements would have to be created and maintained for 
the same airplane model.
    Response: The FAA disagrees with removing the flight manual 
publication requirement. Although most information may be available 
through the ICAO CO2 database \17\ or another certification 
authority-maintained database, these databases are either outside the 
FAA's control or potentially incomplete, because manufacturers are not 
required to submit information to the database. For these reasons, the 
databanks may not provide a complete set of information and may not 
contain information for a particular airplane. The inclusion of fuel 
efficiency levels and MTOM in the flight manual associated with a 
serial number specific airplane allows anyone, including an authority, 
to determine the compliance state of an airplane.
---------------------------------------------------------------------------

    \17\ The FAA hosts but does not control the contents of the ICAO 
Airplane CO2 Certification Database located at: 
www.faa.gov/headquartersoffices/apl/aee/icao-airplane-co2-certification-database.
---------------------------------------------------------------------------

    For these reasons, the FAA is retaining these requirements.
    Comment: Gulfstream asked if the industry could expect to see 
airports imposing fees or restrictions based on fuel efficiency, 
similar to noise, that would motivate an applicant to certify an 
airplane at a lower MTOM. Gulfstream recommended clarifying the 
potential for any benefit with artificially limiting the MTOM to a 
lower value than the design specification.

[[Page 12647]]

    Response: The FAA cannot speculate as to whether third parties, 
such as airports, would impose fees or restrictions on airplanes based 
on these fuel efficiency values.

R. Appendix A to Part 38

    As proposed, Appendix A provided the technical detail needed to 
determine the FEM value of an airplane required to demonstrate 
compliance with part 38. It also detailed the process and procedures an 
applicant needed to use when measuring an airplane for fuel efficiency. 
The proposal also described the data the applicant would submit to the 
FAA.
1. Discussion of the Final Rule
    As adopted, Appendix A to part 38 provides the technical, 
certification-specific details an applicant needs to determine the FEM 
value of an airplane and demonstrate compliance with part 38. The 
primary sources of the information contained in the appendix are 
Sections 2.5 and 2.6 of ICAO Annex 16, Volume III, as well as 
appendices 1 and 2 to that volume. These sources of information were 
not included in the EPA rule directly but were incorporated by 
reference. In coordination with the EPA, the FAA decided it was 
important to include such certification-related details in part 38 
given the FAA's responsibility to enforce the EPA rule within the FAA 
airplane certification framework. As a result, in this rule, the FAA 
does not incorporate this Annex information by reference but includes 
all the requirements from Annex 16 Volume III using current United 
States certification terminology, format, and references.
    Appendix A to part 38 details the processes and procedures to be 
used when measuring an airplane for fuel efficiency. To comply with 
part 38, a certification applicant would need to determine the core 
parameters of the FEM, specifically the SAR and RGF. The specifications 
for the flight tests to gather airplane performance data are provided 
in Appendix A, including the formulas to be used to determine the SAR 
and RGF from data gathered during testing. The appendix also describes 
certification data that would be submitted to the FAA in the 
certification test report that is a part of fuel efficiency 
certification.
    The FAA received comments on several sections of Appendix A to part 
38. As a result of these comments, as well as consistency edits that 
result from the FAA's responses to these comments, the FAA has made 
changes to proposed paragraphs A38.1.2.3.1, A38.1.2.3.4, A38.2.1.1.3, 
A38.2.1.1.6, A38.2.1.3.1, A38.2.1.3.2, A38.4.2.1.2, A38.4.2.1.3, 
A38.4.2.1.4.1, A38.4.2.1.4.2, A38.4.2.1.5.1, A38.4.2.1.5.2, A38.4.2.2, 
A38.4.2.2.1, A38.4.2.2.1.2, A38.4.2.2.1.4, A38.4.2.3.2.1, 
A38.4.2.3.2.2, A38.4.2.3.2.3, A.38.5.2.2.1.1, A38.6, A38.6.1.2, 
A38.6.3.7, A38.6.3.9, and A38.6.4. In general, the comments pertained 
to clarifications on airplane weighing and mass requirements, fuel 
sampling requirements, fuel kinematic viscosity requirements, airplane 
trim requirements, the use of standard United States aerospace 
terminology, engine deterioration, corrections to reference 
specifications, the reporting of data, the fixing titles of reference 
citations, and some minor typographical errors.
    Paragraph A38.2.1.3.1 identifies a reference specification for 
standard day atmosphere. As discussed in relation to Sec.  38.7, the 
FAA has determined that this specification needs to be incorporated by 
reference and has indicated that in A38.2.1.3.1 as well as the other 
paragraphs that include this same reference specification (i.e., 
paragraphs A38.5.2.2.1.9 and A38.5.2.2.1.10). Also, in paragraph 
A38.2.1.3.1, the FAA noticed that it inadvertently failed to include an 
``and'' at the end of this paragraph, which is now included for 
consistency with the ICAO standard. The FAA corrected the section 
accordingly. In paragraphs 38.3.2, 38.3.3, and 38.3.4, this rule adopts 
changes from ``cockpit'' to ``flight deck'' to provide gender-neutral 
language without changing the meaning or intent.
    Other than these changes, the FAA adopts the Appendix as proposed.
2. Public Comments and FAA Response
    The comments and responses below are categorized based on the 
relevant appendix section.
a. Appendix A to Part 38, A38.1 Introduction
    Comment: For proposed paragraphs A38.1.2.3.1 and A38.1.2.3.4, 
Airbus noted potential errors including a missing ``and'' between 
listed requirements of a performance model, and incorrect numbering of 
appendix sections where A38.1.2.3.4 should have been A38.1.2.3.3.
    Response: The FAA disagrees with the request to add an ``and'' at 
the end of A38.1.2.3.1. The FAA notes the proposal contained an ``and'' 
in the next to last item in the list and this is sufficient to make 
each of the items under A.38.1.2.3 a requirement. Thus, the FAA did not 
make this proposed change. However, with respect to the incorrect 
numbering in proposed A38.1.2.3.4, the FAA agrees that this is a 
typographical error and has corrected it.
b. Appendix A to Part 38, A38.2 Reference Specifications for SAR Flight 
Tests
    Comment: For paragraph A38.2.1.1.3, Boeing suggested using standard 
industry terminology of ``unaccelerated'' instead of 
``unaccelerating.''
    Response: The FAA agrees that ``unaccelerated'' is a more common 
aerospace industry terminology when describing steady-level flight, 
thus the FAA made the suggested changes. The FAA also made these same 
changes to paragraphs A38.4.2.2.1.2 and A38.5.2.2.1.
    Comment: For paragraph A38.2.1.1.5, Gulfstream requested 
confirmation that, when it uses a performance model, all the provided 
information in the section will be embedded in the model and additional 
corrections will not be required in the model results.
    Response: The FAA confirms that reference specifications are 
required for flight test data, which can be used to validate a 
performance model. Depending on how the performance model is built and 
on what data it is based, corrections may be necessary for SAR values 
calculated from the model.
c. Appendix A to Part 38, A38.4 Certification Test Specifications
    Comment: For paragraph A38.4.2.1.2, Boeing requested to clarify the 
airplane weight and balance requirement by removing the words ``prior 
to the test flight.'' Boeing indicated it may be possible that the 
weight before flight may not be the best engineering value; because 
test data may, after post-flight weighing, suggest a more optimal means 
for establishing accurate weight.
    Response: The FAA agrees that this airplane weight requirement can 
be clarified, however disagrees with the proposed changes as they would 
cause a substantive difference (discussed in IV.F.) with the ICAO 
international standard that includes the words ``prior to the test 
flight.'' The FAA has revised the text to align with the ICAO 
international standard by changing the requirement to read: ``The test 
airplane must be weighed. Any change in mass after the weighing and 
prior to the test flight must be accounted for.'' During its review of 
this paragraph, the FAA recognized that the ``and balance'' text that 
was contained in the proposed A38.4.2.1.2 is not required given the 
various center of gravity requirements throughout Appendix A. After 
reviewing all center of gravity requirements in Appendix A, the FAA

[[Page 12648]]

