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(NASA CR O R TMX O R AD NUMBER) A (CATEGORY1
NATIONAL ADVISORY COMMITTEE I
FOR AERONAUTICS
I LOW-SPEED INVESTIGATION OF THE EFFECT OF S M A L L CAI'?ARD SURFACES ON THE DlREGTIONAL S"TILITY OF A SWEPEWCK-WING FIGmER-AIRPLANE MODE& By John W. Paulson and Peter C. Boisseau SUMMARY A low-speed investigation has been made i n t h e Langley free-flight tunnel t o determine the e f f e c t of small canard surfaces on the direc- t i o n a l s t a b i l i t y of a fighter-airplane model having an aspect r a t i o of 3.4 and a 42O sweptback w i n g . The canard surfaces were found t o be generally ineffective a t angles of attack below 20°. For higher angles
of attack, small canard surfaces (4?. by 27 inches, f'ull scale reduced
2 )
t h e d i r e c t i o n a l i n s t a b i l i t y of the model a t l o w angles of s i d e s l i p ( p < 5') but provided no improvement a t higher angles of sideslip.
These canard surfaces had v i r t u a l l y no'effect on t h e longitudinal
characteristics. /
INTEIODUCTION Recent t e s t s of a sweptbgck-wing fighter-airplane m o d e l i n the Langley 20-foot free-spinning tunnel (ref. 1) showed that t h e spin recov- ery c h a r a c t e r i s t i c s w e r e improved through t h e use of canard surfaces, some of which represented open e l e c t r i c a l access doors. Additional tests on a catapult f a c i l i t y showed t h a t the canard surfaces, when located a t c e r t a i n positions, S l s o had a favorable e f f e c t on the direc- tional stability charncterjstics of the model a t high argles of attack.
Since the canasd surfaces used i n t h e t e s t s of reference 1 were r a t h e r l a r g e and probably caused undesirably l a r g e reductions i n longi- tudinal s t a b i l i t y , force t e s t s were made i n the Langley free-flight tun- n e l of a generally similar model w i t h smaller, lower-aspect-ratio sur- faces t o see i f such surfaces might s t i l l produce t h e favorable d i r e c t i o n a l s t a b i l i t y e f f e c t s without the detrimental longitudinal e f f e c t s . Surfaces such as these might be small enough t o be permanently e i n s t a l l e d o n a wing.
i n s t a l l e d on t h e nose of the The tests were made as part o f e n investieation being conducted by the Langley free-flight tunnel section to determine the dynamic stability and control characteristics of a general research airplane model similar Tests were made with the simulated access to current fighter designs.
v doors and with the various sizes and shapes of canard surfaces located at different longitudinal and vertical positions on the forward part of the fuselage. For comparison purposes, tests were made with large canard surfaces which were assumed to simulate open electrical access doors.
SYMBOLS The data are referred, in all cases, to the stability system of axes shown in figure 1 . The coefficients are based on the dimensions of the wing plan form which neglect the chord-extension. The center of gravity was located at 2 8 . 7 percent of the mean aerodynamic chord.
b wing span, ft CD drag coefficient, Drag/qS lift coefficient, Lift/qS cL rolling-moment coefficient, %/qSb c 2 Cm pitching-moment coefficient, %/qSE
yawing-moment coefficient, Mz/ qsb
cn lateral-force coefficient, Fy/qS
-
C mean aerodynamic chord, ft .
0 0 0 0 0 0 0 0 0 0 0 0 0 0.0 0 0 0 . 0 0 0 0 . 0 0 0
* NACA RM L56nga : : :' : : 0 0 0 0. 0 0
8 0 0 0 - - 0 0 * FD drag force, lb * FL lift force, lb FY lateral force, lb
MX rolling moment, ft-lb
pitching moment, f't-lb
Mi
yawing moment, ft-lb
MZ
9 dynamic pressure, lb/sq ft S area, sq ft
v airspeed, ft/sec
.
a angle of attack of fiselage reference line, deg P angle of sideslip, deg * P air density, slugs/cu ft
@ angle of roll, deg
$ angle of yaw, deg Subscripts: v t vertical tail W wing APPARATUS AND MODEL The model was tested in the Langley free-flight tunnel, which is a low-speed tunnel with a 12-foot octagoml test section. A sting-type support system and an internally mounted three-component strain-gage balance were used.
