Lateral stability and Spiral stability.
These two topics are easy to get muddled up.
So if I may a bit of non-type specific comment which I think may help this specific thread.
Lateral stability – kick Right rudder under any conditions of flight and if the aircraft rolls to the Right it has positive lateral stability and if it rolls Left it has negative lateral stability. This of course is the aircraft’s dihedral effect in action.
Spiral stability – put the aircraft in a bank and release the controls. If the aircraft slowly but surely increases its bank (it can take quite a while) then it is spirally unstable. If it tends to roll out then of course it is spirally stable.
But (and it is a very big but) with many aircraft one can demonstrate that the aircraft is both spirally stable and spirally unstable. How come? Well the spiral stability term is usually very weak, very weak indeed. This means that the slightest bit of residual aileron left when the controls are released will determine whether the aircraft rolls out or in to the spiral. So in the absence of a cockpit indicator that shows aileron angle allowing one to acurately set zero aileron one can be misled by the aircraft response.
Therefore the aileron control run sticktion, friction and breakout characteristics are very important in this context. This means that if you want to confuse your know-all mates just roll into a bank Left but finish with a tiny Right input as you release the controls and chances are the small residual Right aileron will stick on and cause the aircraft to roll out (spirally stable) then repeat the demo but release the controls without the touch of right aileron at the end as before and the opposite will happen.
Good for a beer.