-------
1=5
O
      O
      CM




      §
      H
      H
      C/3
      w
      H
      M
      H


      O
      O
      w
      Pi
      p
      O
      33
       I
      00
      CO
      s
      o
      I—I
      H
      H
      !3
      W
      O
      u
      O
      u
      H
      O
      w
      w
 ft
 ft

en

 II

T3
 \-4
 CO
T3

 ca
 4J
CO


Cf
c
0)
•H
,0
                                                                                                               O
                                                                                                               ro
                                                O
                                                m
                                                                                                               O
                                                                                                               cr\
                                                      0)

                                                      01
                                                      JJ
                                                      c
                                                      n)
                                                                                                                     •H
                                                                                                                      60
                                                      60
                                                      c
                                                      •H
                                                      -d
                                                                                                                     4-1
                                                                                                                      o
                                                      4J
                                                      •H
                                                      rH
                                                      •H

                                                      43
                                                      Cfl
                                                      J3
                                                      O
                                                      V-i

                                                      PM
                                            o
                                                                     00
                                             (uidd)  ROIIVHINaDNOD  00
                                                          35

-------
same levels of carbon monoxide whether it be influenced by
pollution from other than the airport (easterly winds)  or
from the airport alone (westerly winds).   Figure 2 shows
that the 8-hour CO standard, which is not to be exceeded
more than once per year,  is estimated to have been exceeded
at site 209 13 times per month, or 39 times in the winter 3-
month period.

Part of the carbon monoxide concentrations shown in Figure 2
is due to aircraft.  To estimate the portion of the
concentration that is due to aircraft, dispersion modeling
was applied.  The dispersion modeling methodology is
discussed in Appendix B-   The model's resulting estimate of
the current contribution by aircraft to total CO
concentrations, shown in Figure 3, indicates that aircraft
are highly significant contributors to local CO
concentrations downwind of the airport.   Figure 3 indicates
that expected aircraft contributions constitute 60-70% of
the total CO concentrations in the area of site 209.

Between 1970 and 1980, CO emissions from aircraft are
estimated to increase by fifteen percent. (Table U) while CO
emissions from all other sources in the Los Angeles area are
expected to decrease to 20X of their 1970 levels.12  Using
the estimated changes in emissions from these two source
categories, and assuming that the emission changes yield
proportional changes in pollutant concentrations due to each
source category, CO concentration freguency distributions
for various aircraft contributions can be derived from
Figure 2.  The result is presented in Figure 4 for various
1970 aircraft contributions to pollutant concentrations.

Figure 1 indicates that without controls of CO emissions
from aircraft the 8-hour CO standard will be exceeded more
than once during the 1980 winter months at site 209 if the
aircraft contribution to the total CO concentration in 1970
is as little as 20%.  As shown in Figure 3, the 1970
contribution by aircraft exceeds this percentage over a
large area downwind of the airport.  If the reasonable
assumption is made that Figure 2 approximates the 1970
winter CO concentration frequency distribution in this area,
it is evident that in 1980 the 8-hour CO concentrations will
continue to exceed the standard in this same area downwind
of the Los Angeles Airport if aircraft CO emissions are not
controlled.

As noted in Appendix A, the analysis resulting in Figures 2
and U can be repeated using data from September, rather than
from August, as a basis.   The September data will yield
higher concentrations than will the August data for similar
                             36

-------


£—fcv^lk
! >..-..-^. •• .-'A VV, •, .«.
\ (-'I-/!' )  L ' !] i

i><,^  ! ':-'-.t
    ,
.-•'. i w w a)
.- - ; S iJ c T3
''
                            ^V.^%1' ,^4^j !te^'''i'.:"r
                            nri ••!=-! rnr>' • Si:5^^;



                      niP^^"
                                A

                  37

-------
                                                                               0)

                                                                               0)
                                                                               o
                                                                               ex

                                                                               0)

                                                                               •H
                                                                               ao

                                                                               
-------
frequencies of occurrence.  Consequently, the results from
the September data analysis can be used to indicate an upper
value of a range of frequencies at which the 8-hour CO
standard is exceeded; the results from the August data can
be used to indicate a lower value of the range.  The ranges
for 1970, and for 1980 with various aircraft contributions,
is presented in Table 16.

1-Hour CO Concentrations at the Los Angeles Airport.  The 1-
hour CO air quality standard of 35 ppm (40 ug/m3) was
exceeded at only one of the outdoor continuous sampling
locations at the Los Angeles Airport.  A summary of the 1-
hour sampling data at these receptors is presented in Table
17, which indicates that only at site 205 was the 1-hour CO
standard frequently exceeded.  Site 205 was located next to
heavy automobile traffic en World Way Boulevard at an
automobile passenger unloading area.  The 1-hour CO standard
was exceeded 12 times during the approximately 4-week period
of sampler operation.  Expected reductions in CO emissions
from automobiles probably would reduce concentrations at
sites such as 205 to levels balow the 1-hour standard.
Generally the 8-hour CO standard of 10 ug/m3 is the most
difficult of the two standards to reach,  and statistically
if the 8-hour standard is met, the 1-hour CO standard will
also be met.*'

Carbon Monoxide Concentrations at Other Airports.
Dispersion modeling was used to provide estimates of 1-hour
CO concetnrations both from aircraft alone and from all
airport and adjacent sources within 10 kilometers of the
center of each airport.  This modeling was done for Los*
Angeles, J. F. Kennedy, Chicago-O'Hare, and Washington
National Airports.  The results, presented in Table 18, are
predicted concentrations at airport area points where: (1)
the general public could have access for 1-hour periods,  and
(2) the total concentrations, as estimated by dispersion
modeling, exceed the standards.

Although minimal reliance should be placed on the precise
numerical values predicted by the model,  these values are of
the same order of magnitude as the values from actual
measurements presented in Table 17.  These results indicate
that localized carbon monoxide effects are not limited to
Los Angeles Airport.

The potential of high 8-hour CO concentrations downwind of
other airports, with large aircraft contributions, exists
near airports besides Los Angeles Airport.  As previously
discussed. Table 14 indicates the potential of such
concentrations at six additional airports.
                                39
-------
                               TABLE 16

    EXPECTED RANGE OF DAYS THAT 8-HR STANDARD WILL BE EXCEEDED IN
             VICINITY OF L.A.  AIRPORT,  1970 and 1980a
Based on
August
Datab
Based on
September
Data
   Days Standard Exceeded
          in 1970

   Days Standard Exceeded
   in 1980, With Following %
   Contributions by Aircraft
   (at 1970 emission levels)
   to Total CO Concentrations

           80%

           60%

           40%

           20%

            0%
39
36

22

 9

 1

 0
to
65
to        61

to        49

to        32

to        14

to         1
 aBecause the highest CO concentrations occur during winter months,
it is assumed that the frequency of exceeding the standard during the
winter quarter gives the frequency of exceeding the standard the
entire year.
   From Figures 2 and 4.
                                 40
-------
                                TABLE 17

                          LOS ANGELES AIRPORT

           NUMBER OF TIMES THE 1-HOUR CO STANDARD WAS EXCEEDED
       MAY 10 THROUGH NOVEMBER 9,  1970, CONTINUOUS SAMPLING SITES
Site*
201
203
204
205
208
209
Downtown LA
Total Hours
of Sampling
3710
4256
4258
637
4326
4279
4965
Number of Hourly
Values When
Standard Exceeded
0
2
0
12
1
0
3
Highest Two
Hourly Values
27, 26
46, 40
23, 19
51, 49
37, 28
31, 27
37, 35
*Refer to Figure 1 for Location,
                                     41
-------
                              Table  18

                Dispersion Model Estimates  of 1-Hour
                    Carbon Monoxide Concentrations
Site Location*
JFK (T)
JFK (T)
JFK (T)
LAX (P)
LAX (P)
ORD (T)
ORD (S)
DC A (P)
DC A (P)
CO Concentration, mg/m-^
Aircraft Sources Only Total
85
4
3
55
32
21
9
110
45
100
45
44
62
45
41
41
120
59
*DCA = Washington National Airport, LAX = Los Angeles International
 Airport, JFK = John F. Kennedy International Airport, and ORD =
 O'Hare Airport, Chicago

(T) = Terminal area

(P) = Peripheral area--away from terminals,  but within airport
      boundary

(S) = Outside of airport boundary, in airport surroundings
                               42
-------
Hydrocarbon and Potential Oxidant Concentrations.  Isopleths
of 1970 hydrocarbon concentrations due to aircraft alone at
the Los Angeles Airport are presented in Figure 5.  These
isopleths are based on the dispersion modeling methodology
presented in Appendix B, and are a result of meteorological
conditions that are particularly conducive to high
hydrocarbon concentrations.  Such conditions would be
expected to occur at least once per year.

The results indicate that there are large areas surrounding
the airport where the hydrocarbon concentrations due to
aircraft are well in excess of the standard.

Between 1970 and 1980, Table 4 indicates that at the Los
Angeles Airport, hydrocarbon emissions from aircraft will
decline to about HQ% of their 1970 values.  These reductions
are reflected in Figure 6 which presents isopleths of 1980
hydrocarbon concentrations due to aircraft alone, at Los
Angeles Airport, based on meteorological conditions
equivalent to those used for the isopleths in Figure 5.
Even with the reduction in aircraft hydrocarbon emissions,
it is likely that in 1980 the hydrocarbon standard will
continue to be exceeded over a large area due to aircraft
emissions alone.

As indicated earlier, hydrocarbon concentrations at levels
typically found in the atmosphere are not harmful to health.
However, if airport hydrocarbon concentrations were followed
downwind for several hours under conditions conducive to the
accumulation of high oxidant concentrations,7 aircraft-
generated hydrocarbons could be expected to be large
contributors to downwind oxidant concentrations over the Los
Angeles area.

