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altitude where the margin between level flight AoA and stall AoA is reduced. The high AoA capability of the aircraft provides a buffer for the pilot that makes stalling the airplane (which occurs when critical AoA is exceeded) more difficult. However, military aircraft usually do not obtain such high alpha in combat, as it robs the aircraft of speed very quickly due to induced drag, and, in extreme cases, increased frontal area and parasitic drag. Not only do such maneuvers slow the aircraft down, but they cause significant structural stress at high speed. Modern flight control systems tend to limit a fighter's angle of attack to well below its maximum aerodynamic limit.
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282:. These indicators measure the angle of attack (AOA) or the Potential of Wing Lift (POWL, or Lift Reserve) directly and help the pilot fly close to the stalling point with greater precision. STOL operations require the aircraft to be able to operate close to the critical angle of attack during landings and at the best angle of climb during takeoffs. Angle of attack indicators are used by pilots for maximum performance during these maneuvers, since airspeed information is only indirectly related to stall behavior.
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Some aircraft are equipped with a built-in flight computer that automatically prevents the aircraft from increasing the angle of attack any further when a maximum angle of attack is reached, regardless of pilot input. This is called the 'angle of attack limiter' or 'alpha limiter'. Modern airliners
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and begins to separate from the upper surface. On most airfoil shapes, as the angle of attack increases, the upper surface separation point of the flow moves from the trailing edge towards the leading edge. At the critical angle of attack, upper surface flow is more separated and the airfoil or
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much greater flyable 'true' alpha, up to over 45°, compared to about 20° for aircraft without these devices. This can be helpful at high altitudes where even slight maneuvering may require high angles of attack due to the low density of air in the upper atmosphere as well as at low speed at low
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representing the relative motion between the body and the fluid through which it is moving. Angle of attack is the angle between the body's reference line and the oncoming flow. This article focuses on the most common application, the angle of attack of a wing or airfoil moving through air.
641:(NATO) Advisory Group for Aerospace Research and Development, AGARDograph No. 300 Vol. 1 (AGARD AG-300 Vol. 1); "Calibration of Air-data Systems and Flow Direction Sensors"; Aeroplane and Armament Experimental Establishment, Boscombe Down, Salisbury, Wilts SP4 OJF, United Kingdom
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angle of attack". Below the critical angle of attack, as the angle of attack decreases, the lift coefficient decreases. Conversely, above the critical angle of attack, as the angle of attack increases, the air begins to flow less smoothly over the upper surface of the
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and the vector representing the relative motion between the aircraft and the atmosphere. Since a wing can have twist, a chord line of the whole wing may not be definable, so an alternate reference line is simply defined. Often, the chord line of the
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straight wing. Cambered airfoils are curved such that they generate some lift at small negative angles of attack. A symmetrical wing has zero lift at 0 degrees angle of attack. The lift curve is also influenced by the wing shape, including its
316:. Although the aircraft experiences high angles of attack throughout the maneuver, the aircraft is not capable of either aerodynamic directional control or maintaining level flight until the maneuver ends. The Cobra is an example of
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Above this critical angle of attack, the aircraft is said to be in a stall. A fixed-wing aircraft by definition is stalled at or above the critical angle of attack rather than at or below a particular
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of the airflow from the upper surface of the wing becomes more pronounced, leading to a reduction in the rate of increase of the lift coefficient. The figure shows a typical curve for a
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wing is producing its maximum lift coefficient. As the angle of attack increases further, the upper surface flow becomes more fully separated and the lift coefficient reduces further.
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varies with angle of attack. Increasing angle of attack is associated with increasing lift coefficient up to the maximum lift coefficient, after which lift coefficient decreases.
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that have fly-by-wire technology avoid the critical angle of attack by means of software in the computer systems that govern the flight control surfaces.
259:, the center of gravity of the aircraft and other factors. However, the aircraft normally stalls at the same critical angle of attack, unless
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Coefficients of drag and lift versus angle of attack. Stall speed corresponds to the angle of attack at the maximum coefficient of lift (C
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Some military aircraft are able to achieve controlled flight at very high angles of attack, but at the cost of massive
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as the reference line (and also as the longitudinal axis). Some authors do not use an arbitrary chord line but use the
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prevail. The critical or stalling angle of attack is typically around 15° - 18° for many airfoils.
