AIRCRAFT EMISSIONS:
IMPACT ON AIR QUALITY
AND FEASIBILITY OF CONTROL
SSEZ
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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PREFACE
This report presents the available information on the
present and predicted nature and extent of air pollution
related to aircraft operations in the United States. In
addition, it presents an investigation of the present and
future technological feasibility of controlling such
emissions. This report is published in accordance with
Section 231 (a) of the Clean Air Act as amended, which
states:
" (1) Within 90 days after the date of enactment of
the Clean Air Amendments of 1970, the Administrator shall
commence a study and investigation of emissions of air
pollutants from aircraft in order to determine-
"A. the extent to which such emissions affect
air quality in air quality control regions throughout the
United States, and
NB. the technological feasibility of controlling
such emissions
n (2) within 180 days after commencing such study
and investimation, the Administrator shall publish a report
of such study and investigation . . ."
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TABLE OF CONTENTS
Page
LIST OF FIGURES v
LIST OF TABLES vii
INTRODUCTION 1
CONCLUSIONS ' 5
METHODOLOGY FOR ASSESSMENT OF AIR QUALITY IMPACT 7
NATIONAL AMBIENT AIR QUALITY STANDARDS 7
BASIC REQUIREMENTS FOR IMPACT EVALUATION 10
EMISSION FACTORS 10
SELECTION OF CRITICAL AREAS AND AIRPORTS 12
EMISSION PROJECTIONS 13
RESULTS OF IMPACT EVALUATION 19
REGIONAL IMPACT OF AIRCRAFT EMISSIONS 19
SUBREGIONAL AND LOCALIZED IMPACT 29
GENERAL INDICATIONS OF LOCALIZED AIR QUALITY IMPACT 29
PASSENGER USAGE DENSITY AND AIR POLLUTION POTENTIAL 29
EMISSION DENSITY COMPARISON 30
DETAILED INVESTIGATION OF LOCALIZED POLLUTANT CONCENTRATION..33
8-HOUR CARBON MONOXIDE CONCENTRATIONS 33
1-HOUR CARBON MONOXIDE CONCENTRATIONS AT LOS ANGELES AIRPORT
39
CARBON MONOXIDE CONCENTRATIONS AT OTHER AIRPORTS 39
HYDROCARBONS AND POTENTIAL OXIDANT CONCENTRATIONS A3
OXIDES 'OF NITROGEN 47
SMOKE AND PARTICULATES 49
TECHNOLOGICAL FEASIBILITY OF CONTROLLING AIRCRAFT EMISSIONS 53
111
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Page
EMISSION CONTROL BY ENGINE MODIFICATION .......................... 54
ENGINE CLASSIFICATION ....................................... 54
EMISSION CONTROL METHODS AND EFFECTIVENESS .................. 55
TURBINE ENGINES ........................................ 56
PISTON ENGINES .......................................... 62
COST AND TIME REQUIREMENTS FOR CONTROL METHOD
DEVELOPMENT AND IMPLEMENTATION .............................. 55
EXISTING ENGINES ....................................... 66
FUTURE ENGINES .......................................... 70
EMISSION CONTROL BY MODIFICATION OF GROUND OPERATIONS ............ 71
DEFINITION OF GROUND OPERATIONS ............................. 71
EMISSION CONTROL METHODS .................................... 71
IMPLEMENTATION COST AND TIME REQUIREMENTS ................... 72
COMPARATIVE EVALUATION OF EMISSION CONTROL METHODS ................ 76
EMISSION MEASUREMENT TECHNOLOGY ........................... 79
SAMPLING AND TEST PROCEDURES ................................ 80
EMISSION MEASUREMENT INSTRUMENTATION ........................ 81
APPENDIX A [[[ 83
APPENDIX B [[[ 91
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LIST OF FIGURES
Page
1. AIR SAMPLING LOCATIONS AT LOS ANGELES INTERNATIONAL AIRPORT 34
2. EXPECTED CO CONCENTRATIONS, 8-HOUR AVERAGING TIME, WINTER
1970, STATION 209, LAX 35
3. VICINITY OF LOS ANGELES INTERNATIONAL: PERCENT OF CONTRIBUTION
BY AIRCRAFT TO CARBON MONOXIDE LEVELS 37
4. FREQUENCY DISTRIBUTIONS FOR CARBON MONOXIDE FOR VARIOUS
AIRCRAFT EMISSION CONTRIBUTIONS AT STATION 209, WINTER 1980 38
5. HYDROCARBON ISOPLETHS IN THE VICINITY OF LOS ANGELES INTER-
NATIONAL : AIRCRAFT SOURCES (3-Hr. Average for 1970) 44
6. HYDROCARBON ISOPLETHS IN THE VICINITY OF LOS ANGELES INTER-
NATIONAL: AIRCRAFT SOURCES (3-Hr. Average for 1980) 45
7. CALCULATED NON-METHANE HYDROCARBON CONCENTRATIONS DOWNWIND
OF LOS ANGELES AIRPORT FOR 1980 WITH NON-AIRCRAFT SOURCES
CONTROLLED 46
8. NOX ISOPLETHS IN THE VICINITY OF LOS ANGELES INTERNATIONAL:
AIRCRAFT SOURCES (Annual Average for 1970) 48
9. NOX ISOPLETHS IN THE VICINITY OF LOS ANGELES INTERNATIONAL:
AIRCRAFT SOURCES (Annual Average for 1980) 50
10. NOX ISOPLETHS IN THE VICINITY OF CHICAGO-0'HARE INTER-
NATIONAL : AIRCRAFT SOURCES (Annual Average for 1980) 51
11. PISTON ENGINE EMISSION CHARACTERISTICS 64
12. HYDROCARBON AND CARBON MONOXIDE EMISSIONS FROM A TYPICAL
AIRCRAFT TURBINE ENGINE (JT3D) 73
A-l. MAXIMUM 8-HOUR AVERAGE CO CONCENTRATIONS IN LOS ANGELES AREA 85
A-2. BASELINE DATA, DAILY MAXIMUM 8-HOUR AVERAGE CO CONCENTRATIONS
STATION 209, LAX, 1970 ' 86
A-3. FREQUENCY DISTRIBUTION FOR 8-HOUR CO DATA, STATION 209, LAX,
SEPTEMBER 1970 87
A-4. EXPECTED CO CONCENTRATION DISTRIBUTION, WINTER, STATION 209,
LAX FOR 80 PERCENT AIRCRAFT CONTRIBUTION 88
A-5. EXPECTED CO DISTRIBUTION, WINTER, STATION 209, LAX FOR 20
PERCENT AIRCRAFT CONTRIBUTION 89
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LIST OF TABLES
Page
TABLE
1. NATIONAL AMBIENT AIR QUALITY STANDARDS 9
2. AIRCRAFT CLASSIFICATION SYSTEM ; : > • 11
3. PRESENT AND PROJECTED LTD CYCLES FOR 1970, 1975, and 1980 14
4. CURRENT AND PROJECTED EMISSIONS FOR AIRCRAFT AND AIRPORTS 16
5. ABILITY OR NON-ABILITY TO MEET THE NATIONAL AMBIENT AIR QUALITY
STANDARDS IN 1975 20
6. METROPOLITAN LOS ANGELES INTRASTATE AQCR EMISSIONS 21
7. NEW YORK PORTION OF THE N.J. - N.Y. - CONN. INTERSTATE AQCR
EMISSIONS ••••' 22
8. NATIONAL CAPITAL INTERSTATE AQCR EMISSIONS • • • 23
9. ILLINOIS PORTION OF THE METROPOLITAN CHICAGO INTERSTATE AQCR
EMISSIONS 24
10. METROPOLITAN DENVER INTRASTATE AQCR EMISSIONS 1 25
11. SAN FRANCISCO BAY AREA INTRASTATE AQCR EMISSIONS 26
12. METROPOLITAN DALLAS - FORT WORTH INTRASTATE AOCR EMISSIONS 27
13. METROPOLITAN BOSTON INTRASTATE AQCR EMISSIONS 28
14. INDICATIONS OF LOCALIZED AIRPORT IMPACT OF 20 LARGEST AIR
CARRIER AIRPORTS • 31
15. COMPARISON OF EMISSION DENSITIES FOR AIRPORTS VERSUS URBAN
AREAS FOR 1970, 1975, and 1980 32
16. EXPECTED RANGE OF DAYS THAT 8-HR STANDARD WILL BE EXCEEDED
IN VICINITY OF LAX FOR VARIOUS LEVELS OF AIRCRAFT IMPACT 40
17. LOS ANGELES AIRPORT - NUMBER OF TIMES THE 1-HOUR CO STANDARD
WAS EXCEEDED - MAY 10 THROUGH NOVEMBER 9, 1970 41
18. DISPERSION MODEL ESTIMATES OF 1-HOUR CO CONCENTRATIONS . ; 42
^ i
19. AIRCRAFT ENGINE CLASSIFICATION 55
20. ENGINE MODIFICATIONS FOR EMISSION CONTROL FOR EXISTING AND
FUTURE TURBINE ENGINES 57
VI1
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Page
21. EFFECTIVENESS OF tl - MINOR COMBUSITON CHAMBER REDESIGN -
ON REDUCTION OF EMISSIONS FROM TURBINE ENGINES 59
22. EFFECTIVENESS OF ENGINE MODIFICATION IN CONTROL OF EMISSIONS
FROM TURBINE ENGINES, BY OPERATING MODE 60
23. BASES FOR CONTROL METHOD EFFECTIVENESS ESTIMATES FOP TURBINE
ENGINES 61
24. ENGINE MODIFICATIONS FOR EMISSION CONTROL FOR EXISTING AND
FUTURE PISTON ENGINES 53
25. CURRENT UNCONTROLLED EMISSION RATES FOR PISTON ENGINES 65
26. EFFECTIVENESS OF ENGINE MODIFICATIONS IN CONTROL OF
EMISSIONS FROM PISTON ENGINES BY POLLUTANT 65
27. TIME AND COSTS FOR MODIFICATION OF CURRENT CIVIL AVIATION
ENGINES 68
28. COST RESULTS FOR TURBINE ENGINE POPULATION BY SEPARATE USE
CATEGORIES 69
29. COMPARATIVE REDUCTIONS RESULTING FROM CONTROL METHODS APPLIED
AT LOS ANGELES INTERNATIONAL AIRPORT 74
30. COSTS AND TIME FOR OPERATIONS CHANGES AT LOS ANGELES INTER-
NATIONAL AIRPORT 75
31. COMPARISON OF EMISSION CONTROL METHODS 77
32. INSTRUMENTATION FOR MEASUREMENT OF TURBINE ENGINE EMISSIONS 82
B-l. SHORT-TERM METEOROLOGICAL AND ACTIVITY CONDITIONS 94
Vlll
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INTRODUCTION
Public awareness that aircraft were a source of air
Pollution developed in the late 1950* s with the introduction
of turbine-engine aircraft. Visible exhaust plumes from the
engines and increased levels of exhaust odors a?air ports
£??lei J°^aints *° b« lodged. The complaints, in £S*
stimulated investigations into the nature and extent of
aircraft emissions. The Air Quality Act of 1967
specifically identified aircraft emissions as a subject of
£n?^n ™d re?uired ™ investigation by the DepIrtmlS of
Health, Education, and Welfare. The study*, submitted to
Congress on January 17, 1969, concluded that:
"1. Reduction of particulate emissions from -jet
aircraft is both desirable and feasible. Engine
Sn?«JS*UrerS fnd airlines have indicated that improvements
in turbine engine combustor design can be built into new
engines and retrofitted on engines already in use? Teltina
aJS alread? underw*y- Furthermore, thly have 9
that application of this technology will be
y ^ early 197°'s- While there «e io laws or
L£r?Sei thS *ndustr* to follow through on this
ppears that public pressures resulting primarily
fT8! eff€cts of odors and visibilit? obscuration
industrv to Initiate the application of this
technology as soon as possible and to complete it within the
SS^SLSSS1; time' ^rclingly, it L the'LSntion o!
tuis Department to encourage such action by enoine
manufacturers and airline operators and to keep close watch
on their progress, if, at any time, it appears that
K°^S? 1S ^•TOte or that completion of the work will
?L^ ?iy Prolon9ed' or that the concern of the industry
lags, the Department will recommend regulatory action to the
Congress that statutory authority for such actioTbe
provided .
r,^-. research is needed to define more
precisely the present and probable future "**ur«» and
SS^i^f/ii*?^ a±r P°11Uti°n P^ble^s associated
niS« J * Jivaty ln the United States and to identify
needs for control measures. Emphasis must be placed
particularly on assessment of air pollutant levels in the
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air terminal environment and their effects on health and
satety and on evaluation of possible long-term effects of
upper atmospheric pollution resulting from aircraft flight
activity. The Department will undertake research
appropriate to the solution of this problem.
* *"3' As further research results in identification of
needs for additional measures to control air pollution from
any type of aircraft, and as measures to achieve such
control become available through research and development.
it is the Department's expectation that engine
manufacturers, airline operators, and other segments of the
aviation community will take the initiative in the
development and application of such control measures. If
the private sector fails to provide adequate controls, the
Department will not hesitate to recommend to the Congress
that Federal regulatory action be authorized.
"4. In light of the relatively small contribution of
aircraft to community air pollution in all places for which
adequate data are available, and in view of the practical
£??«"? *5S* would result from State and local regulatory
action in this field, it is the Department's conclusion that
adoption and enforcement of State or local emission control
regulations pertaining to aircraft cannot be adequately
^iT^f at this time' The Department recommends that, if
and when regulations become necessary, the rationale used to
develop Federal rather than local emission standards for
motor vehicles be applied to aircraft.
"5. The Department recognizes that State and local
agencies, in cooperation with the Federal Aviation
Administration and other cognizant agencies, are the most
appropriate groups to insure that control of airport
pollution hazards will be given adequate consideration in
™^Seie°^°n of *irp°rt sites, planning for expansion and
fnd £nn£»T°2 °f airP°rts' desi^ of airports, and planning
and conduct of ground operations.
"6. The Department will include information on
progress in the control of air pollution from aircraft in
the annual report which must be submitted under section 306
of the Air Quality Act."
As a result of conclusion (1) above, in March 1970, at a
meeting held by the Secretaries of Health, Education, and
Welfare and of Transportation, representatives of 31
airlines agreed to a schedule for retrofitting JT8D engines
with reduced smoke combustors, to be substantially completed
by the end of 1972. This agreement sought to significantly
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abate visible (smoke) emissions from aircraft powered by
•this widely used engine. This retrofit program is 85%
complete (July 1972) , conclusion (2) pointed to the need
for studying air terminal environments, a need which led to
an EPA-sponsored study of Los Angeles International Airport
by the Los Angeles Air Pollution Control District. This
study was completed in April 1971.*
Passage of the 1970 Clean Air Act Amendments essentially
required that we reassess the aircraft emissions problem and
update our knowledge concerning the air quality impact and
feasibility of control of such emissions.
The data base for this report includes information
developed by Northern Research and Engineering3 *, Cornell
Research Laboratories5, the previously cited LAPCD study,
and information compiled separately by EPA personnel.
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CONCLUSIONS
The various approaches taken in this study to assess the
impact of aircraft on air quality indicate, both
individually and collectively, that aircraft operations
"cause or contribute to or are likely to cause or contribute
to air pollution which endangers the public health or
welfare" (Sec. 231(a), Clean Air Act Amendments of 1970).
Based on this general conclusion a realistic program of
emissions control should be instituted. Though such a
control program cannot be quantitatively related to the air
quality considerations discussed herein, pollutant emissions
from aircraft and aircraft engines should be reduced through
the application of the present and prospective technology
described in this study. A control program should have
inherent flexibility so that as more extensive impact data
become available the required controls can be modified
accordingly.
The results of EPA's current study of aircraft emissions
and their control have led to the following specific
conclusions:
1. Aircraft emissions are significant contributors to
the regional burden of pollution in comparison to other
sources which will have to be controlled to meet National
Ambient Air Quality Standards.
