Report No. II68-1
ASSESSMENT OF AIRCRAFT
EMISSION CONTROL TECHNOLOGY
Northern Research iiiid Engineering Corporation
e, Massachusetts London, England
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Copy No. 218
Report No. 1168-1
ASSESSMENT OF AIRCRAFT
EMISSION CONTROL TECHNOLOGY
by
E. K. Bastress, R. C. Baker, C. F. Robertson,
R. D. Siegel, and G. E. Smith
Prepared for the
Office of Air Programs
Environmental Protection Agency
(Contract No. 68-0^-0011)
NORTHERN RESEARCH AND ENGINEERING CORPORATION
219 Vassar Street
Cambridge, Massachusetts 02139
September, 1971
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This work was carried out under the direct ion.of Dr. D. M. Dix
with Dr. E. K. Bastress assuming project responsibility. Other principal
participants in this program were Dr. R. C. Baker, C. F. Robertson,
Dr. R. D. Siegel, and G. E. Smith.
The Project Officer for this program was Mr. Charles Gray, Jr.,
of the Division of Emission Control Technology, Mobile Sources Pollution
Control Program, Office of Air Programs* Environmental Protection Agency.
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ACKNOWLEDGEMENTS
Portions of the information used in this program were provided
by the following organizations:
Aircraft Engine Group
General Electric Company
Pratt & Whitney Aircraft Division
United Aircraft Corporation
Avco-Lycoming Division
AVCO Corporation
American Air!ines
Massachusetts Port Authority
Transportation Systems Center
U. S. Department of Transportation
Bureau of Mines
U. S. Department of Interior
Federal Aviation Administration
U. S. Department of Transportation
U. S. Department of Defense
Aero Propulsion Laboratory
U. S. Air Force
Rolls-Royce (1971) Ltd.
Silent Hoist and Crane Company
AiResearch Manufacturing Company
Beckman Instruments, Inc.
Lockheed-California Company
Lewis Research Center
National Aeronautics and Space Administration
Naval Air Propulsion Test Center
U. S. Navy
Southwest Research Institute
Continental Motors Division
Teledyne Corporation
Engelhard Industries Division
Engelhard Minerals and Chemicals Corporation
Van Dusen Aircraft Supplies, Inc.
Curtiss-Wright Corporation
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TABLE OF CONTENTS
INTRODUCTION .....". 1
Background 1
Objectives . . . . 2
Methodology k
Pollutants Considered 6
Report Contents 7
SUMMARY OF RESULTS 8
Emission Control by Engine Modification . 8
Emission Control by Ground Operations Modifications. ... 14
Emission Measurement Technology 16
CONCLUSIONS 19
AIRCRAFT ENGINE CLASSIFICATION 22
Engine Population 22
Engine Classification 23
EFFECTIVENESS OF CONTROL METHODS: ENGINE AND FUEL MODIFICATIONS . . 25
Introduction ....... 25
Control Methods 25
Control Method Effectiveness 35
IMPLEMENTATION COSTS AND TIMES OF CONTROL METHODS:
ENGINE MODIFICATIONS 38
Engine Classification and Control Method Definition. ... 38
Cost and Time Analysis Procedures 39
"Development" Cost and Time Analysis 40
Implementation (Retrofitting) Cost and Time Analysis ... 42
Total Development and Implementation Cost • •
and Time Analysis 45
Final Cost and Time Results for Current
Engines in Service 47
Total Implementation Cost/Engine for
. "Production" Engines 48
Control Methods Applicable to Future Engines 48
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EFFECTIVENESS OF CONTROL METHODS: GROUND OPERATIONS
MODIFICATIONS 5**
Introduction 54
Control Method Effectiveness 5*t
Conclusions 60
IMPLEMENTATION COSTS AND TIMES OF CONTROL METHODS:
GROUND OPERATIONS MODIFICATIONS 61
Basis for Estimates 61
Discussion of Results 6k
EMISSIONS MEASUREMENT 72
Introduction 72
Test Procedures 73
Exhaust Sampling Techniques 73
Instrumentation 76
Recommendations 78
REFERENCES 81
TABLES 90
FIGURES 15^
APPENDIX - INSTRUMENTATION 172
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LIST OF TABLES
Table 1:
Table 2:
Table 3A:
Table 3B:
Table k:
Table 5A:
Table SB:
Table 6:
Table 7:
Table 8:
Table 9:
Table 10:
Table 11:
Table 12A:
Table 12B:
Table 12C:
Table 12D:
Table 12E:
Table 12F:
Table 12G:
Table 13:
Aircraft Classification System .... 91
Turbine Engines in the U. S. Air Carrier
Fleet (January, 1970) 93
Total Engines in the U. S. General Aviation
Fleet (Turbine Engines) (January, 1970) 95
Total Engines in the U. S. General Aviation
Fleet (Piston Engines) (January, 1970) 96
Total Engines in the U. S. Military Fleet
(Turbine and Piston Engines) (January, 1970) 98
Total Engines in the U. S. Civil Helicopter and V/STOL
Fleet (Turbine and Piston Engines) (January, 1970) . . 100
Total Engines in the U. S. Civil Helicopter and V/STOL
Fleet (Turbine and Piston Engines) (January, 1970) . . 101
Engine Classification 102
Aircraft Turbine Engine Classification System 103
Aircraft Piston Engine Classification System ..... 107
Aircraft Turbine and Piston Engine Classification
Summary 109
Emission Control Methods: Modification of
Turbine Engines 110
Emission Control Methods: Modification of
Piston Engines Ill
Emission Control Method Effectiveness: Turbine
Engine Modifications 112
Emission Control Method Effectiveness: Turbine
Engine Modifications 113
Emission Control Method Effectiveness: Turbine
Engine Modifications ]]J*
Emission Control Method Effectiveness: Turbine
Engine Modifications 115
Emission Control Method Effectiveness: Turbine
Engine Modifications 116
Emission Control Method Effectiveness: Turbine
Engine Modifications 117
Emission Control Method Effectiveness: Turbine
Engine Modifications 118
Current Uncontrolled Emission Rates - Piston
Engines (lb/1000 Ib-fuel) i -,
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Table \k: Emission Control Effectiveness: Piston
Engine Modifications 120
Table 15: Total Aircraft Turbine Engine Development
Cost/Time Sample Calculation 121
Table 16: Turbine Engine Development Cost/Time Sample
Calculation for Separate Categories; Air Carrier,
General Aviation, Military 122
Table 17: Total Aircraft Piston Engine Development
Cost/Time Sample Calculation 123
Table 18: Piston Engine Development Cost/Time Sample
Calculation for Separate Categories; Air Carrier,
General Aviation, Military I2*t
Table 19: Total Aircraft Turbine Engine Implementation
Cost/Time Sample Calculation 125
Table 20: Turbine Engine Implementation Cost/Time Sample
Calculation for Separate Categories: Air
Carrier, General Aviation, Military 126
Table 21: Total Aircraft Piston Engine Implementation
Cost/Time Sample Calculation 127
Table 22: Piston Engine Implementation Cost/Time Sample
Calculation for Separate Categories: Air
. Carrier, General Aviation, Military 128
Table 23: Turbine Engine Cost Scaling Parameter Summary 129
Table 2k; Final Cost/Time Results for Total Turbine
Engine Population 130
Table 25: Final Cost/Time Results for Turbine Engine
Population by Separate Categories: Air
Carrier, General Aviation, Military 131
Table 26: Final Cost/Time Results for Total Piston
Engine Population 133
Table 27: Final Cost/Time Results for Piston Engine
Population by Separate Categories: Air
Carrier, General Aviation, Military 13^
Table 28: Implementation Cost/Time Sample Calculation
for "Production" Turbine Engines of Existing Design. . 135
Table 29: Implementation Cost/Time Sample Calculation
for "Production" Piston Engines of Existing Design . . 136
Table 30: Implementation Cost/Time Final Results for
"Production" Engines - Turbine and Piston Engines
of Existing Design 137
Table 31: Cost/Time Results for Future Turbine Engines 138
Table 32: Reduction in Emission Factors for 100 Per Cent
Increase in Idle Power 139
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Table 33: Reduction in Taxi and Idle Emissions Resulting
from the Use of the Minimum Number of Engines
for Taxiing 140
Table 34: Total Aircraft Emissions for 1970 at Los Angeles
International Airport 141
Table 35: Percentage Reduction in Total Aircraft Emissions
Due to Avoiding Runway Delays at Los Angeles
International Airport 142
Table 36: Emissions for Taxi Mode 143
Table 37: Percentage Reduction in Total Aircraft Emissions
Due to Elimination of the Taxi Mode at Los Angeles
International Airport 144
Table 38: Pollutants from Auxi 1 iary Power Unit 145
Table .439: Comparative Reductions Resulting from Control
Methods Applied to Los Angeles Internationa]
Airport 146
Table 40: Basis for Estimating Costs of Ground Operation
Changes at Los Angeles International Airport 14?
Table 41: Implementation Cost and Time for Operations Changes
at Los Angeles International Airport ... 148
Table 42: Factors Affecting Feasibility of Operating
Changes at Los Angeles International Airport 149
Table 43: Current Ranges of Aircraft Engine Exhaust
Emission Concentrations. ... 150
Table 44: Instrumentation Accuracy Requirements for Exhaust
Gas Analysis 151
Table 45: Exhaust Gas Analysis Methods in Use at 17
Organizations
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LIST OF FIGURES
Figure 1: Turbine Engine Emission Data, Carbon Monoxide 155
Figure 2: Turbine Engine Emission Data, Total
Hydrocarbons (as CH. ) 156
Figure 3: Turbine Engine Emission Data, Nitrogen
Oxides (as NO^) 157
Figure 4: Turbine Engine Emission Data, Dry Particulates. .... 158
Figure 5: Emission Control Cost/Time Model for Typical
Aircraft Engine Family Currently In-Service 159
Figure 6: Summary of Total Turbine Engine Population
Cost/Time Analysis Procedure 160
Figure 6A: Summary of Total Piston Engine Population
Cost/Time Analysis Procedure 161
Figure 7: Summary of Air Carrier Turbine Engine
Population Cost/Time Analysis Procedure 162
Figure 8: Summary of General Aviation Turbine Engine
Population Cost/Time Analysis Procedure 163
Figure 9: Summary of Civil Aviation Turbine Engine
Population Cost/Time Analysis Procedure 164
Figure -9A: Summary of Civil Aviation Piston Engine
Population Cost/Time Analysis Procedure 165
Figure 10: Summary of Military Aviation Turbine Engine
Population Cost/Time Analysis Procedure 166
Figure 10A: Summary of Military Aviation Piston Engine
Population Cost/Time Analysis Procedure 167
Figure 11: Implementation Cost Per Engine Versus Normalized
Cost Parameters for Turbine Engine 168
Figure 12: Fuel Flow Plotted Against Power for
Each Aircraft Class 169
Figure 13: CO Emission Factors Plotted Against Power
for Each Aircraft Class 170
Figure 14: Hydrocarbon Emission Factors Plotted Against
Power for Each Aircraft Class 171
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INTRODUCTION
Background
An awareness of air pollutant emissions from aircraft developed
in the late 1950's with the introduction into service of turbine-engine
aircraft. Visible exhaust plumes from turbojet engines and increased
levels of exhaust odors at airports gave rise to complaints against
these perceptible manifestations of aircraft emissions. These complaints,
in turn, stimulated investigations by public health agencies into the
nature and extent of aircraft emissions, and these investigations have
continued unabated in the intervening years.
In 1968, Northern Research and Engineering Corporation con-
ducted a survey of information on aircraft emissions and their control.
This investigation was sponsored by the National Air Pollution Control
Administration and resulted in a comprehensive report on the
nature and control of aircraft emissions (Ref 11). This investigation
was directed primarily at an assessment of the extent or magnitude of
aircraft emissions, and identification of approaches to reducing emission
rates. The report represents the state of our understanding of the subject
in 1968, and identifies the principal sources of information on aircraft
emissions which existed at that time.
Since 1968, several organizations have been active in further
investigations of various aspects of aircraft emission control. The NREC
staff, in 1969, conducted a detailed analysis of the implementation times
and costs of controlling visible smoke emission by "retrofitting" low-
smoke combustors in existing turbine engines (Ref 2). In 1970, Scott
Research Laboratories completed an investigation of emissions from aircraft
piston engines which resulted in the first significant source of information
on this subject (Ref 3)• In '971, a series of papers on aircraft'emissions
were presented at a conference on "Aircraft and the Environment" sponsored
by SAE and DOT (Ref *+), and the results of this conference were summarized
in a paper by Paul 1 in (Ref 5). These investigations (Refs 2 through 5),
in our opinion, have produced the most significant contributions to the .
over-all subject of aircraft emissions since 1968. There have, of course,
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been many advances in more specific areas of emission control. Many of
these works will be cited later in this report.
The investigation described in this report was initiated in
response to requirements of the Clean Air Amendments of 1970. This
act calls for the establishment of aircraft emissions standards as
specified in Section 231 of the Act. Specifically, this section calls
for the investigation of emissions of air pollutants from aircraft to
determine:
1. The extent to which such emissions affect air quality in
air quality control regions throughout the United States.
2. The technical feasibility of controlling such emissions.
Based upon the information generated under such a study, the Environ-
mental Protection Agency is required to propose emissions standards
applicable to any class or classes of aircraft which cause or contribute
to air pollution which endangers the public health or welfare, and to
establish an implementation schedule commensurate with available tech-
nology and reasonable cost of compliance.
In order to carry out the above requirements, the responsi-
bilities within the Environmental Protection Agency were divided. The
Bureau of Air Pollution Sciences, Office of Research and Monitoring,
had primary responsibility to assess the impact of aircraft emissions
on air quality. The Mobile Sources Pollution Control Program,
Office of Air Programs, independently initiated a study to assess the
technical feasibility of controlling aircraft pollutant emissions and
the costs associated therewith.
This report has been prepared for the Mobile Sources
Pollution Control Program and is concerned with aircraft emission
control technology. A parallel investigation of the impact of aircraft
emissions has been conducted by NREC for the Bureau of Criteria and
Standards. The results of the impact investigation are contained in a
companion report (Ref 6).
Object ives
The over-all objective of the two investigations was to provide
information necessary for establishing standards on emissions from aircraft
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activities. The information required for this purpose falls into the
following categories:
1. Methods for controlling emissions from aircraft activiti.es.
t
2. Instrumentation requirements for measuring aircraft emis-
sions.
3- Rates of emission of various pollutants at airports from
aircraft activities.
k. Impact of emissions from aircraft activities in airport
vicinities.
Information on emission control method.s is necessary to determine
the levels to which it is feasible to reduce aircraft emissions. The re-
sults of an earlier NREC study (Ref 1) indicated that practical control
approaches include modifications of aircraft engines, fuels, and
ground operational procedures. Thus, an assessment of control methods
must be concerned with each of these categories of approaches. In assess-
ing the feasibility of a control method, three factors must be explored:
the cost of utilizing the method, the effects of the method on the func-
tioning or capacity of the aircraft system, and the effectiveness of the
method in reducing emissions.
Information on emission measurement instrumentation is necessary
to assure that aircraft emissions can be measured with the accuracy and
sensitivity necessary to enforce the desired standards. Measurements will
be required for engines operated under test conditions in the laboratory
and engines being operated while installed in all types of aircraft. It
is not necessary, for the purpose of enforcing emission standards, that
measurements be taken on engines in moving aircraft, either on the ground
or in fIight.
Pollutant emission rates at airports are not required specifi-
cally in the establishment and enforcement of air quality standards.
Presumably, such standards will be based upon instantaneous or cumulative
emissions from individual aircraft, or aircraft engines, and associated
auxiliary equipment. However, the total emission rate at an airport is
an important intermediate quantity required in relating the impact of
aircraft emissions to aircraft emission rates and activity levels. Also,
the total airport emission rate, is used as a gross measure of the importance
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of an airport as an emission source in the community.
Information on the impact of aircraft emissions is necessary to
determine the levels to which it is necessary to reduce emission rates in
order to prevent adverse health effects, property damage, or undue annoy-
ance. This information must be in the form of correlations between pollu-
tant levels in the airport neighborhood and the rates of emission at the
ai rport.
The specific objectives of this investigation of emission control
technology were:
1. To identify methods of controlling aircraft emissions through
modifications of engines, fuels, and ground operations.
j
2. To estimate the effectiveness of these control methods
in reducing aircraft emission rates.
3« To estimate the times and costs of implementing these control
methods.
k. To assess the technology of emission measurement as applied
to aircraft engines, and to identify areas where advance-
ments in instrumentation or test procedures are required.
Methodology
The program has consisted essentially of independent investiga-
tions of the following topics:
1. Emission control by engine modification.
2. Emission control by fuel modification.
3* Emission control by ground operations modification.
4. Emission measurement.
The investigation of fuel modifications was discontinued after prelim-
inary analysis indicated that no significant reductions in emiss.ions can
be achieved by modifying fuels, except for reductions in sulfur or lead
which result in proportionate reductions of S02 and lead emissions.
Engine modification control methods were identified through
reviews of earlier work (e.g. Ref 1) and through discussions with engine
manufacturers. A list of specific control methods was formulated on the
basis of preliminary analyses which indicated that each method was feasibile
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and offered a significant reduction in one or more emission classes.
Feasibility was based on 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. The results
.of the effectiveness analysis were supplied as input information to the
parallel study of impact of aircraft emissions. The predicted effective-
ness of each control method in reducing impact at airports is reported in
Reference 6.
Ground operations modification control methods were evaluated
in a similar manner. Specific methods were identified through discussions
with engine manufacturers, airlines, and airport operators. These methods
also were subjected to analyses of effectiveness and costs, and their
effectiveness in reducing emission impact also has been evaluated in the
impact study.
The emission measurement technology assessment consisted essen-
tially of the following steps:
1. Analysis of the accuracy and sensitivity requirements of
measurement instruments required for current and future
emission levels from aircraft engines.
2.. Compilation of information on measurement equipment cur-
rently used by engine manufacturers and air quality
control agencies,;and equipment available from instrument
manufacturers;
3. Review of factors affecting the design and selection of
measurement equipment, and the specification of test pro-
cedures.
In this task, full advantage was taken of the results of other groups which
have been active in studying various aspects of measurement of aircraft
emissions.
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Pollutants Considered
In this program, consideration has been given, in varying degrees,
to the following pollutant classes:
Emission constituents:
Carbon dioxide (C02)
Carbon "monoxide (CO)
Nitric oxide (NO)
Nitrogen dioxide (NOz)
Organic constituents
Total hydrocarbons (THC)
Reactive hydrocarbons (RHC)
Aldehydes (ALD)
Dry particulates (DP)
Sulfur dioxide (S02)
Sensory effects:
Visible smoke
Odor
Contributions to these pollutant classes have been considered from the
following aircraft sources:
Engine exhaust
Crankcase blow-by
Auxiliary power unit exhaust
Fuel drainage
Evaporative emissions
The assessment of measurement technology included all of these emissions
except reactive hydrocarbons (RHC). This class is not well defined at
the present time.
In the evaluation of emission control methods involving engine
modifications, the following emission classes were considered:
Carbon monoxide (CO)
Nitrogen oxides (NOx)
Total hydrocarbons (including drained fuel)
Dry particulates (including smoke)
Reactive hydrocarbons and aldehydes were not included since no correlations
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exist between engine design characteristics and emission rates for these
classes, and no control methods have been developed. S0_ emissions were
not considered since these are directly related to the sulfur content
of the fuels burned and are independent of engine characteristics.
In the evaluation of emission control methods based on ground
operations modifications, reductions in RHC, ALD, and SO. emissions were
considered in addition to those considered with engine modifications.
Report Contents
The principal results and conclusions of the program are summar-
ized in the following sections of the report. Detailed descriptions of
the methodology and results of the analyses of control methods and measure-
ment methods are contained in later sections of the report.
Background information in each of the analysis areas is rather
limited. For further information on the nature of- aircraft engines and
their emissions, an earlier NREC report (Ref 1) is suggested. The companion
report on impact of aircraft emissions (Ref 6) also is recommended as a
sourcesof related information.
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SUMMARY OF RESULTS
Emission Control by Engine Modification
Engine Classification
To facilitate analyses of engine modifications, aircraft engines
have been categorized according to their thrust or power level as follows:
Engine Class Engine Type Power Range (Ibf-thrust or ESHP)
Tl Turbine Less than 6000
T2 Turbine 6000 to 29..000
T3 Turbine Greater than
29,000
PI Piston (Includes all opposed
configuration engines)
This classification system, although it is based simply upon thrust
level, effectively separates engines of similar emission potential.
Also, the effectiveness and costs of control methods can be considered
to be similar for all engines within each class. Thus, the classification
system has been particularly useful for this program and may also provide
a rational basis for the definition of emission control standards. Specific
engine families within each class and their characteristics are discussed
in the report- sect ion entitled AIRCRAFT ENGINE CLASSIFICATION.
9
/
Emission Control Methods
Turbine Engines
Six control methods involving engine modifications have been
identified which are applicable to existing turbine engines. The control
methods and the pollutant classes which they are intended to control are
as follows:
Control Method Pollutant Classes Controlled
Combustor redesign (minor) CO, THC, NOx, DP, Smoke
Combustor redesign (major) DP, Smoke
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Control Method Pollutant Classes Controlled
Fuel drainage control THC
Divided fuel supply CO, THC
Water injection NOx
Compressor air bleed CO, THC
The first control method consists of simple modifications of the combustor
and fuel nozzle 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 with respect to those
engine in the same class demonstrating best emission performance. Each
of the other control methods is more specifically directed at one or two
pollutant classes.
Two control methods have been identified which are considered
to be applicable only to future engines as the design concepts involved
could not readily be incorporated into engines already designed. These
control methods are:
Control Method Pollutant Classes Controlled
Variable-Geometry Combustor CO, THC, NOx,; DP, Smoke
Staged Injection Combustor CO, THC, NOx, DP, Smoke
These control methods involve advanced combustor design concepts and,
as indicated, would be effective in controlling all pollutant classes
considered.
The actual reduction in emission rate achieved through the use
of a control method varies 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 the report section entitled EFFECTIVENESS
OF CONTROL METHODS: ENGINE AND FUEL MODIFICATIONS.
Piston Engines
Seven control methods have been identified which are considered
to be feasible for application to existing aircraft piston engines.
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10
These methods have been developed primarily for the control of THC and
CO emissions from automobile engines. Control methods for NOx emissions
have not been included since aircraft piston engines of current design
operate at rich fuel-air ratios and, as a result, their NOx emission
rates are very low compared to those from automobile engines. The
installation of any of the THC and CO control methods would not be
expected to increase NOx emissions significantly. The control methods
applicable to existing piston engines are as follows:
Control Method Pollutant Classes Controlled
Simple Air Injection CO, THC
Thermal Reactor CO, THC
Catalytic Reactor CO, THC
Direct-Flame Afterburner CO, THC
Water Injection CO, THC
Positive Crankcase Ventilation THC
Evaporative Emission Control THC
With regard to future piston engines, various design modifications can
be introduced for reducing emission rates. For this study, these modi-
fications have been regarded collectively as one control method as follows;
Control Method Pollutant Classes Controlled
Engine Redesign CO, THC
The modifications included in this control method would be similar to modi-
fications which have been introduced in recent years by automobile manu-
facturers to achieve moderate reductions in exhaust emissions. They do
not .include the control methods listed above for existing engines, but
may include auxiliary devices required for NOx control. Estimates of
effectiveness for piston engine control methods are presented in the
report section entitled EFFECTIVENESS OF CONTROL METHODS: ENGINE AND
FUEL MODIFICATIONS.
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Implementation Costs and Times^
Existing Engines
The cost and time requirements of applying each control method
applicable to existing engines have been estimated. These estimates are
of a preliminary nature and are intended to indicate the order of the
costs involved in controlling emissions from all civil and military
aircraft. Cost and time requirements have been estimated separately
for control method development and implementation. Development includes
all effort required through certification of the control method for a
specific engine family and tooling for production. Implementation in-
cludes initial installation of the control method on all engines of a
family, and any additional effort or materials costs associated with
the control method throughout the remaining service life of the engine.
Since very few of the control methods have actually been
developed or applied to aircraft engines, and since many factors affect
total implementation costs, many uncertainties are involved in the
estimates. The estimates of development costs and times are considered
to be reliable. Their accuracy is judged to be within a factor of about 2.
That is, the true costs and times of control method development probably
lie within a range between 50 and 200 per cent of the estimates. The
estimates of implementation costs are considered to be less reliable.
The cost and service life of a modified engine component cannot be
predicted accurately. Yet these factors strongly affect the cumulative
costs of operating and maintaining the modified engine. This uncertainty
is unfortunate since the implementation costs could be far greater than
the development costs for some control methods. Thus, the estimates of
implementation costs can only be regarded as indicative of cost penalties
which might be involved with control method implementation.
In the table below, estimates are given of the development
time, development costs; and implementation cost for application of
each control method to the current population of civil engines.
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Turbine Engines
Control Method
Combustor redesign (minor)
Combustor redesign (major)
Fuel drainage control
Divided fuel supply
Water injection
Compressor air bleed
Development
Time
(vears)
2
5
3
5
2.
4
1/2 - 5
- 7 1/2
- 5 1/2
- 7 1/2
1/2 - 4
- 6 1/2
Development
Cost
(106 dollars)
37
74
35
84
25
90
Implementati on
,Cost
(10b dollars)
343
589
44
102
151
58
Piston Engines
1 1/2 - 3
3-6
21/2-5
3 - 6
1 1/2-3
1 - 2
1 1/2-2 1/2
9
25
22
25
9
4
4
165
424
535
42**
81
94
269
Simple air injection
Thermal reactor
Catalytic reactor
Direct-flame afterburner
Water injection
Positive crankcase ventilation
Evaporative emission control
The development times listed above are the times required to reach the
point where installation of the control methods in existing engines could
beg i n. Installation of any control method in all existing engines would
reguire an additional time period which is dependent primarily on the
availability of engine maintenance facilities. The minimum time for
implementation is estimated to be 2 1/2 years for turbine engines and 5
years for piston engines.
As indicated, the costs estimates are based upon the current
engine population. Since this population will be different by the time
any of the control methods could be developed, the implementation costs
also will be different. This difference represents an additional source
of uncertainty with regard to implementation costs.
To put the implementation costs in a different perspective,
they may be.expressed as fractions of total engine costs. For a typical
Class T2 (turbine) engine, the cost of installing and maintaining control
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13
methods ranges from $4500 to $61,000, assuming a 10-year engine life.
Based on a total engine cost of $250,000, these control method impler
mentation costs represent 2 to 25 per cent of the total engine cost.
For a typical piston engine, control method implementation costs
estimates range from $600 to $4000, also based upon a 10-year engine
life. For a total engine cost of $6000, these implementation costs
represent 10 to 65 per cent of the total engine cost.
The turbine engine cost and time estimates were developed by using
the application of low-smoke combustors to the JT8D engine family as a refer-
ence case. Requirements for this case, which is considered to be a
minor combustor redesign for a class T2 engine, were estimated in detail
in 1969 (Ref 2). Requirements for other control methods were determined
essentially by proportioning the costs and times 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
again using the reference case as a basis.
The piston engine time and cost estimates are based largely on
experience to date with emission control from automobile engines.
The methodology used in developing these estimates and the
various elements of the total cost and time estimates are discussed
later in this report. Similar cost estimates are presented for
mil!tary engines.
Future Engines
Cost estimates also have been developed for incorporation of
emission controls in future engines, that is, engines which have not
yet been developed. These estimates have been defined only as fractions
of total engine cost since no reasonable basis is available for estimating
the numbers of engines which would be affected.
Emission control in turbine engines attained through the use
of advanced combustor design concepts is estimated to represent an
increase in total engine cost of 3 to 4 per cent. Emission control in
piston engines achieved by engine design modifications probably would
not result in any significant increase in engine cost. However, if
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greater control of emissions is required than can be achieved by engine
design modifications, 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 per cent of total
engine cost.
These cost estimates represent the increased costs of new
engines with emission controls installed. It is reasonable to expect
additional continuing costs for maintenance of the control methods.
These maintenance costs would be similar to those for modification of
existing engines which were estimated" to represent 2 to 25 per cent of
total turbine engine costs and 10 to 65 per cent of total piston engine
costs.
Emission Control by Ground Operations Modification
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
since most of these operations are prescribed by airport or aircraft
operating procedures. Characteristic operating or LTD (landing-take-off)
cycles have been defined for various classes of aircraft for purposes
of estimating pollutant emissions (Refs 1, 3, and 6).
The LTO.cycle can be separated logically into flight and
ground operations. Flight operations include the approach and climb-
out modes as well as the landing and take-off runs, even though the
latter occur on the ground. Ground operations include the taxi and idle
modes of the cycle and, for purposes of this study, all servicing and
support operations which involve emission sources. This separation is
logical for two reasons. First, flight operations as defined here are
those which cannot readily be modified as an approach to reducing pollutant
emissions. Second, flight operations are conducted almost entirely
with aircraft engines at full or part power, and under these conditions,
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15
pollutant emission rates are quite different from those at the low power
levels which are characteristic of ground operations. Aircraft ground
operations contribute substantially to concentrations of CO and THC
which exist at air carrier airports because of the relatively high emis-
sion rates of these pollutant classes at low engine power levels,
and because ground operations are largely confined to limited areas
within the airport boundaries.
Emission Control Methods
Seven methods have been identified which offer some degree of
control of CO and THC emissions at air carrier airports by modification
of ground operational procedures. These methods, which under preliminary
analysis were judged to be feasible, are as follows:
1. Increase engine speed during idle and taxi operations.
2. Increase engine speed and reduce number of engines operating
during idle and taxi.
3. Reduce idle operating time by controlling departure times
from gates.
4. 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.
7- Manually remove fuel from fuel drainage reservoirs.
The first two methods reduce emissions by requiring engines to be operated
at more efficient power settings, and the next four methods reduce emis-
sions by reducing operating time of either main or auxiliary engines. The
effectiveness of these methods in reducing emissions varies considerably,
but certain methods (2 and 5)t if implemented, would reduce total CO
and THC emissions to approximately one-half their current levels at air
carrier airports.
The control methods listed above are not, in general, applicable
to small, piston-engine aircraft, and, therefore, do not offer means for
controlling emissions at general aviation airports. Delay times at take-off
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16
are significant at some general aviation airports. However, general aviation
operations are, not sufficiently controlled for a system of controlled gate
departures or engine start-up to be effective in reducing delays. If'emissions at
general aviation airports are to be controlled, control methods involving engine
modifications must.be/used.
Implementation Costs and Times
The cost and time requirements of the control methods
involving ground operations modifications have been estimated for one
specific airport (Los Angeles International). These estimates involve
many uncertainties and, therefore, must be regarded as preliminary.
The estimates are considered to be accurate within a factor of 2. That
is the true costs and times of implementation at the airport considered
probably are within a range of 50 to 200 per cent of the estimates.
The estimates are as follows:
Annual Operating
Control Method Time Initial Cost . Cost Change
(years) (1Qb dol llrl) (10-6 dol lars)
1. Increase engine speed 0 0 8.5
2. Increase speed, reduce number 0.3- 0 -3.0
3. Control gate departure 5 15 -1.6
k. Transport passengers 2-5 65 5.0
5. Tow aircraft ' 1 1.2 M7
6. Reduce APU operation 0.5 1.3 1.5
7. Manual drainage .0.5 . 0..04 3.0
Implementation of these methods at other airports would involve costs of
the same magnitude. However, the actual costs would vary with activity
level and the present availability of auxiliary equipment.
Emission Measurement Technology
Sampling and Test Procedures
Obtaining a representative sample of exhaust gas from an air-
craft engine for analysis of emission rates is not a trivial procedure.
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17
The requirement is difficult at the outset with turbine engines because
of the jet blast environment in which the sampling equipment must be installed.
Beyond that problem, the following factors are all found to have significant
effects on the composition of the exhaust sample:
Engine power level
Timewise and spatial variations of exhaust composition '
Sampling line diameter, length, material, and temperature
Ambient temperature and humidity
Ambient pollutant levels
Procedures for sampling and analyzing turbine engine exhaust gases have
been under development for several years by engine manufacturers and
various government agencies. More recently the Society of Automotive
Engineers E-31 Committee has been formed to standardize these procedures.
Standardization of measurement techniques will minimize the variations
due to the factors listed above. However, the sources of error in collecting
samples and the variability of samples among different engines must be
considered in the establishment of emission control standards.
Sampling requirements for aircraft piston engines can be expected
to be similar to those for automobile engines. There are no apparent
factors which would cause variability in exhaust samples beyond those
factors already recognized with automobiles.
Emission Measurement Instrumentation
Measurement of concentrations of most pollutants in exhaust
samples from aircraft engines is generally within the capabilities of
existing instruments, and will remain so even with modifications of
engines to reduce emission rates. The ranges of accuracy and sensi-
t.ivity which are required for aircraft emission measurements are dis-
cussed later in this report.
The various types of instruments which are available and in
current use for aircraft emission measurement have been reviewed.
Instruments which appear to be most suitable for measurement of turbine
engine emissions at the present time are as follows:
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18
Pollutant Class Instrument Type
CO and C0_ Non-dispersive infrared (NDIR)
THC Heated flame.ionization
NO Chemiluminescence
HO Non-dispersive ultraviolet (NDUV)
Smoke SAE Smokemeter (ARP 1179)
Particulates None
S0? Determined from fuel analysis
Aldehydes 3-MBTH
Odor Human odor panel
Even though a suitable instrument for particulate measurement is not
available, emission rates of-dry particulates can be estimated on the
basis of smokemeter measurements. These instruments and alternative
equipment are discussed in the APPENDIX.
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19
CONCLUSIONS
From the results of this program,.it is possible to formu-
late conclusions on the costs of various emission control methods and
the effectiveness of these methods in reducing emission rates from air-
craft engines. The effectiveness of these control methods in reducing
impact of aircraft emi.ssions at airports, is discussed in Reference 6.
In evaluating control method effectiveness, an order of magnitude
system has been used which is based upon multiple factors of two in
emission rate reduction. The system is as follows:
Fraction of
Order of • Emission Reduction Emission Rate
Effectiveness Attainable (Per Cent) Remaining
1 50 0.50
2 75 0.25
3 90 0.10
This system is useful for comparing emission control methods.
The following conclusions pertain to the control of emissions
from turbine-engine aircraft at air carrier airports:
1. First order reductions in CO and THC emission rates can
be achieved by modifying aircraft ground operations. If
these reductions are achieved by modifying engine operating
power levels and reducing the number of engines used in
taxi operations, the costs will be negligible, and the
controls can be implemented immediately. A reduction in
odor levels at airports should accompany the THC emission
reduction.
2. First and, possibly, second order reductions in CO and
THC emission rates can be achieved by engine modifications.
