The effect of lateral area on the lateral stability and control characteristics of an airplane as determined by tests of...

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Material Information

Title:
The effect of lateral area on the lateral stability and control characteristics of an airplane as determined by tests of a model in the Langley free-flight tunnel
Alternate Title:
NACA wartime reports
Physical Description:
13, 8 p. : ill. ; 28 cm.
Language:
English
Creator:
Drake, Hubert M
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Yawing (Aerodynamics)   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: The effects of large variations of lateral area on the lateral stability and control characteristics of a free-flying model when ailerons are used as the principal control have been determined by flight tests in the Langley free-flight tunnel.
Bibliography:
Includes bibliographic references (p. 12).
Statement of Responsibility:
Hubert M. Drake.
General Note:
"Report no. L-103."
General Note:
"Originally issued February 1946 as Advance Restricted Report L5L05."
General Note:
"Report date February 1046."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003614166
oclc - 71248173
sobekcm - AA00006241_00001
System ID:
AA00006241:00001

Full Text

'AIc


ARR No. L5L05


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS


WA RTIME RE PORT
ORIGINALLY ISSUED
February 1946 as
Advance Restricted Report L5L05

THE EFFECT OF LATERAL AREA ON THE LATERAL STABILITY
AND CONTROL CHARACTERISTICS OF AN AIRPLANE
AS JETERMlIED BY TESTS OF A MOEL IN
THE LANCLEY FREE-FLIGBT TURNEL
By Hubert M. Drake

Langley Memorial Aeronautical Laboratory
Langley Field, Va.


NACX


WASHINGTON
NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of
advance research results to an authorized group requiring them for the war effort. They were pre-
Sviously held under a security status but are now unclassified. Some of these reports were not tech-
nically edited. All have been reproduced without change in order to expedite general distribution.
4i


L 103


L..


V


tjl 'c-' TS DEPr









II? at~ 173 i


INACA ARPR h-. L5L05


RESTRICTED


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS


ADVANCE RESTRICTED REPORT


TVE E'FEC'T OF LATERAL AREA ON THE LATERAL STABILITY

"2D CONTROL CHARACTERISTICS OF AN AIPPLANE

AS DETER INED BY TESTS OF A MODEL IN

T' LANGLEY FREE-FLIGHT TUN'CL

By Hubert M. Drake


SUMMARY


The effects of large variations of lateral area on
the lateral stability and control characteristics of a
free-flyirzi m-odel when ailerons are used as the principal
control have been determined by flight tests in the
LanL.ley free-flipht tunnel. The effects of the lateral-
force parameter C,, (rate of change of lateral-force
I-
coefficient with angle of sideslip) were investigated
for a wide range of values of the directional-stability
parameter Cn (rate of change of yawing-moment coeffi-


client vith angle o
yaw Dara":eter Cnr
"r


f sideslip) and the rotary-damping-in-
(rate of change of yawing-moment coef-


ficient with ya:wing angular velocity).


Although large values of Cy. were found to increase

the lateral stability, a definitely undesirable effect
'as obtained with large values of this parameter when
ailerons were used to raise a low wing or to make a
banked turn. "'th large amounts of lateral area the
adverse yav acsco' pianying aileron rolls created adverse
si:-e f'3r3eE of sufficient magnitude to interfere with
the sileron control. This action was particularly objec-
tionable for lov values of Cn and Cnr. It is indi-
cated t-hat decreasing C will improve the over-all
lateral flight behavior.


RESTRI CTED




































Digitized by the Internet Archive
in 2011 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://www.archive.org/details/effectoflaterala001ang










NACA ARR No. L5L05 3

Cy lateral-force coefficient Lateralo force

S wing area, square feet

b wing span, feet

q dynamic pressure, pounds per square foot :-pV
V2 /
V airspeed, feet per second

p mass density of air, slugs per cubic foot
p angle of sideslip, degrees

Single of yaw, deCrees (for force-test data, V= -p)

L rolling moment, about X-axis

N yawing moment, about Z-axis

M pitching moment, about Y-axis

6r rudder deflection

6e elevator deflection

a angle of attack

T1/2 time for oscillation to damp to one-half amplitude

P period of lateral oscillation, seconds

kX radius of gyration about X-axis, feet

ky radius of gyration about Y-axis, feet

pb/2V helix angle generated by wing tip in roll, radians

p rolling angular velocity, radisns per second
r yawing angular velocity, radians per second









NACA ARR No. L5L05


7, rate of change of rollingl-.nioment coefficient with
P angle of sideslip, per degree C6 P)