2. When airports are viewed as concentrated area sources
of pollution emissions, either in isolation or in concert
with their surrounding pollution sources, it can be
demonstrated that airports will probably exert localized
impact on air quality, in excess of the standards, even
though relief is provided elsewhere in the region by
controls relating to automobiles and stationary sources.
That is, unless aircraft emissions are reduced, airports
will still remain intense area emitters of pollutants when
the emission densities in the surrounding region have been
greatly reduced.
3. Aircraft emissions have impact on air quality in
residential and business areas adjacent to major U. S.
airports. The control of non-aircraft sources in and around
such airports will not be adequate to insure compliance with
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the National Ambient Air Quality Standards indicating the
need for controlling aircraft emissions.
U. There exists a variety of control technigues for
effecting aircraft emissions reductions which appear both
feasible and economically attractive during the next two
decades. Emissions may be reduced by means of the following
general approaches:
(a) Modification of ground operational procedures.
(b) Improvement in maintenance and quality control
procedures to minimize emissions from existing families of
turbine engines.
(c) Development and demonstration of new combustion
technology for major reductions in emissions from second-
generation turbine and piston aircraft engines.
(d) Retrofit of turbine engine fleets with existing
technology for near-term reduction of emissions.
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METHODOLOGY FOR IMPACT ASSESSMENT
Assessment of air quality impact involves investigation
at several different levels: (a) global, (b) regional (sub-
global) , (c) urban, and (d) local. In this report the urban
level is defined as an air guality control region. The
ability to conduct investigations or assessment at these
levels depends entirely on the analytical tools and data
bases available. Until quite recently most assessments were
source oriented and presented data in terms of national or
air quality control region inventories. With the
development of models and more refined monitoring systems,
we can now explore the more localized "hot spots" within an
urban area. The earlier report* on the impact of aircraft
emissions dealt only with national and regional inventories
and projections of aircraft emissions and pointed to the
need for a closer look at local airports and their immediate
environments. Hence, this study concentrates on assessing
local effects through a combination of approaches involving
monitoring, statistical analysis, and modeling.
Additionally, aircraft emissions are compared with those
from other sources of the same pollutants in terms of
relative importance and relative cost of control.
The potential impact of aircraft emissions on the global
and sub-global environments is not being ignored. Studies
of pollution at these levels involve an integrated
assessment of all contributors to the global pollution
inventory, and hence are beyond the scope of this report.
The Clean Air Act mandates that EPA study the geophysical
effects of air pollution. Research and monitoring
components of EPA are now engaged in preliminary phases of
such studies.
To provide continuity, we have updated pertinent data
prepared by Northern Research and Engineering which was
contained in the previous report*. Discrepancies between
similar data presentations in the two reports result from
the better data base obtained in this study.
NATIONAL AMBIENT AIR QUALITY STANDARDS
In order to assess the significance of aircraft
emissions, one must evaluate their contribution to pollutant
concentrations in the atmosphere and relate the resulting
concentrations to the national ambient air quality
standards.
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In accordance with the Clean Air Act Amendments of 1970,
the EPA established primary and secondary ambient air
quality standards* for six major pollutants: carbon
monoxide, nitrogen dioxide, hydrocarbons, photochemical
oxidants, sulfur dioxide, and particulates. The primary
standards provide for protection of public health and the
secondary standards for prevention of all other undesirable
effects of air pollution. Table 1 shows the national
standards for these six pollutants.
It should be noted that nonmethane hydrocarbons at
concentrations observed in the atmosphere have not been
associated with health effects. The relationship between
nonmethane hydrocarbons and photochemical oxidants
indicates, however, that peak photochemical oxidant
concentrations are associated with hydrocarbon
concentrations averaged over the time period from 6 to 9
a.m. * The peak oxidant levels normally appear some three
hours later. The nonmethane hydrocarbon standard is based
on this relationship.
As a basis for implementation of the standards, the
entire United States has been divided into some 2HO Air
Quality Control Regions*. Regional boundaries are based on
considerations of urban-industrial concentration, existing
jurisdictional boundaries, and other factors including
topography and meteorology, which would affect levels of air
quality in an area.
In accordance with the provisions of Section 110 of the
Clean Air Act, the States have submitted plans that provide
for the implementation, maintenance, and enforcement of the
national air quality standards on a regional (air quality
region) basis. The State implementation plan for each
region must provide for attainment of the primary standards
in 3-5 years depending on whether an extension has been
granted. The State plan is required to set forth the
procedure for attaining the secondary standards within a
reasonable amount of time.
Strategies which States are proposing to meet the
standards and the possible impact aircraft emissions and
their control may have on the strategies are discussed in
the section on regional impact.
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Table 1 NATIONAL AMBIENT AIR QUALITY STANDARDS
Pollutant
Standard Description
Carbon monoxide
(Primary and secondary
standards are the same)
10 milligrams per cubic meter (9 ppm), maximum
8-hour concentration not to be exceeded more than
once per year.
40 milligrams per cubic meter (35 ppm), maximum
1-hour concentration not to be exceeded more than
once per year.
Nitrogen dioxide
(Primary and secondary
standards are the same)
100 micrograms per cubic meter (0.05 ppm), annual
arithmetic mean.
Hydrocarbons (non-methane)
(Primary and secondary
standards are the same)
160 micrograms per cubic meter (0.24 ppm), maximum
3-hour concentration (6-9 a.m.) not to be exceeded
more than once per year. For use as a guide in
devising implementation plans to meet the oxidant
standards.
Particulate matter
Primary standard
Secondary standard
75 micrograms per cubic meter, annual geometric
mean.
260 micrograms per cubic meter, maximum 24-hour
concentration not to be exceeded more than once per
year.
60 micrograms per cubic meter, annual geometric
mean, as a guide to be used in assessing implementa-
tion plans to achieve the 24-hour standard.
150 micrograms per cubic meter, maximum 24-hour
concentration not to be exceeded more than once per
year.
Sulfur dioxide
Primary standard
Secondary standard
80 micrograms per cubic meter, annual arithmetic
mean.
365 micrograms per cubic meter, maximum 24-hour
concentration not to be exceeded more than once per
year.
60 micrograms per cubic meter, annual arithmetic
mean.
260 micrograms per cubic meter, maximum 24-hour
concentration not to be exceeded more than once per
year.
1300 micrograms per cubic meter, maximum 3-hour con-
centration not to be exceeded more than once per
year.
Oxidant
(Primary and secondary
standards are the same)
160 micrograms per cubic meter, maximum 1-hour con-
centration, not to be exceeded more than once per
year
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BASIC REQUIREMENT FOR IMPACT EVALUATION
EMISSION FACTORS
Pollutants emitted by aircraft engines include gaseous
hydrocarbons, carbon monoxide, oxides of nitrogen,
particulate matter, and sulfur oxides. In order to evaluate
the impact of aircraft emissions on the ambient air levels
of these pollutants, the logical first step is an estimate
of the total emissions due to aircraft. Because emission
rates vary according to engine type, number of engines and
operating mode, we have classified aircraft by type, defined
the typical operating modes for each class throughout their
landing and takeoff (LTO) cycles, and determined emission
factors for each class operating in each mode.
The aircraft classification system groups aircraft into 12
separate types that include the currently used commercial
air carriers, and general aviation, and military aircraft.
(Classes 8-11 are exclusively military aircraft and are
excluded from further consideration in this report.)
Provision was also made in the classification system for the
possible introduction of supersonic commercial aircraft in
the future. The basis for classification of civilian and
commercial aircraft is presented in Table 2.
The aircraft modes of operation for which emission rates
were categorized are:
(1) Start-up and idle
(2) Taxi
(3) Idle at runway
(U) Takeoff
(5) Climb-out to 3,000 foot elevation
(6) Fuel dumping
(7) Approach from 3,000 foot elevation
(8) Landing
(9) Idle and shutdown
(10) Maintenance
Emission factors were developed for the civil aviation
aircraft classes. A representative listing of emission
factors for piston and turbine engines is presented in
subsequent discussions of control feasibility.
The aircraft emission data, obtained through various
research programs funded by EPA, are summarized in the
report prepared for EPA by Cornell University.'
Emissions from non-aircraft sources on and around the
airport are also accounted for in the air quality analyses.
These sources of emissions include airport heating plants.
10
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TABLE 2
AIRCRAFT CLASSIFICATION SYSTEM
Ref. 14
class-
Category Class fication
Air
Carrier 1
2
3 1
4 2
5 4
General
Aviation 6 3
7 6
V/Stol 12 7
Type
Supersonic
transport
Jumbo jet
transport
Long-range
jet transport
Medium range
jet transport
Turboprop
transport
Business jet
Piston-engine
utility
Helicopters
and V/STOL
Examples
Concorde
Tupolev TU-144
Boeing 747
Douglas DC-10
Boeing 707
Douglas DC-8
Boeing 727
Douglas DC-9
Lockheed Electra
Fairchild Hiller
FH-227
Lockheed Jetstar
North American
Sabreliner
Cessna 210
Centurion
Piper 32-300
Cherokee Six
Silorsky S-6L
Vertol 107
Engine Model
R-R/Snecraa
Olympus 593
P&WA JT9D
P&WA JT3D
P&WA JT8D
Allison
501-D13
P&WA JT12
Continental
10-520-A
General
Electric CT58
Type
Turbojet
Turbofan
Turbofan
Turbofan
Turbo-
prop
Turbojet
Opposed
piston
Turbo-
shaft
Engines
Thrust per
or powera aircraft
39,000 Ib. 4
43,000 Ib. 4
18,000 Ib. 4
13,900 Ib. 2.6
3,750 hp. 2.5
2,900 Ib. 2.1
292 hp. lb
1,390 hp. 2
Equivalent shaft power.
b,
Representative of Van Nuys and Tamiami.
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fuel storage losses, automobiles, service vehicles, and
areas neighboring the airport. To estimate the impact of
aircraft emissions on air quality near the ground, one must
take into account emissions from the time an aircraft enters
the atmospheric mixing layer during approach until it leaves
this layer during climb-out. In defining an LTO cycle
representative of this consideration, a height of 3,000 feet
above the runway was selected as a reasonable approximation
of atmospheric mixing depth over major U. S. metropolitan
areas.1 The number of LTO cycles performed, and the relative
lengths of time spent in each operational mode of an LTO
cycle, combined with the appropriate emission factors,
determine the quantities of pollutants emitted ty aircraft.
SELECTION OF CRITICAL AREAS AND AIRPORTS
Once the general emission characteristics of aircraft were
determined, specific regions and airports having high
aircraft activity and air pollution potential were selected
for impact evaluation.
As a part of the Northern study3, several airports were
selected to represent, as nearly as possible, those at which
the impact of emissions from aircraft and related activities
would probably be greatest. The factors considered in
evaluating the potential impact of individual airports
included: (1) aircraft activity levels, (2) airport area,
(3) mean wind speed, and (U) relative activity of different
types of aircraft (commercial air carrier and general
aviation). On the basis of these considerations and the
availability of airport and aircraft activity data, these
airports were selected for study:
(1) Commercial Air Carrier
Los Angeles International
Washington National
J. F, Kennedy International
O'Hare International
(2) General Aviation
Van Nuys, California
Tamiami, Florida
12
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Less elaborate evaluations of four additional airports and
their impact in their respective air quality control regions
were developed as the regional impact analysis was expanded
to include an examination of State implementation plans for
the attainment of the air quality standards.
The four additional airports, located in San Francisco,
Dallas-Ft. Worth, Denver, and Boston, were selected on the
basis of high levels of aircraft activity and severity of
the regional pollutant levels.
EMISSION PROJECTIONS
The basic emission factors for any particular engine type
are not expected to change substantially with time unless
changes are required by emission standards. In addition,
the number and type of engines representative of one
particular class of aircraft are not expected to change
substantially in the next 10-20 years. The important and
determining factors affecting the projected controlled or
uncontrolled emissions are: (1) changes in the level of
airport activity, and (2) changes in the mix of the various
classes of aircraft.
As a part of the Northern Research Study, records of
aircraft activity by class were obtained for the selected
airports. Prospective growth in activity at each airport
was estimated by projecting past and current activity data
to 1975 and 1980. The general trend at the selected
airports is towards more aircraft operations in classes 1,
2, 4, 6 and 7; and less in classes 3 and 5. The total
yearly activity data and projections are summarized in Table
3.
The air carrier airports are so-called because of the
preponderance of commercial air carrier activity, which, in
1970, ranged from 66 percent of total activity at Washington
National to 92 percent at Chicago O'Hare. Activity at
Tamiami and Van Nuys Airports is approximately 99 percent
general aviation aircraft.
Additionally, data were obtained on the uses and locations
of taxiways, runways, terminals, hangars, heating plants,
fuel storage areas, and roadways at each airport in order to
locate and quantify the various sources of emissions during
the operation of aircraft.
Based on projections from Reference 3, revised to
incorporate more accurate emission factors, total projected
emissions of pollutants from aircraft and from all sources
13
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Table 3
Present and Projected LTD Cycles for 1970, 1975, .md 1980
Airport
All FAA operated airports
Air carrier airports
Los Angeles
International
Washington
National
J. F. Kennedy
International
Chicago
General aviation airports
Van Nuys ,
California
Tamiami,"
Florida
Type of aircraft
Air
carrier
-
203,900
109,800
188,800
314,300
20
General
aviation
-
59,900
55,500
27,800
21,200
279,400
200,800
Military
-
4,200
1,500
-
2,700
"
Helicopters
-
4,050
-
Total L'TO cycles
1970a
28 x 106
272,000
166,700
219,200.
339,900
281,600
200,800
1
1975
39 x 106
305,200
169,800
208,500
357,000
1
1980
59 x 106
358,100
173,500
241,300
410,800
700,000
parts do not add up
b!971 estimated activity
to total, LTD cycles not classified by type were included in total
-------
were calculated for the years 1975 and 1980 at each of the
selected airports except New Tamiami (which lacked reliable
activity projections). These projections are presented in
Table H for total hydrocarbons, carbon monoxide, nitrogen
oxides, sulfur dioxide, particulate matter (including lead),
and lead. For a more complete assessment of proposed
control strategies, emission projections for three of the
pollutants (hydrocarbons, carbon monoxide, and nitrogen
oxides) were also developed for 1990. The projected values
for 1990 are presented in the discussion of control
feasibility and impact. The emission projections are based
on present emission rates for each aircraft engine class and
do not incorporate potential future reductions in emissions
as a result of aircraft emission standards. The projected
aircraft emissions reflect increased activity and changes in
the mix of existing engines.
At the four air carrier airports during the 1970*s, as a
result of continued introduction of jet engines found in
present-day new jet aircraft, total emissions of carbon
monoxide from aircraft are not projected to change greatly.
Hydrocarbon emissions, however, although predicted to
increase by 18 percent at Washington National Airport, are
expected to decrease by about 60 to 70 percent at Los
Angeles, John F. Kennedy, and O«Hare Airport. The estimated
average increase in aircraft operations is 20 percent at
these airports during the 1970»s, indicating in general,
lower hydrocarbon and carbon monoxide emissions from the
newer and, in many cases, larger engines. As shown in Table
U there will be substantial increases in aircraft NOx
emissions of 275 percent at Los Angeles, 1U6 percent at John
F. Kennedy, 98 percent at O'Hare, and 33 percent at
Washington National Airport between 1970 and 1980. These
increases reflect the greater amounts of NOx emitted during
an entire LTO cycle from the newer engines. Some increases
in SO2 and particulate emissions from aircraft are
projected, since such increases usually follow increases in
aircraft operations.
At Van Nuys Airport, the projected increases in all
pollutants parallel the large projected increases in
activity at this airport. During the 1970«s, emissions of
hydrocarbons, carbon monoxide, NOx, and lead from aircraft
are projected to increase by about 110 percent.
