1. Presented by Dan Shafer James Pembridge Mike Reilly
Winglets
Presented by
Dan Shafer
James Pembridge
Mike Reilly

2. Outline Introduction History Pros / Cons Force Diagram
Design Considerations
Case Study

3. Problem Induced drag Produced by 3-D airflow around wing tips
Large for high-lift, low speed flight conditions
50% of total drag for subsonic transports opperating at high subsonic speeds
Maughmer, D., Mark, “About Winglets”, Fig 3

4. Solution
Winglets

5. Origins Nature F.W.Lanchester Wingtip configuration on birds
Numerous feathers at wing tips
F.W.Lanchester
Vertical surfaces at wing tips reduced induced drag(1897)
Vertical endplates produced a large reduction in drag at high lift conditions

6. Origins Richard T.Whitcomb Inspired by birds
A properly cambered and angled surface could reduce the strength of trailing vortex
“winglets” emphasize design process similar to wings

7. Winglets Reduce wingtip vortices Cut back on drag up to %20*
Higher cruise speed
Increased fuel economy
Possibly double wings
lift to drag ratio *
Good when wing extension
is not possible
*Richard Whitcomb NASA aerodynamicist
Picture courtesy of Cessna Aircraft

8. Proven Performance Mission block fuel is improved approximately 4
percent (BBJ)
Range increased by as much as 200 nm (BBJ)
and up to 130 nm ( )
6.5 percent reduction in noise levels around
airports on takeoff
4 percent reduction in nitrogen dioxide
emissions on a 2,000-nmi flight.

9. Additional Thrust
The angle at which the winglets' airfoils diverge from the relative wind direction, determine the magnitude and orientation of the lift force generated by the winglet itself. By adjusting these so that the lift force points slightly forward, additional thrust is achieved
Additional Thrust
Inboard Force
Resultant Force

10. Good idea Allow for steeper climb
Good for obstacle-limited, high, hot, weight-
limited, and/or noise-restricted airports
Lower wing spar bending moment than
wingspan extension
Eye catching
For the same amount of structural material,
nonplanar wingtip devices can achieve a
similar induced drag benefit as a planar span
increase

11. Design Challenges Cons Have a tendency to cause wing flutter
Winglet design is very detailed and
complicated
Difficult to determine boundary layer effects
at wingtip/winglet junction (separation,
pressure gradient)
Usually not in initial design

12. Design of Winglets Geometry of Winglet Airfoil Chord distribution
Height
Twist
Sweep
Toe angle

13. Winglet Airfoil
Goal:
Generate enough lift while maintaining the lowest possible drag
Should not stall before wing during low speed flight
Geometry driven by aerodynamic characteristics of the airfoil
Limitation
Narrow chords yield low Re
Re range from 1E5 to 1E6

14. Chord Distribution Sizing Spanwise elliptical chord distribution
Too small:
Airfoil will require a large lift coefficient
Too big :
High winglet loading
Causes outboard section of wing to stall prematurely
Spanwise elliptical chord distribution
Elliptical planform will help with load distribution over a large range of flight regimes

15. Winglet Height Twist/Sweep
Determined by the optimal induced drag and profile drag relationship
Twist/Sweep
Have similar effects on the winglet
Tailor the load distribution

16. Toe Angle Mounting angle Controls overall loading on winglet
Effects the load distribution on main wing
Only optimum for one flight condition

17. Tornado© VLM code for MATLAB
Winglet Modeling
Tornado© VLM code for MATLAB
Winglet Geometry
L = 57 deg
b/20, b/10
Taper => l = 0.3

18. Aircraft Configuration
Winglet Modeling
Aircraft Configuration
dihedral = 4.6o
L1/4 = 20o
l = 0.6

19. Original Configuration
Winglet Modeling
Original Configuration
a = 8o
L/D = 51

20. Winglet Modeling Small Version 11% drag reduction 8% drag reduction
(7% when compared to an extended wing)
8% drag reduction
(4% when compared to an extended wing)

21. Winglet Modeling Large Version 22% drag reduction 12% drag reduction
(14% when compared to an extended wing)
12% drag reduction
(4% when compared to an extended wing)

22. Winglet Modeling
Side View

23. Conclusions Drag reductions up to 20%
Winglets only needed on designs with higher than normal induced drag
Beneficial in canard configuration

24. References
“Concept to Reality: Winglets”.
Maughmer, D., Mark, “Sailplane Winglet Design”.
Maughmer, D., Mark, “The Design of Winglets for High-Performance Sailplanes”, AIAA Paper
Melin, T., Tornado 1.23b, MATLAB code available at

25. Questions?