Sep 2012 Lesson 2.2 Theory of Flight Wing Design

Sep 2012Lesson 2.2

Theory of Flight

Wing Design

Reference

From the Ground Up

Chapter 2.1.2:

Design of the Wing

Pages 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 Flight

Airplane Axes

From the Ground Up

Chapters 2.1.3, 2.1.4:

The Axes of an Airplane, Stability

Pages 23 – 26