As Table U indicates, we estimate that in 1975 CO emissions
from aircraft at Van Nuys Airport will exceed CO emissions
from aircraft at a major commercial airport, Washington
National. This estimation indicates the increasing
importance of general aviation aircraft emissions, and
15
-------
Table 4. CURRENT AND PROJECTED EMISSIONS*
(tons/year)
FROM AIRCRAFT AND AIRPORTS
Airport
and year
Los Angeles
1970
1975
1980
Washington
National
1970
1975
1980
John F. Kennedy
1970
1975
1980
O'Hare
1970
1975
1980
Van Nuys
1970
1975
1980
Particulates
Aircraft
570
610
680
231
242
286
570
550
550
900
970
1,100
3.2
5.4
7.7
Airport
total
616
627
693
253
253
297
660
605
583
1,001
1,023
1,100
3.7
5.7
7.8
NOX
Aircraft
3,060
6,790
11,490
820
980
1,090
2,580
4,660
6,370
3,760
5,760
7,440
12.1
19.8
28.6
Airport
total
4,369
8,110
12,480
1,074
1,211
1,277
4,846
6,640
7,580
6,290
7,520
8,540
27.5
34.1
36.3
SO 2
Aircraft
431
490
623
105
121
143
418
415
442
562
600
718
0.033
0.066
0.099
Airport
total
434
561
726
319
330
352
902
913
957
605
660
803
0.33
0.55
0.88
Lead
Aircraft
0.3
0.9
1.0
0.5
0.5
0.5
0.3
0.4
0.9
0.2
0.4
0.6
3.2
5.3
7.6
Airport
total
35.2
22.0
7.8
4.8
2.1
0.9
53.9
27.5
7.8
63.8
28.6
7.7
3.6
5.5
7.6
Carbon monoxide
Aircraft
16,030
16,630
18,480
2,410
2,700
3,030
12,590
11,280
10,680
14,740
13,840
13,530
1,650
2,750
3,960
Airport
total
29,230
28,730
27,280
3,731
3,691
3,470
32,390
26,680
18,380
34,540
31 ,440
22,330
1,870
2,860
4,070
Total
hydrocarbons
Aircraft
12,570
8,660
4,770
610
680
720
9,490
5,700
2,830
9,580
6,300
3,710
100
165
242
Airport
total
14,660
10,530
5,760
864
823
775
12,680
8,010
3,930
13,210
8,830
4,920
132
198
264
Based on aircraft emissions below 3000 feet altitude.
Includes lead.
-------
emphasizes that during an LTO cycle, CO emissions from a
small general aviation piston engine can, in many cases, be
expected to approach CO emissions from a commercial air
carrier turbine engine.
The existing and potential air quality impact of sulfur
oxides and lead is considered to be negligible in comparison
to other sources of these two pollutants. Therefore, no
further analysis was performed on these pollutants in this
study. The particulate problem associated with aircraft
operations has already been shown to be confined to the
smoke problem and hence the air quality impact discussion is
very brief in this report.
Emission projections for the additional airports at Dallas-
Ft. Worth, San Francisco, Denver, and Boston were based on
the similarity of the particular airport to one or more of
those in Table 4.
17
-------
RESULTS OF IMPACT EVALUATION
REGIONAL IMPACT
The implementation plans of eight air quality control
regions were reviewed in detail. These regions have
critical problems in terms of their ability to meet the
National Ambient Air Quality Standards and also have
airports with high air passenger activity. Pour of the
regions considered are those in which the four major air
carrier facilities considered in the Northern Research Study
are located. The analysis of regional implementation
strategies was extended to include San Francisco, Boston,
Denver, and Dallas-Fort Worth. Table 5 reflects the present
status of implementation plans relating to the control
strategies (by pollutant) for these regions and their
ability to meet the air quality standards by 1975.
As an aid in assessing aircraft emissions and their regional
impact Tables 6 through 13 present the 1970 emission
inventories and emission projections for 1975 and 1980, for
the eight regions cited, along with reductions expected as a
result of Federal standards for emissions from light-duty
motor vehicles.9 In addition, one or more of the proposed
strategies representing ccntrol of smaller sources or
additional controls on motor vehicle sources are cited so
that the spectrum of control demands is evident. Present
and projected estimates of aircraft emissions are also
tabulated, along with the reductions to be expected if the
proposed standards are met. The reductions for 1975
represent application of the only feasible control strategy
available by that date, ground operation control. Two
values are shown for 1980 potential reduction: the first
represents the actual reductions achievalbe by 1980; the
second, mass reductions achievable in the 198C—1990 time
frame as a result of the proposed 1979 design standards.
Note that in 9 of the 17 possible region/pollutant
combinations (an 8-region by 2-pollutant matrix plus Los
Angeles NOx) the potential reductions in aircraft emissions
are comparable to (at least half of) or greater than the
reductions due to minimum strategies proposed for 1980 by
the various regional or State agencies.
More importantly, in « of these 9 cases, the air quality
standard will not be met or will be only marginally met in
the 1975-1980 time frame. In these cases aircraft emission
reductions before and after 1980 would represent effective
control strategies. In all regions facing difficulties in
19
-------
TABLE 5
ABILITY TO MEET
NATIONAL AMBIENT AIR QUALITY STANDARDS
IN 1975
(yes = able, no = unable)
Based on Current State Implementation Plan Information
Region
1. Los Angeles
2. New York
3. Washington, D.C.
A. Chicago
5. Denver
6. San Francisco
7. Dallas/Fort Worth
8. Boston
*N02 air quality data is currently being reevaluated. Results of this
reassessment may require additional or accelerated control of aircraft
NOX emissions to those herein proposed.
CO
Yes
No
No
Yes
No
Yes
Yes
No
Pollutant
HC N02*
No No
No
Yes
Yes
No
No
Yes
No
20
-------
TABLE 6
METROPOLITAN LOS ANGELES INTRASTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (for entire region)
REGION WITH PROPOSED CONTROLS
(Aircraft control not included)
REDUCTION FOR SPECIFIC STRATEGIES
Present motor vehicle program
Petroleum industry
Organic solvents
Incineration
Combustion of fuels
Agriculture
Periodic vehicle inspection
Retrofit evaporative control
1/3 conversion to gaseous fuels
20% traffic reduction
AIRCRAFT CONTROL
Turbine ground operation
Turbine emission standard
Piston emission standard
Sum of aircraft control
strategies
CO
4,130
41.1
1970
HCa
651
6.8
NOX
573
4.2
CO
4,400
51.4
880
2,200
C 14.61
C i.a)
584
485
200.7
10.4
Ci
(_ 2.2)
230
175
o°2J>
10.9
1.9
(25.8)
2.3
(30.9)
15.1
any
1980C
HCa
756
3.2
130
548
25.5
(^2.21
CE3)
9.1
C? .3])
18.3
1.3
0.4
(2.7)
0.0
(0.3)
1.7
o>
NOX
668
15.6
275
350
C"i . l>
C9.Q
i
+14. 6b
I 25.6;)
27.4
1.0
(13.4)
1.0
aReactive HC based on California SIP
Increase rather than decrease due to engine operation tradeoff
'Values shown in parenthesis are projected 1990 emission reductions.
-------
TABLE 7
NEW YORK PORTION OF THE N.J. - N.Y. - CONN. INTERSTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (JFK only)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC
STRATEGIES
National Motor Vehicle
Standards
(Other Strategies)
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HC NOX
4,207
12.6
832
9.5
741
2.6
1975
CO HC NOV
A
4,840
11.3
2,630
2,139
41a
5.7
955
5.7
485
431
20. 8b
3.6
.4
851
4.7
727
101
23. 6C
1980d
CO HC NOX
5,260
10.7
1,136
4,066
44. 6a
5.1
0.8
(9.6)
1,040
2.8
268
702
21b
1.6
0.6
.(3.0)
926
6.4
622
269
25. 6C
0.5
(6.1)
ho
NJ
aDowntown truck control.
-Process evaporation.
Gas space heat downtown.
Values shown in parenthesis are projected 1990 emission reductions.
-------
TABLE 8
NATIONAL CAPITAL INTERSTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (National)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC
STRATEGIES
National Motor Vehicle
Standards
Minimum Strategies
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HC NOX
1,389
2.4
267
0.6
184
0.8
1975
CO HC NOX
1,554
2.7
1,025
470
25. f
1.1
299
0.7
155
97
a
2.2
.3
0.1
206
0.9
188
20
0.55
198QC
CO HC NOX
1,735
3.0
460
1,215
a
11.3-
1.2
0.2
(2.9)
335
0.7
117
190
erf:
.4
0.2
230
1.1
150
78
b
0.3
0.1
(1 . 0.)
N>
OJ
Use of liquified petroleum gas for fleet vehicles.
Motor vehicle maintenance and inspection.
'Values shown in parenthesis are projected 1990 emission reductions.
-------
TABLE 9
ILLINOIS PORTION OF THE METROPOLITAN CHICAGO INTERSTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (O'Hare)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC
STRATEGIES
National Motor Vehicle
Standards
Aggregate Stationary
Source Controls3
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HC NOV
X
2,730
14.7
606
9.6
383
3.8
1975
CO HC NOV
A.
3,064
13.8
1,480
1,383
r^bi
nrg
688
6.3
235.5
262
(TTV
co>
0.6
435
5.8
306
94.5
6.0d
1980e
CO HC NOY
A
3,496
13.3
506
2,748
rT3b>
6.2
1.1
MMM^HM^L
796
3.7
96
465
fl~3C>
2.0
0.8
5T5V
504
7.4
196
265
7.4<3
0.6
(6.5;
Note: Midway emissions = 20% O'Hare.
^Minimum source strategy assumed to be 10% of aggregate.
Incinerators.
cRefinery solvents.
Values shown in parenthesis are projected 1990 emission reductions.
-------
TABLE 10
METROPOLITAN DENVER INTRASTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (Stapleton)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC -
STRATEGIES
National Motor Vehicle
Standards
Retrofit Pre '67 Cars
Tune-ups
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HC NO
X
873
4.5
174
2.6
139
1.0
1975
CO HC NO
X
965
4.6
516
280
66
103
1.8
192
1.7
98
70
14.5
9
1.0
0.2
154
1.6
1980s
CO HC NOY
J\.
1,065
4.8
252
757
12
44
1.7
0.3
(3.5)
212
1.0
65
140
C2.6>
4
0.5
0.2
C J. * -L^r* '
170
2.0
0.2
(1.8)
Values shown in parenthesis are projected 1990 emission reductions.
-------
TABLE .11
SAN FRANCISCO BAY AREA INTRASTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (S.F. Int'l.)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC
STRATEGIES
National Motor Vehicle
Standards
Minimum Strategies
Vehicle Inspection
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HCb NOX
1,980
11.0
315
3.2
266
2.1
1975
CO HO NOX
2,150
11.5
451
1,030
16*
266
5.3
0
340
2.2
89
172
02
10.9
m>
0.1
287
4.7
156
77
21. 8d
+7.3f
1980a
CO HCb NOV
X
2,350
12.7
291
1,730
rr8c|
106
5.6
1.0
(13 . 33
371
1.2
69
252
cr
2.9
0.7
0.2
C1.4)l
313
7.9 .
125
*
164 •
10. 8S
i
;
0.5 •'
6.8
i
Note: Oakland and San Jose = 20% of S.F. Int1].
Rvalues shown in parenthesis are projected 1990 emission reductions.
Defined highly reactive.
Agricultural burning.
d20% traffic reduction.
"1/3 conversion to gaseous fuels.
Increase rather than reduction.
-------
TABLE 12
METROPOLITAN DALLAS - FORT WORTH INTRASTATE AQCR
EMISSIONS, KILOTONS PER YEAR
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (Love Field)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC
STRATEGIES
National Motor Vehicle
Standards
Minimum, Control Stationary
Source and Gases
Maintenance and Inspection
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HC N0x
2,340
7.2
454
4.5
280
1.8
1975
CO HC NO
X
2,620
6.9
3.1
509
3.0
256
199
6.4
48
1.7
0.3
314
2.7
270
44
1980 a
CO HC NOX
2,920
6.7
2.9
0.5
(5.9)
.
567
1.8
149
393
6.4
19
0.9
0.4 :
1.8
350
3.5
178
172
0.3
(3.2)
Values shown in parenthesis are projected 1990 emission reductions.
-------
TABLE 13
METROPOLITAN BOSTON INTRASTATE AQCR
EMISSIONS, KILOTONS PER YEAR
NJ
oa
EMISSIONS
WITHOUT ADDITIONAL CONTROLS
Region
Aircraft (Logan)
WITH STATE PROPOSED CONTROLS
Region
REDUCTION FOR SPECIFIC
STRATEGIES
National Motor Vehicle
Standards
Gasoline Handling
Evaporative Losses
Solvent Control
Other Strategies Sited
None Actually Proposed
AIRCRAFT CONTROL
Ground Operation
Emission Standards
1970
CO HC NOV
A
1,352
7.9
263
5.8
1
206
1.6
1975
CO HC NOV
A
1,555
7.0
1,034
502
3.5
302
3. '5
141.5
95
12
52
2.2
0.2
237
2.8
211.7
25
1980a
CO HC NOV
A
1,690
6.5
490
1,200
3.1
0.5
(5.9)
t
329
1.7
82
178
13
56
1.0
0.4
(1.8)
258
3.9
183
75
0.3
(3.7)
Values shown in parenthesis are projected 1990 emission reductions.
-------
meeting the air quality standards, every viable control
strategy will have to be applied to meet requirements of the
Clean Air Act.
Table 6, which relates to the implementation plan for
metropolitan Los Angeles, lists all proposed strategies and
gives aircraft emission figures representative of all
aircraft activity, including LAX, in the region. For a
specific region, total aircraft emissions can be
substantially higher than those attributed to the area«s
major air carrier airport. The region encompassing
metropolitan Los Angeles, for example, includes, besides
LAX, several smaller commercial air carrier airports and
numerous general aviation facilities. It is not surprising
then that LAX accounts for only U0%, 70%, and 73%,
respectively, of the total regional aircraft emissions of
CO, HC, and NOx in 1970. This general relationship of
emissions attributable to major airports and total regional
aircraft emissions could be expected in similar highly
populated air quality control regions.
In the Los Angeles region, uncontrolled emissions from
aircraft are expected to account for 14% of the CO, 2.5% of
the reactive HC, and 5.5% of the NOx total emissions by
1980.
Emissions from piston aircraft have a particularly
significant impact on regional CO levels. Although piston
aircraft were responsible for about 0.5% of the total CO
emissions in 1970, their contribution to CO emissions, if
uncontrolled, is expected to reach 10% by 1980.
SUB REGIONAL AND LOCALIZED IMPACT
This section deals with the effect of aircraft emissions on
air quality at major airports and downwind of these
airports. Emission densities and other parameters of
emission intensity and air quality impact are first
presented to provide indications of the contribution of
aircraft to air pollutant concentration around a number of
major U. S. airports. Then detailed results of sampling and
dispersion modeling are presented to give deeper insight
into the localized impact of aircraft at airports where
aircraft contributions to air pollutant concentration are
expected to be particularly important.
GENERAL INDICATORS OF LOCALIZED AIR QUALITY IMPACT
Passenger Usage Density and Air Pollution Potential. An
indication of localized impact of aircraft on air quality is
29
-------
presented in Table 1U for the 20 largest U. S. air carrier
airports, as determined by passenger enplanement. On the
basis of concentration of passenger activity, proximity of
the airport to built-up areas, and meteorological pollution
potential»o (a function of atmospheric mixing height and
wind speed), seven airports, designated by asterisks in
Table 1U, could be expected to be particularly important
contributors to localized air pollutant concentrations. The
results of Table 14 indicate most directly the airport
contributions to localized carbon monoxide concentrations-
the airport contributions to oxidant and nitrogen dioxide
concentrations are indicated less directly because
intermediate atmospheric reactions are involved in their
production.
Emission Density Comparison. Emission densities have been
calculated for four of the airports that show a major air
quality impact potential. Table 15 indicates that emission
densities due to aircraft alone in 1970 were in most cases
comparable to those of densely populated metropolitan areas
served by the corresponding airports.
