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

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

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

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

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

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

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

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

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

E. Annual Reporting Requirement

    In 2012, the EPA adopted an annual reporting requirement as part of
a rulemaking to adopt updated aircraft engine NOX
standards.\97\ This provision, adopted into 40 CFR 87.42, requires the
manufacturers of covered engines to annually report data to the EPA
which includes information on engine identification and
characteristics, emissions data for all regulated pollutants, and
production volumes. In 2018, the EPA issued an information collection
request (ICR) which renewed the existing ICR and added PM information
to the list of required data.98 99 However, that 2018 ICR
was not part of a rulemaking effort, and the new PM reporting
requirements were not incorporated into the CFR at that time. Further,
that 2018 ICR is currently being renewed (in an action separate from
this proposal), and the EPA is proposing as part of that effort to add
some additional data elements to the ICR (specifically, the emission
indices for HC, CO, and NOX at each mode of the LTO
cycle).100 101 The EPA is now proposing to formally
incorporate all aspects of that ICR, as proposed to be renewed, into
the CFR in the proposed section 1031.150. It is important to note that
the incorporation of the PM reporting requirements into the CFR would
not create a new requirement for the manufacturers of aircraft engines.
Rather, it would simply incorporate the existing reporting requirements
(as proposed to be amended and renewed in a separate action) into the
CFR for ease of use by having all the reporting requirements readily
available in the CFR.
---------------------------------------------------------------------------

    \97\ 77 FR 36342, June 18, 2012.
    \98\ 83 FR 44621, August 31, 2018.
    \99\ U.S. EPA, Aircraft Engines--Supplemental Information
Related to Exhaust Emissions (Renewal), OMB Control Number 2060-
0680, ICR Reference Number<PHONE_NUMBER>-08, December 17, 2018.
Available at https://www.reginfo.gov/public/do/PRAViewICR?ref_nbr=201809-2060-008, last accessed November 15, 2021.
    \100\ 86 FR 24614, May 7, 2021.
    \101\ Documentation and Public comments are available at:
https://www.regulations.gov/docket/EPA-HQ-OAR-2016-0546, last
accessed November 15, 2021.
---------------------------------------------------------------------------

    The EPA uses the collection of information to help conduct
technology assessments, develop aircraft emission inventories (for
current and future inventories), and inform our policy decisions--
including future standard-setting actions. The information enables the
EPA to further understand the characteristics of aircraft engines that
are subject to emission standards--and engines proposed to be subject
to the PM emission standards--and engines impact on emission
inventories. In addition, the information helps the EPA set appropriate
and achievable emission standards and related requirements for aircraft
engines. Annually updated information helps in assessing technology
trends and their impacts on national emissions inventories. Also, it
assists the EPA to stay abreast of developments in the aircraft engine
industry.
    As discussed in Section VII, the EPA is proposing to migrate the
existing 40 CFR part 87 regulatory text to a new 40 CFR part 1031. Part
of that effort includes clarifying portions of the regulatory text for
ease of use. In the existing 40 CFR 87.42(c)(6), the regulatory text
does not specifically spell out some required data, but instead relies
on incorporation by reference for a detailed listing of required items.
40 CFR 87.42(c)(6) references the data reporting provisions in ICAO's
Annex 16, Volume II and lists the data from this Annex that is not
required by the EPA's reporting requirement. For future ease of use,
the EPA is proposing in the new 40 CFR 1031.150 to explicitly list all
the required items rather than continuing the incorporation by
reference approach in the existing reporting regulations. The reader is
encouraged to consult the proposed 40 CFR 1031.150 text for a complete
list of the required reporting items. However, as previously mentioned,
this list contains all the currently required items as well as the HC,
CO and NOX emission indices as proposed in the separate ICR
renewal action. Finally, the EPA is proposing to incorporate by
reference Appendix 8 of

