Originally Posted by Mb2002
the FMGC calculates the speeds based on estimated landing weight until approach phase is activate, from which point actual GW is used
Right, just found the reference
anyway, F speed will change at about 1 or 2 kt per ton, maximum. The difference for that reason should never be 15 kt!
The OP question was about the diff btw F speed on APPR and GA pages...not F speed before and after APPR phase activation.
On the A330 (don't remember on the A320), check your F speeds in cruise for APPR and GA page, you will see around 15 knot difference. If I am not mistaken, that's what the OP is asking about.