A three-view drawing of the model used in the investigation is pre- sented in figure 2, and the dimensional characteristics are given in table I. Presented in table I1 are sketches showing the canard surfaces tested.
TESTS Force tests were made in order that the effect of the various canard surfaces on the lateral stability characteristics of the model up to an angle of attack of 5 0 ' could be studied. The exploratory runs were gen- erally made over a sideslip range of *lo0, and then some of the more promising configurations were tested over a range of t2Oo with vertical tail off and on. The tests were made with all controls set at a deflec- tion of Oo, with a wing incidence of -lo, and with an incidence of Oo of the canard surfaces.
All tests were run at a dynamic pressure of 4 . 3 pounds per square foot which corresponds to an airspeed of approximately 61 feet per second at standard sea-level conditions and to a test Reynolds number of 511,000 based on the mean aerodynamic chord of 1.309 feet.
RESULTS AND DISCUSSION Lateral Stability Characteristics Basic model and model with access doors extended.- The variation of the coefficients Cy, Cn, and C2 with sideslip angle for various angles of attack is shown in figures 3 and 4 for the basic model and for the model with access doors extended, respectively. The data for the model with vertical tail off (fig. 3 ( a ) ) show that the model was directionally unstable throughout the angle-of-attack range. The yawing-moment coeffi- cient varied linearly with the angle of sideslip and indicated about the same degree of directional instability f o r the model at all angles of attack except at 50°, where the model was less unstable at small angles of sideslip than it was at the higher angles. With the vertical tail on (fig. 3(b)), the model was directionally stable for moderate angles of sideslip up to an angle of attack of about 17' or 18O, and the vari- ation of with the angle of sideslip was nonlinear for most angles Cn of attack. The data of figure 4 show that the extended access doors resulted in the model's being directionally stable for small angles of sideslip at angles of attack above 25O with vertical tail off or on.
At the larger sideslip angles, however, the model was still directionally unstable. Since the access doors improved the directional stability of the model with vertical tail off or on, their effect was apparently 0 0 0 0 0 0 0 0 0 0 0 0 0 eo0 0 0 0 0 0 0 achieved by changing the flow over the fuselage and the w i n g . A direct comparison of some uf the data of figures 3 and 4 is made i n figure 5.
This figure shows that there i s virtually no effect of the access doors on the directional s t a b i l i t y of the madel a t an angle of attack of 20' but that there is a large stabilizing effect a t small angles of sideslip for an angle of attack of 30'. A further comparison of the data of figures 3 and 4 i s made i n figure 6 where the variation with angle of attack of the s t a b i l i t y derivatives and C as measured a t m i - 28' ous sideslip angles, are presented. These data show that the access doors had the greatest effect on the directional s t a b i l i t y a t angles of
aktack above 20° and at l o w angles of sideslip. These results are i n
f a i r agreement w i t h those presented i n reference 1.
Effect of canard size and shape.- Since the preliminmy force tests showed t h a t the extended access doors produced some favorable effects on the directional s t a b i l i t y characteristics, additional tests were made with canard surfaces of different sizes (see table 11) i n an effort t o find a small canard surface that would produce essentially the sane char- a c t e r i s t i c s as the access doors. Presented i n figure 7 are the data from these t e s t s compared with those f o r the basic model and for the access doors extended. The data show t h a t none of the canards had any signifi- cant effect on the directional stability a t an angle of attack of 2 0 ° .
A t an angle of attack of 3 0 ° , however, stabilizing effects cornarable t o those of the access doors were obtained a t small angles of sideslip f o r canard surfaces as s m a l l as 1/2 by 3 inches.