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

V. Aggregate PM Inventory Impacts

    The number of aircraft landings and takeoffs (LTO) affects PM
emissions that contribute to the local air quality near airports. The
LTO emissions are defined as emissions between ground level and an
altitude of about 3,000 feet. They are composed of emissions during
departure operations (from taxi-out movement from gate to runway,
aircraft take-off run and climb-out to 3,000 feet), and during arrival
operations (emissions from approach at or below 3,000 feet down to
landing on the ground and taxi-in from runway to gate). These LTO
emissions directly affect the ground level air quality at the vicinity
of the airport since they are within the local mixing height. Depending
on the meteorological conditions, the emissions will be mixed with
ambient air down to ground level, dispersed, and transported to areas
downwind from the airport with elevated concentration levels.\102\
---------------------------------------------------------------------------

    \102\ A local air quality ``. . . emissions inventory for
aircraft focuses on the emission characteristics of this source
relative to the vertical column of air that ultimately affects
ground level pollutant concentrations. This portion of the
atmosphere, which begins at the earth's surface and is simulated in
air quality models, is often referred to as the mixing zone'' or
mixing height. (See page 137.) The air in this mixing height is
completely mixed and pollutants emitted anywhere within it will be
carried down to ground level. (See page 143.) ``The aircraft
operations of interest within the [mixing height] are defined as the
[LTO] cycle.'' (See page 137.) The default mixing height in the U.S.
is 3,000 feet. (EPA, 1992: Procedures for Emission Inventory
Preparation--Volume IV: Mobile Sources, EPA420-R-92-009. Available
at https://nepis.epa.gov (last accessed June 23, 2021).
---------------------------------------------------------------------------

    As described earlier in Section III, aircraft PM emissions are
composed of both volatile and nonvolatile PM components.\103\ Starting
from an air and fuel mixture of 16.3 percent oxygen (O2),
75.2 percent nitrogen (N2), and 8.5 percent fuel, an
aircraft engine yields combustion products of 27.6 percent water
(H2O), 72 percent carbon dioxide (CO2), and ~0.02
percent sulfur oxide (SOX) with only 0.4 percent incomplete
residual products which can be broken down to 84 percent nitrogen oxide
(NOX), 11.8 percent carbon monoxide (CO), 4 percent unburned
hydrocarbons (UHC), 0.1 percent PM and trace amount of other
products.\104\ Although the PM emissions are a small fraction of total
engine exhaust, the composition and morphology of PM are complex and
dynamic. While the proposed emission test procedures focus only on
measuring nonvolatile PM (black carbon), our emissions inventory
includes estimates for volatile PM (organic, lubrication oil residues
and sulfuric acid) as well.
---------------------------------------------------------------------------

    \103\ ICAO: 2019, ICAO Environmental Report, Available at
https://www.icao.int/environmental-protection/Documents/ICAO-ENV-Repor/t2019-F1-WEB%20(1).pdf (last accessed on November 15,
2021,2021). See pages 100 and 101 for a description of non-volatile
PM and volatile PM.
    ``At the engine exhaust, particulate emissions mainly consist of
ultrafine soot or black carbon emissions. Such particles are called
``non-volatile'' (nvPM). They are present at the high temperatures
at the engine exhaust and they do not change in mass or number as
they mix and dilute in the exhaust plume near the aircraft. The
geometric mean diameter of these particles is much smaller than
PM2.5 (geometric mean diameter of 2.5 Microns) and ranges
roughly from 15nm to 60nm (0.06 Microns). These are classified as
ultrafine particles (UFP).'' (See page 100.) ``The new ICAO standard
is a measure to control the ultrafine non-volatile particulate
matter emissions emitted at the engine exit . . .'' (See page 101.)
    ``Additionally, gaseous emissions from engines can also condense
to produce new particles (i.e., volatile particulate matter--vPM),
or coat the emitted soot particles. Gaseous emissions species react
chemically with ambient chemical constituents in the atmosphere to
produce the so called secondary particulate matter. Volatile
particulate matter is dependent on these gaseous precursor
emissions. While these precursors are controlled by gaseous emission
certification and the fuel composition (e.g., sulfur content) for
aircraft gas turbine engines, the volatile particulate matter is
also dependent on the ambient air background composition.'' (See
pages 100 and 101.)
    \104\ European Monitoring and Evaluation Programme/European
Environment Agency, Air Pollutant Emission Inventory Guidebook 2019;
Available at https://www.eea.europa.eu/themes/air/air-pollution-sources-1/emep-eea-air-/pollutant-/emission-/inventory-guidebook/emep (last accessed June 26, 2021).
---------------------------------------------------------------------------

