Coanda states the adherence of airflow to a curved surface.
Without airflow there is no Coanda and subsequently no Newtonian reacting force which is created by changing the direction of a moving mass (air in this case).
In the hover, Coanda explains the downwash of the propeller, and the resulting lift, now called thrust.
The downwash flows over the control surfaces, where again Coanda explains the resulting control forces.
No downwash, no hover. To see Coanda in action, shut down the engine in the hover, and see what happens. Do this high enough, so true airspeed by plane motion can take over before you crash.