An approximate determination of the power required to move control surfaces as related to control-booster design

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Title:
An approximate determination of the power required to move control surfaces as related to control-booster design
Alternate Title:
NACA wartime reports
Physical Description:
11, 5 p. : ill. ; 28 cm.
Language:
English
Creator:
Johnson, Harold I
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:
Fighter planes   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: As a part of a general investigation of control boosters, preliminary calculations were made to indicate the sizes of control boosters necessary to move the controls of airplanes of various sizes. The analysis was based on the assumption that the controls were moved with a rapidity and amplitude equal to that measured with a fight airplane in simulated combat. A corollary purpose consisted in determining the effect on reducing booster-power unit size of incorporating an energy accumulator in the booster system.
Statement of Responsibility:
by Harold I. Johnson.
General Note:
"Report no. L-102."
General Note:
"Originally issued September 1945 as Restricted Bulletin L5F27."
General Note:
"Report date September 1945."
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

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University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003614183
oclc - 71249216
sobekcm - AA00006262_00001
System ID:
AA00006262:00001

Full Text
,


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS




WAlRTIME RIIPORT
ORIGINALLY ISSUED
September 1945 as
Restricted Bulletin L5F27

AN APPROXIMATE IETERMInATION OF THE POWER REQUIRED TO MOVE
CONTROL SURFACES AS RELATED TO CONTROL-BOOSTER DESIGN
By Harold I. Johnson

Langley Memorial Aeronautical Laboratory
Langley Field, Va.








NACA


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


L 102


DOCUMENTS C ['" ''


IAr


RB No. L5F27




































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/approximatedeter001ang







:.K"A RB No. L5F27

NATIONAL ADVISORY CCOMM'.ITTEE ['OR AERONAUTICS


RESTRICTED BULLETIN


Al APROC"IMATE DETER URINATION OF THE PC','?E RECUTIh-D TO ",'VE

COiT-'I TL SURACES S RELATED TO CONTTROL-B.COSTER DESTI37

By Harold I. Johnson


SU hMMARY


As a rcrt of a general investigation of control
boosters pr-. 11mi ncr: calculations were made to indicate
the sizes of control boosters necessary to move the con-
trols of airnolnes of various sizes. The analysis was
based on the assumption that the controls were moved
.vich rerpidity and amnolitude equal to that measured with
a fighter airplane in simulated combat. A corollary
purpose consisted in determining the effect on reducing
booster-nr.oer unit size of incorporating an energy
-ccuTmulator in the booster system.

The analysis indicates that up to 15 times as large
a rower unit wculd be required for supplying sudden
bursts of w.?er if no accumulated energy were available
as com;rared to a po.-_'er unit capable of supplying the
a'vF.ra- povd-?r uZed in continuous maneuvering in combi-
nstion '.ith i relitiv-ely small energy accumulator.
Results of the calculations show that to operate all the
controls of a Eiiall fighter-type airplane, a power source
of 0.057 h-,orsepo.er in combination with an accumulator
caoeble of storing 51.4 foot-pounds of energy would be
.*uficiently lar.ze if friction and booster cycle losses
arie nalecte.d. In this case, the accumulator would be
required to sup,:.ly bursts of power in amounts up to
0.162 horsepower for e..tremely short periods of operation.
The o.r:c.'-_ '-equireients and booster sizes increase rapidly
w'iLh eirl.ne size. Under the assumptions of the analysis,
a pciVe-- sciurce of 2.05 horsepower in combination with an
acc.umul: tcr capable of storing 5350 foot-pounds of energy
w'Dould be required to operate all the controls of a bomber
w.eihing shout 70,700 pounds. In this case, the peak-
powver dem'.and required from the accumulator would approxi-
mate 20' horsepower. Some of the -roblems involved in
-redicting the booster requirements are discussed in
relation to the assumptions that were made in the









2 IIACA RB No. L5F27


preliminary evaluation. It is concluded that extensive
flight tests are required to determine the effects of
speed, size, and airplane functional type on the booster
requirements.