A. Aircraft Engine PM Emissions for Modeling

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

    \105\ SAE Aerospace Information Reports, AIR5715, Procedure for
the Calculation of Aircraft Emissions, 2009, SAE International.
    \106\ Wayson RL, Fleming GG, Iovinelli R. Methodology to
Estimate Particulate Matter Emissions from Certified Commercial
Aircraft Engines. J Air Waste Management Assoc. 2009 Jan 1; 59(1).
---------------------------------------------------------------------------

    In addition, as described earlier (Sections III.A and IV), volatile
PM and nvPM together make up total PM. The FOA3 method for volatile PM
is based on the jet fuel organics \107\ and sulfur content. Since the
total PM inventory is the emissions inventory we are estimating for
this proposed rulemaking, we are including the volatile PM emission
estimates from the FOA3 method in our emission inventory.
---------------------------------------------------------------------------

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

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

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

    \108\ Annex 16 Vol. II Appendix 8 Note 2.
---------------------------------------------------------------------------

    The EPA led the effort within the SAE E-31 committee to develop the
methodology to correct for system losses. This effort at E-31 resulted
in the development and publication of AIR 6504 and ARP 6481 describing
how to correct for system losses. ICAO has incorporated this same
procedure into Annex 16 Vol. II Appendix 8.
    The engine exit emissions rate, which is corrected for system
losses, is specific to each measurement system and to each engine. The
calculation is an iterative function based upon the measured nvPM mass
and nvPM number values and the geometry of the measurement system.
Manufacturers provide the corrected emissions values to the ICAO EDB
and to the EPA.
    When calculating emissions inventories, these corrected EIs will be
used rather than the values used to show compliance with emission
standards. These measured EIs are only for the nonvolatile component of
PM, and an approximation method will still be required for quantifying
the volatile PM inventory.
3. Improvements to Calculated EIs
    The new version of the approximation method, known as FOA4, has
been developed by CAEP to improve nvPM mass estimation and to extend
the methodology to nvPM number based on the newly available PM
measurement data.\109\ Since PM mass and PM number are two different
measurement metrics of the same pollutant, PM, they can be converted to
each other if the size and density distribution of the pollutant can be
characterized.\110\ FOA4 was not used in the baseline emission rates
for this proposed rulemaking.
---------------------------------------------------------------------------

    \109\ ICAO: Second edition, 2020: Doc 9889, Airport Air Quality
Manual. Order Number 9889. See Attachment D to Appendix 1 of Chapter
3. Doc 9889 can be ordered from ICAO website: https://store.icao.int/en/airport-air-/quality-manual/-doc-9889 (last
accessed June 28, 2021).
    \110\ Based on the newly available measurement data and inputs
from technical experts in SAE E-31 Aircraft Exhaust Emissions
Measurement Committee, CAEP has determined that a set of fixed
geometric mean diameters (GMDs) of 20/20/40/40 nanometers for the
four LTO modes (idle-taxi/approach/climbout/take-off) fits the data
the best. Along with the assumptions of a log-normal size
distribution, a geometric standard deviation of 1.8, and an
effective density of 1,000 kg/m[caret]3 for the exhaust plume at the
engine exit plane, nvPM mass EI and nvPM number EI of LTO mode k can
be converted to each other.
---------------------------------------------------------------------------

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

B. Baseline PM Emission Inventory

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

    \111\ 2017 National Emissions Inventory: Aviation Component,
Eastern Research Group, Inc., July 25, 2019, EPA Contract No. EP-C-
17-011, Work Order No. 2-19.
    \112\ See section 3.2 for airports and aircraft related
emissions in the Technical Supporting Document for the 2017 National
Emissions Inventory, January 2021 Updated Release; https://www.epa.gov/sites/production/files/2021-02/documents/nei2017_tsd_full_jan2021.pdf.
    \113\ https://www.epa.gov/air-emissions/-inventories/2017-/national-emissions-/inventory-nei-data.
---------------------------------------------------------------------------

