Transport Partnership
U.S. ENVIRONMENTAL PROTECTION AGENCY
Air Carrier Partner 2.O.15 Tool:
Technical Documentation M^^
2015 Data Year - United States Version
SEPA
United Stales
Environmental
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Transport Partnership
U.S. ENVIRONMENTAL PROTECTION AGENCY
Air Carrier Partner 2.O.15 Tool:
Technical Documentation
2015 Data Year - United States Version
Transportation and Climate Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
i:wJ Stales Office ofTransportation and Air Quality
EPA-420-B-16-048
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SmartWay 2.0.15 - United States
Version
Air Carrier Model
Technical Documentation
2-19-16
1.0 Data Sources
Similar to the other SmartWay tools, air carrier partners provide information
concerning fuel usage and aircraft activity including landing and take-off cycles
(LTOs) and hours of operation in order to estimate C02, NOx and PMio
emissions, and to account for performance improvements made to their fleets
overtime.
The approach used to estimate C02 emissions associated with aircraft
operations focuses on total fuel usage, while NOx and PMio emissions are
estimated using detailed information about fleet composition and operations.
Most airlines provide aircraft-specific activity data to the FAA. To reduce the
burden to Partners, the data elements required for this Tool are similar to the
data already being reported to the FAA.
1.1 Available Emission Factors
Currently there are two types of aircraft engines used for non-military operations:
aircraft equipped with turbine engines that use jet fuel, and smaller aircraft
equipped with piston-driven engines that use aviation gasoline. The emission
factors used for the fuel-based emission estimates are presented in Table 1.
Table 1 - Fuel-based Emission Factors (g/kg of fuel)
Fuel
Jet Fuel
Aviation Gas
g CO2 per kg fuel
3,131
3,146
Note: Alternative fuels such as biojet and synthetic fuels are currently being
considered for commercial aviation applications. Only recently have these fuels
received certification for aviation use at concentrations up to 50 percent. These
fuels are being tested in pilot projects and have yet to be fully commercialized,
which is expected to take several years as infrastructure issues related to the
distribution and storage of these fuels are addressed. As results concerning the
performance and associated emissions of these alternative fuels are released,
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these data will be evaluated for possible inclusion in future versions of the
SmartWay Air Tool.
The preferred approach for estimating NOx and PMio is based on hours of
operation and LTO activity data. Therefore fuel-based emission factors are not
used for these pollutants. NOx and PMio emissions are based on aircraft-
specific data obtained from the FAA's Emission Dispersion Modeling System
(EDMS). The fuel usage and emission factor data in EDMS are obtained from the
International Civil Aviation Organization (ICAO) Aircraft Engine Databank and
adjusted to account for the airframe to which the engine is applied. The NOx and
PMio emission factors have been updated using the most recent EDMS model,
version 5.1.4.1. All current aircraft and engines included in version 5.1.4.1 have
been added to the Air Tool.
The ICAO testing cycle focused on airport-related emissions. As such, only data
on approach, landing, taxi-in, idle, taxi-out, takeoff, and climbout modes were
collected. Emission factors for cruising are not provided in the ICAO test data,
nor are they calculated in EDMS. For the SmartWay Air Tool, cruising emissions
are calculated based on the assumption that the aircraft engines operate at a
percent of take-off engine loads (i.e., maximum thrust), as specified by the user
(see Engine Load % on the Aircraft Inventory worksheet of the Tool).
1.2 Aircraft Activity Data
Two types of activity data are required for the SmartWay Air Tool: data used to
estimate emissions (e.g., fuel usage, hours of operation, and LTOs) and data
needed to develop performance metrics (e.g., miles traveled, ton-miles, cargo
payload and volume, utilization rates). Much (though not all) of the data needed
for this Tool are publically reported, as summarized in Table 2. Some non-
reported data, such as ton-miles and cargo volume utilization, will also need to
be provided.
