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Presented by Dan Shafer James Pembridge Mike Reilly

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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?

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