Originally Posted by docromano
Does the DES mode have a vertical speed limit ?
DES mode operates within a 20 kt speed range around the managed target speed to maintain the descent path.
If the aircraft gets high on the computed descent path:
The speed will increase towards the upper limit of the speed range, to try to get back the aircraft on the path with IDLE thrust.
If the speed reaches the upper limit of that 20 kt speed range, THR IDLE is maintained, but the autopilot does not allow the speed to increase any more.