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In aeronautics, downwash is the change in direction of air deflected by the aerodynamic action of an airfoil, wing, or helicopter rotor blade in motion, as part of the process of producing lift.^[1] In helicopter aerodynamics discussions, it may be referred to as induced flow.^[2]

Lift on an airfoil is an example of the application of Newton's third law of motion – the force required to create the downwash is equal in magnitude and opposite in direction to the lift force on the airfoil. Lift on an airfoil is also an example of the Kutta-Joukowski theorem. The Kutta condition explains the existence of downwash at the trailing edge of the wing.^[1]^[3]^[4]^[5]

References

^ ^a ^b Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 172. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2
^ "ALC-104: Helicopter - General and Flight Aerodynamics". www.faasafety.gov. Federal Aviation Authority. Retrieved 18 January 2022.
^ Anderson, John D. (2004), Introduction to Flight (5th ed.), McGraw-Hill, pp. 352–361, §5.19, ISBN 0-07-282569-3
^ "The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down." In: Langewiesche, Wolfgang (1990), Stick and Rudder: An Explanation of the Art of Flying, McGraw-Hill, pp. 6–10, ISBN 0-07-036240-8
^ "Downwash Effects on Lift". nasa.gov. Retrieved 4 March 2015.

[Crane-1] Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 172. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2

[ALC104-2] "ALC-104: Helicopter - General and Flight Aerodynamics". www.faasafety.gov. Federal Aviation Authority. Retrieved 18 January 2022.

[Anderson_Flight_5.19-3] Anderson, John D. (2004), Introduction to Flight (5th ed.), McGraw-Hill, pp. 352–361, §5.19, ISBN 0-07-282569-3

[Langewiesche_6_10-4] "The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down." In: Langewiesche, Wolfgang (1990), Stick and Rudder: An Explanation of the Art of Flying, McGraw-Hill, pp. 6–10, ISBN 0-07-036240-8

[5] "Downwash Effects on Lift". nasa.gov. Retrieved 4 March 2015.

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@@ Line 1: / Line 1: @@
 [[File:US Navy 050419-N-5313A-414 Search and Rescue (SAR) swimmers attached to the Kearsarge Expeditionary Strike Group conduct search and rescue training during routine helicopter operations.jpg|thumb|upright=1.14|The effect of downwash from a hovering [[Sikorsky Seahawk]] is clearly visible on the surface of water below.]]
-In aeronautics, '''downwash''' is the change in direction of air deflected by the aerodynamic action of a [[wing]], or [[helicopter rotor]] blade in motion. Downwash is present in the air approaching the wing, and between the [[wingtip vortices]] behind the wing, and is directly associated with [[lift-induced drag]]. Outside the wingtip vortices are regions of upwash; the momentum of the air in the upwash is equal to the momentum of the air in the downwash so neither upwash nor downwash is a source of lift on the wing. A wing of infinite span is able to generate lift but does not experience downwash or upwash.<ref>John D. Anderson (1984), ''Fundamentals of Aerodynamics'', Section 5.1, McGraw-Hill</ref>
+In aeronautics, '''downwash''' is the change in direction of air deflected by the aerodynamic action of an [[airfoil]], [[wing]], or [[helicopter rotor]] blade in motion, as part of the process of producing [[lift (force)|lift]].<ref name="Crane">Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 172. Aviation Supplies & Academics, 1997. {{ISBN|1-56027-287-2}}</ref> In helicopter aerodynamics discussions, it may be referred to as '''induced flow'''.<ref name="ALC104">{{cite web |title=ALC-104: Helicopter - General and Flight Aerodynamics |url=https://www.faasafety.gov/gslac/alc/course_content_popup.aspx?cID=104&sID=451 |website=www.faasafety.gov |publisher=Federal Aviation Authority |access-date=18 January 2022}}</ref>
+Lift on an airfoil is an example of the application of [[Newton's laws of motion#Newton's third law|Newton's third law of motion]] – the force required to create the downwash is equal in magnitude and opposite in direction to the lift force on the airfoil. Lift on an airfoil is also an example of the [[Kutta-Joukowski theorem]]. The [[Kutta condition]] explains the existence of downwash at the [[trailing edge]] of the wing.<ref name="Crane" /><ref name="Anderson_Flight_5.19">{{citation
-In helicopter aerodynamics discussions, downwash may be referred to as '''induced flow'''.<ref name="ALC104">{{cite web |title=ALC-104: Helicopter - General and Flight Aerodynamics |url=https://www.faasafety.gov/gslac/alc/course_content_popup.aspx?cID=104&sID=451 |website=www.faasafety.gov |publisher=Federal Aviation Authority |access-date=18 January 2022}}</ref>
+| last=Anderson
+| first=John D.
+| title=Introduction to Flight
+| year=2004
+| edition=5th
+| publisher=McGraw-Hill
+| isbn=0-07-282569-3
+| pages=352–361, §5.19
+}}</ref><ref name=Langewiesche_6_10>"The main fact of all heavier-than-air flight is this: ''the wing keeps the airplane up by pushing the air down.''" In: {{citation
+| first1=Wolfgang
+| last1=Langewiesche
+| title=Stick and Rudder: An Explanation of the Art of Flying
+| publisher=McGraw-Hill
+| year=1990
+| isbn=0-07-036240-8
+| pages=[https://archive.org/details/stickrudderexp00lang/page/6 6–10]
+| url-access=registration
+| url=https://archive.org/details/stickrudderexp00lang/page/6
+}}</ref><ref>{{cite web |url=http://www.grc.nasa.gov/WWW/k-12/airplane/downwash.html |title=Downwash Effects on Lift |work=nasa.gov |accessdate=4 March 2015}}</ref>
 ==See also==