TI'TRODUCTION


A general investi-A.tion of control boosters is being
conducted at the Langl' Laboratory of the NACA in an
effort to provide some of the information needed for
their design. T'h.e investigation is divided into the
following four ?'f-ses:

(1) St'-d c- flight tests and hinge-mnornent data to
determine the seed with which the controls are usually .
moved and the power required of a booster system to move
them ,ith the desired rapidity.

(2) Analysis of bocster systems in use or in the
design stsae.

(5) Wind-tunnel and ground tests of the more
promising booster systems.

(14) Flight tests of airplanes equir:ed with booster
controls.

This paper is a contribution to the first -hese of
the general investigation.


SYITBOL


AE increment of energy require to drive controls

Hg hi-za moment on control surface at be'inninT of
incremental-control motion Cur-in which con-
trol is moved at constant rate

HE hinge moment on control surface at end of
incremental-control me Lion diiring which control
is mov.-d at constant retd

A6 increment of control-surface deflection in control
motion durin- which control is moved at con-
stant rate










NAC A RB Fc. L'F27 5


6-1p control deflection fror; trim at :- itrz.in.. of
incremental-control movement

6rRE control deflection from trim at end of incrementl-
control movement

6-.- -.av.re control deflection from trim for
incremental-control movement

i6 sil'-'on deflection from trim

62 rne.- y factor, degrees2

2., sil-:..-on energy factor, degrees2

r2/t t .-,.'r factor, degrees2 per second

t ti ,, seconds
(dCh\
T

\~di tct-I rate of change of hiie--moment coefficient
T with control-surface deflection, per degree
includes effect of rate of change of hinge-
mo:aent coefficient with change in angle of
attack)
dirh
-- r&r.e of change of hinge-moment coefficient with
change in control-surface angle, per degree
dC.
-- r-te of ch en of h:1-.: -moment coefficient with
change in angle of attack, per degree

3 c.:rontrol,-surface area back of h-ine center line,
square feet

rc oc.t-mean-square chord of control surface back
of hin.ge center line, feet

qc i:..:-ct pressure, pounds per square foot

rate of change of elevator -, l with change in
edt angle of attack at the horizontal tail

.a, incr.-eental ch-;n7- in tol--: aileron angle (sum of
u;-oirn. and don.rn.ccing aileron movements)









NACA RB No. L5F27


LTH'D OF ANALYSIS AND CETEPAL REjULTS


Thr.:e essential elements are used in a normal ccntrol-
booster system: (1) the power unit, which supplies energy
to the booster system; (2) the accumulator, which stores
up a certain quantity of energy that is instantly avail-
able on demand; and. (5) the booster unit, which takes
energy either from the power unit or accumulator and drives
the control surface. The function of the accumulator is
to take care of short-period demands for great amounts
of power. The purpose of the accumulator is to reduce
materially the necess.ry size of the power-input unit.
The present problem consists in finding the relation
between the sizes of the power unit and accumulator that
.ll always satisfy the ene:.,_.y demands involved in mowing
the controls of an airplane having sny given physical
dimensions. T?-e results obtained should be applicable
to any type of control-booster system, whether hydrauli-
cally, electrically, ,mechanicelly, or air driven.

An analysis was made by selecting an actual vari-
ation of airplane control motion with time and assuming
that this variation is -.p liable to the general case for
Lu.rm~.c-.es of computing control energy and power require-
ments. From a considerable quantity of records available
for a hii'hly maneuverable fighter airplane in simulated
combat, approximately 25 seconds of typically violent
maneuvering were selected. Figure 1 is a reproduction
of the selected time history of airplane and control
motion.

If it is assumed that hinge-mo,-ient variations with
control deflection are linear and aerodynamic damping of
the controls is neglected, a plot may be constructed
from the data in figure 1 of the time variation of some
quantity that is proportional to the energy used in
deflecting the controls. Under the preceding assumptions,
the energy required to deflect the control surface through
a given angle may be determined as the averi.Ze of the
hinge moments acting on the s.irface at the be~rinninr and
end of the motion multiplied by the chn.c in control-
surface sngle; that is,
HB + HE
A-' A6
2









HA" A R3 No. L5F27


Since the hinge moment is proportional to the control-
surface angle, the energy will be proportional to the
average of the control-surface angles at the beginning
and end of the motion multiplied by the change in control-
surface ?n-le, or

