Being fairly ignorant I've never known why we always use the center autopilot on the 757/767, given all remain operative (and of course they all kick in on ILS).
I was asked this; "why", but have to confess I'm not sure. Has it anything to do with the C-autopilot answering to "hidden" center systems not visible on either side (FCC), has it "just always been like this" or is there an educated answer to this riddle?
Why don't we use L & R autopilots on a regular basis?
Thanks.