This emission density comparison suggests that, in these
four airport areas, the contribution by aircraft to ambient
air concentrations of hydrocarbon, CO, and NOx is
substantial. Such contributions are particularly important
where major airports lie in or near metropolitan areas in
which national ambient air quality standards are currently
exceeded. AS shown in Table 5, this is the case for the
four areas considered.
The comparison of emission densities (airport versus
metropolitan area) for 1975 and 1980 demonstrates that the
ratio of the airport emisison densities to those of the
metropolitan areas will increase in most cases, sometimes
dramatically. The trends can be identified in Table 15,
which indicates that aircraft are expected to become
increasingly significant contributors to air pollutant
concentrations at airports and in their vicinities.
It should be kept in mind that the emissions densities
presented in Table 15 are averaged for the given areas and
that variation in actual emission rates within the defined
areas exist.
The majority of the HC, CO, and NOx emissions in
metropolitan areas are due to area rather than point
sources. This tends to minimize variation in emission
densities throughout a metropolitan area. However, one
would expect to observe higher emission densities where
30
-------
TABLE 14
INDICATIONS OF LOCALIZED AIRPORT IMPACT OF 20 LARGEST AIR CARRIER AIRPORTS
Enplaned
Passengers
Millio-ns
Airport (FY 1970)
* O'Hare
* Los Angeles
* Atlanta
* J.F. Kennedy
* La Guardia
San Francisco
* Dallas (Love)
* Washington (Nat.)
Boston
u> Miami
^ Detroit
Denver
Newa rk
Philadelphia
St. Louis
Pittsburgh
Minneapolis
Cleveland
Seattle
Houston
13.5
8.5
8.2
7.0
5.9
5.5
5.3
4.9
4.5
4.4
3.7
3.5
3. L
3.2
3.1
3.0
2.6
2.5
2.5
2 . 2
Aircraft Activity
Percent Percent
Commercial General
Aviation Aviation
95
76
86
86
80
78
70
66
66
66
71
48
76
70
58
64
55
45
68
73
5
22
14
14
20
21
30
33
34
31
27
52
24
30
38
29
37
55
32
27
Airport
Area,
Miles2 "
14.1
4.8
6.6
8.1
0.9
8.1
2.0
1.0
3.7
4.2
7.5
7.2
3.4
3.9
2.9
4.8
4.6
2.3
2.8
11.4
Passengers
'area X 105
36
40
33
25
65
20
38
49
24
22
14
13
19
17
18
14
13
17
16
6
Airport
Proximity to
Built-up
Areas e
2
2
2
2
2
1
2
2
1
2
2
2
2
2
2
2
1
Morning
Meteorological
Air Pollution
Potential (x/Q)b
50
50
50
30
30
50
30
70
20
20
40
30
30
30
40
80
60
50
40
30
a 1 = Residential and business areas adjacent to airport boundaries.
2 = Residential and business areas adjacent to airport boundaries, and a significant frequency of
wind from airport toward these areas.
This parameter is based on a simple model of dispersion over urban areas, in which an average area-
wide pollutant concentration, \, is normalized for an average emission rate, 0. High x/Q values
indicate high potential pollutant concentrations. The values listed above are morning upper
decile levels for a 10-kilometer along-wind distance. More detailed information on this parameter
is presented in Ref. 10.
-------
Table 15. COMPARISON OF EMISSION DENSITIES FOR AIRPORTS VERSUS URBAN AREAS FOR 1970, 1975, and 1980
Los Angeles metropolitan area
Los Angeles Airport - all
emission sources
Los Angeles Airport - air-
craft alone
New York metropolitan area
Airport - all emission
sources
Airport - aircraft alone
Washington D.C. metropoliian
area
National Airport - all
emission sources
National Airport - air-
craft alone
Chicago metropolitan area
O'Hare Airport - all
emission sources
O'Hare Airport - air-
craft alone
Area ,a
mi2_
1250.0
3.9
3.9
320.0
4.5
4.5
61.0
1.0
1.0
227. 0
6.7
6.7
Emission densities,13 tons/mi2-day
1970
Carbon
monoxide
7.2
20.6
11.2
14.5
19.6
7.7
12.5
10.2
6.6
8.1
14.1
6.0
Hydro-
carbons
2.0
10.3
8.8
3.4
7.7
5.8
1.7
2.4
1.7
2.5
5.4
3.9
Nitrogen
oxides
1.0
2.0
1.1
3.6
2.1
0.8
1.7
1.7
1.0
1.4
1.9
0.8
1975
Carbon
monoxide
4.8
20.2
11.7
11.4
16.2
6.9
7.9
10.1
7.4
6.3
12.9
5.7
Hydro-
carbons
1.1
7.4
6.1
2.4
4.9
3.5
1 .1
2.3
1.9
1.7
3.6
2.6
Nitrogen
oxides
0.9
3.5
2.6
3.6
2.7
1.5
1.5
1.8
1.2
1 .4
2.0
1.3
1980
Carbon
monoxide
2.8
19.1
13.0
5.5
11.2
6.5
3.3
9.5
8.3
1 .4
9.1
5.5
Hydro-
carbons
0.9
4.0
3.4
1.3
2.4
1.7
0.4
2.1
2.0
0.9
2 n
C- • \J
1.5
Nitrogen
oxides
0.8
5.6
4.9
3 2
-------
there is high population activity such as in downtown and
industrial areas as opposed to residential areas within the
region.
Detailed Investigation of Localized Pollutant Concentrations
The emissions density data previously discussed pointed to
the fact that major airports are and will continue to be
significant area sources of air pollution emissions. If the
health and welfare of the exposed population is to be
protected, the conclusion may be drawn that the emissions
must be reduced equally for all such sources, e.g., whether
they be airport or non-airport area sources of pollution.
8-Hour Carbon Monoxide Concentrations. Carbon monoxide
concentrations at the Los Angeles International Airport and
in its vicinity were measured from May to November, 1970*.
The sampling was done by the Los Angeles County Air
Pollution control District under EPA contract. Carbon
monoxide concentrations were continuously monitored at
several sampling sites, including U sites in the airport
terminal area, and 2 sites located upwind and downwind of
the airport complex. At all of these, ambient
concentrations of CO were measured. The monitoring sites
were located as shown in Figure 1. Data from site 209 were
analyzed extensively to determine as quantitatively as
possible the air quality impact of aircraft CO emissions on
8-hour ambient CO concentrations in residential and business
areas downwind of the airport.
Site 209 is located directly downwind of the L. A. airport
when the wind blows from its most frequent direction, as
indicated by the wind rose in Figure 1. Until recently this
area was a residential neighborhood, but now it is almost
completely owned by the Los Angeles Airport. Other
residential areas, however, are located only a few blocks
west and north of this area; and it was concluded that
concentrations measured at site 209 are indicative of
concentrations in such residential areas.
Figure 2 presents an estimated frequency distribution of
carbon monoxide concentrations at site 209 during the winter
months, the time of highest CO concentrations in the Los
Angeles area. This frequency distribution is based on
sampling data collected at site 209 during August and is
adjusted to represent wintertime concentrations using a
seasonal conversion based on air quality data for the entire
Los Angeles basin. Derivation of the results shown in
Figure 2 is detailed in Appendix A. It can be seen, in
Figure A-3 of that section, that site 209 is exposed to the
33
-------
~\ -? v '•OH pa
i«s^a^i|iy
•sw^-iWisyfl r..v.','":;•;'..;;
Figure 1
AIR SAMPLING LOCATIONS
AT LOS ANGELES INTERNATIONAL AIRPORT
^M I^WHF-
?„: .."isi^^-^A-WESTCiiFr'
* *«?.*.* "3.O.J-,"
S$&t$*^
r i i •sS»i*sv«-*r™¥W^
••] > J • !: A i
Inair 3
iv1—7f r !?- STHiWtniF- i^'^h, h-i V'j't v
!„ :y^;;|; |i|fe =?--lUiJ wfi] jjlti -
1^—a !l ilfellWl "' iUlfeS^i
*...:»-:3i rW L
\ =
FREQUENCY OF WIND DIRECTION AT L.A.
AIRPORT, IN PERCENTAGES OF TOTAL,
1951-1960
11
Calm - 14%
-------
FIGURE 2
EXPECTED CO CONCENTRATIONS, 8-HOUR AVERAGING TIME, WINTER 1970, STATION 209, LAX
60
a.
ex
20
H
W 10
CJ
z
8 8
g
o
3:
oo
Ambient A/Q Standard = 9 ppm
13 days/month
99.9 99 90 70 50 30
Probability (%) of exceeding the given pollutant level.
10
0.1
-------
same levels of carbon monoxide whether it be influenced by
pollution from other than the airport (easterly winds) or
from the airport alone (westerly winds). Figure 2 shows
that the 8-hour CO standard, which is not to be exceeded
more than once per year, is estimated to have been exceeded
at site 209 13 times per month, or 39 times in the winter 3-
month period.
Part of the carbon monoxide concentrations shown in Figure 2
is due to aircraft. To estimate the portion of the
concentration that is due to aircraft, dispersion modeling
was applied. The dispersion modeling methodology is
discussed in Appendix B. The model's resulting estimate of
the current contribution by aircraft to total CO
concentrations, shown in Figure 3, indicates that aircraft
are highly significant contributors to local CO
concentrations downwind of the airport. Figure 3 indicates
that expected aircraft contributions constitute 60-70% of
the total CO concentrations in the area of site 209.
Between 1970 and 1980, CO emissions from aircraft are
estimated to increase by fifteen percent (Table 4) while CO
emissions from all other sources in the Los Angeles area are
expected to decrease to 20% of their 1970 levels.»« Using
the estimated changes in emissions from these two source
categories, and assuming that the emission changes yield
proportional changes in pollutant concentrations due to each
source category, CO concentration frequency distributions
for various aircraft contributions can be derived from
Figure 2. The result is presented in Figure U for various
1970 aircraft contributions to pollutant concentrations.
Figure U indicates that without controls of CO emissions
from aircraft the 8-hour CO standard will be exceeded more
than once during the 1980 winter months at site 209 if the
aircraft contribution to the total CO concentration in 1970
is as little as 20%. As shown in Figure 3, the 1970
contribution by aircraft exceeds this percentage over a
large area downwind of the airport. If the reasonable
assumption is made that Figure 2 approximates the 1970
winter CO concentration frequency distribution in this area,
it is evident that in 1980 the 8-hour CO concentrations will
continue to exceed the standard in this same area downwind
of the Los Angeles Airport if aircraft CO emissions are not
controlled.
As noted in Appendix A, the analysis resulting in Figures 2
and H can be repeated using data from September, rather than
from August, as a basis. The September data will yield
higher concentrations than will the August data for similar
36
-------
u*-fi*-—\-{-{-*ri--£.r.\
-/•y.l i._^_._/»«.*__L ,.i, ,.(.- .* .„*..'!
-•v-.U—V-L-M'..!.'.!1---- -: ?,
:.;.
~ '•• • :~
FIGURE 3
VICINITY OF LOS ANGELES INTERNATIONAL:
Percent Contribution by Aircraft to
Carbon Monoxide Levels
J I r-'V^lt I ! 1 I I i ."i:";-"-i" "77j .:•• j^T:."" ;
' '• :r!:^---r
<. t CK-J?--
\ I~;.?I !V
V Y" """"• EL SEGUKDO
-------
oo
H
2
W
U
§
u
o
u
PC;
o
i
oo
FIGURE 4
FREQUENCY DISTRIBUTIONS FOR CARBON MONOXIDE FOR VARIOUS
AIRCRAFT EMISSION CONTRIBUTIONS AT STATION 209 - WINTER 1980
Notes
1. 80% rollback from 1970 on non-AC sources
2. 1980 AC CO emissions = 1.15 X 1970 emissions
AMBIENT A/Q STANDARD = 9 ppm
99.9 99 90 70 50 30
Probability (%) of exceeding the given pollutant level
0.1
-------
frequencies of occurrence. Consequently, -the results from
the September data analysis can be used to indicate an upper
value of a range of frequencies at which the 8-hour CO
standard is exceeded; the results from the August data can
be used to indicate a lower value of the range. The ranges
for 1970, and for 1980 with various aircraft contributions,
is presented in Table 16.
1-Hour CO Concentrations at the Los Angeles Airport. The 1-
hour CO air quality standard of 35 ppm (10 uq/m3) was
exceeded at only one of the outdoor continuous sampling
locations at the Los Angeles Airport. A summary of the 1-
hour sampling data at these receptors is presented in Table
17, which indicates that only at site 205 was the 1-hour CO
standard frequently exceeded. Site 205 was located next to
heavy automobile traffic en World Way Boulevard at an
automobile passenger unloading area. The 1-hour CO standard
was exceeded 12 times during the approximately 1-week period
of sampler operation. Expected reductions in CO emissions
from automobiles probably would reduce concentrations at
sites such as 205 to levels below the 1-hour standard.
Generally the 8-hour CO standard of 10 ug/m3 is the most
difficult of the two standards to reach, and statistically
if the 8-hour standard is met, the 1-hour CO standard will
also be met.»3
Carbon Monoxide Concentrations at Other Airports.
Dispersion modeling was used to provide estimates of 1-hour
CO concetnrations both from aircraft alone and from all
airport and adjacent sources within 10 kilometers of the
center of each airport. This modeling was done for Los
Angeles, J. F. Kennedy, Chicago-O'Hare, and Washington
National Airports. The results, presented in Table 18, are
predicted concentrations at airport area points where: (1)
the general public could have access for 1-hour periods, and
(2) the total concentrations, as estimated by dispersion
modeling, exceed the standards.
Although minimal reliance should be placed on the precise
numerical values predicted by the model, these values are of
the same order of magnitude as the values from actual
measurements presented in Table 17. These results indicate
that localized carbon monoxide effects are not limited to
Los Angeles Airport.
The potential of high 8-hour CO concentrations downwind of
other airports, with large aircraft contributions, exists
near airports besides Los Angeles Airport. As previously
discussed. Table 11 indicates the potential of such
concentrations at six additional airports.
39
-------
TABLE 16
EXPECTED RANGE OF DAYS THAT 8-HR STANDARD WILL BE EXCEEDED IN
VICINITY OF L.A. AIRPORT, 1970 and 1980a
Based on
August
Datab
Based on
September
Data
Days Standard Exceeded
in 1970
Days Standard Exceeded
in 1980, With Following %
Contributions by Aircraft
(at 1970 emission levels)
to Total CO Concentrations
80%
60%
40%
20%
0%
39
36
22
9
1
0
to
to
to
to
to
to
65
61
49
32
14
1
aBecause the highest CO concentrations occur during winter months,
it is assumed that the frequency of exceeding the standard during the
winter quarter gives the frequency of exceeding the standard the
entire year.
From Figures 2 and 4.
40
-------
TABLE 17
LOS ANGELES AIRPORT
NUMBER OF TIMES THE 1-HOUR CO STANDARD WAS EXCEEDED
MAY 10 THROUGH NOVEMBER 9, 1970, CONTINUOUS SAMPLING SITES
Site*
201
203
204
205
208
209
Downtown LA
Total Hours
of Sampling
3710
4256
4258
637
4326
4279
4965
Number of Hourly
Values When
Standard Exceeded
0
2
0
12
1
0
3
Highest Two
Hourly Values
27, 26
46, 40
23, 19
51, 49
37, 28
31, 27
37, 35
*Refer to Figure 1 for Location.
41
-------
Table 18
Dispersion Model Estimates of 1-Hour
Carbon Monoxide Concentrations
Site Location*
JFK (T)
JFK (T)
JFK (T)
LAX (P)
LAX (P)
ORD (T)
ORD (S)
DCA (P)
DCA (P)
CO Concentration, mg/nP
Aircraft Sources Only Total
85
4
3
55
32
21
9
110
45
100
45
44
62
45
41
41
120
59
*DCA = Washington National Airport, LAX = Los Angeles International
Airport, JFK = John F. Kennedy International Airport, and ORD =
O'Hare Airport, Chicago
(T) = Terminal area
(P) = Peripheral area--away from terminals, but within airport
boundary
(S) = Outside of airport boundary, in airport surroundings
42
-------
Hydrocarbon and Potential Oxidant Concentrations. Isopleths
of 1970 hydrocarbon concentrations due to aircraft alone at
the Los Angeles Airport are presented in Figure 5. These
isopleths are based on the dispersion modeling methodology
presented in Appendix B, and are a result of meteorological
conditions that are particularly conducive to high
hydrocarbon concentrations. Such conditions would be
expected to occur at least once per year.
