Dani
So, if they are right, the forward motion is bigger than the twisting. That couldn't be the case if in a flat spin.
Anyway, the discussion about spin or not is useless. Because it doesn't deliver a theory about the cause, only about the outcome. We are not interested how they crashed, but why they did (Boac, you remember our discussion in the THY/AMS thread?)
Dani
You are making statements that are totally unsupported.
What evidence is there that the rotational element in a flat spin is greater than the forward. None at all. You just 'invented' that 'fact'. A flat spin can easily have a fairly modest rotational element if the autorotational forces are small due to a number of factors. Speculation on a rate of rotation is fruitless, it is slower for larger aircraft but we cannot say how slow.
Your repeated assertion that large aircraft cannot flat spin is frankly valueless. You have no evidence to support that. The dynamic forces that create a flat spin in small aircraft can easily be scaled up. Also, several large aircraft have entered spins. If you enter a spin then all that is required to make it a flat spin is longitudinal force (e.g. power).
So 1. Large aircraft can spin. Many have. 2. A spin WILL flatten if you apply longitudinal force.
Therefore it is feasible to flat spin a large aircraft.
I am not saying that this is what happened but it would be foolish to dismiss it.