Question about Autopilots

[Guest alexhn]

One thing about the autopilot, and that is, why are there two? CMD A and CMD B. I know vaguely that you enable CMD B as well for ILS landings or something but thats it.In addition, why are there two CWS. ie CWS A and CWS B. I know what they do but what is the purpose for having 2?

[Guest Erups]

>>what they do but what is the purpose for having 2?Redundancy.They constantly confront and exchange data to ensure the maximum precision.They correspond to two (both logically and phisically) different computers.

[Guest hlm65]

You'll engage both A/Ps ONLY when performing an autoland. As Claudio said, the purpose is redundancy/safety (required with the very strict accuracy requirements of an autoland): each a/p has its own separate computer; during an autoland with both APs engaged, they will compare there data and performance.The 2 CWS are there because you have 2 A/P computeres and there's a sperate CWS button for each AP.

[Guest oldngray]

... why are there two?In the real world a pilot cannot legally attempt an autoland unless both computers are operating properly.... 300 souls on board... if system "A" fails and there is no backup to take over seamlessly... does one want the aircraft to autoland without guidance?

[Guest alexhn]

thanks everyone so much for your replies :)now i understand the concept more