RE: "Hydraulic backup" I want to clear something up here. It should be noted that on FBW aircraft,only the control,or shall I say command of flight control surfaces are electronic. The surfaces themselves are still physically actuated hydraulically. Instead of a cable or rod commanding a hydraulic power control unit metering valve as on a 'traditional' a/c,the said metering valve is moved by an electrical servo. So you see,it's not a matter of "cables vs. wires" actually moving flight controls as some think it may be. Yeah,the 319-321 horizontal stab and rudder have cable control for redundancy. (the brake metering valves are also cable operated BTW) When we first got the A319's,I made it a point to crawl up in the E&E bay to verify for my own curiosity that yes,there are cables on a 320 family a/c!