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In aerodynamics, a stall is a condition in which an excessive angle of attack causes loss of lift due to disruption of airflow. Aerodynamics is a branch of fluid dynamics concerned with the study of gas flows, first analysed by George Cayley in the 1800s. ...
In this diagram, the black arrow represents the direction of the wind. ...
Lift consists of the sum of all the fluid dynamic forces on a body perpendicular to the direction of the external flow around that body. ...
An aircraft in flight is usually not pointed directly into the oncoming airflow. The angle (when viewed from the side of the aircraft) between the airflow and the wing is called the angle of attack (not to be confused with the pitch angle). If a pilot allows the angle of attack to become too large, the airflow will be unable to remain attached to the wing and it will begin to separate from the wing, creating a dramatic loss of lift and increase in drag. This condition is known as a stall. Flight dynamics is the study of orientation of air and space vehicles and how to control the critical flight parameters, typically named pitch, roll and yaw. ...
Aviators are people who fly aircraft either for pleasure or for a job. ...
The Coanda effect is the tendency of a stream of fluid to stay attached to a convex surface, rather than follow a straight line in its original direction. ...
Stall recovery usually involves reducing the angle of attack to "break" the stall, and adding power to begin a climb.
Rigorous definition A stall is a condition in aerodynamics and aviation where the angle between the wing's chord line and the relative wind, defined as the angle of attack, exceeds the critical angle of attack. The critical angle of attack is the maximum angle of attack on the lift coefficient versus angle-of-attack curve, and it defines the boundary between the wing's linear and nonlinear regimes. Flow separation begins to occur at this point, decreasing lift, increasing drag, and changing the wing's pitching moment. A fixed-wing aircraft during a stall will experience buffeting, a change in pitching moment (nose up or nose down depending on tailplane configuration), and changes in most stability derivatives. Aerodynamics is a branch of fluid dynamics concerned with the study of gas flows, first analysed by George Cayley in the 1800s. ...
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The lift coefficient (CL) is a number associated with a particular shape of an airfoil, and is incorporated in the lift equation to predict the lift force generated by a wing using this particular cross section. ...
The word linear comes from the Latin word linearis, which means created by lines. ...
To do: 20th century mathematics chaos theory, fractals Lyapunov stability and non-linear control systems non-linear video editing See also: Aleksandr Mikhailovich Lyapunov Dynamical system External links http://www. ...
Tailplane and rudder of an Me 262 A tailplane is a small lifting surface located behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixedwing aircraft such as helocoperts and gyroplanes. ...
Aileron control of roll becomes less effective, whereas its (inverse) control of yaw increases, making adverse yaw even more pronounced. Roll-yaw coupling becomes more pronounced as roll due to sideslip angle predominates. Pitch and roll damping decrease due to lower dynamic pressure, and strong nonlinearities in the airflow. Aileron location on a Piper PA-28. ...
Increasing the angle of attack between an airfoil and the airflow causes the lift and drag produced to increase. This can continue until a point is reached where maximum lift is generated and this is known as the stall or stall angle. Any further increase in angle does not produce a corresponding increase in lift but will in fact lead to a sudden reduction in lift, a change in pitching moment or a wing drop. This is due to flow separation occurring on the upper surface of the airfoil, and therefore the critical angle of attack is dependent not only on the geometry of the configuration, but on the Reynolds number and surface roughness. In this diagram, the black arrow represents the direction of the wind. ...
An airfoil (in American English, or aerofoil in British English) is the shape of a wing or blade (of a propeller or ships screw) as seen in cross-section. ...
Lift consists of the sum of all the fluid dynamic forces on a body perpendicular to the direction of the external flow around that body. ...
For a solid object moving through a fluid or gas, drag is the sum of all the aerodynamic or hydrodynamic forces in the direction of the external fluid flow. ...
In physics, the moment of force (often just moment, though there are other quantities of that name such as moment of inertia) is a quantity that represents the magnitude of force applied to a rotational system at a distance from the axis of rotation. ...
A Laughing Gull on the beach in Atlantic City. ...
The Reynolds number is the most important dimensionless number in fluid dynamics and provides a criterion for determining dynamic similitude. ...
Depending on the aircraft's design, a stall can expose extremely adverse properties of balance and control. The ability of a particular craft to recover from a stall depends on the skill of the pilot and the dynamics of the aircraft to handle periods of reverse-direction with relative control. In unaccelerated flight, a stall is usually associated with a certain airspeed below which the aircraft will not continue to fly.