A modeling analysis was performed to estimate hydrocarbon
concentrations downwind of Los Angeles Airport in 1980.  The
meteorological conditions used were similar to those used
for Figures 5 and 6.  The methodology of this analysis is
presented in Appendix C, and results are presented in Figure
7.  The three curves in Figure 7 show nonmethane hydrocarbon
concentrations downwind of Los Angeles Airport resulting
from the surroundings plus total airport emissions, total
airport emissions alone, and aircraft emissions alone.   The
initial concentration at the western airport boundary (0 km
in Figure 7)  is shown to be zero, which is a result of the
proximity of the western boundary to the ocean, wind
direction from the west, and the assumption of negligible
hydrocarbon concentrations in wind coming off at the ocean.
At a point 3 hours downwind (16 km from the eastern airport
boundary)  the overall hydrocarbon concentration will have
                               43
-------


                                                            <_>
                                                            OL
                                                            O

                                                            CO
                                                            <
                                                            DC.
                                                            o
                                                            o:
                                                             <
                                                             z
                                                             o
                                                             <
                                                             z
                                                             CC
                                                        E   -I
                                                             o

                                                             >-
                                                         (U

                                                        -D
                                                                  <

                                                                  CTi
                                                                  O
                                                                  r^
                                                                  
-------
                          I "i 1 M"i"yv "••   'i"  ;.:':''„''.'••"'-'•- ••"•>• ;
                          •  i : I  ! Lx\X -i  •>• .'••>• '—•.—•>.,
^"fimK\.&

                                                                                     ..'-!. ; I .l,!,i.}J'~!./S '•'••:•




                                                                                 ^Zai* .;.-"-:'^~J' ^'pg-^'^c'o "i1^;
                            /   j.:.,.  •L--v;v^l:)f';
                            V    .SvtiJ-=';.^^i::

                                                                                                                H-   <
                                                                                                                    o
                                                                                                                    CO
                                                                                                                    
-------
















r^

pa
Pi

O
is
0
h™4
H
2
H
W
U

0
u

la
o
w
Pi
<
u
o
Pi
p
IX
PC


o
00
i— i
Pi
o
PH

H
Pi
0
PH
Pi
i— i
<

to
PJ
i_3
Pa
O



Q
Fd
hJ
0

£_)
^
O
U

CO
pa
u
Pi
£3
o
U~)

H
0)
03
03
C
O
•H
4-J
•H
-o
C
O
U

1— 1
CO
O
•1-1
M
O
.— i
O
O
-------
been in excess of the standard for 3 hours, enough time for
possible formation of oxidant in concentrations exceeding
the standard.

It is important to emphasize that this analysis was
performed for 1980.  If it were repeated for 1970, the
concentrations for each of the curves would be at least
double the 1980 values.

The emissions densities presented in Table 15 indicate that
among the four airports studied, emission densities from
aircraft alone are highest at Los Angeles Airport.  However,
the range among these emission density values is still less
than a factor of 2.3 in 1980, indicating that conclusions
concerning future aircraft-generated hydrocarbon and oxidant
concentrations at the Los Angeles Airport and vicinity apply
generally to the other airports studied, and that additional
reductions in aircraft-generated hydrocarbon concentrations
are necessary.

Oxides of Nitrogen.  Although the ambient air quality
standard is for NO2  (100 ug/m3, annual concentration), the
result of the dispersion modeling is presented as oxides of
nitrogen (NOx).  This is done because there exists no well-
defined relationship for the conversion of NO to NO2.   In
the presence of hydrocarbons; the NO to NO2 conversion is
accelerated; best estimates indicate that 90 percent of the
NO is converted to NO2 within a 2-hour period in the
presence of sunlight.  The reaction is essentially
negligible at night.  Considering all NOx as NO2 could
result in an overestimation of annual average
concentrations.

Oxides of nitrogen concentrations due to aircraft alone are
presented in Figure 8 for Los Angeles Airport area for 1970.
These modeling approximations indicate that LAX is
responsible for NOx impact over a large area surrounding the
airport.  With growth of overall aircraft activity, and the
changeover to bigger and higher pressure ratio turbine
engines, aircraft emissions of NOx will increase greatly
between 1970 and 1980.  Present and expected future NOx
emissions from aircraft at the four major airports studied
are given in Table 15, which indicates that between 1970 and
1980 aircraft emissions of NOx will increase by factors of
2.2 at O'Hare Airport, 1. «* at Washington National Airport,
1.5 at Los Angeles International Airport, and 2.9 at John F.
Kennedy Airport.

The general affect of increased NOx emissions from aircraft
at LAX is reflected in Figure 9, which presents isopleths of
                                 47
-------
                        A
                                            g
                                        .y
48
-------
1980 NOx concentrations due to aircraft.  Figure 9 indicates
that NOx concentrations due to aircraft alone could be
widespread in residential areas around LAX, and that in some
areas, the NO2 concentrations due to aircraft are comparable
to the standard.  It should be emphasized that these NOx
concentrations are due to aircraft alone, and NOx emissions
from other sources would be expected to significantly
increase the concentrations plotted in Figures 8 and 9.

NOx concentrations of similar magnitude to those in Figures
8 and 9 can be expected in the vicinity of other airports.
For example, isopleths showing expected 1980 NOx emissions
densities due to aircraft alone for O'Hare Airport are
presented in Figure 10.  Without emission controls, aircraft
using O'Hare Airport can be expected to be large future
contributors to localized NOx concentrations, as was the
case for Los Angeles Airport.

Smoke and Particulates.  Smoke generated by aircraft causes
significant reductions in visibility and is a cause of
widespread complaint by affected citizens.

The 1-year air guality monitoring program conducted at Los
Angeles International Airport indicated increased soiling
effects in the airport vicinity due to aircraft activity.
Atmospheric measurements of particulates using a tape
sampler technigue gave higher readings (indicative of
soiling)  for the airport area than for locations several
miles removed, such as downtown Los Angeles.  Additionally,
sampling at sites surrounding and adjacent to the Los
Angeles Airport area showed increasing soiling values from
upwind of the airport to a maximum immediately downwind of
the airport.

Measurement of total weight of particulate material, based
on Hi-Vol sampling, showed little variation between airport
and downtown areas.

Results of the dispersion modeling analysis for all four
airports indicated that particulate concentrations due to
aircraft in some parts of the airports could exceed the
secondary particulate air guality standards.
-------
uiiC/^^"''^"'^'^ "I	;:; i; ):'"rr" >K~' ^]i]
:^..^^\V\.m   •     t   rr- i  v-'  • -;  '-
•^—l—Til '-  (-~":^—)•*'•"•'•^''i'°:'^/'.' 'bl !'"'• - ' !l -•'• •'•• ~j-——-f-'-—
                                                                E —
                                                                ^
                                                                CD CO
                                                                <1J CO
                                                                -D O
                                                                E

                                                                c
                                                                   CO
                                                                  o
                                       50
-------
             . HARE
            CHICAGO
           TERNATIO
            AIRPOR
                 FIGURE 10     (numbers inL(.g/m )

NO.. ISOPLETHS IN THE VICINITY OF CHICAGO-0'HARE INTERNATIONAL:

                            Annual Average for 1980
AIRCRAFT SOURCES
-------
 TECHNOLOGICAL  FEASIBILITY OF CONTROLLING

                AIRCRAFT EMISSIONS
    Information on emission control methods is necessary to
determine the levels to which aircraft emissions can
feasibly be reduced. An  earlier Federal study,1 **
identified potential control approaches including
modification of aircraft  engines, fuels, and ground
operational procedures.   This study indicated that
modification of aircraft  engines and ground operational
procedures appear to be the most feasible and effective
control procedures.   More recently, the Aerospace Industries
Association (AIA)  has issued a report*s summarizing  results
of investigations conducted by industry on: (1)  emission
characteristics of aircraft gas turbine engines; and (2)
potential methods for reducing aircraft turbine engine
emissions.  The AIA report also identifies the possibility
of reducing emissions through modifications of engines
(especially combustor design) and of ground operational
procedures.

    The current reassessment of control methods must
consider each of the aforementioned approaches.   In
assessing the feasibility of a control method, four  factors
must be explored:  (1) effect of the method on the
functioning or capacity of the aircraft system;  (2)
effectiveness of the method in reducing emissions; (3) cost
of utilizing the method;  and (4)  time reguired for
implementing the method.  Information on emission-
measurement instrumentation is also necessary to ensure  that
aircraft emissions can be measured with the accuracy and
sensitivity required for  enforcing the desired standards.

    The Environmental Protection Agency has conducted
several studies (references 16-27)  to obtain information for
assessment of aircraft emission control methods.  This
report summarizes the information obtained in these
investigations.  The specific objectives of this analysis of
aircraft emission control technology are:

       (1)  To identify methods of controlling aircraft
emissions through modification of engines, fuels,  and ground
operations.
                                  53
-------
       (2)  To estimate their effectiveness in reducing
aircraft emissions.

       (3)  To estimate the time required for and cost of
implementation.

       (H)  To assess the technology of measuring emissions
from aircraft engines and to identify areas requiring
advancements in instrumentation or test procedures.

    Emission control by fuel modifications was reassessed to
evaluate developments in aircraft fuel technology.  This
investigation was discontinued after preliminary analysis
indicated that no significant reductions in emissions could
be achieved by modifying fuels, except for reductions in
sulfur or lead content that result in proportionate
reductions of SO  and lead emissions.

    A list of specific emission control methods involving
engine modifications was formulated on the basis of
preliminary analyses, which indicated that each method was
feasible and offered a significant reduction in one or more
emission classes.  Feasibility was assessed on the basis of
the following factors:

       (1)  No reduction in engine reliability (safety).

       (2)  Little or no reduction in engine performance
(power-weight ratio).

       (3)  Reasonable cost of implementation.

    The preliminary list of control methods was then
subjected to more detailed analysis of control effectiveness
and implementation costs,  control methods involving changes
in ground operations were evaluated in a similar manner.

    Evaluation of the emission control methods involving
engine modifications gave primary consideration to the
following emission classes: carbon monoxide  (CO), nitrogen
oxides (NOx), total hydrocarbons (including drained fuel)
(THC), dry particulates  (DP) , and smoke.

 EMISSION CONTROL BY ENGINE MODIFICATION

Engine Classification

    To facilitate analyses of engine modifications, aircraft
engines are categorized according to their thrust or power
level.  The classification system is indicated in Table 19.
                                   54
-------
                         TABLE 19

            AIRCRAFT ENGINE CLASSIFICATION
Engine class
Engine Type
   Power Range,
 Ib thrust or eshp
     Tl

     T2

     T3

     PI
  Turbine

  Turbine

  Turbine

  Piston
  Less than 6,000

  6,000 to 29,000

Greater than 29,000

 All piston engines
                              55
-------
    Although this classification system is based simply upon
power level it effectively groups engines of similar
emission potential (when the emission rates are normalized
according to an appropriate engine-size parameter) .  Also,
since effectiveness factors and costs of the control methods
are similar for engine models within each class, the system
is particularly useful for this analysis.