The results indicate that there are large areas surrounding
the airport where the hydrocarbon concentrations due to
aircraft are well in excess of the standard.
Between 1970 and 1980, Table 4 indicates that at the Los
Angeles Airport, hydrocarbon emissions from aircraft will
decline to about UQ% of their 1970 values. These reductions
are reflected in Figure 6 which presents isopleths of 1980
hydrocarbon concentrations due to aircraft alone, at Los
Angeles Airport, based on meteorological conditions
equivalent to those used for the isopleths in Figure 5.
Even with the reduction in aircraft hydrocarbon emissions,
it is likely that in 1980 the hydrocarbon standard will
continue to be exceeded over a large area due to aircraft
emissions alone.
As indicated earlier, hydrocarbon concentrations at levels
typically found in the atmosphere are not harmful to health.
However, if airport hydrocarbon concentrations were followed
downwind for several hours under conditions conducive to the
accumulation of high oxidant concentrations,7 aircraft-
generated hydrocarbons could be expected to be large
contributors to downwind oxidant concentrations over the Los
Angeles area.
A modeling analysis was performed to estimate hydrocarbon
concentrations downwind of Los Angeles Airport in 1980. The
meteorological conditions used were similar to those used
for Figures 5 and 6. The methodology of this analysis is
presented in Appendix C, and results are presented in Figure
7. The three curves in Figure 7 show nonmethane hydrocarbon
concentrations downwind of Los Angeles Airport resulting
from the surroundings plus total airport emissions, total
airport emissions alone, and aircraft emissions alone. The
initial concentration at the western airport boundary (0 km
in Figure 7) is shown to be zero, which is a result of the
proximity of the western boundary to the ocean, wind
direction from the west, and the assumption of negligible
hydrocarbon concentrations in wind coming off at the ocean.
At a point 3 hours downwind (16 km from the eastern airport
boundary) the overall hydrocarbon concentration will have
43
-------
1—•-. .... '.,.. '
• •_ ° ':' :' :'- •'
£5.vv
ife
TY!!;!'
(numbers in^yg/m )
FIGURE 5 HYDROCARBON ISOPLETHS IN THE VICINITY OF LOS ANGELES INTERNATIONAL: AIRCRAFT SOURCES
3-Hr Average for 1970 (6-9 AM)
-------
ww
r ~'v^-
A
;. ^.-_L •' i.Ji; -~;: -I'; __•_• J." ' -
rjTtS^Ti i":l i i i ."iKf^-'i"7=5 ,:i"j."
(numbers in
FIGURE 6 HYDROCARBON ISOPLETHS IN THE VICINITY OF LOS ANGELES INTERNATIONAL: AIRCRAFT SOURCES
3-Hr Average for 1980 (6-9 AM)
-------
600 «
FIGURE 7
CALCULATED NON-METHANE HYDROCARBON CONCENTRATIONS
DOWNWIND OF LOS ANGELES AIRPORT FOR 1980
WITH NON-AIRCRAFT SOURCES CONTROLLED
500.
400J
Meteorological Conditions Used:
Wind from West
Stability Class 3
Wind Speed 1.5m/sec
Mixing Height = 200m
E
00
c
o
•H
C
01
o
c
o
u
300
200.
100
Total, All Sources
Total Airport
Aircraft Alone
Airport East Boundary
(3.2 km)
8
12
16
20
24
DOWNWIND DISTANCE, KILOMETERS
-------
been in excess of the standard for 3 hours, enough time for
possible formation of oxidant in concentrations exceeding
the standard.
It is important to emphasize that this analysis was
performed for 1980. If it were repeated for 1970, the
concentrations for each of the curves would be at least
double the 1980 values.
The emissions densities presented in Table 15 indicate that
among the four airports studied, emission densities from
aircraft alone are highest at Los Angeles Airport. However,
the range among these emission density values is still less
than a factor of 2.3 in 1980, indicating that ccnclusions
concerning future aircraft-generated hydrocarbon and oxidant
concentrations at the Los Angeles Airport and vicinity apply
generally to the other airports studied, and that additional
reductions in aircraft-generated hydrocarbon concentrations
are necessary.
Oxides of Nitrogen. Although the ambient air guality
standard is for NO2 (100 ug/m3, annual concentration), the
result of the dispersion modeling is presented as oxides of
nitrogen (NOx). This is done because there exists no well-
defined relationship for the conversion of NO to NO2. In
the presence of hydrocarbons; the NO to NO2 conversion is
accelerated; best estimates indicate that 90 percent of the
NO is converted to NO2 within a 2-hour period in the
presence of sunlight. The reaction is essentially
negligible at night. Considering all NOx as N02 could
result in an overestimation of annual average
concentrations.
Oxides of nitrogen concentrations due to aircraft alone are
presented in Figure 8 for Los Angeles Airport area for 1970.
These modeling approximations indicate that LAX is
responsible for NOx impact over a large area surrounding the
airport. With growth of overall aircraft activity, and the
changeover to bigger and higher pressure ratio turbine
engines, aircraft emissions of NOx will increase greatly
between 1970 and 1980. Present and expected future NOx
emissions from aircraft at the four major airports studied
are given in Table 15, which indicates that between 1970 and
1980 aircraft emissions of NOx will increase by factors of
2.2 at O'Hare Airport, 1.U at Washington National Airport,
1.5 at Los Angeles International Airport, and 2.9 at John F.
Kennedy Airport.
The general affect of increased NOx emissions from aircraft
at LAX is reflected in Figure 9, which presents isopleths of
47
-------
r?r: n'Tnv' t
J »•
\ v -rn
\ V L^1;?.**
!HtK
(numbers in/xg/m )
^•--~z.~^': FIGURE 8 NOJ: ISOPLETHS IN THE VICINITY OF LOS ANGELES INTERNATIONAL: AIRCRAFT SOURCES
Annual Average for 1970
-------
1980 NOx concentrations due to aircraft. Figure 9 indicates
that NOx concentrations due to aircraft alone could be
widespread in residential areas around LAX, and that in some
areas, the NO2 concentrations due to aircraft are comparable
to the standard. It should be emphasized -that these NOx
concentrations are due to aircraft alone, and NOx emissions
from other sources would be expected to significantly
increase the concentrations plotted in Figures 8 and 9.
NOx concentrations of similar magnitude to those in Figures
8 and 9 can be expected in the vicinity of other airports.
For example, isopleths showing expected 1980 NOx emissions
densities due to aircraft alone for O'Hare Airport are
presented in Figure 10. Without emission controls, aircraft
using O'Hare Airport can be expected to be large future
contributors to localized NOx concentrations, as was the
case for Los Angeles Airport.
Smoke and Particulates. Smoke generated by aircraft causes
significant reductions in visibility and is a cause of
widespread complaint by affected citizens.
The 1-year air guality monitoring program conducted at Los
Angeles International Airport indicated increased soiling
effects in the airport vicinity due to aircraft activity.
Atmospheric measurements of particulates using a tape
sampler technigue gave higher readings (indicative of
soiling) for the airport area than for locations several
miles removed, such as downtown Los Angeles. Additionally,
sampling at sites surrounding and adjacent to the Los
Angeles Airport area showed increasing soiling values from
upwind of the airport to a maximum immediately downwind of
the airport.
Measurement of total weight of particulate material, based
on Hi-Vol sampling, showed little variation between airport
and downtown areas.
Results of the dispersion modeling analysis for all four
airports indicated that particulate concentrations due to
aircraft in some parts of the airports could exceed the
secondary particulate air guality standards.
49
-------
Of^r''^^'^^ i!-^:;!-
c^x^i^r
iV? 's l:-;.'i ;
r, •-• il ;:•!,•
!^^S,
'^C-i ,.?
si!
^ " '
(numbers in//g/m )
.: FIGURE 9 NO ISOPLETHS IN THE VICINITY OF LOS ANGELES INTERNATIONAL: AIRCRAFT SOURCES
Annual Average for 1980
-------
HARE
CHICAGO
TERNATIO
AIRPOR
FIGURE 10 (numbers in^ltg/m )
NO ISOPLETHS IN THE VICINITY OF CHICAGQ-Q'HARE INTERNATIONAL: AIRCRAFT SOURCES
Annual Average for 1980
-------
TECHNOLOGICAL FEASIBILITY OF CONTROLLING
AIRCRAFT EMISSIONS
Information on emission control methods is necessary to
determine the levels to which aircraft emissions can
feasibly be reduced. An earlier Federal study,* »*
identified potential control approaches including
modification of aircraft engines, fuels, and ground
operational procedures. This study indicated that
modification of aircraft engines and ground operational
procedures appear to be the most feasible and effective
control procedures. More recently, the Aerospace Industries
Association (AIA) has issued a reportis summarizing results
of investigations conducted by industry on: (1) emission
characteristics of aircraft gas turbine engines; and (2)
potential methods for reducing aircraft turbine engine
emissions. The AIA report also identifies the possibility
of reducing emissions through modifications of engines
(especially combustor design) and of ground operational
procedures.
The current reassessment of control methods must
consider each of the aforementioned approaches. In
assessing the feasibility of a control method, four factors
must be explored: (1) effect of the method on the
functioning or capacity of the aircraft system; (2)
effectiveness of the method in reducing emissions; (3) cost
of utilizing the method; and (U) time required for
implementing the method. Information on emission-
measurement instrumentation is also necessary to ensure that
aircraft emissions can be measured with the accuracy and
sensitivity required for enforcing the desired standards.
The Environmental Protection Agency has conducted
several studies (references 16-27) to obtain information for
assessment of aircraft emission control methods. This
report summarizes the information obtained in these
investigations. The specific objectives of this analysis of
aircraft emission control technology are:
(1) To identify methods of controlling aircraft
emissions through modification of engines, fuels, and ground
operations.
53
-------
(2) To estimate their effectiveness in reducing
aircraft emissions.
(3) To estimate the time required for and cost of
implementation.
(4) To assess the technology of measuring emissions
from aircraft engines and to identify areas requiring
advancements in instrumentation or test procedures.
Emission control by fuel modifications was reassessed to
evaluate developments in aircraft fuel technology. This
investigation was discontinued after preliminary analysis
indicated that no significant reductions in emissions could
be achieved by modifying fuels, except for reduction*- in
sulfur or lead content that result in proportionate
reductions of SO and lead emissions.
A list of specific emission control methods involving
engine modifications was formulated on the basis of
preliminary analyses, which indicated that each method was
feasible and offered a significant reduction in one or more
emission classes. Feasibility was assessed on the basis of
the following factors:
(1) No reduction in engine reliability (safety) .
(2) Little or no reduction in engine performance
(power-weight ratio).
(3) Reasonable cost of implementation.
The preliminary list of control methods was then
subjected to more detailed analysis of control effectiveness
and implementation costs. Control methods involving changes
in ground operations were evaluated in a similar manner.
Evaluation of the emission control methods involving
engine modifications gave primary consideration to the
following emission classes: carbon monoxide (CO), nitrogen
oxides (NOx), total hydrocarbons (including drained fuel)
(THC), dry particulates (DP) , and smoke.
EMISSION CONTROL BY ENGINE MODIFICATION
Engine Classification
To facilitate analyses of engine modificaticns, aircraft
engines are categorized according to their thrust or power
level. The classification system is indicated in Table 19.
54
-------
TABLE 19
AIRCRAFT ENGINE CLASSIFICATION
Engine class
Engine Type
Power Range,
Ib thrust or eshp
Tl
T2
T3
PI
Turbine
Turbine
Turbine
Piston
Less than 6,000
6,000 to 29,000
Greater than 29,000
All piston engines
55
-------
Although this classification system is based simply upon
power level it effectively groups engines of similar
emission potential (when the emission rates are normalized
according to an appropriate engine-size parameter) . Also,
since effectiveness factors and costs of the control methods
are similar for engine models within each class, the system
is particularly useful for this analysis.
Three classes of turbine engines are defined, and all
piston engines are included in a single class. This system
thus categorizes engines according to their principal
applications and according to certain design characteristics
that affect emission rates.
The small turbine engine class (Tl) includes most of the
turboshaft and small turbojet and turbofan engines used in
business and small commercial aircraft. It also includes
auxiliary power units (APU) used on large commercial
aircraft. These engines are considered as one class because
the relatively small size of the combustor components (or
large surface-volume ratio) makes control of certain
emissions more difficult than with larger engines.
The next turbine engine class (T2) includes most of the
turbojet and turbofan engines used in medium-to-large
commercial aircraft. The design characteristics of most of
these engines are basically similar.
The third turbine engine class (T3) includes large
turbofan engines for "jumbo" transport aircraft and the SST
engines currently in use or under development.
Emission Control Methods and Effectiveness
Technology for controlling emissions from aircraft
engines by means of engine modifications has been analyzed.
The purpose of this analysis was to identify specific
methods of reducing pollutant emissions from aircraft
engines and to indicate the reductions in rates of emission
attainable by these methods. Various engine modifications
appear to be feasible in that they can be applied to
aircraft without degrading engine reliability or seriously
reducing aircraft performance. Costs of implementing these
control methods also appear to be within reasonable limits,
at least in preliminary analysis.
Turbine Engines - The engine modification control methods
considered feasible for turbine engines are listed and
described briefly in Table 20. Six methods are, at least in
56
-------
Table 20. ENGINE MODIFICATIONS FOR EMISSION CONTROL FOR EXISTING AND FUTURE
TURBINE ENGINES
Control method
Modification
Existing engines
tl - Minor combustion
chamber redesign
t2 - Major combustion
chamber redesign
t3 - Fuel drainage control
t4 - Divided fuel supply
system
t5 - Water injection
t6 - Modify compressor air
bleed rate
Minor modification of combustion chamber and fuel
nozzle to achieve best state-of-art emission
performance.
Major modification of combustion chamber and fuel
nozzle incorporating advanced fuel injection concepts
(carburetion or prevaporlzation).
Modify fuel supply system or fuel drainage system to
eliminate release of drained fuel to environment.
Provide independent fuel supplies to subsets of fuel
nozzles to allow shutdown of one or more subsets dur-
ing low-power operation.
Install water injection system for short duration use
during maximum power (takeoff and climb-out) opera-
tion.
Increase air bleed rate from compressor at low-power
operation to increase combustor fuel-air ratio.
Future engines
t7 - Variable-geometry
combustion chamber
t8 - Staged injection
combustor
Use of variable airflow distribution to provide inde-
pendent control of combustion zone fuel-air ratio.
Use of advanced combustor design concept involving a
series of combustion zones with independently con-
trolled fuel injection in each zone.
57
-------
principle, applicable to existing engines by retrofitting of
new or modified parts, and to engines currently in
production. Two methods are considered to be applicable
only to future engines of new design, since the
modifications required are too extensive to be applied to
engines for which development has been completed.
The first control method consists of simple
modifications of the combustor and fuel nozzles to reduce
all emission rates to the best levels currently attainable
within each engine class. The degree of control attainable
depends upon the performance of specific engines compared
with those engines in the same class demonstrating the
lowest emission rates. In general, this control method
requires emission quality control (emission reduction to
levels demonstrated by other engines of that model).
Additionally, for certain high-emission engine models, it
means emission reduction to the level of other engines of
the same class. Each of the other control methods is more
specifically directed at one or two pollutant classes.
Reductions in emissions achievable through the use of a
control method vary with the pollutant considered, the
engine class, and the engine operating mode. Estimates of
the effectiveness of each control method have been made for
all combinations of these factors and are presented in
Tables 21 and 22. The estimation of emission control
effectiveness for turbine engines is based upon reductions
attainable from "lowest current emission rates." These
rates are defined as those attainable through control method
tl (table 19), minor combustion chamber redesign.
