

Key Aerofoil Terminology and Their Roles in Flight
Aerofoil is also called an airfoil. It is a surface shaped like an airplane wing, tail, or propeller blade, that produces lift and drag when moved through the air. An aerofoil generates a lifting force that acts at right angles to the airstream and a dragging force that acts in the same direction as the airstream. High-speed aircraft mainly implement low-drag, low-lift airfoils that are thin and streamlined and on the other hand, slow aircraft that carry heavy loads use thicker airfoils with high drag and high lift.
What is Aerofil?
Aerofoil refers to a cross-sectional shape having a design with a curved surface that provides the most favourable ratio between lift and drag in flight. Lift is the component that helps the force turn out to be perpendicular to the motion’s direction while drag is the component that is parallel to the motion’s direction.
Aerofoil or also known as Airfoil is a structure with curved surfaces designed to give the most favourable ratio of lift to drag in flight, which is mainly used as the basic form of the fins, wings, and tailplanes of most aircraft. Aerofoil is the cross-section design of the wing, blade, or sail. Lift is the component such that the force is perpendicular to the direction of motion and drag is the component parallel to the direction of motion. A similar idea is being used in the designing of hydrofoils which is used when water is used as the working fluid. A body that is airfoil-shaped, moving through a fluid produces an aerodynamic force. The design of the aerofoil depends on the weight, speed, and purpose of the aircraft and mainly depends on the aerodynamic characteristics. These are dependent on certain terms that need to be defined to understand the design.
Aerofoil Terminology
An aerofoil consists of various cross-sectional shapes. Different types of aerofoils are used for the construction of aircraft wings. To differentiate between different aerofoil shapes, an aerofoil’s properties are defined and specific terminologies are used. Aerofoil Terminology. An Aerofoil is being designed with a shape that has the capability of producing lift with relatively high efficiency as it passes through the air. An aerofoil can have many cross-sectional shapes. The terms which are related to aerofoils are as follows.
Chord: Chord can be defined as the distance between the leading edge, at the front of the aerofoil that is the point, and has maximum curvature and the trailing edge, at the rear of the aerofoil, that is the point with a maximum curvature along the chord line. It is a distance between the leading and trailing edges measured along the chord line.
Chord Line: Chord line is the straight line connecting the leading and trailing edges.
Leading-Edge: It is an edged part of an aerofoil that hits the air particles first.
Lower Surface: The lower surface is a higher static pressure surface which is also known as a pressure surface. It is the surface of an aerofoil between the leading and trailing edges, on the lower side.
Mean Camber Line: It is a line joining the leading and trailing edges of an aerofoil, at an equal distance from the upper and lower surfaces.
Maximum Camber: It is the maximum distance of the mean camber line from the chord line.
Maximum Thickness: It is the maximum distance of the lower surface from the upper surface.
Trailing Edge: It is an edged part from an aerofoil that hits the air particles last.
Upper Surface: The upper surface is associated with high velocity and low static pressure, which is also known as suction surface. It is the surface of an aerofoil between the leading and trailing edges, on the upper side.
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When the aerofoil is moving through a fluid, the following are the terms used to describe the behaviour:
Aerodynamic Center: The centre where the pitching moment is independent of lift coefficient and angle of attack.
Center Of Pressure: The centre where the pitching moment is zero.
The Angle Of Attack (AOA): The angle of attack is formed between a reference line on a body and the oncoming flow.
Pitching Moment: The moment or torque produced on the aerofoil by the aerodynamic force is known as the Pitching moment.
Lift Coefficient
The lift coefficient is a relationship between the lift generated by a lifting body to fluid density, fluid velocity, and the associated reference area, this is a dimensionless coefficient. Mathematical representation is as follows:
C\[_{L}\] = \[\frac{L}{q_{s}}\] = \[\frac{L}{\frac{1}{2}p.u.u.s}\] = \[\frac{2L}{p.u.u.s}\]
Where,
C\[_{L}\] : lift coefficient
L: lift force
S: relevant surface
q: fluid dynamic pressure
ρ: fluid density
μ : flow speed
Types of Aerofoil
The types of aerofoils that are used are as follows:
Symmetrical Aerofoil:
This has identical upper and lower surfaces that produce no life at zero AOA such that the chord line and mean camber line are the same. In most of the light helicopters in their main rotor blades, these applications are fine. It is the type of aerofoil that has identical upper and lower surfaces such that the chord line and mean camber line happen to be the same, resulting in the production of no life at zero angles of attack. Symmetrical aerofoil has application in the main rotor blades of various light helicopters.
Non-symmetrical Aerofoil:
Non-symmetrical aerofoil has different upper and lower surfaces such that the chord line is placed above with large curvature, and it is also known as a cambered aerofoil. This aerofoil is also known as cambered aerofoil and it has different upper and lower surfaces such that the chord line happens to be placed above with large curvature. The chord line and chamber line of Non-symmetrical aerofoil are different and the advantages of this type are a better lift to drag ratio and stall characteristics, thereby resulting in the production of a useful lift at zero angles of attack.
