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| − | '''Angle of attack''' ([[Greek alphabet|Greek]] alpha) is a term used in [[ | + | '''Angle of attack''' (<math>\alpha</math>, [[Greek alphabet|Greek]] alpha) is a term used in [[aerodynamics]] to describe the [[angle]] between the [[wing]]'s [[chord (aircraft)|chord]] and the direction of the relative [[wind]], effectively the direction in which the [[aircraft]] is currently moving. The amount of [[lift (force)|lift]] generated by a wing is directly related to the angle of attack, with greater angles generating more lift (and more [[drag (physics)|drag]] as it increases the frontal area). This remains true up to the [[stall]] point, where lift starts to decrease again because of [[airflow separation]]. Planes flying at high angles of attack can suddenly enter a stall if, for example, a strong wind gust changes the direction of the relative wind, an effect that is seen primarily at low speeds. |
| − | Using a variety of additional aerodynamic surfaces — known as high-lift devices — like [[ | + | Using a variety of additional aerodynamic surfaces — known as high-lift devices — like [[leading edge extension]]s, [[fighter aircraft]] have increased the potential flyable alpha from about 20° to over 45°, and in some designs, 90° or more. That is, the plane remains flyable when the wing's chord is at right angles to the direction of motion. |
Some aircraft are equipped with a built-in flight computer that automatically prevents the plane from lifting its nose any further when the maximum angle of attack is reached, in spite of pilot input. This is called the angle of attack or alpha limiter. The pilot may disengage the alpha limiter at any time, thus allowing the plane to perform tighter turns (but with considerably higher risk of going into a stall). A famous example of this is [[Pugachev's Cobra]], a maneuver which can only be performed by the [[MiG-29]], the [[Su-27]]/[[Su-33]] and some prototype Western aircraft. It consists of the pilot disengaging the alpha limiter and pulling the aircraft to a 90°–110° angle of attack, then back down to zero. In a properly performed Pugachev's Cobra, the plane maintains a straight and level flight throughout the maneuver. | Some aircraft are equipped with a built-in flight computer that automatically prevents the plane from lifting its nose any further when the maximum angle of attack is reached, in spite of pilot input. This is called the angle of attack or alpha limiter. The pilot may disengage the alpha limiter at any time, thus allowing the plane to perform tighter turns (but with considerably higher risk of going into a stall). A famous example of this is [[Pugachev's Cobra]], a maneuver which can only be performed by the [[MiG-29]], the [[Su-27]]/[[Su-33]] and some prototype Western aircraft. It consists of the pilot disengaging the alpha limiter and pulling the aircraft to a 90°–110° angle of attack, then back down to zero. In a properly performed Pugachev's Cobra, the plane maintains a straight and level flight throughout the maneuver. | ||
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| + | ==Sailing== | ||
| + | In [[sailing]], the '''angle of attack''' is the angle between a sail and the direction of the wind. The physical principles involved are the same as for aircraft. See [[points of sail]] | ||
==See also== | ==See also== | ||
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*[[Lift (force)]] | *[[Lift (force)]] | ||
| − | + | ''This entry is from Wikipedia, the leading user-contributed encyclopedia.'' | |
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