What does downwash mean?
Downwash is the downward flow of air created by an aircraft wing, propeller, or rotor. As air passes over and around a lifting surface, the wing redirects some of it downward, producing a moving region of air with downward, and often curved or turbulent, components. The effect is familiar around helicopters: their powerful rotor downwash can raise dust, flatten grass, blow loose objects away, and create hazardous conditions for nearby aircraft. Fixed-wing aircraft also produce downwash, although it is generally less forceful than that of a helicopter rotor. In technical contexts, the term is more precise than a general reference to a downdraft because it identifies air movement produced by a particular aerodynamic component. Downwash is therefore chiefly an aviation and aerospace term, but it is useful beyond that field whenever one needs to describe the powerful downward currents that can accompany flying machines.
nounThe downward flow of air produced by an aircraft wing, propeller, or rotor. The flow may also be curved, turbulent, or capable of affecting objects, terrain, and other aircraft below the generating airfoil.
- The downward or downward-and-rearward flow of air generated by a lifting surface, propeller, or rotor.
"The helicopter's powerful downwash stirred dust across the landing area."
"The aircraft's downwash rippled the surface of the lake as it passed overhead."
"Pilots are trained to avoid another helicopter's rotor downwash."
The plural is used when referring to separate airflow effects generated by different aircraft, rotors, or aerodynamic configurations.
"The engineers compared the downwashes produced by the two rotor designs."
Downwash is the invisible aerodynamic hand of a wing or rotor, pushing air downward with enough force to stir dust, bend grass, or endanger a hovering aircraft.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does downwash come from?
Downwash is an English compound formed from the directional word down and wash, the latter evoking a moving flow of air or liquid. The term developed as specialized aeronautical vocabulary for airflow directed downward by a wing, propeller, or rotor. Its counterpart upwash was coined in parallel to describe the corresponding upward component of airflow around a lifting surface.
How downwash is actually used
This is a specialized aeronautical and aerospace term rather than ordinary vocabulary. It is especially common in discussions of rotorcraft, fixed-wing aircraft, wind tunnels, and flight safety.
Easily confused with downwash
A downdraft is any downward-moving current of air, whereas downwash specifically refers to airflow driven downward by a wing, propeller, or rotor.