    The aviation emissions developed for the NEI include emissions
associated with airport activities in commercial aircraft, air taxi
aircraft,\114\ general aviation aircraft, military aircraft, auxiliary
power units, and ground support equipment. All emissions from aircraft
with gas turbine engines greater than 26.7 kN rated output from the
aircraft categories described earlier, except military aircraft, are
used in the emissions inventory for this proposed rule (which is a
subset of the aviation emissions inventory). To estimate emissions,
2017 activity data by states were compiled and supplemented with
publicly available FAA data. The FAA activity data included 2017 T-100
\115\ dataset, 2014 Terminal Area Forecast (TAF) \116\ data, 2014 Air
Traffic Activity Data System (ATADS) \117\ data, and 2014 Airport
Master Record (form 5010) \118\ data.\119\ The NEI used the FAA's
Aviation Environmental Design Tool (AEDT) \120\ version 2d to estimate
emissions for aircraft that were in the AEDT database. The NEI used a
more general estimation methodology to account for emissions from
aircraft types not available in AEDT by multiplying the reported
activities by fleet-wide average emission factors of generic aircraft
types (or by aircraft category--e.g., general aviation or air
taxi).\121\
---------------------------------------------------------------------------

    \114\ Air taxis fly scheduled service carrying passengers and/or
freight, but they usually are smaller aircraft and operate on a more
limited basis compared to the commercial aircraft operated by
airlines.
    \115\ Title 14--Code of Federal Regulations--Part 241 Uniform
System of Accounts and Reports for Large Certificated Air Carriers.
T-100 Segment (All Carriers)--Published Online by Bureau of
Transportation Statistics. https://www.transtats.bts.gov/Fields.asp?Table_ID=293. Accessed May 9, 2018.
    \116\ Federal Aviation Administration. Terminal Area Forecast
(TAF). https://aspm.faa.gov/main/taf.asp. Accessed April 21, 2018.
    \117\ Federal Aviation Administration. ATADS: Airport
Operations: Standard Report. https://aspm.faa.gov/opsnet/sys/Airport.asp. Accessed May 23, 2018.
    \118\ Federal Aviation Administration. 2009. Airport Master
Record Form 5010. Published by GCR & Associates. https://www.gcr1.com/5010WEB/. Accessed May 21, 2009.
    \119\ The rationale for the use of multiple FAA activity
databases is described in the 2017 NEI report (2017 National
Emissions Inventory: Aviation Component, Eastern Research Group,
Inc., July 25, 2019, EPA Contract No. EP-C-17-011, Work Order No. 2-
19. See section 3.2 for airports and aircraft related emissions in
the Technical Supporting Document for the 2017 National Emissions
Inventory, January 2021 Updated Release; https://www.epa.gov/sites/production/files/2021-02/documents/nei2017_tsd_full_jan2021.pdf,
last accessed June 26, 2021.)
    \120\ AEDT is a software system that models aircraft performance
in space and time to estimate fuel consumption, emissions, noise,
and air quality consequences. It is available at https://aedt.faa.gov/ (last accessed on June 26, 2021).
    \121\ Ibid.
---------------------------------------------------------------------------

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

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

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

C. Projected Reductions in PM Emissions

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

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

VI. Technological Feasibility and Economic Impacts

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

A. Market Considerations

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

B. Conceptual Framework for Technology

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

technology demonstrated to be safe and airworthy proven to Technical
Readiness Level \125\ (TRL) 8 and available for application over a
sufficient range of newly certificated aircraft.\126\ This means that
the analysis that informed the international standard considered the
emissions performance of aircraft engines assumed to be in-production
on the implementation date for the PM mass and number standards,
January 1, 2023.\127\ The analysis included the current in-production
fleet and engines scheduled for entry into the fleet by this date.
(ICAO/CAEP's analysis was completed in 2018 and considered at the
February 2019 ICAO/CAEP meeting.)
---------------------------------------------------------------------------