Table 2. Activity Data Sources
Activity Measure
Fuel Consumption
LTOs
Distance Between Airports
Passengers Transported
Mail Transported
Freight Transported
Reporting Form
P-12A6
F-2d
T-100andT-100(f)a
T-100andT-100(f)a
T-100andT-100(f)a
T-100andT-100(f)a
T-100andT-100(f)a
TranStats Database
Schedule P-12A
Available on request
T-1 00 Segment (All
Carriers)
T-1 00 Segment (All
Carriers)
T-1 00 Segment (All
Carriers)
T-1 00 Segment (All
Carriers)
T-1 00 Segment (All
Carriers)
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Activity Measure
Operating Revenue
Reporting Form
P-1.2b
P-1.1C
F-1d
TranStats Database
Schedule P-12
Schedule P-11
Available on request
3 Forms are submitted monthly by foreign, large certificated, commuter and small certificated carriers (14
CFR Parts 217, 241, 298). Foreign T-100(f) data are held confidential for six months. Small carrier data are
held confidential for two and a half months.
b Forms are submitted quarterly by large certificated carriers with annual operating revenues of $20 million
or more. Foreign carriers are not required to report financials. Large carrier financials data (P-1.2 and P-1.1)
are held confidential for two and a half months.
c Forms submitted semiannually by large certificated carriers with annual operating revenues of less than
$20 million.
d Forms submitted quarterly by commuter and small certificated carriers. Small carrier financials and fuel
consumption data (F-1 and F-2) are held confidential for 3 years. Small certificated and commuter carriers
are defined by the size of planes in their fleet and the number of trips per week.
e Forms submitted monthly by large certificated carriers with annual operating revenues of $20 million or
more. Foreign carriers are not required to report fuel usage.
For NOx and PMio, emissions at and near airports are estimated for individual
aircraft by applying annual, aircraft-specific LTOs to the LTO emission factors in
the EDMS model. Because aircraft trip lengths can vary significantly, total hours
of operation are required to estimate the time spent in cruising mode. The total
time associated with annual LTO activities are subtracted from the reported total
annual hours to avoid double counting.
1.3 Aircraft Characterization Data
As noted above, C02 emissions are simply based on the amount of fuel used by
the partner annually. For NOx and PMio, the two key data elements required to
estimate emissions are the aircraft make and model and the associated engine
make and model. As any given aircraft model can be equipped with a wide
range of engines that have different fuel consumption and emission rates, it is
important that partners provide as much detailed information as possible about
the engines used in their fleet. In the newest version on EDMS (5.1.4.1), there
are a total of 3,055 aircraft and engine combinations. The list of the possible
aircraft and engine combinations are available in the AirTool-Aircraft-Engine-
Data.xlsxfile.
In a future version of the Air Tool, if partners do not know the engine for their
aircraft, the Tool will identify default engines for each aircraft. For an engine to
be designated as a default for a particular aircraft make and model, a valid
aircraft engine combination should first be identified in the EDMS dataset. In
some cases there is only engine listed per aircraft make/model in EDMS. For
those aircraft, the one available engine is simply designated as the default
engine. For other aircraft, Ascends* activity data are used to determine which
engines are the most common for each aircraft. If an engine listed in Ascends is
not in EDMS, the next most common engine is used instead. If there is no match
with the Ascends data, internet search results provide the basis for determining
the default engine.
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Default engines are designated by a "1" in the Default column in the AirTool-
Aircraft-Engine-Data.xlsx file.
In addition, to accurately represent a partner's performance metrics the Air Tool
estimates aircraft capacity in units of mass and volume for 2,340 individual
aircraft-engine combinations. In October 2014, using Jane's Transportation
Reference Guide, Aviation Week's Aerospace & Defense Sourcebook, and other
online resources, capacities for the individual aircraft were reviewed and over
125 corrections were made. Current capacities were quality checked by
comparing the ratio of capacity and aircraft length, for similar sized
aircraft. Capacity corrections were made calculated ratios were outside an
acceptable range.
When weight capacity was clearly defined, values were chosen that reflected
total passenger and luggage weight (military aircraft totals included
munitions). Note that there are often inconsistencies in how capacities are
defined, however, leading to uncertainty in these assignments. For this reason
partners are encouraged to input their own estimates for weight and volume
capacity if available.
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2.0 Emission Estimation
Within the SmartWay Air Tool a fuel-based approach is used for the calculation
of C02 while an operations-based approach is used for calculating NOx and
PMio.
2.1 Emission Calculations Based on Fuel Consumption Data
C02 emissions are estimated using the following equation:
EM = FUa x FC x EFa
Where:
EM = Emission estimate for C02 (grams per year)
FUa = Reported fuel use (gallons/year or tons/year) for fuel type a
FC = Fuel conversion factor for gallons to kgs (Jet Fuel = 3.07
kilogram/gallon; aviation gasoline 2.73 kilogram/gallon); tons
of fuel to kilograms (1 ton = 907.18 kilograms)
EFa = Emission factor for fuel type a (grams/kilogram of fuel) -
Table 1
a = Fuel type (e.g., jet fuel or aviation gasoline)
2.2 Emission Calculations Based on Aircraft-specific Data
The operations-based approach allows for NOx and PMio emissions to account
for individual aircraft in the partner's fleet. The emissions calculation is
developed using two types of aircraft operations: 1) airport-related activities (i.e.,
approach, landing, taxi-in, idle, taxi-out, take-off, and climbout), which are
quantified in terms of LTO cycles, and 2) cruising operations between airports,
measured in hours.