made a clarifying change in A38.2.1.1.6 by changing ``a'' to ``the'' in 
the proposed text (i.e., representative of a mid-CG point relevant to 
design cruise performance). The FAA's clarifying change ensures there 
is no ambiguity as there is only one mid-CG point at each of the three 
reference airplane masses.
    Comment: For paragraphs A38.4.2.1.3, A38.4.2.1.4.1, A38.4.2.1.5.1, 
and A38.4.2.1.5.2, Boeing suggested correcting these reference 
citations by: (1) removing the word ``specification'' when referring to 
the external American Society for Testing and Materials (ASTM) 
documents, and (2) correcting the titles of the documents as needed.
    Response: The FAA agrees to these minor editorial changes and 
accepts them. The FAA also noticed, and corrected, that the word 
``titled'' instead of ``entitled'' should have been used when quoting 
the titles of these documents.
    Comment: For paragraph A38.4.2.1.4.2, Airbus suggested that it did 
not understand the text ``and may not have variations'' at the end of 
the fuel sample requirement, because fuel samples are analyzed for each 
test flight and a single lower heating value is determined.
    Response: The FAA agrees with this reasoning and has revised the 
text to better align with the ICAO international standard regarding 
flexibility on variations and errors. The language now reads:
    The fuel sample may be representative of the fuel used for each 
flight test and should not have errors or variations due to fuel being 
uplifted from multiple sources, fuel tank selection, or fuel layering 
in a tank.
    Comment: For paragraph A38.4.2.1.5.2, Airbus requested an 
additional ASTM document be added for determining fuel kinematic 
viscosity.
    Response: The FAA disagrees because it would result in a 
substantive difference (discussed in IV.F.) with the ICAO international 
standard. In addition, the FAA notes that the words ``or as approved by 
the FAA'' at the end of that paragraph allow applicants to seek 
approval of other methods for determining fuel kinematic viscosity, 
which is consistent with the ICAO standard.
    Comment: An individual commented on paragraph A38.4.2.2 regarding 
the use of the term ``configuration.'' They indicated that this section 
relates to criteria, procedures, or requirements and that it does not 
relate to configurations, which is a term used for defining an airplane 
configuration such as a flap position, gear position, or some aspect of 
the type design.
    Response: Upon review, the FAA acknowledges the word 
``configuration(s)'' does not accurately reflect the requirement. The 
requirement relates more to procedures on how the pilot should fly the 
airplane during flight testing. As such, the FAA has replaced the word 
``configuration(s)'' with the word ``procedure(s)'' in A38.4.2.2 and 
A38.4.2.2.1.
    Comment: For paragraph A38.4.2.2.1.4, Boeing requested a change to 
the text ``there are no changes in trim.'' Boeing requested that the 
text be revised to allow some changes by stating that changes are to be 
avoided or minimized as practicable. Boeing explained that it may not 
be possible to eliminate all changes during flight because there may be 
unavoidable circumstances during flight; however, such changes may be 
accounted for through data analysis and interpretation.
    Response: The FAA agrees that in-flight conditions may not make it 
possible to eliminate changes to some trim and engine settings, and 
that changes may be accounted for through post-flight data analysis. 
The FAA also notes that providing flexibility better aligns with the 
same recommendation in the ICAO international standard. Accordingly, 
the FAA revised the text to read as follows:
    Changes in trim or engine power/thrust settings, engine stability 
and handling bleeds, or electrical and mechanical power extraction 
(including bleed flow) are avoided or minimized as practicable.
    Comment: For paragraph A38.4.2.3.2, Airbus explained that the 
requirement regarding airplane mass determination should provide for 
alternative methods, specifically by changing the word ``must'' to 
``may.''
    Response: The FAA agrees that this requirement should allow 
additional methods to determine the mass of the airplane because the 
ICAO Annex 16 Vol III also lists the two methods as recommended options 
for determining mass, not as required methods. Therefore, the FAA kept 
the word ``must,'' but added a third option to A38.4.2.3.2.3: other 
methods as approved by the FAA. This third option will allow 
alternative methods in addition to the two options listed.
d. Appendix A to Part 38, A38.5 Measurement of Specific Air Range
    Comment: For paragraph A38.5.2.2.1.7, Airbus suggested the sentence 
starting with the text ``(s)ince engine deterioration is rapid when . . 
.'' may not be grammatically correct.
    Response: The FAA notes that this is a partial sentence that is a 
lead-in to the two sub-paragraphs that follow it. In that context, the 
FAA does not see a need to make changes to this text.
    Comment: For paragraph A38.5.2.2.1.7.2, Boeing suggested replacing 
the proposed text, ``. . . and no correction is permitted'' with, ``. . 
. and a correction to the reference deterioration level may be approved 
by the FAA.'' Boeing asserted that technology and processes have 
advanced to the point where it is reasonable to employ engine 
deterioration corrections in certain circumstances. Boeing noted that 
it has successfully employed deterioration corrections on occasion and 
believes that the FAA provide flexibility for deterioration corrections 
if the FAA approves of the correction.
    Response: The FAA disagrees with providing the suggested 
flexibility for this requirement because this change would cause a 
substantive difference (discussed in IV.F.) with the ICAO international 
standard that precludes correction in these instances.
    Comment: For paragraph A38.5.3, Gulfstream commented that it is 
unclear how an applicant will manage confidence intervals when a 
performance model is used.
    Response: The AC38 provides guidance on determining and using 
confidence intervals.
e. Appendix A to Part 38, A38.6 Submission of Certification Data to the 
FAA
    Comment: For paragraph A38.6, Airbus recommended edits to the 
proposed text to allow other analysis reports to convey the required 
information, not just the certification test report.
    Report: The FAA agrees that there are various types of reports 
during certification that could contain the required information. The 
FAA made the change from ``certification test report'' to 
``certification reports.''
    Comment: For paragraphs A38.6.1.2, A38.6.3.7, and A38.6.3.9, Airbus 
and Boeing noted typographical and reference errors, including a 
reference to Sec.  38.23(a)(3) that does not exist in A38.6.1.2, a 
correction to a semicolon in A38.6.3.7, and incorrect references within 
A38.6.3.9.
    Response: The FAA agrees and fixed the noted typographical and 
reference errors.
    Comment: For paragraph A38.6.4, Airbus requested that the FAA 
remove the text ``defined in Sec.  38.13(b).'' Airbus indicated that 
this language suggested that the test measurements are

[[Page 12649]]

systematically done at the reference masses of the standard but that 
this was not the case when a performance model was used.
    Response: The FAA agrees that the reference to Sec.  38.13(b) 
should be removed for the reasons Airbus stated and has removed the 
reference. In addition, the FAA's review resulted in the need to 
clarify this requirement in paragraph A38.6.4 by clearly stating that 
SAR values, corrections from measured data to reference specifications, 
and finally the SAR values calculated from corrected data must be 
provided for the test measurement points. As such, the requirement has 
been updated to the following language:
    The measured SAR test data, all corrections of the measured data to 
the reference specifications, and the SAR values calculated from the 
corrected data must be provided.

S. Other Revisions to 14 CFR

    The proposed rule set forth several amendments to part 21 to 
include compliance with part 38 as a requirement for type, supplemental 
type, or airworthiness certification using the applicability described 
in Sec.  38.1. If adopted, the amendment proposed to part 21 would 
include adding references to part 38 in Sec. Sec.  21.5, 21.17, 21.29, 
21.31, 21.93, 21.101, 21.115, 21.183, and 21.187. The NPRM also 
proposed to adopt the move and redesignation of Sec.  21.187(c) to 
Sec.  21.187(a)(3). The proposal also included amendments to the 
operating regulations (Sec. Sec.  121.141 and 125.75) for airplanes 
subject to part 38. The revisions were included to add the 
certification information for fuel efficiency to the airplane flight 
manuals.
1. Discussion of the Final Rule
    With some changes, this rule adopts the proposed changes to part 21 
and Sec. Sec.  121.141 and 125.75.
    In particular, in this final rule, the FAA also makes a change to 
Sec.  21.93(d) by adding that a voluntary change that may increase the 
MTOM of that airplane is a ``fuel efficiency change.'' The proposal 
only identified an increase in the FEM value as a ``fuel efficiency 
change.'' This change was made to ensure consistency with the change 
criteria in Sec.  38.19.
    Further, as a result of comments, the FAA made changes to 
Sec. Sec.  21.21, 21.93, and 121.141. These changes ensure that the 
fuel efficiency requirements are appropriately included in part 21 and 
corrected an inadvertent change in Sec.  121.141. Other than these 
identified changes, the FAA adopts the amendments to part 21 and 
Sec. Sec.  121.141 and 125.75 as proposed.
    Finally, this rule adopts changes to Sec.  21.187 to provide 
gender-neutral language (from ``He'' to ``The applicant'') without 
changing the meaning or intent of the rule.
    The comments and responses are organized by the specific regulatory 
section.
2. Public Comments and FAA Response
a. Section 21.5: Airplane or Rotorcraft Flight Manual
    Comment: One individual commenter recommended adding ``Rotorcraft 
Flight Manual'' to the change proposed in Sec.  21.5(b)(3).
    Response: The FAA does not concur with adding ``Rotorcraft Flight 
Manual'' to the changes in Sec.  21.5(b)(3) to accommodate the addition 
of part 38 requirements as this rule only applies to fixed wing 
airplanes.
    Comment: One commenter stated Sec.  21.5 only pertains to airplanes 
and rotorcraft not type certificated with an Airplane or Rotorcraft 
Flight Manual and asked whether there were any such airplanes in 
existence that would be subject to part 38.
    Response: Section 21.5 applies to all airplanes that do not have 
flight time prior to March 1, 1979. Airplanes produced or certified on 
or after that date are required to have an approved flight manual.
    Comment: One individual proposed the airplane flight manual 
requirement should be placed in Sec. Sec.  25.1581 and 23.2620. They 
stated that it was also unclear how the requirement in Sec.  21.5 
meshes with Sec.  38.23. They thought the requirements of Sec.  38.23 
should either be placed in or reference the sections of parts 23 and 25 
pertaining to Airplane Flight Manuals and airplane limitations.
    Response: The FAA disagrees with the requested amendments to parts 
23 and 25. Flight manual requirements are covered in the revised Sec.  
21.5. This final rule also amends the applicability requirements in 
other sections of part 21 such that Sec.  21.5 applies to part 23 and 
25 airplanes. Accordingly, the flight manuals for these airplanes must 
include the flight manual requirements of part 38.
b. Section 21.21: Issue of Type Certificate: Normal, Utility, 
Acrobatic, Commuter, and Transport Category Aircraft; Manned Free 
Balloons; Special Classes of Aircraft; Aircraft Engines; Propellers
    Comment: Boeing recommended that the FAA revise Sec.  21.21(b) and 
(b)(1) by adding ``and fuel efficiency'' to be consistent with proposed 
Sec.  38.1(a)(1), (2) and (3) (for new-type airplanes seeking original 
type certification). Boeing noted that adding ``fuel venting and 
exhaust emissions'' to Sec.  21.21 would also be consistent with the 
FAA's revision of Sec.  21.29.
    Response: Section 21.21 identifies all the necessary requirements 
for receiving a type certificate. In order to fully effectuate part 38 
into the type certification requirements, it is important to include 
this rule in paragraph (b) of this section. Further, the FAA agrees 
that consistency is necessary between Sec. Sec.  21.21 and 21.29. 
Section 21.21 was revised to list fuel efficiency in addition to the 
other environmental requirements that an applicant must comply with in 
order to get a type certificate. The FAA has modified Sec.  21.21 to 
include fuel efficiency.
    The FAA inadvertently revised Sec.  21.29 with a punctuation error 
in the proposed rule to state, ``fuel venting and exhaust emissions, 
and fuel efficiency.'' The FAA has corrected this in the final rule to 
state ``fuel venting, exhaust emission, and fuel efficiency'' to be 
consistent with Sec.  21.21.
c. Section 21.93: Classification of Changes in Type Design
    Comments: Gulfstream requested clarity on the use of the word 
``voluntary'' regarding type design changes in Sec.  21.93(d). 
Gulfstream recollected that the ICAO language did not include the word 
``voluntary'' and asked if it was the FAA's intent to protect 
applicants from having to reverify part 38 compliance after a mandated 
design change.
    Response: The FAA's intent was to prevent applicants from having to 
reverify part 38 compliance after a mandated design change. The FAA 
uses the word ``voluntary'' to describe the action initiated by an 
applicant to obtain an approval. On the other hand, non-voluntary or 
mandated changes, typically required by an authority, are needed to 
maintain the airworthiness of in-service airplanes as soon as possible 
for safety concerns. The ICAO Standards and Recommended Practices do 
not have a similar exception for authority-mandated changes to an 
airplane. It is the responsibility of the authority adopting the 
Annexes to provide their own procedures for handling mandated changes 
required for continued operational safety.
    Comments: Embraer noted that 14 CFR 21.93(d) defines the term `fuel 
efficiency change' that is not used within 14 CFR part 38. This leaves 
the applicability definition of 14 CFR part 38 within Sec.  38.19. On 
the other hand,

[[Page 12650]]

Embraer stated that ICAO/RBAC \18\ uses the definition of ``derived 
version'' to determine applicability. Although the definitions are 
similar, Embraer states this could generate interpretation problems 
when classifying a modification and, consequently, to define the 
involvement of the authorities.
---------------------------------------------------------------------------

    \18\ This is an acronym in Portuguese for Brazilian Regulations 
for Civil Aviation.
---------------------------------------------------------------------------

