Downwash

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.[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 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.[1][3][4][5]

  1. ^ a b Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 172. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2
  2. ^ "ALC-104: Helicopter - General and Flight Aerodynamics". www.faasafety.gov. Federal Aviation Authority. Retrieved 18 January 2022.
  3. ^ Anderson, John D. (2004), Introduction to Flight (5th ed.), McGraw-Hill, pp. 352–361, §5.19, ISBN 0-07-282569-3
  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 9 February 2023.