Effect of canard position and size.- I n order t o determine the effect of canard position on the d i r e c t i o n a l s t a b i l i t y characteristics, force tests were made i n which canard surfaces of different sizes were located a t various positions on the flrselage as shown i n table 11. Tine t e s t s w e r e made a t angles of attack of 2 0 ° and 30°, and the data are summarized i n figure 8. "he data again show that, a t an angle of attack of 20°, none of the canard positions o r sizes had any significant effect on t h e directional s t a b i l i t y characteristics. A t an angle of attack of 30°, however, stabilizing effects were obtained a t a number of posi- tions, 7, 8, or 13.
and the greatest effects occurred a t positions 1, 2, The most favorable position appemedto be position 2, and data obtained from t e s t s made t o determine the variation of the l a t e r a l coefficients m e r a_ si&eslip X F ~ P nf W O O for the 1/2- by 3-inch canard surface a t t h i s position are presenteq i n figure 9.
Comparison of access door and 1/2- by 3-inch canard effects.- Sum- m i z e d i n figure 10 are the l a t e r a l s t a b i l i t y derivatives CY,, %$' and C measured at angles of sideslip of f5O and f20° for the basic
%
model, f o r the model with the access doors, and f o r the model w i t h the 1/2- by 3-inch canard surfaces. The figure shows that the canard surfaces were generally ineffective at angles of attack below 200. For higher angles of attack, both the access doors and the 1/2- by 3-inch canard surfaces reduced the direc$ional instability of the model at low angles of sideslip ( p < 50) but provided.lLttle or no improvement at * I higher angles of sideslip. The variation of the effective dihedral parameter C with angle of attack was generally similar for all cases 2P except the access doors at sideslip angles of +5O.
Longitudinal Characteristics A compar.ison is made in figure 11 of the longitudinal characteristics of the model in its basic configuration, with access doors extended, and with the 1/2- by 3-inch canard surfaces. The data show that the access doors contributed a small lift increment near the stall but reduced the longitudinal stability over the entire angle-of-attack range. The small canard surface, however, did not have any significant effect on the longitudinal characteristics.
CONCLUDING REMARKS I I A low-speed investigation conducted in the Langley free-flight tun- nel to determine the effect of small canard surfaces on the directional stability of a fighter-airplane model showed that these surfaces were generally ineffective at angles of attack below 20°. For higher angles
of attack, small canard surfaces ( 4 ' by 2 7 inches, full scale) reduced
the directional instability of the model at low angles of sideslip ( p < 5 O ) but provided no improvement at higher angles of sideslip. The canard surfaces also had virtually no effect on the longitudinal characteristics.
Langley Aeronautical Laboratory, National Advisory Committee for Aeronautics, Langley Field, Va., June 5, 1956.
REFERENCE c 1. KLinar, Walter J . : A Study by Means of a Dynamic-Model Investigation of the Use of Canard Surfaces as an Aid in Recovering From Spins and A s a Means for Preventing Directional Divergence Beax the Stall. MACA RM ~ 5 6 ~ 2 3 , 1956.
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........................
... . . . . .
0 .
.....
. .. . 0 : 0 . : . . . ’ .
8 NACA RM L56Flga ....... ..... .....
L TABU I.- DIMIQJSIONALCHARACTERISTICS OF M O D E L TESTED IN TUNGLEY FRm-FLIGRT TUNNEL Wing :
A i r f o i l section a t root . . . . . . . . . . . . . . . . NACA 6 5 ~ 0 0 6
A i r f o i l section a t t i p . . . . . . . . . . . . . . . . NACA 6 5 ~ 0 0 5
Area. s q f t . . . . . . . . . . . . . . . . . . . . . . 4.63
span. f t . . . . . . . . . . . . . . . . . . . . . . .
3-96 Aspect r a t i o . . . . . . . . . . . . . . . . . . . . .
3.39 Root chord (on fuselage reference l i n e ) . f t . . . . . .
1.87 Tip chord (without chord-extension) . f t . . . . . . . .
0.462 T i p chord (with chord-extension) . f t . . . . . . . . .
0.518 Mean aerodynamic chord. F. f t . . . . . . . . . . . . .
1.306
Sweep of quaster-chord line. deg . . . . . . . . . ’ . . 42
Dihedral. deg . . . . . . . . . . . . . . . . . . . . .
