Helicopter (rotorcraft)

How does it work on a rotorcraft? Here are the relationships like on a propeller, just only not directed backwards, but downwards. With other words the rotor must press, so that the helicopter can lift off, at least the amount of air masses down, as the weight of the helicopter amounts to. Close to the ground, the so-called ground effect comes to help: Air accelerated downwards (created by rotor or wings) can not escape "simply" like in heigher levels and is kept by the ground (backed up).

One more indication, that the behaviour is in fact as described.