Thanks, I think now I have the answer. FLew many times TAP TriStar500s as a pax and they hadn't those vortex gennerators.
When you say digital vs analogue AFCS can we distinguish it externaly by looking to the glareshield?
Is this the analogue one:
http://www.airliners.net/open.file/423373/L/
and this the digital one:
http://www.airliners.net/open.file/458794/L/
???
Then, I think all standard lenght TriStars had analogue AFCS but had no vortex generators since they were bigger and weren't fitted with ACS which supposedly was a system that could aggravate the jet upset phenomena.
Sorry if I'm saying a big mistake