-5
Taper r a t i o (without chord-extension) . . . . . . . . . 0.247
Incidence. deg . . . . . . . . . . . . . . . . . . . . -1
Horizontal t a i l :
. . . . . . . . . . . NACA 6 5 ~ 0 0 6
Airfoil section a t root . . . . .
. . . . . . . . . . . NACA 65A004
Airfoil section a t t i p . . . . .
. . . . . . . . . . . 1.154
Area ( t o t a l ) . sq f t . . . . . . .
Span. f t . . . . . . . . . . . . . . . . . . . . . . . 2.01
Root chord (on fuselage reference l i n e ) . f t . . . . . . 1.00
Tip chord. f t . . . . . . . . . . . . . . . . . . . . . 0.148
Sweep of quarter-chord line. deg . . . . . . . . . . .
Dihedral. deg . . . . . . . . . . . . . . . . . . . . . 5.42
Aspect r a t i o . . . . . . . . . . . . . . . . . . . . .
3-50
Taper r a t i o . . . . . . . . . . . . . . . . . . . . . . 0.148
Vertical t a i l :
Airfoil section a t root . . . . . . . . . . . . . . . . NACA 6 5 ~ 0 0 6
Airfoil section a t t i p . . . . . . . . . . . . . . . . NACA 65AO04
A r e a (including 0.0926 sq f t of exposed dorsal f i n ) .
1.0 s q f $ . . . . . . . . . . . . . . . . . . . . . . . .
Span (measured from fuselage reference l i n e ) . f t . . .
1.343
Root chord (on fuselage reference line). f t . . . . . . 1.455
Tip chord. f t . . . . . . . . . . . . . . . . . . . . . 0.380
Sweep o f quarter-chord line. deg . . . . . . . . . . .
Area ratio. Sd/Sw. percent . . . . . . . . . . . . . . 21.6
A s p e c t r a t i o . . . . . . . . . . . . . . . . . . . . . 1.802
Taper r a t i o . . . . . . . . . . . . . . . . . . . . . . 0.26
.
TAEW 1 1 . - SZMMARY OF CANARD POSITIONS TEslJED Erosses indicate location of canard leading edge. Canard was perpendicular t o local faelage surface3
+ I6 - 2 . 6
24, - 1 . 0 +23 - . 4 * I 7 _ _ _ _ - -~ 2 2 - -
+ I + I 3 - .5
1 0 1 9 s +6 +21 +2 + I 4 - 1 . 9 - 3.0 + 3 * I5 - 3 . 6 +4 I I
0 3.67 6.67 1 9 . d 7 1 3 1 4 1 1 6 1 7 4 1 9 . 7 4 22.38 --Model stktlons
Conard surfaces Oto 50 f 20 2 20,30 f 1 0 I *20 15to50 !
I thru I 6 2 , 7 , I1,16 20 i 2,lO I I 1 3 1 7 l 8 , 1 9 , 2 0 , 2 1 f 1 0 2 I O 1 : 2,d, I3 I t i8 2 30
I *I0
I I 2 i ~ 20,30 I O ............... .......
. - - - . . . . . . . . . . . .
_ _ - - .
e e .. - - -
. . 0 . .
.......
1 0
0 . 0 . . : NACA RM L56F19a
............ .........
X Wind direction Y Z Y Figure 1.- The stability system of axes. Arrows indicate the positive direction of forces, moments, and angular displacements.
Figure 2.- Sketch of model used i n investigation. A l l dimensions are in inches.
2 f CY 0 -2 -4 -6 C " 0 -02 -04 -06 -08 \-- - -24 -16 -8 0 8 1 6 24 '924 -16 -8 0 8 1 6 24 Bdeg a d e g ( a ) T a i l o f f .