Various alternative methods are available for achieving
these reductions^ but the cost of implementing any of
these methods in the air carrier aircraft fleet will be
of the order of 100 million dollars. The time required
to implement any engine modification control method in
the air carrier fleet will be from 5 to 10 years.
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3. A second order reduction in NOx emission rates can be
achieved through the use of water injection during take-
off and climb-out operations.. The cost of applying this
control method to the air carrier fleet is estimated to
be approximately 100 million dollars, and 5 years or more
will be required to implement the method. The degree
of control can be reduced or increased by reducing or
increasing the rate or duration of water injection.
However, the costs will not vary proportionately.
k. A first order reduction in particulate emissions can be
achieved by major modifications of combustors, but at very
high cost (600 million dollars) and with long implementation
times (7 to 10 years). The reduction in particulate emis- '
sions that would result from minor combustor modifications
would be less than first order.
5. Visible smoke emission from turbine engines can be sub-
stantially reduced by minor combustor modifications, and
such modifications are being implemented for certain
engines. The additional cost of eliminating smoke emission
from all air carrier aircraft is estimated to be of the
order of 100 million dollars.
6. Second or third order reductions in CO and THC emissions
and first order' reductions in NOx and particulate emissions
will accompany the introduction of advanced combustor
design concepts in future engines. Complete elimination
of visible smoke and substantial reductions of odor will
accompany these advanced designs. Associated costs will
be of the order of 3 per cent of the total engine cost.
Engines with these features will not appear in service
before the late 1970's.
The following conclusions pertain to the control of emissions
of piston engines at general aviation airports:
1. First order reductions in CO and exhaust THC emission rates
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21
can be achieved by simple air injection systems. Retro-
fitting costs would be of the order 200 million dollars
with an implementation time of approximately 6 years.
2. Reductions as high as third order in CO and exhaust THC
emissions can be achieved by more advanced control methods
such as thermal reactors or catalytic reactors. Retro-
fitting costs would be of the order of 500 million dollars
and implementation times would be 8 years or more.
3. Effectiveness of THC emission control from piston engines
can be increased by nearly one order of magnitude if
positive crankcase ventilation is combined with another
THC control method. PCV would not be effective alone
because of the fuel-rich operating conditions of aircraft
piston engines. The cost of applying PCV to existing
piston engines would be of the order of 100 million dollars.
k. First order reductions in CO and THC emissions can be
anticipated in future engines by modifications of combustion
chambers and control systems. .Higher order reduction can
be obtained by combining engine design modifications with
auxiliary control devices. Emission control in future
engines may result in increased engine costs up to 10
per cent, depending upon the degree of emission control
achieved. Emission control could be incorporated in new
aircraft piston engines by the mid-1970's if initiated now.
5« Lead emissions from aircraft piston engines could be
reduced by the use of low-lead or lead-free gasoline. These
reductions couid result directly from the control of lead,
or could be incidental to the use of catalytic reactors for
CO and THC control. The cost of low-lead fuels would be
approximately 10 per cent greater than current fuel costs.
The technology of emissions measurement will be adequate to
support emission control standards requiring first, second, or third
order reductions in emission rates when sampling and test procedures have
been refined and standardized.
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AIRCRAFT ENGINE CLASSIFICATION
The objective of this program is to evaluate the effectiveness,
costs, and time requirements associated with the application of emission
control methods to aircraft engines. The program is concerned with engines
in current use and engines which will be in service during the next ten
years. The evaluation of current engines will be based upon the applica-
tion of control techniques to specific existing engines, whereas the evalua-
tion of future engines will necessarily be based upon projections of future
engine characteristics and populations. The purpose of this section is
to identify the specific engines which will be included in the analysis of
current engines.
Engines to be considered include both turbine and piston engines,
and military as well as civil aircraft engines will be included. The
general relationship between the engines and the aircraft classification
system is illustrated in Table il.
Turbine engines will be considered by "family". That is, all
engines with the same basic model number, e.g., JT9D or CF6, will be con-
sidered as a single engine type. This approach is reasonable since, in
most cases, a family of engines has a common combustion system design, and,
hence, the emission characteristics of all engines of the family will be
similar. This approach also is advantageous in that the number of engines
to be analyzed is limited to a reasonable level.
Piston engines also will be considered by family wherein the
family designation, e.g.,.10-200 or TIO-360, indicates the use of fuel
injection or turbocharging as well as the engine displacement.
Engine Population
Engines to be considered in this analysis are listed in Tables 2
through 5- Estimates of the numbers of civil aircraft engines in current
use are included. Civil aircraft engines are identified separately as
a-i r carrier or general aviation types in Tables 2 and-:3. Military
aircraft engines are identified. in Table k, and current population,
data are provided. Since this information on military engines is not
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readily available, the results presented must be assumed to be reasonable
approximations. Helicopter and V/STOL aircraft engines are listed sepa-
rately in Table 5-
Engine Classification
An engine classification system is required to facilitate the
analyses of effectiveness and costs of specific emission control methods.
This classification should also provide a rational basis for the appli-
cation of emission standards in the event that standards are deemed nec-
ess.ary. For these purposes, the method of classification should separate
engines into categories wherein all engines have similar emission rates
when normalized according to an appropriate engine size parameter. Also,
the feasibility and effectiveness of control methods should be similar for
all engines within a single category.
The classification system which has been adopted is indicated
in Table 6. Three classes of turbine engines are defined, and all piston
engines are included in a single class. The system is effective in that
it separates engines according to their principal applications, and also
according to certain design characteristics which affect emission rates.
The small turbine engine class (Tl) includes most turboshaft
and small turbojet engines used in business aircraft. These engines should
be considered separately because the relatively small size of the combustor
components (or large surface-volume ratio) makes control of certain emis-
sions more difficult than with larger engines.
The next turbine engine class (T2) includes most 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 c-lass (T3) includes large turbofan
engines for "jumbo" transport aircraft and the SST engines currently in
use or under development. A grouping of the engine.-populations according
to this classification system is presented in Tables 7 and 8 for aircraft
turbine and piston engines respectively.
Within each of these classes, engine emission rates can be
expected to be similar when expressed as an emission index (lb/1000 Ib-
fuel). Emission rates of all pollutants can be correlated effectively
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with fuel rate and other parameters indicating the engine operating
condition such as power level (turbines) or fuel-air ratio (piston
engines). The emission index is in widespread use as a correlating
parameter, and can be converted readily to other bases such as Ib/hp-hr
or Ib/lb-thrust-hr by using appropriate specific fuel consumption
parameters.
It is expected that this engine classification will suffice
for purposes of this program and for definition of emission standards
for existing engines. The system may require modification, however, as
new engines and engine types are developed.
A summary of the number of engines and engine "families" in
the total current population and in the categories of air carrier, general
aviation, civil aviation, and military aviation is presented in Table 9
by class.
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25
EFFECTIVENESS OF CONTROL METHODS:
ENGINE AND FUEL MODIFICATIONS
Introduction
An analysis has been conducted of the technology of emission
control for aircraft engines by means of engine or fuel modifications.
The purpose of this analysis was to identify specific methods of reducing
pollutant emissions from aircraft, and to indicate the reductions in
emission rates attainable by these methods. Various engine modifications
have been identified which appear to be feasible, in the sense that they
can be applied to aircraft without degrading engine reliability or
seriously reducing aircraft performance. The costs of implementing
these control methods also appeared to be within reasonable limits, at
least from preliminary analysis. However, implementation costs of these
control methods have been evaluated in more detail, and the results of
this cost evaluation are presented in the next section of this report.
Control Methods
Turbine Engine Modifications
Control methods considered feasible for turbine engines are
listed in Table 10. Six methods are, at least in 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 since the modifications required are
too extensive to be applied to engines for which development has been
completed. These methods have been identified in previous NREC studies
of gas turbine combustor design concepts and through discussions with
engine manufacturers. The methods are described in the following
paragraphs.
Minor Combustion Chamber Redesign
A minor combustion chamber redesign is defined in this analysis.
as a modification of the combustor liner or fuel nozzle, or both, not
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26
involving a .change in design concept. Such modifications generally
result in changes in airflow distribution or fuel spray pattern within
the combustor. The modification being made currently to JT8D engine
combustors for control of smoke emission is considered to be a minor
combustion chamber redesign. This control method could be used to reduce
all emissions from conventionally designed combustion chambers. However,
it is not likely that emission rates could be reduced substantially
below the lowest rates which have been achieved in existing engines.
Major Combustion Chamber Redesign
A major combustion chamber redesign is defined as a modification
of the combustor liner and fuel nozzle incorporating an advanced fuel
injection concept. This modification would involve discarding a con-
ventional liner and pressure-atomizing fuel nozzle combination, and
substituting a new combustion chamber with a carbureting or prevaporizing
fuel injector. This type of combustion chamber is being used in some
engines of recent design (e.g., CF6 and F101), and its use results in
substantial reductions in particulate and smoke emissions (Refs 12 and 13)<
Other changes in combustor design could be included in this
control method, such as the substitution of an annular combustor for a
canannular combustor or the introduction of variable geometry. However,
changes such as these are not considered feasible for existing engines.
Fuel Drainage Control
This control method is concerned with the dumping of fuel
which results from the draining of fuel manifolds at engine shut-down .
and start-up. At present, this drained fuel is collected in a drainage
reservoir in many civil engines, and the reservoir is emptied automati-
cally during take-off or climb-out operations. The drained fuel is
.discharged to the atmosphere. In some military engines, the fuel is
drained directly onto the ground at shut-down and start-up.
A fuel drainage control system is defined here consisting of
an automatic transfer system for emptying the fuel drainage reservoir
and returning the fuel to one of. the aircraft fuel tanks. In the
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•s.
27
definition of this system it is assumed that drainage of fuel manifolds
at engine shut-down and start-up will continue to be required. The
drainage control system would be an additional mechanism permanently
installed in each engine to eliminate the dumping of drained fuel into
the atmosphere or onto the ground. An analogous control method is
defined later under ground operations modifications which would serve
the same function, but would consist of ground-based auxiliary equipment.
Divided Fuel Supply System
This control method consists of a modification of the fuel
supply system to allow some fraction of the fuel nozzles to be shut down
during low power operation. The modification would result in increased
fuel flow through the remaining fuel nozzles, thereby increasing the
local fuel-air ratio in the combustion region. This increased fuel-air
ratio should result in more efficient combustion and reduced CO and
THC emissions during idle and taxi operations. This control method
is considered to be feasible for all turbine engines and is used currently
in some small engines. In engines with can or canannular combustors,
operations with all fuel nozzles probably would be required at start-up
to achieve ignition in all cans. However, the control method could be
applied immediately after ignition.
Water Injection
Water injection is used in many turbine engines to allow
engine power output to be increased without increasing turbine inlet
temperatures. Use of the method in civil aircraft generally is. limited
to take-off operations on hot days. No data have been published on the
effect of existing water injection systems on exhaust emissions from
aircraft engines. However, steam injection has been shown to result in
substantial reductions in NOx emissions (Ref 14). With current aircraft
injection systems, water is introduced well upstream of the combustor
and probably is vaporized before entering the combustion zone. Therefore,
its effect can be expected to be the same as steam injection.
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28
It is assumed that water injection for NOx control would be
accomplished by means of injection systems similar to those in current
use- Water injection would be used during take-off and climb-out opera-
tions with an injection rate approximately equal to the engine fuel
consumption rate. In addition to the installation of the injection system,
the aircraft would require a supply of demineralized water. It is possible
that regular use of water injection would reduce combustor service life
due to increased corrosion rates.
Water injection is the only control method which has been
defined which would achieve substantial reductions in NOx emissions
from existing engines. It offers the potential advantage of discretionary
usage. That is, use of the method could be limited to situations where
NOx control is required to improve local air quality.
Modify Compressor Air Bleed Rate
This control method consists of increasing the bleed air rate
from the compressor during low power operation. Its effect would be to
reduce the flow of air through the combustion chamber and increase the
fuel-air ratio. As with control method tk (divided fuel supply), this
change would produce more efficient combustor operation and reduced CO and
THC emissions. Maximum air bleed rates for current engines are approxi-
mately 5 to 10 per cent of total airflow. In defining this control
method, it is assumed that this rate can be increased to 20 per cent at
. id.le by modification of the flow passages and bleed valves at the compressor
exit. These modifications must be achieved within the geometric constraints
of the engine cowling, and bleed air must be exhausted without creating
excessive noise. With these constraints, a bleed rate of 20 per cent
may not be feasible. However, some increase over current rates is likely.
Variable-Geometry Combustion Chamber
Variable geometry in combustor design is. not a new concept.
This feature has been employed in experimental combustors for many
years (Ref 15). It has not been used in practice since the added
complexity has not been justifiable on the basis of improved combustor
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29
performance. The function of variable geometry is to provide control
of the fraction of the total flow which enters the combustion zone.
With such control, the combustion zone fueliair ratio can be maintained
at a value corresponding to efficient combustion performance at all
operating conditions. This feature alone will provide substantial
reductions of CO and THC emissions at low power. With the addition of
an advanced type of fuel injection system which provides a high degree
of premixing of fuel and air, substantial reductions of NOx and particulate
emissions also can be achieved (Ref 16).
A variable-geometry combustor increases the complexity of the
engine and its control system, and therefore, would increase the cost of
developing and manufacturing the engine. It is possible that a combustor
with movable parts also will have a shorter service life than fixed
geometry combustors.
Staged Injection Combustor
Staged injection is a concept wherein combustion occurs in
discrete steps in the flow of air through the combustion chamber. The
concept can take a variety of forms. However, the most likely form for
improved emission control would consist of dual combustion zones arranged
in series with independent fuel injection in each zone. The first zone
would serve primarily as a pilot combustor and would operate continuously
at a fuel-air ratio providing very efficient combustion. The rate of
fuel injection in'the second zone would vary widely to provide variation
of engine power. Fuel would be introduced by means of advanced fuel.
injection concepts which provide a high degree of premixing with the
inlet ai r.
The added flexibility of dual combustion zones and fuel
injection systems would be used to achieve the same results as with
variable geometry. Performance evaluations of staged injection combustors
have not been published, but it is reasonable to expect substantial
reductions in all emissions with the use of this concept. The approach
is advantageous in that no movable combustor parts are required. However*
a staged injection combustor may be larger in size than a conventional
combustor for the same engine.
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Piston Engine Modifications
Control methods considered feasible for aircraft piston engines
are listed in Table 11. These methods include most approaches to control
of carbon monoxide (CO) and total hydrocarbon (THC) emissions which have
been developed for automotive engines. Control methods for nitrogen
oxide (NOx) emissions are not included since the fuel-rich operating.
conditions of aircraft piston engines automatically result in low NOx
emission rates (Ref 1). NOx emission control may be required, however,
in conjunction with any attempt to-reduce CO and THC emissions by changing
engine operating conditions.
Eight piston .engine control methods are listed, including
direct-flame afterburners and water injection which are not being con-
sidered currently for automotive engines. Afterburners are included
here since they might be used to advantage by utilizing the high.velpcity
airflow around the aircraft. Also, the feasibility of adapting other
methods may be less for aircraft than for automobiles.
The piston engine emission control methods were identified and
evaluated through reviews of published evaluations of these methods. Of
the methods identified, all are considered applicable to existing engines
except for any attempt at redesign of the basic engine or its control
systems. The methods are described briefly below. More detailed
descriptions of these methods can be found in References 17 and 18.
Simple Air Injection
Simple air injection consists of controlled amounts of air
injection at the exhaust ports of each engine cylinder. The method
results in modest reductions in CO and THC emissions.
Thermal Reactors
The thermal reactor is an extension of the air injection concept.
An insulated chamber is mounted in the exhaust system into which air is
injected. Improved mixing of exhaust gases and air and increased residence
time provide substantial reductions in CO and THC emissions without
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31
increasing NOx emissions. Thermal reactors do not function effectively
until they reach their steady operating temperatures. Thus, they are
not effective at reducing emissions during engine start-up.
Catalytic Reactors
Catalytic reactors for control of CO and THC emissions function
in a manner similar to thermal reactors. Additional air is injected and
mixed with exhaust gases in a chamber mounted in the exhaust system.
Oxidation of CO and THC is induced by catalyst beds through which the
gases flow so that the reactor operates at a lower temperature than
thermal reactors. Like the thermal reactor, the catalytic reactor does
not function until it reaches its normal operating temperature.
Direct-Flame Afterburner
A direct-flame afterburner is a thermal reactor with both air
and additional fuel injected to maintain the temperatures required for
CO and THC oxidation. The use of additional fuel for temperature control
allows the afterburner to be installed at the end of the exhaust stack
where air could be induced from the propeller stream. Air induced in
this manner would eliminate the necessity for an auxiliary air pump.
An afterburner would, however, require a separate fuel supply system.
Afterburner effectiveness would be comparable to thermal reactor
performance and it would be effective immediately upon start-up. Thus,
•its over-all performance would exceed that of the thermal reactor over
a complete operating cycle.
Water Injection
Water injection provides a means for operating an aircraft
piston engine at leaner fuel-air ratios so that CO and THC emissions
would be reduced. Water injection would allow this change without
increasing engine heating or NOx emissions. The function which would be
served by water injection is now provided by the injection of excess fuel.
The rich fuel-air ratios resulting from this practice are responsible for
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32
the high CO and THC emission rates from aircraft piston engines
(Refs 1 and 3).
With this control method, water would be injected at controlled
•rates into the engine inlet manifold. A separate fluid storage and
control system would be required as well as a supply of demineralized
water. The regular use of water injection could be expected to result
in increased corrosion rates of engine components.
Positive Crankcase Ventilation
Positive crankcase ventialtion (PCV) is in nearly universal
use in new automobile engines. It consists of a connecting line between
the engine crankcase and the air intake with a valve to control the flow
rate in the line. The system creates a flow of air through the crankcase
which flushes blow-by gases from the cylinders and carries them into the
air intake. CO and THC emissions in the blow-by gases are oxidized
during the normal cylinder combustion process or by an auxiliary
control method in the exhaust system.
PCV systems would not be effective with aircraft engines unless
they were adjusted to operate at leaner fuel-air ratios. With their
present operating conditions, no excess oxygen is available in the engine
cylinder to oxidize blow-by emissions. Thus, the PCV system is not
considered to be an effective emission control method for aircraft piston
engines unless it is combined with another method for CO and THC
emission control.. When combined with.another control method such as a
therma.l reactor, PCV will increase the effectiveness of THC emission
control substantially since the other control methods do not affect
blow-by emissions.
Evaporative Emission Controls
Control systems are being developed currently to reduce THC
emissions due to evaporation from fuel supply systems. These control
systems make use of a variety of concepts and components, but generally
accomplish emission control by collecting evaporated fuel while the engine
is shut down and feeding the collected fuel to the engine when it is started.
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The magnitude of evaporative emissions from piston-engine aircraft is
not known, and the adaptability of automotive control methods to aircraft
also is unknown. It can only be stated qualitatively that THC emissions
probably occur due to evaporation and that they are amenable to some
degree of control by methods which exist for automobiles.
Engine Redesign
During the past several years, several minor design changes
have been made with automobile engines to reduce emission rates without
the addition of auxiliary control devices. These changes include
modifications in combustion chamber geometry, valve and spark timing,
and fuel-air ratios. Other changes which might also be made to reduce
emissions include changes in compression ratio and cylinder wall tem-
peratures. Some degree of emission control can be achieved by such
changes in aircraft piston engines. However, these changes also are
likely to increase engine operating temperature, reduce power output, and
increase NOx emissions. Thus, the degree of CO and THC emission control
attainable by engine redesign is considered to be modest, unless other
control methods are used in conjunction with design changes.
Fuel Modifications
Modifications of aircraft fuels can be considered for control
of emissions of lead, SO., and visible smoke. These modifications
consist of removal of fuel impuritiesj the reduction of currently used
additives, or the introduction of new additives. It is recognized that
emissions of reactive hydrocarbons and aldehydes are related to fuel
composition. However, these relationships are not sufficiently well
defined to provide bases for emission control methods.
Fuel modifications are discussed briefly below, but have not
been considered in the detailed analyses of emi.ssion control effectiveness
and costs which follow. With the exception of lead emission control,
modifications of fuels are1 .not considered to be feasible methods of
emission control. The effects and costs of lead reduction are well-
documented elsewhere and need not be evaluated in detail in this program.
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Lead Emission Control
Lead additives are contained only in aviation gasolines used
by aircraft piston engines. Turbine engine.fuels do not contain lead
additives. Low-lead or lead-free gasolines similar to those which are
available for automobile engines in limited quantities, could be used
in aircraft engines. However,, a higher lead content may be required for
aircraft engines because of the relatively high octane requirements of
certain engines. Low-lead gasolines are more costly than conventional
leaded gasolines by about 10 per cent. A more serious problem, however,
is the incidence of valve failure resulting from the use of low-lead
gasoline. Thus, a reduction in lead may result in increased engine
maintenance costs as well as fuel costs. The degree of emission control
achievable is, of course, directly proportional to the reduction in lead
content of the fuel.
S02 Emission Control
Both aircraft piston-engine and turbine-engine fuels contain
sulfur as an impurity. The sulfur content is highest in the heavier
turbine engine fuels. -However, the sulfur content of all aviation fuels,
typically less than 0.05 per cent, is far below that of liquid petroleum
fuels used for heat or power generation in stationary combustion systems.
Reduction of the sulfur, content of aviation fuels below their current
levels would be very costly.
Smoke Emission Control
Various materials have been found to reduce smoke emission from
turbine engines when added to fuels in small quantities (Ref 1). Most
of these materials are metal compounds which have adverse effects on
engine components and produce new emission species with unknown, but
unattractive, characteristics. Thus, additives for smoke control are
not considered to be desirable for regular use in aircraft engines at
the present time. It is possible, however, that further research will
produce smoke-control additives which are free of these undesirable
effects.
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35
Control Method Effectiveness
The effectiveness of each of the control methods listed in
Tables 10 and 11 has been estimated and the-results are listed in Tables
12 and 14. Estimates are based upon demonstrated performance in a few
cases. However, in most instances, no direct experience has been
obtained with these control methods on aircraft engines. Therefore, to
a large extent, the effectiveness estimates are based on theoretical
analyses of engine performance with the changes in operating conditions
associated with the control methods. The bases for these estimates are
indicated in the tables.
Effectiveness of each control method has been rated according
to a scale of the degree of emission reduction attainable. The degree of
reduction is expressed on an "order of magnitude" basis where, in this
case, an order of magnitude is defined as a reduction by a factor of two.
Considering the uncertainties involved in the application of these control
methods to aircraft engines, effectiveness estimates cannot be made more
accurately than within a factor of two. Therefore, this approach is
considered to be valid and it offers a systematic method of classifying
the effectiveness of various engine and control method combinations.
The effectiveness rating scale resulting from this approach is as follows:
Order of Per Cent Reduction Fraction of Emission
Affect iveness Attai nable Rate Remaining
First 50 0.5
Second 75 0.25
Third 90 (Rounded) 0.1
Emission control effectiveness is indicated in the tables by one of these
orders of effectiveness for each control method and pollutant for which
a. significant degree of control would be expected. Pollutants for which
little or no control would be expected are not listed. Effectiveness is
indicated separately for each engine class.
No estimates have been made for control of reactive hydrocarbons
or aldehydes since control methods applicable to these emissions have not
been identified. It is reasonable to expect some reductions in these
emissions along with reductions in THC emissions.
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36
Emission control effectiveness for turbine engines is based
upon reductions attainable from "best current" emission rates. These
rates are defined as those attainable through control method tl-- minor
combustor redesign. The best current rates were taken from the compilation
of emission data shown in Figures 1 through k. It is assumed that all
engines in each class could be modified to achieve these best rates. The
values of these rates are listed in Table 12A. These best rates are
not the lowest rates indicated for each engine class, but are rates near
the low end of each data set which appear to be realistically attainable.
The use of the "best rate" basis is necessary to allow effectiveness esti-
mates to be made by engine class. Because of the wide variations in
actual emission rates for turbine engines, the use of average rates as
a basis for an effectiveness analysis would be less meaningful.
Effectiveness estimates for piston engines are based on reduc-
tions from current uncontrolled rates listed in Table 13« Emission rates
from piston engines do not vary widely, so that control effectiveness
can be based on average rates for existing engines.
The effectiveness estimates shown in Tables 12 and ]k are based
in most cases on the application of individual control methods with the
engine otherwise unchanged. Exceptions are made in the case of methods
t2, tk, t5, and t6 for which it is assumed that method tl has already
been utilized to achieve "best current emission rates". Method p6
(PCV) also is an exception in that it is only considered to be useful in
combination with method pi, p2, p3, P^, or p5«
From the effectiveness estimates, the following general state-
ments can be made with regard to the various emissions:
1. Minor combustor modifications (tl) would result in modest
reductions in all emissions, and would eliminate all or
most visible smoke emission.
2. Other turbine engine modifications would provide further
reductions in particulates (t2), NOx (t$), and low power
emissions of CO and THC (tk and t6).
3. Future turbine engines with combustors of advanced design
will have low rates of emission for all pollutant classes
and probably will not require additional control methods.
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37
k. Various degrees of control of CO and THC emissions can
be achieved for aircraft piston engines by modifying
engine design characteristics, or by installing auxiliary
control devices.
Any of the modifications defined for existing turbine engines
(tl through t6) could be combined to achieve increased emission control
effectiveness, with the exception of methods tk and t6. These two methods
are mutually exclusive. Piston engine modifications pi through p5
are designed to serve the same function and, thus, are mutually exclusive.
All of the others could be combined with any of pi through p5 to achieve
increased emission control effectiveness.
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38
IMPLEMENTATION COSTS AND TIMES OF CONTROL
METHODS: ENGINE MOD IFI CAT IONS
Included among the objectives of this program is an evaluation
of the cost and time requirements associated with the application of
emission control methods to aircraft engines. The program is concerned
with engines in current use and engines which will be in service during
the next 10 years. The evaluation of current engines is based upon the
application of control techniques to specific existing engines, whereas
the evaluation of future engines is on a different basis, involving future
engine characteristics and populations. The purpose of this section is
to present the results of the analysis in terms of cost and time require-
ments associated with the application of several specific emission control
methods.
Engine Classification and Control Method Definition
The current turbine and piston engine population, classified into
three turbine classes and one piston class, was presented previously in
Tables 7 and 8, respectively. These tables list engines by "family",
meaning that only the basic engine model number is considered, such as CF6
or JT9D. The table also identifies the engine manufacturer, the engine
type, the engine thrust or equivalent power level, the turbine engine
combustor type, the number of engines in current use, the maximum produc-
t.ion capacity for each engine, where available, and the aircraft class in
which the engine is used for correlation with the data provided in Tables
1 through 5- Note that the total number of turbine and piston engines listed
in Tables 7 and 8 in current use are further broken down into air carrier,
general aviation and military engines.
The emission control methods applicable to both turbine and piston
engines are listed in Tables 10 and 11, respectively. In each table, the
control methods are subdivided into categories applicable to current engine
(retrofitting) and to future engines. In general, it has been concluded
that emission control methods appropriate for future engines cannot be
incorporated into current engines. Since the incorporation of these
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39
"future" engine emission control methods would be an intrinsic part of the
"future" engine design process, the analysis of the cost and time involved
is not compatible with the analysis conducted on current engines. Hence,
future engine emission control is discussed separately in this section,
following the initial discussion of the current engine analysis.
Cost and Time Analysis Procedures
An analysis of the cost and time involved in the application of
various emission control methods to current engines was conducted, using
the procedures applied to the JT8D engine "family" in Reference 2, as a
basis. Costs and times were established for both turbine and piston
engines for two general categories, which are best described as "Develop-
ment" and "Implementation" costs and times, the elements of which are
described in detail below.
For the case of the turbine engines, it should be recalled that
three classes of engines has been suggested in Table 7, based upon thrust
level ranges. For each class or thrust range, a typical or "baseline" engine
was selected for the cost analysis, with the selection criteria being
generally based upon population. The analysis procedure is illustrated
in the tables provided which include a "sample calcuation" of both the
development and implementation costs and time for class T2 engines for
which the JT8D is the "baseline" engine. A similar procedure is followed
with sample calculations provided, for the piston engines, although no
specific "baseline" engine was identified, since only one class of engine
exists and the size or power range is much narrower for the piston engines
as compared to the turbine engines.
The turbine and piston engine sample calculations are described
in the following paragraphs. It should be noted that the explanatory
paragraphs apply generally to one engine class only such as the class T2
turbines for which the JT8D is used as a baseline engine. In order- to
arrive at costs for other turbine engine classes, a scaling factor is used
which is explained in later paragraphs. The process can be visualized best
by a study of Figures 6 through 10.
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"Development" Cost and Time Analysis
The term "Development", as used herein implies the "one-time"
costs and times associated with the evaluation and refinement by testing
of a given emission control method for a specific engine family. It also
includes the tool design and procurement costs and times required to in-
troduce the given control method into the production schedule for pro-
duction engines, if applicable, and with the overhaul schedule for retro-
fitted engines. The "development" cost and time elements which were treated
for each control method are described below, in the order listed in Tables
15 and 17-
Engineering Development Cp^t
This cost consists of the manpower costs associated with a "team"
of engineers and draftsmen who perform the necessary analysis and design
calculations required for a given control method and produce sets of draw-
ings and test hardware ready for testing.
Engineering Development Time
This time covers the period from the initial analysis until hard-
ware is ready for testing.
• Testing Cost
This cqst consists of the manpower costs associated with a "team"
of engineers and technicians who perform the tasks of assembly, installation,
testing, data analysis, and disassembly in that order on various sets of
test hardware supplied in original and modified form until the testing of
the final, refined emission control system is completed. Testing facilities
are assumed to exist. The cost of operating the test facilities is included.
Testing Time
This time covers the period from the receipt of initial hardware
ready for test through the analysis of the test results of the final, re-
fined emissions control system.
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Tool Design Cost
This cost consists of the manpower costs associated with a team
of engineers and draftsmen who produce a set of drawings, including tooling,
required to fabricate a complete emission control system.
Tool Desi qn Time
This time covers the period from completion of final testing until
completion of final drawings, ready for production.
Tool Procurement Cost
This cost assumes special tooling and/or equipment is required
in order for the given emission control method to be produced at a rate
equal to that required. It is recognized that the production rate and
resulting cost depends upon the number of engines in use and the current
or projected engine production rate.
Tool Procurement Time
This time covers the period from the completion of final
drawings until all tooling and/or equipment required is available for
initiation of production of the specific engine control system components.
Total Development Cost
This cost is initially found as the cost per engine family (JT8D)
and is the summation of all the cost elements previously listed, including
engineering development, testing, tooling design, and tooling procurement.
Total development costs per engine family were assumed to vary among the
several emission control methods considered, but were assumed to be equal
for a given control method applied to various engine families in the same
engine class. The number of engine families in a given class is used to
get the final development cost for that class. It is recognized that the
cost of the test hardware and test facility operating costs will vary with
engine size (or class) but differences are assumed negligible for the analysis,
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Total Development Time
This time is the summation of all the time elements previously
1 isted, as above.
Total development times were assumed to vary among the several
emission control methods considered, but were assumed to be equal for a
given control method applied to various engine families in the same engine
class and also in different engine classes.
A summary of these costs and times for both turbine and piston
engines is presented in Tables 15 through 18 for the various appropriate
emission control methods.
Implementation (Retrofitting) Cost and Time Analysis
The term "implementation cost" as used herein applies to those
cost elements involved in the incorporation of a developed control system
into a specific engine which is currently "in-use". This implies a retrofit
operation. The cost can be expressed as a total cost per engine or as
a total cost when multiplied by the total number of engines affected. The
latter value is assumed to be the total implementation cost, unless other-
wise specified. The implementation analysis assumes that control systems
will be incorporated on an "overhaul" basis, as defined in Reference 2, and
two and one-half years is assumed for an "implementation time" for the
JT8D, used as a baseline engine in the sample calculation.
The "implementation" cost and time elements which were treated
for each control method are described-below. As with the development costs
and time calculations, the procedures for calculating implementation costs
and times are illustrated by means of tables which contain sample calcula-
tions for the same class T2 engines for which the JT8D is still the "base-
line" engine. The sample calculations are found in Tables 19 through 22
and again show results for only the one class of T2 engines. The scaling
factor previously mentioned and explained later is used to obtain costs
for other engine classes, where applicable. Since there is only one piston
engine class, no scaling relationship is required for piston engines. Again,
a study of Figures 6 through 10 should clarify the procedures used.
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Lost Service Life Cost Per Engine
Since "implementation" was assumed to be on an overhaul basis,
as defined in Reference 2, the cost of replacement would include the cost
associated with the remaining service life of the original combustors.
On the average, the unused service life was assumed to be 2500 hours for
the JT8D, or one-fourth the total combustor life. The corresponding
cost would be one-fourth of the original cost of the combustors or
approximately $2500 per engine in the sample case of the JT80.
Initial Additional Installation Cost Per Engine
This cost includes the additional manpower and equipment costs,
if any, per engine involved in the installation of a given emission control
system into a specific engine. For example, it was estimated that the
cost of installing a "minor" combustion chamber modification (control
method t.) into a JT8D engine would be $2000, per Reference 2.
Continuing Additional Cost Per Engine Per Year
This cost is associated with the increased cost of combustion
system components and their (probable) reduced service life. As an
example, this cost for a "minor" combustion chamber modification on the
JT8D engine was calculated to be $2500 per engine per year , assuming
a service life of. 5000 hours or two years of service reduced from the
current assumed combustor service life of 10,000 hours or k years of
service. The increased list price of the combustion chamber components
was estimated to be $11,000 compared to a current approximate price of
$10,500. Actual prices vary as a function of the quantity of the combustors
ordered by an operator and also as a function of the annual inflationary
Assuming that on the average, aircraft operators pay 8? per cent of list
price, increased yearly cost is
new cost/set _ old cost/set
cost/engine = 0.8? service life service life
$11.000 _ $10.500
= 0.87 2 years k years = $2500 per year
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kk
spiral, neither of which effects has been specifically included in this
analysis. The assumed reduction in service life for modified combustors
is consistent with the conclusions of Reference 2, based on aircraft
operators experience. Although modified combustor service life has not
been established yet, even for the JT8D, it seems reasonable that any
modifications to a highly developed component such as the combustor will
introduce some initial difficulties, the end result of which is a
reduction in service life or a loss in reliability. The solution to the
problem is another phase of development, not included elsewhere in this
analysis. The validity of the assumed values for reduced service life
is unknown at this time but the need to include this cost element in the
analysis certainly seems valid.
