EPA-AA-SDSB  79-17
                         Technical Report
             Evaluation of HC Control Strategies for
                  General Aviation  Piston Engines
                                by
                         Richard  S. Wileox
                             July  1979
                              NOTICE

Technical Reports do not necessarily represent final EPA decisions
or positions.  They  are  intended  to  present technical analysis of
issues using data which  are currently available.   The  purpose in
the  release of  such reports is to  facilitate  the exchange of
technical information and to inform the public of technical devel-
opments which may form the  basis  for a  final EPA decision, position
or regulatory action.

               Standards  Development and Support Branch
                 Emission Control Technology Division
             Office  of Mobile  Source Air Pollution Control
                  Office  of Air and Waste Management
                 U.S. Environmental Protection Agency

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                                     -1-
I.   INTRODUCTION

     In support of the current final rulemaking action for  aircraft
emission  standards,  the cost  effectiveness  of controlling hydro-
carbon (HC)  exhaust  emissions  from general  aviation piston-powered
aircraft  (PI)  is evaluated.   Houtman (1976)  previously evaluated
the cost effectiveness of controlling this source  for HC  and carbon
monoxide  (CO).   Recent  analyses  by Jordan  (1977)  and FAA (1978)
have  indicated  that these  aircraft  are  not major  contributors  to
violations  of  the  National Ambient  Air Quality  Standard for  CO
which adversely affect the public health  and welfare.

     Although HC emissions  from  general aviation  are also  small
when  compared  to many  other  sources,  the  oxidant  problem  is  so
widespread  that   all  reasonable  controls  should  be  implemented.
Based on  this  premise,  several potentially  cost-effective control
strategies  for these aircraft  are  evaluated  to determine if reduc-
tions  in  HC from general  aviation piston-powered  aircraft are
justified.

II.  DISCUSSION

     A.   Cost Effectiveness

     To determine  the  most cost  efficient means  of meeting and
maintaining  the  National  Ambient  Air Quality Standards  (NAAQS),
potential control  strategies are  evaluated  on the basis of  their
relative cost effectiveness, i.e.,  the monetary cost  of  preventing
one ton of  emissions.   Unfortunately, cost-effectiveness  analyses
have  some associated  uncertainties.   For  example,  the point  at
which a control strategy is not considered to be cost effective has
never been precisely defined.  Also, when future control  strategies
are being evaluated, it  is important to  remember  that as  the most
efficient  controls are  implemented,  each  succeeding control incre-
ment will have  a higher marginal  cost.   Because  of  this  expected
price  increase,  it   is  not  necessarily  correct to make decisions
with regard  to a potential control strategy by comparing  its cost
effectiveness to that of other  past or presently considered strate-
gies.

     These kinds of  limitations prevent cost-effectiveness  analyses
from being  used as  an absolute  decision making   device  in  every
instance.    Cost  effectiveness  is  most  appropriately employed  in
decision making  along with other  information.   It  is  also useful,
however,  as a  screening  mechanism to  eliminate  those  control
strategies  whose cost  effectiveness  is  not within  the range  of
values that  are generally accepted  to be  cost efficient.

     In this analysis,  cost-effectiveness comparisons are used as  a
screening mechanism.   Therefore,  a  decision  will be  made  to further
evaluate HC  emission  controls  for general  aviation piston-powered

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                                 -2-
aircraft, only  if  the cost  effectiveness  of  these controls is
reasonably within  the range  of  values  for  other strategies which
are  currently  being seriously considered.   As  shown in  Table 1,
current cost-effectiveness values range  up to  about $950.

     Most  of  the cost-effectiveness figures  contained  in Table 1
are  based on annual  costs.   Therefore,  to  maintain  the greatest
degree of comparability between those  figures and the figures
derived in this  analysis, the costs  of controlling  exhaust emis-
sions  from general aviation  aircraft  are annualized.   Also,  the
cost-effectiveness  figures  contained in  Table  1,  and  the costs
which  are used  throughout this  study,  are based  on  1978 dollars.

     The  following  formula is used to determine  the cost-effec-
tiveness values for the control concepts which are reviewed  in this
analysis.