Figure 3.- Variation of t h e s t a t i c lateral s t a b i l i t y c h a r a c t e r i s t i c s with angle of s i d e s l i p . Basic configuration.
-24 4 6 -8 0 8 1 6 24 adeg on.
Figure 3.- Concluded.
.4 .2 CY 0 -. 2 -.6 -.4 .06 .04 .02 Cn 0 0 2 -.E .08 .06 .02 CI 0 -02 .04 -.06 -'824 -16 -8 0 8 1 6 24 i - 1 6 -8 0 8 1 6 24 B,deg a,deS ( a ) T a i l o f f . ( b ) T a i l on.
Figure 4. - Variation of s t a t i c lateral s t a b i l i t y c h a r a c t e r i s t i c s w i t h angle of s i d e s l i p . Access doors extended.
= d o w 0 % m a l II v o b a m m 0 ) V * : 0 4 - 1 a 0
” .. -
0 . 0.. . *<. a*.. . .* ’ . . . 0.. 0 .
0 . .. 0 . . 0 . . 0 . . ...
. . 0 . . 0 . . . . ....
... ..: ’.: NACA RM L56Flga
. . - : .
0 . 0 . 0.. 0 . .
(D In a , d- cv +I d II Q cum “-8 n
5 6
W s !
a , I I I \ I I I I I I I I I I I I I I I I I I I X I I I I I I I I l o +.
c d -P m d k O c $ 1 .
0- In +I
&
6 0 II m n
“ I
P W I I I I l l I I I I I I I I I I I I k (u +I II cl I w n cd v Canwd Posltm - 0 - off D - - d m I o---- d&a 2 ~ A-- I x 6 2 .
CY 0 -2 .04 .02 c n o -02 ( a ) a = 2 0 ~ .
Figure 7.- Effect of canard size and shape on the variation of s t a t i c l a t e r a l s t a b i l i t y characteristics with angle of sideslip.
Tail on.
A l l dimensions are in inches.
.. ... . ... . .. .. . . . ... ..
.. ..
NACA RM L56Flga ' . ...
-
0 - off 0- -doors I - delta ~ - - - - 1 x 6 .2 c c , -.2 .04 .02 Cn o -02 -04
4 -.02 -.04
- 1 6 -8 0 8 1 6
- I6 - 8 0 8 1 6
B,deg
am
(b) a = 30'.
Figure 7.- Concluded.
-a a a a a a a a. a a . a a a* a a NACA RM ~56~i93, a a . . a .
canard 0 - O f f A-- I x 6 b--- 1 x 3 n 4 x 3 2 1 Figure 8.- Effect of canard position and size on the variation of s t a t i c lateral s t a b i l i t y characteristics with angle of sideslip.
T a i l on.
A l l dimensions are i n inches.
.4 .2 CY 0 -.2 I I I I I I I I I I W I -4 .08 .04 Cn .02 -.02 -.04 -06 .06 c' 0 -02 -04 -06 -24 -16 -8 0 8 1 6 24 -24 - 1 6 -8 0 8 1 6 24 4deg a d e g ( a ) Tail o f f . ( b ) T a i l on.
Figure 9.- Effect of angle of attack on variation of the s t a t i c l a t e r a l s t a b i l i t y characteristics with angle of sideslip f o r the -- by 3-inch canard surface a t position 2.
I 1 0 1 4 3
-.m
-.m
-003
CI'B
-002 -.001
.mi! I I I I I I I I I U I
0 8 1 6 24 32 40 48 56 0 8 1 6 2 4 3 2 4 0 4 8 5 6 & 4 d e g (a) B = 5'. (b) = f 2 0 ° .
Figure 10.- Effect of canasd surfaces on the v a r i a t i o n of s t a t i c side- s l i p derivatives with angle of attack.
.
Cm -.2 Canard Position 0 - off - o - - doors 1 o - - - - - I 2 x 3 2
- .4
-.6 1.4 1.2 1.0 cL .8 cD .6 .4 .2 Figure 11.- Longitudinal characteristics of the model.
B = 0'.
NACA - Langley Field, Vd.