FBW a32nx managed altitude activating V/S randomly?

Hi all!, I have a doubt I just can’t find the answer. When I try to engage managed altitude to a random altitude, sometimes (most times lately), the V/S selected altitude will randomly?¿ lit up, with also random fpm values, even though I didn’t touched the V/S knob and being in managed altitude. What’s more, sometimes, randomly?¿, I just can’t engage managed altitude no matter how many times I push the button (up position in sim), the orange dot doesn’t lit. If I wait a bit, then I might be able to engage managed mode again. Power in CLB.

When this happens, I can hear a sound advice and the PFD will show a blinking V/S (+/-fpm value) rectangle. Surprisingly, I seem to be always able to engage managed mode again only when descending from the actual altitude, I mean, as soon as I select a LOWER altitude than actual one, I can then engage managed altitude without the activation of V/S and the orange dot will lit again.

I have my throttle calibrated and no button assigned to these functions. Also, both FD are activated in FCU. SPD and HDG are managed and have a valid flight plan.

I really can’t understand this behaviour nor can’t find info about it. Any ideas what is going on. Maybe Im doing something wrong but I can’t manage to figure out what.


There are really several things that can come together. First of all, when you are in CLB or OP CLB and you dial in a altitude on the FCU that is below your current altitude then V/S mode engages with your current V/S. The same applies to DES / OP DES and you dial in an altitude on FCU that is higher than your current altitude. The blinking white box around V/S tells you that a mode reversion as described occurred.

Now to engage of CLB or DES and the orange dot. You can engage managed climb only when you’re in the right FMGC flight phase. It’s not possible to engage managed climb when you’re in decent. You can check the FMGC flight phase by clicking on PERF button on the MCDU. The page you’re in being on is the current phase.


very interesting information!, thanks a lot!. Let me make some checks and I will be back to comment about my findings.

Ok, back after the test I have to say you are absolutely right sir!. The problem was the different phase of the flight. In climb mode, I can no problem use managed climb and no V/S autoactivation will take place. In cruise, I can both, climb or descend in managed mode (make sense if ATC request a different altitude or the own crew) and once in descend, climb in managed is not possible, while descend actually is, make sense again. So out of the phases of the flight, going “againts” the nature of the phase is not possible in managed mode, BUT possible in selected (open) mode (V/S), which once again makes perfect sense.

Thanks a lot buddy!!