An analytic and experimental effort was undertaken to assess the effectiveness and efficiency of three winglets mounted chordwise to the tip of a rectangular wing. The winglets, with an aspect ratio of 4.6, were mounted on a half-span wing having an effective aspect ratio of 6.29. 13 configurations of varying dihedral arrangements were analyzed with a vortex lattice method and tested in a low-speed wind tunnel at a Reynolds number of 600,000. While the analytic method provided fair agreement with the experimental results, the predicted trends in lift, drag, and (to a lesser degree) pitching moment were in good agreement. The analytic distributions of wake velocity, circulation, and downwash angle verified that highly nonplanar configurations tended to reduce and diffuse the regions of highest circulation and to create more moderate downwash angles in the wake. This was manifest as an overall drag reduction. More specifically, the results showed that the winglets could be placed in various optimum orientations to increase the lift coefficient as much as 65% at the same angle of attack, decrease the drag coefficient as much as 54% at the same lift coefficient, or improve the maximum LD by up to 57%. The most dramatic findings from this study show that positioning the winglet dihedral angles had the result of adjusting the magnitude and slope of the pitching moment coefficient. These observations suggest that multiple winglet dihedral variations may be feasible for use as actively controlled surfaces to improve the performance of aircraft at various flight conditions and to “tune” the longitudinal stability characteristics of the configuration.

1.
F.
Fiorino
, ed., 2003, “
Southwest 737-700s Earn Winglets
,”
Aviat. Week Space Technol.
0005-2175,
158
(
25
), p.
15
.
2.
Proctor
,
P.
, 1996, “
Winglets Span G2 Fleet
,”
Aviat. Week Space Technol.
0005-2175,
145
(
22
), p.
13
.
3.
Proctor
,
P.
, 1993, “
Winglet Designs to Cut Fuel Burn
,”
Aviat. Week Space Technol.
0005-2175,
139
(
23
), p.
49
.
4.
Spillman
,
J. J.
, and
McVitie
,
A. M.
, 1984, “
Wing Tip Sails Which Give Lower Drag at All Normal Flight Speeds
,”
Aeronaut. J.
0001-9240,
88
, pp.
362
369
.
5.
Whitcomb
,
R. T.
, 1976, “
A Design Approach and Selected Wind-Tunnel Results at High Subsonic Speeds for Wing-Tip Mounted Winglets
,” NASA Technical Note D-8260.
6.
Maughmer
,
M. D.
, 2003, “
Design of Winglets for High-Performance Sailplanes
,”
J. Aircr.
0021-8669,
40
(
6
), pp.
1099
1106
.
7.
Maughmer
,
M. D.
, and
Kunz
,
P. J.
, 1998, “
Sailplane Winglet Design
,”
Technical Soaring
,
22
(
4
), pp.
116
123
.
8.
Chattot
,
J. J.
, 2006, “
Low Speed Design and Analysis of Wing∕Winglet Combinations Including Viscous Effects
,”
J. Aircr.
0021-8669,
43
(
2
), pp.
386
389
.
9.
Hoey
,
R. G.
, 1992, “
Research on the Stability and Control of Soaring Birds
,” AIAA Paper No. AIAA-1992-4122.
10.
Tucker
,
V.
, 1995, “
Drag Reduction by Wing Tip Slots in a Gliding Harris’ Hawk, Parabuteo Unicinctus
,”
J. Exp. Biol.
0022-0949,
198
, pp.
775
781
.
11.
Smith
,
M. J.
,
Komerath
,
N.
,
Ames
,
R.
,
Wong
,
O.
, and
Pearson
,
J.
, 2001, “
Performance Analysis of a Wing With Multiple Winglets
,” AIAA Paper No. AIAA-2001-2407.
12.
La Roche
,
U.
, and
La Roche
,
H. L.
, 2004, “
Induced Drag Reduction Using Multiple Winglets, Looking Beyond the Prandtl-Munk Linear Model
,” AIAA Paper No. AIAA-2004-2120.
13.
Kroo
,
I.
,
McMasters
,
J.
, and
Smith
,
S. C.
, 1995, “
Highly Nonplanar Lifting Systems
,” presented at
Transportation Beyond 2000: Technologies Needed for Engineering Design
,
NASA Langley Research Center
, Sept. 26–28.
14.
Cone
,
C. D.
, 1963, “
The Aerodynamic Design of Wings With Cambered Span Having Minimum Induced Drag
,” NASA Technical Report No. TR R-152.
15.
Prandtl
,
L.
, 1923, “
Applications of Modern Hydrodynamics to Aeronautics; Part II: Applications
,” NACA Report No. 116, Taken From NASA, 1979, “Classical Aerodynamic Theory,” NASA Reference Publication No. 1050.
16.
Munk
,
M. M.
, 1923, “
The Minimum Induced Drag of Aerofoils
,” NACA Report No. 121.
17.
Abbott
,
I. H.
, and
Von Doenhoff
,
A. E.
, 1959,
Theory of Wing Sections Including a Summary of Airfoil Data
,
Dover
,
Mineola, NY
, Chaps., 1 and 6.
18.
Moffat
,
R. J.
, 1988, “
Describing the Uncertainties in Experimental Results
,”
Exp. Therm. Fluid Sci.
0894-1777,
1
(
1
), pp.
3
17
.
19.
Coleman
,
H. W.
, and
Steele
,
W. G.
, 1995, “
Engineering Application of Experimental Uncertainty Analysis
,”
AIAA J.
0001-1452,
33
(
10
), pp.
1888
1896
.
20.
1998,
Low Level Measurements
,
5th ed.
,
J.
Yeager
, and
M. A.
Hrusch-Tupta
, eds.,
Keithley Instruments, Inc.
,
Cleveland, OH
, Sec. 3.2.3.
21.
Barlow
,
J. B.
,
Rae
,
W. H.
, and
Pope
,
A.
, 1999,
Low-Speed Wind Tunnel Testing
,
3rd ed.
,
Wiley
,
Hoboken, NJ
, Chap. 10.
22.
Drela
,
M.
, and
Youngren
,
H.
, 2001,
XFOIL 6.94 User Guide
, Aeronautics, and Astronautics Engineering, Massachusetts Institute of Technology, Cambridge, MA.
23.
Margason
,
R. J.
, and
Lamar
,
J. E.
, 1971, “
Vortex-Lattice FORTRAN Program for Estimating Subsonic Aerodynamic Characteristics of Complex Planforms
,” NASA Technical Note D-6142.
24.
Lamar
,
J. E.
, and
Herbert
,
H. E.
, 1982, “
Production Version of the Extended NASA-Langley Vortex Lattice FORTRAN Computer Code; Volume I, User’s Guide
,” NASA Technical Memorandum TM-83303.
25.
Lamar
,
J. E.
, 2003,
Discussions of the Vortex Lattice Method Involving John Lamar, Pat Bookey, and David Miklosovic
,
NASA Langley
, Apr. 29.
26.
Miklosovic
,
D. S.
,
Murray
,
M. M.
,
Howle
,
L. E.
, and
Fish
,
F. E.
, 2007, “
Experimental Evaluation of Sinusoidal Leading Edges
,”
J. Aircr.
0021-8669,
44
(
4
), pp.
1404
1407
.
27.
Samoylovitch
,
O.
, and
Strelets
,
D.
, 2000, “
Determination of the Oswald Efficiency Factor at the Aeroplane Design Preliminary Stage
,”
Aircraft Design
,
3
(
3
), pp.
167
174
.
You do not currently have access to this content.