Stall (fluid dynamics)

Airflow separating from an airfoil at a high angle of attack, as occurs at a stall.
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An example of the relationship between angle of attack and lift on a cambered airfoil. The exact relationship is usually measured in a wind tunnel and depends on the airfoil section. The relationship for an aircraft wing depends on the planform and its aspect ratio.
Flight envelope of a fast aeroplane. Left edge is the stall speed curve.
The airspeed indicator is often used to indirectly predict stall conditions.
Illustration of a turning flight stall, occurring during a co-ordinated turn with progressively increasing angle of bank.
Diagrammatic representation of a deep stall
A Schweizer SGS 1-36 being used for deep-stall research by NASA over the Mojave Desert in 1983.

Reduction in the lift coefficient generated by a foil as angle of attack increases.

- Stall (fluid dynamics)

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Spin (aerodynamics)

Spin — an aggravated stall and autorotation
Aerodynamic spin diagram: lift and drag coefficients vs. angle of attack
The DH 108—the missile-shaped objects on the wing tips are containers for anti-spin parachutes.

In flight dynamics a spin is a special category of stall resulting in autorotation (uncommanded roll) about the aircraft's longitudinal axis and a shallow, rotating, downward path approximately centred on a vertical axis.

Angle of attack

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.

The Wright brothers testing their gliders in 1901 (left) and 1902 (right). The different angles of attack probably at different airspeeds are providing the wanted lift.
Angle of attack of an airfoil
Platform angle of attack
Coefficients of drag and lift versus angle of attack. Stall speed corresponds to the angle of attack at the maximum coefficient of lift
A typical lift coefficient curve for an airfoil at a given airspeed.
Su-27M / Su-35 at high angle of attack

This is also called the "stall angle of attack".

Flap (aeronautics)

Trailing edge flaps extended on the right on a typical airliner (an Airbus A300). Leading edge slats are also extended, on the left.
The three orange pods are fairings streamlining the flap track mechanisms. The flaps (two on each side, on the Airbus A319) lie directly above these.
Flaps during ground roll after landing, with spoilers up, increasing drag.
North American T-6 trainer, showing its split flaps
Flaps and high lift devices. Gurney flap exaggerated for clarity. Blown flap skipped as it is modified from any other type. Pale lines indicate line of movement, and green indicates flap setting used during dive.
Plain flap at full deflection.
Split flap on a World War II bomber
Double slotted Fowler flaps extended for landing
Krueger flaps and triple-slotted trailing-edge flaps of a Boeing 747 extended for landing
Junkers flaps, doubling as ailerons.

A flap is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight.

Camber (aerodynamics)

Asymmetry between the two acting surfaces of an airfoil, with the top surface of a wing commonly being more convex (positive camber).

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An airfoil with reflex camber.

This minimizes the stalling speed of aircraft using the airfoil.

Lift coefficient

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.

A typical curve showing section lift coefficient versus angle of attack for a cambered airfoil

The angle at which maximum lift coefficient occurs is the stall angle of the airfoil, which is approximately 10 to 15 degrees on a typical airfoil.

T-tail

Empennage configuration in which the tailplane is mounted to the top of the fin.

Avro RJ-85 of SN Brussels Airlines (Belgium)
McDonnell Douglas MD-90
Piper PA-44-180 Seminole
Grob G 109 motor glider
Beechcraft 1900D of the Swiss Air Force
T-tail of aircraft (Tu-154)

The aircraft may be prone to stalls at high angles of attack, when airflow over the tailplane and elevators is blanked by the wings The American McDonnell F-101 Voodoo jet fighter suffered from this problem.

Canard (aeronautics)

Wing configuration in which a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft or a weapon.

A Saab 37 Viggen, the first modern canard aircraft to go into production
The 1906 Santos-Dumont 14-bis
The Wright Flyer of 1903 was a canard biplane
Curtiss-Wright XP-55 Ascender
The Kyūshū J7W1 Shinden (scale model)
XB-70 Valkyrie experimental bomber
Canards visible on a JAS 39 Gripen
Canards on a Su-47
Su-34, with canards
Rutan Long-EZ, with high-aspect-ratio lifting canard and suspended luggage pods
The control canard on an RAF Typhoon in flight
Pterodactyl Ascender II+2 with stabilizing canard
Su-33s with canard
Tu-144 with the retractable canards deployed and nose drooped
A Dassault Rafale in high angle-of-attack flight
The Beechcraft Starship has variable-sweep foreplanes.
B-1B Lancer showing left hand ride-control vane at nose

Rather than use the conventional tailplane configuration found on most aircraft, an aircraft designer may adopt the canard configuration to reduce the main wing loading, to better control the main wing airflow, or to increase the aircraft's maneuverability, especially at high angles of attack or during a stall.

Atmospheric icing

Atmospheric icing occurs in the atmosphere when water droplets suspended in air freeze on objects they come in contact with.

The effect of atmospheric icing on a tree in the Black Forest of Germany.

Icing conditions can be particularly dangerous to aircraft, as the built-up ice changes the aerodynamics of the flight surfaces and airframe, which can increase the risk of a stall and potentially accidents.

Aircraft flight control system

Aircraft's direction in flight.

A typical aircraft's primary flight controls in motion
Cockpit controls and instrument panel of a Cessna 182D Skylane
Blériot VIII at Issy-les-Moulineaux, the first flightworthy aircraft design to have the initial form of modern flight controls for the pilot
de Havilland Tiger Moth elevator and rudder cables

It shakes the control column when the aircraft is approaching stall conditions.

Airfoil

Cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine.

Examples of airfoils in nature and in or on various vehicles. The dolphin flipper at bottom left obeys the same principles in a different fluid medium; it is an example of a hydrofoil.
Streamlines around a NACA 0012 airfoil at moderate angle of attack
Lift and drag curves for a typical airfoil
Airfoil nomenclature
Different definitions of airfoil thickness
An airfoil designed for winglets (PSU 90-125WL)
An airfoil section is displayed at the tip of this Denney Kitfox aircraft, built in 1991.
Airfoil of a Kamov Ka-26 helicopter's lower rotor blade

In the region of the ailerons and near a wingtip a symmetric airfoil can be used to increase the range of angles of attack to avoid spin–stall.