Why is the A320 ignoring speed constraints?

[rlanssiers 0]

Short test flight at 5000 ft. Speed constraints manually entered via MCDU before flight at several fixes to stay at 210 kts but the A320 ignores them and accelerates to its maximum of 250 kts below 10000 ft.

[Emi 5161]

Which version do you have installed?

[rlanssiers 0]

Pls. find below the configuration I am using:

• Windows 7 Home Premium 64 bit SP1
• Prepar3D 1.4.4747.0
• Airbus X A320/A321 1.16

[Emi 5161]

Can anyone confirm that this happens with 1.16?

I know we have had this bug in earlier versions, but in 1.16 it has certainly been fixed since a loooooong time.

[Patrick1246 353]

because you are in Cruise phase

SPEED CONSTRAINT
Speed constraints may be attached to specific waypoints in the climb, descent or approach
phases. To meet the speed constraint, the aircraft must fly over the waypoint with a speed equal or
less than the speed constraint

[rlanssiers 0]

Hi Patrick,

Thanks for pointing out the cruise phase but even when I keep the plane in climb phase, constraints are not working as expected.

What happens then is, that the aircraft slows down to be at 210 kts when reaching a waypoint but immediately after the waypoint speeds up to 250 kts to slow down again just a little bit later to be at 210 kts again at the next waypoint.

Maybe this is what the real aircraft would do but I doubt it?

Rony

[Cheyenne Chief Pilot 829]

I doubt it, too ...