A study of the effects of radii of gyration and altitude on aileron effectiveness at high speed

MISSING IMAGE

Material Information

Title:
A study of the effects of radii of gyration and altitude on aileron effectiveness at high speed
Series Title:
NACA WR
Alternate Title:
NACA wartime reports
Physical Description:
7 p., 3 leaves : ill. ; 28 cm.
Language:
English
Creator:
Fehlner, Leo F
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:
Ailerons   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Introduction: Because the time to bank combat aircraft has become increasingly important and because information on the variation in the time to bank with altitude and with weight distribution along the wings is not available, the present theoretical investigation was made to determine the magnitude of these effects. The variation in the necessary aileron control and in the time required to bank to 45° and 90° with altitude and radii of gyration for a typical fighter or a pursuit airplane have been computed and are presented herein.
Bibliography:
Includes bibliographic reference (p. 6).
Statement of Responsibility:
by Leo F. Fehlner.
General Note:
"Originally issued April 1943 as Restricted Bulletin 3D26."
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 - 003805033
oclc - 123904862
System ID:
AA00009439:00001

Full Text
V


RB No. 3D26


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WAllTIM'E REPORT
ORIGINALLY ISSUED
April 1943 as
Restricted Bulletin 3D26

A STUDY OF THE EFFECTS OF RADII OF GYRATIOR AND ALTITUDE
O1 AILERON EFFECTIVENESS AT HIGH SPEED
By Leo F. Fehlner

Langley Memorial Aeronautical Laboratory
Langley Field, Va.


UNIVERSITY OF FLORIDA
DOCUMENTS DEPARTMENT
2-0 IMARSTCN SCIENCE UBRARY
'. BOX 117011
-': L' 32611-7011 USA



NC:i "t


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-
viously 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.
L 249





































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


http://www.archive.org/details/studyofeffectsof001ang









NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS


RESTRICTED BULLETIN


A STUDY OF THE EFFECTS OF RADII OF GYRATION AND. ALTITUDE

Oi AILEROUI EFFECTIVENESS AT HIGH SPEED

B:.' Leo F. Fehlner


I"ITRODUCT :OI


Because the time to bank combat aircraft has become
increasingly imiortart and because information on the
variation in the time to bank with altitude and with
weight distribution along the wing is not available, the
present theoretical investigation -'as made to determine
the magnitude of the-se effects. The variation in the
neceessar;. aileror. control and ijn the time required to
bank to 450 and 900 with altitude and radii of gyration
for a t.'Tpical fighter or a pursuit airplane have been
computed and are rrewented herein.


SY 0BOLS


V true airspeed, miles per hour

Vi indicated airspeed, miles per hour (correct reading
of airspeed indicator calibrated to read true air-
soced at ?ero altitude)

M Mach number

^" longitudinal flight-:iqth anr-'le, degrees

KX ratio of radius of r:;ration about the X axis to span

Kz ratio of radius of gyration about the Z axis to span

t time, seconds

CL rolling-moment coefficient, L

L rolling moment foot pounds












q dynamic pressure pounds per square foot

qo impact pressure, pounds per square foot

SW wing area, square feet

b span, feet


A.IEPLA:E CHARACTERISTICS AID METHOD


The total weight of the airplane considered in the
computations is 9300 pounds; wing loading, 30 pounds per
square foot; aspect ratio, 6; and span, 40 feet. The
ae,r dynamic characteristics were chosen to. be representa-
tive of pur:.it or fighter aircraft in hi,--h-specd flight
just below the critical speed.

The altitude was varied from 0 to 50,00C0 feet under
standard conditions. The ratio of the radius of gyration
about the X axis to the wing span was varied from 0.06 to
0.16 and the ratio of the radius of g ration about the Z
axia to the wing span was varied from 0.14 to ).22. This
rEr.-e of radii-of-gyration ratios covers the complete
r.nn^ge of all the values known for 42 existing con.vention-
al pursuit and fighter aircraft. The motions of the air-
plane were studied in vertical dive, high-speed glide,
level flight, and climb attitudes at constant Iach num-
ber, constant true airspeed, and constant indicated air-
steed.