    Response: The FAA is not defining a new term ``fuel efficiency 
change'' as Embraer indicates. This language refers to changes in the 
certified ``fuel efficiency metric value'' as provided in part 38. The 
applicability of Sec.  38.1 includes a direct reference to Sec.  38.19 
(see in Sec.  38.1(b)) and, therefore, includes modifications as part 
of applicability considerations. Similarly, ICAO includes modifications 
via a definition of ``derived versions'' that is contained outside the 
applicability provisions.
d. Other Part 21 Sections
    Comments: Boeing suggested adding additional text to Sec. Sec.  
21.101(a), 21.115(a)(3), 21.183(j), and 21.187(a)(4) that direct a 
reader to specific applicability sections of part 38. Boeing was 
concerned that, as drafted, these sections could mistakenly be read to 
mean that an obligation to demonstrate compliance with part 38 applies 
automatically upon any application for approval of a modification in 
type design for any airplane, including an in-service airplane, 
regardless of whether the requirements of Sec. Sec.  38.1 and 38.19 are 
met.
    Response: The FAA disagrees. Section 21.93(d) refers to part 38 for 
purposes of maintaining compliance with part 38. Part 38 is the 
appropriate regulatory location to determine which sections of part 38 
apply in a particular circumstance.
    Further, the FAA has revised the applicability requirements in part 
38 to clarify its applicability to modifications in type design for any 
airplane, including an in-service airplane. See FAA's responses to 
comments in section IV.D. For these reasons, the FAA is not adopting 
the suggested changes.
e. Section 121.141 (Airplane Flight Manual) and 125.75 (Airplane Flight 
Manual)
    Comment: One individual commenter noted that changing the word 
``may'' to ``must'' is a significant change in Sec.  121.141(b), making 
it mandatory to revise the performance section of the Airplane Flight 
Manual when operators create their own manual. The commenter also noted 
that this change was not consistent with the proposal to change Sec.  
125.75(b), which does not change a similar ``must'' in the existing 
text to ``may.'' The commenter also recommended that if FAA meant to 
change the language to ``must'' in Sec.  121.141(b), the FAA should 
make a corresponding change in Sec.  125.75(b) and explain the change 
in the preamble.
    Response: The FAA concurs that the text added to Sec.  121.141(b) 
should have said ``may revise'' not ``must revise.'' This was an 
inadvertent change from existing text. Accordingly, the final rule text 
is corrected to ``may revise'' and the FAA does not need to make the 
suggested change to Sec.  125.75(b).
T. Costs
    A number of individuals commented generally regarding their 
concerns about the monetary costs of the rule.
    The FAA conducted an analysis of the costs and benefits of the 
proposed rule. As described in the preliminary regulatory impact 
analysis (RIA) that accompanied the proposal, in the absence of the 
FAA's rule aircraft manufacturers would have to certify to the fuel 
efficiency standards through foreign authorities. As a result, the rule 
reduces the cost of this certification by enabling certification 
through the FAA. Therefore, the FAA does not expect this rule will 
impose an undue burden on industry, an increase in the cost of air 
travel, or other negative economic impacts commenters attribute to the 
rule. Regarding the need for government intervention, airplane fuel 
efficiency has increased as the standard is technology-following, but 
the rule prevents backsliding to less fuel-efficient airplanes. The FAA 
also noted that the rule may generate minimal benefits since the ICAO 
designed the standard in such a way that most airplanes would already 
meet the standard.
    Boeing asserted that footnote 8 in the preliminary RIA contradicted 
the EPA's unambiguous intent with respect to the inapplicability of its 
GHG standards to modifications of individual in-service airplanes. The 
footnote stated that owners or operators that modify an airplane that 
was not certificated to the proposed fuel efficiency standard may also 
need to comply with the rule when the modifications are made. The 
National Business Aviation Association (NBAA) also asserted that in the 
preliminary RIA, the FAA failed to analyze the financial impact this 
rule may have on the current fleet. Specifically, it stated that 
operators seeking to modify their airplanes through a Supplemental Type 
Certificate (STC) may have to complete additional modifications or data 
analysis to meet the FEM, resulting in additional costs. The NBAA 
encouraged the FAA to consider this submission prior to applying this 
rule to modified airplanes.
    The FAA asserts that there will be no economic impact on the 
current fleet stemming from this rule. The FAA agrees that owners or 
operators that modify an airplane that was not certificated to the fuel 
efficiency standards will not need to comply with the rule when those 
modifications are made. The rule does not apply to the in-service fleet 
that was not certified to the fuel efficiency standard, including any 
future modifications. As such, there will be no impact on the current 
fleet for operators seeking to modify their airplane through an STC. 
The FAA deleted the referenced footnote 8 in the final RIA.

V. Regulatory Notices and Analyses

    Federal agencies consider impacts of regulatory actions under a 
variety of executive orders and other requirements. First, Executive 
Order 12866 and Executive Order 13563 direct that each Federal agency 
shall propose or adopt a regulation only upon a reasoned determination 
that the benefits of the intended regulation justify the costs. Second, 
the Regulatory Flexibility Act of 1980 (Pub. L. 96-354) requires 
agencies to analyze the economic impact of regulatory changes on small 
entities. Third, the Trade Agreements Act (Pub. L. 96-39) prohibits 
agencies from setting standards that create unnecessary obstacles to 
the foreign commerce of the United States. Fourth, the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies to 
prepare a written assessment of the costs, benefits, and other effects 
of proposed or final rules that include a Federal mandate that may 
result in the expenditure by State, local, and Tribal governments, in 
the aggregate, or by the private sector, of $100 million or more 
(adjusted annually for inflation) in any one year. The current 
threshold after adjustment for inflation is $177 million using the most 
current (2022) Implicit Price Deflator for the Gross Domestic Product. 
The FAA has provided a detailed Regulatory Impact Analysis (RIA) in the 
docket for this rulemaking. This portion of the preamble summarizes the 
FAA's analysis of the economic impacts of this rule.
    In conducting these analyses, the FAA has determined that this 
rule: will result in benefits that justify costs; is not a 
``significant regulatory action'' as defined in section 3(f) of 
Executive Order 12866, as amended by Executive Order 14094; will not 
have a significant

[[Page 12651]]

economic impact on a substantial number of small entities; will not 
create unnecessary obstacles to the foreign commerce of the United 
States; and will not impose an unfunded mandate on State, local, or 
Tribal governments, or on the private sector.

A. Summary of the Regulatory Impact Analysis

    The FAA identified three United States manufacturers that would be 
affected by the rule. Manufacturers will incur certification costs even 
in the absence of the rule since they would pursue certification with 
foreign authorities. Certification tasks will vary greatly depending on 
the stage of the airplane development process (e.g., new type 
certificate, supplemental type certificate, etc.). Additionally, the 
first fuel efficiency certification project undertaken by any one 
manufacturer may require more resources because of the new processes 
and the need for new data generation. The FAA used information provided 
by the affected airplane manufacturers to construct a timeline of when 
these costs would be incurred over a 10-year period, and the cost 
savings from domestic certification enabled by the rule.
    Because the EPA standards apply to airplanes certificated in the 
United States even in the absence of the rule, there are no incremental 
benefits associated with the FAA's action; however, the rule will 
result in cost savings by enabling United States manufacturers to 
certificate to the standards domestically. Annualized costs savings may 
be approximately $0.4 million using discount rates of 3 percent and 7 
percent (a present value over 10 years of $3.5 million to $2.9 million, 
using discount rates of 3 percent and 7 percent, respectively).
    Please see the RIA available in the docket for more details.

B. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) of 1980, (5 U.S.C. 601-612), 
as amended by the Small Business Regulatory Enforcement Fairness Act of 
1996 (Pub. L. 104-121) and the Small Business Jobs Act of 2010 (Pub. L. 
111-240), requires Federal agencies to consider the effects of the 
regulatory action on small business and other small entities and to 
minimize any significant economic impact. The term ``small entities'' 
comprises small businesses and not-for-profit organizations that are 
independently owned and operated and are not dominant in their fields, 
and governmental jurisdictions with populations of less than 50,000.
    As described in the RIA, the FAA identified three United States 
manufacturers that would be affected by the proposed rule. Based on the 
Small Business Administration (SBA) size standard for aircraft 
manufacturing (Table 1), all three manufacturers are large businesses. 
If an agency determines that a rulemaking will not result in a 
significant economic impact on a substantial number of small entities, 
the head of the agency may so certify under section 605(b) of the RFA. 
Therefore, as provided in section 605(b) and based on the foregoing, 
the head of FAA certifies that this rulemaking will not result in a 
significant economic impact on a substantial number of small entities.

       Table 1--Small Business Size Standards: Air Transportation
------------------------------------------------------------------------
     NAICS code              Description              Size standard
------------------------------------------------------------------------
336411..............  Aircraft manufacturing..  1,500 employees.
------------------------------------------------------------------------
Source: SBA (2022).\19\
NAICS = North American Industrial Classification System.

C. International Trade Impact Assessment
---------------------------------------------------------------------------

    \19\ Small Business Administration (SBA). 2022. Table of Size 
Standards. Effective July 14, 2022. www.sba.gov/document/support--table-size-standards.
---------------------------------------------------------------------------

    The Trade Agreements Act of 1979 (Pub. L. 96-39), as amended by the 
Uruguay Round Agreements Act (Pub. L. 103-465), prohibits Federal 
agencies from establishing standards or engaging in related activities 
that create unnecessary obstacles to the foreign commerce of the United 
States. Pursuant to these Acts, the establishment of standards is not 
considered an unnecessary obstacle to the foreign commerce of the 
United States, so long as the standard has a legitimate domestic 
objective, such as the protection of safety and does not operate in a 
manner that excludes imports that meet this objective. The statute also 
requires consideration of international standards and, where 
appropriate, that they be the basis for United States standards.
    The FAA has assessed the potential effects of this rule and finds 
that it does not create an unnecessary obstacle to foreign commerce. 
The United States has adopted the same airplane emission standards as 
ICAO and many of its member States. This rule is the next step in 
insuring compliance with the internationally recognized standard.

D. Unfunded Mandates Assessment

    The Unfunded Mandates Reform Act of 1995 (2 U.S.C. 1531-1538) 
governs the issuance of Federal regulations that require unfunded 
mandates. An unfunded mandate is a regulation that requires a State, 
local, or Tribal government or the private sector to incur direct costs 
without the Federal government having first provided the funds to pay 
those costs. The FAA determined that this final rule will not result in 
the expenditure of $177 million or more by State, local, or Tribal 
governments, in the aggregate, or the private sector, in any one year.
    This rule does not contain such a mandate; therefore, the 
requirements of title II of the Act do not apply.

E. Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires 
that the FAA consider the impact of paperwork and other information 
collection burdens imposed on the public. According to the 1995 
amendments to the Paperwork Reduction Act (5 CFR 1320.8(b)(2)(vi)), an 
agency may not collect or sponsor the collection of information, nor 
may it impose an information collection requirement unless it displays 
a currently valid Office of Management and Budget (OMB) control number.
    This action contains the following new information collection 
requirement. As required by the Paperwork Reduction Act of 1995 (44 
U.S.C. 3507(d)), the FAA has submitted these information collection 
amendments to OMB for its review. The OMB control number for this 
action is 2120-0815.
Summary
    The regulations, adding a new part 38 to 14 CFR that requires 
certification for fuel efficiency, includes a collection of data from 
certification applicants. Certain data collected by the respondent 
during its certification flight tests are to be included in a 
certification test report that is submitted to the FAA. Those data are 
described in Appendix A to part 38. The information in the test report 
is used by the agency to determine whether the subject airplane 
complies with the fuel efficiency requirements promulgated by the EPA 
and the FAA. Without such information, the FAA would not have the 
complete record of an airplane's fuel efficiency performance and would 
be unable to issue a type or airworthiness certificate.
Use
    Respondent's data will be used to determine compliance with the 
fuel efficiency standards established by the

[[Page 12652]]

EPA under the requirements of the Clean Air Act. The FAA is required by 
the Clean Air Act to implement those standards, which is done at the 
time of airplane certification.
    Respondent's test data will not be maintained by the FAA following 
a certification determination. The certification test report is not 
available to the public. The regulation also requires that certain 
values be listed in the flight manual of the airplane, which is given 
to the purchaser of an airplane.
    Respondents (including number of): The FAA anticipates three 
respondents to the collection of information.
    Frequency: The FAA anticipates that respondents will provide 
responses annually (averaged).
    Annual Burden Estimate: Table 1 provides the FAA's estimates of 
annual reporting (submittal of certification data) and recordkeeping 
(manual information) burden.

                    Table 1--Summary of Annual Burden
------------------------------------------------------------------------
                  Category                    Reporting   Recordkeeping
------------------------------------------------------------------------
# of respondents...........................           3                3
# of responses per respondent..............           2                2
Time per response (hours)..................           2                8
                                            ----------------------------
  Total # of responses.....................           6                6
                                            ----------------------------
    Total burden (hours)...................          12               48
------------------------------------------------------------------------

F. International Compatibility

    In keeping with United States' obligations under the Convention on 
International Civil Aviation, it is FAA policy to conform to 
International Civil Aviation Organization (ICAO) Standards and 
Recommended Practices to the maximum extent practicable. The FAA has 
reviewed the corresponding ICAO Standards and Recommended Practices and 
has identified no substantive differences with these regulations.

G. Environmental Analysis

    FAA Order 1050.1F identifies FAA actions that are categorically 
excluded from preparation of an environmental assessment or 
environmental impact statement under the National Environmental Policy 
Act (NEPA) in the absence of extraordinary circumstances. The FAA has 
determined this rulemaking action qualifies for the categorical 
exclusion identified in paragraph 5-6.6f for regulations and involves 
no extraordinary circumstances.

VI. Executive Order Determinations

A. Executive Order 13132, Federalism

    The FAA has analyzed this final rule under the principles and 
criteria of Executive Order (E.O.) 13132, Federalism. The FAA has 
determined that this action will not have a substantial direct effect 
on the States, or the relationship between the Federal Government and 
the States, or on the distribution of power and responsibilities among 
the various levels of government, and, therefore, will not have 
federalism implications.

B. Executive Order 13175, Consultation and Coordination With Indian 
Tribal Governments

    Consistent with Executive Order 13175, Consultation and 
Coordination with Indian Tribal Governments,\20\ and FAA Order 1210.20, 
American Indian and Alaska Native Tribal Consultation Policy and 
Procedures,\21\ the FAA ensures that Federally Recognized Tribes 
(Tribes) are given the opportunity to provide meaningful and timely 
input regarding proposed Federal actions that have the potential to 
have substantial direct effects on one or more Indian Tribes, on the 
relationship between the Federal government and Indian Tribes, or on 
the distribution of power and responsibilities between the Federal 
government and Indian Tribes; or to affect uniquely or significantly 
their respective Tribes. At this point, the FAA has not identified any 
unique or significant effects, environmental or otherwise, on Tribes 
resulting from this final rule.
---------------------------------------------------------------------------

    \20\ 65 FR 67249 (Nov. 6, 2000).
    \21\ FAA Order No. 1210.20 (Jan. 28, 2004), available at 
www.faa.gov/documentLibrary/media/1210.pdf.
---------------------------------------------------------------------------

C. Executive Order 13211, Regulations That Significantly Affect Energy 
Supply, Distribution, or Use

    The FAA analyzed this final rule under E.O. 13211, Actions 
Concerning Regulations that Significantly Affect Energy Supply, 
Distribution, or Use (May 18, 2001). The FAA has determined that it is 
not a ``significant energy action'' under the executive order and not 
likely to have a significant adverse effect on the supply, 
distribution, or use of energy.

D. Executive Order 13609, Promoting International Regulatory 
Cooperation

    Executive Order 13609, Promoting International Regulatory 
Cooperation, promotes international regulatory cooperation to meet 
shared challenges involving health, safety, labor, security, 
environmental, and other issues and reduce, eliminate, or prevent 
unnecessary differences in regulatory requirements. The FAA has 
analyzed this action under the policy and agency responsibilities of 
Executive Order 13609. The FAA has determined that this action will 
eliminate differences between United States aviation standards and 
those of other civil aviation authorities by adopting the airplane 
certification regulations needed to comply with the standards adopted 
by ICAO and the EPA.

VII. Additional Information

A. Electronic Access and Filing

    A copy of the NPRM, all comments received, this final rule, and all 
background material may be viewed online at www.regulations.gov using 
the docket number listed above. A copy of this final rule will be 
placed in the docket. Electronic retrieval help and guidelines are 
available on the website. It is available 24 hours each day, 365 days 
each year. An electronic copy of this document may also be downloaded 
from the Office of the Federal Register's website at 
www.federalregister.gov and the Government Publishing Office's website 
at www.govinfo.gov. A copy may also be found at the FAA's Regulations 
and Policies website at www.faa.gov/regulations_policies.
    Copies may also be obtained by sending a request to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW, Washington, DC 20591, or by calling (202) 267-9677. 
Commenters must identify the docket or notice number of this 
rulemaking.
    All documents the FAA considered in developing this final rule, 
including economic analyses and technical reports, may be accessed in 
the electronic docket for this rulemaking.

B. Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996 requires the FAA to comply with small entity requests for 
information or advice about compliance with statutes and regulations 
within its jurisdiction. A small entity with questions regarding this 
document may contact its local FAA official, or the person listed under 
the FOR FURTHER INFORMATION CONTACT

[[Page 12653]]

heading at the beginning of the preamble. To find out more about SBREFA 
on the internet, visit www.faa.gov/regulations_policies/rulemaking/sbre_act/.

List of Subjects

14 CFR Part 21

    Aircraft, Aviation safety, Exports, Imports, Reporting and 
recordkeeping requirements.

14 CFR Part 38

    Air Pollution Control, Aircraft, Incorporation by reference.

14 CFR Part 121

    Air carriers, Aircraft, Airmen, Alcohol abuse, Aviation safety, 
Charter flights, Drug abuse, Drug testing, Reporting and recordkeeping 
requirements, Safety, Transportation.

14 CFR Part 125

    Aircraft, Airmen, Aviation safety, Reporting and recordkeeping 
requirements.

The Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration amends chapter I of title 14, Code of Federal 
Regulations as follows:

PART 21--CERTIFICATION PROCEDURES FOR PRODUCTS AND ARTICLES

0
1. The authority citation for part 21 continues to read as follows:

    Authority:  42 U.S.C. 7572; 49 U.S.C. 106(f), 106(g), 40105, 
40113, 44701-44702, 44704, 44707, 44709, 44711, 44713, 44715, 45303.


0
2. Amend Sec.  21.5 by adding paragraph (b)(3) to read as follows:


Sec.  21.5  Airplane or Rotorcraft Flight Manual.

* * * * *
    (b) * * *
    (3) Documentation of compliance with part 38 of this chapter, in an 
FAA-approved section of any approved airplane flight manual. Such 
material must include the fuel efficiency metric value as calculated 
under Sec.  38.11 of this chapter, and the specific paragraph of Sec.  
38.17 of this chapter with which compliance has been shown for that 
airplane.

0
3. Amend Sec.  21.17 by revising paragraph (a) introductory text to 
read as follows:


Sec.  21.17   Designation of applicable regulations.

    (a) Except as provided in Sec. Sec.  25.2, 27.2, and 29.2 of this 
subchapter, and in parts 26, 34, 36, and 38 of this subchapter, an 
applicant for a type certificate must show that the aircraft, aircraft 
engine, or propeller concerned meets--
* * * * *

0
4. Amend Sec.  21.21 by revising paragraphs (b) introductory text and 
(b)(1) to read as follows:


Sec.  21.21   Issue of type certificate: normal, utility, acrobatic, 
commuter, and transport category aircraft; manned free balloons; 
special classes of aircraft; aircraft engines; propellers.

* * * * *
    (b) The applicant submits the type design, test reports, and 
computations necessary to show that the product to be certificated 
meets the applicable airworthiness, aircraft noise, fuel venting, 
exhaust emission, and fuel efficiency requirements of this subchapter 
and any special conditions prescribed by the FAA, and the FAA finds--
    (1) Upon examination of the type design, and after completing all 
tests and inspections, that the type design and the product meet the 
applicable noise, fuel venting, emissions, and fuel efficiency 
requirements of this subchapter, and further finds that they meet the 
applicable airworthiness requirements of this subchapter or that any 
airworthiness provisions not complied with are compensated for by 
factors that provide an equivalent level of safety; and
* * * * *

0
5. Amend Sec.  21.29 by revising paragraphs (a)(1)(i) and (b) to read 
as follows:


Sec.  21.29   Issue of type certificate: import products.

    (a) * * *
    (1) * * *
    (i) The applicable aircraft noise, fuel venting, exhaust emissions, 
and fuel efficiency requirements of this subchapter as designated in 
Sec.  21.17, or the applicable aircraft noise, fuel venting, exhaust 
emissions, and fuel efficiency requirements of the State of Design, and 
any other requirements the FAA may prescribe to provide noise, fuel 
venting, exhaust emission, and fuel efficiency levels no greater than 
those provided by the applicable aircraft noise, fuel venting, exhaust 
emissions, and fuel efficiency requirements of this subchapter as 
designated in Sec.  21.17; and
* * * * *
    (b) A product type certificated under this section is determined to 
be compliant with the fuel venting and exhaust emission standards of 
part 34 of this subchapter, the noise standards of part 36 of this 
subchapter, and the fuel efficiency requirements of part 38 of this 
subchapter. Compliance with parts 34, 36, and 38 of this subchapter is 
certified under paragraph (a)(1)(i) of this section, and the applicable 
airworthiness standards of this subchapter, or an equivalent level of 
safety, with which compliance is certified under paragraph (a)(1)(ii) 
of this section.