2.2.1 Airport-related Activities
LTO data can be applied to aircraft-specific fuel-consumption and emission
factors, which were developed from data extracted from the FAA's EDMS
database. Within the Air Tool, aircraft engine emissions data are applied to time-
in-mode data for each segment of the LTO cycle, providing aircraft-specific LTO-
based emission factors. The time-in-mode values from EDMS vary by aircraft
make and model, and actual time-in-mode values for taxi-in, idle, and taxi-out
times can vary significantly between airports. Airport-related delays which affect
taxi and idle times are not considered in the Air Tool emissions calculations.
Instead, default EPA time-in-mode values are used to generate the LTO
emission factors used in the Tool.
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The default EPA time-in-mode values are included in the EPA's NEI
documentation
(http://www.epa.gov/ttnchie1/net/2008 nei/aircraft report final.pdf), page 2-
14. Note that the NEI builds upon the FAA's EDMS model, and EDMS has two
types of default values for takeoff/climbout/approach/landing - the first set
matches the time periods used in the ICAO engine testing, while the second set
accounts for airport-specific mixing height for climb out and approach. Because
the Air Tool is set up to accept data for operations at any airport, the default
ICAO times were used. Neither EDMS or ICAO data include default taxi times as
these can vary significantly between airports, so the default values noted in the
NEI documentation were used (taxi-in time 7 minutes and taxi-out time 19
minutes).
EDMS uses fuel based indexes to estimate emissions, which means the time in
mode values are linked to fuel usage rates, which in turn vary based on aircraft
model/engine combinations. These fuel usage rates are built into the EDMS
model, which then calculates the emissions based on fuel usage. For the Air
Tool, EDMS was run for each aircraft make model engine combination using the
default times for 10,000 LTOs. The output was then divided by 10,000 to obtain
a per LTO emission factor for each make/model/engine combination.
User-provided aircraft-specific LTO activity data (under Total Annual LTOs on the
Aircraft Operations screen) is applied to the LTO emission factors using the
following equation:
EAxP=LTOxx EFixp
Where:
EAxp = Airport-related aircraft emissions for specific aircraft model and
engine combination (x) and pollutant (p) (grams per year)
LTOx = Annual LTO activity for specific aircraft (x) (LTOs/year)
EFixp = LTO emission factor for specific aircraft (x) and pollutant (p)
(grams/LTO)
X = Specific aircraft make/model/engine combination
P = Pollutant (NOx or PMio)
Additional information on the emission factors used for the LTO emission
calculations can be found in the AirTool-Aircraft-Engine-Data.xIsx file.
2.2.2 Cruising Operations
Reported aircraft hours of operation include time spent in airport-related activities
as well cruising. For this reason it is necessary to adjust the total hours value to
estimate the time spent in the cruising mode. As noted, the period of time an
aircraft spends in an LTO cycle varies by aircraft make and model, and time-in-
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mode values are included in the EDMS model for all modes except idling. The
EPA default value used in the latest National Emission Inventory (NEI) for the
idling time-in-mode is used in the Air Tool.
The time spent in the cruising mode is estimated using the following equation:
TOx = THx - (LTOx x LMx / 60)
Where:
TOx = Total cruising hours of operation for specific aircraft x (hours/year)
THx = Total hours of operation for specific aircraft (x)
LTOx = Annual LTOs for specific aircraft (x)
LMx = Total time spent per LTO cycle, minutes (from EDMS, EPA)
60 = Conversion - minutes per hour
x = Aircraft make and model
To estimate cruising emissions, the cruising hours of operation are applied to the
cruising emission factors. These emission factors assume that aircraft in cruising
mode operate at the fraction of power specified in the Engine Load % field.
