The Coanda Effect has been discovered in1930 by the Romanian aerodynamicist Henri-Marie Coanda (1885-1972). He has observed that a steam of air (or a other fluid) emerging from a nozzle tends to follow a nearby curved surface, if the curvature of the surface or angle the surface makes with the stream is not too sharp.
The Coanda UAV, propelled by an electric engine, uses the Coanda effect to take off vertically, fly, hover and land vertically ( VTOL ). There is no big rotor like on an helicopter and the flight is very stable and safe for the surrounding.
More info at: jlnlabs.online.fr/gfsuav/index.htm