Total Implementation Cost Per Engine
This cost is the summation of the three previously listed
cost elements. Note that the units of the "continuing additional cost
per engine per year" requires that some time span must be introduced
in order that the units be consistent with the other cost elements and
the resulting summation legitimate. Since the period of interest for
this program has been stated to be the 10 year span from 1970 to 1980,
10 years has been assumed for a time span, henceforth referred to as
"engine life". This 10 year span has no necessary relationship to the
actual useful life of either turbine or piston engines. A cost/time
model was established for purposes of consistency, as shown in Figure 5,
which assumes a finite engine life as explained above and a time
between overhauls (TBO). In the sample baseline case of the JT8D engine,
5000 hours or 2 1/2 years was assumed for the time between overhauls
(TBO) and an engine life of 10 years was also assumed. This results
in a total implementation cost per engine of $35,500 for the 10 year assumed
life of the engine. Similar assumptions were made for the piston engine
analysis, as shown in Figure 5-
Total Implementation Cost
This total cost is established from the previously described
implementation cost per engine by multiplying that unit cost by the number
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of engines in the given class of turbine engines. The number of turbine
Class T2 engines is projected to be 35,87*+ which means that the total
implementation cost will be 35,87^ x $35,500 per engine or 1275 million
dollars for that class of engines for the assumed 10 year engine life
and 2 1/2 year assumed value for TBO. Sample calculations of total
implementations costs for both turbine and piston engines are provided
in Tables 19 and 21.
Total Implementation Time
As previously stated, implementation was assumed to be on an
overhaul basis which results in an average value of two and one-half years
to completely convert all engines in a given fam.i ly of turbine engines in
use.
A summary of the implementation costs and times for bn«-h
turbine and piston engines is presented in Tables 19 through 21 for
the various appropriate emission control methods. The principal guidance
for distributing costs and times among the various emission control methods,
relative to the .initial t. case presented here and in Reference 2 for the
JT80, was obtained in References 20 through 2**.
Total Development and Implementation Cost and Time Analysis
Having established the costs and times associated with the sample
case of the JT8D engine, and the T2 engine class, of which it is a member,
the analysis procedure used to obtain'cost and time data for the entire
aircraft engine population is illustrated graphically in Figure 6. It can
be seen from Table 7 that the JT8D is a Class T2 turbine engine and that
there are 20 engine "families" in that class which also includes a total
number of 35,87^ engines. Assuming that the JT8D engine family is
representative of all engine families in the Class T2 turbine group, total
Class T2 turbine engine development costs are obtained by multiplying the
JT80 baseline development cost by 20 as in Table 15 and the total Class
T2 turbine engine impelmentation cost is obtained by multiplying the JT8D
baseline total impelmentation cost per engine by 35,87*1, as in Table 19-
It is assumed that both development and implementation times as a function
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of emission control methods for the JT8D engine are equal for all other
engine families in the T2 class and in the other turbine classes. Similar
assumptions are made for the piston engine families, as tabulated in
Table 8.
Extending the results of the JT8D baseline case to all "families"
in the Class T2 turbine group results in a simple table, as illustrated in
Figure 6, of total cost and total time for all Class T2 turbine engines,
for each emission control method, covering the period from initial engineering
development through the conversion of the last engine "currently" in use
at the end of the overhaul period assumed.
Cost Scaling Factor
Using the analysis described above, a table of total costs and
total times for one class (T2) of turbine engines has been explained. To
arrive at comparable tables for other classes of engines, as suggested in
Figure 6, it is necessary to repeat the analysis for other "baseline"
engine families in the other engine classes or to establish a scaling re-
lationship which can be used to obtain tables of costs and times for the
other engine classes. The latter approach has been selected.
Technical Scaling Parameter
Considerable effort has been devoted to trying to correlate
aircraft turbine engine cost with technology, which includes both size
and performance. -An example of this effort is provided in Reference 25.
Since both size and performance are involved in the turbine engine clas-
sification system adopted in this analysis, the combination technical
parameter presented in Reference 25 seemed appropriate and in fact provides
a' reasonable scaling relation as shown in Table 23 and Figure 11.
Final Scaling Parameter
A cost variation proportional to the square root of engine
thrust (or equivalent horsepower) was suggested and investigated with
results also shown in Table 23 and Figure 11. The simplicity of this
scaling parameter is appealing and since it appears to correlate very
well with the technical scaling parameter, its use was adopted for this analysis
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Final Scaling Factor
As suggested in Figure 6, simple tables of costs and times are
required for all three turbine engine classes, of which only the Class T2
engines have been explained, using the JT8D engine as a baseline example.
Baseline engines for the other two turbine classes were selected for
scaling purposes, based generally on population, as shown in Table 7 and
1 is ted below:
Turbine Class Baseli ne Enqi ne
Tl T53
T2 JT80
T3 TF39
Calculation of both the technical and final scaling parameters and normali-
zation of the parameters relative to the JT8D baseline engine case, yields
normalized final scaling factors as shown in Table 23. The scaling
factors used were 0.35, 1.00, and 1.6*+ for the Class Tl, T2, and T3
turbine engine classes, respectively. These factors are applied to the
total implementation cost per engine only, based on the assumption that
development costs are essentially independent of turbine engine class.
Again, reference to Figures 6 through 10 should aid in understanding the
procedures used.
Final Cost and Time Results for Current Engines in Service
The final results of this analysis are presented in Tables 2*+ through
27 for both turbine and piston engines- now in service. The tabulation includes
the engine classification, the baseline engine assumed, the emission control
method, the number of engine families in a given.engine class, the number
of total engines in a given engine class, the total development and imple-
mentation cost for a given engine class, and the total development and
implementation time for a given engine class. The latter two values of
total cost and total time are presented for engine classes as a function
of the several control methods selected. Costs are further broken down
to show air carrier, general aviation, civil aviation and military aviation
costs in addition to total costs for both turbine and piston engines. The
result of Tables 2k and 25 are shown graphically in Figures 6 through 10.
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Total Implementation Cost/Enqine^. for "Production" Engines
The analysis and results presented thus far, for both turbine and
piston engines, apply to engine models and populations now in existence
and assume emission controls will be developed and implemented on an
overhaul basis, as previously explained. Certain of these engines will
still be in production at the end of the development period and the
"implementation" costs associated with production engines must be
treated differently from engines currently in service and requiring
a retrofit of the developed control systems. Implementation costs were
analyzed for production engines on a basis similar to that presented
previously. However, the cost associated with the useful life remaining
in a discarded combustor system cannot be included and it is assumed
that the additional installation cost, if any exists, associated with the
new emission control system will certainly be lower than that for a
retrofitted engine now in service. The continuing additional cost per
engine per year was assumed to be the same as for a retrofitted engine and
10 years was again used as a value for "engine life" in order to have the
cost results on a comparable basis. Since future engine production
values are unknown, results are presented on the basis of a 10 year imple-
mentation cost per engine. A "sample calculation" for both turbine and
piston engines is presented in Tables 28 and 29, respectively. These
resul.ts can be compared with those presented in tables 19 and 21 and are
somewhat lower, which seems reasonable. Final results for all classes of
engines, including the three turbine classes, is presented in Table 30-
As indicated, the same scaling factors previously presented have been
used for the turbine engine classes.
Control Methods Applicable to Future Engines
Intensified interest in controlling emissions from aircraft turbine
engi.nes has already stimulated research on combustors for the next engine
generation. Current combustor design practices are recognized to offer
only limited emission reduction. In late 1968, the National Academy of
Engineering recommended government support for the development of com-
bustors using variable geometry and air atomization fuel injectors (Ref 29).
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The advantage lies in controlling local combustion zone fuel-air ratios
over the entire operating range. This departure from current design practice
does not represent a new concept, but rather a method for achieving low
emissions from the current design concept.
A more radical suggestion for reducing emissions in the next
generation of engines is a new design concept - viz, the use of staged-
combustion (Ref 16). The idea is to introduce a series of separate com-
bustion zones with independently controlled fuel injection in each zone.
Air atomization fuel injection would be used in all zones. Again the
objective is to maintain control of local fuel-air ratios over a wide
operating range of the combustor. Several fluid dynamic and combustion
problems must be solved before staged-combust ion becomes workable. The
only serious development problems in the case of variable geometry center
on the added mechanical and control system complexity.
Reduced emissions is not the only factor.promoting development
of more complicated combustors for the next engine generation. Better control
of the mixture can also provide more uniform turbine inlet temperature
profiles. As turbine inlet temperatures increase with the next generation;
more uniform profiles over the entire flight map may be a definite require-
ment for practical thermomechanical design of cooled turbines. The
feasibility of advanced combustors for reduced emissions should be assessed
with th i s in mi nd.
Basis for the Cost and Time Estimates
Either of the control methods applicable to future engines will
require development of new combustors. In the past, the development of ad-
vanced component design concepts has to a large extent been supported by
the federal government - by NASA or by the military. Indeed, the USAF
ATEGG type program might be ideal for developing variable geometry or staged-
injection combustors. Even after the technology is established, however,
each new engine requires separate additional development of its components.
The total development cost for an advanced combustor is thus a somewhat
misleading figure when assessing the practicality of emission control
methods. New combustors will be developed regardless of emission requirements,
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50
The number of interest is rather the incremental cost which will result
if emission criteria necessitate variable geometry or staged-combustion.
The cost and time for developing demonstrator combustors using variable
geometry or staged-combustion are estimated below. Also estimated are
the fractions of the total cost and time which will result from emissions
control rather than from normal evolution of advanced combustors for new
engines. The development costs and times are broken down into design
and testing categories in the same manner as in the preceding treatment
of control methods for current engines. An additional category, per-
taining to incorporation of prototype combustors into engines covers
the effort required to integrate the combustor with other components.
There is a second approach to assessing the cost of emission
control in future engines - viz, the incremental increase in engine
purchase price which results from more complicated combustors. Hardware
and assembly costs will increase with added design complexity. Total
engine costs vary radically with parameters unrelated to combustion (e.g.,
airflow and weight). For this reason, the incremental costs of emission
control in future engines are best defined in terms of the percentage
of the total engine cost associated with the combustor. In the JT8D the
combustor represents roughly U.5 per cent of the engine cost (from Ref 2,
assuming 11K for the combustor and 250K for the engine). The combustor
costs as a per cent of the engine price are included in Table 31, both
for variable geometry and for staged-combustion.
,ln sum, then, three cost numbers are provided: advanced proto-
type combustor development cost; fraction of development cost associated
with emission control; and fraction of engine purchase price associated
with different combustor concepts. All raw cost numbers assume an engine
size essentially the same as the JT80.
Discussion of Results
The various cost and time numbers for conventional combustors,
for combustors incorporating variable geometry, and for staged-injection
combustors are summarized in Table 31« The discussion below examines the
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advantages and disadvantages of each emission control method for future
eng i nes.
Variable Geometry Combustors
Since variable geometry combustors using air atomization fuel
injectors were recommended in 1968 by the National Academy of Engineering,
it seems safe to assume that development efforts are already underway.
Air atomization fuel injectors are not expected to cost more than con-
ventional injectors once production levels are reached (Ref 30). The
major cost lies rather in the added mechanical complexity of a combustor
with hot moving parts and in the need for an actuation and control system
to vary the geometry during engine operation. Any gains in engine per-
formance or in turbine weight (as a result of better inlet temperature
profile) will at least be offset by the additional weight of the variable
geometry combustor. The incremental cost and time associated with
introducing this type of combustor in future engines consists primarily
of the development and manufacturing problem of varying the geometry.
As indicated in Table 31, the design effort required by
variable geometry is estimated to be twice that of a fixed geometry com-
bustor. This figure assumes a 20 per cent increase in fluid design effort,
a 100 per cent increase in mechanical design, and a control design effort
comparable to the customary mechanical design effort. The increased
cost of prototype hardware represents first, higher tolerances on critical
varying geometry parts and second, additional actuation and control
components. The increased test costs result first from time spent
optimizing the geometry at various operating conditions and second from
anticipated mechanical problems in actuating geometry changes during opera-
tion. The additional engineering effort required to incorporate a pro-
totype variable geometry combustor into an engine results from added control
system complexity.
The purchase cost of a variable geometry combustor using air
atomization fuel injectors is expected to be about twice that of a comparable
fixed geometry combustor. The combustor hardware cost should increase by
50 per cent, and the rest of the additional cost stems from the actuation
and control hardware.
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52
Since no new combustion concepts are involved with the variable
geometry combustor, the essential engineering problem is to design an
actuation and control system which is compatible with the rest of the
engine. The only other issue is assuming adequate life of more critically
designed parts. The development time estimated for a prototype combustor
of this type reflects these considerations.
Staged-Injection Combustors
Staged-combustion is a more radical departure from current com-
bustor design practice. The problem with variable geometry is to implement
a concept which will surely work from a combustor performance standpoint.
The problem with staged-injection is to develop and to prove the concept
itself. Several combustor performance difficulties are anticipated. These
are best understood by describing the concept in slightly more detail.
One approach to staged-injection uses two air atomization injec-
^ors where one is used now. One of these fuels a pilot burner, and the
other introduces the major part of the design fuel flow into a prechamber.
Fuel is premixed and vaporized in this prechamber before entering the
combustor proper. A serious technical problem is the danger of flash-back
into the prechamber. High gas velocities are needed in the prechamber for
mixing, and a considerable pressure drop is needed between the prechamber
and combustor proper to prevent flash-back. Careful fluid dynamic design
of a more complicated network is needed if pressure losses are to be
acceptable. On the other hand, the flexibility provided by a pair of
injectors should improve combustor flame stability.
The costs shown in Table 31 for the staged-injection combustor
reflect the need for technological development of the concept. The much
larger engineering design and test effort indicated will be devoted to com-
bustor rig exploratory development programs. Different arrangements of
the prechamber and pilot will require examination with particular attention
to a fluid dynamic design which will provide adequate prechamber mi-xing,
low pressure losses, and no flash-back problems. Once an acceptable pro-
totype staged-injection combustor is obtained, it can more readily and
less expensively be incorporated into an engine as compared to the variable
geometry combustor. No actuation or complicated control system is needed -
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53
only two fuel lines with separate controls of the type currently used in
zoned afterburners. Compressor diffuser designs will, however, doubtlessly
requ i re revis ion.
The production cost of staged-combustion is greater than that of
conventional designs first, because twice as many fuel injectors are needed
and second, because the structural design must provide a more complicated
flow.path. However, staged-combustion, once developed, should offer a
noticeable cost savings versus variable geometry.
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EFFECTIVENESS OF CONTROL METHODS:
GROUND OPERATIONS MODIFICATIONS
Introduction
This section of the report examines how effective seven sug-
gested ground operations changes would be in reducing aircraft emissions.
The next section will evaluate the cost and time for implementing the
changes. The suggested changes are:
1. Increase engine idle RPM.
2. Use a minimal number of engines for taxi operations and
increase the idle RPM of the engines used.
3» Minimize unnecessary engine time by a system for controlling
engine start and gate departure.
k. Minimize taxi time by parking aircraft near runways and
using auxiliary vehicles to transport passengers to and
from the terminal.
5. Tow aircraft between runway areas and the terminal, thus
eliminating the taxi mode of engine operation.
6. Provide ground-based auxiliary power supply in order to elimi-
nate use of on-board auxiliary supply units while at the gate.
7. Provide auxiliary equipment for emptying fuel drainage
reservoirs.
The effectiveness of the various changes in reducing aircraft emissions has
been evaluated for a single representative airport, Los Angeles International
Airport. Each of the seven changes is discussed separately below.
Control Method Effectiveness
Increase Engine Idle RPM
Two categories of turbine engine emissions, carbon monoxide and
hydrocarbons, result from incomplete combustion. This occurs primarily at
low engine power settings because the combustor is optimally configured
for full power operation. By operating engines nearer the combustor de-
sign condition, the emission rates for CO and hydrocarbons will be reduced.
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Aircraft braking power and brake wear ultimately constrain the extent
to which the idle RPM can be increased. Brake overheating already oc-
curs occasional ly dur.ing ground operation.
Essentially a doubling of engine power was assumed to get a
benchmark for the effectiveness of a higher idle in reducing emissions.
Figure 12 approximates the relationship between power and fuel flow.
Although this approximation cannot be extrapolated to zero power output,
.it suffices for estimating emission reduction with idle power setting
change. Figures 13 and 14 give CO and hydrocarbon emission rates versus
engine power setting. Figures 12 through \k thus supply sufficient in-
formation to calculate the per cent emission reduction which results from
doubling the power during aircraft idle.
Table 32 summarizes the reduction in engine emissions which
results from doubling idle power output. The table also indicates the
uncontrolled emission rates for each engine and the number of engines in
each aircraft class (as per Ref 6). Although increasing the idle RPM re-
duces emissions per unit mass of fuel, increased fuel flow can offset the
improvement (as in the case of hydrocarbons for Class 2 aircraft). Thus
the full benefit of increased idle RPM will be realized only if not all
engines are in use during ground operations.
Uj>e Minimal Number of Engines
at Increased Idle RPM
Thrust levels for taxi can be kept the same by using less than
the full complement of engines, but at a higher power output level. Again
the benefit will be in reducing carbon monoxide and hydrocarbon emissions
which occur predominately at low power settings. Using fewer engines (and
less fuel) per aircraft during ground operations will also provide an
across-the-board cut in emissions. Implementation of such a change is
straightforward with the sole exception of requiring fire-safety pro-
visions at the ends of. runways while departing aircraft are starting
engines. At least one airline currently saves fuel by shutting down the
center engine on arriving Boeing 727 aircraft, while taxiing to the gate.
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The question with this method of controlling emissions at air-
ports is how many engines are minimally needed for taxi. In the extreme
it is possible to taxi with a single engine. This would provide the maxi-
mum reduction in emissions. Airline pilots do not expect that the un-
balanced thrust from single engine taxi of two and four engine aircraft
would be unacceptable; tests are nonetheless needed to confirm the safety
of such operation as a standard procedure. A more serious factor milita-
ting against use of a single engine is the power level which would be re-
quired to resume taxi after the aircraft comes to a complete stop. With
fully loaded aircraft on slight grades a 100 per cent power output from
a single engine may well be necessary to resume taxi. The hazardous jet
blast area would have to be extended from a current value of 150 feet to
more than kQO feet. The ramifications of the increased jet blast might
require substantial modification of airport taxi procedures and rules.
The extent to which the number of engines used during taxi can
be reduced thus remains unclear. For this reason two sets of reduced.
emission numbers have been derived: one assuming single engine opera-
tion and the other, two engine operation for all commercial aircraft.
Table 33 summarizes the reduction in emissions which would result if only
one or two engines were operating (at a higher power level) during taxi.
The reductions for the taxi mode are substantial-- particularly if single
engine taxi proves to be acceptable. As discussed in the next section of
the report, the savings in fuel from single engine taxi operation would
surely be attractive to the airlines.
Controlled Engine Start-Up and Gate Departure
The idea is to restrict engine operation while the aircraft is
on the ground to that required for taxi. The engines would be shut down
at the gate. They would be started under the direction of a ground traf-
fic control system which, among other things, would eliminate delays at
the end of the runway. Such an airport ground traffic control system offers
many evident advantages besides reduced emissions. However, several factors
militate against its implementation. The traffic control system would have
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to be extremely complex if current runway utilization levels are to be
maintained. Moreover, a prime reason for current delays at th'e end of
the runway is the unavailability of gates for arriving aircraft. Air-
lines di spatch aircraft simply to open a gate, regardless of how soon
clearance for take-off will be granted. Thus either more gates, or an
intermediate parking area for departing aircraft, or more uniformly
scheduled traffic levels would be necessary to implement this ground
operation change. Nevertheless the orderly growth of air transport
operation will doubtlessly require automated ground control to maximize
airport utilization. Thus this method for reducing emissions is likely
to appear increasingly practical with time.
This control method will eliminate delay mode emissions, as
defined in Reference 6. In the case of Los Angeles International Air-
port mode times are as follows:
Mode Time
Taxi 12 minutes
Delay 112 seconds
Maintenance 69 seconds at idle power
23 seconds at cruise power
Table 3^ summarizes the aircraft emissions at Los Angeles Airport
which result from each mode of ground operation. Table 35 gives the
reduction of the emissions achievable by eliminating the delay mode.
Carbon monoxide and hydrocarbon levels at Los Angeles Airport can be re-
duced by about 10 per cent. At other airports, where the delay mode
represents a larger fraction of ground operation time, the reduction can
be more dramatic.
Intermediate Passenger Transportation
From the point of view of emissions the use of lounges for
transporting passengers to and from aircraft is attractive only if the
aircraft can be parked near the runway to be used. Otherwise taxi times
.would not be markedly reduced from those of current operation. Ideally
aircraft parking areas would be located adjacent to the runways, midway
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along their length. Even then the minimum taxi time will correspond
to the runway length, which is not a substantial reduction over current
taxi times. Moreover., practical safety requirements will increase the
taxi distance since parked aircraft should not be exposed to the hazards
of landing aircraft.
The general conclusion, then, is that modifying existing airports
to use intermediate passenger transportation between the terminal and an
aircraft staging area is unlikely to reduce aircraft emissions. The stag-
ing area at Dulles International Airport, for example, is no closer on the
average to the ends of the runways than is the terminal. Introducing a
staging area for each individual runway at existing airports is scarcely
feasible since land shortage is already a problem at most. New airports
designed to stage aircraft in the vicinity of runways might show some
advantage in emissions, but the advantage would be slight. Current air-
port design practices already attempt to locate the terminal to minimize
taxi times, commensurate with safety. Even should lounges be pollution-
free, then, it is doubtful that airport emissions will improve with the
mobile lounge type of operation.
Towing of Aircraft
•Using auxiliary vehicles to tow aircraft around airports will
dispense with aircraft emissions from the taxi mode altogether. Tow
tractors would be used not only to move the aircraft clear of the gate,
but then to tow.the aircraft to a staging area at the end of the runway.
Once clearance is granted, engines would be started at the staging area.
Arriving aircraft would correspondingly shut down engines at the end of
the runway and would then be towed into the gate. This type of operation
has on occasion been contemplated in the past because of concern with
jet blast and aircraft maneuverability (for example, by Pan American dur-
ing the advent of turbojet powered commercial aircraft). The crucial dis-
advantage stems from a'maximum speed capability of below 10 miles per hour
for current tow vehicles. Since taxi times would more than double, towing
aircraft around airports would require radical revisions of airport pro-
cedures and of airline schedules.
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The effectiveness of towing in reducing airport emissions in-
volves a trade-off between reduced aircraft and increased tow vehicle
emissions. The trade-off is defined on the basis of kilometers travelled,
assuming an aircraft taxi speed of 17.5 kilometers per hour. The values
of aircraft emissions for the taxi mode (as per Ref 6) are given in Table
36. This table also indicates values for diesel powered tow vehicles ob-
tained from Reference 31; tractors are assumed to use 17 litres per kilo-
meter. Comparison of aircraft and tow vehicle emissions shows that even if
tractors were required to do a double journey, there would be substantial
reductions of carbon monoxide and hydrocarbons for most of the aircraft
classes. However, NOx emissions might increase to an unacceptable level.
Table 37 shows the effect of eliminating the taxi mode emissions
entirely. These values should be taken in conjunction with those of Table
36 to obtain the actual reduction from using tractors.
Use Ground-Based Auxiliary Power Equipment
There are two ways in which on-board auxiliary power units could
be eliminated from use while at the gate: by using portable electric and
air supplies or by equipping each gate with a centrally supplied air and
electric system. The latter method is of limited practicality except pos-
sibly for a newly designed airport. Mobile units are more feasible with
exi sting ai rports.
The emissions for on-board auxiliary power units are given in
Table 38. They are based on those for turboprop engines at take-off
conditions (Ref 6), scaled according to fuel flow rate. API) operating
details have been obtained from an information sheet on the GTCP-85, pub-
lished by Garrett, and from Reference 11.
Table 38 also gives the reduction in emissions which would re-
sult from eliminating the use of on-board auxiliary power units. The re-
duction is essentially negligible.
Use Auxiliary Equipment for Emptying Fuel Drainage Reservoirs
Fuel which collects in the engine drainage reservoirs is cur-
rently dumped as part of the take-off procedure. The emission levels
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associated with this operation at Los Angeles International Airport are
indicated in Table 2**. A demonstration is being held on August 18, 1971,
of an auxiliary device which extracts and stores the fuel in the drainage
reservoirs prior to aircraft take-off. This device is assumed to be 100
per cent effective from the point of view of emissions. Thus, all emis-
sions from fuel dumping shown in Table 24 would be eliminated by imple-
menting this ground operation control procedure.
Conclusions
Table 39 summarizes the reductions in carbon monoxide and hydro-
carbon emissions which would result at Los Angeles International Airport
from the seven suggested ground operation changes. The distribution of
activity among aircraft classes (Ref 6) for the first two control methods
has been taken as follows:
Aircraft Class Per Cent
2 3
3 56
4 22
5 6
6 13
Pollutants other than CO and hydrocarbons appear to be less affected,
although NOx emissions may increase with the use of tractors to tow air-
craft. By combining minimal number of engines with controlled departure
to eliminate runway delays, a substantial reduction in emissions can be
achieved— indeed a reduction at least comparable to the use of tow
vehicles. Use of passenger lounges and avoidance of using on-board APU's
offer no advantages in reducing emissions. The maximum effect obtainable
by combining the various control methods is a reduction of emissions to
about 50 per cent of their uncontrolled level for this airport, assuming
two engine taxi; and to about 40 per cent, assuming single engine taxi.
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IMPLEMENTATION COSTS AND TIMES OF CONTROL
METHODS:GROUND OPERATIONS MODIFICATIONS
This section of the report presents estimates of the costs and
times required for implementing various ground operation changes to con-
trol aircraft emissions. Constraints on feasibility which are difficult
to assess in terms of time and money required for implementation are also
reviewed. The effectiveness of the different ground operation changes in
controlling emissions is discussed in the preceding section. Attention
here is confined to the feasibility of the changes independently of their
effectiveness. Seven operation changes are examined:
1. Increase engine idle RPM.
2. Use minimal engines for ground operations and increase the
idle rpm of these engines.
3. Reduce unnecessary engine time by a system for controlling
engine start and gate departure.
k. Reduce taxi time by parking aircraft near runways and using
auxiliary vehicles to transport passengers to and from the
terminal.
5. Minimize engine time by towing aircraft between runway areas
and the terminal.
6. Provide ground-based auxiliary power supply in order to
eliminate use of on-board auxiliary supply units while at
the gate.
7. Use auxiliary equipment for emptying the fuel drainage
reservoirs of each engine.
Time and cost estimates have been made for a single representative airport,
Los Angeles International Airport. Costs will necessarily vary from air-
port to airport. The basis, for making the estimates is accordingly dis-
cussed so that comparable numbers for other airports can be derived.
Basis for Estimates
The fundamental assumption made in evaluating the feasibility of
the seven ground operation changes is that current operation levels at
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Los Angeles International Airport remain in effect. Specifically, the
peak hour load was assumed to be 120 operations involving 10,000 passen-
gers. LA currently has 77 gates, but some of these must be paired when
servicing Boeing 7^7 aircraft. It was therefore assumed that servicing
facilities for 75 aircraft must be available at any one time-- either
gates or parking facilities. Five categories of cost have been distin-
guished: land, construction, equipment, automation procedures, and op-
erating. Each of these is defined and the ground rules for deriving
numbers are described below. The bases for the cost estimates for each
operation change are summarized in Table **0.
Additional land purchase is needed for those ground operation
changes which require aircraft parking facilities other than those at
the terminal. Space required for servicing varies from aircraft to air-
craft, and provision for maneuver must be made. For estimation purposes,
an aircraft was assumed to require an average of 1.2 acres of parking space.
Land purchase prices in the vicinity of airports vary widely. A represen-
tative price of $50,000 per acre was assumed in this study, which corres-
ponds to assessed valuation in the vicinity of Logan International Airport
in Boston.
Two types of construction costs can be incurred in implementing
ground operation modifications: additions or alterations to the terminal
facility and additional taxiway and aircraft parking surfaces. Terminal
construction costs have been estimated from the costs required to modify
gates when the 7**7 aircraft were introduced. Surface costs have been
predicated on 12 inch thick concrete, at a cost of $500,000 per acre of
surfacing.
Different suggested ground operation changes require purchase of
different types of new equipment. Use of tractors to tow aircraft between
the terminal and the runway areas will require purchase of additional tow
vehicles. At a minimum it was assumed that 80 vehicles would be needed to
service 75 gates at peak load without inconvenience. Airlines currently
maintain about 15 tow vehicles per twenty gates. Thus, about 25 new trac-
tors would be needed at LA International Airport. The price of tractors
varies from $20,000 for one adequate for a Boeing 727 to more than $50,000
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for wide-body aircraft. An average price of $30,000 per tractor was
assumed.
Use of lounges to transport passengers between the terminal
'and the aircraft will require purchase of lounges. At Dulles Inter-
national Airport lounges costing over $200,000 can transport 110 passen-
gers at a time. One such lounge per gate should more than suffice for
peak hour loads at LA International.
Mobile auxiliary power units cost approximately $20,000 for air
supply and $15,000 for electrical supply. Again the availability of one
air supply and one electrical supply unit per gate should suffice for
eliminating use of on-board auxiliary power units on the ground. It was
assumed that currently only 50 per cent of this requirement is satisfied.
To empty at the gate the fuel which collects in the fuel drain-
age reservoirs will require purchase of the proper auxiliary equipment.
An FAA demonstration of such a piece of equipment was held on August 18,
1971. This particular design costs $500. LA International Airport would
require 75 of them-- one per gate.
In initiating a complicated ground control system, automation
equipment will be needed— in particular, a computer system with rapid
information through-put capacity and with auxiliary communication equip-
ment between aircraft and control. For estimation purposes an IBM 360-65
computer was assumed as a bench mark.
Initiation of a ground control system will also require the de-
velopment and implementation of automated procedures. If computer control
is to be adopted, programs will have to be developed to provide the computer
with techniques for maintaining control. Programming cost consists pri-
marily of labor at roughly $30 per man hour. Even without a computer con-
trolled ground traffic pattern, new schedules and procedures will be needed
to implement either the use of tow vehicles or passenger lounges. Again a
labor cost of $30 per man hour was assumed.
Various types of operating costs were recognized. Aircraft op-
erating expenses on the ground were estimated on the basis of fuel costs
at idle for JT8D engines. The basic rule is that each engine consumes 1200
Ibs/hr of fuel during idle, at a cost of $48 per hour. Operating enqines
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at an increased idle speed, based on Boeing 727 experience, increases
consumption to 1800 Ibs/hr. Los Angeles International Airport had
JtO.OOO operations during 1970. If it is assumed that the average opera-
tion involved 20 minutes of idle and taxi time and that the average "air-
craft" has 2.7 engines, then the ground fuel consumption at LA alone is
$17,000,000 per year. The cost savings which would result by reducing
aircraft engine ground operation are accordingly of large potential.
These cost savings are in part balanced by the additional costs for labor
and fuel used by auxiliary vehicles. They are also likely to be balanced
by the reduction in total capacity which results when ground operations
require significant increases in time. The assumed incremental operating
costs described below reflect these various considerations.
In estimating the time required to implement each ground opera-
tion change it was assumed that purchase of land and of equipment would
encounter no unusual problems. Construction times and times required for
introducing automation were estimated on the basis of current experience.
Time estimates should be regarded as quite approximate since numerous
social and political factors may interfere with the rapid implementation
of ground operation changes.
Discussion of Results
Table k\ summarizes the costs and times required for implementing
each of the seven considered ground operation changes. Money and time,
however, are not the only factors affecting the feasibility of these changes.
Some changes have advantages other than those associated with aircraft emis-
sion levels, while others involve disadvantages in terms of airport operation
which cannot readily be assessed numerically. For this reason a synopsis of
the method of implementation and the advantages and disadvantages of each of
the seven changes is presented below. Table k2 summarizes the factors which
affect the implementation of the changes. Included in the table are the re-
quirements for implementation, advantages other than emissions, and con-
straints other than time and cost.
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Increase Idle RPM
If all engines were to be operated on the ground at an in-
creased idle RPM, fuel consumption would obviously increase. The in-
creased operating cost shown in Table 41 is predicated on this assump-
tion. The extent to which the idle RPM can increase is constrained by
the capacity of the aircraft brakes— in particular, by the need to avoid
overheating and excessive wear of the brakes. Implementation of an in-
crease in idle RPM requires only a modification of cockpit procedure since
the idle speed is fully under the pilot's control. Thus no prominent
initial costs would occur with implementation.
This control method would probably not be adopted without a cor-
responding reduction in the number of engines operating, so that total air-
craft thrust would remain essentially the same. Brake problems would in
this way be eliminated. The net effect on the operating cost of this com-
bination of control methods, as discussed below, could be a substantial re-
duction in fuel expenditures for ground operations. American Airlines, for
example, cuts Boeing 727 fuel costs on the ground by shutting down the center
engine and by operating the out-board engines at higher output levels.
Reduce Number of Engines During Taxi
and Increase Idle RPM
Total aircraft thrust during ground operations can be maintained
by using fewer engines operating at higher power output levels. Aircraft
emissions would-be reduced on two counts: shut-down engines would produce
no emissions, and engines operating at higher output would produce less
carbon monoxide and hydrocarbon emissions. The change in airport pro-
cedure would call for unnecessary engines to be shut down upon landing and
not to be restarted until at the end of the runway prior to departure.
Whether one or two engines would be necessary for effective ground opera-
tions to be maintained at airports remains an open question. However,
except for an answer to this question, implementation of the change would
not be difficult since no equipment purchase or construction is entailed.
Indeed, the suggested change in effect provides a more efficient method for
achieving ground thrust requirements. Thus reduced fuel consumption would
be a direct consequence.
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The principal constraint on the minima] number of engines
needed is the thrust required to resume taxi once the aircraft comes to
a complete stop. A fully loaded Boeing 727 requires approximately 50 per
cent of take-off power from two engines to resume taxi following a pro-
longed stop on a slight grade. Single engine operation would require a
100 per cent power level. The resulting jet blast along taxiways may prove
hazardous. More space (e.g., in excess of ^00 feet) between aircraft wait-
ing for departure at the end of the runway would doubtlessly be needed with
single engine operation. There is also a question on the safe maneuverability
of two and four engine aircraft taxiing with unbalanced thrust produced by
a single engine. Still, two engine ground operation appears reasonable with
most commercial aircraft, and single engine operation is not out of the ques-
tion. An airport procedure change to provide fire protection equipment and
personnel would be necessary were engines to be started not at the gate, but
at the end of the runway. A slightly more elaborate staging area at the end
of the runway might also be needed at some airports.