                            (C.Rf) + (LtF.Cf)  + M.
     Cost Effectiveness = 	—	
                                    Jr Lt
                                     r t
Where:    C.    =  incremental  cost to the consumer;


          Rf   =  capital recovery factor based on 10% interest per
                 annum and 20  year useful  life;


          L    =  landing and  takeoff cycles (LTO's) per year (250);


          F.    =  increment in fuel consumption in gallons per LTO;


          Cf   =  price  per  gallon  of   aviation  fuel  ($0.97/gal);
          P    = pollutant reduction  per LTO; and


          M.    = annual maintenance increment.
           i

All of the control costs  are attributed to HC since it is the only
pollutant being considered for  regulation in this study.

     B.   Baseline Exhaust Emissions

     The  present  standards  (promulgated  in  1973)  were  directed
predominantly at controlling CO;  therefore, the HC standard was set
by EPA at a  lenient  level to preclude HC-CO  tradeoffs by  some
possible  control  technologies.   A review of  the  baseline (uncon-
trolled)  emissions  from these aircraft  found  that the  fleet-
weighted average emissions were the same as the present standard of

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                               -3-

                             Table 1

         Cost Effectiveness of Strategies for HC Control
                          (1978 Dollars)

                                                  Cost
Control Strategy                             Effectiveness
with Control Increment                           $/Ton

Degreasing 0-40%                                -230 a/
Gravure 0-98%                                    -60 aj
Gas Terminal 0-67%                                 0 aj
Acrylonitrile 0-35%                                0 aj
Polyethylene 0-95%                                 0 aj
Charcoal 0-99%                                     0 aj
Miscellaneous Chemicals 0-35%                      0 aj
Dry Cleaning 0-80%                                10 aj
Industrial Finishing 0-75%                        10 aj
Carbon Black 0-95%                                10 aj
Formaldehyde 0-95%                                20 aj
Refining 0-67%                                    10 aj
Arch. Coatings 0-100%                             20 aj
GHDV Evap. 5.8-0.5 gm/mi                          20 aj b/
Open Burning 0-25%                                20 aj
Ethylene Oxide 0-95%                              20 aj
Acrylonitrile 36-99%                              40 aj
Ethylene Dichloride 0-95%                         40 aj
Paint & Varnish 0-70%                             60 aj
Degreasing 41-90%                                100 aj
Industrial Finishing 76-97%                      110 aj
Gasoline Handling 16-50%                         110 aj
Cyclohexanone 0-95%                              140 aj
Metal Decorating 0-90%                           160 aj
Miscellaneous Chemicals 35-53%                   220 aj
Gasoline Distribution 67-99%                     300 aj
Coke Ovens 0-80%                                 490 aj
LDV Exhaust  0.9-0.41 gm/mi                      530 aj
Foundries 0-60%                                  560 aj
Letterpress & Lithography 0-90%                  790 aj
Gas Handling 51-91%                              780 aj cj
HDV Gas 90% of baseline                          300 d/
HDV Diesel 90% of baseline                       162 d/
LDV I/M                                          955 e/
LOT 1.7-0.8 gm/mi                            139-201 f/
a/   DOT (1976).
b/   A more recent EPA analysis which supports a regulation yet to
     be published as a proposal, yields numbers in the range of $70
     to $250 per ton.
c/   Agrees reasonably well with a more recent EPA analysis.
d/   EPA (1978).
e/   EPA (1979a).
f/   EPA (1979b).

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                                 -4-
0.0019 HC Ibm/ rated power/cycle.  Therefore, the level of control
must be more stringent to effectively  reduce  HC emissions from this
source.

     The  fleet-weighted  baseline exhaust emissions per  LTO  cycle
are shown in Table 2.

     C.   Control  Strategies  Using Fuel Schedule Enleanment

     When  the present  promulgated  standards were  issued,  EPA
identified  fuel  schedule enleanment as  the most practical control
technology  for these  airplane  engines.   As  shown  in Figure 1,  the
fuel-air ratio which is  necessary to meet the CO standard is  below
the  fuel-air  ratio which is  required  to attain the  HC  standard.
Therefore,  by meeting the CO standard, additional reductions  in HC
were achieved.  The most stringent potential HC reduction reviewed
in  the analysis  of fuel enleanment  concepts,  is the  level  of HC
control that would result if the present CO standard was  attained.
(The potential HC reductions attributable to each  of  the control
concepts which are reviewed  in  this analysis  are hereafter referred
to as "the HC reduction criteria.")