    \125\ TRL is a measure of Technology Readiness Level. CAEP has
defined TRL8 as the ``actual system completed and `flight qualified'
through test and demonstration.'' TRL is a scale from 1 to 9, TRL1
is the conceptual principle, and TRL9 is the ``actual system `flight
proven' on operational flight.'' The TRL scale was originally
developed by NASA. ICF International, CO2 Analysis of CO2-Reducing
Technologies for Aircraft, Final Report, EPA Contract Number EP-C-
12-011, see page 40, March 17, 2015.
    \126\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15
February 2019, Committee on Aviation Environmental Protection,
Document 10126, CAEP11. It is found on page 26 of the English
Edition of the ICAO Products & Services 2021 Catalog and is
copyright protected: Order No. 10126. For purchase and available at:
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last
accessed November 15, 2021). The statement on technological
feasibility is located in Appendix C of Agenda Item 3 of this report
(see page 3C-4, paragraph 2.2).
    \127\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15
February 2019, Committee on Aviation Environmental Protection,
Document 10126, CAEP11. It is found on page 26 of the English
Edition of the ICAO Products & Services 2021 Catalog and is
copyright protected: Order No. 10126. For purchase and available at:
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last
accessed November 15, 2021). The summary of technological
feasibility and cost information is located in Appendix C to the
report on Agenda Item 3 (starting on page 3C-1).
---------------------------------------------------------------------------

C. Technological Feasibility

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

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

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

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

D. Costs Associated With the Proposed Rule

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

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

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

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

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

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

E. Summary of Benefits and Costs

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

VII. Technical Amendments

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

A. Migration of Regulatory Text to New Part

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

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

B. Deletion of Unnecessary Provisions

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

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

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

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

C. Other Technical Amendments and Minor Changes

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

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

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

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

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

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

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

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

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

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

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

VIII. Statutory Authority and Executive Order Reviews

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

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

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

B. Paperwork Reduction Act (PRA)

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

C. Regulatory Flexibility Act (RFA)

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

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

D. Unfunded Mandates Reform Act (UMRA)

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

E. Executive Order 13132: Federalism

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

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

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

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

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

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

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

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

I. National Technology Transfer and Advancement Act (NTTAA)

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

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

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

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

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

List of Subjects

40 CFR Parts 87 and 1031

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

40 CFR Part 1030

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

Michael S. Regan,
Administrator.

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

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

0
1. Revise part 87 to read as follows:

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

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

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

Sec.  87.1  Definitions.

    Definitions apply as described in 40 CFR 1031.205.

Sec.  87.2  Abbreviations.

    Abbreviations apply as described in 40 CFR 1031.200.

Sec.  87.3  General applicability and requirements.

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

Sec.  87.10  Applicability--fuel venting.

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

Sec.  87.11  Standard for fuel venting emissions.

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

Sec.  87.20  Applicability--exhaust emissions.

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

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

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

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

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

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

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

Sec.  87.48  Derivative engines for emissions certification purposes.

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

Sec.  87.50  Exemptions and exceptions.

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

Sec.  87.60  Testing engines.

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

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

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

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

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

Sec.  1030.1  Applicability.

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

PART 1031--CONTROL OF AIR POLLUTION FROM AIRCRAFT ENGINES

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

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

Subpart A--Scope and Applicability

Sec.  1031.1  Applicability.

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

Sec.  1031.5  Engines installed on domestic and foreign aircraft.

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

Sec.  1031.10  State standards and controls.

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

Sec.  1031.15  Exemptions.

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

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

Sec.  1031.20  Exceptions.

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

Subpart B--Emission Standards and Measurement Procedures

Sec.  1031.30  Overview of emission standards and general requirements.

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

Sec.  1031.40  Turboprop engines.

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

SN = 187[middot]rO-0.168

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

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

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

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

SN = 83.6[middot]rO-0.274

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

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

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

SN = 83.6[middot]rO-0.274

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

SN = 83.6[middot]rO-0.274

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

SN = 83.6 [middot] rO-0.274

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Sec.  1031.90  Supersonic engines.

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

    SN = 83.6[middot]rO-0.274

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

HC = 140[middot]0.92rPR

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

CO = 4550[middot]rPR-1.03

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

NOX = 36+2.42[middot]rPR

Sec.  1031.130  Derivative engines for emissions certification
purposes.

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

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

Sec.  1031.140  Test procedures.

    (a) Overview. Measure emissions using the equipment, procedures,
and test fuel specified in Appendices 1 through 8 of ICAO Annex 16
(incorporated by reference, see Sec.  1031.210) as described in this
section (referenced in this section as ``ICAO Appendix #''). For
turboprop engines, use the procedures specified in ICAO Annex 16 for
turbofan engines, consistent with good engineering judgment.