5TRB + 6TRE
AE cc 2 A6 = 6TR &6
2 av

Figure 2 gives the results obtained by summing up the
incremental-energy quantities required to drive the
aileron control in the maneuver of figure 1. The energy
-2
hs-. be.-n expressed in terms of an energy factor 62
which represents the summation of average control deflec-
tion from trim times incremental control deflection over
which the rate of control motion was approximately
con.st -nt:
t
Q2 = 8 A6
/ 5TRav
0

The time history was broken into increments during which
the -rete of control motion was approximately constant in
order to determine the variation of the control power
input with time. The variation during the maneuver of
control power input with time affects the balance between
po,:.er unit and accumulator sizes. Inasmuch as energy to
move rhie controls is required only when the control is
nove.I away from trim, the numerous flat spots in the curve
re.r~-ent conditions where the controls were either fixed
or .L'ere returning toward trim. The energy factor plotted
in figure 2 may be converted into energy in units of foot-
pounds by use of the relation

Work = 2 S- (1)
57-3 c

Values of K to be used in equation (1) are the
total hinge-moment-coefficient variation for the control
surface, 'which includes the variation of hinge-moment
coefficient with angle of attack. Thus, the response
characteristics of any particular airplane to which the
iselict.d variation of control motion is applied are
accounted for in the equation.










NACA RB Do. L5F27


Figure 2 and sir:11.'r plots for the other two controls
were used directly to establish general relations between
the power input required and the accumulator capacity
necessary to supply every energy demand of the controls.
Under the assumption that energy is supplied to the
accumulator at a given rate whenever its energy content
falls below its rated capacity, a simole trial and error
graphical solution was employed to determine the desired
relation. This solution consisted in finding, for
various assumed ener.-r capacities, the line with the
smallest slope (smallest power-input rating) that would
provide an energy-available curve which would just meet
the energy-required curve at the most critical time.
One such trial and error solution for an accumulator
cesp city factor of 200 de-_reus2 is shown in figure 2.
Note that the slo"e 52/t so determined is a direct
measure of a minimum rower-input factor which, in combi-
nation with the assumed energy capacity, will satisfy
the energy d-r.en.s of the control throughout the entire
25-second maneuver. Just as in the case of energy,' the
power factor may be converted into power in foot-pounds
per second by use of equation (l)-with the power
factor 52/t in place of the energy factor 62.

82 K
Power t 57-5 Scqc (2)

Results showing the balance between power input and
accumulator capacity required for performing 25-second
periods of violent maneuvering at widely spaced intervals
are given in figure 3 for all three controls. Attention
is directed to the horizontal line labelled "Indefinite
maneuvers" in this figure. This line defines the average
rate at which, by far, most of the energy required to
move the controls was used and is therefore representative
of the minimum power input required for indefinite maneu-
vering. A determination of this value for the aileron
control is given by the slope of the dashed line in fig-
ure 2. Figure 5 shows the isolated maximum power values
plotted for accumulator capacities of zero. These points
were determined from figure 2 and other similar plots by
measuring, the greatest rate of energy output required to
drive the controls at any time during the selected
maneuver.

The data of figure 3 indicate that up to 15 times
as large a power unit would have to be provided if no
accumulator were used as compared to the rinimumn power-









.'AA RB Kc. L5"27


unit rating required for indefinite maneuvering in
cor', nation with a relatively small accumulator. In
t:-is connection, it is believed that a combination con-
siFring of an extremely small power '-.nit and a very lai.,
accum'.ulator would not be considered since this combination
wouldul d be satisfactory only for limited-duration maneuvers
c--u,.iring at widely separated times. Probably the best
all-around combination would be one in which the power
unic is the smallest required for indefinite maneuvering
to-ether with an accumulator of moderate size.