The lateral motions were computed for the cases
given in table I.

The ir.,.act pressure for the various cordition2 mf
fli<-t are given in table II.

The lateral motions of the airplane wnre determined
by solving the differential einations of motion in a
manner similar to, that used in reference 1. In the pre.-
ent report the ailerons were assumed to be deflected in
such a way as to increase uniformly the rolling-.oment
coefficient applied to the airplane during -Lhe first one-
tenth second and to hold it constant thereafter.













RESULTS AND DISCUSSION


The results are presented in figures 1 to -3.

Figure 1 includes three types of variation with alti-
tude: one variation at constant true airspeed, another at
constant L'ach number, an.'. a third at constant indicated
airspeed. Cases for constant true airspeed and constant
Mach number are chosen to be identical at 20,000 feet and
cases for constant indi--,ted air-r'ped and constant Hach
number arp chosen to be identical at 50,000 feet.

Figure 1l.a) show- the variation with altitude of the
rolling-moment coe fi cient that must be ap--lied by aile-
ron? to perform t.wo banz:ir. -' maneuvers; namely, the at tain-
ment of an an-le of ban;: of 450 at the an-d of the first
half second ,ind 0 at the end of the fir t second.

Fie:u'.re 1(b) -how- *.e varia+ io'., with altitude of the
time to ban': to 1'' and 'C0. The roil 1 in -moment coef-
fiient a lied at all alti'.udes are those thnt produce
an angle of banrk of 45 at a ne end of the fi;r t half
second :-nd of c 0o at t'he end or th}e first second at zero
alt i tude.

The rollinr-:-_ir.mernt coefficient neces ar-- to bank to
45 in one-nalf second i? greater than that neces.;ary to
bank to '0o ir 1 second. Tnis difference in required
rolling-m.omen coefficient i= due to trhe f ct that the
airplane acc-lerate= in roll during all or a large part
of the time interval considered. The n ent of inertia
in roll tr.erefore ha- an im,;,ortant influence on very short
rolling; maneuver=. The rolling-. moment coefficient re-
quired to bank to any other anrile in the sa.Te time is
directly. proportional to the angle; that is to bank- to
450 in I second requires half the rollinF-mcment coef-
ficient necessar-" to bank to 900 in 1 second.

The decrease in. re'-uired rollirn -mor ent coefficient
shown for increa- i- n altitude w'it:. indicated airsoeed con-
stant is cqai ed by the large increase in true airspeed
that i re-uired to maintain a gi',en indicated girpreed.
(See table I. The rolli n--moment coefficient necessary
to bank the airplane i n a given ti e is r, ct a function of
v P 1ocit alone, how ever, a is Ih own by the variation of
rolling-momnnt coeffi irnt with --iltitule wnen true air-
speed is constant (fig. ).












At a Mach number of 0.75 and also at a true airspeed
of 530 miles per hour, a greater rolling-momerjt coeffi-
cient is required to bank thp airplane to 900 in 1 second
at hir-h altitudes than at low altitudes. At a Vach number
of 0.75 the increase in rolling-moment coefficient re-
quired in chan-ing from 20,000 to 40,COO feet is about 40
percent for tho airplane considered.

If the hinge moment is assumed to be proportional to
the rolling moment, a relative hinge moment may be com-
put-d by multirlyine the rolling-moment coefficients of
figure 1 by the corresponding impact Iressures presented
in table II. These relative hinge moments are presented
in figure 2 in a manner similar to that used for the roll-
ing-LLoment coefficients oF fig'ire 1.

The factor of proportionality between the rolling
moment and the hirac:e moment depend- on the aerodynamic
characteristics of the particular airplane. The variation
ef stick force with hinge moment varied with linkage and
booster system,. The coIrutaticr of the variation of
stick force with altituie from the hir.F-e-inoment variation
requires a knowledge of The variation in stick force with
hin.e moment for a particular case.

