Downwash

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

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 an airfoil, wing, or helicopter rotor blade in motion, as part of the process of producing lift.<ref name="Crane">Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 172. Aviation Supplies & Academics, 1997. Template:ISBN</ref> In helicopter aerodynamics discussions, it may be referred to as induced flow.<ref name="ALC104">Template:Cite web</ref>

Lift on an airfoil is an example of the application of Newton's third law of motion – the force required to deflect the air in the downwards direction 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">Template:Citation</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: Template:Citation</ref><ref>Template:Cite web</ref>

See also

• Brownout (aeronautics)
• Jet blast
• Slipstream
• Wake turbulence
• Wingtip vortices