S directional-stability parameter, that is, rate of
n achar.-e in yacwlIn-moment coefficient with angle
of sideslip, per degree (6Cn/6

Cnr rotary-.,'armping-in-Iaw parameter, that is, rate of
r change of yawa.ng-Toment coefficient with ya,'ing

angular velocity, ner radisn ~n/'6bl

Cy lateral-force parameta-e, that is, rate of change
P of lateral-force coefficient with angle of side-
9sli, oer dr'.r.? k(6C0/6I


APP ARATUS


The invest .,a' on was conducted in the Langley free-
fli-ht tunnel, a cnomrlete description of which is given
in reference 2. A photogreni of the test section of the
tunnel with the model in flight is given as figure 2.
Force tests to determine the static stability character-
istics of the model were made on the free-flight-tur.nel
six-component balance (described in reference 5), which
measures moments and forces about the stability axes.

T'r, free-oscillation method emoloyed in reference 4
was used to determine experimentally the -values of the
rotar--famping-in-yaw parameter Cn These values were
derived from damAing measurements of the model mounted
on a strut that .srmitted freedom in ya..

A three-view sketch of the model used in the tests
is shown as figure 3 and a photograph of the model is
shown as figure li.. The test model was so designed that
vertical tails of different size (fig. 5). could be
mount-; at various locations r-lonp the fuselage, both
ahec3 of and behir. the center of ;.rsvity. Ten vertical
tails wer-e rTed during the tests. Eiht of these tails,
two each of tails 1 to L (fig. 3), were Peometrically
similar. 01 the other two t-ils, one was extremely large
(tail 5) and the other was of low aspect ratio (tpil 6).








IACA ARR N-. LSLO5 5


A !hotoraph of the model with tail 5 in place is pre-
sented as figure 5. The dimensional and mass character-
istics of the model used in the tests are given in table I.


TESTS

Test Conditions


The flight tests of the model were made for a wide
range of values of the lateral-force parameter Cy
over a range of values of the directional-stability
oarameter C, and the rotary-damping-in-yaw parameter 0r.
Changes in these oarameters were obtained by various
c~ibinations of vertical-surface area and tail lengths
so that the lateral-force narameter could be varied while
the directional-stability and rotary-damping-in-yaw
oararreters were held constant. The dihedral was zero
for ,'ost of the tests.

The rane of test conditions covered in the investi-
gatior, is. sho'rr. in figure 6 in the form of slope values
obtained fro-ri: the force tests and the free-oscillation
tests of the various configurations. For most of the
tests, h.e values of Cy,n Cn and Cnr were varied,
respectively, from -O.OOlL to -0.0201, from -0.00000
to 0.00260, and from -0.011 to -0.158. The ratio between
-rn and n Cn vas held at a convenient normal value of
about 60:1 for most tests, but no attempt was made to
maintain an exactly constant value of this ratio. In
addition, the model was tested with two configurations
having a very high value of Cy (-0.0600) for two
large values of Cn and n For some tests the
vertical tail was removed and the minimum value of Cn
r
occurred in this condition rather than at the negative
value of Cp because, in order to obtain negative COn,
a vertical tail had to be added ahead of the center
of gravity.

Flight tests were arbitrarily made at a lift coef-
ficient of 0.5 for each of the conditions represented by
the test points shown in figure 6. In order to determine
the effect of lift coefficient, some tests were also made








NACA ARR No. L5L05


at a lift coefficient of 1.0. Flights were made for each
test arr-ingeenter by use of ailerons alone or rudder
coordinated with ailerons for control.

The total aileron deflection used in the tests was
300. This deflection gave a value of pb/2V of about
0.07 as measured in rolls from level flight with rudder
fixed. For most of the tests the ailerons were riEged
up 100 in order to minimize the adverse aileron .::i'.wg.

Flight tests were made at approximately 00 effective
dihedral angle as indicated by force tests. The vertical
tails were added above or below the fuselage in order to
maintain the effective dihedral angle as near 0 as
possible. One exception was the test with tail 5, which
rave approximately 24 effective dihedral -nile.

Throughout the tests, the mass characteristics were
maintained constant at the values given in table I.


Flight Patir.-i s

The model was flown at each of the test conditions
represented by the parameter values in figure 6. Graduated
ratings on stability, control, and general flight char-
acteristics were assigned each test condition fro:.: pilot's
observations of the model in flight. The stability and
control ratings used were as follows:


I- ----- -------------i
Rating Stability or control

A Good
B Fair
C Poor
D Veryi -oor
E Divergk' t
__...._____ 1I~_______________


Plus or minus rati.LTs were assigned to indicate slight
but perceptible changes in the rating. iMotion-picture
records of some flights were made to permit more careful
study of the flight behavior and thereby to aid observers
in misL..;_; more accurate flight rating.









