The A320 is almost never field limited. So Vspeeds for a FLEX take-off are optimized/increased (improved climb in non-airbus speak) in order to maximize the FLEX temperature. i.e. a higher V2 will result in a a better climb gradient thus a higher climb limited TOW. That's why you can see very high Vspeeds on long runways.
If you use TOGA, there is no FLEX temp to be maximized. So the Airbus philosophy is to have the lowest speeds possible. (tirewear, ASDA, brakes etc). Also note that when Tmaxflex (ISA+60 for most CFM's, ISA+53 for IAE) is achieved there is no further Vspeed optimization. So in very non-limiting cases you CAN see FLEX with lower than usual Vspeeds or even 'TOGA speeds'.
You can use TOGA with FLEX speeds, no problems. (think about it: you would consider selecting TOGA when N-1).
Last edited by OPEN DES; 21st Jun 2009 at 12:13.