Originally Posted by
1201alarm
I never understood why Airbus is not improving their calculated managed descent profile. They do all kind of things for sustainability like green procedures etc, but the FMS still calculates a speed of around 145kt when intercepting the 3° ILS-GP instead of calculating with 185kt, which is the usual speed on A320fam to go onto the glide.
This difference in projected speed by the FMS and in reality flown speed makes for a managed descent profile that is roughly 1500 ft too low. So you can't really use managed descent with the in principal cool idea that you let the machine sort out wind variations by flying within a speed bracket instead of a speed bug.
I think that used to be true with the old style descent planning in the FMC. With DPO/CDO it is not anymore. Easy to see if it puts the flap 1 and 2 pseudo waypoints after glide slope intercept, which can and does happen. Having updated and recent descent winds helps with that, otherwise there is a chance that one might actually be higher than planned, not lower. Resulting either in an intercept from above or speedbrake usage.