Rich. With reference to the Airbus, unless all the engines seize (unlikely), then the continued rotation of the engine, and thus the Engine Driven Hydraulic Pumps, will provide enough hydraulic pressure to power the flight controls. If the emergency generator, should also fail then the batteries will still provide the required ergs to keep Prim 1 and Sec 1 (Flight Control Computers, A330/340) going and therefore a degraded regime Flight Control Law (Alernate Law).