Sep 2012Lesson 2.2

Theory of Flight

Wing Design

Reference

From the Ground UpChapter 2.1.2:Design of the WingPages 20 - 23

Introduction• There are many different airfoil designs. The

type of operation for which an airplane is intended has a direct influence on the design and shape of the wing for that airplane.

• Normally, an airplane designed for slow speed uses a thick airfoil and a thin airfoil is best for high speed.

Outline• Camber & Planform• Angle of Incidence• Wingtips and Wing Fences• Wash Out• Flaps & Spoilers

Wing Design• Conventional Airfoils

– Thick, for stronger structure– Camber is farther rearward, which Increases lifting capability over

more of wing and decreases drag– For larger, slower aircraft (such as cargo planes)– Thickest at 25% chord

Wing Design• Laminar Flow Airfoils

– Usually thin– Leading edge more pointed and upper and lower surfaces nearly

symmetrical– For smaller, faster aircraft (such as fighter jets)– Thickest at 50% chord

Planform• Planform – Shape of wing as seen from

above

• Aspect Ratio – Ratio of wing span to Chord (or MAC)

• High Aspect Ratio creates more lift and less induced drag

Angle of Incidence• Angle that wing is attached to fuselage

• Angle between wing and longitudinal axis (or the horizontal)

Longitudinal Axis

Longitudinal Axis

Angle of Incidence

Wing Tip Design• Different wing tip devices disrupt vortices, thus

decreases induced drag. Some devices: – Wing tip tanks– Wing tip plates– Droop wing tip– Winglets

Wing Fences• Small fin-like surfaces on upper surface of wing

• Control and straighten airflow, reduce wing vortices, and therefore reduce induced drag

• Provide better slow speed handling and stall characteristics

Wash-Out• Wash-Out - Twist in the wing so wing tip has

smaller angle of incidence than wing root

• Reduces tendency of wing to stall suddenly

• Wing tips stall last, so ailerons remain effective

Flaps and Spoilers• Slats - Airfoils on leading edge that pull out at

high angle of attacks. They help improve lateral control by smoothing out turbulent airflow

• Slots - Passageways in leading edge. At high angles of attack, air flows through holes smoothing out turbulent airflow

• Leading Edge Flap – Increase camber and increase lift

Flaps and Spoilers

Flaps and Spoilers• Spoilers - Devices fitted into wing that

increase drag and decrease lift

• Speed Brakes – Devices on wing or fuselage that increase drag

Flaps and Spoilers• Flaps are high lift devices that increase

the camber of the wing. Flaps give you:

– Better Take-off Performance– Steeper Approach Angles– Lower Approach/Landing Speeds

Next Lesson

2.3 - Theory of FlightAirplane Axes

From the Ground UpChapters 2.1.3, 2.1.4:The Axes of an Airplane, StabilityPages 23 – 26