An airfoil is a specialized shape designed to interact with a fluid, such as air, to generate an aerodynamic force. These shapes are fundamental to aircraft wings, propeller blades, and even boat sails, enabling them to produce lift or thrust. The specific contours of an airfoil play a significant role in determining how efficiently it can generate these forces.
What Airfoil Camber Means
Camber refers to the curvature of an airfoil. It represents the asymmetry between the upper and lower surfaces of a wing. To precisely define this curvature, engineers use the “mean camber line.” This imaginary line runs midway between the upper and lower surfaces of the airfoil, extending from the leading edge to the trailing edge.
If the mean camber line is straight, the airfoil is considered symmetrical. Most often, airfoils have a curved mean camber line.
Airfoils can exhibit different types of camber. Positive camber occurs when the mean camber line curves upward, making the upper surface more convex than the lower. This design is common in aircraft wings, as it is effective at generating lift. Conversely, negative camber means the mean camber line curves downward.
How Camber Creates Lift
The curvature of an airfoil generates lift by influencing how air flows over and under the wing. As an airfoil moves through the air, its shape causes the air to split, with some flowing over the curved upper surface and some flowing along the lower surface. The air traveling over the more curved upper surface must cover a greater distance in the same amount of time compared to the air flowing underneath. This causes the air above the wing to accelerate and move faster.
According to Bernoulli’s principle, an increase in fluid velocity corresponds to a decrease in pressure. Therefore, the faster-moving air above the wing creates an area of lower pressure. Simultaneously, the slower-moving air beneath the wing experiences relatively higher pressure. This pressure difference, with higher pressure below and lower pressure above, results in an upward force known as lift. This phenomenon explains how camber contributes to an aircraft’s ability to fly.
Different Camber Designs and Their Uses
Different degrees of camber are employed depending on an aircraft’s intended purpose and typical operating speeds. Airfoils with higher camber are effective at generating significant lift at lower airspeeds. This characteristic makes them suitable for aircraft designed for slow flight, such as general aviation planes or gliders, where maximizing lift at reduced speeds is beneficial. Highly cambered airfoils can experience increased drag at higher speeds.
Conversely, airfoils designed for high-speed aircraft, like fighter jets or commercial airliners, often feature less camber or a more symmetrical design. These designs prioritize minimizing drag at high speeds while still providing sufficient lift. Symmetric airfoils are advantageous for aerobatic aircraft that perform inverted flight, as they generate lift equally well when inverted.
Modern aircraft frequently utilize variable camber systems, such as flaps and slats, to modify the wing’s curvature during different phases of flight. Flaps, located on the trailing edge, and slats, on the leading edge, extend or pivot to increase the effective camber of the wing. This temporary increase in camber enhances lift, allowing aircraft to take off and land at slower speeds. These movable surfaces provide versatility, optimizing the wing’s shape for both low-speed, high-lift operations and high-speed, low-drag cruising.