He and others believe that Airbus cannot correct the flaw without a major redesign. Planes already in service cannot be retrofitted with the correction.
The vertical stabalizer came off.
After loss of rudder control, it went into a spin, the spin made it shed parts all over the streets below, and crash.
Rudder control is what keeps an airplane from spinning. (invented by the Wright Brothers to keep their airplane from spinning.)
Composite/carbon fiber delamination?
As I recall, the problem seemed to be that the rudder controls required a lot of force on the ground or at very low speeds. In flight, they were much more responsive. The co-pilot was not familar with the Airbus. It was his responsibility to operate the rudder foot pedals and to perform pre-flight checks on them. One theory was that when performing the pre-flight check-out he came to believe that the rudder required a lot of force. In flight, when he needed to operate the rudder he literally stepped on the control pedal and when the rudder over responded he jammed them in the opposite direction. It was classic example of an underdamped control system "hunting". The loop gain was too high and the time delay too long. After reading about the Gimli Glider, I sure wouldn't want to be in an Airbus when someone is attempting a dead stick landing.