     The fleet-weighted  reductions in fuel consumption and gaseous
emissions for the  most   stringent enleanment  HC reduction criteria
are  shown  in Table 3.   Two enleanment concepts  are reviewed:
fuel metering tolerance  reductions and  automatic  fuel scheduling.

     a)   Fuel Metering Tolerance Reduction

     The simplest and least  expensive  control concept  is  to modify
the existing fuel  system so  that  the  fuel-air mixture of each
engine is calibrated at  or near the production lean limit.  Specif-
ically, this modification would result in reducing  the fuel meter-
ing orifice  tolerances  of the  carburetor or fuel injectors.    FAA
recertification of  the  engine  or airframe would not  be  required.
The cost  of this  modification has been  estimated  by one engine
manufacturer to be  $150  to  $200  per engine,  excluding the cost of
engineering  and development  (Avco 1977).   There  is  no maintenance
increment associated with this  hardware.

     For the purposes of  this analysis,  the total incremental cost
of the hardware to  the  consumer  is $200.   It is unlikely that  the
hardware could  be  less  expensive after  amortizing  the  costs  of
engineering  and  development  over the  expected  production  volume;
therefore,  this  is considered  the  "best  case"  control  cost.

     The  fuel  metering  tolerance  reduction  control  technique  is
incapable  of fully attaining the most  stringent potential  HC
reduction which has been identified   (Table  3).   It  is,  however,
capable of a significant  reduction in HC, the level of  which can be

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                                 « R —








                             Table 2





                 Baseline Piston Aircraft  Emissions
Engine HC Emissions
Model (Ibs/bhp per LTD)
IO-320D
IO-360-B
0-320-D
0-200-A
10-5 20-D
Tiara G 285-B
GTSIO-520-K
TSIO-360-C
Weighted Average
0.00120
0.00160
0.00159
0.00220
0.00220
1.00140
0.00140
0.00470

Promulgated Standard
Fraction Weighted
of Fleet HC Emissions
0.055 0.00007
0.159 0.00025
0.121 0.00019
0.285 0.00063
0.129 0.00028
0.141 0.00020
0.072 0.00010
0.036 0.00017
0.00189
0.00190
Source - Data Derived From Deimen (1977).

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                            -7-
                        Table 3






        Fleet Weighted Emission Factors (Ib/LTO)









                    CO       HC      NOx      Fuel






Baseline           15.4      0.32    0.04     0.69






Controlled          8.8      0.21    0.20     0.57






Percent Change    -43%      -34%     +400%    -17%
Source:  Houtman (1977).

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                                 -8-
estimated from information contained in a document prepared by the
Avco Corporation  (Avco  1977).   It  is stated that disregarding the
obvious variation of  the fuel schedules from model  to  model,  the
control technique could  reduce  the  baseline CO  emissions  from the
best  0-320 engine  tested  by 28 percent  (from  the mean engine
setting to the  lean  limit).  As  previously stated, enleanment
reduces CO  and  HC  together;  therefore,  for the  purposes  of  this
simplified analysis, this same proportion of control is  applied to
the baseline fleet-weighted  average  HC emissions.

     As shown in Table  3, a  1.0 percentage  point reduction  in CO
corresponds to a 0.79  percentage  point change in HC (34/43 = 0.79).
Therefore, the  28 percent reduction in  CO is equivalent  to  a 22
percent reduction in baseline HC (28 x 0.79 = 22).  Based on Table
3,  this  would mean a reduction  in HC  of  0.07  Ibm per LTO and  a
reduction in fuel  consumption  of 0.08  Ibm per  LTO.   The  cost
effectiveness is approximately $2,300 per ton of HC reduced.   This
control technique is not reasonably within the range of  costs  that
have been calculated for other mobile and stationary source control
strategies (Table 1).

     b)   Automatic  Fuel Scheduling

     Recent  information  indicates   that  an  engine  power  control
system which  automatically  schedules the  fuel-air ratio may  come
quite  close   to  achieving the  currently  promulgated CO  standard
(Scott 1978).   Developed  by Woodward Governor  Company, Beech
Aircraft  Company, and  Teledyne  Continental Motors,  the  system is
referred  to  as  the  single  lever power  control.   It has been FAA
certified in  a   Beechcraft  Bonanza  airframe equipped with a  Con-
tinental  10-520  engine.   Presently, the  fuel  control is  used  in
conjunction with  a  constant  speed  propeller  and  a continuous  fuel
injection system.   The  unit could  also  be used  on turbocharged
engines  and possibly be adapted  to carbureted  engines  as  well
(Liseon 1978).

