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N A S A TECHNICAL N O T E N A S A TN D-3025
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EFFECT OF WING PLANFORM MODIFICATION
ON LONGITUDINAL CHARACTERISTICS
O F A VARIABLE-SWEEP M W I N G
by Edward J. Ray and WiZlium P. Henderson
Langley Research Center
Lungley Station, Hampton, Vu.
N A T I O N A L A E R O N A U T I C S A N D SPACE A D M I N I S T R A T I O N W A S H I N G T O N , D. C. O C T O B E R 1 9 6 5 NASA TN D-3025 EFFECT OF WING PLANFORM MODIFICATION ON LONGITUDINAL CHARACTERISTICS OF A VARIABLE-SWEEP M WING By Edward J. Ray and William P. Henderson Langley Research Center Langley Station, Haiipton, Va.
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EFFECT OF WING PLANFORM MODIFICATION ON LONGITUDINAL CHARACTERISTICS OF A VARIABU-SWEEP M WING By Edward J. Ray and William P . Henderson __-- .
Langley Research Center SUMMARY
An investigation was conducted in the Langley high-speed 7- by 10-foot tun-
nel to determine the effects of wing planform modifications on the longitudinal aerodynamic characteristics of a variable-sweep wing having an M planform. The test planforms were investigated in combination with a basic-fuselage-vertical tail configuration, without engine packs or horizontal tail. The investigation was made at a Mach number of 0.40, corresponding to a dynamic pressure of about 213 lb/sq ft ( 101.98 N/m2), and a Reynolds number of 2.52 X 1 0 6 per foot (per 30.5 cm), through an angle-of-attack range which extended from - 3 O to 220.
The results indicated that increases in the aspect ratio and taper of the basic planform, accomplished by removing portions of the trailing edge of the outer wing panel, resulted in slight decreases in the variation of the longi- tudinal stability level with leading-edge sweep angle. The low-lift pitch-up tendencies of the basic planform, however, were aggravated by the modifications to the trailing edge of the outer wing panel. Modifications which were made to the basic planform by removing portions of the wing tip resulted in substantial reductions in the variation of longitudinal stability level with wing sweep. In addition, the wing-tip modifications considerably improved the variation of pitching-moment coefficient with lift coefficient at all leading-edge sweep , angles.
INTROIXJCTION The National Aeronautics and Space Administration has investigated a number of configurations in the study of the longitudinal stability characteristics of Examples of some of these various configurations are pre- variable-sweep wings.
The advantages of the variable-sweep M wing, from sented in references 1 to 4 .
the standpoint of longitudinal stability characteristics, are discussed in ref- erence 4. The investigation presented herein is related to the study described in reference 4 in that the basic wing series of the present investigation is identical to one of the wing series utilized in the investigation of reference 4 .
This wing consisted of a series of flat-plate airfoils representing a variable- sweep M wing at several different leading-edge sweep angles with an assumed wing pivot located at 45 percent of the sweptback wing semispan. The study presented in reference 4 was concerned with the determination of the effects of wing pivot location on the variations of the longitudinal stability level with wing sweep and the variation of pitching-moment coefficient with lift coefficient. The
results of reference 4 revealed that the variable-sweep M wings exhibited pitch-
up at all the test wing-sweep angles and wing pivot locations. The nonlinear- ities in the variation of pitching-moment coefficients with lift coefficients
indicated in the investigation of'reference 4 might have been alleviated by
proper placement of a horizontal tail. However, to provide freedom in the posi- tioning of the horizontal tail so as to avoid engine-efflux effect, the pitch-up must be minimized for the wing alone. The present investigation, therefore, was undertaken to study the effect of various wing planform modifications on the longitudinal characteristics of a variable-sweep M wing in an attempt to elim- inate the undesirable variations of pitching-moment coefficient with lift coefficient.
The investigation included tests of five series of variable-sweep M wings, differing in outer wing panel planform, combined with a basic-fuselage-vertical- tail combination. Each wing series consisted of flat-plate airfoils with leading-edge outer panel sweeps of l5OY 30°, and 72O. The simulated pivot point for all the wing series was located at 45 percent of the sweptback wing semispan.
The investigation was conducted in the Langley high-speed 7- by 10-foot wind
tunnel at a Mach number of 0.40 which corresponds to a dynamic pressure of about 6 per foot (per 213 lb/sq ft (101.98 N/m2), and a Reynolds number of 2.52 X 1 0 30.5 cm). Lift, drag, and pitching-moment data were determined for all the test configurations through an angle-of-attack range extending from -3O to 25O.