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as the aircraft's wings are well beyond the critical angle of attack for most of the maneuver.
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is the angle of attack which produces the maximum lift coefficient. This is also called the "
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255:. The airspeed at which the aircraft stalls varies with the weight of the aircraft, the
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meaning the angle between the chord of an airfoil and some fixed datum in the airplane.
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is the angle between the sail's chord line and the direction of the relative wind.
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is chosen as the reference line. Another choice is to use a horizontal line on the
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instead of angle of attack. However, this can lead to confusion with the term
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111:, angle of attack specifies the angle between the chord line of the wing of a
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backcountry flying, aircraft may be equipped with the angle of attack or
547:"Fly-by-Wire Systems Enable Safer, More Efficient Flight | NASA Spinoff"
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Additional aerodynamic surfaces known as "high-lift devices" including
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USAF & NATO Report RTO-TR-015 AC/323/(HFM-015)/TP-1 (2001).
479:, McGraw-Hill Professional, first edition (September 1, 1990),
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where, by definition, zero angle of attack corresponds to zero
512:, Chapter 3 (8th edition), Pitman Publishing Limited, London
433:"Summary of Methods of Measuring Angle of Attack on Aircraft"
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Angle between the chord of a wing and the undisturbed airflow
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As the angle of attack of a fixed-wing aircraft increases,
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Calibration of Air-data
Systems and Flow Direction Sensors
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has a lower, flatter curve with a higher critical angle.
30:"Attack angle" redirects here. For rail technology, see
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In takeoff and landing operations from short runways (
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Relation between angle of attack and lift coefficient
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274:), such as Naval Aircraft Carrier operations and
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465:http://www.av8n.com/how/htm/aoa.html#sec-def-aoa
418:National Aeronautics and Space Administration
442:(NACA-TN-4351). NASA Technical Reports: 1–30
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135:Some British authors have used the term
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620:. Massachusetts Institute of Technology
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614:"HOW A SAIL BOAT SAILS INTO THE WIND"
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637:Lawford, J.A. and Nippress, K.R.;
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325:leading edge wing root extensions
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32:Attack angle (rail technology)
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414:"Inclination Effects on Lift"
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41:Angle of attack of an airfoil
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304:High Alpha Research Vehicle
141:riggers' angle of incidence
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618:Reports on How Things Work
360:, measures angle of attack
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431:Gracey, William (1958).
236:critical angle of attack
230:Critical angle of attack
155:Platform angle of attack
18:Critical angle of attack
533:"NASA Lift Coefficient"
495:Wolfgang Langewiesche,
475:Wolfgang Langewiesche,
369:Aircraft principal axes
298:at high angle of attack
280:Lift Reserve Indicators
75:{\displaystyle \alpha }
508:Kermode, A.C. (1972),
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658:Aircraft aerodynamics
379:Bernoulli's principle
302:Further information:
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91:on a body (often the
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663:Aircraft wing design
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510:Mechanics of Flight
440:NACA Technical Note
200:fixed-wing aircraft
130:coefficient of lift
113:fixed-wing aircraft
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137:angle of incidence
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374:Angle of sideslip
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16:(Redirected from
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329:fighter aircraft
318:supermaneuvering
314:Pugachev's Cobra
261:icing conditions
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180:lift coefficient
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118:root of the wing
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257:load factor
186:at a given
652:Categories
624:14 January
598:2022-06-02
556:2022-01-04
446:2024-02-22
400:References
224:swept wing
207:separation
178:A typical
99:) and the
93:chord line
87:between a
294:Su-27M /
83:) is the
70:α
352:See also
253:airspeed
211:cambered
188:airspeed
122:fuselage
342:sailing
336:Sailing
245:airfoil
216:airfoil
184:airfoil
97:airfoil
582:"DTIC"
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499:, p. 7
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327:allow
101:vector
95:of an
668:Kites
592:(PDF)
585:(PDF)
436:(PDF)
296:Su-35
240:stall
222:. A
198:of a
85:angle
61:, or
626:2012
514:ISBN
481:ISBN
276:STOL
272:STOL
234:The
194:The
340:In
167:MAX
107:In
55:AOA
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165:L
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