    Three classes of turbine engines are defined, and all
piston engines are included in a single class.  This system
thus categorizes engines according to their principal
applications and according to certain design characteristics
that affect emission rates.

    The small turbine engine class (Tl) includes most of the
turboshaft and small turbojet and turbofan engines used in
business and small commercial aircraft.  It also includes
auxiliary power units (APU) used on large commercial
aircraft.  These engines are considered as one class because
the relatively small size of the combustor components (or
large surface-volume ratio) makes control of certain
emissions more difficult than with larger engines.

    The next turbine engine class (T2) includes most of the
turbojet and turbofan engines used in medium-to-large
commercial aircraft.  The design characteristics of most of
these engines are basically similar.

    The third turbine engine class (T3) includes large
turbofan engines for "jumbo" transport aircraft and the SST
engines currently in use or under development.

Emission Control Methods and Effectiveness

    Technology for controlling emissions from aircraft
engines by means of engine modifications has been analyzed.
The purpose of this analysis was to identify specific
methods of reducing pollutant emissions from aircraft
engines and to indicate the reductions in rates of emission
attainable by these methods.  Various engine modifications
appear to be feasible in that they can be applied to
aircraft without degrading engine reliability or seriously
reducing aircraft performance.  Costs of implementing these
control methods also appear to be within reasonable limits,
at least in preliminary analysis.

Turbine Engines - The engine modification control methods
considered feasible for turbine engines are listed and
described briefly in Table 20.  Six methods are, at least in
                                   56
-------
  Table 20.   ENGINE MODIFICATIONS FOR EMISSION  CONTROL  FOR  EXISTING AND  FUTURE

                                  TURBINE ENGINES
       Control  method
                    Modification
Existing engines
  tl - Minor combustion
       chamber redesign


  t2 - Major combustion
       chamber redesign


  t3 - Fuel drainage control


  t4 - Divided fuel supply
       system


  t5 - Water injection
  t6 - Modify compressor air
       bleed rate
Future engines
  t7 - Variable-geometry
       combustion chamber

  t8 - Staged injection
       combustor
Minor modification of combustion chamber and fuel
nozzle to achieve best state-of-art emission
performance.

Major modification of combustion chamber and fuel
nozzle incorporating advanced fuel  injection concepts
(carburetion or prevaporization).

Modify fuel supply system or fuel  drainage system to
eliminate release of drained fuel  to environment.

Provide independent fuel supplies  to subsets of fuel
nozzles to allow shutdown of one or more subsets dur-
ing low-power operation.

Install water injection system for short duration use
during maximum power (takeoff and  climb-out) opera-
tion.

Increase air bleed rate from compressor at low-power
operation to increase combustor fuel-air ratio.
Use of variable airflow distribution to provide inde-
pendent control of combustion zone fuel-air ratio.

Use of advanced combustor design concept involving a
series of combustion zones with independently con-
trolled fuel injection in each zone.
                                          57
-------
principle, applicable to existing engines by retrofitting of
new or modified parts, and to engines currently in
production.  Two methods are considered to be applicable
only to future engines of new design, since the
modifications required are too extensive to be applied to
engines for which development has been completed.

    The first control method consists of simple
modifications of the combustor and fuel nozzles to reduce
all emission rates to the best levels currently attainable
within each engine class.  The degree of control attainable
depends upon the performance of specific engines compared
with those engines in the same class demonstrating the
lowest emission rates.  In general, this control method
requires emission quality control (emission reduction to
levels demonstrated by other engines of that model).
Additionally, for certain high-emission engine models, it
means emission reduction to the level of other engines of
the same class.  Each of the other control methods is more
specifically directed at one or two pollutant classes.

    Reductions in emissions achievable through the use of a
control method vary with the pollutant considered, the
engine class, and the engine operating mode.  Estimates of
the effectiveness of each control method have been made for
all combinations of these factors and are presented in
Tables 21 and 22.  The estimation of emission control
effectiveness for turbine engines is based upon reductions
attainable from "lowest current emission rates."  These
rates are defined as those attainable through control method
tl (table 19), minor combustion chamber redesign.

    It is predicted that all engines in each class could be
modified to achieve these "best rates." The values of these
rates are listed in Table 21.  These "best rates" are not
the lowest rates indicated for each engine class, but are
rates near the low end of those emission rates that appear
to be realistically attainable.  The use of the "best rate"
basis is necessary to allow effectiveness estimates for each
engine class.  Because of the wide variations in actual
emission rates of turbine engines, an effectiveness analysis
based on average rates would be less significant.  Table 22
indicates the effectiveness of control methods t2 through
t8.  Some estimates are based upon demonstrated performance.
Most, however, are not based on direct experience with these
control methods on aircraft engines.  Therefore, estimates
of effectiveness are based largely on theoretical analyses
of engine performance under the operating conditions
associated with the control methods.  The bases for these
estimates are summarized in Table 23.
                                   58
-------
Table 21.  EFFECTIVENESS OF tl  - MINOR COMBUSTION CHAMBER

REDESIGN3 - ON REDUCTION OF EMISSIONS FROM TURBINE ENGINES
        \
         (Emission rates in lb/1000 Ib of fuel)
Engine
class
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T3
T3
T3
T3
Pollutant
CO
THC
NOX
DP
CO
THC
NO*
DP
CO
THC
NOX
DP
Mode
Idle/taxi
25
10
3
0.2
45
10
2
0.2
50
10
3
0.1
Approach
5
1
7
0.5
6
1
6
0.5
3
1
10
0.1
Takeoff
2
0.2
11
0.5
1
0.1
12
0.5
0.5
0.1
40
0.1
Minor combustor redesign is assumed
invisible or "smokeless" levels for
to reduce the smoke to
all engine classes.
                        59
-------
                                     Table  22
                 Effectiveness  of Engine  Modification  in  Control
              of Emissions from Turbine Engines,  by Operating Mode3
Control
method
t2b
t2
t2
t2
t3
t3
t3
t4
t4
t4
t4
t4
t4
t5
t5
t5
t6
t6
t6
t6
t6
t6
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
t7 or t8
Engine
class
Tl
Tl
T2
T3
Tl
T2
T3
Tl
Tl
T2
T2
T3
T3
Tl
T2
T3
Tl
Tl
T2
T2
T3
T3
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T3
T3
T3
T3
Pollutant
DP
NO

Idle/taxi
0.5
NCC
DPX 1 0.5
NOX | NC
THC
THC
THC
CO
THC
CO
THC
CO
THC
NOX
NOX
NOX
CO
THC
CO
THC
CO
THC
CO
THC
NOX
DP
CO
THC
NOX
DP
CO
THC
N°x
DP
NC
NC
NC
0.25
0.25
0.25
0.25
0.25
0.25
NC
NC
NC
0.5
0.5
0.5
0.5
0.5
0.5
0.1
0.1
NC
0.5
0.1
0.1
NC
0.5
0.1
0.1
NC
0.5
Mode
Approach
0.5
NC
0.5
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
0.5
NC
NC
NC
0.5
NC
NC
NC
0.5
Takeoff
0.5
0.5
0.5
0.5
0d
fld
fld
NC
NC
NC
NC
NC
NC
0.1
0.1
0.1
NC
NC
NC
NC
NC
NC
NC
NC
0.75
0.5
NC
NC
0.75
0.5
NC
NC
0.75
0.5
aEmission rate is fraction of best current rate assumed to be attainable
 through minor combustion chamber redesign and with control method cited

 t2 = Major combustion chamber redesign
 t3 = Fuel drainage control
 t4 = Divided fuel supply system
 t5 = Water injection
 t6 = Modify compressor air bleed rate
 t7 = Variable-geometry combustion chamber
 t8 = Staged injection combustor

CNC indicates no change

^Refers to raw fuel drainage only
                                          60
-------
                                        Table 23

            Bases for Control Method Effectiveness Estimates for Turbine Engines
      Control method
                         Rationale
tl - Minor combustion
     chamber redesign
t2 - Major combustion
     chamber redesign
t3 - Fuel drainage control
t4 - Divided fuel supply
     system
t5 - Water injection
t6 - Modify compressor air
t7 - Variable-geometry
     combustion chamber

t8 - Staged injection
     combustor
 The  assumption  is made  that emission rates  for  all
 engines within  a given  class can be reduced to  common,
 optimum levels  (on  a  lb/1000 Ib fuel basis) by  minor
 combustor modifications.  These optimum emission  rates
 are  based on  the best performance reported  for  each
 engine class, excluding extreme data points.
 Estimates are based on  reports of carbureting fuel
 injector performance  and reduction of  smoke emission.
 Concept is  incorporated in some Class  T3 engines.
 Estimates are based on  assumption that best emission
 rate for Class  Tl and T2 engines is at an exhaust
 visibility  threshold  at maximum power.  Carburetion
 appears to  reduce smoke level, and presumably particu-
 late emissions, to  approximately half  that  level.  Addi-
 tionally, premixing of  air and fuel can be used to give
 substantial NOX reduction by decreasing residence time
 in the combustor.
 Estimate is based on  the assumption that fuel drainage
 can  be completely eliminated by collecting drained fuel
 and  returning to fuel tank.
 Control method  results  in combustion zone fuel-air ratio
 similar to  that at  approach condition.  Reduction in CO
 and  THC from idle to  approach is approximately  90 per-
 cent  in Class Tl and  T2 engines and 90 percent  in
 Class T3 engines.  Effectiveness is reduced by  one order
 because combustor is  not operating at  "well-designed"
 condition.
 Water injection is  assumed only at takeoff at a rate
 up to twice the fuel  rate.  Water injection into
 compressor or diffuser  is assumed to be by system
 similar to those in current use.  Effectiveness based
                                            9 P
 upon published  results with steam injection.    Water
 injection assumed to be of equal effectiveness when
 injected upstream of combustor.
 Assumptions are (1) fraction of air that can be bled is
 small so that engine operating point is nearly unchanged,
 (2)  combustor f/a varies inversely with air bleed rate,
 and  (3) CO and THC emissions at idle vary as the  (air
 mass flow rate)^ and  inversely as (f/a) .  This
 relationship is based upon data from Reference  14.
 If maximum air bleed rate is 20 percent, CO and THC
 emission rates  are reduced by 50 percent.
 Combustor primary zone is assumed to operate at a con-
 stant f/a equal to normal f/a at approach power condition
 (primary equivalence ratio = 0.6).   CO and THC emissions
 at idle are reduced to levels corresponding to approach
 power, or by 90 percent for Classes Tl, T2, and T3.   This
 incorporates design characteristics that provide a good
mixture in the combustion zone.  This feature and con-
 stant f/a operation combine to reduce NOX emissions at
 full power by 75 percent^" and particulate emissions by
 50 percent at all power levels as in t2.
                                               61
-------
    Emission-control effectiveness is indicated in Tables
21t 22, and 23 for each control method and for each
pollutant for which a significant degree of control
expected.  Pollutants for which little or no control
expected are not listed.  Effectiveness is indicated
separately for each engine class.  No specific estimates
have been made for control of reactive hydrocarbons, odor,
or aldehydes because control methods applicable to these
emissions are not yet identified.  Reductions in these
emissions are expected along with reductions in THC
emissions.  Any of the modifications defined for existing
turbine engines (tl through t6) could be combined to achieve
increased emission control effectiveness; exceptions are
modifications t4 and t6, which are mutually exclusive.