The initial costs in implementing this ground operation change
would be negligible. Reduced fuel consumption during ground operations
would yield operating cost savings, as indicated by the negative numbers
in Table k\. In particular, single engine operation would result in a $7-5
million annual cost savings at Los Angeles International Airport, and two
engine operation would result in a $3 million savings. The additional labor
cost for fire protection at the end of the runway is negligible by compari-
.son-- less than one-half million dollars annually at LAX. Implementation of
two engine operation should require little time since all factors other than
fire protection are at the pilot's command. Single engine operation should
await a series of tests to establish its practicality and safety. Since
fuel costs as well as" emission levels show decided gains from using fewer
engines, a more detailed examination of this change is surely merited.
Controlled Gate Departure
The idea'is to restrict engine operation on the ground to that
required for taxi. The engines would be shut down at the gate. They
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would be started under a ground traffic control system which, among other
things, would eliminate delays at the end of the runway. Such an airport
traffic control system offers many evident advantages, but several factors
mi 1i tate against i t.
The fundamental problem centers on the incompatibility of the
times required for arrival and departure procedures if the latter are
initiated from the gate rather than from the end of the runway. The time
required for an aircraft to proceed from a final holding pattern to land-
ing is of the order of magnitude of hundreds of seconds. The time re-
quired for an aircraft to be towed clear of the gate, to start engines, to
taxi to the end of the runway, and to take-off is more of the order of mag-
nitude of thousands of seconds. For example, the average taxi time alone at
LA International Airport is 12 minutes (Ref 6). Moreover, the time from en-
gine start to take-off is not uniform since it depends on the distance from
the gate in question to the runway in use. For a controlled gate departure
procedure to work with current peak load conditions, a complicated computer
based system with automated communication techniques would be needed. The
computer would be programmed on the basis of queuing theory to supply air-
craft at the runway end automatically. The program would take into account
the time required for the aircraft to reach the runway from its gate as well
as the sequence in which permission to start is requested. Contingencies
associated with arrivals, with weather, and with emergencies would be taken
into consideration. Procedures for assuring fair treatment of all airlines
regardless of terminal location and procedures for continuous monitoring
after permission to start, could in principle be introduced. Implementation
of so complicated a ground control system would scarcely be straightforward,
particularly given the current complexity of airport procedures with minimal
ground control.
A second constraint on controlled gate departure is that much of
the current delay at the end of runways results from an insufficient number
of gates. Airlines dispatch aircraft to open a gate for use even though
the aircraft will be unable to take off. Thus, a second requirement for
controlled gate departure is either an increase in the number of gates or a
parking area from which the ground traffic control system would take over.
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For example, aircraft could be towed to the parking area under direction
of .the computer when gate space is needed, but when engine start per-
mission can not yet be granted. Provision for 20 per cent of the gate
capacity for such intermediate parking should suffice except during ex-
traordinary circumstances.
A final constraint on controlled gate departure is the need to
supply electrical power and air conditioning without the use of the air-
craft engines. Boeing 707's, 720's, and McDonnel1-Douglas DC-8's do not
have on-board auxiliary power units, so that ground-based facilities would
be required for these planes.
Introduction of an automated ground control system, as indicated
in Table k], involves substantial effort and expenditures. Were this
ground operation change viewed purely in terms of reduced aircraft emis-
sions, it would be of dubious merit. However, the orderly growth of com-
mercial air transport in the present social climate is likely to require
more effective utilization of existing airports. Automated ground control
would surely provide one step toward improved utilization, though the step
may seem small compared to improved air traffic control. Thus in judging
the costs for controlled gate departure, shown in Table k\, the reader is
encouraged to keep the total airport picture in mind.
Intermediate Passenger Transportation
From the point of view of emissions the use of lounges for trans-
porting passengers to and from the aircraft is attractive only if the air-
craft can be parked near the runway to be used. Otherwise taxi times would
not be markedly reduced from those of current operation. Parking space for
75 aircraft near the runways at LA International is not remotely available.
Safety questions may also discourage locating parking areas near runways.
The large costs associated with modifying an existing airport to this type
of operation result to a dominant extent from the cost of a parking area.
In the case of a new airport this type of operation would appear far more
practical since terminal construction costs can be reduced in far greater
proportion than the cost of the lounges and parkinq space.
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To implement this change at an existing airport requires purchase
of land, construction of parking space near runways, purchase of passenger
transportation vehicles, and possibly some added purchase of aircraft ser-
vice and power supply vehicles. Again either ground-based or on-board
auxiliary power units will have to suffice for air conditioning. Obviously
airline schedules would also require revision. It might bfe competitive on
a cost basis simply to build a new airport using this type of operation.
Nevertheless, from the point of view of emission control the feasibility
of this operation change is contingent upon whether aircraft parking areas
can be made available quite close to runways. Since taxi time correspond-
ing to runway length will at a minimum remain necessary, the gain in emis-
sions will probably not be significant. The operating cost reduction in-
dicated in Table ^1 is predicated on a 50 per cent reduction in taxi and
idle time. A more realistic assumption might be no reduction in taxi and
idle time, in which case the operating cost at LAX would increase by $5
mi 11 ion per year.
Towing of Aircraft
The principal difficulty in towing aircraft between the runway
and the terminal is the substantial time the operation would require. Tow
vehicles are currently limited to 8 miles per hour loaded (15 miles per
hour unloaded); this speed drops off markedly on a grade (Ref 32). Thus
the average time required from the gate until departure at LA International
Airport will increase from \k minutes, to at least 30 minutes. The average
time required for towing into the gate after landing will be around 20
minutes, as compared to a current taxi average of less than 7 minutes. Such
increases in ground time would necessitate revision of airline schedules,
particularly those associated with short-haul and shuttle type flights. Thus
the implementation cost of a towing operation is a minor consideration com-
pared to potential ramifications of the time loss problem. Several man-years
of scheduling effort will be required per airport. Some new aircraft may be
needed to maintain current capacity. There is even the possibility of lost
revenue because, for example, the gate-to-qate time from Los Angeles to S.i".
Francisco will double.
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In assessing the cost of towing aircraft, several assumptions
were made. First, it was assumed that with proper scheduling the increased
ground time could be absorbed in such a way as to avoid loss of revenue to
the airlines. Such scheduling would require larger than normal implementa-
tion labor. A major operating expense would result from increased crew-
hours during towing. It was assumed that for ^00,000 operations at Los
Angeles Airport the crew time would increase by 150,000 hours, at a cost
of $200 per crew hour. When this expense is added to the cost of operating
the tow vehicles, all cost savings associated with aircraft engine fuel con-
sumption are offset.
Implementation of the towing procedure thus requires not only ad-
ditional towing vehicles, but also schedule modifications to allow for more
than a 100 per cent increase in ground taxi times. The alternative of new
tow vehicle designs capable of 30 mile per hour operation is possible, but
it would require the development of a new generation of tow equipment and
the formulation of quite different ground rules for towing safety and re-
liability. Towing would finally require the on-board auxiliary power units
to supply adequate air conditioning throughout the towing period; special
provisions would be needed for those aircraft without on-board auxiliary power
uni ts.
Ground-Based Auxi1iary Power Supply
There are two ways in which on-board auxiliary power units could
be eliminated fromuse while at the gate: by using portable electric and
air supplies or by equipping each gate with a centrally supplied air and
electric system. The latter method is of limited practicality except pos-
sibly for a newly designed airport. With existing airports mobile units
are more feasible. Implementation will require purchase of adequate equip-
ment. From the point of view of over-all ground operation, ignoring emis-
sions, experience with the first generation of jet powered aircraft has led
to the standard use of on-board auxiliary power units. The operational com-
plexities associated with ground-based equipment are well known (Ref 33).
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Auxiliary Equipment to Empty
Fuel Drainage Reservoirs
Equipment has recently been developed for extracting and tempo-
rarily storing the fuel which collects in the engine fuel drainage reser-
voirs (Ref 3^). The device hooks up to each engine in turn, and it would
be used as part of the standard aircraft servicing procedure at the terminal
gate. The devices cost $500 per unit. One per gate should suffice. Thus
at Los Angeles International Airport only a $38,000 expenditure is needed to
eliminate fuel dumping from the take-off procedure. The equipment in ques-
tion is currently being demonstrated. Implementation could proceed quite
rapidly once equipment is purchased and personnel are trained.
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EMISSIONS MEASUREMENT
I ntroduct ion
Reliable methods of measuring pollutant emission rates from
aircraft engines are required to support a program of emission control.
Emission measurements are required to evaluate the effectiveness of
control methods, and specific measurement methods must be incorporated
in emission control standards.
An assessment has been conducted of the state of emission
measurement technology to determine whether measurement techniques are
sufficiently well-advanced to support the development of emission con-
trol methods and the implementation of emission standards for aircraft
engines. The conclusion drawn from this assessment is that current
measurement technology will meet most of the requirements of an emission
control program. Certain measurement techniques are inadequate at present
but development of improved techniques appears to be proceeding at a
satisfactory rate.
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. Analysis instrumentation for determining pollutant con-
centrations in the exhaust gas sample.
Aircraft engine manufacturers and certain government agencies have devoted
substantial effort toward providing for these requirements for emissions
measurements for turbine engines. Representatives of these organization
have formed a committee under the auspices of the Society of Automotive
Engineers, referred to as the SAE E-31 Committee, for the purpose of
defining standard measurement procedures and equipment. This assessment
of turbine engine emissions measurement technology is based to large degree
on the work of the SAE E-31 Committee.
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Less progress has been made in defining measurement technique
specifically applicable to aircraft piston engines. The techniques which
have been developed for automobile engines are applicable in general to
ai rcraft engines.
Test Procedures
Two types of test procedures can be used in measuring emissions
from mobile sources. In the first type, emission rates of all pollutants
of interest are measured at each steady state engine operating condition.
These measured rates are then averaged, with appropriate weighting factors,
to determine the total emissions for a complete operating cycle. In the
second type of procedure, the engine is actually operated through a com-
plete operational cycle and a composite sample is collected and analyzed.
The weighted average emission rate for the operational cycle is obtained
directly. This procedure is more effective for operating cycles which
involve transient operations such as starting and acceleration.
Only the first type of procedure has been used to date with air-
craft engines. Operational cycles which have been defined for aircraft
generally include steady operating conditions only. An additional factor
is that current sampling techniques for turbine engines require long
sampling times to assure that representative samples are obtained. With
this requirement, it is not feasible to obtain composite samples for a
complete operating cycle.
Test procedures for standardized emission measurements should
be based on a sequence of measurements at well-defined, steady operating
conditions. Conditions which affect emission rates should be defined
carefully. These include engine speed and power level, fuel type, inlet
air temperature, pressure, and humidity.
Exhaust Sampling Techniques
Turbine Engines
The primary objective in exhaust gas sampling is obtaining a
representative sample of exhaust gas of a known quantity or at a known
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flow rate. Apparatus used for sampling generally consists of a probe,
sampling line, a flow measuring device, a pump capable of drawing the
desired flow rate through the system, and collection devices for captur-
ing pollutant samples.
Effort is underway to standardize the design of sampling probes
(Ref 35). The SAE E-31 Committee recommends that probes be of stainless
steel with an orifice area such that the principle pressure drop occurs
in the orifice itself. If a mixing probe is to be used, they specify that
all sampling holes be equidiameter (Ref 36). The probe need not be designed
to achieve isokinetic sampling since departures from this condition only
cause errors for particulates whose diameters are greater than 3-5 microns.
Particulate emissions from aircraft engines are primarily less than 1
micron in diameter. As a notable example of this lack of need for isokinetic
sampling, Pratt 5- Whitney (Ref 37) tested an aircraft engine exhaust with
two probes installed back to back: one facing upstream; the other down-
stream. No detectable difference in the smoke density was observed as
measured by the two probes as a function of engine power level. Further,
probe orientation was not critical as long as they were stationed within
the exhaust stream and secondary air had not diffused into the stream.
The SAE E-31 Committee and others (Refs 38 and 39) have found
that multipoint sampling of engine exhausts is necessary (due to wide
spatial variations in stream characteristics) in order to achieve repre-
sentative values of engine emission rates. The SAE therefore recommends
that samples be collected at at least twelve locations at a minimum of
three different radial positions in each of four sampling quadrants. The
location of these twelve points is specified by the E-31 Committee; pro-
cedures are also identified for point location if more than twelve samples
are collected. Either mixing or individual probes are acceptable (Ref 36).
The SAE also recommends that the axial sampling plane be no further than
one exit nozzle diameter from the engine exhaust. However, with after-
burning engines, combust.ion is by no means complete at the engine exit
plane. Champagne (Ref *+0) reports that the Arnold Engineering Development
Center is conducting tests to produce preliminary solutions to this problem;
The E-31 Committee will attempt to write a separate standard for measurement
of emissions from afterburning engines later this year.
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The sampling line, which conveys the gas sample from the probe
to the collection and measurement apparatus, must be designed such that
no changes in sample composition or physical state occur during transit.
The line must therefore be short, of small bore (0.18 to 0.32 in I. 0.,
Ref 36), and be constructed of materials (stainless steel or Teflon)
which do not adsorb or react chemically with pollutant materials (Ref 41).
The line must also allow free passage of particulate matter. As an
illustration of the necessity for these requirements, Reference k2 con-
tains a discussion of the reduction of NOX by CO when catalyzed by certain
metals frequently used in sample lines. In sampling engine exhaust gases,
it is also necessary to maintain the sampling line temperature at a level
at which condensation of organic vapors and water do not occur (about 350
deg F, Ref 36). This requirement is more severe with turbine engines
than with gasoline-fueled piston engines. Turbine engine fuels, which
have higher boi1 ing points than gasoline, give rise to organic emissions
which also have high boiling points. This requirement for heating the
sampling line often is neglected; however, the E-31 Committee has recom-
mended in their test procedure that sample lines be heated to 350 deg F
to minimize this adsorption/desorption phenomenon. At the present time,
line heating is accomplished primarily via electrical heating tapes;
however, their use has been somewhat problematic and heat transfer fluids
may be employed in the future (Ref 43).
The types of pollutant collection devices to be used in a sampl-
ing system depend upon the measuring techniques to be employed. Many
measuring techniques do not require pollutant collection, but indicate
pollutant concentration directly by measuring some property of the gas
sample. These techniques are utilized either by connecting the measuring
device directly to the sampling system, or by collecting a gas sample in
a container (grab sample) and transporting it to the measuring device.
Separate (heated) sample lines may eventually be employed for grab samples
to prevent their upsetting the flow into continuous monitoring equipment
(Ref
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Piston Engines
Sampling techniques for aircraft piston engines are not as
critical as with turbine engines since exhaust gases are thoroughly
mixed when they reach the exhaust stack exit. Also, fewer condensible
vapors are encountered and particulates generally are not measured.
The sampling technique initially proposed by the Department of Health,
Education, and Welfare for automobile emission measurements (Ref 45)
appear to be appropriate for aircraft piston engines.
Instrumentation
Range and Accuracy Requirements
An analysis has been conducted of the range and accuracy of
the instrumentation necessary to measure emission rates of all pollutants
of concern from aircraft engines. Allowance has been made for potential
reductions in emission rates resulting from future equipment modifications.
Pollutants Considered
In a previous .characterization of aircraft engine exhaust gases
(Ref 1), Northern Research and Engineering Corporation indicated that emis-
sions that should be considered for control and measurement should include,
but not be limited to: total organics (hydrocarbons), carbon monoxide,
oxides of nitrogen, sulfur dioxide, carbon dioxide, total particulates,
visible smoke, and odor. Reexamination of the literature (Refs 46 and 47)
shows that species such as peroxyacyl nitrates, olefins, and aromatics
(ingredients in photochemical smog); polynuclear hydrocarbons (potentially
carcinagenic); acrolein (aldehyde) formaldehyde, carbonyls, and unsaturated
hydrocarbons (all apparently related to odor intensity); ozone (oxidant);
lead; and unburned fuel (including drainage) are now often cited as atmo-
spheric contaminants emitted in aircraft engine exhausts. The majority
of these species are, however, emitted in extremely low quantities and at
concentrations below which satisfactory continuous measurement techniques
have been developed. Furthermore, many of these species are constituents
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of emissions which are themselves difficult to measure. As a result,
with the exception of total aldehydes and unburned fuel (including
drainage), these additional species are omitted from this analysis.
Until recently, nitrogen oxides in aircraft engine exhausts
were considered to consist primarily of NO with only trace quantities
of other oxides. Recent measurements (Ref 34) with turbine engines have
revealed, however, that NCL concentrations are not negligible under some
conditions. Thus, two measurements for NO and N02, or a combined measure-
ment for the two species, are required to indicate total NOX emission rate.
Instrumentation Range
Existing data (Refs 1, 3, 37, 41, and 48 through 54) on air-
craft engine exhaust emissions are summarized in Table 43- The column
entitled "Recommended Range" in Table 44 gives the suggested sensitivity
of instrumentation for each pollutant. These ranges reflect emissions
levels of both piston and turbine aircraft now and in the near future
after satisfactory control methods have been established. These ranges
correspond in a large part to the forthcoming recommendations (Ref 36)
of the Society of Automotive Engineers Committee E-31, which as produced
an "Aerospace Recommended Practice" (Ref 55) covering the measurement of
visible smoke from turbine engines under test cell conditions. The absence
of data and specifications for smoke and odor emissions reflects the
specialized nature of these emissions in that they are not measured and
quantified in a conventional manner (Kefs 55 and 56).
Instrument Accuracy
Automated pollution measurement instruments can, in general,
measure specie concentration with an accuracy of + 1 - 2 per cent
(Ref 57). This sensitivity, however, does not reflect the circumstances
under which the instruments are required to operate; that is, it does
not reflect the entire "system" accuracy (Ref 58). Further, these limits
are, in many cases, far more restrictive than practically necessary. The
accuracies recommended in Table 44 therefore reflect the sensitivity which
a given instrument should be required to meet, exclusive of interferences
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from other pollutant species, in characterizing aircraft engine exhausts.
In a majority of cases, these recommendations are consistent with those
proposed by the SAE E-31 Committee (Ref 36).
Instrument Availability
A wide variety of instruments are available for analyzing exhaust
samples from aircraft engines. Broderick (Ref 59) compiled a table of
measurement methods in use by nine organizations that are concerned with
quantification of aircraft emissions. In this study, NREC contacted
several additional organizations to expand and update this analysis.
These organizations are:
1. Air Force Aero Propulsion Laboratory; Captain 0. L. Champagne.
2. Cranfield Institute of Technology; by Dr. R. S. Fletcher of
the NREC staff.
3. Rolls-Royce (Derby); Dr. Brian Edwards.
k. Lockheed-California Company; Mr. E. F. Versaw.
5* Southwest Research Institute; Mr. C. T. Hare.
6. AiResearch Manufacturing Company; Mr. J. M. Haasis.
7. U. S. Department of the Interior, Bureau of Mines; Mr. R. W. Hum.
8. Curtiss-Wright Corporation; Mr. T. P. Gagandize.
Table ^5 is a compilation of the results of Broderick's report and of this
survey. In several cases, organizations use more than one method to deter-
mine a particular constituent; in several cases, organizations do not
measure all of the pollutant species included in the table. The instruments
listed in Table ^5 and alternative instruments are described in the Appendix.
Recommendat i ons
CO and CO-2
NREC concurs with the recommendations of the SAE E-31 Committee
(Ref 36) and recommends the use of NDIR instrumentation for monitoring CO
and CO.. Low level emissions should be measured with supplemental instru-
mentation such as small gas chromatographs.
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Total Hydrocarbons
NREC concurs with the recommendations of the SAE E-31 Committee
(Ref 36) and recommends the use of FID instrumentation for monitoring total
hydrocarbons. Low level emissions should be measured with supplemental
instrumentation such as small gas chromatographs. Hydrocarbon distribution
should be determined with gas chromatographs.
Oxides of Nitrogen (NO and NOj
NREC concurs partially with the recommendations of the SAE E-31
Committee and recommends the use of NDUV instrumentation for monitoring
NO^. However, chemiluminescence monitors are recommended for monitoring
NO because of their greater accuracy at low NO concentrations.
19-2
NREC recommends that SO. emissions be calculated from the sulfur
content of the fuel rather than measured by any type of instrumentation.
If a measurement program is selected, the West-Gaeke wet chemical procedure
is recommended. "Faristors" are not reconmended at this time, as they have
not yet been field tested in an aircraft emissions program.
Aldehydes
NREC recommends that the 3-MBTH wet chemical procedure be employed
for measurement of total aliphatic aldehydes. Formaldehyde should be deter-
mined by the chromotropic acid procedure and acrolein by the 4-hexylresorcinol
method.
Particulates
No instrument can be recommended at present for measuring mass
emission rates of either dry or total particulates. Filtration or
impingement techniques are not sufficiently sensitive to measure partic-
ulate concentrations in current engines. Until suitable instruments are
developed, approximate indications of dry particulate emission rates can
be obtained from correlations with smoke measurements.
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Smoke
Smoke should be measured according to the procedures (and
forthcoming sampling modifications) recommended in the SAE ARP-1179
(Ref 55).
Odor
NREC makes no recommendations for .odor measurement other than
suggesting that dilution thresholds be determined for aircraft exhausts
by means of human odor panels.
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83
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-------
86
7**. Groth, R. H. and Calabro, D. S. , "Evaluation of Saltzman and Phenoldi-
sulfonic Acid Methods for Determining NOx in Engine Exhaust Gases",
J. of the Air Pollut. Control Assn^. vol. 19, no. 11, November, 1969.
75. Saltzman, B. E. , "Color imetric Microdeterminat ion of Nitrogen Dioxide
in the Atmosphere", Anal. Chem. , vol. 26, no. 12, December,
76. Ganz, G. and Kuznetsou, I., "Automatic Gas Analyzer for Oxides of
Nitrogen", Ind. Lab. ( I L No. 1), vol. 33, 1967,, pp. 126-128.
77- Private Communication, Dr. M. Shaw, Envi ronmentr ics Inc., Marina
del Rey, Calif., 1971.
78. Fontijn, A., Sabadell, A. J. , and Ronco, R. J. , "Homogeneous
Chemi luminescent Measurement of Nitric Oxide with Ozone, Implications
for Continuous Selective Monitoring of Gaseous Air Pollutants",
Anal. Chem.. vol. kl, no. 6, May, 1970, pp. 575-579-
79« Tommerdahl, J. B. , Ozone Chemi luminescent Study. Final Report. Part I.
Research Triangle Institute, Research Park, N. C. , December, 1969.
80. "Unit Sensitively Detects Nitric Oxide", Chemical and Engineering News.
January 18, 1971, p. 33-
81. Niki, H. , Warnick, A., and Lord, R. R. , An Ozone-NO Chemi luminescence
Method for NO Analysis in Piston and Turbine Engines (SAE Paper No.
710072), Society of Automotive Engineers, Automotive Engineering
Congress, Detroit, Mich., January 11-15, 1971-
82. Singh, T. , Sawyer, R. F. , Starkman, E. S. , and Coretto, L. S. , "Rapid
Continuous Determination of Nitric Oxide Concentration in Exhaust
Gases", J. of the Air Pollut. Control Assn.. vol. 18, no. 2, February,
1968.
83. West, P. W. and Gaeke, G. C. , "Fixation of Sulfur Dioxide as Disulfito-
mercurate (II) and Subsequent Colorimetric Estimation", Anal . Chem. .
vol. 28, no. 12, December, 1956, pp. 1816-1819-
8^. Wilson, H. N. and Duff, G. M. S. , "Industrial Gas Analysis. A
Literature Review", The Analyst, vol. 92, December, 1967, p. 1101.
85. Stahl, Q. R. , Preliminary Air Pollution Survey of Aldehydes. A
Literature Review (Publication No. APTD 69-2*+) , National Air Pollution
Control Administration, U. S. Department of Health, Education, and
Welfare, Raleigh, N. C. , October, 1969.
86. Sawicki, E. , Hauser, T. R. , Stanley, T. W. , and Elbert, W. , "The 3-Methyl-
2 Benzothiazolone Hydrazone Test, Sensitive New Methods for the Detection,
Rapid Estimation, and Determination of Aliphatic Aldehydes", Anal . Chem. .
vol. 33, no. 1, January, 1961, pp. 93-96.
87. Groth, R. H. , Calabro, D. S. , and Gardner, D. G. , Evaluation of Three
Wet Chemical Methods for Determining Carbonyl in Turbine Exhaust Gases
(Paper No. 71-151), 6^th Annual Meeting, Air Pollution Control Association,
June 27-July 1, 1971.
88. Rounds, F. G. and Pearsall, H. W. , Diesel Exhaust Odor. Society of
Automotive Engineers, National Diesel Engine Meeting, Chicago, 111.,
1966.
-------
87
89« Devorkin, H. , Chass, R. L. , Fudurich, A. P., and Kanter, C. V.,
Air Pollution Source Testing Manual. Los Angeles County Air Pollution
Control District, Los Angeles, Calif., 1965-
90. Lippman, M. , Air Sampling Instruments for Evaluation of Atmospheric
Contaminants. American Conference of Governmental Industrial Hygienists,
Cincinnati, Ohio, 1966.
91. 01 in, J. G. , Trautner, R. P., and Sem, G. J. , Air-Quality Monitoring
of Particle Mass Concentration With a Piezoelectric Particle Micro-
balance (Paper No. 71-1), 64th Annual Meeting, Air Pollution Control
Association, June 27-July 1, 1971.
92. Chuan, R. L. , "An Instrument for the Direct Measurement of Particulate
Mass", J. of Aerosol Science, vol. 1, no. 2, May, 1970.
93- Herling, R. , et al, A Comparison of Automotive Particle Mass Emissions
Measurement Techniques. Presented at the Central States Meeting of
the Combustion Institute, University of Michigan, Ann Arbor, Mich.,
. March 23^24, 1971.
9^. "Exotic Detection Devices Unveiled for Air Pollution", Chemical
Engineering. May 20, 1968.
95. Charlson, R. J. , "Atmospheric Visibility Related to Aerosol Mass
Concentration, A Review", Environmental Science and Technology, vol. 3,
no. 10, October, 1969.
96. Air Quality Criteria for Particulate Matter. U. S. Department of
Health, Education, and Welfare, Public Health Service, Consumer
Protection and Environmental Health Service, National Air Pollution
Control Administration, Washington, D. C. , January, 1969«
97- Private Communication, Richard B. Codling, Meteorology Research, Inc.,
Altadena, Cal if.
98. Nesti, A. J. , Jr., "The Condensation Nuclei Counter as an Air Pollution
Weapon", Optical Spectra, July/August, 1970.
99» Shaffernocker , W. M. and Stanforth, C. M. , Smoke Measurement Techniques
(SAE Paper No. 6803^6), Society of Automotive Engineers, Air Transporta-
tion Meeting, New York, N. Y. , April 29-May 2, 1968.
100. Toone, B. , A Review of Aero Engine Smoke Emission. Lecture given at
Cranfield, Symposium on Combustion, April, 1967-
101. Sal lee, G. P., Standard Smoke Measurement Method (SAE Paper No.
700250), Society of Automotive Engineers, National Air Transportation
Meeting, New York, N. Y. , April 20-23, 1970.
102. Champagne, D. L. , Standard Measurement of Aircraft Gas Turbine
Engine Exhaust Smoke (ASME 71-GT-88), The American Society of
Mechanical Engineers, Presented at the Gas Turbine Conference and
Products Show, Houston, Tex., March 28-April 1, 1971.
103- Stockham, J. and Betz, H. , Study of Visible Exhaust Smoke from Air-
craft Jet Engines (SAE Paper No. 710^28), Society of Automotive
Engineers, National Air Transportation Meeting, Atlanta, Ga. , May 10-13,
1971.
-------
]Qk. Sullivan, R. J., Preliminary Air Pollution Survey of Odorous Compounds.
A Literature Review. U. S. Department of Health, Education, and
Welfare, Public Health Service, Consumer Protection and Environmental
Health Service, National Air Pollution Control Administration,
Raleigh, N. C., October, 1969.
105- Fish, B. R., On the Measurement of Odor. Presented at Symposium on
Measurement of Environmental Pollution, UT Space Institute, Tullahoma,
Tenna., May 20, 1971.
106. Dravnieks, A., O'Donnell, A., Scholz, R. , and Stockham, J. D. , jjjgs
Chromatoqraphic Study of Diesel Exhaust Using a Two-Column System.
Presented at the American Chemical Society Meeting, Division of
Water, Air, and Waste Chemistry, Los Angeles, Calif., March 29-
April 2, 1971.
107- Chemical Identification of the Odor Components in Diesel Engine
Exhaust. Final Report to Coordinating Research Council and National
Air Pollution Control Administration, U. S. Public Health Service,
Arthur D. Little, Inc., Cambridge, Mass., July, 1969.
108. Somers, J. H. and Kittredge, G. D., Review of Federally Sponsored
Research on Diesel Exhaust Odors. U. S. Environmental Protection Agency,
Presented at the 64th Annual Meeting of the Air Pollution Control
Association, Atlantic City, N. J., June 27-July 2, 1971.
109« Heylin, M., "Pollution Control Instrumentation", Chemical & Engineering
News. February 15, 1971-
110. Soderholm, L. G., "Ultraviolet-Absorption Technique Measures Auto Air
Pollution", Design News. June 21, 1968.
111. Groth, R. H. and Zaccardi, V. A., Development of a High Temperature
Subtractive Analyzer for Hydrocarbons (Report No. 71-152), Pratt &
Whitney Aircraft Corporation, Division of United Aircraft Corporation,
East Hartford, Conn.
112. Leonard, D. A., Feasibility Study of Remote Monitoring of Gas Pollutant
Emissions by Raman Spectroscopy (Research Report No. 362), Avco
Everett Research Laboratory, A Division of Avco Corporation, Everett,
Mass., December, 1970.
113« Leonard, D. A., Development of a Laser Raman Aircraft Turbine Engine
Exhaust Emissions Measurement System - Program Summary (Research
Note 892, Contract No. F33615-71-C-1875), Avco Everett Research
Laboratory, A Division of Avco Corporation, Everett, Mass., July, 1971.
114. Hinkley, E. D. and Kelley, P. L., Detection of Air Pollutants with
Tunable Diode Lasers. Lincoln Laboratory, Massachusetts Institute
of Technology, Lexington, Mass., 1971.
115. Kreuzer, L. B. and Patel, C. K. N., "Nitric Oxide Air Pollution
Detection by Optoacoustic Spectroscopy", Science, vol. 173, July 2,
1971.
116. Reagan, J. A., "Applying LIDAR as an Atmospheric Probe", Laser Focus.
June, 1968.
-------
89
117. Dix, R. E., Benek, J. A., MacDermott, W. N., and Tempelmeyer, K. E. ,
Experience with a Mass Spectrometer Probe for Studying the Formation
of Oxides of Nitrogen. Presented at the 64th Annual Meeting of the
Air Pollution Control Association, June 27-July 1, 1971.
118. Bogdan, L. and McAdams, H. T., Analysis of Aircraft Exhaust Emission
Measurements (CAL No. NA-5007-K-1), Cornell Aeronautical Laboratory,
Inc., Cornell University, Buffalo, N. Y., October 15, 1971.
-------
90
TABLES
-------
TABLE 1 - AIRCRAFT CLASSIFICATION SYSTEM
Ai rcraf t
Category
Air
Carrier
General
Av iat ion
Mil! tary
Class
1
2
3
1*
5
6
7
8
9
Ref I
Classi-
f icat ion
—
~
1
2
*4
3
6
Tvpe
Supersonic
Transport
Jumbo Jet
Transport
Long-Range
Jet Transport
Med i urn-Range
Jet Transport
Turboprop
Transport
Business Jet
Piston-Engine
Util ity
Over
1*00,000 Ibs
Gross Weight
100,000 Ibs -
1*00,000 Ibs
Gross Weight
Examples
Concorde
Tupolev TU-IM*
Boeing 7^7
Douglas DC-10
Boeing 707
Douglas OC-8
Boeing 727
Douglas DC-9
Lockheed Electra
Fairchild Hiller
FH-227
Lockheed Jetstar
North American
Sabrel iner
Cessna 210
Centurion
Piper 32-300
Cherokee Six
Boe ing
Stratofortress
Lockheed
Star! if ter
Representative Engine
Model
R-R/Snecma
Olympus 593
P£WA JT9D
P6WA JT3D
P£WA JT8D
Al 1 ison
501-D13
P6WA JT12
Cont inental
10-520-A
P6WA TF33-P-3
P&WA TF33-P-7
Tvpe
Turbojet
Turbofan
Turbofan
Turbofan
Turbo-
prop
Turbojet
Opposed
Piston
Turbofan
Turbofan
Thrust
or
Power
37,290 LB-T
1*7,000 LB-T
18,000 LB-T
11*. 500 LB-T
3)750 ESHP*
.3,300 LB-T
285 ESHP
17,000 LB-T
21,000 LB-T
Engi nes
per
Air-
craft
1*
k
k
2.6
2.5
2.1
1""
Shaft Power
Representative of VanNuys and Tamiami
-------
TABLE 1 - AIRCRAFT CLASSIFICATION SYSTEM (CONTINUED)
Aircraft
Category
Mil itary
V/STOL
Class
10
11
12
Ref 1
Classi-
fication
7
Type
10,000 Ibs -
100,000 Ibs
Gross Weight
Under
10,000 Ibs
Gross Weight
Hel icopters
and V/STOL
Examples
LTV Crusader
Cessna 172
Sikorsky S-61
Vertol 107
Representative Engine
Model
P&WA J57-P-20
Cont i nenta 1
10-360
General Elec-
tric CT58
Type
Turbojet
Opposed
Piston
Turbo-
shaft
Thrust
or
Power
18,000 LB-T
210 ESHP
1870 ESHP
1
Engine
Pef
Air-
craft
2
NJ
-------
TABLE 2 - TURBINE ENGINES IN THE U. S. AIR CARRIER FLEET
(JANUARY. 1970)
A!re raft
Class
Manufacturer
AiResearch Division
Garrett Corporation
Model
TFE731-2K
TPE331-2-20IA
Type
Turbofan
Turboprop
Turboprop
Maximum Pov;er
or Thrust
3500 LB-T
665-715 ESHP
575 ESHP
Number
in Use
Total
2
3
3
3
\
2
3
3
3
Al1ison Divis ion
General Motors Corporation
General Electric Company
Pratt & Whitney
Ai rcraft Divis ion
United Aircraft
Corporat ion
RolIs-Royce Ltd.
