FSX - HYD pumps.

[Lomaster]

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.

[mikeandpatty]

Hydraulics on a larger airplane typically run the flight controls using hydraulic actuators (elevator, rudder, ailerons, spoilers, landing gear, flaps, brakes). Engine driven pumps provide independent pressure in case one engine is shut down, the remaining one can still actuate most systems. Typically the engine driven pumps are on with the engine running. They cannot be shut down, but part of the hydraulic circuits that they pressurize can be isolated if their is a leak in a pressure line.

Electric punps are usually a "last ditch" backup system that help out if one engine pump is lost.

Brakes may be powered by a main hydraulic circuit, but have an independent hydraulic reservoir and air accumulator as an emergency backup.

I am not familiar with the exact 737 series setup, but I would guess all should be on. If you turn one off as a test, try moving the controls, gear, flaps and see if the switches actually do something. Also see if you get a warning or caution light