What are hydraulic pumps supposed to do? What they really do in vanilla FSX? Particulary there are 3 of those in 737: two engine HYD pumps and one electric. I guess they are supposed to be switched on during the flight, but I haven't noticed if turning them off affected the flight in any way.

Also can someone tell me why can't I download files? It say I must login/signup first even though I already am.