APPLICATION TO SPECIFIC AIRPLA-TES AND DISCUSSION


In order to gain some idea of the sizes of power
units and accumulators necessary to.supply 100 percent of
the energy required to move the controls of airplanes of
various sizes with a rapidity equal to that attained with
the fighter airplane used in the selected maneuver, the
data of figure 5 and equation (1) have been applied with
a:..._'rooriate dimensions to four airplanes covering the
rn'e of size of present interest. These calculations
e:--e made for the minimum-size booster combinations
re.-_.ired for continuous maneuvering. Several assuL:itions
s:-.ly to the results, which are shown in table I, as
follows:

(1) All control surfaces are assumed to have no
aerodyna..-ic balance. This awssution leads to .p:;roxi-
I6Ch -6Ch
:aSt. values of --- of -0.010 per degree and of -
of -0.003 per degree for surfaces of usual dimensions.

(2) All airplanes are assumed to have a degree of
d6e
stick-fixed longitudinal stability such that -- = 1.0.
dat
This assumption leads to a value of K for the elevator
of 0.007 per degree.

(5) All maneuvers are accomplished with zero sideslip
angle. This assumption results in a value of K for the
rudier of 0.010 per degree.

(4) The effect of chcrn-e in angle of attack over the
ailerons on aileron L:inge moments during rolling is neg-
lectel. This assumption results in a value of K for the
aileron3 of 0.010 per degree.









NTACA RB3 No. L5F27


(5) The indicated sirspeed is constant at 175 miles
per hour. This condition was very neErly the case in
the selected maneuver of the fighter airlane.

(6) All transfers of energy in the control-booster
system are accom--lished at 100-percent efficiency for
purposes of this analysis.

Some of the foregoinr assumptions are related
directly to certain basic control-booster considerations,
some of which are discussed in the following para3rphs.

In practice some aerc5.nr.ic balance would probably
be used on control surfaces as a means of reducing the
size and weight of the booster. In these cases, the
booster requirements would be expected to very inversely
with the degree of aerodynamic balance employed (as
expressed by the factor K in equation (1)); however,
the power required to overcome control-system inertia
in order to obtain the desired quickness of response
will probably determine the minimuia size of booster that
can be used when the controls are closely balanced aero-
dynamically. _o account was taken of control-system
inertia in the illustrative calculations, the results
of which are given in table I.

Although the illustrative calculations for booster
size were made for only one speed, the booster power
required is undoubtedly dependent on the speed of flight.
Consider, for instance, the control-power requirements
for a fighter airplane in a particularly violent type
of evasive maneuver. Assume that a pilot rolls an air-
plane from 900 bank in one direction to 900 bank in the
other direction by use of full aileron control and s f-
ficient rudder deflection to maintain zero sideslip at
all times; assume also that the elevator control is used
to produce the pilots' limit load factor when the air-
plane is banked 900 and 1g normal acceleration at the
instant the airplane passes through laterally level flight.
Finally, assume che maneuver is repeated continuously
(without pause when the plane reaches 900 bank in either
direction). Under these conditions, the power necessary
to move the ailerons should vary appro.:imsrtely as the
cube of the indicated airspeed, that necessary to move
the rudder as the first power of the indicated airspeed,
and that necessary to move the elevator as the inverse
of the indicetod airsp ed (at constant altitude). This
analysis nse-lects, of course, the possible adverse effects










NACA :,r. T.5P27 9


of covirressibility on the control forces of airplanes
flown in the critical-s,.eed re ion. Althoi.-h the use of
a booster might considerably alleviate control problems
at extreme speeds, no at-.-r.nt to analyze quantitatively
the requirements of a booster system in this regard seems
possible until more complete data on the aerodynamic
effects are available.

The effect of airplane size, as related to the rate
of response to control deflection, must also be con-
sidered in any accurate an-lr'cis of booster requirements.
For iur,.oses of the illustrative calculations, all the
airplanes were assumed to be subjected to the same vari-
ation in control motion with time. The shortco:..in., of
this assumption can be shown by a simple analysis. For
exa.:*le, sup ..o- a very large airplane, such as air-
plane D of table I, were to perform the evasion maneuver
su posted above. If the rolln: effectiveness of the
ailerons were the same (in terms of wing-tip helix n7.le
produced by full aileron deflection) as for the fighter
indicated in table I (airplane A),the frequency of control
motions for the large airplane would be reduced to about
one-tenth the frequency of the control motions for the
fighter because the length of time to roll to 900 would
vary :.'oroximately as the ratio of the wing spans. The
relative control power required would be reduced the same
amount due to the slower response of the -Lr'Ter airplane.
Obviously, then, it is not logical to assume that control-
power requirements for airplanes of all sizes and types
can be determined from any specific variation of control
motion with time, or for that matter, from any specific
type of spatial maneuver; for, whereas fighter airplanes
encounter most violent maneuver-n. conditions in combat,
ver-: lz ;,- airplanes may encounter most violent maneuvering
conditions while fly.ln through gusty air.

