briefly explain how the A/P can simply disengage because of an overspeed, then climb to lose the airspeed excursion
As the Bus is a FBW aircraft, it is controlled by computers (obviously). The FBW technology means that there are effectively a few layers. Firstly, the control surface deflections are all computer controlled,. The aircraft has auto-trim (put the stick in a position, let it go and the aircraft will hold that attitude). The FBW is almost (simplistically) a dumb autopilot - it sets and hold control surface positions. It also has an ability (a bit smarter than dumb) to realise when things aren't right, and change control surface deflections to 'fix' the problem.
This FBW technology allows the aircraft to have a series of protections, one being an overspeed protection. When an overspeed is detected, the control surfaces are deflected by the flight computers to change the attitude and prevent an overspeed, just as a pilot would...
The autopilot is a layer above the FBW (the smart side of the aircraft). This operates like any autopilot, tracking, height conntrol etc etc.
When something is amiss (ie overspeed) the autopilot will drop out and the the FBW protections will kick in, to fix/control the problem.
So basically, the FBW is a 'basic' control, and the autopilot is a level above.
Hope this makes sense