It is predicted that all engines in each class could be
modified to achieve these "best rates." The values of these
rates are listed in Table 21. These "best rates" are not
the lowest rates indicated for each engine class, but are
rates near the low end of those emission rates that appear
to be realistically attainable. The use of the "best rate"
basis is necessary to allow effectiveness estimates for each
engine class. Because of the wide variations in actual
emission rates of turbine engines, an effectiveness analysis
based on average rates would be less significant. Table 22
indicates the effectiveness of control methods t2 through
t8. Some estimates are based upon demonstrated performance.
Most, however, are not based on direct experience with these
control methods on aircraft engines. Therefore, estimates
of effectiveness are based largely on theoretical analyses
of engine performance under the operating conditions
associated with the control methods. The bases for these
estimates are summarized in Table 23.
58
-------
Table 21. EFFECTIVENESS OF tl - MINOR COMBUSTION CHAMBER
REDESIGN3 - ON REDUCTION OF EMISSIONS FROM TURBINE ENGINES
^(Emission rates in lb/1000 Ib of fuel)
Engine
class
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T3
T3
T3
T3
Pollutant
CO
THC
NOX
DP
CO
THC
NOX
DP
CO
THC
NOX
DP
Mode
Idle/taxi
25
10
3
0.2
45
10
2
0.2
50
10
3
0.1
Approach
5
1
7
0.5
6
1
6
0.5
3
1
10
0.1
Takeoff
2
0.2
11
0.5
1
0.1
12
0.5
0.5
0.1
40
0.1
aMinor combustor redesign is assumed
invisible or "smokeless" levels for
to reduce the smoke to
all engine classes.
59
-------
Table 22
Effectiveness of Engine Modification in Control
of Emissions from Turbine Engines, by Operating Mode3
Control
method
h
t2
t2
t2
t2
t3
t3
t3
t4
t4
t4
t4
t4
t4
t5
t5
t5
t6
t6
t6
t6
t6
t6
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
Engine
class
Tl
Tl
T2
T3
Tl
T2
T3
Tl
Tl
T2
T2
T3
T3
Tl
T2
T3
Tl
Tl
T2
T2
T3
T3
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T3
T3
T3
t7 or t8 ' T3
Pollutant
DP
NOX
DP
Idle/taxi
0.5
NCC
0.5
NOX j NC
THC
THC
THC
CO
THC
CO
THC
CO
THC
NOX
NOX
NOX
CO
THC
CO
THC
CO
THC
CO
THC
NOX
DP
CO
THC
NOX
DP
CO
THC
NOX
DP
NC
NC
NC
0.25
0.25
Mode
Approach
0.5
NC
0.5
NC
NC
NC
NC
NC
NC
0.25 j NC
0.25
0.25
0.25
NC
NC
NC
0.5
0.5
0.5
0.5
0.5
0.5
0.1
0.1
NC
0.5
0.1
0.1
NC
0.5
0.1
0.1
NC
0.5
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
0.5
NC
NC
NC
0.5
NC
NC
NC
0.5
Takeoff
0.5
0.5
0.5
0.5
Qd
Od
Od
NC
NC
NC
NC
NC
NC
0.1
0.1
0.1
NC
NC
NC
NC
NC
NC
NC
NC
0.75
0.5
NC
NC
0.75
0.5
NC
NC
0.75
0.5
aEmission rate is fraction of best current
through minor combustion chamber redesign
t2 = Major combustion chamber redesign
t3 = Fuel drainage control
t4 = Divided fuel supply system
t5 = Water injection
t6 = Modify compressor air bleed rate
t7 = Variable-geometry combustion chamber
t8 = Staged injection combustor
CNC indicates no change
dRefers to raw fuel drainage only
rate assumed to be attainable
and with control method cited
60
-------
Table 23
Bases for Control Method Effectiveness Estimates for Turbine Engines
Control method
Rationale
tl - Minor combustion
chamber redesign
t2 - Major combustion
chamber redesign
t3 - Fuel drainage control
t4 - Divided fuel supply
system
t5 - Water injection
t6 - Modify compressor air
t7 - Variable-geometry
combustion chamber
t8 - Staged injection
combustor
The assumption is made that emission rates for all
engines within a given class can be reduced to common,
optimum levels (on a lb/1000 Ib fuel basis) by minor
combustor modifications. These optimum emission rates
are based on the best performance reported for each
engine class, excluding extreme data points.
Estimates are based on reports of carbureting fuel
injector performance and reduction of smoke emission.
Concept is incorporated in some Class T3 engines.
Estimates are based on assumption that best emission
rate for Class Tl and T2 engines is at an exhaust
visibility threshold at maximum power. Carburetion
appears to reduce smoke level, and presumably particu-
late emissions, to approximately half that level. Addi-
tionally, premixing of air and fuel can be used to give
substantial NO., reduction by decreasing residence time
A.
in the combustor.
Estimate is based on the assumption that fuel drainage
can be completely eliminated by collecting drained fuel
and returning to fuel tank.
Control method results in combustion zone fuel-air ratio
similar to that at approach condition. Reduction in CO
and THC from idle to approach is approximately 90 per-
cent in Class Tl and T2 engines and 90 percent in
Class T3 engines. Effectiveness is reduced by one order
because combustor is not operating at "well-designed"
condition.
Water injection is assumed only at takeoff at a rate
up to twice the fuel rate. Water injection into
compressor or diffuser is assumed to be by system
similar to those in current use. Effectiveness based
upon published results with steam injection. Water
injection assumed to be of equal effectiveness when
injected upstream of combustor.
Assumptions are (1) fraction of air that can be bled is
small so that engine operating point is nearly unchanged,
(2) combustor f/a varies inversely with air bleed rate,
and (3) CO and THC emissions at idle vary as the (air
mass flow rate)3 and inversely as (f/a) . This
relationship is based upon data from Reference 14.
If maximum air bleed rate is 20 percent, CO and THC
emission rates are reduced by 50 percent.
Combustor primary zone is assumed to operate at a con-
stant f/a equal to normal f/a at approach power condition
(primary equivalence ratio = 0.6). CO and THC emissions
at idle are reduced to levels corresponding to approach
power, or by 90 percent for Classes Tl, T2, and T3. This
incorporates design characteristics that provide a good
mixture in the combustion zone. This feature and con-
stant f/a operation combine to reduce NOX emissions at
full power by 75 percent26 and particulate emissions by
50 percent at all power levels as in t2.
61
-------
Emission-control effectiveness is indicated in Tables
21, 22, and 23 for each control method and for each
pollutant for which a significant degree of control
expected. Pollutants for which little or no control
expected are not listed. Effectiveness is indicated
separately for each engine class. No specific estimates
have been made for control of reactive hydrocarbons, odor,
or aldehydes because control methods applicable to these
emissions are not yet identified. Reductions in these
emissions are expected along with reductions in THC
emissions. Any of the modifications defined for existing
turbine engines (tl through t6) could be combined to achieve
increased emission control effectiveness; exceptions are
modifications tl and t6, which are mutually exclusive.
Piston Engines - The control methods considered feasible for
aircraft piston engines are listed with brief descriptions
in Table 2U. These methods include most of the approaches
that have been developed for automotive engines for control
of carbon monoxide and total hydrocarbon. Methods for
controlling nitrogen oxide (NOx) emissions are not included
because the fuel-rich operating conditions of aircraft
piston engines result in low NOx emission rates. Piston
engine emission characteristics are included in Figure 11.
As this figure indicates, fuel-air ratio has a significant
effect on aircraft piston engine emissions. Plans for
changes in engine operating conditions to reduce CO and THC
emissions must also consider NOx to prevent significant
increases in emissions of this pollutant.
Table 2U lists nine piston-engine control methods,
including the use of direct-flame afterburners and water
injection, methods that are not being considered currently
for automotive engines. Afterburners might be used to
advantage in this application because they can utilize the
high-velocity airflow around the aircraft. Although
aircraft piston engines and automobile engines are
fundamentally similar, their applications are significantly
different, with different requirements. Reliability is of
primary importance in aircraft piston engine applications
and therefore is given paramount consideration in
identifying applicable control methods. The piston-engine
emission-control methods were identified and evaluated
through reviews of published investigations. Of the methods
identified, all are considered applicable to existing
engines except those that would reguire redesign of the
basic engine or its control systems.
Effectiveness estimates for piston engines are based on
reductions of current uncontrolled rates listed in Table 25.
62
-------
Table 24
Engine Modifications for Emission Control
for Existing and Future Piston Engines
Control method
Modification
Existing engines
pi - Fuel-air ratio
control
p2 - Simple air injection
p3 - Thermal reactors
p4 - Catalytic reactors
for HC and CO
control
p5 - Direct-flame
afterburner
p6 - Water injection
p7 - Positive crankcase
ventilation
p8 - Evaporative emission
controls
Future engines
p9 - Engine redesign
Limiting rich fuel-air ratios to only those
necessary for operational reliability.
Air injected at controlled rate into each engine
exhaust port.
Air injection thermal reactor installed in place of,
or downstream of, exhaust manifold.
Air injection catalytic reactor installed in exhaust
system. Operation with lead-free or low-lead fuel
required.
Thermal reactor with injection of air and additional
fuel installed in exhaust system.
Water injected into intake manifold with simultaneous
reduction in fuel rate to provide for cooler engine
operation at leaner fuel-air ratios.
Current PCV system used with automotive engines applied
to aircraft engines. Effective only in combination
with one of preceding control methods.
A group of control methods used singly or in combina-
tion to reduce evaporative losses from the fuel system.
Control methods commonly include charcoal absorbers and
vapor traps in combination with relatively complex
valving and fuel flow systems.
Coordinated redesign of combustion chamber geometry,
compression ratio, fuel distribution system, spark and
valve timing, fuel-air ratio, and cylinder wall temper-
ature to minimize emissions while maintaining opera-
tional reliability.
63
-------
FIGURE 11
PISTON ENGINE EMISSION CHARACTERISTICS
2
O
CO
O
•
CX,
00
w
0.7
0.6
0.5
.-> PC
§ i °-4
0>Lt, K
*• M
U ^^
M J3
SC 0.3
u
0.2
0.1
3
4-1
W)
JO
tn
C
O
•^
U)
tn
CU
TD
•r-(
X
O
C
O
C
O
.G
U
1600
1400
§ 1200
o
1000
800
600
400
200
BSFC
OJ
140 a
120
100
80
60
40
20
O
O
O
t/3
C
o
•1-1
U)
in
•H
E
X
O
3
•o
C
0
H
8:1
9:1
10:1
11:1
12:1
13:1
14:1
15:1
Air-Fuel Ratio
-------
TABLE 25
CURRENT UNCONTROLLED EMISSION RATES
FOR PISTON ENGINES29
(lb/1000 lb of fuel)
Pollutant
CO
THCa
NOX (as N02)
Idle
896
48
7
Taxi
882
76
4
Approach
918
80
4
Takeoff
849
18
6
Total hydrocarbon (THC) emission rates have been increased by 50% to
account for crankcase blow-by emissions. Evaporative emissions are
not included in these rates.
TABLE 26
EFFECTIVENESS OF ENGINE MODIFICATIONS IN
CONTROL OF EMISSIONS FROM PISTON ENGINES
BY POLLUTANT3
Controlled
Control Method CO
PI
P2
P3
P4
P5
P6
P7
P8
P9
Fuel-air ratio control
- Simple air injection
- Thermal reactor
- Catalytic reactor
(requires lead-free fuel)
- Direct-flame
afterburner
- Water injection
- Positive crankcase
ventilation (PCV)
- Evaporative emission
control
- Engine redesign
0.5
0.1
0.1
0.1
0.1
0.1
NC
NC
0.1
Emission Rate
THCb
0.5
0.5
0.25
0.25
0.1
0.25
d
e
0.5
a Emission rate is fraction of uncontrolled emission rate after installation
of control method and applies to all operating modes.
b Exhaust HC only.
c NC indicates no change.
d PCV would eliminate blow-by emissions when used in combination with pi,
p2, p3, p4, p5, or p8. Blow-by THC emission estimated to be equal to
30% of uncontrolled exhaust emission.
e Evaporative controls would reduce THC emissions due to evaporation from
fuel supply. Magnutude of uncontrolled emissions is inknown.
65
-------
Since emission rates from piston engines do not vary as
widely as those from turbine enqines, control effectiveness
can be based on average rates for existing engines. The
effectiveness estimates shown in Table 26 are based in most
cases on the application of individual control methods
without other engine changes. Method p7 (PCV) is an
exception; it is considered to be most effective in
combination with method pi, p2, p3, pU, p5, p6, or p9.
Piston-engine modifications p2 through p6 are designed
to serve the same function and, thus, are mutually
exclusive. All of the others could be combined with any of
the modifications p2 through p6 to achieve increased
emission-control effectiveness.
Cost and Time Requirements for Control-Method Development
and Implementation
Existing Enqines - Estimates of the cost and time
requirements of applying each control method applicable to
existing engines are preliminary and are intended to
indicate the magnitude of costs and time involved in
controlling emissions from all civil aircraft. Cost and
time requirements are estimated separately for control-
method development and implementation. Development includes
all effort required from initial stages through
certification of the control method for a specific engine
class and tooling for production. Implementation includes
initial installation of the control method on all engines of
a given class and costs associated with additional effort or
materials required for the control method throughout the
remaining service life of the engines. These estimates are
based on a turbine engine life of 10 years with engine
overhauls every 5,000 hours or 2 1/2 years and a piston
engine life of 10 years with engine overhauls every 5,000
hours or 5 years. Operating costs for water injection are
based upon experience with the water injection system on the
Boeing 717 aircraft.
Because few of the control methods have been developed
for or applied to aircraft engines, and because many factors
affect total implementation costs, many uncertainties are
involved in the estimates. Estimates of development costs
and time requirements are based on the previous experience
of aircraft engine manufacturers in similar modifications.
Estimates of implementation costs are considered to be less
certain than development costs. The cost and service life
of a modified engine component is difficult to predict
accurately. Yet these factors strongly affect the
cumulative costs of operating and maintaining the modified
66
-------
engine. Because implementation costs could be far greater
than development costs for some control methods, the
estimates of implementation costs are only indicative of
cost penalties that might be involved with control-method
implementation.
Three potential levels of aircraft emission control
entail three distinct associated cost levels: (1)
retrofitting in-use engines, (2) modifying present
production designs -to incorporate emission control
technology in new engines of models presently being
produced, and (3) incorporating emission control technology
into new engine designs during the design phases of a new
engine model.
Costs are highest for retrofitting in-use engines, are
significantly lower for modifying existing designs in new
production engines and are lowest for incorporating emission
technology during engine design. Table 27 presents
estimates of the development time, development costs, and
implementation costs for application of the control methods
that could be retrofit-ted on the current population of all
civil engines.
The development time requirements listed in Table 27 are
the periods required to reach the point where installation
of the control methods in existing engines could begin. The
application of controls in all existing engines would
require an additional time period that depends primarily on
the availability of engine maintenance facilities. The time
for implementation is estimated to be 2 1/2 years for
turbine engines and 5 years for piston engines. These time
estimates allow implementation of the emission control
method during normal maintenance procedures, minimizing
cost. Table 28 presents costs by category: air carrier,
general aviation, and civil aviation. These tables
represent cost to retrofit the various control methods to
the current population of aircraft.