Cruising emissions are estimated using the following equation:
ECxp = TOx x (EFcXpX 3,600) x LFx/70
Where:
ECxp = Cruising aircraft emissions for specific aircraft model (x) and
pollutant (p) (grams per year)
TOx = Total cruising hours of operation for specific aircraft x
(hours/year)
EFcxp = Cruising emission factor for specific aircraft (x) and pollutant (p)
(grams / second)
3,600 = Conversion seconds per hour
LFx = Load factor specified for each aircraft make/model (x), in
percent
70 = Default engine load factor percent for cruising operations from
EDMS
x = Specific aircraft make and model
p = Pollutant
Additional information on the emission factors used for the cruising mode can be
found in the AirTool-Aircraft-Engine-Data.xIsx file.
Once LTO and cruising emissions are calculated they are summed to determine
total emissions for each aircraft.
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2.3 Aircraft Upload Function
The Air Tool provides an upload function which allows the user to import
hundreds or thousands of records for individual aircraft, including the engine
characteristic and activity data needed to estimate emissions and performance
metrics. The Air Tool aggregates the import file to the aircraft/engine level. To
perform this aggregation the Tool weights the reported engine loads by total fuel
consumption for the given aircraft/engine category. Similarly, individual weight
capacity values (in pounds) are weighted by the relative fraction of ton-miles for
the category, and volume capacity values (in cubic feet) are weighted by miles.
Note that this approach only impacts the reported performance metrics, not the
calculated mass emissions.
The SmartWay Air Tool is provided with an Excel file named "starterfile.xls"
which should be populated with aircraft-specific data for upload. Users can
provide one record for each aircraft make/model/engine make/model
combination. Each record should include data for the following columns:
# aircraft
Fuel Type
Fuel Units
fuel usage
total miles
total ton-
miles
LTOs
operating
hours
weight
capacity
volume
capacity
utilized
volume
The first two rows of the starter file contain example inputs for user reference.
These rows should be over-written with actual data before importing into the Air
Tool. Please be sure to save the updated file using the same name and Excel
file format as the original starter file.
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3.0 Performance Metrics
The SmartWay Air Tool is designed to apply calculated emissions to a variety of
operational metrics. These metrics can be used as reference points to evaluate a
partner's environmental performance relative to others. The equations used to
estimate the different performance metrics are shown below.
3.1 Grams of Pollutant per Mile
PMp =
Where:
PMp = Grams of pollutant per mile (grams/mile)
EMpo = Total annual emissions summed by pollutant (P) for both
operation types (0) (grams per year)
M = Total annual statute miles flown
P = Pollutant
0 = Operation types (airport and cruising)
3.2 Grams of Pollutant per Ton-Mile
PTMp = X EPTO / TM
Where:
PTMp = Grams of pollutant per ton-mile (grams /ton-mile)
EPO = Annual emissions summed over operation type (0) by pollutant
(P) (grams/year)
TM = Total annual ton-miles
P = Pollutant
0 = Operations (airport and cruising)
3.3 Grams of Pollutant per Thousand Cubic Foot-Miles
The Air Tool provides aircraft-specific weight and volume capacity in terms of
pounds and cubic feet, respectively. Volume characterization for a given aircraft
make/model includes both passenger and luggage space, as well as the cargo
hold. Capacities were compiled using variety of sources, including manufacturer
websites and the Aviation Source Book. The resulting volume capacity estimates
were quality checked by comparing the ratio of capacity and aircraft length, for
similar type and size aircraft.
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Total mass emissions are divided by total fleet volume capacity and miles
traveled to obtain emissions per thousand cubic foot-miles, using the following
equation:
PCFp = X EPO / (CF/1,000 x M)
Where:
PCFp = Grams of pollutant per aircraft volume (grams/ thousand cubic
foot-miles)
EPO = Total annual emissions summed over operations (0) by
pollutant (P) (grams/year)
CF = Total fleet capacity volume (cubic feet)
M = Total annual (statute) miles
P = Pollutant
0 = Operations (airport and cruising)
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References
Ascends, Aircraft and Airline Data, 2012.
Aviation Week & Space Technology 2009 Source Book.
Endres, Gunter, and Gething, Michael. Jane's Aircraft Recognition Guide - Fifth
Edition. London: HarperCollins, 2007.
International Civil Aviation Organization, Aircraft Engine Emissions Databank,
2009.
U.S Department of Transportation, Federal Aviation Administration, Emission
Dispersion and Modeling System Version 5.1.4.1, August 2013.
U.S. Department of Transportation, Federal Aviation Administration, F-1 and F-2
Forms
U.S. Department of Transportation, Federal Aviation Administration, P-1 Forms
U.S. Department of Transportation, Federal Aviation Administration, T-100 Forms
U.S. Environmental Protection Agency, National Emission Inventory, 2009.
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