These have different chord lines and chamber lines. These are the advantages of a non-symmetrical aerofoil, that is the lift to drag ratio and stall characteristics are better and useful lift is produced at zero AOA. The only disadvantages are that they are not economical and there is a production of undesirable torque.
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Fun Facts
In American English it is Airfoil and in British English, it is known as Aerofoil.
An Aerofoil or Airfoil is the shape of a wing or blade of a propeller.
Aerofoil was invented by Sir George Cayley.
Aerofoil will provide either lift or downforce, when it is moving through a fluid, depending on what it is used for.
According to Newton’s third law, the air must exert equal and opposite force on the airfoil, which is known as lift.
Birds fly on the basis of airfoils for wing-lift.
The underwater fins of sailboats, such as centerboards, are also lifting foils and operate on the same principles as airfoils. Technically they should be called hydrofoils, but this term has already been taken; generally, they are just referred to as "foils"
It is important to note that any thin object such as a flat plate or even the deck of a bridge, at an angle of attack with respect to the airflow, will generate lift; there is nothing "magic" about the shape of an airfoil. However, the lift is generated with the minimum of drag, so it is important for efficiency, the airfoil shape ensures that.
FAQs on What Is an Aerofoil in Physics?
1. What is an aerofoil in Physics?
In physics, an aerofoil (also known as an airfoil in American English) is a body with a specially shaped cross-section designed to generate an aerodynamic force, primarily lift, when it moves through a fluid like air. Its streamlined shape, typically with a curved upper surface and a flatter lower surface, is crucial for its function in applications like aircraft wings and propeller blades.
2. How is an aerofoil's shape designed to produce lift?
An aerofoil's design is based on creating a pressure difference between its upper and lower surfaces. The curved top surface forces the air to travel a longer distance, making it move faster than the air passing under the flatter bottom surface. According to Bernoulli's principle, faster-moving air exerts lower pressure. This creates a region of lower pressure above the aerofoil and higher pressure below it, resulting in a net upward force called lift.
3. What is the fundamental difference between an aerofoil and a wing?
The primary difference lies in their dimensionality. An aerofoil refers to the two-dimensional (2D) cross-sectional shape or profile. A wing, on the other hand, is the three-dimensional (3D) structure that is built using an aerofoil profile. A wing has physical properties like wingspan and surface area, whereas an aerofoil is the geometric shape that defines the wing's cross-section.
4. What are the key forces acting on an aerofoil during flight?
There are two primary aerodynamic forces acting on an aerofoil:
- Lift: The force generated perpendicular to the direction of the oncoming airflow. It is the component that counteracts gravity and keeps an aircraft in the air.
- Drag: The force that acts parallel to the airflow and opposes the motion of the aerofoil. It is a form of resistance that must be overcome by the aircraft's thrust.
5. What are the main types of aerofoils and their applications?
Aerofoils are categorised based on their shape and intended use. The main types include:
- Symmetrical Aerofoils: These have identical upper and lower surfaces. They generate zero lift at a zero angle of attack and are used in aerobatic aircraft and helicopter rotor blades for stable, inverted flight.
- Cambered Aerofoils: These have a curved upper surface and a flatter lower one, designed to generate significant lift. They are the most common type, used in commercial airliners and general-purpose aircraft.
- Supercritical Aerofoils: These are designed for high-speed flight near the speed of sound. Their shape delays the formation of shockwaves, reducing drag, and they are used on modern jet aircraft.
6. What factors determine the amount of lift an aerofoil can generate?
The amount of lift generated by an aerofoil is influenced by several key factors:
- Velocity: Lift increases with the square of the velocity of the air flowing over the aerofoil.
- Air Density: Lift is directly proportional to the density of the air. Denser air at lower altitudes produces more lift.
- Surface Area: A larger wing surface area results in greater lift.
- Angle of Attack: This is the angle between the aerofoil's chord line and the oncoming air. Increasing the angle of attack generally increases lift, up to a critical point where the flow separates and the wing stalls.
7. Why is Bernoulli's principle essential for explaining the lift of an aerofoil?
Bernoulli's principle provides the core physical explanation for how an aerofoil generates lift. The principle states that for a fluid, an increase in speed occurs simultaneously with a decrease in pressure. The aerofoil's shape causes air to flow faster over its top surface than its bottom. This velocity difference, as explained by Bernoulli's principle, creates the necessary pressure differential (low pressure above, high pressure below) that produces the upward lift force.
8. Besides aircraft wings, what are some other real-world applications of aerofoil principles?
The principles of aerofoil design are applied in many fields beyond aviation. Some common examples include:
- Wind Turbines: The blades of a wind turbine are shaped like aerofoils to generate lift, which causes them to rotate.
- Propellers and Rotors: Both boat propellers and helicopter rotors are essentially rotating wings that use aerofoil shapes to create thrust or lift.
- Racing Cars: Spoilers and wings on racing cars are inverted aerofoils designed to create downforce, pressing the car onto the track for better grip at high speeds.
- Sails: The curved shape of a sail on a sailboat acts as an aerofoil, generating lift that propels the boat forward.

