0
6. Amend Sec.  21.31 by revising paragraph (e) to read as follows:


Sec.  21.31   Type design.

* * * * *
    (e) Any other data necessary to allow, by comparison, the 
determination of the airworthiness, noise characteristics, fuel 
efficiency, fuel venting, and exhaust emissions (where applicable) of 
later products of the same type.

0
7. Amend Sec.  21.93 by adding paragraph (d) to read as follows:


Sec.  21.93  Classification of changes in type design.

* * * * *
    (d) For the purpose of maintaining compliance with part 38 of this 
chapter, any voluntary change in the type design of an airplane that 
may increase the fuel efficiency metric value or the MTOM of that 
airplane is a ``fuel efficiency change'', in addition to being a minor 
or major change as classified in paragraph (a) of this section.

0
8. Amend Sec.  21.101 by revising paragraph (a) to read as follows:


Sec.  21.101  Designation of applicable regulations.

    (a) An applicant for a change to a type certificate must show that 
the change and areas affected by the change comply with the 
airworthiness requirements applicable to the category of the product in 
effect on the date of the application for the change and with parts 34, 
36, and 38 of this chapter. Exceptions are detailed in paragraphs (b) 
and (c) of this section.
* * * * *

0
9. Amend Sec.  21.115 by revising paragraph (a) to read as follows:


Sec.  21.115  Applicable requirements.

    (a) Each applicant for a supplemental type certificate must show 
that the altered product meets applicable requirements specified in 
Sec.  21.101 and--
    (1) In the case of an acoustical change described in Sec.  
21.93(b), show compliance with the applicable noise requirements of 
part 36 of this chapter;
    (2) In the case of an emissions change described in Sec.  21.93(c), 
show compliance with the applicable fuel venting and exhaust emissions

[[Page 12654]]

requirements of part 34 of this chapter; and
    (3) In the case of a fuel efficiency change described in Sec.  
21.93(d), show compliance with the applicable fuel efficiency 
requirements of part 38 of this chapter.
* * * * *

0
10. Amend Sec.  21.183 by adding reserved paragraph (i) and adding 
paragraph (j) to read as follows:


Sec.  21.183  Issue of standard airworthiness certificates for normal, 
utility, acrobatic, commuter, and transport category aircraft; manned 
free balloons; and special classes of aircraft.

* * * * *
    (i) [Reserved]
    (j) Fuel efficiency requirements. No original standard 
airworthiness certificate may be issued under this section unless the 
applicant has demonstrated that the type design complies with the 
applicable fuel efficiency requirements of part 38 of this chapter.

0
11. Amend Sec.  21.187 by revising paragraph (a) to read as follows:


Sec.  21.187  Issue of multiple airworthiness certification.

    (a) An applicant for an airworthiness certificate in the restricted 
category, and in one or more other categories except primary category, 
is entitled to the certificate, if--
    (1) The applicant shows compliance with the requirements for each 
category, when the aircraft is in the configuration for that category;
    (2) The applicant shows that the aircraft can be converted from one 
category to another by removing or adding equipment by simple 
mechanical means;
    (3) The aircraft complies with the applicable requirements of part 
34 of this subchapter; and
    (4) The airplane complies with the applicable requirements of part 
38 of this subchapter.
* * * * *

0
12. Add part 38 to read as follows:

PART 38--AIRPLANE FUEL EFFICIENCY CERTIFICATION

Subpart A--General
Sec.
38.1 Applicability.
38.3 Definitions.
38.4 Compatibility with airworthiness requirements.
38.5 Exemptions.
38.7 Incorporation by reference.
38.9 Relationship to other regulations.
Subpart B--Determining Fuel Efficiency for Subsonic Airplanes
38.11 Fuel efficiency metric.
38.13 Specific air range.
38.15 Reference geometric factor.
38.17 Fuel efficiency limits.
38.19 Change criteria.
38.21 Approval before compliance testing.
38.23 Manual information and limitations.

Appendix A to Part 38--Determination of Airplane Fuel Efficiency Metric 
Value

    Authority:  42 U.S.C. 4321 et seq., 7572; 49 U.S.C. 106(g), 
40113, 44701-44702, 44704; 49 CFR 1.83(c)

Subpart A--General


Sec.  38.1  Applicability.

    (a) Except as provided in paragraph (c) of this section, an 
airplane that is subject to the requirements of 40 CFR part 1030 may 
not exceed the fuel efficiency limits of this part when original type 
certification under this title is sought. This part applies to the 
following airplanes:
    (1) A subsonic jet airplane that has--
    (i) Either--
    (A) A type-certificated maximum passenger seating capacity of 20 
seats or more;
    (B) A maximum takeoff mass (MTOM) greater than 5,700 kg; and
    (C) An application for original type certification that is 
submitted on or after January 11, 2021;
    (ii) Or--
    (A) A type-certificated maximum passenger seating capacity of 19 
seats or fewer;
    (B) A MTOM greater than 60,000 kg; and
    (C) An application for original type certification that is 
submitted on or after January 11, 2021.
    (2) A subsonic jet airplane that has--
    (i) A type-certificated maximum passenger seating capacity of 19 
seats or fewer;
    (ii) A MTOM greater than 5,700 kg, but not greater than 60,000 kg; 
and
    (iii) An application for original type certification that is 
submitted on or after January 1, 2023.
    (3) A propeller-driven airplane that has--
    (i) A MTOM greater than 8,618 kg; and
    (ii) An application for original type certification that is 
submitted on or after January 11, 2021.
    (4) A subsonic jet airplane--
    (i) That is a modified version of an airplane whose type design was 
not certificated under this part;
    (ii) That has a MTOM greater than 5,700 kg;
    (iii) For which an application by the type certificate holder for a 
type design change is submitted on or after January 1, 2023; and
    (iv) For which the first certificate of airworthiness is issued 
with the modified type design.
    (5) A propeller-driven airplane--
    (i) That is a modified version of an airplane whose type design was 
not certificated under this part;
    (ii) That has a MTOM greater than 8,618 kg;
    (iii) For which an application by the type certificate holder for a 
type design change is submitted on or after January 1, 2023; and
    (iv) For which the first certificate of airworthiness is issued 
with the modified type design.
    (6) A subsonic jet airplane that has--
    (i) A MTOM greater than 5,700 kg; and
    (ii) Its first certificate of airworthiness issued on or after 
January 1, 2028.
    (7) A propeller-driven airplane that has--
    (i) A MTOM greater than 8,618 kg; and
    (ii) Its first certificate of airworthiness issued on or after 
January 1, 2028.
    (b) The requirements of this part apply to an airplane for which an 
application for a change in type design is submitted that includes a 
modification that meets the change criteria of Sec.  38.19. A modified 
airplane may not exceed the applicable fuel efficiency limit of this 
part when certification under this chapter is sought. A modified 
airplane is subject to the same fuel efficiency limit of Sec.  38.17 as 
the airplane was certificated to prior to modification.
    (c) The requirements of this part do not apply to:
    (1) Subsonic jet airplanes having a MTOM at or below 5,700 kg.
    (2) Propeller-driven airplanes having a MTOM at or below 8,618 kg.
    (3) Amphibious airplanes.
    (4) Airplanes initially designed, or modified and used, for 
specialized operations. These airplane designs may include 
characteristics or configurations necessary to conduct specialized 
operations that the FAA and the United States Environmental Protection 
Agency (EPA) have determined may cause a significant increase in the 
fuel efficiency metric value.
    (5) Airplanes designed with a reference geometric factor of zero.
    (6) Airplanes designed for, or modified and used for, firefighting.
    (7) Airplanes powered by reciprocating engines.


Sec.  38.3   Definitions.

    For the purpose of showing compliance with this part, the following 
terms have the specified meanings:
    Amphibious airplane means an airplane that is capable of takeoff 
and

[[Page 12655]]

landing on both land and water. Such an airplane uses its hull or 
floats attached to the landing gear for takeoff and landing on water, 
and either extendable or fixed landing gear for takeoff and landing on 
land.
    ICAO Annex 16, Volume III means Volume III of Annex 16 to the 
Convention on International Civil Aviation.
    Maximum takeoff mass (MTOM) is the maximum certified takeoff mass, 
expressed in kilograms, for an airplane type design.
    Performance model is an analytical tool (or a method) validated 
using corrected flight test data that can be used to determine the 
specific air range values for calculating the fuel efficiency metric 
value.
    Reference geometric factor (RGF) is a non-dimensional number 
derived from a two-dimensional projection of the fuselage.
    Specific air range (SAR) is the distance an airplane travels per 
unit of fuel consumed. Specific air range is expressed in kilometers 
per kilogram of fuel.
    Subsonic means an airplane that has not been certificated under 
this title to exceed Mach 1 in normal operation.
    Type certificated maximum passenger seating capacity means the 
maximum number of passenger seats that may be installed on an airplane 
as listed on its type certificate data sheet, regardless of the actual 
number of seats installed on an individual airplane.


Sec.  38.4   Compatibility with airworthiness requirements.

    Unless otherwise approved by the FAA, an airplane used to 
demonstrate compliance with this part must meet all of the 
airworthiness requirements of this chapter required to establish the 
type certification basis of the airplane, for any condition under which 
compliance with this part is being demonstrated. Any procedure used to 
demonstrate compliance, and any flight crew information developed for 
demonstrating compliance with this part, must be consistent with the 
airworthiness requirements of this chapter that constitute the type 
certification basis of the airplane.


Sec.  38.5   Exemptions.

    A petition for exemption from any requirement of this part must be 
submitted to the Administrator in accordance with and meet the 
requirements of part 11 of this chapter. The FAA will consult with the 
EPA on each exemption petition before taking action.


Sec.  38.7   Incorporation by reference.

    The ICAO Doc 7488/3, Manual of the ICAO Standard Atmosphere 
(extended to 80 kilometres (262 500 feet)) (1993), referenced in 
sections A38.2.1.3.1, A38.5.2.2.1.9, and A38.5.2.2.1.10 of appendix A 
to this part, 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. All approved material is available for inspection at 
the FAA and at the National Archives and Records Administration (NARA). 
Contact FAA at: Office of Rulemaking (ARM-1), 800 Independence Avenue 
SW, Washington, DC 20590 (telephone 202-267-9677). For information on 
the availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email 
[email protected]. The ICAO Doc 7488/3 is available for purchase 
from the ICAO Store at 999 Robert-Bourassa Boulevard Montr[eacute]al 
(Quebec) Canada H3C 5H7, (https://store.icao.int/).


Sec.  38.9   Relationship to other regulations.

