Overview
This lecture introduces the concept of airfoils, explains how they generate lift, and defines key terms and types related to airfoil design.
Airfoil Basics
- An airfoil is the cross-sectional shape of an aircraft wing, designed to generate lift.
- Lift is produced due to pressure differences between the upper (lower pressure) and lower (higher pressure) surfaces of the airfoil.
- The upper surface airflow moves faster than the lower surface, reducing pressure above the wing.
Factors Affecting Lift
- Lift depends on airfoil shape, velocity, air density, surface area, and angle of attack (the angle between airflow and the chord line).
Key Airfoil Terms
- Leading edge is the front part of the airfoil that meets the air first.
- Trailing edge is the rear part of the airfoil that meets the air last.
- Chord is the distance between the leading and trailing edge.
- Chord line is a straight line connecting the leading and trailing edge.
- Camber line is a line equidistant from the upper and lower surfaces, running from leading to trailing edge.
- Thickness is the vertical distance from the top to the bottom surface.
- Leading edge radius is the curvature radius at the leading edge.
Aerodynamic Concepts
- Pitching moment is the twisting force created by aerodynamic forces on an airfoil.
- Center of pressure is the point where total lift force acts and where pitching moment is zero.
- Aerodynamic center is the point where pitching moment remains constant regardless of angle of attack.
- Angle of attack is the angle between relative wind and chord line; increasing it increases lift.
- Stall occurs when the angle of attack increases past a certain point, causing lift to drop and drag to rise.
- Stall angle is the specific angle of attack where stall begins.
Types of Airfoils
- Symmetric airfoils have identical upper and lower surfaces; chord line and camber line are the same.
- Non-symmetric (cambered) airfoils have different surfaces; camber line is above or below the chord line, affecting lift direction.
Key Terms & Definitions
- Airfoil — Cross-sectional shape of a wing, designed for lift.
- Lift — Force perpendicular to airflow, generated by pressure difference.
- Chord line — Straight line from leading to trailing edge.
- Camber line — Curve equidistant from upper and lower surfaces.
- Pitching moment — Twisting force on an airfoil from aerodynamic effects.
- Center of pressure — Point where lift acts; pitching moment is zero.
- Aerodynamic center — Point where pitching moment is constant.
- Angle of attack — Angle between airflow and chord line.
- Stall — Sudden drop in lift due to high angle of attack.
Action Items / Next Steps
- Review and memorize airfoil terms and definitions.
- Study the effects of angle of attack on lift and stall.
- Practice identifying types of airfoils and their characteristics.