Originally Posted by
shortfuel
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.
Tried Full Speedbrakes in a 321 today.. Didn't slow down any faster, but its a very reassuring rumble....