The hinge moments applied in fi-.ure 2(b) qre those
that produce an angle of bank of 450 Pt the end cf the
first half second and 0O at the end of the first second
at zero altitude.

The hinge moment r.ecessar" to bark to 450 and 900 in
the stated time intervals io girentl:,' decreased 1h- in-
creases in altitude. For the 90") maneuver at a Mach num-
ber of 0.75 the hinge moment is 44 percent less at 40,000
feet than at 2',0000 feet.

The time to bank to 90 arid 450 gr'eaPtly decreases as
altitude increases if the hine r.omiEnt i.g held constant
at all altitudes. The decrea3s in tht time to bank to
i0 .is 3% percent for a cainrgCe in altitude from 20,000 to
40,000 feet.

AlthD-t'h figure 2(b) does show the variation of the
time to bank to eiven ?anl PF with altitude for various
constant hingCe moLents, the corres:.onding rolling-moment
coefficients required at high altitude exceed those ob-
tainable with present designs. The decrease in the time
to bank to a given an4le as shown in figure 2(b) is there-
fore limited by the maximlum rolling-moment coefficient
available.













From figures 1 and 2, it is concluded that if the
strength of the pilot limits the aileron deflection, as
is usually the case for present high-speed airplanes, the
aileron effectiv"eness increase with altitude. At a
given limiting IYach number, the increase in effectiveness
results largely from tht larger deflections produce by,' a
given force applied to the stick and the increase in ef-
fectiveness will cortinup cnly to the altitude at which
the maximum design deflection of the aileron is reached.
Above this altitude the aileron effectiveness will de-
crease. The aileron system, therefore, should be de-
signed for roll i ng-noment re.-ui rementis at high altitude
and the hinge-moment limitpt ionr. at low altitude.

Figure 3 includes variationr.s of the radius of gyra-
tion about the X axi- of the airrl-ne inr a glide and in
level flight at 530 miles per hour and at an altitude of
20,000 feet. The rndii -of ;.rat ion of airi lanes of widely
different cla; ifications fall within the-- ran.-e of radii
of g.ratior, consid.- red. -.hese czlazsifizations include all
conv ren tional sir. -, c- and t .-,in-er.gine pursuit and fighter
air-lene .-c ith 1-'ide variations an wei.rt distribution
along tne r'inge.

Figure 3(?) show. the vari-,ti r -'.ith the radius of
gyration about the X axi s of the rollir.g-aToient coeffi-
cient necessary, to a tai.i an angle of bar. of 4,.O at the
end of the first half spco-.d and of '-2 st the end of the
first sec-nd.

Figure 3(b) shows t'-ie vari tion of the time to bank
to 450 and c0O with the radiis of .:'"ratio n about the X
axis. The rolii n -mov.ent coefficient.s appliei for all
values of the r-.dius of gyrstion are those that produce
an ani-le of banr: of qt thr end of the first half
second and of '3'C at the end of the first second with the
ratio of radiu- cf ,yvratior, about t h1 X a-ris to the span
er'u.al to c ..>?.

The effect of changes i- the radius of gyration in
roll on the rollir..--.omer.t coefficient nezeesary to bank
to 90 in 1 record is larce bec-aue of the large percent-
age of the maneuver spent in acc.-eleratine: the airplane in
roll. The roll g-moer.ent re. ii rrn ent s are in-creased
about 2. percent b:,- incre-isina'r the radius of gyration
about the X axis from O.OS t- 0.16.












The effect on the banking maneuvers considered of
variations in the radius of gy.ration about the Z axis are
negli .ible.

The longitudinal flight path was varied from a ver-
tical dive to a 13.90 climb at F'30 miles per hour and at
20,000 feet. The effects on the banking -:aneuver of var-
iations in longitudinal flight iath angle are negligible
in the range investigated.

For all the assumed co.nditiocr of 'light, the angle
of sideslip resulting from a rolling-momert coefficient
of 0.05 deviates in an oscillator' mr-nner during the first
2 seconds and does not exceed ar. anrLle of the order of 20.



Largley Memorial Aeroanutical Laboratory,
National Advisory Corm:ittee fir Aeronautics,
Langley Field, Va.



