Expert: Ray Wilkinson - 5/3/2007

Question
hello MR RAY,
am doing a final year project about designing and innovation on A380 in Perth college.A380 used hydraulic system 5000psi,but what will happen if they used 3000psi,and what is the difference between them.and is there any disadvantages if they used 3000psi
thank you sir
farid

Answer
Hi Farid

I was in Toulouse a couple of years ago, and met one of the systems engineers - we spent a couple of hours looking at all of the A380 systems, including the hydraulics.
The A380 uses a 5000psi hydraulic system to save weight. As force = pressure x area, the same force can be obtained with smaller components. However, as the pressures are higher in the pipes and components they must be stronger than they would if they used 3000psi, so there's no weight saving in these. The weight saving comes in the smaller volume of fluid needed to run the system, though. The pipes are of smaller bore, and if I recall correctly it saves over a tonne over the entire aircraft.
Of course, the system is pre-set to use 5000psi maximum, so it isn't possible to use 3000psi accidentally. However, the drawback of using the higher pressure is that 5000psi components are not so readily available (only Concorde used 5000psi before, as far as I know). This means that all components, including pressure transducers, seals, pumps and so on, must be designed for the new pressure, and are not available off the shelf.

Regards

Ray