 Typical behavior of most airfoils. Lift Curve graph - created for a number of aerodynamics articles File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Lift Curve graph - created for a number of aerodynamics articles File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Graph The graph shows that the greatest amount of lift is produced just before the critical angle of attack is reached (which in early 20th century aviation was called the "burble point"). This angle is 17.5 degrees in this case but changes from aircraft to aircraft. The graph shows that as the critical angle of attack is exceeded, the lift produced by the wing decreases significantly. The aerofoil is now stalled.
Note that this graph shows the stall angle, yet in practice most pilots discuss stalling in terms of airspeed. This is because in general terms one can relate the angle of attack to airspeed - a lower speed requires a greater angle of attack to produce the necessary lift and vice versa. Thus as speed falls, AoA increases, until the critical angle is reached. The airspeed at which this occurs is the stalling speed of the aircraft in that particular configuration. Deploying flaps/slats decreases the stall speed to allow the aircraft to land at a lower speed. This article contains information that has not been verified and thus might not be reliable. ...
Lift consists of the sum of all the fluid dynamic forces on a body perpendicular to the direction of the external flow around that body. ...
Flaps are hinged surfaces on the trailing edge of an airplane wing which, when deployed, increase the lift (and drag) of a wing. ...
Aerodynamic description of a stall
Stalling an aeroplane An aeroplane can be made to stall in any pitch attitude or bank angle or at any airspeed but is commonly practised by reducing the speed to the stall speed, at a safe altitude. Stall speed varies on different airplanes and is represented by color codes on the air speed indicator. As the plane flies at this speed the angle of attack must be increased to prevent any loss of altitude or gain in airspeed (which corresponds to the stall angle described above). The pilot will notice the flight controls have become less responsive and may also notice some buffeting, an aerodynamic vibration caused by the airflow starting to detach from the wing surface. This article refers to the tool of travel. ...
Flight dynamics is the study of orientation of air and space vehicles and how to control the critical flight parameters, typically named pitch, roll and yaw. ...
Airspeed Indicator The airspeed indicator is an instrument used in an aircraft to display the crafts airspeed, typically in knots to the pilot. ...
It has been suggested that this article or section be merged with Aircraft flight mechanics. ...
In most light aircraft, as the stall is reached the aircraft will start to descend (because the wing is no longer producing enough lift to support the aeroplane's weight) and the nose will pitch down. Recovery from this stalled state usually involves the pilot decreasing the angle of attack and increasing the air speed, until smooth air flow over the wing is resumed. Normal flight can be resumed once recovery from the stall is complete. The maneuver is normally quite safe and if correctly handled leads to only a small loss in altitude. It is taught and practiced in order to help pilots recognize, avoid, and recover from stalling the airplane. General aviation (abbr. ...
The most common stall-spin scenarios occur on takeoff (departure stall) and during landing (base to final turn). Stalls also occur during a go-around maneuver if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed. Stall speed is increased when the upper wing surfaces are contaminated with ice or frost.
A special form of asymmetric stall in which the aircraft also rotates about its yaw axis is called a spin. A spin will occur if an aircraft is stalled and there is an asymmetric yawing moment applied to it. This yawing moment can be aerodynamic (sideslip angle, rudder, adverse yaw from the ailerons), thrust related (p-factor, one engine inoperative on a multi-engine non-centerline thrust aircraft), or from any number of possible sources of yaw. In flying, a spin is a special case of a stall, with the aircraft descending rapidly and rotating about a vertical axis. ...
Since most aircraft have an engine, too, a lot of language confusion exists between an aerodynamic versus engine stall. Many people seem to believe that an aircraft will drop out of the sky as soon as the engine stops in flight. In actuality, most aircraft will first slow up and then simply drop their nose. This gains them additional speed, and the aircraft will now be descending (in a controlled fashion) at more or less the same airspeed as it had before. The pilot has enough time to find a suitable landing surface on the ground or to restart the engine.
Put differently, all powered aircraft (even the biggest ones) become gliders when they lose all thrust. There have been cases of airliners running out of fuel at high altitude that landed successfully at airports a hundred kilometers away. The Gimli Glider is a celebrated example. Gliders are un-powered heavier-than-air aircraft. ...
The Gimli Glider is the name given to an infamous incident in aviation history. ...