Piston Engines - The control methods considered feasible for
aircraft piston engines are listed with brief descriptions
in Table 2U.  These methods include most of the approaches
that have been developed for automotive engines for control
of carbon monoxide and total hydrocarbon.  Methods for
controlling nitrogen oxide (NOx) emissions are not included
because the fuel-rich operating conditions of aircraft
piston engines result in low NOx emission rates.  Piston
engine emission characteristics are included in Figure 11.
As this figure indicates, fuel-air ratio has a significant
effect on aircraft piston engine emissions.  Plans for
changes in engine operating conditions to reduce CO and THC
emissions must also consider NOx to prevent significant
increases in emissions of this pollutant.

    Table 24 lists nine piston-engine control methods,
including the use of direct-flame afterburners and water
injection, methods that are not being considered currently
for automotive engines.  Afterburners might be used to
advantage in this application because they can utilize the
high-velocity airflow around the aircraft.  Although
aircraft piston engines and automobile engines are
fundamentally similar, their applications are significantly
different, with different requirements.  Reliability is of
primary importance in aircraft piston engine applications
and therefore is given paramount consideration in
identifying applicable control methods.  The piston-engine
emission-control methods were identified and evaluated
through reviews of published investigations.  Of the methods
identified, all are considered applicable to existing
engines except those that would reguire redesign of the
basic engine or its control systems.

    Effectiveness estimates for piston engines are based on
reductions of current uncontrolled rates listed in Table 25.
                                    62
-------
                                       Table 24

                      Engine Modifications for Emission Control
                       for Existing and Future Piston Engines
       Control method
                     Modification
Existing engines
  pi - Fuel-air ratio
       control

  p2 - Simple air injection
  p3 - Thermal reactors
  p4 - Catalytic reactors
       for HC and CO
       control

  p5 - Direct-flame
       afterburner

  p6 - Water injection
  p7 - Positive crankcase
       ventilation
  p8 - Evaporative emission
       controls
Future engines
  p9 - Engine redesign
Limiting rich fuel-air ratios to only those
necessary for operational reliability.

Air injected at controlled rate into each engine
exhaust port.

Air injection thermal reactor installed in place of,
or downstream of, exhaust manifold.

Air injection catalytic reactor installed in exhaust
system.  Operation with lead-free or low-lead fuel
required.

Thermal reactor with injection of air and additional
fuel installed in exhaust system.

Water injected into intake manifold with simultaneous
reduction in fuel rate to provide for cooler engine
operation at leaner fuel-air ratios.

Current PCV system used with automotive engines applied
to aircraft engines.  Effective only in combination
with one of preceding control methods.

A group of control methods used singly or in combina-
tion to reduce evaporative losses from the fuel system.
Control methods commonly include charcoal absorbers and
vapor traps in combination with relatively complex
valving and fuel flow systems.
Coordinated redesign of combustion chamber geometry,
compression ratio, fuel distribution system, spark and
valve timing, fuel-air ratio, and cylinder wall temper-
ature to minimize emissions while maintaining opera-
tional reliability.
                                              63
-------
                              -sq-[ QOOI/'sqi) suofssTuia XON  put? DHI
                                 O
                                 CM
                                   O
                                   O
             O
             00
                                                                  o
W
O
    co
    CJ
    H
    H
    CO
    M
    Pi

    13
PS
<
PC
u


§
M
C/3
CO
M
S
W

w
    W


    §
    H
    CO
    M
    P-i
                                                                                o
                                                                                •H
                                                                                0)
                                                                                a
                    O
                    O
                      o
                      o
O
O
CXI
O
O
o
o
o
oo
o
o
o
o
o
o
Csl
                                                                           OO
                            'sq-[  OOOI/'scl~[)
                                           o     o

                                        Om-
-------
                                TABLE 25
                  CURRENT UNCONTROLLED EMISSION RATES
                          FOR PISTON ENGINES29
                          (lb/1000 Ib of fuel)
Pollutant
CO
THCa
NOX (as N02)
Idle
896
48
7
Taxi
882
76
4
Approach
918
80
4
Takeoff
849
18
6
a Total hydrocarbon (THC) emission rates have been increased by 50% to
  account for crankcase blow-by emissions.  Evaporative emissions are
  not included in these rates.
                                TABLE 26
                EFFECTIVENESS OF ENGINE MODIFICATIONS IN
                CONTROL OF EMISSIONS FROM PISTON ENGINES
                             BY POLLUTANT3
Controlled
Control Method CO
PI
P2
P3
P4
P5

P6
P7

P8
P9
Fuel-air ratio control
- Simple air injection
- Thermal reactor
- Catalytic reactor
(requires lead-free fuel)
- Direct-flame
afterburner
- Water injection
- Positive crankcase
ventilation (PCV)
- Evaporative emission
control
- Engine redesign
0.5
0.1
0.1
0.1

0.1
0.1

NC
NC
0.1
Emission Rate
THCb
0.5
0.5
0.25
0.25

0.1
0.25

d
e
0.5
  Emission rate is fraction of uncontrolled emission rate after installation
  of control method and applies to all operating modes.
b Exhaust HC only.
c NC indicates no change.
" PCV would eliminate blow-by emissions when used in combination with pi,
  p2, p3, p4, p5, or p8.  Blow-by THC emission estimated to be equal to
  30% of uncontrolled exhaust emission.
e Evaporative controls would reduce THC emissions due to evaporation from
  fuel supply.  Magnutude  of uncontrolled emissions is inknown.

                                        65
-------
Since emission rates from piston engines do not vary as
widely as those from turbine engines, control effectiveness
can be based on average rates for existing engines.  The
effectiveness estimates shown in Table 26 are based in most
cases on the application of individual control methods
without other engine changes.  Method p7 (PCV) is an
exception; it is considered to be most effective in
combination with method pi, p2, p3, pi, p5, p6, or p9.

    Piston-engine modifications p2 through p6 are designed
to serve the same function and, thus, are mutually
exclusive.  All of the others could be combined with any of
the modifications p2 through p6 to achieve increased
emission-control effectiveness.

Cost and Time Requirements for Control-Method Development
and Implementation

Existing Engines - Estimates of the cost and time
requirements of applying each control method applicable to
existing engines are preliminary and are intended to
indicate the magnitude of costs and time involved in
controlling emissions from all civil aircraft.  Cost and
time requirements are estimated separately for control-
method development and implementation.  Development includes
all effort required from initial stages through
certification of the control method for a specific engine
class and tooling for production.  Implementation includes
initial installation of the control method on all engines of
a given class and costs associated with additional effort or
materials required for the control method throughout the
remaining service life of the engines.  These estimates are
based on a turbine engine life of 10 years with engine
overhauls every 5,000 hours or 2 1/2 years and a piston
engine life of 10 years with engine overhauls every 5,000
hours or 5 years.  Operating costs for water injection are
based upon experience with the water injection system on the
Boeing 717 aircraft.

    Because few of the control methods have been developed
for or applied to aircraft engines, and because many factors
affect total implementation costs, many uncertainties are
involved in the estimates.  Estimates of development costs
and time requirements are based on the previous experience
of aircraft engine manufacturers in similar modifications.
Estimates of implementation costs are considered to be less
certain than development costs.  The cost and service life
of a modified engine component is difficult to predict
accurately.  Yet these factors strongly affect the
cumulative costs of operating and maintaining the modified
                                     66
-------
engine.  Because implementation costs could be far greater
than development costs for some control methods, the
estimates of implementation costs are only indicative of
cost penalties that might be involved with control-method
implementation.

    Three potential levels of aircraft emission control
entail three distinct associated cost levels:  (1)
retrofitting in-use engines, (2) modifying present
production designs to incorporate emission control
technology in new engines of models presently being
produced, and  (3) incorporating emission control technology
into new engine designs during the design phases of a new
engine model.

    Costs are highest for retrofitting in-use engines, are
significantly lower for modifying existing designs in new
production engines and are lowest for incorporating emission
technology during engine design.  Table 27 presents
estimates of the development time, development costs, and
implementation costs for application of the control methods
that could be retrofitted on the current population of all
civil engines.

    The development time requirements listed in Table 27 are
the periods required to reach the point where installation
of the control methods in existing engines could begin.  The
application of controls in all existing engines would
require an additional time period that depends primarily on
the availability of engine maintenance facilities.  The time
for implementation is estimated to be 2 1/2 years for
turbine engines and 5 years for piston engines.  These time
estimates allow implementation of the emission control
method during normal maintenance procedures,  minimizing
cost.  Table 28 presents costs by category: air carrier,
general aviation, and civil aviation.  These tables
represent cost to retrofit the various control methods to
the current population of aircraft.

