which hydraulic system is being used during normal operation on an airbus aircraft?
 

I've noticed that there are 3 hydraulic systems mounted on every airbus. Do they all work together to provide support for the aircraft or only one of them is active each time while the other 2 are in standby mode?

A320 version of Airbus hydraulics
 

All three systems work regularly (whenever there is demand) to maintain 3000psi.

Each control surface or hydraulic user has a primary hydraulic source and some systems have secondary or tertiary sources.

Spoiler no 3 has blue only but the rudder has all three sources whereas the ailerons are powered by the green and blue systems, with the left aileron having blue as it's primary and green on standby and the right aileron having green as it's primary and blue as the standby.

The hydraulic architecture diagram in the back of the QRH explains a lot of it.

All three work in unison for redundancy (same with Boeing). Most flight controls have feeds from just 2 systems, the rudder and elevators being the exception. The RAT only powers the yellow system on the Airbus IIRC.

A380 only has 2 hydraulic systems btw

Let's start with the A300, I believe all twin Airbus are the same. Electrically the Green (center system) has a engine pump on both engines, the left engine has a Blue pump and the right engine has a yellow pump. This is normal operation with engines running. The green system is the most critical, it has 2 transfer pumps that will power B&Y (non reversible motor pumps). The green system has two electric pumps that will power B&Y w/o engines running, If you lose an engine the Green will power the others. On the ground of course the Green sustains all.

grounded27
As long as you stay on ground you will be safe.

Thank you everyone for the thorough explanation!!

The small buses are all the same, the larger twin engine buses are different because of ETOPS certifications.

A300 might be designed for ETOPS (stand to be corrected...) but it is not the same as the A320-family.

A320 is ETOPS capable.

A310 and A300-600 as well etops. A300 (b4) was before etops.

A300B4 has 10 hydraulic pumps in total.

Do you know them all?

My flight engineer did, for sure.

A300
 

Really? Right engine has a G&Y pump, left has a G&B pump. Electrical 2 each green pumps. The G will drive the B&Y. Have the feeling I must keep it simple for this crowd.

I am flying Boeings now for more than ten years. You sure forgive me this memory slip, no?
I think I am glad I do not mix up now the CV580, SF340, EMB120, HS747, Viscount 700, L188 and the classic Airbusses with the 737, no?

On A320 No1 EDP drives green system, No2 EDP drives yellow system also it has yellow electric pump, between Green and Yellow there is a PTU that comes on automatically in case of low pressure in either system. Blue hydraulic system is by electric pump and has RAT in emergency. They all work all the time and operate their respective services.