AA587 + Air Transat Connection: Some speculation:
I certainly hope that the investigators of the Air Transat incident will probe deeper and give a possible link to these two incidents - or at least give the NTSB investigators thought to reconsider AA587 findings.
The Air Transat rudder event occurred when the aircraft was in cruise flight at FL350. There was a strong initial yaw motion. A flight attendant standing in the flight deck was thrown to one side. The event was not precipitated by pilot input and was not reacted to (no counter input). It is possible that the rudder started to delaminate on one side causing the rudder to push over. In this case the rudder subsequently disintegrated due to air loads and drag as is evidenced by the pictures. The vertical stab did not fail because there was no rudder reversal input nor any preexisting weakness in the stab.
In the AA587 incident it is possible that the same or at least similar failure occurred. The aircraft entered an area of turbulence caused by a preceding aircraft. I speculate that coincidently the rudder started to delaminate at that point. There was an initial rudder hard over which was countered by a rudder input by the First Officer. The flight data recorder showed two inputs and Airbus has latched onto the idea of rudder reversal causing stab failure. I contend or at least ruminate that the first rudder input was a feedback from the delamination rudder hardover and the second input was the FO's correct reaction. The stab failed due to a preexising weakness caused by some other event or engineering weakness.
The American crew was up at the controls as they were in the initial climb phase and reacted correctly. The Transat crew was in cruise and in a more relaxed state. Different mode of flight and different reaction and preparedness. That is a fact of airline flying.
The A310 and A300-600 are very similar machines. One of the exceptions is length. The increased length of the 300 and the greater moment arm force on the tail in combination with the rudder input could be the difference in the two cases.
This is just my opinion. But in respect to the American crew and the victims of that accident it is worth looking into.