COEFFICIENTS AND SYMBOLS The forces and moments measured on this configuration are presented about the wind-axis system. All coefficients are nondimensionalized with respect to 72O.
the geometric characteristics associated with the maximum-sweep position of The reference dimensions for each wing series are given in table I . The plan- form area at the wing-fuselage juncture included in the reference areas of the test wing planform is indicated by the dashed lines shown in figure 1. The moment-reference points were chosen such that the 150 sweptback wing of each wing series had a longitudinal stability level of 5 percent of the mean aero- dynamic chord. The moment-reference center for each wing series is shown in 1 to 3 .
figures The units used for the physical quantities defined in this paper are given both in U.S. Customary Units and in the International System of Units (SI).
Factors relating the two systems are given in reference 5.
b2
A -
aspect ratio, S b wing span, in. (m) Drag
drag coefficient, -
CD
ss
L i f t
lift coefficient, -
cL
ss
lift-curve slope, per deg cLU Pitching moment pitching-moment coefficient, Cm qsp longitudinal s t a b i l i t y parameter, &Cm/&CL, near CL = 0 C V L F mean aerodynamic chord, i n . ( m ) dynamic pressure, lb/sq f t (N/rn2) S wing reference area, sq f t
(2)
U angle of attack, deg A leading-edge sweep angle of the movable panel, deg MODELS The models of t h i s investigation u t i l i z e d f l a t - p l a t e wings mounted beneath a fuselage with a v e r t i c a l t a i l . Drawings of the configurations investigated a r e shown i n figures 1 t o 3 . The basic w i n g of t h i s investigation i s designated shown i n figure 1. This wing i n the 7 2 O sweptback position wing s e r i e s 1 and i s had an M planform with the leading-edge break located a t 33 percent of the wing semispan. The wing pivot was located at 45 percent of the wing semispan and at 60 percent of the streamwise chord of the sweptback wing.
During the present investigation the movable panel of the basic wing series was modified t o produce the wing s e r i e s designated 2 t o 5. Wing s e r i e s 2 and 3 ( f i g . 2) were obtained by cutting away part of the t r a i l i n g edge of the movable p m e i of the basic wing so t h a t the trailing-edge sweep of the movable wing panel was changed i n increments of 5 O . The modifications made t o the basic wing s e r i e s t o obtain wing s e r i e s 2 and 3 r e s u l t i n a wing which not only has a higher aspect r a t i o but also has increased taper and l e s s area.
Wing s e r i e s 4 and 5 ( f i g . 3) were obtained by removing portions of the wing This type of modification r e s u l t s i n a wing which t i p of the basic wing series.
has a span reduction for the wing i n the 150 sweep position of 14 and 28 percent f o r wing s e r i e s 4 and 5, respectively. Since only the outer panel of the basic wing w a s modified, t h i s span reduction results i n wings which have lower aspect r a t i o s and l e s s taper.
Wing sweep angles of 15O, 3 0 ° , and 72O were investigated for all the wiAg series. The wings were 3/16-inch (0.476-cm) flat plates with rounded leading edges and blunt trailing edges. N o attempt was made to fair the wings into the fuselage and therefore the drag characteristics should be used with caution.
TESTS AND CORRECTIONS
The investigation was made in the Langley high-speed 7- by 10-foot tunnel
at a Mach number of 0.40 which corresponds to a dynamic pressure of about 213 lb/sq ft (101.98 N/m2), and a Reynolds number per foot (per 30.5 cm) of 2.52 X lo6.
Lift, drag, and pitching moment were measured through an angle-of-attack The angle of attack was corrected for deflection of the range of -30 to 220.
sting support system under load. The drag data have not been corrected for the effects of base pressure acting on the base of the fuselage and the balance chamber. These tests were made without artificial transition strips on either the wings or the fuselage. Jet-boundary and blockage corrections (estimated from refs. 6 and 7) have been applied to the data.
PRESENTATION OF DATA The data are presented in the following figures: Figure Effect of wing sweep on longitudinal aerodynamic characteristics of configuration with:
Wing series 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Wing series 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Wing series 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Wing series 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Wing series 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Effect of wing planform modifications on variation of lift-curve slope and longitudinal stability parameters for:
Wingseriesl, 2, a n d 3 . . . . . . . . . . . . . . . . . . . . . . . . . 9
Wing series 1, 4, and 5 . . . . . . . . . . . . . . . . . . . . . . . . . 1 0
Effect of wing planform modifications on variation of pitching moment with lift coefficient for:
Wingseriesl, 2, and3 . . . . . . . . . . . . . . . . . . . . . . . . . 11
Wingseries1, 4, a n d ? . . . . . . . . . . . . . . . . . . . . . . . . .12
RESULTS AND DISCUSSION Since the main interest of this investigation was the effect of wing plan- form modifications on the stability characteristics of the basic wing series, the test wings were constructed of plate material to minimize fabrication time.
