Originally Posted by waren9
FCOM 1.31.45 indicates that current G/S only is used to give the ETA for the next waypoint shown on the ND
Thats it !
Best exemple is to take a first waypoint something like 200 NM after takeoff and look at the difference of ETA between ND and MCDU.
Take that reading early after takeoff when GS is still pretty low and the difference will not be counted in minutes ... but in
minutes X 10
As soon as GS increases, difference shrinks.