And these caused which accidents exactly? (And don't tell me Habsheim.)
Off the top of my head:
* Paris air crash (still can't decide which version of events is correct)
* A330 under-going autopilot test flights (AP couldn't be disengaged after a go-around and it stalled).
* Incident with A320 making un-commanded pitch maneuvers on approach, but thankfully didn't crash.
Most other aircraft with which I am familiar have three independent hydraulic systems, of which a single one allows the aircraft to be flown and landed, albeit with reduced manoeuverability.
Maybe it's a weight issue? Exec jets tend to only have two systems, I know the Fokker 70/100 has only two systems. It doesn't make them "less safe". The A380 only has two hydraulic systems (5000 psi systems), with electric backup!!
The DC-10 had three systems, but there were a couple of crashes where it didn't make any difference - all three lines were severed by a single event.
ECAM Actions.