    From another perspective, implementation costs may be
expressed as fractions of total engine costs.  For a typical
class T2 (turbine)  engine, the cost of installing and
maintaining control systems ranges from $300 to $69,900,
assuming a 10-year engine life.  Based on a total engine
cost of $250,000, these control-method implementation costs
represent 0.1 to 25 percent of the total engine cost.  For a
typical piston engine, estimated control-method
implementation costs range from $100 to $4,000, also based
upon a 10-year engine life.  For a total engine cost of
                                    67
-------
                                   Table 27

                  Time and Costs for Modification of Current
                           Civil Aviation3 Engines
Control method
Turbine engines
Minor combustion
chamber redesign
Major combustion
chamber redesign
Fuel drainage control
Divided fuel supply
Water injection
Compressor air bleed
Piston engines
Simple air injection
Thermal reactor
Catalytic reactor
Direct-flame
afterburner
Water injection
Positive crankcase
ventilation
Evaporative emission
control
Development
time,
years
2.5 to 5
2.5 to 7.5
1 to 2.5
5 to 7.5
2.5 to 4
4 to 6.5
1.5 to 3
3 to 6
2.5 to 5
3 to 6
1.5 to 3
2 to 4
1.5 to 2.5
Development
cost,
106 dollars
37
74
1.5
84
25
90
9
25
22
25
9
4
4
Implementation
cost,
10° dollars
383
665
5.4
102
175
58
165
424
535
424
400
94
269
lnCivil  aviation"  includes  air carrier and general aviation engines
                                           68
-------
                                       Table  28

                      Cost Results for Turbine Engine Population
                              by Separate  Use  Categories
Engine
class
Tl
Tl
Tl
Tl
Tl
Tl
T2
T2
T2
T2
T2
T2
T3
T3
T3
T3
T3
T3
Control
method
tl
t2
t3
t4
t5
t6
tl
t2
t3
t4
t5
t6
tl
t2
t3
t4
t5
t6
"
Cost
scaling
factor
0.35
0.35
0.35
0.35
0.35
1.00
1.00
--
1.00
1.00
1.00
1.64
1.64
1.64
1.64
1.64
1.64
Development
cost per
engine family,
106 dollars
0.90
1.80
0.05
1.80
0.62
2.20
0.90
1.80
0.05
1.80
0.62
2.20
0.90
1.80
0.05
1.80
0.62
2.20
Implementa-
tion cost
per engine,
10-3 dollars
12.4
21.3
0.1
3.7
5.5
2.1
35.5
69.9
0.3
10.5
15.6
6.0
58.3
100.0
0.6
17.2
25.6
9.9
Total cost, 106 dollars
Air
carrier
19.2
34.5
0.4
14.9
9.8
15.5
243.0
418.0
2.0
87.0
108.7
61.5
50.0
95.0
2.0
13.7
29.5
16.0
General
aviation
90.5
159.3
1.0
51.5
43.6
48.1
17.8
31.0
--
8.3
8.2
7.1
--
--
--
--
--
--
Civil
aviation3
109.7
193.8
1.4
66.4
53.4
63.6
259.8
449.6
2.0
95.3
116.9
68.6
50.0
95.0
2.0
13.7
29.5
16.0
a"Civil  aviation"  includes  air carrier and general  aviation engines
                                             69
-------
$6,000, these implementation costs represent 2 to 65 percent
of the total.

    Retrofit cost and time estimates for turbine engines
were developed by using the application of low-smoke
combustors to the JT8D engine class as a reference for cases
in which no direct experience was available.  Cost and time
requirements for this modification, which is considered a
minor combustor redesign for a class T2 engine, were
estimated in detail in 1969.27 Requirements for other
control methods were determined essentially by proportioning
the cost and time expenditures according to the complexity
of the method, with respect to the reference case.
Requirements for other engine classes were determined by
using appropriate scaling factors and by again using the
JT8D modifications as reference.  Time and cost estimates
for piston engines are based largely on experience to date
with emission controls for automobile engines,  significant
differences, such as certification and safety requirements
and production levels, were considered in scaling the costs
from the experience with automobiles.

    Costs of emission control technology are substantially
lower when applied to new engines only.  These costs are
less than one-half the retrofit costs on a per-engine basis.
These estimates cannot be totalled as were the retrofit
estimates because of uncertainty concerning the number of
engines that would be affected.

Future Engines - Cost estimates have been developed also for
incorporation of emission controls in future engines, that
is, engines that have not yet been developed.  These
estimates are defined only as fractions of total engine
cost, since no reasonable basis is available for estimating
the numbers of engines that would be affected.

    Emission control in turbine engines that is attained
through the use of advanced combustor-design concepts is
estimated to represent an increase in total engine cost of 3
to 1 percent.  Emission control in piston engines that is
achieved by engine-design modifications would not
necessarily result in any significant increase in engine
cost.  If greater control of emissions is required than can
be achieved by engine design modifications, however, one or
more of the control methods applicable to existing engines
will be necessary.  The costs of these control methods,
which involve the addition of auxiliary devices such as
thermal reactors, will be significant, probably in the range
of 5 to 10 percent of total engine cost.
                                    70
-------
    These estimates represent the increased costs of new
engines with emission controls installed.  Additional
continuing costs may accrue for maintenance of the controls.
These maintenance costs will be considerably less than those
entailed in modifications of existing engines.

 EMISSION CONTROL BY MODIFICATION OF GROUND OPERATIONS

Definition of Ground Operations

    The cycle of operations performed by an aircraft during
its arrival at and departure from an airport can be defined
quite precisely because most of these operations are
prescribed by airport or aircraft operating procedures.
Characteristic operating or LTO (landing-takeoff) cycles
have been defined for various classes of aircraft for
purposes of estimating pollutant emissions.

    The LTO cycle can be separated logically into flight and
ground operations.  Flight operations include the approach
and climb-out modes as well as landing and takeoff, even
though the latter occur partially on the ground.  Ground
operations include the taxi and idle modes of the cycle.
This separation is logical for two reasons.  First, flight
operations as defined here are those that cannot readily be
modified to reduce pollutant emissions.  Second, flight
operations are conducted almost entirely with aircraft
engines at full or part power; under these conditions,
pollutant emission rates are quite different from those at
the low power levels characteristic of ground operations.
Aircraft ground operations contribute substantially to the
concentrations of CO and THC at air carrier airports because
of the relatively high emission rates of these pollutants at
low engine power levels, and because ground operations are
largely confined to limited areas within the airport
boundaries.

Emission Control Methods

    Six methods offer some degree of control of CO and THC
emissions at air carrier airports by modification of
turbine-aircraft ground-operation procedures.

        (1) Increase engine speed during idle and taxi
operations.

        (2) Increase engine speed and reduce number of
engines operating during idle and taxi.
                                    71
-------
       (3) Reduce idle operating time by controlling
departure times from gates.
           Reduce taxi operating time by transporting
passengers to aircraft.

       (5)  Reduce taxi operating time by towing aircraft
between runway and gate.

       (6)  Reduce operating time of aircraft auxiliary power
supply by providing ground-based power supply.

    The first two methods reduce emissions by requiring that
engines be operated at more efficient power settings than
those in current practice (Figure 12) ; the next four methods
reduce emissions by reducing operating time of either main
or auxiliary engines.  The effectiveness of these methods in
reducing emissions varies considerably.  Table 29 summarizes
the reductions in CO and THC emissions that would result at
Los Angeles International Airport from the six suggested
ground-operation changes.  Tables developed for other major
air carrier airports show emission reductions of the same
magnitude.

    The control methods listed, with the possible exception
of number 3, are not applicable to small, piston-engine
aircraft, and, therefore, do not seem to offer means for
controlling emissions at general aviation airports.  Periods
of delay at take-off are significant at some general
aviation airports; however, aircraft ground traffic at
general aviation airports may not be sufficiently controlled
to allow an effective system of controlled gate departures
or engine start-ups to reduce periods of delay.

Implementation Cost and Time Requirements

    The cost and time requirements of the contrcl methods
involving ground operation modifications have been estimated
for Los Angeles International.  Table 30 presents summary of
the estimates.  Implementation of these methods at other
airports would involve costs of the same magnitude.
Specific costs, however,  would vary with airport activity
level and the present availability of auxiliary equipment.
FAA and the airlines have estimated savings for control
method 2, and their estimates are within 2 OX of the estimate
in Table 30.

    Tables 29 and 30 indicate that alternative 2 is the most
attractive means of reducing turbine aircraft emissions
                                    72
-------
               Normal Taxi-idle
V-i

o
f.

S-l
0)
ex

0)
c
•1-1
60

0)
0)
ex

en
a)
•H
o
a)
a
tn
O
cx
en
•O
C

O
a,
en
C
O
•H
CO
CO
•H

W
    120
100
 80
     60
 40
 20
                    Modified Taxi-idle
                                               Carbon Monoxide
                                               I
                           20                 40

                                 Percent  Thrust
                                                             60
                       FIGURE 12


      HYDROCARBON  AND CARBON MONOXIDE  EMISSIONS

    FROM A TYPICAL AIRCRAFT TURBINE  ENGINE (JT3D)
                                73
-------
                      Table  29

   Comparative Reductions Resulting from Control
Methods Applied at Los Angeles International Airport
                                         Resultant emissions,
Control method
1.
2.


3.
4.
5.
6.
Increase engine idle speed
Increase idle speed and use minimal
engines for taxi
Two engines
Single engine
Eliminate delays at gate and runway
Transport passengers between
terminal and aircraft
Tow aircraft to avoid taxi emissions
Avoid use of aircraft auxiliary
power units (APU)
/„ or uncontrolled
emissions
CO
71

53
39
90
98
34
96
Hydrocarbons
93

66
51
91
97
42
98.5
                              74
-------
                                Table  30

                 Costs and Time for Operations Changes
                  at Los Angeles International Airport
Control method
1.
2.
3.
4.
5.
6.
Increase engine speed
Increase speed, reduce
number
Control gate departure
Transport passengers
Tow aircraft
Reduce APU operation
Time,
years
0
0.3
5
2.5
1
0.5
Initial cost,
106 dollars
0
0
15
65
1.2
1.3
Annual operating
cost change,3
106 dollars
8.5
-0.7
-0.4
5.0
0.4
1.5
T^inus sign indicates an estimated savings
                                        75
-------
providing that operational and safety requirements can be
met.

 COMPARATIVE EVALUATION OF EMISSION CONTROL METHODS

    The engine and ground operation modifications just
discussed can be compared in terms of effectiveness, cost,
and implementation time.  A "potential benefit factor" has
been defined to allow comparison of cost/benefit of the
emission control methods.  The potential benefit factor
(PBF)  is the net emission reduction resulting from a
particular control strategy, averaged over the next 20
years, divided by the cost.

                  PBF = FYE x CE x ECF
                              CP

where FYE is the fraction of the next 20 years that the
control method is effective; CE is the control method
effectiveness (the percentage reduction of a particulate
pollutant);  ECF is the emission contribution fraction
(percentage of total aircraft emissions at relevant airports
contributed by engines affected by this control strategy);
and CP is the cost of the control strategy for the pollutant
considered.  Emissions at major carrier airports were used
to determine effectiveness of turbine engine control methods
and those at general aviation airports to determine
effectiveness of piston engine emission control methods.

