Editing Angle of attack (section)

{{Short description|Angle between the chord of a wing and the undisturbed airflow}}
{{Redirect|Attack angle|rail technology|Attack angle (rail technology)}}

[[File:Airfoil angle of attack.jpg|thumb|upright=1.25|Angle of attack of an airfoil]]

In [[fluid dynamics]], '''angle of attack''' ('''AOA''', '''α''', or '''<math>\alpha</math>''') is the [[angle]] between a [[Airfoil#Airfoil terminology|reference line]] on a body (often the [[chord (aircraft)|chord line]] of an [[airfoil]]) and the [[vector (geometry)|vector]] representing the relative motion between the body and the fluid through which it is moving.<ref name="nasa">{{cite web|url=https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/foilinc|title=Inclination Effects on Lift|website=National Aeronautics and Space Administration|date=2018-04-05}}</ref> 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.

In [[aerodynamics]], angle of attack specifies the angle between the chord line of the wing of a [[fixed-wing aircraft]] 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 [[Wing root|root of the wing]] is chosen as the reference line. Another choice is to use a horizontal line on the [[fuselage]] as the reference line (and also as the longitudinal axis).<ref>{{cite journal |title=Summary of Methods of Measuring Angle of Attack on Aircraft |url=https://ntrs.nasa.gov/api/citations/19930085167/downloads/19930085167.pdf |issue=NACA-TN-4351 |journal=NACA Technical Note |first=William |last=Gracey |year=1958 |pages=1–30 |publisher=NASA Technical Reports |access-date=2024-02-22}}</ref> Some authors<ref name="SHIF">John S. Denker, ''See How It Flies''. http://www.av8n.com/how/htm/aoa.html#sec-def-aoa</ref><ref name="SnH">Wolfgang Langewiesche, ''Stick and Rudder: An Explanation of the Art of Flying'', McGraw-Hill Professional, first edition (September 1, 1990), {{ISBN|0-07-036240-8}}</ref> do not use an arbitrary chord line but use the [[zero lift axis]] where, by definition, zero angle of attack corresponds to zero [[Lift coefficient|coefficient of lift]].

Some British authors have used the term [[angle of incidence (aerodynamics)|angle of incidence]] instead of angle of attack.<ref>Wolfgang Langewiesche, ''Stick and Rudder: An Explanation of the Art of Flying'', p. 7</ref>  However, this can lead to confusion with the term ''riggers' angle of incidence'' meaning the angle between the chord of an airfoil and some fixed datum in the airplane.<ref>Kermode, A.C. (1972), ''Mechanics of Flight'', Chapter 3 (8th edition), Pitman Publishing Limited, London {{ISBN|0-273-31623-0}}</ref>