The following discussion will not be able to reach to everyone here because of differing areas of experience, but to those who understand, it will help make the point-Timeliness is everything in control input, particularly when you are attempting to stabilize an unstable situation.
How many of you have flown tail draggers? Of those, how many have performed wheel landings? (I know of a couple of guys who pass the first criterea but not the second.) If you qualify for the second criterea, read on.
During a wheel landing the aircraft is (generally) flown down to the runway in a level attitude and the wheels are placed gently on the runway which if you are skillful will cause a slight pitch down as the momentum used in spinning up the wheels acts upon a point below the CG and creates a brief nose down pitch. This slight pitch down will help hold the aircraft on the runway and the aircraft can then be decelerated and transitioned to 3 point landing attitude. (Remember that tail draggers have the main landing gear positioned ahead of the CG)
If you reach the surface a little more firmly, the landing can be saved by a small amount of nose down input, but that nose down input must be timely. If you are half a second late, the aircraft will have skipped back into the air and your nose down input will create a second slightly more firm touchdown. If your response is again late, the result is a rapidly escalating series of bounces that would make a Kangaroo jealous.
At that point you must go around or crash.
A similar process is also at work on MD-11 landing accidents although there are many more factors causing the effect.
So what is the relevance to an Airbus flight control system? Simple. Timeliness is everything. When the aircraft's CG is aft, inherent pitch and yaw damping are reduced. Inherent stability is reduced. The aircraft gets its nice flying characteristics by virtue of timely computer directed control inputs. Let those control inputs be
delayed and Katy bar the door.
Discussion?