    The potential benefit factor is a measure of the cost-
effectiveness of each control strategy.  Potential benefit
factors (Table 31) have been calculated for the control
strategies previously described as applied to (1)
retrofitting in-use aircraft, (2)  modifying new engines of
present models, and (3)  incorporating control methods in new
engine designs.  The higher numbers represent the most cost-
effective strategies for emission reduction.

    The potential benefit factors in Table 31 are a
composite for all turbine and piston engines.  Although
these factors indicate the relative merits of the control
methods, the factor for an individual engine classification
may be significantly different.  For example, retrofit of
water injection for class T3 shows a potential benefit
factor of 4.2, whereas the average for all turbine engines
is only 1.1.  Additionally, while some control strategies
show a high potential benefit number, other strategies must
also be used to achieve significant emission reductions.
For example, fuel venting represents from t to 20% of total
hydrocarbon emissions, dependent upon airport considered.
                                     76
-------
               Table 31




Comparison of Emission Control Methods
Control Method

Turbine Engines
A. Retrofit-Engine Modifications
1. Minor combustion chamber redesign
(APU)
2. Major combustion chamber redesign
(T3 and APU)
(T2 only)
3. Fuel drainage control
(T2 and T3 only)
4. Divided fuel supply
5. Water injection
(T3 only)
6. Compressor air bleed
B. New Production Engine Modification
1. Minor combustion chamber redesign
2. Major combustion chamber redesign
3. Fuel drainage control
4. Divided fuel supply
5. Water injection
(T3 only)
6. Compressor air bleed
C. Future Engine Emission Control
1. Fuel drainage control
2. Divided fuel supply
3. Water injection
(T3 only)
4. Compressor air bleed
5. Variable geometry combustion chamber
6. Staged injection combustor
D. Ground Operations Modification
1. Increase engine idle speed
2. Increase speed, reduce number
3. Eliminate delays
4. Transport passengers
5. Tow aircraft
6. Reduce APU operation
Piston Engine
A. Retrofit-Engine Modification
1. Fuel-air ratio control
2. Air injection
3. Thermal reactor

Potential Benefit Factor
HC & CO


0.37
(2.5)
0.3


10
(20)
1.5
--

1.3

5.0
4.6
30
5.0
--

4.0

30
15
--

15
25
25

2.4
105
10
0.1
75
1.0


50
5
2

NOX


0.37

1.1
(6.6)

--

--
1.4
(4.2)
--

5.0
4.6
--
--
1.4
(4.2)
--

--
--
2.0
(5.6)
--
25
25

--
--
--
--
--
--


--

--
Smoke


0.37

1.1

(5.0)
--

--
--

--

5.0
4.6
--
--
--

--

--
--
--

--
25
25

--
--
--
--
--
--


--
--
--
I
                      77
-------
           Table 31 (Cont.)




Comparison of Emission Control Methods
Control Method
4. Catalytic reactor
5. Direct-flame afterburner
6. Water injection
7. Positive crankcase ventilation
8. Evaporative emission control
B. New Production Engine Modifications
1. Fuel-air ratio control
2. Air injection
3. Thermal reactor
4. Catalytic reactor
5. Direct-flame afterburner
6. Water injection
7. Positive crankcase ventilation
8. Evaporative emission control
C. Future Engines
1. Fuel-air ratio control
2. Air injection
3. Thermal reactor
4. Catalytic reactor
5. Direct-flame afterburner
6. Water injection
7. Positive crankcase ventilation
8. Evaporative emission control
9. Engine redesign
D. Ground Operations Modifications
1. Eliminate delays
Potential Benefit Factor
HC & CO
1.5
1
2
3
1-5
500
30
6.6
5.0
3.3
15
50
3.0
500
30
6.6
5.0
3.3
15
50
6.0
25
10
NOX
--
—
--

::
—
—
--

—
--
- -
"
--
Smoke
--
—
--

—
--
—
--

::
—

::
--
                       78
-------
Consequently, to achieve substantial reduction of
hydrocarbon emissions a less attractive control method is
necessary in addition to eliminating fuel venting.

    A review of the PBF values in Table 31 supports the
following conclusions providing that all operational and
safety requirements can be met:

       (1) Modification 2 for ground operation procedures is
the most cost-effective method of reducing hydrocarbon and
carbon monoxide emissions from turbine engines,

       (2) Incorporating emission control methods into
design of new engines is the most cost-effective method of
over-all aircraft emission control.

       (3) Control of fuel-air ratio is the most cost-
effective method of reducing hydrocarbon and carbon monoxide
emissions from piston engines,

       (I) Retrofits of class T3 turbines is a more cost-
effective method for NOx control compared to retrofit of
other turbine engine classes.

       (5) Fuel drainage control has high PBF because of
extremely low cost of implementation (CP)  rather than high
control effectiveness (CE).

       Because cost-effectiveness varies significantly among
engine classes and control strategies, several factors in
addition to cost and effectiveness must be considered in
developing emission control strategies for aircraft engines.

EMISSION MEASUREMENT TECHNOLOGY

    Reliable methods for measuring the rates at which
pollutants are emitted from aircraft engines are required
for the support of an emission-control program.  Emission
measurements are required for evaluating the effectiveness
of control methods, and specific measurement methods must be
incorporated in emission-control standards.

    The state of emission-measurement technology has been
assessed to determine whether measurement techniques are
sufficiently well advanced to support the development of
emission-control methods and the implementation of emission
standards for aircraft engines.  The conclusion drawn from
this assessment is that current measurement technology will
meet the reguirements of an emission-control program.
Although measurement techniques for particulate emissions
                                     79
-------
are inadequate at present, improved techniques are beinq
developed throuqh cooperative qovernment-industry action.

    Measurement of emission rates from an aircraft enqine
involves three major requirements:

        (1) A test procedure specifyinq enqine operatinq
conditions.

        (2) A samplinq technique for obtaininq a
representative sample of exhaust qas.

        (3) Analytical instrumentation for determininq
pollutant concentrations in the exhaust-qas sample.

    Aircraft enqine manufacturers, FAA, and EPA are devotinq
substantial effort toward meetinq these requirements for
measurinq emissions from turbine enqines.

Samplinq and Test Procedures

    Obtaininq a representative sample of exhaust qas from an
aircraft enqine for analysis of emission rates is a complex
and difficult procedure.  Samplinq emissions from turbine
enqines is difficult at the outset because of the jet-blast
environment in which the samplinq equipment must be
installed.  Beyond this problem, the followinq factors all
siqnificantly affect the composition of the exhaust sample:

        (1) Enqine power level.

        (2) Temporal and spatial variations in exhaust
composition.

        (3) Samplinq-line diameter, lenqth, material, and
temperature.

        CO Ambient temperature and humidity.

        (5) Ambient pollutant levels.

    Procedures for samplinq and analyzinq turbine-enqine
exhaust qases have been under development for several years
by enqine manufacturers, FAA, and EPA.  More recently, the
Society of Automotive Enqineers Aircraft Exhaust Emission
Measurement (E-31) Committee has been formed to standardize
these procedures.  Standardization of measurement techniques
will minimize variations resultinq from the factors listed
above; however, the several sources of error in collectinq
exhaust samples and the variability of samples among
                                    80
-------
different engines must be considered in the establishment of
a standard emission measurement procedure.

    Sampling requirements for aircraft piston engines are
similar to those for automobile engines.  The exhaust gases
are well mixed by the time they reach the exhaust stack
exit.  Consequently, no factors are apparent, beyond those
already recognized as affecting automobile exhaust
emissions, that would cause variability in exhaust samples
from aircraft piston engines.  Differences in engine
operation, however, must be considered in the establishment
of a standard emission measurement procedure.

Emissions Measurement Instrumentation

    Measuring the concentrations of most gaseous pollutants
in exhaust samples from aircraft engines is generally within
the capabilities of existing instruments and should remain
so, even when engines are modified to reduce emission rates.

    The various types of instruments that are available and
in current use for aircraft emission measurement have been
reviewed.  Instruments that appear to be most suitable for
measuring turbine-engine emissions at the present time are
presented in Table 32.
                                    81
-------
                        Table  32

            Instrumentation for Measurement
              of Turbine Engine Emissions
      Measurement method
Non-dispersive infrared (NDIR)

Heated flame ionization

Chemiluminescence

Chemiluminescence3

SAE smokemeter (ARP1179)

None

Determined from fuel analysis

3-MBTH

Human odor panel
Pollutant class
   CO and C02

      THC

       NO

      NO 2

     Smoke

  Particulates

      so2

   Aldehydes

      Odor
'The non-dispersive ultraviolet instrument  (NDUV)
 may also prove acceptable for NO.-, measurement
                                82
-------
APPENDIX A:
ANALYSIS OF CARBON  MONOXIDE CONCENTRATION
AT LOS ANGELES INTERNATIONAL  AIRPORT
  When continuous air quality monitoring data is  available,
  statistical analysis may be applied to determine frequencies
  of occurrence of any concentration for any averaging time
  either  by interpolation of the data or by extrapolation if
  the available data is limited.  It has been observed that
  all air quality data regardless of averaging time follows a
  log normal distribution.13

  The continuous carbon monoxide data taken at LAX during six
  months  in 1970 were analyzed statistically for  1-hour and 8-
  hour averaging times at several sites to determine the
  expected frequencies when the NAAQS would be exceeded.  With
  the use of the simple rollback technique, adjusted
  frequencies could be determined for changes in  emissions and
  various control strategies for aircraft and non-aircraft
  emission sources.  Dispersion modeling results  were used to
  predict the degree of influence aircraft emissions have in
  locations beyond the boundaries of Los Angeles  Airport.

  The analysis focused on the 8-hour exposure case in areas
  adjacent to the airport where it would be expected that
  people  would meet the exposure time criteria either as
  residents or business employees.  The 1-hour exposure case
  would apply to the terminal area itself as well as the areas
  considered in the 8-hour averaging time case.

  Corrections were made to the available ambient  data because
  of the  recognized seasonal variation of carbon  monoxide
  levels  in the Los Angeles basin.  A recent report published
  by the  LAAPCD contained sufficient data to calculate the
  summer-winter correction factors for the hourly and 8-hour
  averaging times.  The average correction factors for the
  basin to convert August-September data to December-January
  data were found to be 1.5 for the 1-hour data and 1.9 for
  the 8-hour case.