ITACA ARR No. L5L05


The stability rating of a free-flying model in a
stable condition is generally deter-rined in the free-
flight tunnel from the steadiness of flight in the rather.
gusty air of the tunnel. A very stable model returns to
its original flight path more rapidly after receiving a
gust disturbance and generally does not tend to move as
far from its original flight path as one with less stability.
Greater stability is thus indicated by greater steadiness.
For unstable conditions, however, the stability is judged
from the rate at which the model deviates from straight
and level flight and from the frequency of control appli-
cation required to maintain steady flight.

The control rating is determined from the ease with
which straight and level flight is maintained and from
the response of the model to control applications designed
to perform maneuvers. Any unnatural lag or motion in the
wrong direction is judged as poor control.

The general flight ratings are based on the over-all
flying characteristics of the model. The ratings indicate
the ease with which the model can be flown, both for straight
and level flight ?nd for performance of the mild maneuvers
possible in the Lsn~ley free-flight tunnel. Any abnormal
characteristics of the model are generally judged as poor
general flight behavior, inasmuch as they are disconcerting
to the free-flight-tunnel pilots.


RESULTS AND DISCUSSION


The results of the investigation are summarized in
figure 7, which presents pilot's ratings for the stability,
control, and general flight characteristics. The sta-
bility and control ratings are substituted for the test
point values of figure 6 and are therefore representative
of various configurations. It should be remembered that
these results were obtained at a dihedral angle of 0
(Ct = 0), except for tail 5, and are strictly true only
for this dihedral angle; however, the qualitative effects
of Cy are believed to be unaffected by dihedral. The
general effects of dihedral have been reported in refer-
ences 5 and 6.









FACA ARR No. L5LQ5


Effect of Cy, on Stability

The stability ratings of figure 7 show that increasing
Cv while maintaining Cp and Cr constant slightly
increased the stability. The results of stability calcu-
lations, made by the method of reference 7, are presented
in figure 8. The lateral-force parameter is given as a
function of the period of the lateral oscillation (P) and
as a function of the time required for the oscillation to
damp to one-half amplitude (T1/2). The results shown in
figure 6 show the same trend noted in the results of
figure 7. The increase in stability with increased Cy
is greatest for the smallest values of On and Cnrp
The calculations also show that Cv has very little

effect on the period of the lateral oscillation.


Effect of Cy on Control by Use of Ailerons

The results of figure 7 show that increasing Cy
generally decreased the ease with which the model could
be controlled with ailerons alone or rudder coordinated
with ailerons. The deterioration in control was much
greater for the low values of Cn, and Cnr than for
the large values of these derivatives. The reduction in
control with increased Cyv is explained as follows:
"rhen the m1cc,,el received a gust disturbance in yaw causing
it to sideslio, the pilot gave corrective aileron control
to bring the model back on course. As a result of this
control application, the model rolled but the large side
force opposed the lateral component of lift that tended
to bring the model back to its original location in the
tunnel. The return to the original flight path was thus
abnormally slow. As Cy and, hence, the opposing side
force was increased, the aileron control became less
effective in restoring the model to its or'rinal lateral
position in the tunnel. For another case, if the model
was in straight level flight and the pilot a-D-lied aileron
control to perform a maneuver, the adverse yawing caused
by the aileron deflection and rolling introduced









NACA A'R No. L5L05


a side force in such a direction as to o-oose the side
force produced by the angle of bank. This effect caused
the model to hesitate or move first in the wrong direc-
tion and was therefore considered undesirable.


Effect of Cy on General Flight Charocreristics

The pilot's ratings for general flight character-
istics are presented in figure 7 together with those for
stability and control. These ratings are shown by the
separated regions of figure 7(b) and indicate that the
pilot pref-rred the ease of control obtained with low
values of Cy, to the slight increase in stability
resulting from increased Cy. Obviously, the ideal
configuration would be one that was both very stable and
easily controlled. If low stability characteristics
necessitated a cor.oro-ise, the pilot's rating indicated
a preference for ease of control rather than a slight
increase in stability. The tests showed that the quanti-
tative effect of varying Cy was dependent upon the
accomnanying values of Cnp and Cnr

Large values of Cn and Cn .- At extremely large
values of n and Cn, such as are shown in the flying-
bomb region in figure 6, all flights were given an excel-
lent rating by the pilot despite the fact that two of the
configurat-ins tested had extremely Ifrge values of Cy
For conditions in this region, the large amount of
directional stability limited to small values the side-
slip -ing due to adverse aileron yaw. As a result, the side
force created by the large values of Cy was not large
enou.,'- to affect the ailero-n control a).reciably.