    In accordance with certain provisions of the Clean Air Act 
Amendments of 1970 (CAA) (42 U.S.C. 7571 et seq.), the United States 
Environmental Protection Agency (EPA) is authorized to set standards 
for aircraft engine emissions in the United States, while the FAA is 
authorized to ensure compliance with those standards under a delegation 
from the Secretary of Transportation (49 CFR 1.83). The fuel efficiency 
limits in Sec.  38.17 are intended to be the same as that promulgated 
by the EPA in 40 CFR part 1030. Accordingly, if the EPA changes any 
regulation in 40 CFR part 1030 that corresponds with a regulation in 
this part, a certification applicant may request a waiver of those 
provisions as they appear in this part in order to comply with part 
1030. In addition, unless otherwise specified in this part, all 
terminology and abbreviations in this part that are defined in 40 CFR 
part 1030 have the meaning specified in part 1030.

Subpart B--Determining Fuel Efficiency for Subsonic Airplanes


Sec.  38.11  Fuel efficiency metric.

    For each airplane subject to this part, or to determine whether a 
modification makes an airplane subject to this part under the change 
criteria of Sec.  38.19, a fuel efficiency metric value must be 
calculated, using the following equation, rounded to three decimal 
places:
[GRAPHIC] [TIFF OMITTED] TR16FE24.041

Where:

The SAR is determined in accordance with Sec.  38.13, and the RGF is 
determined in accordance with Sec.  38.15. The fuel efficiency 
metric value is expressed in units of kilograms of fuel consumed per 
kilometer.


Sec.  38.13   Specific air range.

    (a) For each airplane subject to this part, the SAR of an airplane 
must be determined by either:
    (1) Direct flight test measurements; or
    (2) Using a performance model that is:
    (i) Validated by actual SAR flight test data; and
    (ii) Approved by the FAA before any SAR calculations are submitted.
    (b) For the airplane model, establish a 1/SAR value at each of the 
following reference airplane masses:
    (1) High gross mass: 92 percent MTOM.
    (2) Low gross mass: (0.45 * MTOM) + (0.63 * (MTOM[supcaret]0.924)).
    (3) Mid gross mass: simple arithmetic average of high gross mass 
and low gross mass.
    (c) To obtain (1/SAR)avg as required to determine the 
fuel efficiency metric value described in Sec.  38.11, calculate the 
average of the three 1/SAR values described in paragraph (b) of this 
section. Do not include auxiliary power units in any 1/SAR calculation.
    (d) All determinations made under this section must be made in 
accordance with the procedures applicable to SAR as described in 
appendix A to this part.


Sec.  38.15   Reference geometric factor.

    For each airplane subject to this part, determine the airplane's 
non-dimensional RGF for the fuselage size of each airplane model, 
calculated as follows:
    (a) For an airplane with a single deck, determine the area of a 
surface

[[Page 12656]]

(expressed in m[supcaret]2) bounded by the maximum width of the 
fuselage outer mold line projected to a flat plane parallel with the 
main deck floor and the forward and aft pressure bulkheads except for 
the crew flight deck zone.
    (b) For an airplane with more than one deck, determine the sum of 
the areas (expressed in m[supcaret]2) as follows:
    (1) The maximum width of the fuselage outer mold line, projected to 
a flat plane parallel with the main deck floor by the forward and aft 
pressure bulkheads except for any crew flight deck zone.
    (2) The maximum width of the fuselage outer mold line at or above 
each other deck floor, projected to a flat plane parallel with the 
additional deck floor by the forward and aft pressure bulkheads except 
for any crew flight deck zone.
    (c) Determine the non-dimensional RGF by dividing the area defined 
in paragraph (a) or (b) of this section by 1 m[supcaret]2.
    (d) All measurements and calculations used to determine the RGF of 
an airplane must be made in accordance with the procedures for 
determining RGF in section A38.3 of appendix A to this part.


Sec.  38.17  Fuel efficiency limits.

    (a) The fuel efficiency limits in this section are expressed as 
maximum permitted fuel efficiency metric values, as calculated under 
Sec.  38.11.
    (b) The fuel efficiency metric value of an airplane subject to this 
part may not exceed the following, rounded to three decimal places:

[[Page 12657]]

[GRAPHIC] [TIFF OMITTED] TR16FE24.042


[[Page 12658]]




Sec.  38.19  Change criteria.

    (a) For an airplane that has been shown to comply with Sec.  38.17, 
any subsequent version of that airplane must demonstrate compliance 
with Sec.  38.17 if the subsequent version incorporates a modification 
that either increases:
    (1) The maximum takeoff mass; or
    (2) The fuel efficiency metric value by a percentage that is more 
than the following calculated thresholds.
    (i) For airplanes with a MTOM greater than or equal to 5,700 kg, 
the threshold decreases linearly from 1.35 percent for an airplane with 
a MTOM of 5,700 kg to 0.75 percent for an airplane with a MTOM of 
60,000 kg.
    (ii) For airplanes with a MTOM greater than or equal to 60,000 kg, 
the threshold decreases linearly from 0.75 percent for an airplane with 
a MTOM of 60,000 kg to 0.70 percent for airplanes with a MTOM of 
600,000 kg.
    (iii) For airplanes with a MTOM greater than or equal to 600,000 
kg, the threshold is 0.70 percent.
    (b) For an airplane that has been shown to comply with Sec.  38.17, 
and for any subsequent version of that airplane that incorporates 
modifications that do not increase the MTOM or the fuel efficiency 
metric value in excess of the levels shown in paragraph (a) of this 
section, the fuel efficiency metric value of the modified airplane may 
be reported to be the same as the value prior to modification.
    (c) For an airplane that meets the criteria of Sec.  38.1(a)(4) or 
(5), on or after January 1, 2023, and before January 1, 2028, the 
airplane must demonstrate compliance with Sec.  38.17 if it 
incorporates any modification that increases the fuel efficiency metric 
value of the airplane prior to modification by more than 1.5 percent.


Sec.  38.21  Approval before compliance testing.

    All procedures, weights, configurations, and other information or 
data that are used to establish a fuel efficiency level required by 
this part or in any appendix to this part (including any equivalent 
procedures) must be approved by the FAA prior to use in certification 
tests intended to demonstrate compliance with this part.


Sec.  38.23  Manual information and limitations.

    (a) Information in manuals. The following information must be 
included in any FAA-approved section of a FAA-approved Airplane Flight 
Manual or combination of approved manual material:
    (1) Fuel efficiency level established as required by this part; and
    (2) Maximum takeoff mass at which fuel efficiency level was 
established.
    (b) Limitation. If the fuel efficiency of an airplane is 
established at a weight (mass) that is less than the maximum 
certificated takeoff weight (mass) used to establish the airworthiness 
of the airplane under this chapter, the lower weight (mass) becomes an 
operating limitation of the airplane and that limitation must be 
included in the limitations section of any FAA-approved manual.

Appendix A to Part 38--Determination of Airplane Fuel Efficiency Metric 
Value

A38.1 Introduction
A38.2 Reference specifications for SAR flight tests
A38.3 Determination of reference geometric factor (RGF)
A38.4 Certification test specifications
A38.5 Measurement of specific air range
A38.6 Submission of certification data to the FAA

A38.1 Introduction

    A38.1.1 This appendix describes the processes and procedures for 
determining the fuel efficiency metric value for an airplane subject 
to this part.

A38.1.2 Methods for Determining Specific Air Range (SAR)

    A38.1.2.1 SAR may be determined by either--
    A38.1.2.1.1 Direct flight test measurement at the SAR test 
points, including any corrections of test data to reference 
specifications; or
    A38.1.2.1.2 Use of a performance model.
    A38.1.2.2 For any determination made under section A38.1.2.1.1 
of this appendix, the SAR flight test data must have been acquired 
in accordance with the procedures defined in this appendix and 
approved by the FAA.
    A38.1.2.3 For any determination made under section A38.1.2.1.2 
of this appendix, the performance model must:
    A38.1.2.3.1 Be verified that the model produces the values that 
are the same as FAA-approved SAR flight test data;
    A38.1.2.3.2 Include a detailed description of any test and 
analysis method and any algorithm used so as to allow evaluation by 
the FAA; and
    A38.1.2.3.3 Be approved by the FAA before use.

A38.2 Reference Specifications for SAR Flight Tests

    A38.2.1 The following reference specifications must be 
established when determining SAR values for an airplane. No 
reference specification may exceed any airworthiness limit approved 
for the airplane under this chapter. See section A38.5 of this 
appendix for further information.
    A38.2.1.1 Reference specifications at the airplane level:
    A38.2.1.1.1 Airplane at the reference masses listed in Sec.  
38.13(b);
    A38.2.1.1.2 A combination of altitude and airspeed selected by 
the applicant;
    A38.2.1.1.3 Airplane in steady, unaccelerated, straight and 
level flight;
    A38.2.1.1.4 Airplane in longitudinal and lateral trim;
    A38.2.1.1.5 Airplane gravitational acceleration when travelling 
in the direction of true North in still air at the reference 
altitude and a geodetic latitude of 45.5 degrees, based on 
g0 (g0 is 9.80665 m/s\2\, which is the 
standard acceleration due to gravity at sea level and a geodetic 
latitude of 45.5 degrees);
    A38.2.1.1.6 A reference airplane center of gravity (CG) position 
selected by the applicant to be representative of the mid-CG point 
relevant to design cruise performance at each of the three reference 
airplane masses; and
    A38.2.1.1.7 A wing structural loading condition defined by the 
applicant that is representative of operations conducted in 
accordance with the airplane's maximum payload capability.
    A38.2.1.2 Reference specifications at the engine level:
    A38.2.1.2.1 Electrical and mechanical power extraction and bleed 
flow relevant to design cruise performance, as selected by the 
applicant;
    Note 1 to A38.2.1.2.1--Power extraction and bleed flow 
attributable to the use of optional equipment such as passenger 
entertainment systems need not be included.
    A38.2.1.2.2 Engine stability bleeds operating according to the 
manufacturer's normal schedule for the engine; and
    A38.2.1.2.3 Engines with at least 15 cycles or 50 engine flight 
hours.
    A38.2.1.3 Other reference specifications:
    A38.2.1.3.1 ICAO standard day atmosphere (Doc 7488/3, 3rd 
edition 1993, titled ``Manual of the ICAO Standard Atmosphere 
(extended to 80 kilometres (262 500 feet))'') (incorporated by 
reference, see Sec.  38.7); and
    A38.2.1.3.2 Fuel lower heating value equal to 43.217 MJ/kg (18,-
580 BTU/lb).
    A38.2.2 If any test conditions are not the same as the reference 
specifications of this appendix, the test conditions must be 
corrected to the reference specifications as described in section 
A38.5 of this appendix.