No attempt was made to blend the wings with the basic fuselage o r to correct the data for the pressure acting on the base of the fuselage.
The reader is advised, therefore, to view the drag data with caution. The drag results have been pre- sented herein without analysis simply t o afford the reader an opportunity to observe the effects of the various wing modifications on the induced drag.
Effects of Wing Sweep on Longitudinal Characteristics of Wing Planforms The effects of wing sweep on the longitudinal aerodynamic characteristics
of the five M wing planforms are shown in figures 4 to 8 . It should be noted
that the moment-reference points for these test models have been adjusted so that the l5O sweptback wing of each wing series had a low-lift static margin of
5 percent of the mean aerodynamic chord. The data (See figs. 1 , 2, and 3 . )
shown in figures 4 to 8 indicate that the effects of wing sweep on the longi- tudinal aerodynamic characteristics of the test models were similar for the five wing planforms investigated. In general, these data indicate that increases in the leading-edge sweep of the outer wing panels resulted in reductions of the and more favorable variations of pitching-moment coef- lift-curve slope
cLa
ficient with lift coefficient.
of Wing Planform Modifications on bngitudinal Effects Aerodynamic Characteristics of Basic Wing The planform modifications which were made to the basic wing series, wing Wing series 2 and 3 (fig. 2) series 1 , consisted of two types of modifications.
represent modifications which were made to the basic planform by removing area The trailing-edge modifications from the trailing edge of the outer wing panel.
resulted in wings having a higher aspect ratio and more taper than the basic wing.
Wing series 4 and 5 (fig. 3 ) were obtained by removing portions of the
wing tip of the basic planform. Wing series 4 and 5, therefore, had lower
aspect ratios and less taper than the basic wing series 1 planforms.
The effects of the modifications to the trailing edge of the outer wing panel on the longitudinal characteristics of the basic planform may be deter-
4) with the results for
mined by comparing the results for wing series 1 (fig.
wing series 2 and 3 (figs. 5 and 6 ) , respectively. A comparison of the varia-
tions of the longitudinal aerodynamic characteristics with wing sweep for these three wing planforms is shown in figure 9. It should be noted here that the
results contained in reference 4 were utilized to aid in the fairing of the
data shown herein in figures 9 and 1 0 . These data indicate that the removal of area from the trailing edge of the basic planform, with consequent increases in Wing aspect ratio, resulted in higher lift-curve slopes at all sweep angles.
series 3, having the highest aspect ratio, exhibited an increase in lift-curv-e slope of about 0.003 throughout the wing-sweep angle above the lift-curve slope values indicated for the basic planform. The variation of the longitudinal with the leading-edge sweep angle was reduced slightly stability parameter C V L for wing series 2 and 3, due to the removal of area from the trailing edge of the The largest reduction in the variation of the longitudinal outer wing panels.
with sweep angle was a reduction of about 0.015 as stability parameters C q L indicated for wing series 3.
A comparison of the results for wing series 1 (fig. 4) with the longitudinal
Characteristics of wing series 4 and 5 (figs. 7 and 8) indicates the effects of These effects removing portions of the wing tip from the basic wing planform.
have been summarized in figure 10. The lift-curve slopes indicated for wing series 4 and 5 were lower than the lift-curve slopes of the basic planform throughout the sweep range due to the reductions in aspect ratio. In addition, the removal of area from the outer wing panel substantially improved the varia- tion of the longitudinal stability parameter with leading-edge sweep c"cL angle, and in fact produced less longitudinal stability at 7 2 O sweep than at 15O sweep.
Figures 11 and 12 were prepared to illustrate the effect of the various planform modifications on the variation of pitching-moment coefficient with lift coefficient. The pitching-moment data shown in figures 11 and 12 have been adjusted so that the static margins of the wing planforms at all sweep angles were equal to 5 percent of the mean aerodynamic chord F of each planform. The effects of the trailing-edge modifications to the outer wing panel on the longi- tudinal stability characteristics of the model are shown in figure 11. The trailing-edge modifications to the basic wing planform are seen to have an adverse effect on the longitudinal stability characteristics. The increased nonlinearities in the variation of pitching-moment coefficient with lift coef- ficient indicated for wing series 2 and 3 resulted from the increases in the taper of the basic wing panel which is believed to cause the flow over the outer wing panel to separate more readily.
Although the removal of area from the basic outer wing panel trailing edge aggravated the pitch-up tendency of the basic planforms, figure 12 shows that the longitudinal stability characteristics for the basic planform can be improved by removing area from the tip of the outer wing panel. The wing modifications of wing series 4 and 5, which in effect reduced the aspect ratio and taper Of the basic planform, considerably reduced the effect of outer wing panel sepa- ration on the pitching moment. Although the linearity of the variation of pitching-moment coefficients with lift coefficients was substantially improved by the removal of wing-tip area and subsequent reductions in aspect ratio, it should be remembered that these modifications would naturally result in reduc- tions of the subsonic lift-to-drag ratios.