!-oderate values of C, and Cn.- 'hen Cn and Cnr
were reduced to values corresponding to those of the
ordinary conventional airplane, large variations of Cy
appreciably affected the control of the model. For values
of Cn corresponding to a conventional airplane with a
rather large tail Cnp = 0.00200), increasing Cyp from









NACA ARR T;i. L5LO5


small to large values caused a corresponding reduction in
general flight ratings frDm excellent to good. With
smaller values of Cn, and Cn (Cn = O.00140) in the
conventional-airplane range the change in flight character-
istics with large increases in Cy was more pronounced
(excellent to fair).

Small values of 0n and Cnr.- Flights made in the
tailless-csirplane region (P- = O.O0014 to 0.00080) were
satisfactory only for the smallest values of -, .
Increasing Cy to larger values in this region resulted
in very poor flight behavior.

Flights made at the lowest value of Cn
Cn = 0.00014) in the tailless region, although very
controllable (control rating, A-) were given a general
flight rating of only fair. This rating was given because,
although the model was stable in this configuration, it
had a long-period large-amplitude yawing oscillation that
was objectionable to the pilot. The model flew very
steadily, however, because of the long period of the
oscillation. This flight behavior has been previously
reported for other tailless designs (model and full scale)
and was similarly objectionable both to free-flight-tunnel
and airplane pilots. Increasing Cnp to a value of 0.00080
reduced the yawing oscillation to a great extent and
resulted in satisfactory flights.

The model was directionally divergent in flights
made with a negative value of Cnp for values of C0

equal to -0.0030 and -0.0105 and thus could not be
given a control rating, but was however given a general
flight rating of very poor. The directional divergence
at both values of Cy was very slow and the pilot felt
that the divergence could have been prevented with
independent rudder control had this control been available.
In any case, the condition would have been given a general
flight rating of very poor because of the unnatural control
required.









NACA ARR No. L5LO5


Effect of lift coefficlent.- Fli.i,:ts made at a lift
coefficient of 1.0 showed a negligible change in flight
behavior fror corresponding flights made at a lift coef-
ficient of 0.5 and consequently no d-:,ta are presented for
these tests.


CO.'CLTUDluG PEI'APF S


Tn tests, nade in the LarTley free-flight tunnel,
in which ailerons were used as the princinal o control, it
was found that, although large values of the lateral-force
paraneter CCy (rate of chan-e of lateral-force coeffi-

cient with angle of sideslip) increased the lateral sta-
bility, a definitely. undesirable effect was o3'tained then
ailerons *were used to raise a lo;'-r wi'i or to rna'ke a
banked turn. This -efiect was oiar.ti ularly objectionable
for small v..lues of the directional-stability paraneter Cn
(rate of change cf -7av.ng-oemnent coefficient with angle
of sideslip) ard the rotary-damping-in-yaw parameter C
nr
(rate of change ol ya'ring-momrn nL coeffi.ient with yawing
angular velocity;. For s'.ch conditions the adverse yaw
accompanying aileron deflection created adverse side
forces sufficient to interfere with the aileron control.
The over-all flight behavior of the model wa..s considered
best with srrall values of C .

For any- value of C., the over-all flight character-
istics were improved b3 incraas.ng Cn and ri
nr
Tncreasina Cn and Cnr was rr st effective at the smallest
values of Cy .

Little change in the fli ':t zhar:scteristics w.a
caused. by a change in lift coefficii-nt from 3.5 to 1.0.

Langley Meemorial Aeronautical Laboratory
National Advisor- Cor.-mittee for Aeronoutics
Langley F'el., Va.








NACA ARR No. L5LO5


REFERENCES

1. Bamber, '. J. Effect of Chan-es in Asotct Ratio,
Side Area, Flight-Path Angle, and normall Accelera-
tion on Lateral Stability. FACA ARR,Dec. 1942.

2. .hortal, Joseph A., and Osterhout, Clayton J.: Pre-
liminary Stability and Control Tests in the NACA
Free-Flight '"ind Tunnel and Correlation with Full-
Scale Flight Tests. NACA TI; No. 810, 1941.