  Data and statistical information on carbon monoxide analysis
  presented in a paper by Larsen3* were also utilized in this
  phase of the analysis.   The L. A.  basin CO data in the
  Larsen  paper were used to check the LAX data for consistency
                                     83
-------
in terms of the frequency and range of observed carbon
monoxide levels.  Tabulated and plotted data in this
reference indicate the air pollution hot spot represented by
the Los Angeles Airport and its environs.  Figure A-lr taken
from the reference shows this point quite clearly.  Figure 1
in the main text of this report indicates the location of
the continuous ambient carbon monoxide stations.  Station
209 was chosen as representative of an off airport site for
the 8 and 1-hour analysis.  Figure A-2 shows the plot of the
raw station 209 data for the months of August and September.

It is obvious that station 209 is directly influenced by the
airport only when the wind is blowing from a westerly
direction.  The September data were categorized into East or
West influences and the results are plotted on Figure A-3.
It can be seen that the composite plot is representative of
both these subcategories and therefore was used for all
subsequent analysis.  It further demonstrates that the
airport exerts the same impact on the air quality at station
209 as the non-airport area sources surrounding it.  Figure
2, in the text of the report, shows the August station 209
frequency distributions for maximum 8-hour daily averages
adjusted for the summer-winter correction factor.  The
frequency of occurrence relating to one day per quarter is
assumed to be equivalent to the one day per year frequency
associated with the 8-hour NAAQS because it can be assumed
that the worst exposure case would occur during the winter
quarter of the year.  This plot has then been adjusted
(Figures h-H and A-5)  for expected rollback emission
reductions of non-aircraft sources in combination with
various percent contributions due to due to aircraft sources
and assumed levels of aircraft emission controls.  Similar
methodology was used in estimating expected 1980 CO
concentrations with various aircraft contributions.  These
are given in the main text.  Modeling results were used to
determine the relating distribution and magnitude of
aircraft emissions around LAX.  It can be seen that the
station 209 analysis is quite representative of other areas
adjacent to LAX where adverse influences of aircraft
operations can be expected to occur.

The same procedures were followed in plotting the adjusted
September data to determine the frequency with which the
standard would be expected to be exceeded for various
percent aircraft contributions.  This data would represent
the upper limits of the analysis.

Similar frequency analysis can be performed for the 1-hour
exposure case.  However, unless there is extreme variation
between the slopes  (or standard geometric deviations) of the
                                     84
-------
                             FIGURE A-l.
      MAXIMUM ANNUAL  8-HOUR-AVERAGING-TIME CONCENTRATION OF

CARBON MONOXIDE EXPECTED AT VARIOUS SITES IN THE  LOS  ANGELES AREA.
                          \
                          30

                         SAN FERNANDO

                            VALLEY
   • 32
  28
 PASADENA
 29

DOWNTOWN
                                                               SAN BERNARDINO
                                                                           • REDLANDS
                                                                           21
                                                                                19
                                     85
-------
0
                                                                                                                                O
                                                                                                                               , CM
                                                                                                                                O
                                                                                                                                LT)
                                                                                                                                O
                                                                                                                                oo
                                                                                                                                      0)

                                                                                                                                      0)
                                                                                                                                      c
                                                                                                                                      to
                                                                                                                                      4J
                                                                                                                                      3
                                                                                                                                      •H
                                                                                                                                      O
                                                                                         00
                                                                                         C
                                                                                         •H
                                                                                         TJ
                                                                                         0)
                                                                                         QJ
                                                                                         O
                                                                                         X
                                                                                         w
                                                                                                                                       >1
                                                                                                                                       4-1
                                                                                                                                       •r-l
                                                                                                                                       r—I
                                                                                                                                       •i-l
                                                                                                                                      43
                                                                                                                                       O
                                                                                                                                       PLI
                                                                   i   «
                 O
                 u-i
O
-------
  o
  r>
  a-.
  w
  H
  w
  CO
  o
  
                                                                                                      01
                                                                                                      c
                                                                                                      cd
                                                                                                      O
                                                                                                      cx
                                                                                                      0)
                                                                                                      >
                                                                                                     •H
c
•H
13
0)
QJ
O
•H
rH
•H


n)


O
M
(X,
                                      (mdd)  NOIIVHINaONOD 00
                                                               87
-------
w
O
      X
     o
     OJ
      O
      H
      H
      <
      H
 - H
aS  to
fV|  pQ

H  M
£3  pi
O H
M fn
PQ O
i—i fv;
Pi M
H <

M H
Q £5
   W
IZ CJ
O Pi
M pq
H CM



H CO
O O
;z PM
o
o

o
o

Q
W
H
o
w

X
w
                                                                                                           (U


                                                                                                           0)
                                                                                                           O
                                                                                                           O,

                                                                                                           C
                                                                                                           0)

                                                                                                          •1-1

                                                                                                           00


                                                                                                           60
                                                                                                           C
                                                                                                     Q)
                                                                                                     0)
                                                                                                     o
                                                                                                     X
                                                                                                           •H
                                                                                                           I— I

                                                                                                           •r-l
                                                                                                           o
                                                                                                           ^1
                                                                                                           PH
                                     (uidd)  uoi:)Ea:}uaouo3 00
-------
X
IS M
O H
M p
H P5
<; M
H Pi
W H


Pi u
w
H H
   O
  - Pi
t^r^ i  i

O -^
M
H H


M u

H W
W PH

P O
   CN
O
og

P PH
W
H
O
W
PM
X
w
                                                                                                                   c
                                                                                                                   CO
                                                                                                                   4-1
                                                                                                                   3
                                                                                                                   O
                                                                                                                   a,

                                                                                                                   c
                                                                                                                   0)

                                                                                                                  •H
                                                                                                                   60

                                                                                                                   a.1
                                                                                                                  .c
                                                                                                                   60
                                                                                                                   c
                                                                                                                  •M
                                                                                                                  •a
                                                                                                                   
-------
1-hour data and the 8-hour averaging time data, the 1-hour
standard will be met if the strategies are imposed to meet
the 8-hour standard.  This wculd appear to be the case in
those areas at LAX where the 1-hour CO levels are higher
than the standard at the present time.
                                      90
-------
                      APPENDIX B:

 DISPERSION MODELING METHODOLOGY AND

                ISOPLETH DERIVATION
    The primary and most  direct, method of estimating
aircraft contributions  to air pollutant concentrations
involved the application  of  frequently used dispersion
modeling procedures to  estimate air pollutant concentrations
caused by aircraft alone  and by all sources located in the
airport vicinity (within  a 10-kilometer radius of the
airport center).  Dispersion models similar to the one used
in this study are specified  by EPA as one means of showing
that implementation plans for certain regions will be
adequate to meet the ambient air quality standards.  Much of
the analysis of aircraft  air quality impact presented in
this report is based on modeling work performed, under EPA
contract, by Northern Research and Engineering Corporation.
A general description of  the modeling procedure is presented
here; a more detailed account of the modeling work and
results is available in the  contract report.3

    The procedure in the  modeling study involved: (1)
approximating emission  sources as continuous, stationary
point sources of constant strength over the time period
being considered, (2) modeling the dispersion of pollutants
from these sources using  an  empirical mathematical model,
and  (3)  estimating concentrations at specified receptor
points by summing the pollutant contributions from each
point source, and (U) constructing isopleths of estimated
pollutant concentrations  based on the estimated receptor
point concentrations.

    The point sources used in the modeling approximated the
location and strength of  emission sources at each of the
four airports studied.  Lines along which automobile or
aircraft movement occur were represented by series of point
sources.  Area sources, representing airport surroundings
out to a 10-kilometer radius from the airport center,  were
represented by circular arrangements of point sources around
the airports.  Altogether, 149 to 276 point sources were
used for each air carrier airport, depending on the size and
complexity of the airport.   The number of sources was chosen
to provide a reasonable approximation of emissions at the
                                     91
-------
airport and in the vicinity without need for excessive
computer time or computer program complexity.

    The basis of the atmospheric dispersion modeling is an
empirical, mathematical approximation of pollutant
dispersion after emission from a point source.  This
approximation yields a plume whose concentration
distribution is Gaussian in the vertical and crosswind
direction.  The distribution is dependent upon downwind
distance from the source and on atmospheric stability.
Eventually the upper boundary of the atmospheric mixing
layer restricts vertical spread of the plume and modifies
the distribution of pollutants in the vertical direction.
This dispersion model should be considered as a general
approximation of airport dispersion patterns; considerable
model development would be required to include more detailed
small-scale dispersion patterns, such as those around large
buildings or near jet blasts.

    In calculation of long-term concentrations, the fact
that there is a distribution of meteorological conditions is
used to simplify the basic dispersion model.  The result,
known as the Martin-Tikvart model, approximates plume spread
in the crosswind direction and sums the contributions of all
combinations of wind speeds and atmospheric stabiltities.

    The concentration at any receptor point is obtained as
the sum of the contributions from each point source of
emissions.  The accuracy of the concentration value for this
type of model is dependent upon the proximity of the
receptor point and the emission sources.  Because the
sources of emission are actually a collection of points,
lines areas, and volumes, rather than merely a collection of
points, as assumed in the model, greater accuracy generally
results when the receptor point is not close proximity to
any sources.  To limit inaccuracies attributable to the
point source, receptor locations within 100 meters of a
point source were not considered in the results.

    The model provided estimates of air pollutant
concentrations both from aircraft alone and from all sources
at a number of sites located in and around the selected
airports.  Receptors considered in this study were located
according to the following overall scheme at air carrier
airports: (1) one receptor at the center of each major
terminal, (2) one receptor 100 meters from the head of each
runaway,  (3) sixteen receptors on the airport boundary,
spaced equally on a compass rose located at the designated
center of the airport, and (4)  sixteen more receptors
located in the airport surroundings, 5 kilometers from the
                                      92
-------
center of the airport and spaced equally on the compass
rose.  Not more than 50 receptors were used, the actual
number depending on the number of terminals and runways at
each airport.

The resulting concentrations at the various receptor points
were used in constructing isopleths of pollutant
concentration.  Isopleths were constructed for 6-9 a.m.
hydrocarbon and annual NOx concentrations due tc aircraft
alone, and for aircraft contributions to total CO
concentrations.

    The model input data used in calculating annual
concentrations of NOx were based on yearly distributions of
wind direction, stability class and wind speed class, and
annual average values of mixing height and emission rates.
The short-term meteorological and activity conditions used
to calculate the 8-hour and 1-hour CO conditions and the 6-9
a.m. hydrocarbon concentration were chosen to be
representative of conditions that would be expected to yield
high concentrations of these pollutants, i.e., low wind
speed, high atmospheric stability, and low mixing height,
and moderate to high aircraft activity.  The conditions for
calculation of short-term concentrations are presented in
Table B-l.

