Airfoil

An airfoil is a shaped surface, such as a wing section, that generates aerodynamic forces as air flows around it. Its geometry influences lift, drag, and pitching moment.

Lift (force): The component of aerodynamic force perpendicular to the oncoming flow. Pressure differences and momentum changes around an airfoil produce lift.
Chord (aeronautics): The straight-line distance from an airfoil's leading edge to its trailing edge. Chord supplies a reference length for airfoil dimensions and aerodynamic coefficients.
Aircraft wing: A lifting surface attached to an aircraft that supports flight through aerodynamic force. An aircraft wing uses airfoil sections along its span to generate lift.
Symmetrical airfoil: An airfoil whose upper and lower surfaces are mirror images across its chord line. It produces no camber-based lift at zero angle of attack, unlike a cambered profile.
George Cayley: An English engineer who established foundational principles of heavier-than-air flight in the nineteenth century. Cayley separated lift and propulsion and used curved surfaces in glider designs.
Angle of attack: The angle between a body's reference line and the oncoming flow. Changing this angle alters an airfoil's lift and can trigger stall.
Camber: The curvature of an airfoil's mean line between its upper and lower surfaces. Camber strongly affects lift at a given angle of attack.
Propeller: A rotating assembly of blades that produces thrust by accelerating a fluid. Each propeller blade uses airfoil sections to create force as it rotates.
Supercritical airfoil: An airfoil profile designed to delay shock formation and reduce drag near transonic speeds. Its flattened upper surface and aft loading address compressibility limits of conventional profiles.
Otto Lilienthal: A German aviation pioneer who studied gliding and published measurements of aerodynamic lift. His experiments with curved wings helped turn airfoil design into an empirical practice.

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