RYiERE~TCE


1. Fehlner, Leo F;. A Stud;: of tne Effects of Vertical
Tail Area and Dihedral on the Lateral Maneuvera-
bility of an Airplane. 1ACA A.R.R., Oct. 1941.












TALE I

CASES FOR WHICH{ LATERAL MO0TIOUS WERE COMPUTED


Case M Altitude KA, 1 C
e <(.mph) .mplh) (ft ) (,leg) I
1 0O.V50 7?0 T5" 0 -."0." 2 "125 j15 0 .06
2 .750 53-0 400 20,0,0> -1 .9 .1 5F .175 .088
3 .750 496 25 40,000 1 .125 .175 .224
4 .750 4-6 2'04 0,0 3 -4.4 .1 5 .175 .365

5 .C96 550 520 0 -27.0 .125, .175 .043
S .300 53C 2' 40,00- 125 .175 .l'1
S ._300[ 30 220 750,03 -4. .1]5 .175 .n3 0

8 .269 2204 204 I 0 -4. 125 175 .325
9> '-4 4 0 4" 20,00' -4.7 .125 .175 .329
10 .50? C 204 4 -4.5 125 .175 550

11 C l 530 400 20, 000 -13. 2 .0 .140 .C0 8
12 ?. 5:0 400 i 20 ,00 -1 .U''- 220 .0 8
13 .750 530' 4,0.' 2,0, :0 ': -13.C 1.:. .22'0 .0689

14 .750 5?0 400 20,000 ', Cl 1 '5 .175 .01l
15 .750 530 400 20,00: 0 .0 :0 .140 .0 1
16 .75C 530 400 C 0,00 0 .0.30 20 .091
17 .7?50 530 400 20,0:'0 '' .110 .220 .0:1

1s .750 50 400 20,000 1 .9 .125 .15 .088
19 .F0 530 400 20,000 -.90.0 .125 .175 0



TABLE II

VARIATIO'T OF IMPACT PRESSURE W',ITH ALTITUDE



Altitude '___
S i' = 0..750 V = 53 r.mph Vi = 204 mr.h
I 1


0

40, 000
50 00


.*50.0
436.5
17 0
1 0 J. 1


.;05 .
433.5
203. 9
126.5


109.1
10'. 1
10 1
109.1









NACA Fig. I

N N N -





SaI

S\ I




C 0
/.


> l I o
^-_--- -7^---- -----









co
SI I






,\ Q / \ I




..C 0
0 L
g al

N 0




- t__- -___ _-- 1.


CO N \o o o) V cv o
0 0 0 0 6-0<
'0 r !J.U11 .; H 20 J.LUai O WLI- Ll'i/O^J







NACAo = 0 ) Fig. 2



c ci ,c/ i /

----r-^-4--
4z


/ '


---------------------------------------------------- -H ------^ -


/ 4 /
~ / I~ s


-1 / A 0
0






E
-------- --






,,... "K ra

-KE















nac
V.40

~ -
t \ UI' o w













-* -/ -- 1





a:u/ -- --- LZy/L-- -\-L--- \








NACA


.49 q-


____ c:Z~i



~ ~


I


i -4 f ----- I F-


0


1 S

o o
a'




0
0

o
0




0'






0 E
.4-




0





a : if
-.4 0







I























MO@
F-
S.



0


OS O
S -C


0
U^ 41 c

B CJ

t::. BE

o-! a. 0 > -


a *< 2404
ot F. I j



o *
0 0JQ .
.-.. F-
OC 04
5..14


Fig. 3


o pa0,2.;'ao0 pJau.ioj- 6&'U.lol


IL


I









f

I
:













t








!*
I
i
I
:
r
i







i;,




UNIVERSITY OF FLORIDA

31262 8 4601
i



UNIVERSITY OF FLORIDA
DOCUMENTS DEPARTMENT
1 20 MARSTON SCIENCE LIBRARY
F'. BOX 117011
S-ThESVILLE, FL 32611-7011 USA