Symptoms of an approaching stall One symptom of an approaching stall is slow and sloppy controls. As the speed of the airplane decreases approaching the stall, there are less air particles moving over the wing and therefore less will be deflected by the control surfaces (ailerons, rudder and elevator) at this slower speed. There may be slight buffeting of the controls as the stall is reached. The stall warning will sound, in most aircraft 5 to 10 knots above the stall speed.
Stalling characteristics Different aircraft types have different stalling characteristics. A benign stall is one where the nose drops gently and the wings remain level throughout. Slightly more demanding is a stall where one wing stalls slightly before the other, causing that wing to drop sharply, with the possibility of entering a spin. A dangerous stall is one where the nose rises, pushing the wing deeper into the stalled state and potentially leading to an unrecoverable deep stall. Deep stall is a dangerous condition that affects certain aircraft designs, notably those with a T-tail configuration. ...
Stall warning and safety devices Airplanes can be equipped with a variety of devices to prevent or postpone a stall or to make it less (or in some cases more) severe, or to make recovery easier. - A slight twist can be introduced to the wing with the leading edge near the wing tip twisted downward. This is called washout and causes the wing root to stall before the wing tip. This makes the stall gentle and progressive. Since the stall is delayed at the wing tips, where the ailerons are, roll control is maintained when the stall begins.
- The wing can be built with aerodynamic twist; the airfoil changes shape toward the wing tip in such a way that the wing tip has a lower stall speed than the wing root. This serves the same purpose as washout.
- A stall strip is a small sharp-edged device which, when attached to the leading edge of a wing, encourages the stall to start there in preference to any other location on the wing. If attached close to the wing root it makes the stall gentle and progressive; if attached near the wing tip it encourages the aircraft to drop a wing when stalling.
- Vortex generators, tiny strips of metal or plastic placed on top of the wing near the leading edge, lower the stall speed by preventing flow separation over the top of the wing.
- An anti-stall strake is a wing extension at the root leading edge which generates a vortex on the wing upper surface to postpone the stall.
- A stick-pusher is a mechanical device which prevents the pilot from stalling an aeroplane by pushing the controls forwards as the stall is approached.
- A stick-shaker is a similar device which shakes the pilot's controls to warn of the onset of stall.
- A stall warning is an electronic or mechanical device which sounds an audible warning as the stall speed is approached. The majority of aircraft contain some form of this device that warns the pilot of an impending stall. The simplest such device is a 'stall warning horn', which consists of either a pressure sensor or a movable metal tab that actuates a switch, and produces an audible warning in response.
- An angle of attack limiter or an "alpha" limiter is a flight computer that automatically prevents pilot input from causing the plane to rise over the stall angle. Some alpha limiters can be disabled by the pilot.
If a forward canard is used for pitch control rather than an aft tail, the canard is designed to stall at a slightly higher speed than the wing (i.e. the canard stalls first). When the canard stalls, the nose drops, lowering the angle of attack thus preventing the wing from stalling. Thus the wing virtually never stalls. Aileron location on a Piper PA-28. ...
Vortex created by the passage of an aircraft wing, revealed by coloured smoke A vortex is a spinning turbulent flow (or any spiral whirling motion) with closed streamlines. ...
A buzzer or beeper is a signalling device, usually electronic, typically used in automobiles, household appliances such as a microwave oven, or game shows. ...
Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ...
A sensor is a physical device or biological organ that detects, or senses, a signal or physical condition and chemical compounds. ...
It has been suggested that switching be merged into this article or section. ...
In aeronautics, canard (French for duck) is a type of fixed-wing aircraft in which the tailplane is ahead of the main lifting surfaces, rather than behind them as in conventional aircraft. ...
If an aft tail is used, the wing is designed to stall before the tail. In this case, the wing can be flown at higher lift coefficient (closer to stall) to produce more overall lift.
Military aircraft often have an angle of attack indicator which lets the pilot know precisely how close to the stall point the aircraft is.
Spoilers In most circumstances, a stall is an undesirable event. Spoilers, however, are devices that are intentionally deployed to create a carefully controlled stall over part of an aircraft's wing, in order to reduce the lift it generates, and allow it to descend without gaining speed. Airbus A319 with fully deployed combined airbrakes and spoilers In aeronautics a spoiler (sometimes called a lift dumper) is a device intended to reduce lift in an aircraft. ...
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