501-DI3
501-D22A
CF6-6D
CF6-50A
CJ805-3B
CJ805-23B
CJ610-1.9.6
CF700-2D2
JT9D-3A.7J5
JT3C-6.7
JT3D-1.3B.7
JT8D-I.9.7
JT12A-8
Turboprop
Turboprop
Turbojet
Turbofan
Turbofan
Turbojet
Turbofan
Turbojet
Turbofan
Turbofan
Turbojet
Turbofan
Turbojet
Turbofan
Turbojet
Olympus 593 Turbojet
RB.211-22B Turbofan
Conway RCo.12MK508.509 Turbofan
Conway RCo. ^2,i»3MK5*40 Turbofan
Spey RSp*4MK5!2 Turbofan
Avon RA-29-533 Turbojet
Spey RSp*4MK5H Turbofan
Bristol-Viper 522 Turbojet
3750 ESHP
ESHP
68600 LB-T
^0000 LB-T
A9000 LB-T
11650 LB-T
16100 LB-T
2850-3100 LB-T
^4250 LB-T
Total
Total
LB-T
13500
17000-19000 LB-T
17500 LB-T
li*500 LB-T
3300 LB-T
37290 LB-T
i«2000 LB-T
17500 LB-T
20370 LB-T
12550 LB-T
12600 LB-T
moo LB-T
3360 LB-T
Total
536
Bk
620
161*
2i+
8
10
206
6k
160
2811
376
2881
8
6300
120
OJ
-------
TABLE 2 - TURBINE ENGINES IN THE U. S AIR CARRIER FLEET (CONTINUED)
(JANUARY. 1970)
Ai rcraf t
Class Manufacturer
5 Rol Is-Royce Ltd.
5
5
5
5
5
5 Societe Turbomeca
5
5 United Aircraft of Canada
Model
Dart Da6-MK51*»
Dart Da7-MK532
Dart DalO-MK5**2
Dart Da7-MK529
Dart Da6-MK510
Tyne 12MK515
Astazou X 1 1
Bastan VIC
PT6A-20.27
Type
Turboprop
Turboprop
Turboprop
Turboprop
Turboprop
Turboprop
Turboprop
Turboprop
Turboprop
Maximum Power
or Thrust
1850 ESHP
2230 ESHP
3025 ESHP
2100. ESHP
J670 IStiP
5500 ESHP
731 ESHP
1065 ESHP
579-715 ESHP
Number
in Use
72
1^8
1A8
—
32
36
Total 598
_
-
Total 0
26
Total 26
TOTAL TURBINE ENGINES
Sources: References 7, 8, 9, 10, and 11
775*4
vo
-p-
-------
TABLE 3A - TOTAL ENGINES IN THE U. S. GENERAL AVIATION FLEET
(TURBINE ENGINES) (JANUARY. 1970)
Ai rcraft
Class
6
6
6
6
6
Maximum Pov/er
Number
6
6
6
6
6
6
6
6
6
6
6
6
6
Manufacturer
AiResearch Division
Garrett Corporation
A) 1i son Divis ion
General Motors Corporation
General Electric Company
Pratt & Whi tney
Aircraft Division
United Aircraft Corporation
Rolls-Royce Ltd.
Societe Turbomeca
United Aircraft of Canada
TOTAL TURBINE ENGINES
Sources: References 7, 8, 9, 10, and 11
Model
TPE33I-3U
TPE331-1-15IA
TPE331-143
ATF-3
TFE-731-2K
501-D13
CJ610-1.6.9
CF700-2D2
JT12A-8
JT8D-9.7
Dart Da7MK-529
Spey RSpl4MK5H-8
Viper 522
Viper 601
Dart Da7MK520
Dart DalOMK5i*2-it
Tyne 12MK5I5
Astazou XIV MK1
JT15D-1
PT6A-20.2.28
Type
Turboprop
Turboprop
Turboprop
Turbofan
Turbofan
Turboprop
Turbojet
Turbofan
Turbojet
Turbofan
Turboprop
Turbofan
Turbojet
Turbojet
Turboprop
Turboprop
Turboprop
Turboprop
Turbofan
Turboprop
or Thrust
8*»0 ESHP
665-715 ESHP
575 SHP
1*050 LB-T
3500 LB-T
3750 ESHP
2850-3100 LB-T
14250 LB-T
3300 LB-T
114500 LB-T
-
2100 ESHP
111400 LB-T
3360 LB-T
3750 LB-T
1815 ESHP
3025 ESHP
5500 ESHP
600 ESHP
2200 LB-T
579-715 ESHP
in Use
88
186
222
30
22
Total 5^8
12
Total 12
652
200
Total 852
6142
310
Total 952
562
138
131*
58
76
146
16
Total 1030
26
Total 26
2
1387
Total 1389
1*809
vn
-------
TABLE 3B - TOTAL ENGINES IN THE U. S. GENERAL AVIATION FLEET
Ai rcraft
Class
(PISTON ENGINES)
Manufacturer Model
Avco Lycoming Division 0-235
Avco Corporation 0-290
0-320
0-360
0-5^0
G0-*»80
10-320
10-360
I0-5*»0
TIO-320
Tl 0-360
TIO-5*»0
TIO-5*»1
TIO-5**7
IGSO-*t80
IGSO-5^0
Continental Motors Division 0-200
Teledyne Corporation 0-300
0-*»70
GO-300
W-670
(JANUARY, 19701
Type
Normal Carburation
Normal Carburation
Normal Carburation
Normal Carburation
Normal Carburation
Normal Carburation
and Gear
Fuel Inject ion
Fuel Inject ion
Fuel Injection
Turbocharged Fuel
Injected
Turbocharged Fuel
Injected
Turbocharged Fuel
Injected
. Turbocharged Fuel
Injected
Turbocharged Fuel
Injected
Fuel Injected,
Geared, Supercharged
Fuel Injected,
Geared, Supercharged
Normal Carburation
Normal Carburation
Normal Carburation
Normal Carburation
and Gear
Maximum Power
at Sea Level
115 ESHP
UO ESHP
160 ESHP
180 ESHP
260 ESHP
295 ESHP
160 ESHP
200 ESHP
300 ESHP
200 ESHP
310 ESHP
380
3*»0 ESHP
380 ESHP
100 ESHP
l*»5 ESHP
2*40 ESHP
Number
in Use
318
1302
20AOO
7610
16200
217
3010
87
12
2790
1150
258
53
Total 57335
30600
2)80
17050
1578
129
-------
TABLE 3B - TOTAL ENGINES IN THE U. S. GENERAL AVIATION FLEET (CONTINUED)
Ai rcraft
Class
(PISTON ENGINES) (JANUARY, 1970)
Manufacturer
Continental Motors Division
Teledyne Corporation
Curt iss-Wr ight Corporation
Fairchild Engine Division
Fairchild Aircraft Company
Franklin Engine Company, .Inc.
Subsidiary of Allied Aero
Indus tries
Jacobs-Page Aircraft Engine
Company
Pratt & Whitney
Aircraft Division
United Aircraft Corporation
•
Model
10-360
10-1*70
10-520
TSI-520
GTS 10-520
R-975
R1820
R2600
Rl*360
Ranger R6-1*1*OC
2A-120
l*A-235
6A-335
6A-350
R-755A2
R-755B2
R-985
R- 131*0
R-1830
R-2000
R-2800
Type
Fuel Injection
Fuel Injection
Fuel Injection
Turbocharged Fuel
Injected
Fuel Injected,
Geared, Supercharged
Radial
Radial
Radial
Radial
Hor i zontal -Opposed
Hor i zontal -Opposed
Hor i zon ta 1 - Opposed
Hor izontal -Opposed
Radial
Radial
Radial
Radial
Radial
Radial
Radial
Maximum Power
at Sea Level
210 ESHP
260 ESHP
300 ESHP
310 ESHP
1*75 ES.HP
1200 ESHP
1700 ESHP
2200 ESHP
200 ESHP
50-90 ESHP
65-80 ESHP
150-165 ESHP
100-215 ESHP
21*5 ESHP
300 ESHP
1*50 ESHP
600 ESHP
. 1050 ESHP
11*50 ESHP
2300 ESHP
TOTAL PISTON ENGINES
Sources: References 7,, 8, 9, and 11
Number
i n
1*29
12930
3330
58
Total 7321*4
3**
350
136
299
819
Total
Total
Total
Total
55
55
26
8
21*2
1900
2176
275
669
92
1190
901*
78
55*4
Total 2818
137116
-------
TABLE
- TOTAL ENGINES IN THE U. S. MILITARY FLEET
(TURBINE AND PISTON ENGINES) (JANUARY. 1970)
Ai rcraft
Class
8
10
Manufacturer
General Electric Company
Pratt & Whitney
Aircraft Division
United Aircraft Corporation
Al 1ison Division
General Motors Corporation
Curtiss-Wright Corporation
Pratt & Whitney
Aircraft Division
United Aircraft Corporation
AiResearch Division
Garrett Corporation
Al) i son D ivi s ion
General Motors Corporation
Avco Lycoming Division
Avco Corporation
Curtiss-Wright Corporation
Model
TF39
J57
T56
R-3350
JT3D
TF33
T76
T56
T63
J71
T53
YT55
J&5
R1300
R1820
R3350
Type
Turbofan
Turbojet
Turboprop
Radial Turbo-Comp.
Turbofan
Turbofan
Turboprop
Turboprop
Turbofan
Turboprop
Turboprop
Turbojet
Turboprop
Turboprop
Turbojet
Radial
Radial
Radial
Maximum Power
or Thrust
*»1100 LB-T
18000 LB-T
*»910 ESHP
3^00 ESHP
18000 LB-T
21000 LB-T
6000 ESHP
715 ESHP
15000 LB-T
^910 ESHP
317 ESHP
1900 ESHP
3750 ESHP
10500 LB-T
600 ESHP
1200 ESHP
3*tOO ESHP
Number
in Use
258
2000
Total 2258
1769
200
28
2*400
215
Total **612
826
*4000
1906
135
\2kkS
2*«93
137
11
2069
217
Including Military Helicopters
oo
-------
TABLE *4 - TOTAL ENGINES IN THE U. S. MILITARY FLEET" (CONTINUED)
Ai rcraft
Class
(TURBINE
Manufacturer
General Electric Company
Pratt & Whitney
Aircraft Division
United Aircraft Corporation
AND PISTON ENGINES)
Model
T58
T61»
J79
J85
TF30
TF33
J52
J57
J58
J60
T73
J75
F100
R 13*40
R2800
(JANUARY, 1970)
Type
Turboshaf t
Turboshaf t
Turbojet
Turbojet
Turbofan
Turbofan
Turbojet
Turbojet
Turbojet
Turbojet
Turboshaf t
Turbojet
Turbofan
Radial
Radial
RolIs-Royce Ltd.
11 Allison Divis ion
General Motors Corporation
Avco Lycoming Division
Avco Corporation
Continental Motors Division
Teledyne Corporation
General Electric Company
United Aircraft of Canada
TOTAL MILITARY ENGINES
Sources: References 1, 7. 8, 9, and 1
Dart MK 529-8X
J33
0-1435
GO-480
J69
0-1470
J85
T7** (PT6)
Turboprop
Turbojet
Normal Carburet ion
Normal Carburation
Turbojet
Normal Carburation
Turbojet
Turboshaft
Maximum Pov;er
or Thrust
1870 ESHP
3925 ESHP
17900 LB-T
2900-5000 LB-T
13^00 LB-T
21000 LB-T
11200 LB-T
16900 LB-T
30000 LB-T
3300 LB-T
14500 ESHP
26500 LB-T
30000 LB-T
600 ESHP
2300 ESHP
2100 ESHP
1*600 LB-T
260 ESHP
295 ESHP
1*420 LB-T
2*40 LB-T
2900-5000 LB-T
579. ESHP
Number
in Use
3159
1*58
10083
AOOO
1509
1307
3733
6231
878
208
11422
22
70
Total 57323
20
81*4
1419
555*4
173
3020
1*32
Total 10*432
7^625
VD
VD
-------
TABLE 5A - TOTAL ENGINES IN THE U. S. CIVIL HELICOPTER AND V/STOL FLEET
(TURBINE AND PISTON ENGINES) (JANUARY. 1970)
Ai rcraft
Class
.'.
12"
Manufacturer
AlIison Oivi s ion
General Motors Corporation
Avco Lycoming Division
Avco Corporation
General Electric Company
TOTAL CIVIL HELICOPTER ENGINES
Sources: References 7, 8, 9, and 11
Model
250-C18
T53
VO-*O5
V0-5*»0
HI 0-360
IVO-360
T58
CT58
Type
Turboshaft
Turboshaft
Vert ical-Opposed,
Normal Carburation
Vert ical-Opposed,
Normal Carburation
Horizontal-Opposed,
Fuel Injected
Vert ical-Opposed,
Fuel Injected
Turboshaft
Turboshaft
Maximum Power
or Thrust
317 ESHP
1900 ESHP
265 ESHP
305 ESHP
205 ESHP
180 ESHP
1870 ESHP
1870 ESHP
Number
iri Use
836
323
550
755
530
100
281
29
Heli copters
o
o
-------
TABLE SB - TOTAL ENGINES IN THE U. S. CIVIL HELICOPTER AND V/STOL FLEET
(TURBINE AND PISTON ENGINES) (JANUARY. 1970)
Ai rcraft
Class
12*
Manufacturer
AiResearch Division
Garrett Corporation
Avco Lycoming Division
Avco Corporation
General Electric Company
Pratt & Whi tney
Ai rcraft Divi s i on
United Aircraft Corporation
United Aircraft of Canada
TOTAL V/STOL ENGINES
TOTAL CLASS 12 ENGINES
Sources: References 7, 8, 9» and 11
Model
TPE33I
Type
0-5^*0
ALF301
J85
YT58
CF700
R2000
PT6A
Turboshaft
Geared, Normal
Carburation
Normal Carburation
Turbofan
Turbojet
Turboshaft
Turbojet
Radial
Turboshaft
Maximum Pov/er
or Thrust
715 ESHP
295 ESHP
300 ESHP
2730 LB-T
2900-5000 LB-T
1870 ESHP
A250 LB-T
1*450 ESHP
715 ESHP
jjumber
i n Use
15
k(>
2k
2
b
1
285
391
3795
V/STOL
-------
102
TABLE 6
ENGINE CLASSIFICATION
Tl - Small turbine engines (nominally less than 6000 LB-T or equivalent
shaft horsepower).
Examples: JT12A, T58
T2 - Turbine engines (nominally 6000 to 29,000 LB-T or ESHP).
Examples: JT8D, CJ805
T3 - Turbine engines (nominally 29,000 to LB-T or ESHP and greater)
Examples: JT9D, CF6
PI - Piston engines (all opposed configuration engines).
-------
TABLE 7
AIRCRAFT TURBINE ENGINE
Engine
Class Manufacturer
Tl-l All ison Div.
TI-2 CMC
TI-3
TI-4
TI-5
TI-6
TI-7 AiResearch D?v.
TI-8 Garrett Corp.
TI-9
TI-10
Tl-ll Avco-Lycoming Div.*
Tl-l 2 Avco Corp.
Tl-13
TI-14 Continental Motors
TI-15 General Electric Co.
TI-16
TI-17
TI-18
TI-19
TI-20
TI-21
TI-22
" Basel ine Engine
Eng ine
Fami 1 y
Model No.
J33
J71
T56
501
T63-
250
T76
TPE331
ATF3
TFE731
151
T55
ALF301
J69
T58
CT58
GE1
GE12
T64
J85
CJ610
CF700
Thrust
Engine or
Type Power
TJ
TJ
TP
TP
TP
TP
TP
TP
TF
TF
TS
TS
TF
TJ
TS
TS
TJ
TS
TS
TJ
TJ
TF
4600
1*910
3750
317
317
715
715
4050
3500
1900
3750
2730
1920
1870
1870
5000
1500
3925
5000
3100
4250
LB-T
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
LB-T
LB-T
ESHP
ESHP
LB-T
LB-T
ESHP
ESHP
LB-T
ESHP
ESHP
LB-T
LB-T
LB-T
CLASSIFICATION SYSTEM
Type
Combustor No.
CN (6)
CN (6)
CA (1)
CA (1)
A
A
A
A
A
A
A
A
CA (1)
CA (1)
CA (1)
A
A
A
A
A
; A G
620 12
- 836
4 511
30
22
- 323
285
29
8 652
10 201
Maximum
Production
Capacity Aircraft
in Use Per Year Classes
M
20
135
5769
1906
826
12449
2493
5554
3159
458
7022
-
.G =
M =
T =
T
20
135
5769
632
1906
836
826"
515
30
22
12772
2493
5554
3444
29
458
7022
660
211
20
100
1000
500
1000
500
1300
1000
650
600
600
300
150
1000
500
500
Ai r Carrier Fleet
General Aviation
Mi 1 i tary Fleet
Total Engines in
11
10
9,10
5,6
10
12
10
12,5,6
6
5,6
10,12
10
11
10,12
12
10
10,11 ,12
4,6
4,6,12
Fleet
Use
Total
No.
In Use
..9.238
J393
15265
5554
1 1 824
0
v*>
-------
TABLE 7 (CONTINUED),
AIRCRAFT TURB
Engine
Class Manufacturer
TI-23 Pratt & Whitney D
TI-2** Vac.
TI-25
TI-26
TI-27
TI-28
TI-29 Rolls-Royce Ltd.
TI-30
TI-31
TI-32
TI-33
T 1-3*4
TI-35
TI-36 Bristol Eng. Div.
TI_ v; Rolls-Royce Ltd.
' ' J f
TI-38 Societe Turbomeca
TI-39 United Aircraft
Tl-^tO of Canada Ltd.
TI-M
-
TI-^2 Westinghouse
Population unknown.
Eng i ne
Fami 1 y
Model No.
i v . J 60
JT1.2A
T73
T3*4
PT2
ST9
Dart Mk 510
511+
520
529
532
5*42
Tyne 12
VIPER 522
601
ASTAZOU XIV
JT15
T7*4
PT6
J3^
Engine
Type
TJ
TJ
TJ
TP
TP
TS
TP
TP
TP
TP
TP
TP
TP
TJ
TJ
TP
TF
TS
TS
TJ
INE ENGINE CLASSIFICATI
ON SYSTEM
Thrust
or Type
Power Combustor
3300
3300
1*050
6000
6000
1500
1670
1850
1815
2100
2232
3025
5500
3360
3750
600
2200
715
715
3UOO
TOTAL
LB-T
LB-T
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
ESHP
LB-T
LB-T
ES:J,P
LB-T
ESHP
ESHP
LB-T
CN (8)
CN (8)
CN (8)
CN (8)
CN (8)
—
CN (7)
CN (7)
CN (7)
CN (7)
CN (7)
CN (7)
CN (10)
CA (1)
CA (1)
j
A
A
A
A
--
Tl ENGINES
A
-
8
-
-
-
-
32
72
-
1^8
1*48
36
2
-
_ .
-
26
-
A
G
M
T
No.
G
-
6*42
_
-
-
-
_
_
76
562
**6
16
I3*»
8
26
2
_
1672
-
= Air
Max imum
Product i on
Capacity Aircraft
in Use Per Year Classes
M
878
_
208
215
*
^
_
_
-
_
_
-
^
-
_
*432
T
878 220
650 no
208 200
215 60
30
_
32
72
76
562
1*48
19*4
52 - -
136
58
26
2
1*32 100
- 1698 50
*
Carr
= General
= Mi 1
i tary
= Total En
-
ier Fleet
Aviation Fleet
Fleet
gines in Use
10
*»,6, 1 0
10
9
9
--
5
5
6
5,6
5
5,6
5,6
U,6
6
6
6
5
5,11 ,12
10
No.
In U^:«
1951
—up
IS-
26
__. _, _
? 1 3 ?.
TO:' 73
o
.r-
-------
TABLE 7 (CONTINUED)
AIRCRAFT TURBINE ENGINE CLASSIFICATION SYSTEM
Engine
Class
T2-1
T2-2
T2-3
T2-5
T2-6
T2-7
T2-8
T2-9
T2-IO
T2-11
T2-12
T2-13
T2-14
T2-15
T2-16
T2-17
T2-18
T2-19
T2-20
Engine
Fami 1 y
Manufacturer . Model No.
All ison Div. GMC T4l
Curt iss-Wr ight Corp J65
.
General Electric J79
Co. CJ805
TF34
•
Pratt & Whitney Div. J52
Vac.-'- JT8D
J57
JT3C
J75
IT/i A
w 1 • »»
TF33
JT3D
TF30
JTF10
Rolls-Royce Ltd. AVON RA29
CONV/AY CO 12
CONV/AY C042
SPEY MK 51 1
MK 512
Engi ne
Type
TF
TJ
TJ
TJ.TF
TF
TJ
TF
TJ
TJ
TJ
TJ
TF
TF
TF
TF
TJ
TF
TF
TF
TF
Thrust
or
Power
15000
10500
17900
1 1 650 , 1
9000
11200
14500
18000
13500
26500
17500
21000
19000
13400
131*00
12600
17500
20370
1UOO
12550
LB-T
LB-T
LB-T
6100
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
Type
Combustor No. in Use
CN (10)
CA (1)
'
CN (10)
CN (10)
A
CN (9)
CN (9)
CN (8)
CN (8)
CN (8)
CN (8)
CN (8)
CN (8)
CN (8)
CN (8)
_
CN (8)
CN (10)
CN (10)
CN (10)
CN (10)
TOTAL T2 ENGINES
A
-
—
•
-
188
-
-
2831
-
160
-
376
-
2811
.
-
1*0
-
-
-
120
A = Ai
G M
-
- 137
- 10083
-
-
- 3733
310 -
- 8231
-
11*22
-
- 3707
28
- 1509
-
-
-
-
138 -
-
r Carrier
G = General Avi
M = Mi
1 i tary Fl
T
-
137
10083
188
-
3733
3191
8231
160
11*22
376
3707
2839
1509
-
1*0
-
-
138
120
Fleet
at ion
eet
. T - Total Enoines in
Max imum
Product i on
Capacity Aircraft
Per Year Classes
500
100
1400
700
--
500
250
2000
1000
300
150
700
350
400
200
— _
__
__
_ _
--
Fleet
Use
10
10
10
3,4
10
i; £
8,10
3
10
3
9,10
3-9
10
--
4
3
3
'i.
Total
No.
In Use
M7
Toiyr
25168
298
35874
o
Baseline Engine
vn
-------
TAD I? 7 (CONTINUED)
AIRCRAFT TURB
Engi ne
Class
T3-1
T3-2
T3-3
T3-4
T3-5
T3-6
T3-7
T3-8
T3-9
Engine
Fami 1 y
Manufacturer Model No.
General Electric* JF39
Co. CF6
GE9
GE4
Pratt & Whitney Div. J58
Vac. JT11D
JT9D
Rolls-Royce Ltd. RB21 1
OLYMPUS 593
INE 7JIGINE CLASS IF
1 CAT ION SYSTEM
Thrust
Engine
Type
TF
TF
TF
TJ
TJ
TJ
TF
TF
TJ
or
Power
41100
40000
68600
30000
30000
47000
42000
37290
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
LB-T
TOTAL T3 ENGINES
Vv
RA«;P 1 i i
tc Fnoinp<;
Type
Combus tor
A
A
A
__
--
A
A
A
A =
G =
M ~
T =
No. in Use
A G M
- - 258
_
-
-
_
64 - -
— - _
Air Carrier
General Avi
Mi 1 itary Fl
T
258
-
- -
_
-
64
_
Max imum
Product ion
Capaci ty
Per Year
500
250
~ •"
500
250
500
^
^ —
** **
Ai rcraf t
Classes
8
2
"
10
--
2
2
1
Fleet
Total
No.
In Use
258
64
—
322
at ion F 1 eet
eet
Total Engines i
n Use
-------
TABLE 8
AIRCRAFT PISTON ENGINE CLASSIFICATION SYSTEM'*
Engi ne
Class
P'l-1
PI-2
PI-3'
PI-*4
PI-5
PI-6
PI-7
PI -8
PI -9
PI-10
Pl-ll
PI-12
PI-13
P|-l*4
PI-15
PI-16
PI-17
PI-18
PI-19
PI-20
PI-21
PI-22
PI-23
PI-2*4
PI-25
PI-26
PI-27
PI-28
Engine
Fami ly
Manufacturer Model No.
Avco-Lycomi ng 0-235
Avco Corporation 0-290
0-320
0-360
0-*435
0-5*40
G0-*480
10-320
HIO-360
10-360
10-5*40
TIO-320
TIO-360
T 10-5*40
TIO-5*4l
TIO-5*47
IGSO-*480
IGSO-5*tO
VO-*435
V0-5*40
IVO-360
Continental Motors 0-200
DIV, Teledyne Corp. 0-300
0-*470
GO-300
w-670
10-360
I0-*470
Engine
Type
HO.NC
HO.NC
HO.NC
HO.NC
VO.NC
HO.NC
G.HO.NC
1 ,HO
1 ,HO
1 ,HO
I.HO
T, ,HO
T, ,HO
T, ,HO
T, ,HO
T, ,HO
I.G.S
I.G.S
VO.NC
VO.NC
1 ,VO
HO.NC
NO.NC
HO.NC
G,HO,NC
--
1 ,HO
1 ,HO
"
Thrust
or
Power
115 ESHP
1*40
160
180
260
260
280
160
180
200
300
160
200
310
380
--
3*40
380
260
305
180
100
1*45
2*40
1*45
--
210
260
No.
G
318
1302
20*400
7610
-
1622*4
263
3010
530
*458
2*430
87
12
2790
1150
258
10*»0
53
550
755
100
30600
2180
17050
1578
129
*429
*4960
in Use
M T
318
1302
20*400
7610
81*4 81*4
1622*4
*4l9 682
3010
530
*458
2*430
87
12
2790
1150
258
10*40
53
550
755
100
30600
2180
173 17223
1578
129
*429
*4960
Max imum
Product ion
Capac i ty
per year
1173
15
3700
2100
_ _
2700
306
__
__
__
«. _
_ _
__
__
200
• _
_ _
_ _
__
__
--
3187
1700
__
__
—
55*4
2000
Total
A i rcraf t i n
Classes Use
7
7
7
7
1 1
7,12
7,11,12
7
12
7
7
7
7
7-
7
7
7
7
12
12
12
-60573
7
7
7,11
7
7
7
7
Radial engines not included
G = General Aviation Fleet
M = Mi Iitary Fleet
T = Total Piston Fleet
o
—j
-------
TABLE 8 (CONTINUEDI
PI-29
PI-30
Pl-31
PI-32
PI-33
PI-34*
PI-35
Manufacturer
Franklin Engine CO
AIRCRAFT PISTON ENGINE C
Enqi ne
Fami 1 y
Model No.
10-520
TS10-520
GTSI 0-520
2A-I20
**A-235
6A-335
6A-350
Enq i ne
Type
1 ,HO
T.I.HO
G.T.I ,HO
HO.NC
HO.NC
HO.NC
HO.NC
LASSIFICATION SYSTEM
Thrust
or
Power
300
310
^35
50-90
65-80
200
230
No. in Use
G M
12930
3330
58
26
8
2*+2
1900
T
12930
3330
58
26
8
2k2
1900
Maximum
Produc1i on
Capac i'ty
per year
2600
Aircraft
Classes
7
7
7
7
7
7
7
73^17
TOTAL PISTON ENGINES
21/6
1^3,130
HO = Horizontally Opposed
VO = Vertically Opposed
R = Radia1
NC = Normal Carburet ion
I = Fuel Injection
G Geared Propeller Drive
T = Turbo-Supercharged
S = Supercharged
G = General Aviation Fleet
M = Mi 1i tary Fleet
T = Tola 1 Pi ston Fleet
o
CO
-------
TABLE 9
AIRCRAFT TURBINE AND PISTON ENGINE CLASSIFICATION SUMMARY
Total
Families
Class (Population)
Tl k2
(48773)
T2 20
(3587*0
T3 9
(322)
Air
Carrier
Fami 1 i es
(Population)
6*
dm)
10
(6576)
7
(64)
General
Aviation
Fami 1 ies
(Population)
16*
(6137)
2
(448)
0
(o)
Total
Civil
Aviation
Fami 1 ies
(Population)
22
(7251)
12
(7024)
7
(64)
Total
Mi 1 i tary
Fami 1 i es
(Populat i ori)
20
(41522)
8
(28850)
2
(258)
TURBINE
TOTAL
POPULATION
84969
7754
6585
14339
70630
•• Placement of engine families in these categories is based upon majority of engine applications since some
families are used in both air carrier and general aviation categories.
PISTON
TOTAL
POPULATION
39
(136166)
136166
(*
(*
*)
*)
34
(134760)
134760
34
(134760)
134760
(1406)
1406
** Radial Engines not included
oWt Air carrier piston engines not included
o
vo
-------
no
TABLE 10
EMISSION CONTROL METHODS: MODIFICATION OF
TURBINE ENGINES
I. Methods applicable to existing engines
tl. Combustion chamber redesign (minor) - Minor modifi-
cation of combustion chamber and fuel nozzle to achieve
best state-of-art emission performance.
it2. Combustion chamber redesign (major) - Major modifica-
tion of combustion chamber and fuel nozzle in-
corporating advanced fuel injection concepts (car-
buretion or prevaporization).
t'3. Fuel drainage contro] - Modify fuel supply system or
fuel drainage system to eliminate release of drained
fuel to environment.
t4. Divided fuel supply system - Provide independent fuel
supplies to subsets of fuel nozzles to allow shut-down
of one or more subsets during low power operation.
t5. Water injection - Install water injection system for
short duration use during maximum power (take-off and
climb-out) operation.
t6. Modify compressor air bleed rate - Increase air
bleed rate from compressor at low power operation to
increase combustor fuel-air ratio.
I I. Methods applicable to future engines
t7. Variable-geometry combustion chamber - Use of variable
airflow distribution to provide independent control
of combustion zone fuel-air ratio.
t8. Staged injection combustor - Use of advanced combustor
design concept involving a series of combustion zones
with independently-controlled fuel injection in each
zone.
-------
11
TABLE 11
EMISSION CONTROL METHODS: MODIFICATION OF PISTON
ENGINES
1. Methods applicable to existing engines
pi. Simple air injection - Air injected at controlled
rate into each engine exhaust port.
p2. Thermal reactors - Air injection thermal reactor
installed in place of, or downstream of, exhaust
manifold.
p3. Catalytic reactors for THC arid CO control - Air in-
jection catalytic reactor installed in exhaust system.
Operation with lead-free or low-lead fuel required.
p4. Direct-Flame Afterburner - Thermal reactor with in-
jection of air and additional fuel installed in ex-
haust system.
p5. Water injection - Water injected into intake manifold
with simultaneous reduction in fuel rate to provide
operation at leaner fuel-air ratios.
p6. Positive crankcase ventilation.- Current PCV system
used with automotive engines applied to aircraft
engines. Effective only in combination with one of
preceding control methods.
p7. Evaporative emission controls - A group of control
methods used singly or in combination 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.
I I. Methods applicable to future engines
p8. Engine redesign - Coordinated redesign of combustion
chamber geometry, compression ratio, fuel distribution
system, spark and valve timing, fuel-air ratio, and
cylinder wall temperature to minimize emissions while
maintaining operational reliability.
-------
TABLE 12A
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MOD IFI CAT IONS
Control Method tl - Combustion Chamber Redesign (minor)
Best current emission rates assumed to be attainable through minor
comb us tor
Enqi ne
Class
Tl
T2
T3
Basis for
redesign (lb/1000
Pol lutant
CO
THC
.NOx
DP
CO
THC
NOx
DP
CO
THC
NOx
DP
estimates
Ib fuel)
Mode
Idle/Taxi
25
10
3
0.2
^5
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
Take-Off
2
0.2
11
0-5
1
0.1
12
0.5
0.5
0.1
i+0
0.1
It is assumed 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, as shown in Figures 1-4.
-------
113
TABLE 12B
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MODIFICATIONS •
Control Method t2 - Combustion Chamber Redesign (major)
Emission Rate with Control Method Installed (as fraction of best current
rate for
Enqi ne
Class
Tl
T2
Basis for
engine class)
Pol lutant
DP
DP
estimates
J
Mode
Idle/Taxi . Approach Take-Off
0.5 0,5 0.5
0.5 0.5 0.5
Estimates based on reports of carbureting fuel injector performance
and reduction of smoke emission. Concept is incorporated in some
Class T3 engines. Estimates based on assumption that best emission
rate for Class Tl and T2 engines is at visibility threshold at maximum
power. Carburetion appears to reduce smoke level, and presumably
particulate emissions, to approximately one-half that level (Refs 12 fl
13).
-------
TABLE 12C
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MODIFICATIONS
Control Method t3 - Fuel Drainage Control
Emission Rate with Control Method Installed (as fraction of best current
rate for engi
Engine
Class
Tl
T2
T3
Basis for est
ne class)
Pol lutant
THC
THC
THC
imates
Take-Off
Mode (Drainage
Idle/Taxi Approach Mode)
0
no change 0
0
Estimate based on the assumption that fuel drainage can be completely
eliminated by collecting drained fuel and returning to fuel tank.
-------
115
TABLE 12D
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MODIFICATIONS
Control Method t4 - Divided Fuel Supply System
Emission Rate with Control Method Installed (as fraction of best current
rate for
Enqine
Class
Tl
Tl
T2
T2
T3
T3
Basis for
engine class)
Pol lutant
CO
THC
CO
THC
CO
THC
estimates
Mode
Idle/Taxi
0.25
0.25
0.25
0.25
0.25
0.25
Approach Take-Off
no change
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. Effectiveness reduced by one
order because combustor is not operating at a "wel1-designed condition.
-------
116
TABLE 12E
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MODIFICATIONS
Control Method t5 - Water Injection
Emission Rate with Control Method Installed (as fraction of best current
rate for
Enqi ne
Class
Tl
T2
T3
engine class)
Pol lutant
NOx
NOx
NOx
Mode
Idle/Taxi Approach Take-Off
0.25
0.25
no change
0.25
Basis for estimates
Assumed that water injection used at take-off only and at a rate
equal to twice the fuel rate. Also assumed that water is injected
into compressor or diffuser by system similar to those in current
use. Effectjveness based upon published results with steam injection
(ftef 1*+). Water injection assumed to be of equal effectiveness when
injected upstream of combustor.
-------
117
TABLE 12F
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MODIFICATIONS
Control Method t6 - Modify Compressor.Air Bleed Rate
F.mission Rate with Control Method Installed (as fraction of best current
rate for
Enqi ne
Class
Tl
Tl
T2
T2
T3
T3
engine class)
Pol lutant
CO
THC
CO
THC
CO
THC
Mode
Idle/Taxi
0.5
0.5
0.5
0.5
0.5
0.5
Approach Take-Off
no change
Basis for estimates
Assumed that fraction of air which can be bled is small so that
engine operating point is nearly unchanged. Assumed that combustor
f/a varies inversely with air bleed rate, and that CO and THC
emissions at idle vary as:
(f/a)"3 -
3
This relationship based upon data from NREC Report 113^-1 (Ref 1). If
maximum air bleed rate is 20 per cent, CO and THC emission rates
are reduced by 50 per cent.
