3 CMD switches, 747
Hello,
Mere PMDG 747X user, but having searched for 30 mins on PPRuNe, Google and the books supplied (PDF), I just can't find an answer:
What is the difference between the three CMD switches for AP functionality?
I understand the roll modes, the FCC connections, the fact all 3 are used for precision on approaches (due to rudder input) but simply: why select L C or R after take-off, for example? Is it simply: they all do the same thing until APP mode is activated then it needs all three? So, next question would be: why three? If one provides roll and pitch during regular flight phases, and another provides yaw (which one?), then why have three and not 2? I just don't see how the numbers add up and it's somewhat frustrating me that I can't find a clear answer anywhere.