Recent content by ronaldleemhui

It's like a jet engine, or a rocket engine or throwing stones downward forcefully -- a certain momentum per unit time has to be shot down to overcome the effect of gravity on the helicopter. You can easily figure out what momentum flux is necessary, but depending on whether it is small amount...

To hover, a helicopter needs to provide a thrust by accelerating air downward. The thrust is proportional to the mass of downdraft per unit time times the velocity of the flow. If the rotors are extremely long and wide, the volume of downflow can be great. This allows the velocity to be low...