-------
18
TABLE 12G
EMISSION CONTROL METHOD EFFECTIVENESS:
TURBINE ENGINE MODIFICATIONS
Control Method . t7 - Variable-Geometry.Combust ion Chamber
or t8 - Staged Injection Combustor
Emission Rate with Control Method Installed (as fraction of best current
rate for engine class)
Enqine
Class
Tl
T2
T3
Basis for
Pol lutant
CO
THC
NOx
DP
CO
THC
NOx .
DP
CO
THC
NOx
DP
estimates :
Idle/Taxi
0.1
0.1
NC
0.5
0.1
0.1
NC
0.5
0.1
0, 1
NC
0.5
Mode
Approach
NC
NC
NC
0.5
NC
NC
NC
0.5
NC
NC
NC
0.5
Take-Off
NC
NC
0.5
0.5
NC
NC
0.5
0.5
NC
NC
0.5
0.5
a. Assumed that combustor primary zone operates at a constant f/a
equal to normal f/a at approach power condition (primary zone
equivalence ratio = 0.6). CO and THC emissions at idle reduced to
levels corresponding to approach power, or by 90 per cent.
b. Combustor incorporates design characteristics which provide well-
mixed combustion zone. This feature and constant f/a operation
combine to reduce NO emissions at full power by 50 per cent (Ref 16)
and particulate emissions by 50 per cent-at al.l power leve.ls as in control
method t2.
-------
TABLE 13
CURRENT UNCONTROLLED EMISSION RATES - PISTON ENGINES
Pol lutant
CO
THC
NOx
(as N02)
(lb/
Idle
896
48
7
1000 Ib-fuel)
Mode
Taxi Approach
882 918
76 80
4 4
Take-Off
849
18
6
Basis for Estimates:
Rates listed are average rates for nine engines measured
during aircraft operations (Ref 3). Total hydrocarbon (THC) emission
rates have been increased by 50 per cent to account for crankcase blow-by
emissions. Evaporative emissions are not included in these rates.
-------
120
TABLE
EMISSION CONTROL EFFECTIVENESS:
PISTON ENGINE MODIFICATIONS
Control Method
Controlled Emission Rate"
p] - Simple Air Injection
p2 - Thermal Reactor
p3 - Catalytic Reactor
pk - Direct-Flame Afterburner
p5 - Water Injection
p6 - Positive Crankcase Venti-
lation
p7 - Evaporative'Emission Control
p8 - Engine Redesign
(fraction
CO
0.5
0.25
0.25
0.1
0.25
NC
NC
0.5
of uncontrol
THC
(exhaust .
only)
0.5
0.25
0.25
0.1
0.24
**
Vn.Wf
0.5
led rat
Lead
NC
NC
0.1
NC
NC
NC
NC
NC
Basis for Estimates
Review of published results..on effectiveness of automotive emis-
sion controls; in particular, References 17, 18, and 19.
Fractions listed are considered to be applicable to all operating modes.
PCV would eliminate blow-by emissions when used in combination with pi,
p2, p3, pk, or p5. Blow-by THC emission estimated to be equal to 30 per
cent of uncontrolled exhaust emission.
Evaporative controls would reduce THC emissions due to evaporation from
fuel supply. Magnitude of uncontrolled emissions is unknown.
-------
TABLE 15
TOTAL AIRCRAFT TURBINE ENGINE DEVELOPMENT COST/TIHE SAMPLE CALCULATION
Total Total No.
Dev. Dev. of Total
Total Total & & Engine Dev.
Dev. Dev. Test Test Families Cost
& & Tool Tool Tool Tool Total Total & & in Per
No. Control Dev. Dev. Test Test Test Test Design Design Procure Procure Tool Tool Tool Tool Class Class
Engine Engines Method Cost Time Cost Time Cost Time Cost Time .Cost Time Cost Time Cost Time T 2 T 2
$/FAM yrs.$/FAM yrs.$/FAM yrs.
JT8D
JT8D
JT8D
JT8D
JT8D
JT8D
3191 ti
3191 t2
3191 t3
3191 tk
3191 t$
3191 tt
360k 1-2
720k 2-3
360k 1-2
720k 2-3
200k 1
k
1080 1-2
360k 1-2 720k 2-4
720k 2-3 1 .44m 4-6
360k 1-2 720k 2-4
720 2- 3 l.44m 4-6
360k 1-2 560k 2-3
720k 2-3 1.8m 3-5
$/FAM yrs. $/FAM
10k
120k £-1 60k
20k
240k 1-3 A 120k
15k
I8ok 1-3 A 90k
20k
50k £-1 I0k
20k
240k 1-3 A 120k
yrs.
*-!
1-3 A
1-3 A
1-3 A
i"!
1-3 A
$/FAM
130k
I80k
260k
360k
I95k
270k
260k
360k
6ok
260k
360k
yrs. $/FAM yrs.
1-1 900k 2l-5 20
V
l-l! l.8m 5-7! 20
l-l! 990k 3-5! 20
l-l! l.8m 5-71 20
1-1 620k 21-4 20
l-l! 2.2m 4-6! 20
$
18"
36m
20m
36m
|2m
43-
-------
TABLE 16
Engine
JT8D
JT8D
JT8D
JT8D
JT8D
JT8D
TURBINE ENGINE DEVELOPMENT COST/T
CATEGORIES; AIR CARRIER,
Note:
Total
Develop-
ment and
Control Test and
Method Tool Cost
$/FAMILY
t, 900k
t2 1.8m
t3 990k
t^ 1.8m
t 620k
2.2m
Civil Aviat
Number .
of Ai r
Carrier
Engi ne
Fami 1 i es
in C lass
T2
_ _
10
10
10
10
10
10
ion Engines
Total
Deve lop-
ment Cost
for C lass
T2 Air
Carrier
Engi nes
$
9m
I8m
9-9m
18m
6.2m
22. Om
= Sum of
Number of
Genera 1
Avi a t i on
Fami 1 i es
i n C lass
T2
2
2
2
2
2
2
IME SAMPLE CALCULATION FOR SEPARATE
GENERAL AVIATION. MILITARY
Ai r Carrier
Total
Develop- .
ment Cost
for C lass
T2 Gen-
era 1
Aviation
Engi nes
$
l.8m
3.6m
2.0m
3.6m
1.2m
it.it"1
and Genera
Number of
Civi 1
Aviat ion
Engi ne
Fami 1 i es
i n C lass
T2
12
12
12
12
12
12
1 Avi at i on
Total
Deve lop-
ment Cost
for C lass
T2
Civi 1
Avia t i on
Engi nes
$
10. 8m
21. 6m
11. 9m
21. 6m
7.km
26. km
Engi nes
Number of
Mi 1 i tar y
Avia t i on
Engi ne
Fami lies
i n C lass
J12_
8
8
8
8
8
8
Total
Deve lop-
ment Cost
for C lass
T2
Military
Avia t ion
Engi nes
$
7-2m
1*4. it™
8.1m
li*.i*m
i*.6m
I6.6m
-------
TABLE 17
TOTAL AIRCRAFT PISTON ENGINE DEVELOPMENT COST/TIME SAMPLE CALCULATION
Engine
Control Dev. Dev. Test Test Total Total Tool Tool Tool Tool Total Total Per Total No, of Total
Method Cost Time Cost Time Dev. Dev. Design Design Procure Procure Tool Tool Family Time Engines Dev.
6- & Cost Time Cost Time Cost Time Total Dev. Families Cost
Test Test One- & in for
Cost Time Time Test Class Class
Cost Tool PI PI
yrs $ yrs. $
yrs. $
yrs.
$
yrs,
yrs. $
yrs
Piston
Piston
Piston
Piston
Piston
Piston
Piston
P,
P2
P3
pi,
P5
P6
P
62k i-l 170k i-
232
6l
i/3A 70
1-2
228k 1-2 350k 1-2 578k 2-k
2l6k 1-2 350k 1-2 566k 2-k
228k 1-2 350k 1-2 578k 2-k
I70k i-l 231k 1-2
95k i-l 95k i-l
117
30*
120k
60k
120k
15k
5k
5k
i-i
i-l
i-i
i-i.
i-i
i i
V 2
i-i
IOK
30k
15k
30k
5k
5k
5k
i-i
i-l
i-i
i-l
i-i
i-i
i-i
ko
150k
75k
150k
20k
iok
,ok
i-l
1-2
i-l
1-2
i-l .
i-l
i-l
272
728k
6k} k
728k
25 lk
105k
I27k
li-3
3-6
2i-5
3-6
li-3
1-2
li-2i
35
35
35
35
35
35
35
9-5M
25.6N.
22. *4M
25.6M
8.8M
3.7M
k.S*
-------
TABLE 18
PISTON ENGINE DEVELOPMENT COST/TIME SAMPLE CALCULATION FOR SEPARATE
CATEGORIES; AIR CARRIER. GENERAL AVIATION. MILITARY
Note: Civil Aviation Engines = Sum of Air Carrier and General Aviation Engines
Control
Method
^ . —
pl
P2
P,
3
P4
Pr
5
P6
P.,
Total
Develop-
ment and
Test and
Tool Cost
$ /FAMILY
272k
728k
691k
728k
25lk
105k
12?k
Number
of Air
Carrier
Engi ne
Fami 1 i es
in Class
PI
_ _
0*
0
0
0
0
0
0
Total
Develop-
ment Cost
for Class
PI Air
Carrier
Engines
$
0
0
0
Q
0
0
0
Number of
General
Aviation
Fami 1 ies
in C lass
PI
— —
34
3*t
34
34
34
34
34
Total
Develop-
ment Cost
for C lass
PI
General
Avi at ion
Engi nes
$
' 9.3m
24. 8m
21.7
24. 8m
8.5m
3.6m
4.3m
Number of
Civil
Aviat ion
Engine
Fami 1 ies
i n C lass
PI
— —
34
34
34
34
34
34
34
Total
Develop-
ment Cost
for C lass
PI Civi 1
Aviat ion
Engi nes
$
9.3m
24. 8m
21.7k
24. 8m
8.5m •
3.6m
4.3m
Number of
Mi I i tary
Aviat ion
Engine
Fami 1 i es
in C lass
PI
V •
1
1
1
I
1
1
1
Total
Develop-
ment Cost
for Class
PI
Mi li tary
Aviat i on
Engi nes
$
272k
728k
641 k
728k
251k
-05k
127k
Air carrier piston engines not included.
-------
TABLE 19
Control
Enqi ne Method
JT8D
JT8D •
JT8D
JT80
JT8D
JT80
TOTAL AIRCRAFT TURB
Lost
Serv ice
Life
Cost/
Enq i ne
$/Eng
2500
2500
500
2500
0
0
Add.
1 ns tal-
lat ion
Cost/
Enqi ne
$/Eng
2000
*4000
1000
2000
2000
1500
10 Years
Total
Add.
Instal-
lation
Cos-t/
Enqi ne
$/Eng
8000
16000
itOOO
8000
8000
6000
INE ENGINE
Cont inu-
inq Add.
Cost/
Enq i ne/
Year
$/Eng/Yr
2500
k2kO
0
0
760
0
IMPLEMENTATION COST/TIME SAMPLE CALCULATION
10 Years
Cont i nu-
i nq Add.
Cost/
Enq i ne
$/Eng
25000
i*2*+00
0
0
7600
0
10 Years
Total
Imple-
ment
Cost/
Enq i ne
$/Eng
35500
60900
i*500
10500
15600
6000
Total
No. of
Enqi nes
in Class
."T 2
3587*4
3587*4
3587*4
3587*4
3587*4
3587*4
10 Years
Total
Imp le-
ment
Cost for
. Class T2
Enq i nes
$xlo'S
1275
2180
161.
376
560
215
Total
T ime
Be tv/een
Over-
hau 1 s
(TBO)
Yrs.
2 1/2
2 1/2
2 1/2
2 1/2
2 1/2
2 1/2
Imp Ie-
ment
Imp 1e-
ment
Start Finish
Date
1977
1979
1977
1979
1976
1978
Date
1979
1983
1980
1982
1978
1981
K>
NJ1
-------
TABLE 20
Engi ne
JT80
JT8D
JT8D
JT8D
JT8D
JT8D
TURBI
NE ENGINE
IMPLEMENT AT
CATEGORIES: AIR
Control
Method
--
t,
t2
t3
t^
t5
1 £
Note
10 Years
Total Im-
plementa- .
tion Cost/
Engi ne
$/ENG
. 35,500
60,900
^,500
10,500
15,600
6,000 '
ION COST/TIME SAMPLE CALCULATION
CARRIER, GENERAL AVIAT
FOR SEPARATE
ION, MILITARY
Civil Engines - Sum of Air Carrier and General Aviation Engines
Number
of Ai r
Carr i er
Engi nes
in Class
T2
--
6,576
6,576-
6,576
6,576
6,576
6,576
Total
Implement
Cost for
Class T2
Air
Carr i er
Engi nes
..
$x!0b
233
koo
30
69
103
39
Number of
General
Aviation
Engi nes
in C lass
. T2
--
M»8
kkB
kkB
kkB
kkB
kkB
Total
Implement
Cost for
Class T2
General
Aviat i on
Engi nes
-6
$x!0b
16
27
2
5
7
3
Number of
Ci vi 1
Aviat ion
Engi nes
i n C lass
T2
--
7,02k
7,02k
7,02k
7,02k
7,02k
7,02k
Total
Impl ement
Cost for .
Class T2
Civil
Aviat ion
Enqi nes
-6
$xlO
250
i*28
32
7k"
110
1*2
Number of
Mi 1 i tary
Aviat ion
Engi nes
in C lass
T2
28,850
28,850
28,850
28,650
28,850
28,850
Total
Impl ement
Cost for
Class T2
Mi Li tary
Aviat i on
Engi nes
-6
$xlO D
1,025
1,752
129
302
*450
173
-------
TABLE 21
TOTAL AIRCRAFT PISTON ENGINE IMPLEMENTATION COST/TIME SAMPLE CALCULATI
Enqi ne
- —
Piston
Piston
Piston
Piston
Piston
Piston
Piston
Control
Method
--
P.
pi
p
P;
P6
P?
Lost
Service
Life
Cost/
Enq ine
$/Eng
25
25
25
25
0
0
0
Add.
Instal-
lat ion
Cost/
Enqine
$/Eng
U50
850
825
850
300
150
500
10 Years
Total
Add.
Instal-
lation
Cost/
Enqine
$/Eng
900
1700
1650
1700
600
200
1000
10 Years
Cont i nu-
inq Add.
Cost/
Enqi ne/
Year
$/Eng/Yr
30
230
1^2
0
50
100
10 Years
Cont i nu-
inq Add.
Cost/
Enqi ne
$/Eng
300
1^20
2300
Ht20
0
500
1000
Total
Imple-
ment
Cost/
Enqine
$/Eng
1225
31^5
3975
31**5
600
700
2000
Total
No. of
Enqi nes
in C lass
PI
•
— —
136,166
136,166
136,166
136,166
136,166
136,166
136,166
10 Years
Total
Imp le-
ment
Cost for
Class PI
Enqi nes
" 6
$x!0°
167
i+30
5^2
1+30
82
96
272
ON
Total
T ime
Between
Over-
hauls
(TBO)
Yrs.
5
5
5
5
5
5
5
Imple-
ment
Start
Date
— -
1975
1978
1977
1978
1975
197*»
197**
Imple-
ment
Finish
Date
— —
1980
1983
1982
1983
1980
1979
1979
-------
TABLE 22
PISTON ENGINE IMPLEMENTATION COST/TIME SAMPLE CALCULATION FOR SEPARATE
CATEGORIES: AIR CARRIER. GENERAL AVIATION. MILITARY
.Note: Civil Engines = Sum of Air Carrier and General Aviation Engines
Control
Method
--
pl
P2
P3
pk
P5
P6
P7
10 Years .
Total Im-
plementa-
tion Cost/
Engi ne
$/ENG
1,225
3,1**5
3,975
3,1**5
600
700
2,000
Number
of Air
Carrier
Engi nes
i n C lass
PI
--
0
0
0
0
0
0
0
Total
Implement
Cost for
Class PI
Air
Carrier
Engi nes
$xlO~6
0
• 0
0
0
0
0
0
Number of
Genera 1
Aviat ion
Engi nes
in C lass
PI
--
13**, 760
13**, 760
13**, 760
13**, 760
13**, 760
13**, 760
13**, 760
Total
Implement
Cost for
Class PI
General
Aviat i on
Engi nes
$xlO
165
**2**
536
^2^
81
95.
270
Number of
Civil
Aviat ion
Engi nes
i n C lass
PI
.
13**, 760
13**, 760
13**, 760
13**, 760
13**, 760
13**, 760
1 3*», 760
Total
Imp lement
Cost for
Class PI
Civil
Aviat ion
Enqi nes
$xlO~6
165
k2k
536
k2k
81
95
270
Number of
Mi 1 i tary
Aviation
Engi nes
i n C lass
PI
--
1 ,**06
1,**06
1 ,**06
1 ,*»06-
1 ,**06
l,**06
1,**06
Total
Impl ement
Cost for
Class PI
Mi 1 i tary
Avia t i on
Engi nes
$xlO~6
1.7
k.k
5.6
*t.**
0.8
1.0
2.8
OO
-------
TABLE 23
TURBINE ENGINE COST SCALING PARAMETER SUMMARY
Engine SFC OPR W T(P)
Ib/HP-HR P2/P](lbs) Ibs(ESHP)
T53 0.56 8 561 igoo
*JT8D 0.63 18 3309 15500
TF39 0.58 25-7 7311 141100
10 Year 10 Year
Total Total
Imple- Imple-
ment ment
Cost/ Cost/
SFCxOPR 2W/T P P/P... Engine /T" /f77%~ Engine
$/ENG. -tfTbs " $/EMG.
i*.i»8 0.59 5.07 0.1*3 15250 1*3.6 0.35 121400
11.35 0.1*3 11.78 1.00 35500 125 1. 00 35500
11*. 95 0.36 15.31 1.30 146200 205 1.64 58300
P = Technical Scaling Parameter = J_(SFCxOPR)+ 2W 1
T J
SFC = Specif!
OPR = Over-AI
W = Engine
T = Engine
c Fuel Consumption
1 Pressure Rat io
Dry Weight
Thrust
Base Iine Engine
-------
130
TABLE 2k
FINAL COST/TIME RESULTS FOR TOTAL TURBINE
Cost
Seal i ng
Factor
0.35
0.35
0.35
0.35
0.35
0.35
1.00
1.00
1.00
1.00
1.00
1.00
1.6it
1.64 .
1.64
1.64
1.64
1.64
Engine
Class
Tl
T 1
T 1
T 1
T 1
Tl
T2
T2
T2
T2
T2
T2
T3
T3
T3
T3
T3
T3
2T =T1
2T =T1
ST =TI
£T =TI
£T =TI
£T =T1
Baseline Control
Engine Method
T53 t,
T53 t2
T53 t3
T53 t^
T53 t$
T53 t&
JT8D t]
JT8D t2
JT8D t
JT8D . t^
JT8D t
JT8D t6
TF39 t,
TF39 t2
TF39 t3
• TF39 t^
TF39 t5
TF39 t6
+ T2 + T3 t]
+ T2 + T3 C2
+ T2 + T3 t3
+ T2 + T3 ^
+ T2 + T3 t5
+ T2 + T3 . t6
Total
Fami 1 ies
w
It 2
[i o
42
42
42
20
20
20
20
20
20
9
9
9
9
9
9
71
71
71 '
71
71
" 71
ENGINE POPULATION
Total
Engines
48,773
48,773
48,773
48,773
48,773
48,773
35,874
35,874
35,874
35,874
35,874
35,874
322
322
322
322
322
322
84,969
84,969'.-
84,969
84,969
84,969
84,969-
Total
Dev. and
Implement
Cost, $
643- OM
1116. OM
120. OM
257. OM
295. OM
196. OM
1293.0M
2226. OM
181. OM
412. OM
572. OM
258. OM
26. 8M
48. 4M
11. 3M
21.7M
13. 9M
23. OM
1963M '
3390M •
312M
691M
881M
477M .
Total
Dev. and
Implement
Time, yrs
5-71
71-10
51-8
71-10
5-61
61-9
5-71
71-10
51-8
71-10
5-61
61-9
5-71
71-10
51-8
71-10
5-61
61-9
5-71
71-10
51-8
71-10.
5-61
61-9
-------
TABLE 25
FINAL COST /TIME RESULTS
FOR TURBINE ENGINE POPULATION BY SEPARATE
CATEGORIES: AIR CARRIER, GENERAL AVIATION,
Engine Control
Class Method
--
Tl tj
Tl t2
tj
Tl tfy
T, t5
Tl '6
T2 "t,
T2 t2
T2 t3
T2 tk
T2 t
T2 t6
T3 t,
T3 t2
T3 t3
T3 t.
Note; Ci
Cost
Seal i ng
Factor
--
0.35
0.35
0.35
0.35
0.35
0.35
1.00
1.00
1.00
1.00
1.00
1.00
1.64
1.64
1.64
1.64
vi 1 Engi ne = Sum
. Development
Cost Per
Fami ly
$/FAMxlO
0.90
K80
0.99
1.80
0.62
2.20
0.90
1.80
0.99
.1.80
0.62
2.20
0.90
1.80
0.99
1.80
of Air Carrier and Genera
Impl ement
Cost Per
Engi ne
$/ENGxl03
12.4
21.3
1.6
3-7
5-5
2.1
35-5
69-9
^•5
10.5
15.6
6.0
58.3
100.0
7.4
17-2
Air
Carrier
Total
Cost
$x!06
19-2
34.5
7-7
14.9
9.8
15-5
243.0
418.0
39-5
87-0
108.7
61.5
10.0
19.0
7-4
13-7
MILITARY
1 Aviation Engines
Genera 1
Aviat ion
Total
Cost
$xl66
90.5
159.3
25.6
51-5
43.6
48. 1
17.8
3.1.0
4.0
8.3
8.2
7-1
0.0
0.0
0.0
0.0
Civil
A vi at ion
Total
Cost
$xl66
109.7
193.8
33.5
66.4
53.4
63.6 -
259-8
449.6
43.5
95.3
116.9
68.6
10.0
19.0
7.4
13.7
Mi 1 i tary
Avi at i on
Total
Cost
$xl66
533-0
921.0
87-0
190.0
240.0
131.0
1032.2
1774.4
137-9
317.4
454.9
190.6
16.8
29-4
3-9
8.0
-------
TABLE 25 (CONTINUED)
FINAL COST/TIME RESULTS FOR TURBINE ENGINE POPULATION BY SEPARATE
CATEGORIES: AIR CARRIER, GENERAL AVIATION,
Engine Control
Class Method
T3 t,.
T3 t6
ET=TI+T2 +T3 t.
ET=TI + T2 4T3 t2
ET=TI+1 2 +T3 t_
ET=TI+T2 +T3 t^
ET=TI+T2 +T3 t
ET+TI+T2 +T3 t.
Cost Development
Seal ing Cost Per
Factor Fami ly
1.6** 0.62
\.6k 2.20
__ •
.
__
—
—
__
Implement
Cost Per
Engi ne
25.6
9.9
—
--
--
--
--
--
Air
Carr i er
Total
Cost
5-9
16.0
272.0
^72.0
5^.0
116.0
125.0
93.0
MILITARY
Genera 1
Aviation
Total
Cost
0.0
0.0 .
108.0
192.0
29.0
61.0
52.0
55.0
Civi 1
Aviation
Total
Cost
5-9
16.0
380.0
66*t.O
83.0
177.0
177.0
1^8.0
Mi 1 i tary
Aviat i on
Total
Cost
7.8
7.0
1583.0
2726.0
229.0
51^.0
70k. 0
329.0
-------
133
TABLE 26
FINAL
COST/TIME RESULTS FOR TOTAL PISTON ENGINE
POPULATION .
Cost
Seal i ng
Factor
1.00
1.00
1.00
1,00
1.00
1.00
1.00
Engi ne
Class
PI
PI
PI
PI
PI
PI
PI
-
Baseline Control
Engine Method
Aircraft
Piston P.
Aircraft
P i s ton ?2
Ai rcraft
Piston P.
Ai rcraft
Piston P.
Aircraft
Piston P_
Aircraf t
P I s ton P.
Aircraft
Piston ?7
Total
Fam i 1 i es
35
35
35
35
35
35
35
Total
Engines
136,166
136,166
136,166
136,166
136,166
136,166
136,166
Total
Dev. and
Implement
Cost, $
176. 5M
453. 6M
564. 4M
453. 6M
90. 8M
98. 7M
276. 5M
Total
Oev. and
Implement
Time, yrs
61-8
8-11
71-10
8-11
61-8
6-7
61-71
-------
TABLE 27
FINAL COST /TIME RESULTS FOR PISTON ENGINE POPULATION BY SEPARATE
CATEGORIES: AIR CARRIER, GENERAL AVIATION,
Note: Civil Engine = Sum
Engi ne
Class
--
PI
PI
PI
PI
PI
PI
PI
Control
Method
--
P]
P2
P3
pit
P5
P6
P7
Cost
Seal i ng
Factor
--
1.00
1.00
1.00
1.00
1.00
1.00
1.00
. Development
Cost Per
Fami ly
$/FAMxl06
0.27
0.73
0.6it
. 0.73
0.25
0.11
0.13
of Air Carrier and Genera
Implement
Cost Per
Engi ne
$/ENGxl63
1.23
3.15
3.98
3.15
0.60
0.70
2.00
Air
Carr i er
Total
Cost
$x!06
0.0
0.0
0.0
0.0
0.0
0.0
0.0
MILITARY
1 Aviation Engines
General
Aviat ion
Total
Cost
$xl66
17**. 5
itit8.it
556.8
Mi8.7
89.7
97.6
273-3
Civi 1
Avi at ion
Total
Cost
$xl66
17^.5
itit3.it
556.8
itit8.it
89.7
97-6
273.3
Mi 1 i tary
Aviat ion
Total
Cost
$xl66
2.0
5.2
6.3
5.2
1. 1
1. 1
3.0
-------
TABLE 28
IMPLEMENTATION COST/TIME SAMPLE CALCULATION FOR "PRODUCTION" TURBINE ENGINES
Enq i ne
JT8D
JT8D
JT8D
JT8D
JT8D
JT8D
Additional
Insta 1 lat ion
Control Cost Per'
Method Enqine
$/Eng x lo"3
t, 1.0
t2 3.0
t3 0.5
t|, 1-5
t 1.8
t, 1.0
OF EX
10 Years
Total
Add! t ional
1 nsta 1 lat i on
Cost Per
Enqine
$/Eng x 10"3
12.0
2.0
6.0
7.2
ISTING DESIGN
Cont i nu i nq
Add! t iona 1
Cost/Engine/
Year
$/Eng/Yr x
2.5
0
0
0.76
0
10 Years
Cont i nu i nq
Additional
Cost Per
Enqine
$/Eng x 103
25.0
0
0
3.0
0
10 Years
Total
Implementa t ion
Cost Per
Enqi ne
$/Eng x 103
29.0
2.0
6.0
10.2
Effect i ve
Product ion ,
Start Date
1977
1979
1977
1979
1976
1978
This date assumes the control system development effort is initiated 1/1/72 and that the maximum
development, test ing, and tooling time is required, as tabulated in Table 15-
-------
TABLE 29
IMPLEMENTATION COST/TIME SAMPLE CALCULATION FOR "PRODUCTION" PISTON ENGINES
OF EXISTING DESIGN
Enq i ne
Pi ston
Piston
Pi ston
Piston
Piston
Piston
Piston
Add! t iona 1
1 nsta 1 la t ion
Control Cost Per-
Method Enqine
$/Eng x 103
Pj 0.200
P2 0.500
P3 0.^*75
P^ 0.500
P5 0.150
P6 0.075
P., 0.100
7
10 Years
Total
Add i t i ona 1
Insta 1 lat ion
Cost Per
Enq i ne
$/Eng x 103
0.1+00
1.000
0.950
1.000
0.300
o. 150
0.200
Cont i nu i nq
Add i t iona 1
Cost/Enqi ne/
. Year
$/Eng^Yr x
0.030
0. 11+2
0.230
0. 1i»2
0
0.050
0.100
10 Years
Cont i nu i nq
Add i t iona 1
Cost Per
Enqi ne
$/Eng x 103
0.30
1.1+2
2.30
1.1+2
0
0.50
1.00
10 Years
Tota 1
Imp 1 emen ta t i on
Cost Per
Enqi ne
$/Eng x 10 3
0.70
2.1+2
3.25
2.^42
0.30
0.65
1.20
Effect i ve
Product i on,
Start Date'
1975
1978
1977
1978
1975
This date assumes the control system development effort is initiated 1/1/72 and that the maximum
development, testing, and tooling time is required, as tabulated in Table .17-
-------
137
TABLE 30
IMPLEMENTATION COST/TIME FINAL RESULTS FOR "PRODUCTION" ENGINES-
Enqi ne
Class
Tl
Tl
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T2
T2
T3
T3
T3
T3
T3
T3
PI
PI
PI
PI
PI
PI
PI
TURBINE
Control
Method
t,
tz
t3
tk
t5
t6
t,
t2
'3
|5
t]
t2
t3'
t^
'5
pl
P2
P3
Pi
4
P5
P6
P7
AND PISTON
Seal i nq
Factor
0.35
Q.35
0.35
0.35
0.35
0.35
1.00
1.00
1.00
1.00
1.00
1.00
1.61*
1.61*
1.61*
1.61*
\'.ll
1.00
1.00
1.00
1.00
1.00
1.00
1.00
ENGINES OF. EXISTING
10 Year
Total
Implementat ion
Cost Per
Enq i ne
$/Eng
101,50
19,000
700
2,100
3,570
1 ,1*00
29,000
51*, 1*00
2,000
6,000
10,200
1*7,600
89,200
3,280
9,81*0
16,700
6,560
700
2,1*20
3,250
2,1*20
300
650
1,200
DESIGN
Implementat ion
Start Date
1977
'1979
1977
1979
1976
1978
1977
1979
1977
1979
1976
1978
1977
1979
1977
1979
1976
1978
1975
1978
1977
1978
1975
1971*
1971*
-------
138
TABLE 31
COST/TIME
Item Unit
Design Cost $
Prototype
Hardware Cost $
Testing Cost $
Cost of
1 ncorporation of
Prototype Design
into Demonstrator
Engine $
Total
Demonstrator Engine
Development Cost $
Prototype
Development Time Yrs
Fraction of
Development Cost
Attributable to
Emission Control %
Fraction of
Development Time
Attributable to
Emission Control ' %
RESULTS FOR FUTURE TURBINE ENGINES
New Combustor .. . . , . .
,. Variable Geometry
_ . T Combustor
Current Type
150K 300K
180K 280K
620K 740K
850K 1000K
1800K 2240K
2.0 3.5
0.0 34
0.0 43
Staged Injection
Combustor
550K
360K
850K
900K
' 2660K
5.0
47
60
Fraction of Engine
Purchase Price
from Combustor
k.S
8.5
7.0
-------
139
TABLE 32
Alrcraft
Class
2
3
4
5
6
Averaqe
Number
of
Enqi nes
£e_r
Ai rcraf t
4
4
2.6
2.5
2.1
REDUCTION IN EMISSION
INCREASE
CO
Uncontrol led
Idle Emissions
Per Enqine Of
Grams Per Hour
427000
68600
26000
5800
26700
FACTORS FOR
IN IDLE POWER
Pol
100 PER CENT
lutant
Hydrocarbons
Control led
Emiss ions
As Per Cent
Uncontrol led
Emissions
58
62
62
20
59
Uncontrol led
Idle Emissions
Per Enqine
Grams Per Hour
10500
30800
3540
1900
3130
Control led
Emissi ons
As Per Cent
. Of Uncontrol led
Emi ss i ons
108
91
71
30
61
-------
\ko
TABLE 33
REDUCTION IN TAXI AND IDLE EMISSIONS RESULTING FROM THE
USE OF THE MINIMUM NUMBER OF ENGINES FOR TAXIING
Number
Aircraft of
Class Engines
2 4 to 2
3 4 to 2
4 3 to 2
2 to 2
2.6 to 2 mean
5 4 to 2
2 to 2
2.5 to 2 mean
6 4 to 2
2 to 2
2.1 to 2 mean
2 4 to 1
3 4 to 1
4 3 to 1
2 to 1
2.6 to 1 mean
5 4 to 1
2 to 1
2.5 to 1 mean
6 4 to 1
2 to 1
2.1 to 1 mean
Control
Rate as
led Emission
a Per Cent of
Uncontrol led
Emiss
CO
29
31
42
62
48
10
20
16
30
59
56
15
15
21
31
24
5
10
8
15
30
28
ion Rate
Hydrocarbons
54
45
48
71
55
15
30
24
30
61
58
27
22
24
35
27
7
15
12
15
30
29
-------
TABLE 34
TOTAL AIRCRAFT
Pol lutant
CO
NOx
so2
particulates
lead
hydrocarbons
reactive
hydrocarbons
aldehydes
Approach
704
302
163
175
0.0205
843
6.36
111
Landing
288
1.09
2.81
1.25
0.0042V
117
0.253
3.81
EMISSI
Taxi
8720
33.2
67.6
37.7
0.153
3520
6.06
108
ONS FOR 1970
Idle &
Shut-
Oown
grams
32k
0.678
2.41
10.7
0.00106 0
141
0.127
4.38
AT LOS ANGELES INTERNATIONAL
Main-
tenance
x 10'6
864
50.5
22.5
26.2
.0241
426
0.581
13.2
Start-up
& Idle
728
2.27
5.63
3.12
0.0127
293
0.505
9.01
Delay
at
Runway
1360
5.16
10.5
5.87
0.0238
548
0.9*O
16.8
AIRPORT
Take-
Off
87.1
246
400
103
0.0155
29.8
4.49
2.87
C 1 imb-
Out
115
293
444
118
0.0502
39.1
6.10
3.22
Fuel
Dump'
ing
0
0
0
93. ^
0
93. ^
17.2
0
-------
TABLE 35
PERCENTAGE REDUCTION IN TOTAL AIRCRAFT EMISSIONS DUE TO
AVOIDING RUNWAY DELAYS AT LOS ANGELES INTERNATIONAL AIRPORT
Pol lutant
CO
NOx
so2
participates
lead
hydrocarbons
reactive
hydrocarbons
aldehydes
Delay
Mode
Emissions
Grams Per
Year x 1Q-&
1360
5.16
10.5
5.8?
