E-175 v2 VNAV will not engage

[Vorden]

I've followed the tutorial, I setup the FMS, I can see the altitudes on the legs page but whenever I press the VNAV button in flight, I immediately get "VNAV DISCONNECT" on the MCDU and the flight director switches to FPA.  The autopilot IS engaged when I do this, other modes such as V/S work just fine.  Any ideas why this might be happening or is this just a known bug?

Thanks,

  

Edited January 28, 2022 by Vorden

[sax702]

@Vorden, ensure your controller is calibrated. Also ensure you have set the desired altitude and that the FMC has all the required values for vertical navigation. 

[justplanemad]

On 1/29/2022 at 12:01 AM, Vorden said:

I've followed the tutorial, I setup the FMS, I can see the altitudes on the legs page but whenever I press the VNAV button in flight, I immediately get "VNAV DISCONNECT" on the MCDU and the flight director switches to FPA.  The autopilot IS engaged when I do this, other modes such as V/S work just fine.  Any ideas why this might be happening or is this just a known bug?

Thanks,

  

Can you paste a screenshot of the PFD when this comes up?

are you in LNAV mode (NAV button) laterally?

[Vorden]

Ok I think I figured it out, I didn't realise you have to set the entire route ahead of time, like landing runway and everything, once I did that it seems to be playing nice.  Certainly different from Boeing and CRJ FMSs for sure but that's why I'm doing this, to learn!  Thanks for the responses.

[justplanemad]

6 hours ago, Vorden said:

Ok I think I figured it out, I didn't realise you have to set the entire route ahead of time, like landing runway and everything, once I did that it seems to be playing nice.  Certainly different from Boeing and CRJ FMSs for sure but that's why I'm doing this, to learn!  Thanks for the responses.

Yeah VNAV is basically following the vertical component of the FMS flight plan… if there’s nothing in there - it doesn’t have anything to follow.    Boeing and Airbus the same IRL

if you haven’t programmed anything in FMS flight plan/route … just use FLCH (vertically) and HDG (laterally) instead for climb