From another perspective, implementation costs may be
expressed as fractions of total engine costs. For a typical
class T2 (turbine) engine, the cost of installing and
maintaining control systems ranges from $300 to $69,900,
assuming a 10-year engine life. Based on a total engine
cost of $250,000, these control-method implementation costs
represent 0.1 to 25 percent of the total engine cost. For a
typical piston engine, estimated control-method
implementation costs range from $100 to $1,000, also based
upon a 10-year engine life. For a total engine cost of
67
-------
Table 27
Time and Costs for Modification of Current
Civil Aviation3 Engines
Control method
Turbine engines
Minor combustion
chamber redesign
Major combustion
chamber redesign
Fuel drainage control
Divided fuel supply
Water injection
Compressor air bleed
Piston engines
Simple air injection
Thermal reactor
Catalytic reactor
Direct-flame
afterburner
Water injection
Positive crankcase
ventilation
Evaporative emission
control
Development
time ,
years
2.5 to 5
2.5 to 7.5
1 to 2.5
5 to 7.5
2.5 to 4
4 to 6.5
1.5 to 3
3 to 6
2.5 to 5
3 to 6
1.5 to 3
2 to 4
1.5 to 2.5
Development
cost,
10b dollars
37
74
1.5
84
25
90
9
25
22
25
9
4
4
Implementation
cost,
10° dollars
383
665
5.4
102
175
58
165
424
535
424
400
94
269
"Civil aviation" includes air carrier and general aviation engines
68
-------
Table 28
Cost Results for Turbine Engine Population
by Separate Use Categories
Engine
class
Tl
Tl
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T2
T2
T3
T3
T3
T3
T3
T3
i
Control
method
tl
t2
t3
t4
t5
t6
tl
t2
t3
t4
t5
t6
tl
t2
*- O
t4
t5
t6
i
Cost
scaling
factor
0.35
0.35
--
0.35
0.35
0.35
1.00
1.00
--
1.00
1.00
1.00
1.64
1.64
1 C. 1.
1.64
1.64
1.64
|
Development ]
cost per
engine family,
106 dollars
0.90
1.80
0.05
1.80
0.62
2.20
0.90
1.80
0.05
1.80
0.62
2.20
0.90
1.80
0.05
1.80
0.62
2.20
Implementa-
tion cost
per engine,
103 dollars
12.4
21.3
0.1
3.7
5.5
2.1
35.5
69.9
0.3
10.5
15.6
6.0
58.3
100.0
n c.
17.2
25.6
9.9
Total
Air
carrier
19.2
34.5
0.4
14.9
9.8
15.5
243.0
^418.0
2.0
87.0
108.7
61.5
50.0
95.0
2.0
13.7
29.5
16.0
cost, 106 dollars
General
aviation
90.5
159.3
1.0
51.5
43.6
48.1
17.8
31.0
--
8.3
8.2
7.1
--
--
..
--
--
--
Civil
aviation3
109.7
193.8
1.4
66.4
53.4
63.6
259.8
449.6
2.0
95.3
116.9
68.6
50.0
95.0
o n
13.7
29.5
16.0
a"Civil aviation" includes air carrier and general aviation engines
69
-------
$6,000, these implementation costs represent 2 to 65 percent
of the total.
Retrofit cost and time estimates for turbine engines
were developed by using the application of low-smoke
combustors to the JT8D engine class as a reference for cases
in which no direct experience was available. Cost and time
requirements for this modification, which is considered a
minor combustor redesign for a class T2 engine, were
estimated in detail in 1969.27 Requirements for other
control methods were determined essentially by proportioning
the cost and time expenditures according to the complexity
of the method, with respect to the reference case.
Requirements for other engine classes were determined by
using appropriate scaling factors and by again using the
JT8D modifications as reference. Time and cost estimates
for piston engines are based largely on experience to date
with emission controls for automobile engines. Significant
differences, such as certification and safety requirements
and production levels, were considered in scaling the costs
from the experience with automobiles.
Costs of emission control technology are substantially
lower when applied to new engines only. These costs are
less than one-half the retrofit costs on a per-engine basis.
These estimates cannot be totalled as were the retrofit
estimates because of uncertainty concerning the number of
engines that would be affected.
Future Engines - Cost estimates have been developed also for
incorporation of emission controls in future engines, that
is, engines that have not yet been developed. These
estimates are defined only as fractions of total engine
cost, since no reasonable basis is available for estimating
the numbers of engines that would be affected.
Emission control in turbine engines that is attained
through the use of advanced combustor-design concepts is
estimated to represent an increase in total engine cost of 3
to 1 percent. Emission control in piston engines that is
achieved by engine-design modifications would not
necessarily result in any significant increase in engine
cost. If greater control of emissions is required than can
be achieved by engine design modifications, however, one or
more of the control methods applicable to existing engines
will be necessary. The costs of these control methods,
which involve the addition of auxiliary devices such as
thermal reactors, will be significant, probably in the range
of 5 to 10 percent of total engine cost.
70
-------
These estimates represent the increased costs of new
engines with emission controls installed. Additional
continuing costs may accrue for maintenance of the controls.
These maintenance costs will be considerably less than those
entailed in modifications of existing engines.
EMISSION CONTROL BY MODIFICATION OF GROUND OPERATIONS
Definition of Ground Operations
The cycle of operations performed by an aircraft during
its arrival at and departure from an airport can be defined
quite precisely because most of these operations are
prescribed by airport or aircraft operating procedures.
Characteristic operating or LTO (landing-takeoff) cycles
have been defined for various classes of aircraft for
purposes of estimating pollutant emissions.
The LTO cycle can be separated logically into flight and
ground operations. Flight operations include the approach
and climb-out modes as well as landing and takeoff, even
though the latter occur partially on the ground. Ground
operations include the taxi and idle modes of the cycle.
This separation is logical for two reasons. First, flight
operations as defined here are those that cannot readily be
modified to reduce pollutant emissions. Second, flight
operations are conducted almost entirely with aircraft
engines at full or part power; under these conditions,
pollutant emission rates are quite different from those at
the low power levels characteristic of ground operations.
Aircraft ground operations contribute substantially to the
concentrations of CO and THC at air carrier airports because
of the relatively high emission rates of these pollutants at
low engine power levels, and because ground operations are
largely confined to limited areas within the airport
boundaries.
Fjnission Control Methods
Six methods offer some degree of control of CO and THC
emissions at air carrier airports by modification of
turbine-aircraft ground-operation procedures.
(1) Increase engine speed during idle and taxi
operations.
(2) Increase engine speed and reduce number of
engines operating during idle and taxi.
71
-------
(3) Reduce idle operating time by controlling
departure times from gates.
Reduce taxi operating time by transporting
passengers to aircraft.
(5) Reduce taxi operating time by towing aircraft
between runway and gate.
(6) Reduce operating time of aircraft auxiliary power
supply by providing ground-based power supply.
The first two methods reduce emissions by requiring that
engines be operated at more efficient power settings than
those in current practice (Figure 12); the next four methods
reduce emissions by reducing operating time of either main
or auxiliary engines. The effectiveness of these methods in
reducing emissions varies considerably. Table 29 summarizes
the reductions in CO and THC emissions that would result at
Los Angeles International Airport from the six suggested
ground-operation changes. Tables developed for other major
air carrier airports show emission reductions of the same
magnitude.
The control methods listed, with the possible exception
of number 3, are not applicable to small, piston-engine
aircraft, and, therefore, do not seem to offer means for
controlling emissions at general aviation airports. Periods
of delay at take-off are significant at some general
aviation airports; however, aircraft ground traffic at
general aviation airports may not be sufficiently controlled
to allow an effective system of controlled gate departures
or engine start-ups to reduce periods of delay.
Implementation Cost and Time Requirements
The cost and time requirements of the contrcl methods
involving ground operation modifications have been estimated
for Los Angeles International. Table 30 presents summary of
the estimates. Implementation of these methods at other
airports would involve costs of the same magnitude.
Specific costs, however, would vary with airport activity
level and the present availability of auxiliary equipment.
FAA and the airlines have estimated savings for control
method 2, and their estimates are within 2OX of the estimate
in Table 30.
Tables 29 and 30 indicate that alternative 2 is the most
attractive means of reducing turbine aircraft emissions
72
-------
Normal Taxi-idle
120
o
JE
cu
CL
Hi
c
•1-1
60
C
-------
Table 29
Comparative Reductions Resulting from Control
Methods Applied at Los Angeles International Airport
1.
2.
3.
4.
5.
6.
i
Control method
Increase engine idle speed
Increase idle speed and use minimal
engines for taxi
Two engines
Single engine
Eliminate delays at gate and runway
Transport passengers between
terminal and aircraft
Tow aircraft to avoid taxi emissions
Avoid use of aircraft auxiliary
power units (APU)
Resultant emissions,
70 of uncontrolled
emissions
CO
71
53
39
90
98
34
96
Hydrocarbons
93
66
51
91
97
42
98.5
74
-------
Table 30
Costs and Time for Operations Changes
at Los Angeles International Airport
Control method
1.
2.
3.
4.
5.
6.
Increase engine speed
Increase speed, reduce
number
Control gate departure
Transport passengers
Tow aircraft
Reduce APU operation
Time,
years
0
0.3
5
2.5
1
0.5
Initial cost,
106 dollars
0
0
15
65
1.2
1.3
Annual operating
cost change,3
106 dollars
8.5
-0.7
-0.4
5.0
0.4
1.5
sign indicates an estimated savings
75
-------
providing that operational and safety requirements can be
met.
COMPARATIVE EVALUATION OF EMISSION CONTROL METHODS
The engine and ground operation modifications just
discussed can be compared in terms of effectiveness, cost,
and implementation time. A "potential benefit factor" has
been defined to allow comparison of cost/benefit of the
emission control methods. The potential benefit factor
(PBF) is the net emission reduction resulting from a
particular control strategy, averaged over the next 20
years, divided by the cost.
PBF = FYE x CE x ECF
CP
where FYE is the fraction of the next 20 years that the
control method is effective; CE is the control method
effectiveness (the percentage reduction of a particulate
pollutant); ECF is the emission contribution fraction
(percentage of total aircraft emissions at relevant airports
contributed by engines affected by this control strategy);
and CP is the cost of the control strategy for the pollutant
considered. Emissions at major carrier airports were used
to determine effectiveness of turbine engine control methods
and those at general aviation airports to determine
effectiveness of piston engine emission control methods.
The potential benefit factor is a measure of the cost-
effectiveness of each control strategy. Potential benefit
factors (Table 31) have been calculated for the control
strategies previously described as applied to (1)
retrofitting in-use aircraft, (2) modifying new engines of
present models, and (3) incorporating control methods in new
engine designs. The higher numbers represent the most cost-
effective strategies for emission reduction.
The potential benefit factors in Table 31 are a
composite for all turbine and piston engines. Although
these factors indicate the relative merits of the control
methods, the factor for an individual engine classification
may be significantly different. For example, retrofit of
water injection for class T3 shows a potential benefit
factor of U.2, whereas the average for all turbine engines
is only 1.1. Additionally, while some control strategies
show a high potential benefit number, other strategies must
also be used to achieve significant emission reductions.
For example, fuel venting represents from U to 20% of total
hydrocarbon emissions, dependent upon airport considered.
76
-------
Table 31
Comparison of Emission Control Methods
Control Method
Turbine Engines
A. Retrofit-Engine Modifications
1. Minor combustion chamber redesign
(APU)
2. Major combustion chamber redesign
(T3 and APU)
(T2 only)
3. Fuel drainage control
(T2 and T3 only)
4. Divided fuel supply
5. Water injection
(T3 only)
6. Compressor air bleed
B. New Production Engine Modification
1. Minor combustion chamber redesign
2. Major combustion chamber redesign
3. Fuel drainage control
4. Divided fuel supply
5. Water injection
(T3 only)
6. Compressor air bleed
C. Future Engine Emission Control
1. Fuel drainage control
2. Divided fuel supply
3. Water injection
(T3 only)
4. Compressor air bleed
5. Variable geometry combustion chamber
6. Staged injection combustor
D. Ground Operations Modification
1. Increase engine idle speed
2. Increase speed, reduce number
3. Eliminate delays
4. Transport passengers
5. Tow aircraft
6. Reduce APU operation
Piston Engine
A. Retrofit-Engine Modification
1. Fuel-air ratio control
2. Air injection
3. Thermal reactor
Potential Benefit Factor
HC & CO
0.37
(2.5)
0.3
10
(20)
1.5
--
1.3
5.0
4.6
30
5.0
--
4.0
30
15
--
15
25
25
2.4
105
10
0.1
75
1.0
50
5
2
NOX
0.37
1.1
(6.6)
--
--
1.4
(4.2)
--
5.0
4.6
--
--
1.4
(4.2)
--
--
--
2.0
(5.6)
--
25
25
--
--
--
--
--
--
--
--
--
Smoke
0.37
1.1
(5.0)
--
--
--
--
5.0
4.6
--
--
--
--
--
--
--
--
25
25
--
--
--
--
--
--
--
--
~~
77
-------
Table 31 (Cont.)
Comparison of Emission Control Methods
Control Method
B.
C.
D.
4.
5.
6.
7.
8.
Catalytic reactor
Direct-flame afterburner
Water injection
Positive crankcase ventilation
Evaporative emission control
New Production Engine Modifications
1.
2.
3.
4.
5.
6.
7.
8.
Fuel-air ratio control
Air injection
Thermal reactor
Catalytic reactor
Direct-flame afterburner
Water injection
Positive crankcase ventilation
Evaporative emission control
Future Engines
1.
2.
3.
4.
5.
6.
7.
8.
9.
Fuel-air ratio control
Air injection
Thermal reactor
Catalytic reactor
Direct-flame afterburner
Water injection
Positive crankcase ventilation
Evaporative emission control
Engine redesign
Ground Operations Modifications
1.
Eliminate delays
Potential Benefit Factor
HC
1
1
2
3
1
500
30
6
5
3
15
50
3
500
30
6
5
3
15
50
6
25
10
& CO
.5
.5
.6
.0
.3
.0
.6
.0
.3
.0
NOX
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
—
*" —
Smoke
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
—
"
78
-------
Consequently, to achieve substantial reduction cf
hydrocarbon emissions a less attractive control method is
necessary in addition to eliminatinq fuel venting.
A review of the PBF values in Table 31 supports the
following conclusions providing that all operational and
safety requirements can be met:
(1) Modification 2 for ground operation procedures is
the most cost-effective method of reducing hydrocarbon and
carbon monoxide emissions from turbine engines,
(2) Incorporating emission control methods into
design of new engines is the most cost-effective method of
over-all aircraft emission control.
(3) Control of fuel-air ratio is the most cost-
effective method of reducing hydrocarbon and carbon monoxide
emissions from piston engines.
(U) Retrofits of class T3 turbines is a more cost-
effective method for NOx control compared to retrofit of
other turbine engine classes.
(5) Fuel drainage control has high PBF because of
extremely low cost of implementation (CP) rather than high
control effectiveness (CE).
Because cost-effectiveness varies significantly among
engine classes and control strategies, several factors in
addition to cost and effectiveness must be considered in
developing emission control strategies for aircraft engines.
EMISSION MEASUREMENT TECHNOLOGY
Reliable methods for measuring the rates at which
pollutants are emitted from aircraft engines are required
for the support of an emission-control program. Emission
measurements are required for evaluating the effectiveness
of control methods, and specific measurement methods must be
incorporated in emission-control standards.
The state of emission-measurement technology has been
assessed to determine whether measurement techniques are
sufficiently well advanced to support the development of
emission-control methods and the implementation of emission
standards for aircraft engines. The conclusion drawn from
this assessment is that current measurement technology will
meet the requirements of an emission-control program.
Although measurement techniques for particulate emissions
79
-------
are inadequate at present, improved techniques are being
developed throuqh cooperative government-industry action.
Measurement of emission rates from an aircraft engine
involves three major requirements:
(1) A test procedure specifying engine operating
conditions.
(2) A sampling technique for obtaining a
representative sample of exhaust gas.
(3) Analytical instrumentation for determining
pollutant concentrations in the exhaust-gas sample.
Aircraft engine manufacturers, FAA, and EPA are devoting
substantial effort toward meeting these requirements for
measuring emissions from turbine engines.
Sampling and Test Procedures
Obtaining a representative sample of exhaust gas from an
aircraft engine for analysis of emission rates is a complex
and difficult procedure. Sampling emissions from turbine
engines is difficult at the outset because of the jet-blast
environment in which the sampling equipment must be
installed. Beyond this problem, the following factors all
significantly affect the composition of the exhaust sample:
(1) Engine power level.
(2) Temporal and spatial variations in exhaust
composition.
(3) Sampling-line diameter, length, material, and
temperature.