0.0238
5^8
0.9^3
16.8
Total
Emissions
Grams Per
Year x 10'°
13200
93^
1120
57^
0.305
6060
U2.7
273
Controlled
Emi ss ions
Per Cent
Of Un-
Control led
Emiss ions
90
99.5
99
99
93
91
98
-------
143
TABLE 36
Ai rcraf t
Class 1
Class 2
Class 3
Class 4
Class 5
Class 6
Diesel
Fuel led
Vehicles
CO
1*5900
9770
15700
3870
829
3210
EMISSIONS FOR TAXI MODE
Reactive
Aide- Hydro-
NO S0» hydes carbons
612' 1160
321 145 39.5 2k]
15.1 115 222
3k. 2 4.13 3.27
189
18.1 87.9 25.0
Total
Hydror
carbons
200
2410
7040
526
271
376
Partic-
Lead ulates
0
236
— - 46.5
48.5
20.1
3.87
Tractor
439 1030 91.1 6.13
51.1
20.4
-------
TABLE 37
PERCENTAGE REDUCTION IN TOTAL AIRCRAFT EMISSIONS DUE TO
ELIMINATION
Pol lutant
CO
NOx
so2
ti culates
lead
Irocarbons
eactive
Irocarbons
lehydes
OF THE TAXI MODE AT LOS
Delay
Mode
Emissions
Grams Per
Year x 10 ~°
8720
33.2
67.6
37.7
0.153
3520
6.06
108
ANGELES INTERNATI
Total
Emiss i ons
Grams Per
Year x 10 ~6
13200
93^
1120
574
0.305
6060
42.7
273
ONAL AIRPORT
Control led
Emi ss ions
Per Cent
Of Un-
Control led
Emi ssions
9b
94
93
50
42
86
60
-------
Total
145
TABLE 38
POLLUTANTS FROM AUXILIARY POWER UNIT
For Each Mode in Grams
Mode
Taxi
Park
Taxi
Ascent
CO
19.7
157
39.3
19.7
NOx
40.5
324
81.1
40.5
Hydrocarbons
27.U
219
5^.7
27.4
Participates
6.84
54.7
13.7
6.84
236
486
328
82.1
For Los Angeles International Airport For 1970
™Hydrocarbons"
Em!ss ions
Without
APU as a
Per Cent
of Un-
Controlled
Emissions
NOx
Participates
99.5
98.5
96
-------
TABLE 39
COMPARATIVE REDUCTIONS RESULTING FROM CONTROL
METHODS APPLIED TO LOS ANGELES INTERNATIONAL AIRPORT
Controlled Emissions as Per Cent
of Uncontrolled Emissions
Control Method C0_ Hydrocarbons
1. Increase engine idle rpm 71 93
2. Increase idle rpm and use
minimal engines for taxi:
a. two engines 53 66
b. single engine 39 51
3. Eliminate delays at gate
and runway 90 91
k. Transport passengers be-
tween terminal and air-
craft 100 100
5. Tow aircraft to avoid taxi
emissions 3^ 42
6. Avoid use of aircraft auxi-
liary power units 99.5 98.5
7. Control emptying of fuel
drainage reservoirs 100 98.4
-------
TABLE **0
BASIS FOR ESTIMATING COSTS OF GROUND OPERATION CHANGES
AT LOS ANGELES INTERNATIONAL AIRPORT
Control
Method
Increase
Idle
Speed
Minimal En-
gi ne Taxi :
2 Engines
1 Engine
Control led
Gate
Departure
Passenger
Transport
Ai rcraft
Towi ng
Ground-Based
APU
Fuel Drainage
Equ i pment
Land
Cost
Construe t ion
Cost
Equipment
Cost
Automati ng
Cost
18 Acres at
$50K per Acre
90 Acres at
$50K per Acre
18 Acres at
$500K per Acre
90 Acres at
$500 per Acre
IBM 360/65
75 Vehicles
$200K per
Vehicle
25 New Ve-
hicles $30K
per Vehicle
37 Ai r Supply
at $20K
37 Electrical
at $15K
75 Devices at
$500
25 Man-Years
$60K per Man-Year
3 Man-Years
$60K per Man-Year
8 Man-Years
$60K per Man-Year
Per Annum
Operating Cost
Change
Fuel: 600 Ib per Engine-
Hour at $O.OVlb, 360K
Engine-Hours
Save 90K Engine-Hours
Add 200 Ib per Hour
Fuel for 270K Engine-
Hours
Save 227K Engine-Hours
Add 600 Ib per Hour
Fuel for 133K Engine-
Hours
Save 1200 lb-Fue.1 per
Engine-Hour frOK Engine-
Hours
Save 180K Engine-Hours
Spend $frOK Labor, $20K
Fuel per Vehicle
Save 360K Engine-Hours
Spend $UOK Labor, $20K
Fuel per Vehicle
Spend 150K Crew Hours
Spend $20K Fuel per
Vehicle
Add 75 Man-Years
-------
TABLE
Control Land
Method Cost
Increase
Idle
Speed
Minimal En-
gi ne Taxi :
2 Engines
1 Engine
Controlled $900K
Gate
Departure
Passenger $**500K
Transport
Aircraft
Towi ng
Ground-Based
APU
Fuel Drainage
IMPLEMENTATION COST AND
LOS ANGELES 1
Construction Equipment
Cost Cost
~ . --
__
..
$9000K $^OOOK
$^5,OOOK $15,OOOK
$750K
$1295K
$38K
TIME FOR OPERATIONS CHANGES
NTERNATIONAL AIRPORT
Total
Automating Initial
Cost Cost
$0
$0
$0
$1500K $l5,i+OOK
$180K $6^,680K
$^80K $1230K
$1295K
$38K
AT
Per Annum
Change in Cost
of Operation
$8500K
^$3000K
-$7500
-$1560
-$^000
to $5000K
+$** 17, ooo
$1500K
$3000K
T ime
Requi red
Negl i gible
b Months
I Year
5 Years
2.5 Years
1 Year
6 Months
6 Months
Equi pment
CO
-------
TABLE 42
FACTORS AFFECTING FEASIBILITY OF
OPERATING CHANGES AT LOS ANGELES INTERNATIONAL AIRPORT
Control
Method
Increase
Idle Speed
M i n i ma I
Engine Taxi
Control led
Gate
Departure
Passenger
Transport
Ai rcraft
Towi ng
Ground-Based
APU
Fuel Drainage
Equi pment
Implementation
Requires
1. Pi lot Procedure
Change
1. Pilot Procedure
Change
2. Fire-Protection at
Runway End
1. Automated Traffic
Control
2. Interim Parking
Area
I. Mobile Lounges
2. Parking Area Near
Runways
1. Tow Vehicles
2. Revised Schedules
1. Air and Electrical
Supply Un i ts
1. Equipment and
Personnel
Advantages Other
than Emissions
1. Use Less Fuel
for same thrust
I. Expedites Airport
Traffic
1. Use Less Fuel
1. Use Less Fuel
1.
Constraints and
D i sadvantages
Limited by Braking
Capaci ty
Limited by Jet Blast
when Starting from
Dead Stop
Complicated System
Requires Continuous
Updating
1. Requi res Ai rport
Expansion
1. Requires Much More
Taxi Time
I. Clutters Parking
Area
1. Adds a Task to
Aircraft Service
Procedure
-------
TABLE *Q
CURRENT RANGES OF AIRCRAFT ENGINE EXHAUST EMISSION CONCENTRATIONS
Pollutant
Spec ies
Total
Hydrocar-
bons , ppmC
CO
ppm
NO
ppm
NOx
ppm
(as N02)
Dry Part.
mg/m3
Total Part.
mg/m3
a?
Total
Alde-
hydes
ppm
Turb i ne
Idle
75-
1025
100-
1600
1-
10
5-
19
0-
200
500- .
700
0.9-
2.5%
0.9-
60
Approach
2-
280
30-
\t*o
10-
1*0
10-
60
5-
150
300-
550
].k-
3-2%
0-
20
Cru i se
0-
150
0-
85
10-
110
15-
165
6-
60
200-
550
1.5-
3-2%
0-
20
Take-Off
0-
55
0-
70
7-
125
25-
300
2-
150
200-
i*50
2.0-
i». 1%
0-
30
Piston
Taxi .
3,000-
30,000
3%-
12%
70-
850
6-
12%
Idle
2,000-
30,000
. 5%-
11%
80-
1300
6-
11%
27
Ascent
• 900-
10,000
6%-
12%
90-
600
t*-
!*»%
16
Cru i se
Rich
900-
2800
.5%-
11%
80-
700
7-
13%
33
Cruise
Lean
200-
1800
o.^»%-
5%
600-
4800
11-
15%
18
Descent
900-
35,000
l%-
11%
• 75-
750
-
5-
12%
51
vn
o
-------
TABLE Mt
151
INSTRUMENTATION ACCURACY-REQUIREMENTS FOR EXHAUST GAS ANALYSIS
Pol lutant
Species
Total Hydrocarbons
ppmC
CO
ppm
NO
ppm
NOx (as NO )
ppm
DRK Particulates
mg/m3
Total Particulates
mq/m3
CO
2
(%)
Total Aldehydes
(as HCHO)
Recommended
Ranae
0-10
0-100
0-1000
0-10,000
0-5%
0-10
0-100
0-500
0-2500
0-20,000
0-15%
0-10
0-50
0-250
0-1000
0-5000
0-10
0-50
0-250
0-1000
0-5000
0-10
0-50
0-100
0-250
0-100
0-1000
0-2%
0-5%
0-15%
0-20%
0-10
0-50
0-100
Recommended
Accuracy
+5% full scale with
propane calibration gas
+2% ful 1 scale with
propane calibration gas
+ 1% full scale with
propane calibration gas
+1% full scale with
propane calibration gas
+1% full scale with
propane calibration gas
+5% full scale
+2% full scale
+1% full scale
+1% full scale
+1% full scale
+1% full scale
±5% full scale
±2.5% ful 1 scale
+2% full scale
+2% full scale
+1% full scale
±5% full scale
±2.5% full scale
+2% full scale
+2% full scale
+1% full scale
- +5% full scale
+5% full scale
+5% full scale
±5% full scale
+5% full scale
+5% full scale
+1% full scale
+1% full scale
•*•!% full scale
+1% full scale
+5% full scale
+2% full scale
+2% full scale
-------
152
TABLE kS
EXHAUST GAS ANALYSIS METHODS IN USE AT 17 ORGANIZATIONS
Analysis Method Number Using Method
Carbon Dioxide
Flame lonization (after conversion to methane) (1)
Gas Chromatography ' (2)
NDIR
Carbon Monoxide
Flame lonization (after conversion to methane) (1)
Gas Chromatography (2)
NDIR (17)
Hydrocarbons
Flame lonization with Heated (*v 350-^00 deg F)
Sample Line (8)
Flame lonization, Unheated ( <.300 deg F line) (5)
Flame lonization, Line Temperature not Reported (5)
High Temperature Oxidation to CO, ( <£ 300 deg F
line) L (1)
NDIR (1)
Nitric Oxide
NDIR (12)
Saltzmann Method (2)
PDS (2)
Chemiluminescent Method (1)
Electrochemical Cell (2)
Mass Spectrometer (1)
Faristor (1)
Nitrogen Dioxide
NDUV (*+)
NDIR (by conversion to NO) 0)
-------
153
TABLE kS (CONTINUED)
EXHAUST GAS ANALYSIS METHODS IN USE AT 17 ORGANIZATIONS
Analysis Method Number Using Method^
Nitrogen Oxides
Electrochemical Cell (2)
Chemiluminescent Method (2)
NDUV (assuming exhaust is NO and NO.; NO previously determined) (2)
PDS (2)
Faristor (1)
Particulates
Mass Determination (k)
Mass Determination and Sizing by Electron (2)
Microscope (2)
Mass Determination and Wet Chemical Analysis (2)
Smoke
Per SAE, ARP 1179 (10)
Other (3)
Sulfur Dioxide
Calculated (6)
Faristor (2)
Aldehydes
MBTH (6)
-------
15**
FIGURES
-------
-------
90
80
70
60
0)
3
I
.d
- 50
O
O
o
-Q
X
V
-o
c
c
o
I/I
'i
30
20
10
480©
-------
18
16
12
i
ja
o
o
o
X
0>
c
o
I/I
I/I
10
O Data from Reference 6.
• Data from Reference 118,
Tables IV-300 through
IV-312.
28 (t
Tl T2 T3 Tl T2 T3
Idle Approach
Engine Class and Power Level
Q)
i
1
Tl T2 T3
Take-Off
FIGURE 3 - TURBINE ENGINE EMISSION DATA. NITROGEN OXIDES (AS NO?)
157
-------
-------
Assumpt I ons
Turbi ne Engi nes
1. TBO = Time Between Overhauls
= 5000 hrs = 2}2 years
2. Engine Life = 10 years
159
Pi ston Enqi nes
1 . TBO = 1500 hrs = 5 years
2. Engine Life = 10 years
Cost
Test!ng
Tooli ng
Cost
Servi c
Cost
4
/
ne
nt,
i
e ^
\
Initial
Add i t iona
Instal lat
Cost
%
1
ion
1
\ '
1
»>
Y////////////;
TBO
— Ini
•>
»
t
TBO
ial Con
1
•»
<•.
V(
le
TBO
|
^
*•
TBO
;rsion Time
I
—
Co
--~ Ad
L Co
^ Ad
In
Cc
f
t
T
Cont i nuous
Add i tional
Cost per Year
Add!ti onal
Installation
Major Overhaul
Ti mes
Development,
Testing &
Tooli ng
Time
Time (years)
FIGURE $ - EMISSION CONTROL COST/TIME MODEL FOR
TYPICAL AIRCRAFT ENGINE FAMILY CURRENTLY IN-SERVICE
-------
160
Class
Class
Class
9
322
FAMILIES
ENGINES
1
/
TF39
[1 1
t?
tl
tk
! Development il Implementation
S/Fam
X 10"° Years
o.q
1.8
1.0
1.8
t<; jl 0.6
t6
2.2
S/Eng
x lO"^ Years
2-5-5 il 58.3
5-7-5 1! 100.0
3-5-5
5-7-5
2.5-4
4-6.5
' 7.4
17.2
25-6
9-9
II
10
10
10
10
10
10
20 FAMILIES
35,874 ENGINES
JT8D i
t] !
t?
t* \
Deve lopment
S/Fam
x. 10~6 Years
0.9
1.8
1.0
t'k li I -8
tj; |! 0.6
tfi i
1
2.2
2.5-5
5-7-5
3-5-5
5-7-5
2.5-4
4-6.5
Implementat ion
§/tng
x. 10--* Years
35.5
60.9
1 4.5
10.5
! 15.6
6.0
10
10
10
10
10
10
42 FAMILIES
48,773 ENGINES
t]
t?
[3
tl,
:; Class
lj
IS x 10"6
;i 26.8 i
lj 48.4 !
'! 11.3
'I 21.7 i
T3
Years
5-7.5
7.S-10
5.5-8
7.5-10
t5 li 13.9 ' 5-6.5
t.
li 23.0 i
6.5-9
1! i
i! Class T2
1
i
5xlO-6 Ye
a r s "•'•'
t, li 1293 ! 5-7.5
t0 IJ2226 1 7-
13 '
tu !
181 : 5-
412 7.
5-10
5-8
5-10
tq !! 572 5-6.5
tg |
!
258 6.
i
5-9
• "!
*To complete initial
convers ion
/ jj Development
151 ji $/Fam
llx 10"6 Years
t] il 0.9
t2 1! 1.8
17 li 1.0
t^ II 1.8
C5 i! 0.6
tg, 11 2.2
2-5-5
5-7-5
3-5-5
5-7.5
2.5-4
1 mplementat i on
U/Eng
Ix 10"3 Years
12.4
21.3
10
10
1.6 | 10
1 3-7 i 10
5-5
4-6. b il 9 1
•^ 11 ^ • '
li ! li
10
IU
J
FIGURE 6 - SUMMARY OF TOTAL. TURBI NE ENGINE
.XV
POPULAT
Class Tl
!$ x 10"6 Years
t, il 643 1 5-7-5
t2 II 1116! 7-5-10
t, j| 12C ! 5-5-8
t^ !| 257 i 7-5-10
tj.
t^
| 295 i 5-6.5
1 196 ! 6-5-9
I 1
ION
COST/TIME ANALYSIS PROCEDURE
-------
161
Class PI
35 FAMILIES
136,166 ENGINES
Opposed
Piston
Dl
D2
P-,
Pr
! Development
:1$/Fam
Jix 10"3 Years
iP272
!! 728
li 641
il 728
i! 251
p£ II 105
P7
!j 127
1.5-3
3-6
i Implementation
S/En.g
|c 10~3 Years
1.23
10
3.15 1 10
2.5-5 li 3.98
10
3-6 II 3.15 ! 10
1.5-3 ! 0.60
1-2
1.5-2.5
0.70
2.00
10
10
10
D,
P2
P3
Pz,
PC
P6
P. . 1
i Clas
$ x 10"6
176.5 •
^53- 6 i
56k. k l
453-6;
90.8;
1 98.7!
1.276.5 1
s PI
Years
6.5-8
8-11
7.5-10
8-11
6.5-8
6-7
6.5-7.5
FIGURE 6A - SUMMARY OF TOTAL PISTON ENGINE
POPULATION COST/TIME ANALYSIS PROCEDURE
-------
162
Class T3
Class T2
Class Tl
7 FAMILIES
6k ENGINES
r
/
I im
ti
to
13
tL
tr
t£
Development
S/Fam/.
Ix 10"b Years
Implementation
$/Eng,
x 10 3 Years
O.q 1 2.5-5 li 58.3
1.8 5-7.5
i.o
1.8
0.6
2.2
3-5.5
5-7-5
2.5-4.
4-6.5
100.0
1 7.4
17.2
25.6
q.q
10
10
10
10
10
10
A
10 FAMILIES
6,576 ENGINES
/
^JT8D
t,
t?
I Development
;$/Fam
Ix 10"b Years
0.9
1.8
t, || 1.0
tif il 1.8
tc
ti
0.6
2.2
2.5-5
5-7-5
3-5-5
Implementat ion
$/Eng
x lO'-J Years
35-5
60.9
**-5
5-7-5 !! 10.5
2.5-Jf
i|-6.5
15.6
6.0
10
10
10
: 10
10
10
FAMILIES
ENGINES
/ li Development
T53 .$/Ta?T
|p( 10-b Years
ti II 0.9
t, !' 1.8
t-.
ti;
tr
t£
1.0
1.8
0.6
2.2
2.5-5
5-7.5
3-5-5
5-7-5
2.5-4
4-6.5
Implementat i on
5/Eng
x lO--* Years
12.4
21.3
1.6
3.7
5o5
2.1
10
10
10
10
10
10
ti
to
i Class T3
$ x 10" Years
10
! 1Q
5-7-5
7.5-10
t; !! 7 ! q.q-8
"
t^
t,.
t^
14 I 7.5-10
6
16
6 1
5-6.5
6.5-9
^To complete initial
conversion
FIGURE 7 - SUMMARY OF AIR. CARRIER TURBINE ENGINE
POPULATION COST/TIME ANALYSIS PROCEDURE
| Class
i $ x i cr6
t! II 243 !
to
T2
Years-
5-7.5
1 418 i 7-5-10
t; ii 40 •
tu
87 !
tq li 109 !
t6 H 62 ;
6 li i
5-5-8
7-5-10
5-6.5
6-5-9 :
t,
ro
t^J
t?
U
fr
Class Tl
$ x 10"6 Years
19
35
5-7. q
7.5-10
8 i 5.5-8
15
10
16
7-5-10
5-6.5
6.5-9
-------
0 FAMILIES
0 ENGINES
1
/
IE12
ti
to
t7
tii
t«;
t*
Development
$/Fam
x 10~b Ypars
0.9
1.8
1.0
1.8
0.6
2.2
2.5-i)
5-7-5
3-5.5
Implementation
$/Eng
x in-3 Ypsrs
58.3
100.0
7.4
5-7.5 II 17.2
2.5-4
4-6.5
25.6
q.q
to
10
10
10
10
10
Class T2
Class'Tl
2 FAMILIES
ENGINES
JT8D
Development
$/Fam
x ID'6 Years
t, :: 0.9
t2
ti
''i
tc
t6
1.8
1.0
1.8
0.6
2.2
2.5-5
5-7.5
3-5.5
5-7-5
2.5-4
4-6.5
Implementat ion
$/Eng
x 10"3 Years
35.5
60.9
4.5
10.5
15.6
6.0
10
10
10
10
10
10
16 FAMILIES
6,137 ENGINES
(^
t]
t2
t3
t'",
tq
tfi
Development
$/Fam,
x 10'6 Years
0.9
1.8
1.0
1.8
0.6
2.2
2.5-5
5-7-5
3-5.5
5-7-5
2.5-**
4-b.5
Implementat ion
$/Eng
x 10-3 Years
12.4
21.3
1.6
3.7
5.5
2.1
10
10
10
10
10
10
163
t]
1 Class T3
$ x 10"6 Years
0
U il 0
t; ii o
U I 0
tp
! 0
tg ! o
1
5-7-5
7.5-10
5.5-8
7-5-10
5-6.5
6.5-9
*To complete initial
conversion
FIGURE 8 - SUMMARY OF GENERAL AVIATION TURBINE ENGINE
POPULATION COST/TIME ANALYSIS PROCEDURE
Class T2 '
$ x 10'6 Years^
t , il 18
to
t^
tL\
t5'
tr
31
k
8
8
7
5-7. «;
7-5-10
5-5-8
7-5-10
5-6.5
6.5-9
1
Class TI
$ x 10"6 Years
ti !l 91
to
t^
tL
^
tft
159
26
52
^
<48
5-7-5 !
7-5-10
5-5-8
7-5-10
5-6-5
b.i-9
-------
Class T3
7 FAMILIES
64 ENGINES
1
/
TF39
Development
$/Fam
x IO"6 Years
t] li 0.9
t?
1.8
ti j! 1.0
t,-;
tc
u
]«8
0.6
2.2
Impl ementat ion
$/Eng
x 10'3 Years
2.5-5 il 58« 3
5-7.5 11100.0
3-5.5
5-7.5
2.5-4
4-6.5
7.4
17.2
25.6
9.9
I
10
10
10
10
10
10
12
7,024
FAMILIES
ENGINES
/
JT8D
t.
t^
Development
$/Fam,
x 10 Years
0.9
1.8
t; it i.o
t,
tc
t6
1.8
0.6
2.2
2.5-5
Implementat ion
$/Eng
x 10"-* Years
35.5
5-7.5 ft 60.9
3-5.5
5-7.5
2.5-4
4-6.5
4.5
10.5
15.6
6.0
II
10
10
10
10
10
10
22 FAMILIES
7,251 ENGINES
164
t,
tn
tt
til
tc
t£
Class T?
$. x 10~6 Years
10.0
19.0
5-7.5
7.5-10
7.4 1 5.5-8
13.7 1 7.5-10
5.9
16.0
5-6.5
6.5-9
t,
to
'3
t7,
tc
t£
Class T2
$ x 10"6 Years*
260 ,
450
44
95
117
69
5-7.5
7.5-10
5.5-8
7.5-10
5-6.5
. 6.5-9
*To comp1e te initial
conversion
/
lii
t]
t?
13
t
tc
^
Development
$/Fam
x 10'6 Years
0.9
1.8
1.0
1.8
O.b
2.2
2.5-5
ij-/«.b
3-5.5
5-7.5
2.5-4
4-6.5
Implementation
$/Eng
x 10-3 Years
12.4
21.3
1.6
3-7
5.5
2.1
10
10
10
10
10
10
t]
t?
t*
t/,
tc
t^
Class Tl
$ x 10'6 Years
1 10
194
34
66
53
64
5-7-5
/.5-IO
5-5-8
7.5-10
5-6.5
6.5-9
FIGURE 9 - SUMMARY OF CIVIL .AVIATION TURBINE ENGINE
POPULATION COST/TIME ANALYSIS PROCEDURE
-------
165
Class
3*» FAMILIES
134,760 ENGINES
/ Ij Development
Opposed !i$/Fam_
Piston ilx 10'3 Years
pi !: 272
. P2 ij 728
P3 i| Ml
p4 ji /ZB
P5 il 251
p6 1! 105
P? I 127
! Implementat ion
fc/Eng,
be ID"3 Years
1.5-3 1! 1.23
3-6 ! 3-15
2.5-5
3-b
1.5-3
1-2
3-98
3. 15
0.60
0.70
1.5-2.511 2.00
10
10
10
10
10
10
10
1 Class
$ x 10"6
pi ii 17^.5i
p2 j! 448. k\
P3 i| 55b.b|
pk
P5
p6
M»8.M
89.7!
97.6!
P7 II 273.31
PI
Years i
6.5-8
8-11
7.5-10
8-11
6.5-8
6-7
6.5-7.5
NOTE: Air carrier piston engine population assumed negligible.
Therefore, air carrier population ° civil aviation population.
FIGURE 9A - SUMMARY OF CIVIL AVIATION PISTON ENGINE
POPULATION COST/TIME ANALYSIS PROCEDURE
-------
Class
Class T2
Class TI
2 FAMILIES
258 ENGINES
'
TF39
Development
$/Fam
x 10"b Years
ti II 0.9
to
t-.
J
tl
t7
J
L
1.8
1.0
1.8
0.6
2.2
2.q-t;
5-7.5
•}_c;_q
5-7.5
2.5-4
4-6.5
Implementat ion
$/Eng
x 10'3 Years
58.3
100.0
7.4
17.2
25.6
9.9
in
in
in
in
in
10
A
8 FAMILIES
28,850 ENGINES
JT8D
tl
t,
t.
t/i
C5
Development
Implementat ion
$/Fam |j$/Eng
x 10-6 Years Ijx 10"-> Y^^rc
0.9
1.8
loO
i.a
0.6
2.2
2.5-5 II 35.5
5-7.5
3-5.5
5-7.5'
2.5-4
4-6.5
60.9
4.5
10.5
15.6
6.0
10
10
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167
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168
FIGURE 11 - IMPLEMENTATION COST PER ENGINE VERSUS NORMALIZED
COST PARAMETERS FOR TURBINE ENGINE
-------
8000
per
hour
6000
4000
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•Fuel Flow
(Turboprop)
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FOR EACH AIRCRAFT CLASS ..
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170
CO
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FIGURE 13 - CO EMISSION FACTORS PLOTTED AGAINST POWER
FOR EACH AIRCRAFT CLASS
-------
Hydrocarbons
Emissions
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171
Class 3
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50
Per Cent
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FIGURE \U - HYDROCARBON EMISSION FACTORS PLOTTED
AGAINST POWER FOR EACH AIRCRAFT CLASS
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172
APPENDIX
INSTRUMENTATION
Introduction
The formation of the Committee on Aircraft Exhaust Emissions
Measurement (E-31) by the Society of Automotive Engineers in 1968
represents a significant step towards the development of acceptable
standards for characterization of aircraft engine exhausts. This com-
mittee has issued an Aerospace Recommended Practice (ARP-1179) on
"Aircraft Gas Turbine Exhaust Smoke Measurement" (Ref 55) that has been
widely accepted and adopted as a standard procedure by the aerospace
community. Furthermore, the committee is completing work on a "Procedure
for the Continuous Sampling and Measurement of Gaseous Emissions from
Aircraft Turbine Engines" (Ref 36) that specifies instrumentation,
sampling, and test procedures that shall be used for measurement of
carbon monoxide, carbon dioxide, nitric oxide, and total hydrocarbons
in turbine exhausts. Before being discharged of its responsibilities, the
committee will also examine procedures for odor characterization and
measurement of particulates also in turbine engine exhausts. They will
also reexamine the areas of emissions sampling procedures in the light of
discoveries made subsequent to their recommendations on smoke measurement.
The forthcoming recommendations of the E-31 Committee on the
characterization of aircraft gaseous emissions reflect a state-of-the-
art analysis of existing measurement hardware. The committee's report
does not, however, discuss alternative measurement techniques; it
instead specifies standard measurement techniques and procedures that
are to be followed in the aerospace community to insure the validity
of data comparisons from one test program to another.
Consequently, to complement rather than duplicate the E-31
Committee's work, this discussion is directed towards various alternative
instruments both available now, and under development, that cpuld be
used in an aircraft emissions measurement test program. This
discussion will not include comparison of the cost and performance of
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173
the various brands of a specific type of instrument; the reader is
referred to a recent study by Arthur D. Little, Inc. for such a com-
parison (Ref 60). Reference 61 also contains information on cost and
detection principles for a number of commercially available continuous
moni tors.
In this Appendix, measurement techniques are discussed for the
following ,pollutant classes:
Carbon Monoxide (CO)
Carbon Dioxide (COj
Total Hydrocarbons
Nitric Oxide (NO)
Total Nitrogen Oxides (NOx)
Sulfur Dioxide (S02)
Aldehydes
Particulates
Smoke
Odor
The discussions include, where data are available, reference to performance
characteristics, sensitivity, response time, costs, ease of use, auxiliary
equipment requirements, and portability for each specific type of instru-
ment. Problem areas indigenous to each instrument type are enumerated;
instrumentation under development is identified; and, wherever applicable,
the recommendations of the SAE E-31 Committee are cited.
Measurement Techniques
Carbon Monoxide
As discussed by Broderick et al (Ref 59), carbon monoxide
emissions in aircraft engine exhausts are now measured by nondispersive
infrared analyzers, by electrochemical analyzers, by mercury vapor
analyzers, and by gas chromatographs. At the present time, the most
widely accepted and used of these instruments is the NDIR analyzer.
The instrument provides on-line analysis of emissions, has been suc-
cessfully used in the field as a portable unit (Ref 3), can be easily
-------
operated by unskilled personnel, and carries the recommendation of the
SAE E-31 Committee as an industry standard (Ref 36).
NDIR
In an infrared analyzer, radiant energy passes through a cell
containing a reference gas and a cell containing the sample gas. In
the sample cell, the radiation is absorbed by the components of interest
in regions where that specie has absorption bands. The percentage
absorption relates to the concentration of that specie. Interference
from other components of the sample gas that absorb in neighboring
bands is eliminated by optical filters or filter cells. In the reference
cell, attenuation of the reference beam is negligible.
After passage through the cells, the radiant energy passes
into a detector unit-- a closed container comprised of two compartments
separated by a metal diaphragm. Both compartments are filled with the
species of interest in the gaseous state. The incoming energy from the
sample cell heats the gas in one compartment while the energy from the
reference cell heats the gas in the other. The difference in incoming
energy causes a pressure differential in the detector that leads to a
deflection of the cell diaphragm.
Between the dual infrared energy sources is an optical chopper
that chops the energy beams at a prescribed frequency. This chopping
causes the diaphragm to pulse cyclically. Since the diaphragm is part
of an amplitude modulation circuit, the pulsing causes a concentration
related change in its capacitance that is ultimately relayed to a
recorder and/or controller as an electrical signal. Cost of an NDIR
analyzer is in the vicinity of $3500 with the cost dependent on the
user's choice of concentration level, dynamic range, and packaging
arrangement.
Infrared analyzers suffer from two significant deficiencies.
interference from other molecular species, and lack of sensitivity,
stability, and specificity at low concentration levels. For CO mea-
surement, the first of these deficiencies is primarily caused by the
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175
presence of C0_ and HO in the sample stream. This interference can,
fortunately, be largely eliminated by desiccants, absorbers, optical
filtersiand filter cells. However, until recently, the second deficiency
could only be circumvented by the use of alternative Instrumentation
(e.g., a gas chromatograph) for engines operating at high power levels
(low CO emission rates).
A state-of-the-art advancement in NDIR-instrumentation has
come about with the development of a-fluorescent source carbon monoxide
NDIR analyzer (Refs 62 and 63) • This analyzer eliminates all unwanted
infrared radiation from the sample source and thus from the analysis
procedure (i.e., there is no interference from other constituents of
the sample stream). The detector is typically solid state or pyroelectric
and hence, free from the .s.tabi 1 i ty problems associated with the typical
gas-filled detector (Ref>62) • The instrument uses two isotopes of CO
as sources of fluorescent radiation and operates on a single optical
path thus eliminating the requirement for a separate standard cell.
Although still in the prototype stage, the instrument has been accepted
by NASA for use on board the first orbiting sky lab (Ref-.£4). Prototype
costs are estimated at $10,000-$15,000. After commercialization, the
instrument is expected to reach a competitive cost position with existing
NDIR instruments.
Electrochemical
Electrochemical analyzers operate through a wet chemical process
where the transducer converts specie concentration to a current signal
by an electroxidation or electroreduction reaction. For carbon
monoxide determination this reaction is SCO + 10 i-p-
5CO + I. (Ref 65). The instrument is accurate at low concentrations
provided the sample stream.is properly dried to eliminate possible
interference from water. The units cost approximately $2000 to $2500
and are thought to.require operation by skilled personnel (Ref 59).
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176
Mercury Vapor Detectors
The basis of operation of these detectors is the reaction
between carbon monoxide and mercuric oxide: CO + HgO -—*-
CCL + Hg. The elemental mercury liberated in this reaction is measured
and related to the carbon monoxide content of the sample stream. Since
the analysis can be affected by hydrocarbon interference, sample lines
must be cooled to condense out these unwanted species. The primary
advantage of mercury vapor detectors is their reputed accuracy at low
concentration levels (Ref 59)-
Gas Chromatographs
All gas chromatograph instruments are comprised of six
basic elements: a carrier gas supply system, a sample injection system,
a separation column, a column oven, a detector, and a signal output
system. The heart of the system is the separation column which can be
either a flame ionization detector, a thermal conductivity detector,
or an electron capture detector.
In a flame ionization detector, the change in ion concentration
during combustion of organic compounds relates to the carbon content
of the sample stream. In a thermal conductivity detector, the difference
in the thermal conductivity of the species in the sample stream is
responsible for a different ability of each component to conduct heat
away from a set of filaments, causing a change in filament temperature.
The degree of this change is recorded by the signal detection system and
is proportional to each species concentration. The basis for operation
of an electron capture detector is the difference in the ability of
different compounds to-capture "free" electrons. Using nitrogen as a
carrier gas, the detector ionizes the nitrogen molecules to liberate
free electrons. The change in the electron concentration, recorded
as a change in current output, is a measure of the amount and electron
affinity of the specie(s) present.
Gas Chromatographs are primarily thought of as laboratory
tools for use with grab samples from aircraft engine exhausts. However,
by installation of an automatic sampling valve, a chromatograph can be
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177
easily adapted for continuous monitoring in an emissions measurement
program. Contrary to popular belief, chromatographs are easy to operate;
it is the interpretation of their data that presents a source of diffi-
culty to the unskilled operator.
Gas chromatographs offer the advantages of wide dynamic range
(0.1 - 1000 ppm) and high measurement accuracy. Although the basic
laboratory units are expensive (approximately $7000 including recorder),
the units can monitor several molecular species concurrently. Further,
2
one particular gas chromatograph, a small (occupies less than 1 ft
of bench space), light (35 lb), portable unit, has now been developed
to sell at $1250 plus $1000 for the recorder system. Such a unit would
be an excellent supplementary tool to an NDIR unit for low level emissions
monitor ing.
