Originally Posted by ke_a320
that's because ;
when it comes to a roll control function and a deceleration funtion, the roll function has the priority. so the system limits the deployment of the spoilers. In emergency descent you have to disengage the autopilot and select full speed brakes.
That's not the reason. You can find the main reason in my previous post above.
All other Airbus FBW will give you full speedbrakes deflection if you require so with AP ON, so the roll function priority is not the reason.
As for "having to" disconnect the AP during EMER DES...you state that as if that was the manufacturer procedure...not really.