Okcflyer wrote:Brakes are almost entirely pressure driven and require very little fluid flow (volume).
As stated, aircraft run constant pressure hydraulic systems. Flow rate (ie volume) through the pump / system depends on the “demand”.
Brake demand is next to nothing. Further, the demand is consumed from the accumulators storing the energy.
Does the 737 have a PTU between hyd systems to assist the electric pumps for high demand applications once in the air?
452QX wrote:Dash 8 APUs will give you nothing at all, you either need a DC power GPU or engines running. Brake pressure can come from a manual hand pump in the #2 engine
T prop wrote:DC GPU won't run the electric hydraulic pumps on the Dash, they're AC powered.
zeke wrote:T prop wrote:DC GPU won't run the electric hydraulic pumps on the Dash, they're AC powered.
Surely there is a static inverter off the DC bus, how else is the AC bus powered when in an emergency situation where the aircraft is just powered off batteries ?
T prop wrote:Yes, there are 3 inverters on board that provide single phase fixed frequency AC power for avionics. Heavy demand AC items like the standby hydraulic pumps, fuel pumps anti ice heating etc. use 3 phase variable frequency AC power that is only available with either engine running with it's propeller unfeathered...or if you have an AC GPU connected.
T prop wrote:[url][/url]452QX wrote:Dash 8 APUs will give you nothing at all, you either need a DC power GPU or engines running. Brake pressure can come from a manual hand pump in the #2 engine
DC GPU won't run the electric hydraulic pumps on the Dash, they're AC powered.
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