A38.3 Determination of Reference Geometric Factor (RGF)

    A38.3.1 This section provides additional information for 
determining the RGF, as required by Sec.  38.15.
    A38.3.2 The area that defines RGF includes all pressurized space 
on a single or multiple decks including aisles, assist spaces, 
passageways, stairwells and areas that can accommodate cargo or 
auxiliary fuel containers. It does not include permanent integrated 
fuel tanks within the cabin, or any unpressurized fairings, crew 
rest or work areas, or cargo areas that are not on the main or upper 
deck (e.g., `loft' or under floor areas). RGF does not include the 
flight deck crew zone.
    A38.3.3 The aft boundary to be used for calculating RGF is the 
aft pressure bulkhead. The forward boundary is the forward pressure 
bulkhead, not including the flight deck crew zone.

[[Page 12659]]

    A38.3.4 Areas that are accessible to both crew and passengers 
are not considered part of the flight deck crew zone. For an 
airplane that has a flight deck door, the aft boundary of the flight 
deck crew zone is the plane of the flight deck door. For an airplane 
that has no flight deck door or has optional interior configurations 
that include different locations of the flight deck door, the aft 
boundary is determined by the configuration that provides the 
smallest available flight deck crew zone. For airplanes certificated 
for single-pilot operation, the flight deck crew zone is measured as 
half the width of the flight deck.
    A38.3.5 Figures A38-1 and A38-2 of this appendix provide a 
notional view of the RGF boundary conditions.
[GRAPHIC] [TIFF OMITTED] TR16FE24.043


[[Page 12660]]


[GRAPHIC] [TIFF OMITTED] TR16FE24.044

A38.4 Certification Test Specifications

    A38.4.1 Certification Test Specifications. This section prescribes 
the specifications under which an applicant must conduct SAR 
certification tests.
    A38.4.2 Flight Test Procedures
    A38.4.2.1 Before a Test Flight. The test flight procedures must 
include the following elements and must be approved by the FAA before 
any test flight is conducted:
    A38.4.2.1.1 Airplane conformity. The test airplane must conform to 
the critical configuration of the type design for which certification 
is sought.
    A38.4.2.1.2 Airplane weight. The test airplane must be weighed. Any 
change in mass after the weighing and prior to the test flight must be 
accounted for.
    A38.4.2.1.3 Fuel. The fuel used for each flight test must meet the 
specification defined in either ASTM D1655-15 (titled ``Standard 
Specification for Aviation Turbine Fuels''), UK MoD Defense Standard 
91-91, Issue 7, Amendment 3 (titled ``Turbine Fuel, Kerosene Type, Jet 
A-1, NATO Code F-35; Join Services Designation; AVTUR''), or as 
approved by FAA.
    A38.4.2.1.4 Fuel lower heating value. The lower heating value of 
the fuel used on a test flight must be determined from a sample of fuel 
used for the test flight. The lower heating value of the fuel sample 
must be used to correct measured data to reference specifications. The 
determination of lower heating value and the correction to reference 
specifications are subject to approval by the FAA.
    A38.4.2.1.4.1 The fuel lower heating value may be determined in 
accordance with ASTM D4809-13 ``Standard Test Method for Heat of 
Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision 
Method)'', or as approved by the FAA.
    A38.4.2.1.4.2 The fuel sample may be representative of the fuel 
used for each flight test and should not have errors or variations due 
to fuel being uplifted from multiple sources, fuel tank selection, or 
fuel layering in a tank.
    A38.4.2.1.5 Fuel specific gravity and viscosity. When volumetric 
fuel flow meters are used, the specific gravity and viscosity of the 
fuel used on a test flight must be determined from a sample of fuel 
used for the test flight.
    A38.4.2.1.5.1 The fuel specific gravity may be determined in 
accordance with ASTM D4052-11 ``Standard Test Method for Density, 
Relative Density, and API Gravity of Liquids'', or as approved by FAA.
    A38.4.2.1.5.2 The fuel kinematic viscosity may be determined in 
accordance with ASTM D445-15 (titled ``Standard Test Method for 
Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation 
of Dynamic Viscosity)''), or as approved by FAA.
    A38.4.2.2 Flight Test Procedures and Test Condition Stability. An 
applicant must conduct each flight test in accordance with the flight 
test procedures and the stability conditions as follows:
    A38.4.2.2.1 Flight Test Procedure. The following procedures must be 
maintained during each flight used to gather data for determining SAR 
values:
    A38.4.2.2.1.1 To the extent that is practicable, the airplane is 
flown at constant pressure altitude and constant heading along isobars;
    A38.4.2.2.1.2 The engine thrust/power setting is stable for 
unaccelerated level flight;
    A38.4.2.2.1.3 The airplane is flown as close as practicable to the 
reference specifications to minimize the magnitude of any correction;
    A38.4.2.2.1.4 Changes in trim or engine power/thrust settings, 
engine stability and handling bleeds, or electrical and mechanical 
power extraction (including bleed flow) are avoided or minimized as 
practicable; and
    A38.4.2.2.1.5 There is no unnecessary movement of on-board 
personnel.
    A38.4.2.2.2 Test Condition Stability. To obtain a valid SAR 
measurement, the following conditions must be maintained during each 
test flight, including the indicated tolerances for at least 1 minute 
while SAR data is acquired:
    A38.4.2.2.2.1 Mach number within 0.005;

[[Page 12661]]

    A38.4.2.2.2.2 Ambient temperature within 1 [deg]C;
    A38.4.2.2.2.3 Heading within 3 degrees;
    A38.4.2.2.2.4 Track within 3 degrees;
    A38.4.2.2.2.5 Drift angle less than 3 degrees;
    A38.4.2.2.2.6 Ground speed within 3.7 km/h (2 kt);
    A38.4.2.2.2.7 Difference in ground speed at the beginning of the 
SAR measurement from the ground speed at the end of the SAR measurement 
within 2.8 km/h/min (1.5 kt/min); and
    A38.4.2.2.2.8 Pressure altitude within 23 m (75 ft).
    A38.4.2.2.3 Alternatives to the stable test condition criteria of 
section A38.4.2.2.2 of this appendix may be used provided that 
stability is sufficiently demonstrated to the FAA.
    A38.4.2.2.4 Data obtained at test points that do not meet the 
stability criteria of section A38.4.2.2.2 may be acceptable as an 
equivalent procedure, subject to FAA approval.
    A38.4.2.2.5 SAR measurements at the test points must be separated 
by either:
    A38.4.2.2.5.1 Two minutes; or
    A38.4.2.2.5.2 An exceedance of one or more of the stability 
criteria limits described in A38.4.2.2.2.
    A38.4.2.3 Verification of Airplane Mass at Test Conditions
    A38.4.2.3.1 The procedure for determining the mass of the airplane 
at each test condition must be approved by the FAA.
    A38.4.2.3.2 The mass of the airplane during a flight test is 
determined by subtracting the fuel used from the mass of the airplane 
at the start of the test flight. The accuracy of the determination of 
the fuel used must be verified by:
    A38.4.2.3.2.1 Weighing the test airplane on calibrated scales 
before and after the SAR test flight;
    A38.4.2.3.2.2 Weighing the test airplane before and after another 
test flight that included a cruise segment, provided that flight occurs 
within one week or 50 flight hours (at the option of the applicant) of 
the SAR test flight and using the same, unaltered fuel flow meters; or
    A38.4.2.3.2.3 Other methods as approved by the FAA.

A38.5 Measurement of Specific Air Range

    A38.5.1 Measurement System
    A38.5.1.1 The following parameters must be recorded at a minimum 
sampling rate of 1 Hertz (cycle per second):
    A38.5.1.1.1 Airspeed;
    A38.5.1.1.2 Ground speed;
    A38.5.1.1.3 True airspeed;
    A38.5.1.1.4 Fuel flow;
    A38.5.1.1.5 Engine power setting;
    A38.5.1.1.6 Pressure altitude;
    A38.5.1.1.7 Temperature;
    A38.5.1.1.8 Heading;
    A38.5.1.1.9 Track; and
    A38.5.1.1.10 Fuel used (for the determination of gross mass and CG 
position).
    A38.5.1.2 The following parameters must be recorded:
    A38.5.1.2.1 Latitude;
    A38.5.1.2.2 Engine bleed positions and power off-takes; and
    A38.5.1.2.3 Power extraction (electrical and mechanical load).
    A38.5.1.3 The value of each parameter used for the determination of 
SAR (except for ground speed) is the simple arithmetic average of the 
measured values for that parameter obtained throughout the stable test 
condition described in section A38.4.2.2.2 of this appendix.
    A38.5.1.4 For ground speed, the value is the rate of change of 
ground speed during the SAR test measurement. The rate of change of 
ground speed during the SAR measurement must be used to evaluate and 
correct any acceleration or deceleration that might occur during the 
SAR measurement.
    A38.5.1.5 Each measurement device must have sufficient resolution 
to determine that the stability of a parameter defined in section 
A38.4.2.2.2 of this appendix is maintained during SAR measurement.
    A38.5.1.6 The SAR measurement system consists of the combined 
instruments and devices, and any associated procedures, used to acquire 
the following parameters necessary to determine SAR:
    A38.5.1.6.1 Fuel flow;
    A38.5.1.6.2 Mach number;
    A38.5.1.6.3 Altitude;
    A38.5.1.6.4 Airplane mass;
    A38.5.1.6.5 Ground speed;
    A38.5.1.6.6 Outside air temperature;
    A38.5.1.6.7 Fuel lower heating value; and
    A38.5.1.6.8 CG.
    A38.5.1.7 The SAR value is affected by the accuracy of each element 
that comprises the SAR measurement system. The cumulative error 
associated with the SAR measurement system is defined as the root sum 
of squares (RSS) of the individual accuracies.
    A38.5.1.8 If the absolute value of the cumulative error of the 
overall SAR measurement system is greater than 1.5 percent, a penalty 
equal to the amount that the RSS value exceeds 1.5 percent must be 
applied to the SAR value that has been corrected to reference 
specifications (see section A38.5.2 of this appendix). If the absolute 
value of the cumulative error of the overall SAR measurement system is 
less than or equal to 1.5 percent, no penalty will be applied.
    A38.5.2 Calculation of Specific Air Range from Measured Data
    A38.5.2.1 Calculating SAR. SAR must be calculated using the 
following equation:

SAR = TAS/Wf

Where:

TAS is the true airspeed and Wf is total airplane fuel 
flow.