     The  power   control  system  automatically regulates  the  fuel
schedule  above  1500  rpm.   During  takeoff,  the  fuel-air ratio  is
leaned to just  slightly rich of "best power."   For  climbout,  the
mixture is  leaned to "best  power," and  for  approach it  is  near
"best  economy."  (The  corresponding  fuel-air  ratios  for these
conditions are  shown  in Figure  1.)   The power  control  unit  also
compensates  for changes  in ambient  conditions and  altitude.

     Industry representatives were  unable to state the actual  cost
of  this unit  to  the consumer.  They did  comment,  however,  in the
context of statements made previously by Helms (1977) regarding the
cost of achieving the current EPA standards.  Scott (1978), Liseon
(1978),  and  Norsworth  (1978) generally agreed  that in  limited
production quantities, i.e.,  500-1000 units, the  cost of  the single

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                                 -9-
lever power  control may  be close to or greater than the $1,500 to
$3,000 as  cited  by  Helms (1977).  If the unit were widely used as
emission control hardware,  there  was agreement  that the price would
be reduced, perhaps  by 33 percent.

     To evaluate the cost effectiveness  of this hardware, the "best
possible"  emission  control  case will  be  examined.    Although  no
emission tests have been conducted  (Wilkinson 1978),  it is assumed
that  because  the power  control unit  might  nearly achieve  the
existing CO  standard,  it will achieve  the  suggested HC reduction
criteria (a 34 percent reduction  from baseline  emissions).  Also it
is assumed that  if  the unit was  widely  used for pollution control,
the incremental  cost  to  the purchaser  of a  new aircraft would be
$1,000  per  engine with no  accompanying  maintenance penalty.

     By using the emission and  fuel  reduction information contained
in Table 3,  the  cost effectiveness is calculated to be over $8,000
per ton  of  HC  reduced.    This  is  significantly greater  than  the
currently  accepted  range of values for other  control strategies
(Table 1).

     D.    Other Control Strategies

     It has  been demonstrated  that  fuel schedule modifications  are
not cost  effective  for  reducing HC  exhaust  emissions alone.    A
variety  of other control techniques  for light  airplane piston
engines have  been evaluated by  NASA  and EPA contractual efforts,
and will now be considered.

     The two previous examples illustrate that the cost effective-
ness of any  HC  control strategy  for this  source is very sensitive
to the total cost of  the system.  Therefore,  in considering  other
control techniques,  a  low cost  will  be the primary concern.   All of
the remaining control techniques  are able to provide  a significant
degree of HC control.

     a)    Air Injection System

     Renzy (1976) has  ranked various control  concepts based on  a
variety of criteria  as  shown  in Table 4.  Air injection ranks  first
as the least expensive, and  since it  is  also known to be very
effective in reducing  HC  emissions from piston engines, it  will be
evaluated for its cost effectiveness.   It  should  also be  pointed
out that air injection was ranked fourth in overall  utility as  a
control concept (Table  5).

    Air  injection exhaust  after  treatment has been well defined as
an automotive emission control device.  It works by  injecting  air
into  the  engine exhaust port which,  as  it mixes  with the  hot
exhaust,  oxidizes  a  portion  of the HC and CO remaining in  the
exhaust stream.   The  additional   air  is typically  supplied by  an
engine-driven air pump.

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                                                  Table 4
                               Concept Rank Ordering Versus Criteria Importance
                                                                    Criteria
















Improved Cooling Combustion Chamber*
Improved Fuel Injection Systems
Air Iniection
Multiple Spark Discharge System*
Ultrasonic Fuel Atomization, Autotronic
Variable Timing Ignition System*
Thermal Fuel Vaporization, Ethyl
Hydrogen Enrichment, JPL
Texaco CCS
2-Stroke Diesel, McCulloch*
Ford Proco
Variable Camshaft Timing
Honda CVCC
4-Stroke Diesel, Open Chamber
Dominant