(*») Ambient temperature and humidity.
(5) Ambient pollutant levels.
Procedures for sampling and analyzing turbine-engine
exhaust gases have been under development for several years
by engine manufacturers, FAA, and EPA. More recently, the
Society of Automotive Engineers Aircraft Exhaust Emission
Measurement (E-31) Committee has been formed to standardize
these procedures. Standardization of measurement techniques
will minimize variations resulting from the factors listed
above; however, the several sources of error in collecting
exhaust samples and the variability of samples among
80
-------
different engines must be considered in the establishment of
a standard emission measurement procedure.
Sampling reguirements for aircraft piston engines are
similar to those for automobile engines. The exhaust gases
are well mixed by the time they reach the exhaust stack
exit. Conseguently, no factors are apparent, beyond those
already recognized as affecting automobile exhaust
emissions, that would cause variability in exhaust samples
from aircraft piston engines. Differences in engine
operation, however, must be considered in the establishment
of a standard emission measurement procedure.
Emissions Measurement Instrumentation
Measuring the concentrations of most gaseous pollutants
in exhaust samples from aircraft engines is generally within
the capabilities of existing instruments and should remain
so, even when engines are modified to reduce emission rates.
The various types of instruments that are available and
in current use for aircraft emission measurement have been
reviewed. Instruments that appear to be most suitable for
measuring turbine-engine emissions at the present time are
presented in Table 32.
81
-------
Table 32
Instrumentation for Measurement
of Turbine Engine Emissions
Measurement method
Ntm-dispersive infrared (NDIR)'
Heated flame ionization
Chemiluminescenee
Chemiluminescence3
SAE smokemeter (ARP1179)
None
Determined from fuel analysis
3-MBTH
Human odor panel
Pollutant class
CO and CC>2
THC
NO
NO 2
Smoke
Particulates
so2
Aldehydes
Odor
aThe non-dispersive ultraviolet instrument (NDUV)
may also prove acceptable for N0~ measurement
82
-------
APPENDIX A:
ANALYSIS OF CARBON MONOXIDE CONCENTRATION
AT LOS ANGELES INTERNATIONAL AIRPORT
When continuous air quality monitoring data is available,
statistical analysis may be applied to determine frequencies
of occurrence of any concentration for any averaging time
either by interpolation of the data or by extrapolation if
the available data is limited. It has been observed that
all air quality data regardless of averaging time follows a
log normal distribution.*3
The continuous carbon monoxide data taken at LAX during six
months in 1970 were analyzed statistically for 1-hour and 8-
hour averaging times at several sites to determine the
expected frequencies when the NAAQS would be exceeded. With
the use of the simple rollback technique, adjusted
frequencies could be determined for changes in emissions and
various control strategies for aircraft and non-aircraft
emission sources. Dispersion modeling results were used to
predict the degree of influence aircraft emissions have in
locations beyond the boundaries of Los Angeles Airport.
The analysis focused on the 8-hour exposure case in areas
adjacent to the airport where it would be expected that
people would meet the exposure time criteria either as
residents or business employees. The 1-hour exposure case
would apply to the terminal area itself as well as the areas
considered in the 8-hour averaging time case.
Corrections were made to the available ambient data because
of the recognized seasonal variation of carbon monoxide
levels in the Los Angeles basin. A recent report published
by the LAAPCD contained sufficient data to calculate the
summer-winter correction factors for the hourly and 8-hour
averaging times. The average correction factors for the
basin to convert August-September data to December-January
data were found to be 1.5 for the 1-hour data and 1.9 for
the 8-hour case.
Data and statistical information on carbon monoxide analysis
presented in a paper by Larsen31 were also utilized in this
phase of the analysis. The L. A. basin CO data in the
Larsen paper were used to check the LAX data for consistency
83
-------
in terms of the frequency and range of observed carbon
monoxide levels. Tabulated and plotted data in this
reference indicate the air pollution hot spot represented by
the Los Angeles Airport and its environs. Figure A-l, taken
from the reference shows this point quite clearly. Figure 1
in the main text of this report indicates the location of
the continuous ambient carbon monoxide stations. Station
209 was chosen as representative of an off airport site for
the 8 and 1-hour analysis. Figure A-2 shows the plot of the
raw station 209 data for the months of August and September.
It is obvious that station 209 is directly influenced by the
airport only when the wind is blowing from a westerly
direction. The September data were categorized into East or
West influences and the results are plotted on Figure A-3.
It can be seen that the composite plot is representative of
both these subcategories and therefore was used for all
subsequent analysis. It further demonstrates that the
airport exerts the same impact on the air quality at station
209 as the non-airport area sources surrounding it. Figure
2, in the text of the report, shows the August station 209
frequency distributions for maximum 8-hour daily averages
adjusted for the summer-winter correction factor. The
frequency of occurrence relating to one day per quarter is
assumed to be equivalent to the one day per year frequency
associated with the 8-hour NAAQS because it can be assumed
that the worst exposure case would occur during the winter
quarter of the year. This plot has then been ad-justed
(Figures A-4 and A-5) for expected rollback emission
reductions of non-aircraft sources in combination with
various percent contributions due to due to aircraft sources
and assumed levels of aircraft emission controls. Similar
methodology was used in estimating expected 1980 CO
concentrations with various aircraft contributicns. These
are given in the main text. Modeling results were used to
determine the relating distribution and magnitude of
aircraft emissions around LAX. It can be seen that the
station 209 analysis is quite representative of other areas
adjacent to LAX where adverse influences of aircraft
operations can be expected to occur.
The same procedures were followed in plotting the adjusted
September data to determine the frequency with which the
standard would be expected to be exceeded for various
percent aircraft contributions. This data would represent
the upper limits of the analysis.
Similar frequency analysis can be performed for the 1-hour
exposure case. However, unless there is extreme variation
between the slopes (or standard geometric deviations) of the
84
-------
FIGURE A-l.
MAXIMUM ANNUAL 8-HOUR-AVERAGING-TIME CONCENTRATION OF
CARBON MONOXIDE EXPECTED AT VARIOUS SITES IN THE LOS ANGELES AREA.
\ LOS ANGELES COUNTY
\
\
\
\
I.
\ *
30
\ SAN FERNANDO
—' VALLEY / f
\ i° *° / l'8'3
-' • l»37 /««f / .32 V •
* | ^BURBANK A28 X^
HOLLYWOOD /37 / PASADENA
l.r^I • *-"*
fTf'j*™ "'I a "^^^ • -^
HOLLYWOOD /37 / PASADENA "" • r*
4V.37* 38* •/DOWNTOWN P
^5 ,VV'hs « lx rj
J.^ffi^f".,. /.„ --^
Nn Wa^4< r DISNEYLAND ^^x-
0 5 10
miUf
22
DISNEYLAND
23
SANTA ANAV
12* AIRPORT
85
-------
50
FIGURE A-?
BASELINE DATA, DAILY MAXIMUM 8-HR. AVERAGE
CO CONCENTRATIONS, STATION 209, LAX, 1970
a
a
c
o
•H
c
0)
O
c
o
o
o
o
M
3
O
20
10
2 •
September Data
August Data
90 80 50 20 10
Probability (%) of Exceeding the Given Pollutant Level
« t
0.1
-------
FIGURE A-3
FREQUENCY DISTRIBUTION FOR 8-HR. CO DATA', STATION 209, LAX, SEPTEMBER 1970
00
o.
o.
H
z
u
u
z
o
u
I
00
60 T
40 -
20 '
10 ••
Key
o •- easterly wind influence.
A -- westerly wind influence.
—#-
95
90 80 50 20
Probability (%) of exceeding the given pollutant level.
10
0.1
-------
FIGURE A-4
00
00
E
a
a
c
o
•l-l
4-1
C
Q)
O
c
o
o
o
u
(-1
3
O
I
oo
EXPECTED CO CONCENTRATION DISTRIBUTION, WINTER, STATION 209, LAX
FOR 80 PERCENT AIRCRAFT CONTRIBUTION
40 r
20
10
99
39 days/year
Ambient AQ Standard, 9 ppm
90 70 50 30 10
Probability (%) of exceeding given pollutant level
-------
FIGURE A-5
EXPECTED CO DISTRIBUTION, WINTER, STATION 209, LAX
FOR 20 PERCENT AIRCRAFT CONTRIBUTION
40
00
E
a
ex
c
o
C
0)
o
o
CJ
o
o
t-l
3
O
oo
20
10
8
Ambient AQ Standard, 9 ppm
99
.1.
JL
90 70 50 30 10 1
Probability (%) of exceeding the given pollutant level
-------
1-hour data and -the 8-hour averaging time data, the 1-hour
standard will be met if the strategies are imposed to meet
the 8-hour standard. This wculd appear to be the case in
those areas at LAX where the 1-hour GO levels are higher
than the standard at the present time.
90
-------
APPENDIX B:
DISPERSION MODELING METHODOLOGY AND
ISOPLETH DERIVATION
The primary and most direct method of estimating
aircraft contributions to air pollutant concentrations
involved the application of frequently used dispersion
modeling procedures to estimate air pollutant concentrations
caused by aircraft alone and by all sources located in the
airport vicinity (within a 10-kilometer radius of the
airport center). Dispersion models similar to the one used
in this study are specified by EPA as one means of showing
that implementation plans for certain regions will be
adequate to meet the ambient air quality standards. Much of
the analysis of aircraft air quality impact presented in
this report is based on modeling work performed, under EPA
contract, by Northern Research and Engineering Corporation.
A general description of the modeling procedure is presented
here; a more detailed account of the modeling work and
results is available in the contract report.'
The procedure in the modeling study involved: (1)
approximating emission sources as continuous, stationary
point sources of constant strength over the time period
being considered, (2) modeling the dispersion of pollutants
from these sources using an empirical mathematical model,
and (3) estimating concentrations at specified receptor
points by summing the pollutant contributions from each
point source, and (U) constructing isopleths of estimated
pollutant concentrations based on the estimated receptor
point concentrations.
The point sources used in the modeling approximated the
location and strength of emission sources at each of the
four airports studied. Lines along which automobile or
aircraft movement occur were represented by series of point
sources. Area sources, representing airport surroundings
out to a 10-kilometer radius from the airport center, were
represented by circular arrangements of point sources around
the airports. Altogether, 1U9 to 276 point sources were
used for each air carrier airport, depending on the size and
complexity of the airport. The number of sources was chosen
to provide a reasonable approximation of emissions at the
91
-------
airport and in the vicinity without need for excessive
computer time or computer program complexity.
The basis of the atmospheric dispersion modeling is an
empirical, mathematical approximation of pollutant
dispersion after emission from a point source. This
approximation yields a plume whose concentration
distribution is Gaussian in the vertical and crosswind
direction. The distribution is dependent upon downwind
distance from the source and on atmospheric stability.
Eventually the upper boundary of the atmospheric mixing
layer restricts vertical spread of the plume and modifies
the distribution of pollutants in the vertical direction.
This dispersion model should be considered as a general
approximation of airport dispersion patterns; considerable
model development would be required to include more detailed
small-scale dispersion patterns, such as those around large
buildings or near jet blasts.
In calculation of long-term concentrations, the fact
that there is a distribution of meteorological conditions is
used to simplify the basic dispersion model. The result,
known as the Martin-Tikvart model, approximates plume spread
in the crosswind direction and sums the contributions of all
combinations of wind speeds and atmospheric stabiltities.
The concentration at any receptor point is obtained as
the sum of the contributions from each point source of
emissions. The accuracy of the concentration value for this
type of model is dependent upon the proximity of the
receptor point and the emission sources. Because the
sources of emission are actually a collection of points,
lines areas, and volumes, rather than merely a collection of
points, as assumed in the model, greater accuracy generally
results when the receptor point is not close proximity to
any sources. To limit inaccuracies attributable to the
point source, receptor locations within 100 meters of a
point source were not considered in the results.
The model provided estimates of air pollutant
concentrations both from aircraft alone and from all sources
at a number of sites located in and around the selected
airports. Receptors considered in this study were located
according to the following overall scheme at air carrier
airports: (1) one receptor at the center of each major
terminal, (2) one receptor 100 meters from the head of each
runaway, (3) sixteen receptors on the airport boundary,
spaced equally on a compass rose located at the designated
center of the airport, and (4) sixteen more receptors
located in the airport surroundings, 5 kilometers from the
92
-------
center of the airport and spaced equally on the compass
rose. Not more than 50 receptors were used, the actual
number depending on the number of terminals and runways at
each airport.
The resulting concentrations at the various receptor points
were used in constructing isopleths of pollutant
concentration. Isopleths were constructed for 6-9 a.m.
hydrocarbon and annual NOx concentrations due tc aircraft
alone, and for aircraft contributions to total CO
concentrations.
The model input data used in calculating annual
concentrations of NOx were based on yearly distributions of
wind direction, stability class and wind speed class, and
annual average values of mixing height and emission rates.
The short-term meteorological and activity conditions used
to calculate the 8-hour and 1-hour CO conditions and the 6-9
a.m. hydrocarbon concentration were chosen to be
representative of conditions that would be expected to yield
high concentrations of these pollutants, i.e., low wind
speed, high atmospheric stability, and low mixing height,
and moderate to high aircraft activity. The conditions for
calculation of short-term concentrations are presented in
Table B-l.
Because the results of the model have not been
extensively validated or verified, the concentratidns
generated by the model should be considered to be very
approximate. They are useful, however, in indicating
general pollutant concentration levels of the extent of
aircraft contributions to localized pollutant concentration.
93
-------
TABLE B-l
SHORT-TERM METEOROLOGICAL AND ACTIVITY CONDITIONS
6-9 A.M. HC
8-Hour CO
at L.A. Airport at L.A. Airport
LAX
1-Hour CO
ORD JFK DCA
Wind speed class
Stability class (Turner)
Wind direction, deg.
Wind variability, deg .
Mixing height, m.
Aircraft activity, 60
LTO cycles. 79
Direction of movement
1
C
255
20
200
(1970)
(1980)
West
1
E
255
20
200
260
West
1
E
90
40
535
54
E
1
F
215
30
700
49
SW
1
E
200
10
960
30
S
1
E
320
20
980
34
N
Idle time at runway,
sec.
60
Estimated annual
frequency of occurrence
of meteorological con-
itions at least
once
150
240
260
540
81
29*
10
300
67
a These conditions are used in estimating ratios between aircraft generated and total
8-hour CO concentrations; the ratios are not sensitive to the conditions assumed.
b Based on 5 months of data.
94
-------
APPENDIX C:
AREA - SOURCE DISPERSION MODELING TO ESTIMATE
DOWNWIND POLLUTANT CONCENTRATIONS
The modeling method used in this analysis involved
approximating emissions both at airports and in surrounding
areas as area sources, and relating these emissions to
downwind pollutant concentrations by assuming Gaussian
pollutant distribution in the vertical and crosswind
directions. For each receptor point, the concentration
caused by small-area elements was determined by integrating
in the crosswind and upwind directions over each source
region. The airport and surroundings were considered as
separate source regions. The concentrations due to these
two source regions were calculated separately then added
together to obtain the total concentration at each receptor.
Near the airport source, concentrations are the same as
those from an area source of infinite extent.32 At greater
distances, edge effects caused by the finite width of the
airport are considered by including the integration in the
cross-wind direction. Also included is the limit to
vertical mixing imposed by a more stable layer aloft.
For the purpose of this modeling, the airport was
assumed to cover an area of 3.2 by 3.2 kilometers. The time
period for the analysis, 8 a.m. to 11 a.m., was selected on
the basis of recurring meteorological conditions conducive
to high air pollutant concentrations. A diurnal correction
factor was applied to the resulting concentrations to
correct for the disproportionately greater amount of
activity that occurred during this 3-hour period than
occurred during other 3-hour periods during the day. The
specific meteorological conditions used for the time period
considered were: wind from west; stability class = 3, wind
speed = 1.5 in/second mixing height = 200 m. These
conditions are representative of severe conditions, from an
air pollution standpoint, that are expected to cccur at
least once a year in the Los Angeles area.
95
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99
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