Originally Posted by chornedsnorkack
The problem with hydraulics seems demonstrated by 3 cases of airliners suffering total hydraulic failure despite redundancies.
A300 had a rocket in one wingtip. The aileron was served by three redundant hydraulic systems... so they all failed, and the aileron at the other wingtip as well as the aerodynamic controls of tail, though mechanically intact, became useless. DC-10 had engine shrapnel in tailfin... again, it was served by all three redundant hydraulic systems, so they all duly failed and ailerons, flaps et cetera became useless. B747 has rear bulkhead failure... again, it broke all 4 hydraulic systems, so that e. g. ailerons at the end of, mechanically intact, wings became useless.
How do airplanes deal with this kind of multiple common-cause failures?
The most common outcome is what happened to the JAL B747.