    Because the results of the model have not been
extensively validated or verified, the concentrations
generated by the model should be considered to be very
approximate.  They are useful, however, in indicating
general pollutant concentration levels of the extent of
aircraft contributions to localized pollutant concentration.
                                      93
-------
                                      TABLE B-l

                  SHORT-TERM METEOROLOGICAL AND ACTIVITY CONDITIONS
                         6-9 A.M.  HC
                  8-Hour CO
                       at L.A.  Airport   at L.A.  Airport
                                  LAX
                     1-Hour CO
                    ORD    JFK    DCA
Wind speed class
Stability class (Turner)
Wind direction, deg.
Wind variability, deg.
Mixing height, m.
Aircraft activity, 60
LTO cycles. 79
Direction of movement
1
C
255
20
200
(1970)
(1980)
West
1
E
255
20
200
260
West
1
E
90
40
535
54
E
1
F
215
30
700
49
SW
1
E
200
10
960
30
S
1
E
320
20
980
34
N
 Idle time at runway,
        sec.

 Estimated annual
 frequency of occurrence
 of meteorological con-
 itions
   60
at least
  once
150
240
260
540
                                                            81
                     29
                10
300
               67
a These conditions are used in estimating ratios between aircraft generated and total
8-hour CO concentrations; the ratios are not sensitive to the conditions assumed.
b  Based on 5 months of data.
                                                  94
-------
                        APPENDIX C:

AREA - SOURCE DISPERSION MODELING TO ESTIMATE

      DOWNWIND POLLUTANT CONCENTRATIONS
     The modeling method used in this analysis involved
  approximating emissions both at airports and in surrounding
  areas as area sources,  and relating these emissions to
  downwind pollutant concentrations by assuming Gaussian
  pollutant distribution  in the vertical and crosswind
  directions.  For each receptor point, the concentration
  caused by small-area elements was determined by integrating
  in the crosswind and upwind directions over each source
  region.  The airport and surroundings were considered as
  separate source regions.  The concentrations due to these
  two source regions were calculated separately then added
  together to obtain the  total concentration at each receptor.
  Near the airport source, concentrations are the same as
  those from an area source of infinite extent.'«  At greater
  distances, edge effects caused by the finite width of the
  airport are considered  by including the integration in the
  cross-wind direction.  Also included is the limit to
  vertical mixing imposed by a more stable layer aloft.

     For the purpose of  this modeling, the airport was
  assumed to cover an area of 3.2 by 3.2 kilometers.  The time
  period for the analysis, 8 a.m. to 11 a.m., was selected on
  the basis of recurring  meteorological conditions conducive
  to high air pollutant concentrations.  A diurnal correction
  factor was applied to the resulting concentrations to
  correct for the disproportionately greater amount of
  activity that occurred  during this 3-hour period than
  occurred during other 3-hour periods during the day.  The
  specific meteorological conditions used for the time period
  considered were: wind from west; stability class = 3, wind
  speed = 1.5 in/second mixing height = 200 m.  These
  conditions are representative of severe conditions, from an
  air pollution standpoint, that are expected to occur at
  least once a year in the Los Angeles area.
                                      95
-------
                         REFERENCES
 1.  Nature and Control of  Aircraft Engine Exhaust Emissions.  Report
     of the Secretary of Health, Education, and Welfare to the United
     States Congress.  December  1968.

 2.  Jet Aircraft Emissions and  Air Quality in the Vicinity of the
     Los Angeles International Airport.  Air Pollution Control District,
     County of Los Angeles, California.  April 1971.

 3.  The Potential Impact of Aircraft Emissions Upon Air Quality.
     Northern Research and  Engineering Corporation.  Final Report to
     the U. S. Environmental Protection Agency.  Research Triangle Park,
     North Carolina.   Contract Number 68-02-0085.  December 1971.

 4.  Assessment of Aircraft Emission Control Technology.  Northern
     Research and Engineering Corporation.  Final Report to the U. S.
     Environmental Protection Agency.  Research Triangle Park, North
     Carolina.  Contract Number  68-04-0011.  September 1971.

 5.  Analysis of Aircraft Exhaust Emission Measurements.  Cornell
     Aeronautical Laboratory.  Available from NTIS--PB 204-879.  Contract
     Number 68-04-0040.   October 1971.

 6.  National Primary and Secondary Ambient Air Quality Standards.
     Environmental Protection Agency.  Federal Register 36(84):8187,
     April 30, 1971.

 7.  Air Quality Criteria for Hydrocarbons.  U. S. DHEW, PHS, EHS,
     National Air Pollution Control Administration.  Publication Number
     AP-64.  Washington, D.  C.  March 1970.

 8.  Federal Air Quality Control Regions.  Environmental Protection
     Agency, Office of Air  Programs, Research Triangle Park,  North
     Carolina.  Publication Number AP-102.  January 1972.

 9.  Requirements for Preparation, Adoption, and Submittal of Implemen-
     tation Plans.  Environmental Protection Agency.  Federal Register
     3^(158):15486, August  14, 1971.

10.  Mixing Heights,  Wind Speeds, and Potential for Urban Air Pollution
     Throughout the Contiguous United States.   Environmental  Protection
     Agency, Office of Air  Programs, Research Triangle Park,  North
     Carolina.  Publication Number AP-101. January 1972.

11.  Climatography of U.  S.,  Summary of Observations for Los  Angeles
     International  Airport,  1951-1960.  U. S.  Department of Commerce,
     Weather Bureau.   Washington, D. C.  1962.
                                        97
-------
12.  The State of California Implementation Plan  for Achieving  and
     Maintaining the National Ambient  Air  Quality Standards.  California
     Air Resources Board.   Sacramento, California.  January  1972.

13.  A Mathematical Model  for Relating Air Quality Measurements  to Air
     Quality Standards.  Environmental Protection Agency, Office of Air
     Programs, Research  Triangle  Park, North Carolina.   Publication
     Number AP-89.  November 1971.

14.  Nature and Control  of Aircraft  Engine Exhaust Emissions.   Northern
     Research and Engineering Corporation.  Final Report to  the National
     Air Pollution Control Administration.  Durham, North Carolina.
     Contract Number CPA 222-68-27.  November 1968.

15.  A Study of Aircraft Gas Turbine Engine Exhaust Emissions.  Aerospace
     Industries Association.  Washington,  D.  C.   August  1971.

16.  Collection and Assessment of Aircraft Emissions Baseline Data -
     Turbo-prop Engines.  Detroit Diesel Allison  Division (CMC).  Avail-
     able from NTIS--PB  202-961.  Contract Number 68-04-0029.   September
     1971.

17.  Exhaust Emissions Test: AiResearch Aircraft  Propulsion  and Auxiliary
     Power  Gas Turbine Engines.   AiResearch Division Garrett Corporation.
     Available from NTIS--PB 204-920.   Contract Number  68-04-0022.
     September 1971.

18.  Assessment of Aircraft Emission Control Technology. Northern
     Research and Engineering Corporation.  Available  from NTIS--PB 204-878,
     Contract Number 68-04-0011.  September 1971.

19.  Collection and Assessment of Aircraft Emissions -  Piston Engines.
     Teledyne Continental  Motors. Available from NTIS--PB 204-196.
     Contract Number 68-04-0035.  October  1971.

20.  Analysis of Aircraft  Exhaust Emission Measurements: Statistics.
     Cornell Aeronautical  Laboratory.   Available  from  NTIS--PB  204-869.
     Contract Number 68-04-0040.  November 1971.

21.  A Study of Aircraft Powerplant  Emissions (Piston  and Turbine).
     Scott  Research Laboratories, Inc. Available from NTIS--PB 207-107.
     Contract Number 68-04-0037.  January  1971.

22.  Collection and Assessment of Aircraft Emissions Baseline Data -
     Turbine Engines. Pratt and  Whitney Aircraft. Available from NTIS--
     PB 207-321.  Contract Number 68-04-0027. February 1972.
                                         98
-------
 23.  A Field Survey of Emissions from Aircraft Turbine Engines.  U. S.
     Bureau of Mines, RI  7634.  Bartlesville Energy Research Center,
     Bartlesville, Oklahoma.

 24.  Gaseous Emissions from  a Limited Sample of Military and Commercial
     Aircraft Turbine Engines.  Southwest Research Institute.  Available
     from NTIS--PB 204-177.  Interim Report, Contract Number EHS 70-108.

 25.  A Study of Exhaust Emissions from Reciprocating Aircraft Power
     Plants.  Scott Research Laboratories.  Available from NTIS--PB 197-627,
     Contract Number CPA  22-69-129.  December 1970.

 26.  Design Criteria for  Control of Nitrogen Oxide Emissions from Air-
     craft Turbine Engines.  Ronald S. Fletcher, Richard D. Siegel, and
     E. Karl Bastress.  Northern Research and Engineering Corporation.
     Report Number 1162-1.

 27.  Time Requirements for Retrofitting Jet Aircraft with Improved
     Combustor Design.  Northern Research and Engineering Corporation.
     Final Report to National Air Pollution Control Administration,
     Durham, North Carolina.  Contract Number CPA 22-69-90.  July 1969.

 28.  Reduction of Nitrogen Oxides from Gas Turbines by Steam Injection.
     N. R. Dibelius, M. B. Hilt, and R. H. Johnson.  ASME Paper 71-67-58,
     American Society of Mechanical Engineers.

 29.  A Study of Exhaust Emissions from Reciprocating Aircraft Power
     Plants.  Scott Research Laboratories, Inc.  Scott Project Number 1136.
     Final Report to the U. S. Environmental Protection Agency.  Research
     Triangle Park, North Carolina.  Contract Number CPA 22-69-129.
     December 1970.

 30.  Profile of Air Pollution Control. County of Los Angeles, Air Pollution
     Control District.  1971.

 31.  Ambient Carbon Monoxide Exposures.  R. I. Larsen and H. W. Burke.
     APCA 69-167, Air Pollution Control Association.  June 1969.

 32.  A Simple Method of Calculating Dispersion for Urban Areas.  Steven R.
     Hanna.  Journal of the Air Pollution Control Association, 2_1(12):774-
     777.  December 1971.
                                         99
OUS GOVERNMENT PRINTING OFFICE 1973 514-151/133 1-3
-------