E
M
I
S
S
I
0
N
S
Q
3
4
14
12
13
11
1
5
7
6
10
2
8









S
A
F
E
T
Y
1
2
5
3
4
6
7
14
8
11
9
13
12
10




P
E
R
F
0
R
M
A
N
C
E
6
1
8
5
9
3
10
7
12
2
13
4
11
14








C
0
0
L
I
N
G
1
14
9
7
11
8
13
4
2
6
3
10
12
5


W
E
I
G
H
T

&

S
I
Z
E
1
2
5
3
5
4
7
8
10
13
11
9
12
14



F
U
E
L

E
C
0
N
0
M
Y
6
5
14
12
10
11
9
1
2
4
3
13
8
7











C
0
S
T
6
7
1
2
4
5
3
12
10
13
9
8
11
14
Secondary




R
E
L
I
A
B
I
L
I
T
Y
3
A
5
6
1
7
2
8
12
9
11
14
13
10





T
E
C
H
N
0
L
0
G
Y
2
1
3
4
5
7
6
9
13
11
14
8
10
12
0 C
P H
E A
R R
A A
T C
I T
0 E
N R
A I
L S
•T
I
C
S
1
6
3
2
5
9
4
12
10
13
11
8
7
14
M a
A n
I d
N
T M
A A
I I
N N
A T
B E
I N
L A
I N
T C
Y E
1
2
5
3
4
6
7
8
13
9
14
10
11
12
Minor




I
N
T
E
G
R
A
T
I
0
N
6
4
2
1
10
3
9
7
11
13
12
5
8
14






M
A
T
E
R
I
A
L
S
3
2
6
1
4
5
7
14
13
12
9
8
10
11


P
R
0
D
U
C
I
B
I
L
I
T
Y
2
7
1
5
4
6
3
8
11
13
12
9
10
14



A
D
A
P
T
A
B
I
L
I
T
Y
4
6
1
2
7
3
5
8
11
14
12
9
10
13
                                                                                                                 o
                                                                                                                 I
* Not considered an HC control concept in this analysis.
Source: Rezy (1976).

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                                  -11-


                                Table 5

                     Concept Ranking for Emissions

              Rank                  	Concept
               1                    Hydrogen Enrichment, JPL

               2                    Honda CVCC

               3                    Improved Fuel Injection Systems

               4                    Air Injection

               5                    Texaco CCS

               6                    Ford Proco

               7                    2-Stroke Diesel, McCulloch a]

               8                    4-Stroke Diesel, Open Chamber

               9                    Improved Cooling Combustion
                                    Chamber aj

              10                    Variable Camshaft Timing

              11                    Thermal Fuel Vaporization,
                                    Ethyl

              12                    Ultrasonic Fuel Atomization,
                                    Autotronic

              13                    Variable Timing System aj

              14                    Multiple Spark Discharge System a/
a/   Not considered an HC control technique in this analysis.

Source: Rezy (1976).

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                                 -12-
     Air  injection  systems were considered to  be  a potential
control technology at the time Federal emission standards for this
source were originally proposed.   Bendix (EPA 1973) evaluated this
concept on a  Continental 0-200 engine  and  concluded  that  it could
meet or exceed the Federal  standard  for HC and CO emissions.  Areas
in which  further  development work was  necessary  were  also identi-
fied.

     Unlike automotive engines,  aircraft piston  engines  use fuel-
air mixtures which are much  richer than stoichiometric over most of
the flight regime.  This means that the exhaust from these engines
contains a large quantity of potential energy  in the form of HC and
CO.   Under  some conditions, if  too much air  is  injected  into the
exhaust, overheating  of  the exhaust manifold could result  in its
failure.  This  problem can be alleviated by  correctly  sizing the
injection air  flow  and installing a  thermal sensor to prevent
overheating.    Under  normal  operating  conditions,  the  added  heat
from  the  exhaust  may  adversely  affect  engine cooling.    This may
require double-wall construction  of the exhaust  system  or a rede-
sign  of  the  engine cooling  shroud.   It  is expected  that  the air
injection pump  will  fit into the  existing  engine  cowling config-
uration, however.

