Let's say that we want to build a helicopter, if we want it to hover in the air then the pushing force of it's fan must equal the force of gravity but in the opposite direction, so how do we calculate the pushing force of a specific fan? What information do we need to know? Like it's rotation rate and it's area.
Also, I've searched about this but I didn't find a clear equation or something, but some people were talking about some variables, like "air going through the fan" what does that mean? And also the "angle of the blades" what is it?
Finally I have another question, is it a requirement for the fan to consists of blades and not a one full circle?