How's this for a mind-bender...
At sea level air weights 0.0813 lb per cubic foot. At that weight it would take 61,500 cu ft of air (at sea level) to equal the weight of a 5000 lb helicopter. That's the amount of air it would take to fill a box fifty feet to a side and twenty five feet tall. That's the amount of air the chopper has to have in motion at any given moment just to support it's own weight in a hover.
Hmm... any of you erronawtikul types know what the actual pressure is on the high- and low-pressue sides of the rotor?
Brad
p.s. - yes, I am constantly thinking about irrelevant crap like this...