     Specific HC  emission  reduction figures for  this control
concept have  been  reported  by  Bendix (EPA  1973) and  Renzy (1977)
which are based on actual engine  tests.  Bendix (EPA 1973)  tested a
Continental  0-200  engine and  found  that  the  HC emissions  were  67
percent below the  existing  Federal  standard.   It was  also pointed
out that  because  of  the abnormally  long residence  time  of the
exhaust  before  it was  sampled, the HC  reduction was  somewhat
inflated.   Renzy (1976) tested  a Continental 0-200  and applied the
results to  Continental IO-520-D.   For  this  engine,  HC  emissions
were 35 percent below the standard.

     For the  purposes  of this simplified analysis, a  "best case"
condition is considered where injection reduces the fleet-weighted
HC emissions to a  level between the values  reported by Bendix (EPA
1973) and Renzy (1977).  Hence,  the reduction criteria  is assumed
to be 50 percent of the existing  HC Federal standard.   Since it has
already been demonstrated that  the  fleet-weighted  baseline  HC
emissions  are  equivalent  to the  existing Federal  standard  (Table
2), the assumed reduction criteria can be directly applied to these
baseline values.  Therefore, a  reduction  of  0.16  Ibm  of HC per LTO
is used in the cost-effectiveness  formula.

     The literature  which  was  reviewed as  part  of this  analysis
contained  only one  reference to  the  cost of installing  an air
injection  system on an  aircraft  piston engine.   Northern  Research
(1971) reported that  the new engine price  increment would  be $200.
This price may  seem  somewhat high when  current  automotive experi-
ence is considered as a benchmark.  In a document prepared for the

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                                -13-
EPA  (Lindgren 1978),  the price  of  an automotive  air injection
system is $32.

     There  are  several  factors  which would  increase  the  system
price  for a  light  piston aircraft.   These include:   1) higher
pass-through costs  since more corporate entities are involved
(i.e., a minimum of hardware, engine, and airframe manufacturers);
2) FAA certification costs for  the engine and airframe;  3)  develop-
ment  costs for a  larger number  of  engine families;  4)  a lower
economic volume over which  to  amortize nonrecurring expenses;  and
5) added costs due  to additional cooling and over temperature
safety control considerations.  If  the above factors are con-
sidered, a  cost  of $200,  in  1978 dollars,  does not appear to  be
unreasonable.

     Other  costs  will  be  incurred  by this  control technique
throughout its useful life in addition  to the first cost.   Although
automotive air injection  systems do not require maintenance  during
the useful  life  of the car (5 years or 50,000 miles), it is con-
ceivable that  some  direct and indirect maintenance  will  be  required
by the aircraft system because  its useful  life  is much longer  (20
years).  Operating  the  air injection system will also increase fuel
consumption slightly by absorbing a small amount of horsepower from
the engine to drive  the  pump.   Northern  Research  (1971) estimated
that these costs would  average  a total of $30 per  year. This cost
is equivalent  to  about  $45 in 1978 dollars.

     The cost effectiveness of  the air injection system can  now be
calculated by inserting  into the  formula:   (1)  $200 as the  incre-
mental cost to  the consumer,  and  (2)  a yearly  expenditure  of  $45
for added maintenance and increased fuel consumption. This control
concept requires $3,000  to  reduce  one ton of HC;  it is much more
expensive than any cost-effectiveness  value that  has  been  calcu-
lated for other  control  strategies (Table 1).

     E.   Remaining Concepts

     Since air injection  has a very  high  cost-effectiveness value
and it is ranked as the  least costly  control concept (Table  4),  as
well as one of the better HC  emission reduction techniques  (Table
5), all  other potential  control  concepts  can  be eliminated from
further consideration since they will  be  even less  cost effective.

III.  SUMMARY AND  CONCLUSION

     The cost  effectiveness of alternative  strategies for  control-
ling HC exhaust emissions from piston-powered aircraft  ranges from
$2,300 to  $8,000  per ton.   These values were based primarily  on
industry supplied  data.   Although EPA considers  the  cost  infor-
mation to  be  reasonably representative,  the actual  expense  of
pollution control may be somewhat lower  if  a rigorous  independent

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analysis were made.  The  costs,  however,  would  have to be signifi-
cantly  reduced  to  bring  the cost-effectiveness  values  for  these
aircraft within  the range of other  implemented or  planned control
strategies,  A  reduction  of that size seems  unlikely  based on the
information which  is  currently available.   Therefore,  controlling
the HC  emissions  from  piston-powered aircraft is  not considered to
be  cost effective  at  this  time.   In the future, however,  as the
marginal costs  of controlling air  pollution  increase,  this source
may again be considered for control.

