and how a windmilling engine can generate 5000 p.s.i.....and is this normal operating px for the A380 ?/
Windmilling engines turn engine mounted hydraulic pumps. This will produce full hyd pressure at very low RPMs. Watch an airliner starting its engines. As the first engine starts to rotate, you can see the ailerons move up to normal posn.
It needs some speed to get full hyd flow, but the FCOM will tell you what this is. You will usually have full hyds available on windmilling engines down to a landing, but then must be careful as you slow down as the pressure will dissapear.