Supplemental
A wet chemical technique also exists for the determination
of CO (Ref 65.). In this technique, the sample gas is first cooled and
passed through an absorption train to remove unburned hydrocarbons,
C0_, and other interfering species. The stream is then heated
electrically,converting the CO to CO . The CO is then absorbed in a
standard barium hydroxide solution and the excess barium hydroxide
titrated with hydrochloric acid. The technique is accurate to a lower
limit of about 1 ppm. There is no known carbon monoxide monitor which
operates on this principle.
A second wet chemical technique for quantitative analysis of
carbon monoxide content in a gas stream involves the use of the carbon
monoxide indicator tube. When highly purified silica gel, impregnated
with ammonium molybdate and a solution of palladium or palladium oxide,
is digested in suIfuric acid it forms a si1icomolybdate which on
exposure to CO forms molybdenum blue. The depth of color in the detector
tube varies from faint green to deep blue in proportion to the amount
of CO present in the gas sample. This method can be on a continuous
basis for sampling CO by aspirating a metered flow of air through the
tube at a constant rate and observing the color change with respect to
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178
time. The procedure is not now known to be in use in monitoring air-
craft exhaust gases; it has, however, been used for sampling aircraft
turbine exhausts with some degree of success in the past (Ref 66).
Carbon Dioxide
Carbon dioxide is a major constituent of aircraft engine ex-
hausts. Present in percentage level quantities in both turbine and piston
engine exhausts, it is most frequently measured by NOIR analysis equip-
ment. Gas chromatographic techniques are also employed but generally
only for laboratory analyses of engine grab samples. Batch Orsat type
analyses have been employed in the past (Ref 50), but are no longer in
use.
The SAE E-31 Committee recommends NDIR instruments as the s_tan-
dard device for determination of C0_ in turbine engine exhausts (Ref 36).
A description of the principle of operation of NDIR analyzers and gas
chromatographs is presented in the discussion of carbon monoxide
monitoring equipment.
Total Hydrocarbons
The concentration of total hydrocarbons in aircraft engine
exhausts is most frequently measured with a flame ionization detector.
Optical spectrophotometers are also used (Ref 66); gas chromatographs
and mass spectrometers are used if determination of specific constituent
concentrations is required. In all cases,it is imperative that the sample
line to the instrument be maintained at 300 to 350 deg F to avoid conden-
.sation of the less volatile hydrocarbon constituents in the sampl«> <=» i-
FID
The principle of operation of flame ionization detector has
been previously discussed in the section dealing with carbon monoxide:
gas chromatographs. To reiterate, the flame formed by combustion of
pure hydrogen with air produces a negligible source of ions. If a
sample gas containing hydrocarbons is introduced into the flame, a
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179
complex ionization process occurs liberating a large number of ions.
By applying a voltage across the flame, a small ionization current is
established in the detector system. This current is then directly
proportional to the carbon atom concentration of the flame.
FIDs have been shown to have poor measurement characteristics
below about 10 ppm in turbine exhausts (Ref ^1), although they are
reputedly able to make measurements of hydrocarbon concentrations down
to 1 ppm. On the more positive side, FIDs can be used for on-line
analysis of emissions, have been successfully employed in the field
as portable units (Ref 3), can be easily operated by unskilled personnel,
and carry the recommendation of the SAE E-31 Committee as an industry
standard (Ref 36). Their cost is approximately $5500.
Optical Spectrophotometers
NDIR spectrometers similar to those used for CO and C02 can
also be used for- determination of total hydrocarbons in exhaust emis-
sions. George and Burl in (Ref 66), for example, report collection of
grab samples from aircraft exhausts and their analyses with an IR
spectrophotometer set at the 3**5Q^#. This technique clearly requires
elaborate calibration procedures and has therefore not seen wide
application in aircraft emissions measurement programs.
Gas Chromatography
The instrument best suited for the constituent analysis of the
total hydrocarbon measurement is the gas chromatograph. Linear tem-
perature programming is generally employed to elute all individual
organics with a sensitivity less than I ppb (Ref 67). The technique
is most frequently applied to grab samples of the exhaust stream.
FID units are not suitable for this type of measurement as they are
not sensitized for a particular compound but, instead, detect all
classes of unburned hydrocarbons (Ref 68).
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180
Mass Spectrometers
Time of flight mass spectrometers operate on a principle of
separation of species according to their mass number. The separation
is accomplished by ionizing the sample, accelerating the ionic species via a
grid system, and allowing the ions to drift through a region at the
nominal ion energy. Since heavier ions travel slower than those of
lighter mass, a separation of the different molecular constituents is
ach ieved.
Mass spectrometers are expensive units (about $15,000), require
the use of highly skilled operators, and are not suited for field use.
Their use in aircraft emissions analysis programs has been all but
nonexi stent.
Nitric Oxide and Total Oxides of Nitrogen
Nitric oxide and total oxides of nitrogen are measured by a
variety of overlapping techniques. These methods include classical
batch wet chemical colorometric procedures, electrochemical analyzers
similar to those used for measurement of carbon monoxide, nondispersive
infrared spectrometers for measurement of NO, nondispersive ultraviolet
spectrometers for measurement of NO , gas chromatographs, faristors,
and chemiluminescence monitors. The SAE E-31 Committee presently
recommends the use of NDIR units for measurement of NO, NDUV units for
measurement of NO , and makes no recommendation for total NOx monitoring
equipment (Ref 3&) • However, at this writing, chemiluminescence monitors
are undergoing extensive field testing by the EPA and may become the
industry standard for continuous measurement of NO and NOx.
Sampling problems associated with measurement of emissions
are discussed earlier in this report. However, it is imperative to
keep in mind that: (1) NOx can be reduced by CO if catalyzed at elevated
temperatures by any of a variety of the metallic surfaces that are
frequently employed in sampling lines; (2) NO can be similarly catalyzed
to NO^; and (3) N02 can be easj.l.y lost in the drying of the exhaust
sample prior to analysis . (Ref ^2).
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181
Wet Chemical Procedures
Many wet chemical procedures for the determination of nitric
oxide depend on the oxidation of the oxide to nitrogen dioxide. The
sample is bubbled through an acid potassium permanganate solution where
all of the nitric oxide present is converted to an equivalent amount of
NO. (Ref 69). The NO concentration is then determined by an optical
measurement of the color intensity produced by the reaction of the NO
with appropriate reagents. Since NO and N0_ are the primary nitrogen
oxide constituents of aircraft engine exhausts, it is appropriate to
test a given sample twice (or split the sample stream for individual
analyses)-- once for determination of the NO content of the NOx and
once for determination of the total NO and NO. in the sample. The NO
concentration is determined by difference.
The Jacobs and Hochheiser technique for determination of NO
(Ref 70) is frequently employed in the presence of high concentrations
of sulfur dioxide. Air is aspirated through a fritted bubbler in a
sampling train containing a nitrogen dioxide absorbing solution. The
absorbed nitrogen dioxide is determined colorimetrically as the azo
dye. Nitrogen dioxide concentration of the order of parts per hundred
million can be determined by this technique. Another method used for
NO. determination is based on the absorption of nitrogen oxides by a
solution of mixed reagent consisting of sulfanilic acid, o£-naphthylamine,
and acetic acid in a glass bubbler (Ref 70- The color produced is
compared to standards or observed spectrophotometrically at a wavelength
of 550 nanometers (nm). ASTM designation E1607, issued in 1958, is a
modification of the above principle, the major changes being the substi-
tution of N-(l, naphthy1)-ethylene diamine dihydrochloride for
«•£• -naphthylene as the coupling agent and the use of a fritted bubbler
instead of an ordinary glass bubbler. Again the resultant color can be
read with a spectrophotometer set at 550 nm.
In the phenol disulphonic (PDS) acid procedure, the gas
sample is fed into an absorbent solution of hydrogen peroxide in dilute
sulfuric acid. The oxides of nitrogen (NO and NO ) are converted to
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182
nitric acid by the absorbent and the resulting nitrate ion reacted with
PDS to produce a complex whose yellow color is read colorimetrically
(Refs 72 and 73)- The PDS procedure is recommended for gaseous mixtures
containing NOx from 5 to several thousand ppm. It is specific only for
the total NOx in the exhaust stream. No definite trend attributable
to contaminants ;n the exhaust stream has been noted for the PDS
procedure (Ref 7*0.
The most commonly used wet chemical analysis method for
nitrogen dioxide and nitric oxide is the Saltzman method (Refs 69 and
75). This method is intended for manual determination of nitrogen
dioxide in the atmosphere in the range of a few parts per billion to
about five parts per million. The sample is obtained by drawing air
through fritted bubblers and nitrogen dioxide is absorbed in Griess-
Saltzman reagent (Ref 65). A stable pink color is produced and may be
read visually or spectrophotometrically at 550 nm. This method is also
applicable to the determination of nitric oxide after it is converted to
an equivalent amount of nitrogen dioxide by passage through a potassium permanganate
bubbler. Ozone and sulfur dioxide are known to interfere with Saltzman
measurements (Refs 69 and 7^); however, their concentrations in aircraft
exhausts are usually not high enough to cause significant difficulty
with the technique.
Another technique that has not seen much application to aircraft
engine,.exhaust analysis is the Griess-Ilosvay (Gl) colormetric method
(Ref 65). A high-pressure mercury vapor lamp is used in the presence
of a butadiene solution to oxidize NO photochemically to NO . The N0_
is absorbed in the Gl reagent and the intensity of color measured. For
simultaneous determination of NO and N0?, the sample stream is divided
into two portions with the NO in one converted to N0» by passage through
an acidified solution of potassium permanganate. Both streams are then analyzed
for N07 content by the previously discussed procedure that employs an
absorbing solution of sulfanilic acid, N-(l-naphthy1)-ethylenediamine
dihydrochloride and acetic acid.
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183
All of these methods are batch type analyses which are slow,
require skilled personnel for performance, and do not yield continuous
data. Some investigations have incorporated these techniques into
continuous analyzers by using a spectrophotometer and appropriate
valving. For example, Ganz and Kuznetsuo (Ref 76) have developed an
automatic recording gas analyzer based on the measurement of the varia-
tion of the pH of a solution with the concentration of the oxides of
nitrogen in the gas stream passing through it. Its operating principle
is that the interaction of nitrous gases with the absorbent (5 per cent
hydrogen peroxide) yields a weak nitric acid solution and the change in
concentration of the acid is dependent on the specific gravity and con-
centration of the gas passing through the solution.
Electro-Chemical Analyzers
Electro-chemical analyzers similar to those used for carbon
monoxide can also be used for determination of NO and NOx concentration
in exhaust emissions. The units range in cost from approximately $2000 to
$3000 with cost dependent on range anduthe SO concentration in the
stream. The principle of operation and the relative advantages and
disadvantages of this instrument .are discussed in the section on carbon
monoxide measurement.
NDIR
NDIR spectrometers similar to those used for CO and C0?
can also be used for determination of nitric oxide in exhaust emissions.
This technique is, in fact, the proqe.dure recommended by the SAE E-31
Committee for NO determination (Ref 36). The procedure is accurate and
reliable j_f_ care is taken to eliminate interference from other species
present in the exhaust, especially water vapor. A combination of optical
filters and drying agents are the most widely used methods of discrimi-
nation. This interference problem is most acute at low concentrations
of nitric oxide.
-------
NDUV
NDUV units have been recommended by the SAE E-31 Committee for
NCL determination in turbine engine exhausts since it is now accepted
that NO and NO. are the prime nitrogen oxide constituents in aircraft
exhausts. The principle of operation of NDUV units is as NDIR units;
only a different portion of the spectrum and a different optical cell
path length are employed.
Gas Chromatographs
Gas chromatographs are well suited for the analysis of the
oxides of nitrogen especially at low concentration levels where they
would make excellent supplemental tools for NOIR and NDUV units.
Their relative advantages and disadvantages are discussed in the
section on carbon monoxide measurement.
Faristors
Faristor is the trade name of a "plug-in sensor" marked
by Environmetrics Inc. These units are low cost ($1750 to $2300)
electronic multigas analyzers that are "liquid-state nonohmic variable
resistors in which a pollutant-selective activating surface ruptures
the gas molecular bonds, releasing energy as a voltage signal proportional
to the pollutant concentration" (Ref 77)« Faristors are sensitive to
NO, N0_, NOx, and S0_ with various modular units available for differ-
ent ranges of each of the species of interest. Avco Lycoming (Ref 39)
is evaluating the applicability of these instruments for aircraft
exhaust measurements. Their sensitivity in this application is as
yet unknown.
Chemiluminescence Monitors
As evidenced above, most of the instruments and procedures
for determing oxides of nitrogen depend on coulometric or colorimetric
techniques. The chemiluminescent procedure depends instead, upon the
formation of electronically excited nitrogen dioxide by the rapid reaction
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185
of nitric oxide with ozone and the subsequent emission of optically
detectable light (Refs 78, 79, and 80). Total oxides of nitrogen are
determined by thermal conversion of the nitrogen dioxide in the sample
to nitric oxide and remeasurement of the total NO.
This procedure has a reported sensitivity from 1 ppb to
1000 ppm and offers the added advantages of continuous monitoring
without interference from other (pollutant) species typically present
in aircraft exhausts. Chemiluminescent units are now available in
both modular and self-contained configurations and require only a small
vacuum pump as auxiliary equipment. Instrument operation is possible
by unskilled personnel; cost per unit is between $5^75 and $10,800,
depending on the range and configuration requirements and on whether
the unit is required to measure NO or NO and NOx.
Application of this instrument to engine exhaust measurement
has shown it highly satisfactory for measurement of nitric oxide (Refs
81 ,and 82). Measurement difficulties have, however, been encountered
for measurement of NOx (Ref ^0) particularly in turbine exhausts where
NOx £ NO. Chemiluminescence units are now undergoing extensive testing
in the EPA's aircraft emissions baseline data collection program; the
results of this program should determine its suitability as a standard
for NO and NOx emissions quantification.
Sulfur Dioxide
Sulfur oxides in aircraft engine exhaust is produced by the
combustion of sulfur impurities in the source fuel. It is generally
accepted that all of the sulfur present in the fuel is converted to
sulfur dioxide during engine operation; hence, it is standard procedure
to calculate, rather than measure, the SO- content of the exhaust stream.
This can be done from a knowledge of the fuel's sulfur content, and of
the fuel-to-air ratio and fuel flow rate for the prescribed engine
operating conditions.
Measurement of SO- in engine exhaust is most frequently
accomplished by batch wet chemical analysis procedures although some
of these techniques have been adapted for use in continuous monitoring
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186
equipment. The S0? content of aircraft exhausts can also be monitored
by Faristors, by electrochemical and conductivity analyzers, and by
remote spectrometers. These techniques are, at most, infrequently
employed and are only mentioned here for completeness.
Wet Chemistry
Katz (Ref 65) reports a large number of wet chemical pro-
cedures for determination of S0?; however only the West-Gaeke (Ref
83) and hydrogen peroxide methods (Ref 69) are widely used.
In the West-Gaeke procedure, the sulfur dioxide is reacted
with sodium tetrachlormercurate to form an intermediate dichloro-
sulfitomercurate ion.. This ion is reacted with acid-bleached p-
rosaniline and formaldehyde to produce a red-purple color that may
be read visually or spectrophotometrically. Nitrogen dioxide is
known to interfere with this determination if the N(L is present at
concentrations greater than that of the sulfur dioxide. Fortunately,
the NO. can be eliminated as an obscurant by addition of sulfamic acid
to the absorbent. The technique is applicable for determination of SO.
in the range 0.005 to 5 ppm and is more sensitive than the hydrogen
peroxide technique discussed below.
In the hydrogen peroxide technique, sulfur dioxide is absorbed
in a solution of hydrogen peroxide which oxidizes it to sulfuric acid.
The solution acidity is then determined by titration with a standard
alkali solution. This method is the preferred procedure if SO. is the
principle acid or basic atmospheric pollutant present in the exhaust
gas stream; it is simpler to conduct than the West-Gaeke procedure and
applicable in a concentration range of about 0.01 to 10 ppm.
Faristors
The discussion of Faristor operating principles in the sec-
tion on NO/NOx measurement is applicable here. The Avco effort (Ref 39)
will be the first known application of these sensors to aircraft exhaust
emissions. Lockheed-California also has Faristors, but their use has
not as yet been reported.
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Electrochemical Analyzers
The discussion of electrochemical operating principles in
the-section on CO measurement is applicable here. There has been no
known attempt to measure the SO. content of aircraft exhausts with such
analyzers.
Conductivi ty
The instruments developed for S0? measurement via conductivity
techniques depend upon the H_0 wet chemical technique. These instru-
ments have been specifically tailored for ambient, rather than source,
emissions monitoring programs. They can, of course, be used in a source
measurement program if the source stream is diluted to reduce the SO.
concentration to detectable limits.
Spectrometry
As discussed by Broderick (Ref 59) remote monitoring of SO
2
by correlation spectrometry is technically possible but economically
infeasible. Further development of the technique will be necessary
before it can be employed in a source emissions analysis program.
Aldehydes
Wilson's paper (Ref 8**) and Stahl's survey (Ref 85) contain
thorough reviews of the procedures for the determination of aldehydes in
air. All methods for aldehyde determination-- either for total aldehydes
or for individual species (e.g., formaldehyde, acrplein)— depend upon
wet chemical analysis. The only procedure for continuous aldehyde
analysis is the Technicon Air Monitor IV-- at a price of $6^00_. This
monitor makes use of the 3-MBTH wet chemical procedure (Ref 86) for
total aliphatic aldehydes measured in equivalent formaldehyde units.
(A modified Schiff procedure using rosaniline and dichlorosulfulomercurate
is also available.)
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Total Aldehydes
A summary of the available methods for total aldehyde
measurement is also given in NREC Report No. 113^ (Ref I) and is not
repeated here. The most extensively used method for determination of
total water-soluble aliphatic aldehydes (measured as formaldehyde) are
the 3-Methyl-2-benzothiazolone Hydrozone Hydrochloride (MBTH) method.
This procedure was developed by Sawicki (Ref 86) and subsequently
refined by Mauser and Cummins (Ref 69). In this procedure, 3'MBTH
is reacted with the sample in the presence of ferric chloride in a
sulfamic acid solution to form a blue cation dye that is measured
spectrophotometrically at 628 m^ The procedure is specific for aldehyde
concentrations as low as 2 ppb. Aromatic amines, heterocyclic imino
compounds, and carbozoles cause-interference with the analysis; however,
since most of these compounds are neither gaseous nor water soluble,
they do not generally interfere in atmospheric or exhaust gas analysis.
The disadvantage of the MBTH procedure is that the reaction
is more sensitive to formaldehyde than other aliphatic aldehydes or
branched-chained and unsaturated aldehydes (Ref 8$). This causes an
unequal response to each aldehyde which has been reported (Ref 51)
to be responsible for inaccurate (low) measurement of total aldehydes
in aircraft turbine exhausts. Further, high ratios of the concentration
of SO- or- olefins to total aldehyde concentration at low (1 ppm)
aldehyde levels may cause errors in the measured results (Ref 8?)•
Two other techniques for carbonyl measurement are given in
Reference 87. Their suitability for turbine exhaust measurements are
also discussed.
Formaldehyde and Acrolein
There are a variety of procedures for measurement of individual
aldehyde concentrations; for example, the ^-hexylresorcinol procedure
exists for acrolein (Ref 69) and the chromotropic acid method is used
for formaldehyde (Ref 69). These procedures are applied because it
is frequently necessary to distinguish between total aldehydes and the
two major aldehyde constituents of aircraft exhaust— formaldehyde
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and acrolein. This is done in efforts to find correlations between
the odor and irritant properties of engine exhaust gases (Ref 88).
In the chromotropic acid method, formaldehyde reacts with the
acid to produce a purple-violet monocationic chromogen whose color
intensity (read spectrophotometrically at 580 m^) is proportional to
the formaldehyde concentration. Fromic acid, dextrose, methanol, phenols,
olefins, and aromatic hydrocarbons and similar compounds that decompose
under the test procedure are also detected; their presence in the
exhaust stream will cause somewhat low measurements. The technique has
a sensitivity range of 0.01 to 200 ppm.
Acrolein is also detected by a spectrophotometric procedure.
As discussed by Katz (Ref 65.)., acrolein reacts with ^-hexyl resorcinol
in the presence of mercuric chloride and trichloroacetic acid to
produce a blue-purple color whose intensity can be read by a spectro-
photometer or colorimeter at 605 m/£. The procedure is quite sensitive
and specific; most organic constituents of the exhaust stream will not
interfere with the determinations. The technique has a reported
sensitivity range from 20 ppb to 10 ppm.
Particulates
The major problem ascribed to measurement of particulate
emissions from aircraft is one of definition. All particulates, large
or small, liquid or solid, emanating from an emissions .source are included
in the Los Angeles County Air Pollution District (Ref 89) definition of
particulate matter. Specifically, they describe particulate matter as
any substance, liquid or solid, except unbound water, that exists in a
finely divided form at ambient conditions. Clearly, this definition
means that vapors of low volatility, for example, hydrocarbons, are
counted in two categories— as both hydrocarbons and particulates.
As a result, most aircraft emissions measurement programs are concerned
with particulate matter on a .dry basis; that is, with the liquid
droplets removed from the sample stream or. with the sampling and collecting
system maintained at a sufficiently elevated temperature to avoid vapor
condensation.
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A good example of the discrepancy in the measured results
according to these two definitions is provided in Bristol's paper
(Ref 52) on aircraft gas turbine engine emissions. Here it is shown
that particulates in the same exhaust stream are as much as 2 to 3 orders
of magnitude higher in concentration if measured by the Los Angeles
"wet" procedure than they are if measured on a dry basis.
Both solid and liquid particulate emissions are of concern to
air pollution control agencies. However, in the opinion of the NREC
staff, no particulate measurement device has been developed which
realistically simulates the condensation of vapors as it occurs in an
aircraft engine exhaust plume. Therefore, the only particulate measure-
ments which have any quantitative significance are those which indicate
concentrations of solid or "dry" particulates.
NREC Report No. 1134 (Ref ]), the study by Broderick (Ref 59) ~,
and the Los Angeles Source Testing Manual (Ref 89) provide thorough
summaries of the instruments and procedures available for particulate
mass, size, and size distribution measurement. As a result, only a
summary of the more common types of particle detectors now available
is presented here.
Collection devices that are most commonly used in monitoring
aircraft particulate emissions are based on filtration and impingement
(wet or dry) techniques.
Filters remove particles from a gas stream by direct inter-
ception, by inertial collection, by diffusional deposition, by electrical
attraction, and by gravitational attraction. In a given instrument
one or more of these mechanisms may be employed; details-of these
principles are given in Ref '90. Filtration schemes are generally applicable
for particles in the 0.1 to 10 micron (diameter) range; in most cases,
the analysis is completed by direct weighing of the filtrate and filter
medium. Types of filters and filter holders are discussed in Reference 90;
typical cost of the widely used "Hi-.Vol" sampler which is based on the
direct filtration principle is about $200 to $300.
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Impactors or impingers are generally built as cascades to
simultaneously collect and classify particles by both mass and size.
Impactors are less frequently used in aircraft particulate emissions
measurement programs than direct filtration devices; their predominant
application has been with aerosols and dust laden process streams.
Impactors cost from $750 to $2000 with cost dependent upon the stage
requirements and upon the necessity (or lack of necessity) for main-
taining the sample stream at an elevated temperature.
Mass monitors are devices that allow real-time measurements
of particulate concentration over a size range from 0.01 to 15 microns
and at concentrations up to 100,000 ^^.gms/m . These instruments
operate by drawing the sample gas through a chamber where the particles
take on an electrostatic charge. The stream then passes over a
vibrating piezoelectric sensor where an electric field forces the
particles into contact with the sensor. The resonant frequency of the
sensor is thus reduced in direct proportion to the mass of the adhering
particles; this output signal can be monitored with standard digital
counting equipment (Refs 91 and 92). Cost of a mass monitor is
$1800 to $2000, a complete system including a monitor, indicator/printer,
auxiliary vacuum pump, and cabinet, costs $4000. One report of the use
of particle mass monitors in an automotive emissions program showed
a deviation of +30 per cent from deposits collected via filtration equip-
ment; this may be due to the presence of organic particles with the
lead particles or to temperature and humidity fluctuations in the diluted
exhaust streams (Ref 93). Clearly, further development work is still
necessary on this type instrument.
Other existing detection devices for particulate monitoring
that do not depend upon optical scattering techniques include electrical
mobility analyzers and beta gauge systems. Electrical mobility analyzers
are used with particles 0.005 to 1.0 microns in diameter and are based
on the attraction of charged particles to a metal surface of opposing
charge (Ref -59). Beta gauge systems use a paper tape sampler to collect
particulate matter on a filter; the tape is then placed between a beta
source and a radiation detector. The attenuation of the. source energy
is proportional to the particle concentration (Ref 93). Both of these
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instruments are in the prototype stage; the beta guage system has been
successfully employed in an automotive emissions program (Ref 93).
Microwave laser radar and microwave spectrometers are both
available for measurement of particle size and density in exhaust
streams (Ref 9^). Units based on electrostatic precipitation are also
available (Ref 9*t).
An interesting optical device for particle monitoring is the
0.1 to 10 micron (diameter) range is the integrating "nephelometer"
described by Charlson (Ref 95). This device measures the scattering
coefficient of light caused by particulate matter in the sample stream
and automatically relates the measurement to particle concentration and
to visibility. The instrument is so designed that nearly the total
solid angle from full forward to direct back-scattering is observed.
A serious deficiency in the instrument is the needed assumption of a
constant particle size distribution and composition in its calibration
(Ref 96). The instrument and sampling line can be maintained at a
sufficiently elevated temperature to avoid condensation of the less
volatile matter in the sample stream. A nephelometer has recently been
tested with aircraft engines at the Naval Air Propulsion Test Center,
but the results of the test are unknown (Ref 97)* Unit cost is about
$5300.
Most other light scattering or video scan devices have been
developed primarily for measurement of the size distribution of a sample,
rather than for determination of total particulate concentration. These
devices are expensive ($^000 for a sensor to $35,000 for complete systems),
have a limited dynamic range (e.g., 30), and have an unsatisfactory lower
sensitivity limit of about 0.1 microns.
Condensation nuclei counters are used for determination of
the concentration of particulate matter in the 0.001 to 1 micron
(diameter) size range. Particles of this size are important from an
emissions standpoint since they act as nuclei for the photochemical
smog reactions. Further, particulates in this size range are respirable
and thus potential health hazards. It appears that, the majority of the
particulate emissions from aircraft engines fall into this category
(Ref 58) and are clearly not measured by convention filtration or
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impingement techniques. The basis of operation of condensation nuclei
counters is the ability of condensation nuclei to act as centers for
the condensation of water in a supersaturated environment. Through the
condensation of the water on the nuclei, droplets are formed of visible
size. Standard optical techniques are then applied for their detection
and measurement (Ref 98). Condensation nuclei counters cost in the
vicinity of $6500,with compact portable units available at about $4500.
Most currently avaiVable condensation nuclei monitors operate
in a range from 0.001 to 0.1 microns with a 20 per cent accuracy. The
Department of Transportation Systems Research Center in Cambridge, Mass.
is therefore developing a portable counter to fulfill the need for an
instrument operating in the range from 0.001 to 1 micron (Ref .59% The
design goals for this instrument include the ability to accept sample
streams with concentrations from 10 to 10 particles/cc at input ambient
pressures from 0.05 to 1.0 atm with intake temperatures from -60-deg C
to 200 deg C and with a measured accuracy of 10 per cent across a spectrum
of 10 size ranges. Reference 59 contains further reference details on
the need for condensation nuclei monitors for aircraft particulate
emissions monitoring.
Smoke
Three general techniques are applicable for smoke measurement.
These are:
1. Subjective analysis where visual comparison of plume
darkness is made with a graded chart.
2. Light extinction where a light meter measures the
attenuation of a light source shone directly through a
sample of the exhaust plume.
3. Indirect reflectance where the amount of light reflected by
filter paper through which a fixed volume of the sample
stream has passed is measured.
In all cases, a smoke number is calculated or assigned which relates the
darkness of the plume to the amount of light absorbed and scattered by
the smoke. NREC Report No. 1134 (Ref 1) and the reports of Shaffernocker
(Ref:99) and Toone (Ref.100) contain detailed discussion of these techniouo;
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The first priority of the SAE E-31 Committee was to
develop a method and device for monitoring smoke emissions from
aircraft. The committee agreed that, "... a stained filter technique
was the most satisfactory even though it missed the desire for a mea-
surement system thai was directly convertible into degree of visible
obscuration (Ref 101)." This decision led to the SAE ARP-1179<(Ref 55)
which specifies test, sampling (e.g., probe orientation), and analysis
techniques to be followed to insure conformity of smoke measurement in
the aircraft industry. At the present time, the committee is considering
modifications to the sampling procedures established in the ARP in light
of information made available since its release.
Several instruments have been constructed which conform to
the specifications of ARP 1179- One unit has a sale price of $3200
without a sample line or a reflectometer; it is not, however, generally
ava!1 able.
As recognized by the E-31 Committee at its inception, the
stained filter technique does not lead directly into a measure of visi-
bility extinction. However, correlations have been developed which relate
the smoke meter reading to the mass concentration of dry particulates (Ref 102)
and the opacity of the engine exhaust jet (Ref .103).
Odor
NREC's discussion of the origin and measurement of odor in
aircraft engine exhausts (Ref l.).is still an adequate and appropriate
summary of this emissions problem. The report by Sullivan (Ref 10^)
the Public Health Service and the papers by Dravnieks (Ref 56) and
Fish (Ref 105) are more recent surveys of the general topic of odorous
emissions; Sullivan's study does contain a brief section devoted to
ai rcraft odors.
Perhaps the most relevant statement about odor is made by
Fish (Ref 105) when he states "... with few exceptions, we do not
yet know how to apply meaningful weighting factors to obtain a useful
subjective measurement of odor based on qualitative and quantitative
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measures of gas concentration." Studies by Dravnieks (Ref 106) and Arthur D.
Little, Inc. (Ref 107) confirm this contention by identifying the composition
of odorous compounds in diesel engine exhaust (by, for example, gas chroma-
to graphic separations) but by failing to develop adequate correlations of
these concentrations with a suitable sensory scale. Reference 108 contains
a review'of federally sponsored research on diesel engine exhaust odors.
Not even this latter type of analysis has been undertaken for
gas turbine exhausts. Lozano et al (Ref 50) do, however, report odor
dilution thresholds for turbine engines as a function of operating mode
(power level) and engine type.
As stated in an earlier section, the SAE E-31 Committee is
planning to address itself to this emissions problem in the near future.
Instruments Under Development
The principle of operation of the NO-NOx (and 0 ) chemi-
luminescence monitor involves measurement of the light.energy emitted as the
specimen of interest is reacted with another gaseous specie. This
principle is by no means restricted to the determination of oxides of
nitrogen and ozone; systems based on the principle have already been
marketed for determination of sulfur dioxide and hydrogen sulfide
(Ref 102). EPA is also developing similar methods for measurement
of formaldehyde, aromatic hydrocarbons, chlorine, fluorine, hydrogen
chloride,-arid some metals (Ref 109).
A device based on ultraviolet absorption has .been designed
to monitor unburned hydrocarbons in auto exhaust (Ref .110). In the sample
chamber the exhaust gas is exposed to UV radiation. A sensor tuned to
a wavelength band between 1850 and 2250 Angstroms then measures the
degree of absorption of the radiation by the sample. Since olefins
and aromatic hydrocarbons are excellent absorbers in this band (but
oxygen, water, and other common gases are not), the instrument is
particularly well-suited for determination of reactive hydrocarbons.
A device for separating reactive and unreactive hydrocarbon'
in engine exhaust has al.so been developed by Groth and Zaccardi at
Pratt £• Whitney (Ref.111). This unit is subtractive in nature; that is,
chemical absorbents are used in series with a heated FID to remove
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the reactive hydrocarbons from the sample. In this way, the concen-
tration of the reactive species that participate in the photochemical
smog reactions can be determ.ined.
McClatchie (Ref 62) reports that a single path fluorescent
NDIR unit similar to that constructed for monitoring CO is under development
for NO measurement. The unit promises to have greater sensitivity in
the lower concentration ranges than conventional NDIR instruments and
will be free of interference from water vapor and other obscurants.
Broderick (Ref 59) discusses the'newly-developed technique of
applying remote Raman spectroscopy to trace gas analysis. Until
development of the laser,the procedure was primarily a laboratory curio-
-sity due to the requirement of lengthy exposure times with high-power
mercury arc lamps (Ref. 112). This analysis technique depends on light
scattering; light absorbed by a molecule is re-emitted at a shifted
frequency. This and the incident frequency relate to specific character-
excitation frequencies of the scattering molecule. If the energy of the
Raman photons for a particular molecule is known, measurement of the
scattering relates to the concentration of that specie in the sample stream.
Champagne (Refs kQ and 113) reports a contract between the Aero Propulsion
Laboratory and Avco Everett for the development of an engineering proto-
type of a field unit that could be used at either an aircraft test cell
or at a flight line location. The two year program will examine the
technological feasibility of monitoring CO, C02, NO and NOx, and total
organics (C-H stretch band) as they are emitted in aircraft exhausts.
The first phase of this program is now underway and will determine the
. appropriate molecular energy bands and potential obscurations (e.g., CO by CO
or CO by CO) at the elevated, temperatures (1200 to 1800 deg.F) of interest.
Hinkley and Kelley discuss (Ref. 11A) the development of
tunable semi-conductor diode lasers which show promise in the creation
of extremely sensitive and accurate NDIR instruments. As discussed by
Broderick (Ref 59) such diodes could be "tuned" to specific wavelengths
to permit monitoring of such species as the individual components of the total
hydrocarbon emission. An instrument specific to NO and which depends on
tunable infrared radiation from a Raman spin-flip laser has been reported
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to detect NO contentrations in air samples at concentrations as low as
0.01 ppm (Ref 115).
LIDAR or Light Detection and Ranging systems have been proposed
as atmospheric probes to measure and detect particulate concentrations in
the atmosphere. These instruments depend on lasers as power sources and
on back scattering measurements to determine particle size distribution
and number density. LIDAR is a tool for remote monitoring programs;
one drawback to its use is the necessity to make a priori assumptions
pertaining to particle size distribution and.index of refraction for
the purpose of instrument calibration. Reference •)16 contains a review
of the technique and of its potential application as a pollution
monitoring tool.
Dix et al (Ref 11?) discuss the use of a mass spectrometer as
a probe for studying the chemical kinetics of the formation of oxides of
nitrogen in a simulated gas turbine combustor. The' probe is suitable
-3 -4
for* measurement of mole fractions in the 10 to 10 range, but
requires further engineering development before use as a mobile monitor
for engine emissions.
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