3. Shortal, Joseph A., and Draper, John *?.: Free-Flight-
Tunnel Investigation of the Effect of the Fuselage
Length and the Aspect Ratio and Size of the Vertical
Tail on Lateral Stability and Control. NACA ARR
No. 3D17, 1935.

4. Car-nbell, John P., and .-F;thews, Ward 0.: Experimental
Determination of the Yawing Moment Due to Yawing
Contributed by the 'ing, Fuselage, and Vertical
Tail of a ..idwing Airolane :odel. NACA ARR ['o. 5F28,
19435.

5. Camnbell, John P., and Seacord, Charles L., Jr.: The
Effect of :.ass Distribution on the Lateral Stability
and Control Characteristics of an Airplane as
Determined by Tests of a "odel in the Free-Flight
Tunnel. YACA ARR No. 35H1, 1945.

6. Campbell, John P., and Seacord, Charles L., Jr.: Effect
of 'in:-, Loading and Altitude on Lateral Stability
and Control Characteristics of an Airplane as Deter-
mined by Tests of a :odel in the Free- light Tunnel.
'.3A ARP No. 5F25, 1945.

7. Zimmerman, Charles H.: An Analysis of Lateral Stability
in Power-Off Flight with -harts for Use in Design.
NACA Fep. Ho. 589, 1957.










NACA ARR To. L5L05


TABLE I

MASS AND DTMET-SIONAL CHARACTERISTICS OF THE '.ODEL


5.05


". rng:
Area, sq ft . .
Span, ft . .
Aspect ratio .
M.A.C., ft . .
Sweepback of 50-percent-chord line,
Dihedral, deg . .
Ta-er ratio (ratio of tip chord to
Root chord, ft .
Tip chord, ft . .
Loading, Ib per sq ft .


deg
Sroot
root
* .

. .


* .
. .
* .
. .
. .
* *
chord)
. .
. .
* .


. 2.67
6.0

S0.70
S. 0

050
. 0.90

S1.89


Radii of gyration:
kX, ft .
kz, ft .. ..


Ailerons:
Type .. .
Area, percent S .
Span, percent b .


. . 0.625
. . 0.844


Plain
7
. 4.6.2


* S *


NATIONAL ADVISORY
CO' ITTEE FOR AERONAUTICS


'"eight, lb . .









Fig. 1


NACA ARR No. L5L05


Wind
direction


'c9~


wind
direction

z NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS

figure /.- System of /sAbility axes. Arrows
Indiccoe positive direchons of moments, Forces,
arxi control- surface def/ectons.




ii







NACA ARR No. L5L05


Figure 2.- Test section of Langley free-flight tunnel
with model in flight. Cy$ = -0.0160; Cn, = 0.00080;
Cn -0.064; CL = 0.5.


Fig. 2




ii'
9:








NACA ARR No. L5L05


Tail
I
2
3
4
Supper
S powerr
6


U I NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS

F/lure 3 Three -view sketch of mode/ used
in /alera/-force inves//ga//on. Al/ d/mens/ons
in n1hc S.


Fig. 3










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Ir
































































































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NACA ARR No. L5LO5 Fig. 4




















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o

(-.









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Oq bD






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0
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be
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NACA ARR No. L5L05


Figure 5.- Side view of model used in lateral-force
investigation in Langley free-flight tunnel showing
tail 5 mounted on model.


Fig. 5















































































































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t







NACA ARR No. L5LO5


-.660-- .0


.0







Qb
















-.150-
1 30- -'









-i.-
0 a







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-J./ --

-.664--
-.02-"
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-.24--


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0 4 -- - -


yj


n n Ordin/ry conven iona/-
Sca/rp/an region
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0 NATIONAL ADVISORY
(- I COMMITTEE FOR AERONAUTICS
i.0L1Ii


O -.0/


-.02 -03 -.04 -.OS -.06 -.07
Laera/-fErc paranmefer, Cy


Figure 6.- Range of vo/ues of n C and Cy
covered in /aferal -force i/n eig'n n' ne 4
Langley free -f//gh/ funne/ nd range of values fr
different types of aircraft. C = 0.,5.


Fig. 6


Oz










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NACA ARR No. L5L05 Fig. 7



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Nio
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NACA ARR No. L5L05


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NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS
0 -C04- -.C08 -.0/2 -D0/6 -.0
LaeraoJ-force polDneter, Cyp


Figure 8.- Cal/oL/laed
oscl//atoon of the
force /nvest/gahon
Anrle/. C = O.J.


c/corac/er/3//cs of /he /aferal
model used in the /faeral -
in the ZLcryley /fe -f7/gh/


Fig. 8














































































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