The planform modifications which were considered in the present investi- gation did not improve the longitudinal stability characteristics of the basic planform to the extent that the variation of pitching-moment coefficient with lift coefficient was linear at all sweep angles. Wing series 5, however, having reduced taper and outer wing panel area exhibited a nearly linear variation of pitching-moment coefficient with lift coefficient at leading-edge sweep angles It is believed that the addition of leading-edge devices to of 300 and 720.
several of the test planforms would be one method to minimize the pitching-moment nonlinearities and result in acceptable longitudinal stability characteristics which, in turn, might possibly allow some freedom in the choice of wing planform and tail location. In addition, the longitudinal stability characteristics indi- cated in the present investigation for the flat-plate wings might be signifi- cantly changed by incorporating wing twist and camber.
CONCLUSIONS The results of a low-speed investigation to determine the effects of wing planform modifications on the longitudinal aerodynamic characteristics of a variable-sweep wing having an M planform indicated the following conclusions: 1 . Increases in the aspect ratio and outer panel taper of the basic plan- form, accomplished by removing portions of the trailing edge of the outer wing panel, resulted in slight decreases in the variation of the longitudinal sta- bility level with leading-edge sweep angle. The trailing-edge modifications, however, aggravated the low-lift pitch-up tendencies of the basic planform.
2. Modifications which were made to the basic planform by removing portions of the wing tip resulted in substantial redxtions in the variation of longi- tudinal stability level with wing sweep. The wing-tip modifications consider- ably improved the variation of pitching-moment coefficient with lift coefficient at all leading-edge sweep angles.
Langley Research Center, National Aeronautics and Space Administration, Langley Station, Hampton, Va., June 25, 1965.
, REFEIiENCES 1 . Henderson, William P.: Low-Speed Longitudinal Stability Characteristics of a Supersonic Transport Configuration With Variable-Sweep Wings Ehploying a Double Inboard Pivot. NASA TM X-744, 1962.
2. Alford, William J., Jr.; Ramona, Alexander D.; and Henderson, William P.: Low-Speed Stability Characteristics of a Supersonic Transport Model With a Blended Wing-Body, Variable-Sweep Auxiliary Wing Panels, Outboard Tail Surfaces, and Simplified High-Lift Devices. NASA TM x-802, 1963.
3 . Lockwood, Vernard E.; McKinney, Linwood W.; and Lamar, John E . : Low-Speed Aerodynamic Characteristics of a Supersonic Transport Model With a High- Aspect-Ratio Variable-Sweep Warped Wing. NASA TM X-979, 1964.
4. Henderson, William P . ; and Ray, Edward J.: Effect of Wing Pivot Location on Longitudinal Aerodynamic Characteristics of a Variable-Sweep Wing Having an M Planform. NASA TM X-1022, 1964.
5. Mechtly, E . A.: The International System of Units - Physical Constants and
Conversion Factors. NASA SP-7012, 1964.
6. Gillis, Clarence L.; Polhamus, Edward C.; and Gray, Joseph L., Jr.: Charts
7- by
for Determining Jet-Boundary Corrections for Complete Models in 10-Foot Closed Rectangular Wind Tunnels. NACA WR L-123, 1945. (Supersedes NACA ARR L5G3l. ) 7 . Herriot, John G.: Blockage Corrections for Three-Dimensional-Flow Closed- Throat Wind Tunnels, With Consideration of the Effect of Compressibility.
NACA Rept. 995, 1950. (Supersedes NACA RM ~7~28. )
TABLE I . - WING SERIES REFERENCE D l 3 E N S I O N S
-
S b C Wing A s e r i e s f t 2 in. cm in. cm 1.814 0.1604 21.240 53.95 34.52 1.727 21.240 1.888 32.78 1.659 53.95 21.240 1.568 1457 55.95 32-50 1.998 34.64 1.627 1.623 19.500 49.53 34.82 1.463 1.514 .1407 17.860 45.36
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W i n g series 0 f 0 4 A c A ,deq Figure 10.- Effect of wing planform modifications o n variation of l i f t - c u r v e slope a n d longitudinal stability parameter w i t h w i n g sweep.
W i n g series - 4 -,2 0 .2 4 . 6 .8 L O L 2 /.4 ‘ i Figure 11.
Effect of w i n g planform modifications o n variation of pitching-moment coefficient Cm w i t h l i f t coefficient CL, (Data transferred to common stability level near CL = 0 . ) .
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NASA-Langley, 1965 L-4559 2 6