Originally Posted by ChrisVJ
..... after all we hear often enough of physical control systems being jammed, either by mis-installation or foreign objects or by minor structural damage that would not in itself bring an aircraft down.
I forgot to mention....
On Concorde it was belts
and braces
and an elastic band
and a piece of string....
Three hydraulic systems, two separate electrical signalling channels, mechanical backup (rods and cables) and finally, if the mechanical controls were jammed, strain gauges on the controls, that detected the forces being exerted by the pilots and controlled the system that way.
Don't know what's on more recent aircraft.
CJ