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IV.   REFERENCES

     Avco Corporation. 1977.   The Past  Development  and  Future
     Development  of  the Avco Lycoming Aircraft Piston Engines for
     Reductions  in Exhaust Emissions.   Avco Lycoming Williamsport
     Division, Williamsport, Pa.

     Bastress, E.K.,  R.C.  Baker, C.F.  Robertson,  R.D. Siegal, and
     G.E.  Smith.   1971.   Assessment of  Aircraft  Emission Control
     Technology.   Northern  Research  and Engineering Corporation.
     Report No. 1168-1.  EPA Contract No.  68-04-0011.

     Datwyler, W.F., A. Blatter, and S.T.  Hassan.  1973.  Control of
     Emissions from Light  Piston-Engine  Aircraft.   The  Bendix
     Corporation.  EPA Report No. APTD-1521.

     Deimen,  J.M.  1977.   Aircraft  Emissions  at Selected Airports
     1972-1985.   TSR AC77-01.    Emission Control Technology Divis-
     ion,  EPA, Ann Arbor, MI.

     Department of Transporation,  Interagency  Task  Force on Motor
     Vehicle Goals  Beyond  1980.  1976.  Air Quality,  Noise and
     Health.

     Environmental  Protection  Agency. 1978.   Proposed Gaseous
     Emission Regulations  for 1983  and Later Model Year Heavy-Duty
     Engines:   Draft Regulatory Analysis.   Emission Control Tech-
     nology Division, EPA, Ann Arbor, MI.

     	.   1979a.   Cost Effectiveness of Portland I/M
     Program.  Memo from Catherine  O'Rourke to  Janet Becker.
     Emission  Control  Technology  Division, EPA,  Ann  Arbor,  MI.

     	.   1979b.   Gaseous  Emission  Regulations for
     1983  and Later Model Year  Light-Duty  Trucks.   F.R. 44(135):
     40784-40839.

     Federal Aviation Administration.  1978. General Aviation
     emission measurements at Lakeland, Florida.  Memo from Chief,
     High  Altitude Pollution Staff,  FAA,  to Director, Environmental
     Quality.

     Helms,  J.L.  1976.   Summary of the General Aviation Manufac-
     turers'  Position  on Aircraft  Piston  Engine  Emissions.   Pre-
     sented  at  the  1976  Aircraft Piston  Engine  Exhaust Emission
     Symposium,  NASA  Lewis  Research  Center.    NASA CP-2005.

     Houtman, W.H. 1976. Development of EPA Aircraft Piston Engine
     Emission  Standards.   Presented at  the 1976  Aircraft  Piston
     Engine Exhaust Emission Symposium,  NASA Lewis Research Center.
     NASA  CP-2005.

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                                 -16-
IV.   REFERENCES (cont'd)

     	.   1977.   Reevaluation of the Need for Aircraft
     Piston Engine  Emission  Standards.   TSR  AC77-03.    Emission
     Control Technology Division, EPA, Ann Arbor, MI.

     Jordan,  B.  C.  1977.   An Assessment  of  the Potential Air
     Quality Impact of General  Aviation  Emissions.   Office of Air
     Quality Planning and  Standards,  EPA,  Research Triangle Park,
     N.C.

     Lieson,  P.  Woodward Governor Company.    1979.   Telephone
     Communication  with R.  S.  Wilcox,  Emission Control Technology
     Division,  EPA,  Ann Arbor,  MI.

     Norsworthy,  J. Woodward  Governor Company.   1979.   Telephone
     Communication  with R.  S.  Wilcox,  Emission Control Technology
     Division,  EPA,  Ann Arbor,  MI.

     Rezy,  B.   1976.   TMC  Aircraft  Piston Engine Emission Reduction
     Program.   Presented at the 1976 Aircraft Piston Engine Exhaust
     Emission  Symposium, NASA Lewis Research Center.  NASA CP-2005.

     Scott,  0. W.   Beech  Aircraft Corporation.   1979.   Telephone
     communication  with R.  S.  Wilcox,  Emission Control Technology
     Division,  EPA,  Ann Arbor,  MI.

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