The precs.linr, considerations serve to outline some
of the major factors affecting booster requirements that
could not be handled at the present time due to scarcity
of c, ;:rooriate flight data. It appears that extensive
flight tests of various types of airplanes must be carried
out if an accurate predetermination of the control-booster
requirements of any projected design is to be made. Such
tests would best be conducted with structurally sound
airplanes equi:.-..ed with overly 1:rs control boosters in
order that the desired d-.gree of maneuverability could
always be achieved.










JACVA RB No. L5F27


From the foregoing discussion the results obtained
fr.c:n the illustrative calculations for booster sizes
(see table I) apparently cannot be regarded as accurate
quantitative results. For the larger airplanes, particu-
larly airplanes C and D, the estimates are liable to be
in considerable error.


CO:NCLU DING R3A"2 7"3


An analysis of booster requirements presented has
served to provide rough estimates of the sizes of boosters
necessary for the continuous rapid maneuverin, of air-
planes of various sizes. Because a specific variation
of control motion with time, taken from data obtained
with a fighter airnlsne in mock combat, was applied to
airplanes of different sizes and functional types, the
results obtained sre to be regarded as only rough indi-
cations of t.K- power requirements. A further limitation
of the calculations is that the variation in required
control-booster power with speed of flight could not be
taken into account although a theoretical analysis indi-
cates speed of flight is one of the primrr"r determinrnts
of the required control-booster size. For a more accurate
determination of control-booster- requirements it appears
that extensive flight tests must be made for airplanes
of different sizes and functional ty.. s in crder to
determine the maneuver:zr.;- conditions that are most
critical with re:-,rdd to the power required to operate
controls.


Langle',y '~irorial Aeronautical Laboratory
Thtional Advisory Committee for Aeronnutics
L--n.ley Field, Va.


































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NACA RB No. L5F27


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RB No. L5F27


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fighter airplane In simulated combat.







NACA RB No. L5F27


|U
V-
I


Record of energy available
fobr example of minimum
Satisfactory booster system
_(Accumulator capacity = ZoO de
kPower-unit raqhng= 16 degq'/.


0 5 10 15
Time, 5ec


Figure 2.- Time record of the growth in energy factor required to move aileron control
during maneuver shown in figure 1, assuming linear variation of aileron hinge
moment with deflection from trim.


Fig. 2








NACA RB No. L5F27


800 IMax.

8Ocyf-Mo \


/ w/


1*


600 -\



500 -



400


0 I definite
300 maneuvers








Inter maitent
Z5-sec maneuvers

r\ ___ _____ ______________


80 11o IO 0X0
Accumulator capacity
factor, degz
(a) Total aileron control. -


440 480
NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


Figure 3.- Relation between accumulator capacity factor and
power-input factor required to move controls during violent
maneuvers as determined from records of a fighter airplane
in simulated combat.


I I I t -t


320


Fig. 3a







NACA RB No. L5F27


CL


4OC

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3OO
J00



250




200



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S'O





o Intermittent
S-secr maneuvers /

0 1------- I -------


so


/00


150


200


Accumulator capacity
factor, deg
(b) Rudder control.
Figure 3.- Continued.


Z50 300
NATIONAL ADVISORY
CONNITTEE FOR AERONAUTICS


Fig. 3b







NACA RB No. L5F27


9- Max.-


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700



600










500 \0
300



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maneuvers

/00

rIntermittent t_---0
2~5-Vec maneuvers
n -


0 40


/ZO 100 O0
Accumulator capacity
Pac tor, deg9
(c) Elevator control.


Z40 _890 --
NATIONAL ADVISORY
cONNITTEE Foe AEMIIUTICS


Figure 3.- Concluded.


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. .






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