Heres one for the Aerodynamic experts among you:
How do you calculate how much downwash ie air pressure and how much is lift that keeps the helicopter in the air?
Now we all know that lift is 1/3 pressure(underneath) and 2/3 low pressure (on the top!) so you must have a third force involvement, because when you have pressure underneath pushing up and at the same time pressure pushing down, they must influence each other to some degree.
Was I asleep in Aerodynamic theory? Am I asking a stupid question?