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# Angle of attack

In fluid dynamics, angle of attack (AOA, or \alpha (Greek letter alpha)) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is moving. [1]

In aeronautics and marine hydrodynamics, the advance ratio is the ratio of the freestream fluid speed to the propeller, rotor, or cyclorotor tip speed.

## Aerodynamics

Aerodynamics, from Greek ἀήρ aer (air) + δυναμική (dynamics), is the study of the motion of air, particularly its interaction with a solid object, such as an airplane wing.

## Aircraft principal axes

An aircraft in flight is free to rotate in three dimensions: yaw, nose left or right about an axis running up and down; pitch, nose up or down about an axis running from wing to wing; and roll, rotation about an axis running from nose to tail.

## Airfoil

An airfoil (American English) or aerofoil (British English) is the shape of a wing, blade (of a propeller, rotor, or turbine), or sail (as seen in cross-section).

## Airspeed

Airspeed is the speed of an aircraft relative to the air.

## Alpha

Alpha (uppercase, lowercase; ἄλφα, álpha, modern pronunciation álfa) is the first letter of the Greek alphabet.

## Angle

In plane geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle.

## Angle of incidence (aerodynamics)

On fixed-wing aircraft, the angle of incidence (sometimes referred to as the mounting angle) is the angle between the chord line of the wing where the wing is mounted to the fuselage, and a reference axis along the fuselage (often the direction of minimum drag, or where applicable, the longitudinal axis).

## Bernoulli's principle

In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

## Camber (aerodynamics)

In aeronautics and aeronautical engineering, camber is the asymmetry between the two acting surfaces of an aerofoil, with the top surface of a wing (or correspondingly the front surface of a propeller blade) commonly being more convex (positive camber).

## Chord (aeronautics)

In aeronautics, chord refers to the imaginary straight line joining the leading and trailing edges of an aerofoil.

## Drag equation

In fluid dynamics, the drag equation is a formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid.

## Euclidean vector

In mathematics, physics, and engineering, a Euclidean vector (sometimes called a geometric or spatial vector, or—as here—simply a vector) is a geometric object that has magnitude (or length) and direction.

## Fighter aircraft

A fighter aircraft is a military aircraft designed primarily for air-to-air combat against other aircraft, as opposed to bombers and attack aircraft, whose main mission is to attack ground targets.

## Fixed-wing aircraft

A fixed-wing aircraft is an aircraft, such as an airplane or aeroplane (note the two different spellings), which is capable of flight using wings that generate lift caused by the vehicle's forward airspeed and the shape of the wings.

## Flow separation

All solid objects traveling through a fluid (or alternatively a stationary object exposed to a moving fluid) acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface.

## Fluid dynamics

In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids - liquids and gases.

## Fuselage

The fuselage (from the French fuselé "spindle-shaped") is an aircraft's main body section.

## Greek alphabet

The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC.

## Lift (force)

A fluid flowing past the surface of a body exerts a force on it.

## Lift coefficient

The lift coefficient (CL, CN or Cz) is a dimensionless coefficient that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area.

## Lift-induced drag

In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is an aerodynamic drag force that occurs whenever a moving object redirects the airflow coming at it.

In aeronautics, the load factor is defined as the ratio of the lift of an aircraft to its weightHurt, page 37 and represents a global measure of the stress ("load") to which the structure of the aircraft is subjected: where: Since the load factor is the ratio of two forces, it is dimensionless.

## Point of sail

A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface.

## Pugachev's Cobra

In aerobatics, Pugachev's Cobra (or Pugachev Cobra) is a dramatic and demanding maneuver in which an airplane flying at a moderate speed suddenly raises the nose momentarily to the vertical position and slightly beyond, before dropping it back to normal flight.

## Sailing

Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the water (sailing ship, sailboat, windsurfer, or kitesurfer), on ice (iceboat) or on land (land yacht) over a chosen course, which is often part of a larger plan of navigation.

## Slip (aerodynamics)

A slip is an aerodynamic state where an aircraft is moving somewhat sideways as well as forward relative to the oncoming airflow or relative wind.

## Stall (fluid mechanics)

In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases.

## STOL

STOL is an acronym for a short takeoff and landing aircraft, which have short runway requirements for takeoff and landing.

## Supermaneuverability

Supermaneuverability is the ability of aircraft to maintain pilot control and perform maneuvers in situations and ways exceeding those that are possible using purely aerodynamic mechanisms.

## Swept wing

A swept wing is a wing that angles either backward or occasionally forward from its root rather than in a straight sideways direction.

## Wing configuration

The wing configuration of a fixed-wing aircraft (including both gliders and powered aeroplanes or airplanes) is its arrangement of lifting and related surfaces.

## Wing root

The wing root is the part of the wing on a fixed-wing aircraft that is closest to the fuselage.

## Zero-lift axis

A cambered aerofoil generates no lift when it is moving parallel to an axis called the zero-lift axis (or the zero-lift line.) When the angle of attack on an aerofoil is measured relative to the zero-lift axis it is true to say the lift coefficient is zero when the angle of attack is zero.

## References

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