    A38.5.2.2 Correcting Measured SAR Values to Reference 
Specifications
    A38.5.2.2.1 The measured SAR values must be corrected to the 
reference specifications listed in A38.2 of this appendix. Unless 
otherwise approved by the FAA, corrections to reference specifications 
must be applied for each of the following measured parameters:
    A38.5.2.2.1.1 Acceleration/deceleration (energy). Drag 
determination is based on an assumption of steady, unaccelerated 
flight. Acceleration or deceleration occurring during a test condition 
affects the assessed drag level. The reference specification is in 
section A38.2.1.1.3 of this appendix.
    A38.5.2.2.1.2 Aeroelastics. Wing aeroelasticity may cause a 
variation in drag as a function of airplane wing mass distribution. 
Airplane wing mass distribution will be affected by the fuel load 
distribution in the wings and the presence of any external stores. The 
reference specification is in section A38.2.1.1.7 of this appendix.
    A38.5.2.2.1.3 Altitude. The altitude at which the airplane is flown 
affects the fuel flow. The reference specification is in section 
A38.2.1.1.2 of this appendix.
    A38.5.2.2.1.4 Apparent gravity. Acceleration, caused by the local 
effect of gravity, and inertia, affect the test weight of the airplane. 
The apparent gravity at the test conditions varies with latitude, 
altitude, ground speed, and direction of motion relative to the Earth's 
axis. The reference gravitational acceleration is the gravitational 
acceleration for the airplane travelling in the direction of true North 
in still air at the reference altitude, a geodetic latitude of 45.5 
degrees, and based on g0 (see section A38.2.1.1.5 of this 
appendix).
    A38.5.2.2.1.5 CG position. The position of the airplane CG affects 
the drag due to longitudinal trim. The reference specification is in 
section A38.2.1.1.6 of this appendix.
    A38.5.2.2.1.6 Electrical and mechanical power extraction and bleed 
flow. Electrical and mechanical power extraction, and bleed flow affect 
the fuel

[[Page 12662]]

flow. The reference specifications are in sections A38.2.1.2.1 and 
A38.2.1.2.2 of this appendix.
    A38.5.2.2.1.7 Engine deterioration level. The requirement in 
section A38.2.1.2.3 of this appendix addresses the minimum 
deterioration of an engine that is used to determine SAR. Since engine 
deterioration is rapid when an engine is new, when used for SAR 
determination:
    A38.5.2.2.1.7.1 Subject to FAA approval, an engine having less 
deterioration than the reference deterioration level in section 
A38.2.1.2.3 of this appendix must correct the fuel flow to the 
reference deterioration using an approved method.
    A38.5.2.2.1.7.2 An engine with greater deterioration than the 
reference deterioration level in section A38.2.1.2.3 of this appendix 
may be used, and no correction is permitted.
    A38.5.2.2.1.8 Fuel lower heating value. The fuel lower heating 
value defines the energy content of the fuel. The lower heating value 
directly affects the fuel flow at a given test condition. The reference 
specification is in section A38.2.1.3.2 of this appendix.
    A38.5.2.2.1.9 Reynolds number. The Reynolds number affects airplane 
drag. For a given test condition the Reynolds number is a function of 
the density and viscosity of air at the test altitude and temperature. 
The reference Reynolds number is derived from the density and viscosity 
of air from the ICAO standard atmosphere at the reference altitude (see 
sections A38.2.1.1.2 and A38.2.1.3.1 of this appendix, incorporated by 
reference see Sec.  38.7).
    A38.5.2.2.1.10 Temperature. The ambient temperature affects the 
fuel flow. The reference temperature is the standard day temperature 
from the ICAO standard atmosphere at the reference altitude (see 
section A38.2.1.3.1 of this appendix, incorporated by reference see 
Sec.  38.7).
    Note 2 to A38.5.2.2.1.10--Post-flight data analysis includes the 
correction of measured data for data acquisition hardware response 
characteristics (e.g., system latency, lag, offset, buffering, etc.).
    A38.5.2.2.2 Correction methods are subject to the approval of the 
FAA.
    A38.5.2.3 Using Specific Air Range to Determine the Fuel Efficiency 
Metric Value
    A38.5.2.3.1 Calculate the SAR values for each of the three 
reference masses as described in Sec.  38.13, including any corrections 
to reference specifications, as required under this part. The final SAR 
value for each reference mass is the simple arithmetic average of all 
valid test points at the appropriate gross mass, or derived from a 
validated performance model. No data acquired from a valid test point 
may be omitted unless approved by the FAA.
    A38.5.2.3.2 When an FAA-approved performance model is used, 
extrapolations to aircraft masses other than those tested may be 
approved when such extrapolations are consistent with accepted 
airworthiness practices. Since a performance model must be based on 
data covering an adequate range of lift coefficient, Mach number, and 
thrust specific fuel consumption, no extrapolation of those parameters 
is permitted.
    A38.5.3 Validity of Results
    A38.5.3.1 A 90 percent confidence interval must be calculated for 
each of the SAR values at the three reference masses.
    A38.5.3.2 If the 90 percent confidence interval of the SAR value at 
any of the three reference airplane masses--
    A38.5.3.2.1 Is less than or equal to 1.5 percent, the 
SAR value may be used.
    A38.5.3.2.2 Exceeds 1.5 percent, a penalty equal to the 
amount that the 90 percent confidence interval exceeds 1.5 
percent must be applied to the SAR value, as approved by the FAA.
    A38.5.3.3 If clustered data is acquired separately for each of the 
three gross mass reference points, the minimum sample size acceptable 
for each of the three gross mass SAR values is six.
    A38.5.3.4 If SAR data is collected over a range of masses, the 
minimum sample size is 12 and the 90 percent confidence interval is 
calculated for the mean regression line through the data.

A38.6 Submission of Certification Data to the FAA

    The following information must be provided to the FAA in the 
certification reports for each airplane type and model for which fuel 
efficiency certification under this part is sought.
    A38.6.1 General Information
    A38.6.1.1 Designation of the airplane type and model:
    A38.6.1.2 Configuration of the airplane, including CG range, number 
and type designation of engines and, if fitted, propellers, and any 
modifications or non-standard equipment expected to affect the fuel 
efficiency characteristics;
    A38.6.1.3 MTOM used for certification under this part;
    A38.6.1.4 All dimensions needed for calculation of RGF; and
    A38.6.1.5 Serial number of each airplane used to establish fuel 
efficiency certification in accordance with this part.
    A38.6.2 Reference Specifications. The reference specifications used 
to determine any SAR value as described in section A38.2 of this 
appendix.
    A38.6.3 Test Data. The following measured test data, including any 
corrections for instrumentation characteristics, must be provided for 
each of the test measurement points used to calculate the SAR values 
for each of the reference masses defined in Sec.  38.13(b):
    A38.6.3.1 Airspeed, ground speed and true airspeed;
    A38.6.3.2 Fuel flow;
    A38.6.3.3 Pressure altitude;
    A38.6.3.4 Static air temperature;
    A38.6.3.5 Airplane gross mass and CG for each test point;
    A38.6.3.6 Levels of electrical and mechanical power extraction and 
bleed flow;
    A38.6.3.7 Engine performance;
    A38.6.3.7.1 For jet airplanes, engine power setting; or
    A38.6.3.7.2 For propeller-driven airplanes, shaft horsepower or 
engine torque, and propeller rotational speed;
    A38.6.3.8 Fuel lower heating value;
    A38.6.3.9 When volumetric fuel flow meters are used, fuel specific 
gravity and kinematic viscosity (see section A38.4.2.1.5. of this 
appendix);
    A38.6.3.10 The cumulative error (RSS) of the overall measurement 
system (see section A38.5.1.7 of this appendix);
    A38.6.3.11 Heading, track and latitude;
    A38.6.3.12 Stability criteria (see section A38.4.2.2.2 of this 
appendix); and
    A38.6.3.13 Description of the instruments and devices used to 
acquire the data needed for the determination of SAR, and the 
individual accuracies of the equipment relevant to their effect on SAR 
(see sections A38.5.1.6 and A38.5.1.7 of this appendix).
    A38.6.4 Calculations and Corrections of SAR Test Data to Reference 
Specifications. The measured SAR test data, all corrections of the 
measured data to the reference specifications, and the SAR values 
calculated from the corrected data must be provided for each of the 
test measurement points.
    A38.6.5 Calculated Values. The following values must be provided 
for each airplane used to establish fuel efficiency certification in 
accordance with this part:
    A38.6.5.1 SAR (km/kg) for each reference airplane mass and the 
associated 90 percent confidence interval;
    A38.6.5.2 Average of the 1/SAR values;
    A38.6.5.3 RGF; and
    A38.6.5.4 Fuel efficiency metric value.

[[Page 12663]]

PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL 
OPERATIONS

0
13. The authority citation for part 121 continues to read as follows:

    Authority:  49 U.S.C. 106(f), 106(g), 40103, 40113, 40119, 
41706, 42301 preceding note added by Pub. L. 112-95, sec. 412, 126 
Stat. 89, 44101, 44701-44702, 44705, 44709-44711, 44713, 44716-
44717, 44722, 44729, 44732; 46105; Pub. L. 111-216, 124 Stat. 2348 
(49 U.S.C. 44701 note); Pub. L. 112-95 126 Stat 62 (49 U.S.C. 44732 
note).


0
14. Amend Sec.  121.141 by revising paragraph (b) introductory text to 
read as follows:


Sec.  121.141  Airplane flight manual.

* * * * *
    (b) In each airplane required to have an airplane flight manual in 
paragraph (a) of this section, the certificate holder shall carry 
either the manual required by Sec.  121.133, if it contains the 
information required for the applicable flight manual and this 
information is clearly identified as flight manual requirements, or an 
approved Airplane Manual. If the certificate holder elects to carry the 
manual required by Sec.  121.133, the certificate holder may revise the 
operating procedures sections and modify the presentation of 
performance data, except for the information required by Sec.  38.23 of 
this chapter identifying compliance with the fuel efficiency 
requirements of part 38 of this chapter, from the applicable flight 
manual if the revised operating procedures and modified performance 
data presentation are--
* * * * *

PART 125--CERTIFICATION AND OPERATIONS: AIRPLANES HAVING A SEATING 
CAPACITY OF 20 OR MORE PASSENGERS OR A MAXIMUM PAYLOAD CAPACITY OF 
6,000 POUNDS OR MORE; AND RULES GOVERNING PERSONS ON BOARD SUCH 
AIRCRAFT

0
15. The authority citation for part 125 continues to read as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44705, 
44710-44711, 44713, 44716-44717, 44722.


0
16. Amend Sec.  125.75 by revising paragraph (b) to read as follows:


Sec.  125.75   Airplane flight manual.

* * * * *
    (b) Each certificate holder shall carry the approved Airplane 
Flight Manual or the approved equivalent aboard each airplane it 
operates. A certificate holder may elect to carry a combination of the 
manuals required by this section and Sec.  125.71. If it so elects, the 
certificate holder may revise the operating procedures sections and 
modify the presentation of performance from the applicable Airplane 
Flight Manual if the revised operating procedures and modified 
performance data presentation are approved by the Administrator. Any 
approved equivalent must include the information required by Sec.  
38.23 of this chapter identifying compliance with the fuel efficiency 
requirements of part 38 of this chapter.

    Issued under authority provided in 42 U.S.C. 4321 et seq., 7572, 
49 U.S.C. 106(f), 40133, 44701-44701, 44703, and 44704 in 
Washington, DC.
Michael Gordon Whitaker,
Administrator.
[FR Doc. 2024-02330 Filed 2-15-24; 8:45 am]
BILLING CODE 4910-13-P