A320 Neo V2 VNAV not working

[Bazz]

Hello, Great product and really enjoying thank you

VNAV seems to work well for the most part however I am not sure about a couple of things

Firstly in the example in the manual it says to enter the FAF altitude in the FCU at the top of descent.  When I do this it does not recognise the waypoint altitude constraints in between TOD and FAF.

Secondly I found this when I did a small flight from YBBN to YBCG RNAV 13W where the constraints are as follows and the MCDU Flight Plan calculated altitudes 

 

VAPMU Constraint 2500 A320 MCDU Flight Plan page calculated 1828

CG017 Constraint 2500 A320 MCDU Flight Plan page calculated 1678

I am wondering if you can comment on this please

Kind regards

Barry C

 

[richboy2307]

Hi @Bazz

On 6/4/2024 at 12:45 PM, Bazz said:

Firstly in the example in the manual it says to enter the FAF altitude in the FCU at the top of descent.  When I do this it does not recognise the waypoint altitude constraints in between TOD and FAF

So it shouldn't ignore your constraints in a managed descent (DES). It would however ignore them in an Open Descent (OP DES).

Normally you would see on the bottom right of your PFD, the target ALT, same as set on your FCU in blue colour. If it is limited by any constraint, it would show up in Purple with the ALT of that constraint.

So when you are noticing this issue, could you please provide a screenshot of your PFD,ND, FCU and also the MCDU (FPLN Page)?
 

 

On 6/4/2024 at 12:45 PM, Bazz said:

Secondly I found this when I did a small flight from YBBN to YBCG RNAV 13W where the constraints are as follows and the MCDU Flight Plan calculated altitudes 

 

VAPMU Constraint 2500 A320 MCDU Flight Plan page calculated 1828

CG017 Constraint 2500 A320 MCDU Flight Plan page calculated 1678

Could you share the full route that you tried? Also a screenshot of your INIT A/B pages or list the values used.
I have just tried with a couple of randomly generated dispatches via simbrief and not exactly seeing your calcs.

Here's an example:

 

From this, I can see for YBCG RNAV-W RWY 14, the following computed path:

Do note that VAPMU is programmed in this procedure as 2500ft or above alt constraint by the navdatabase itself, and we cannot control that. So given this restriction, it has computed the path (within margin of error) whilst still abiding by the constraints. 

I am not able to reproduce the erroneous path currently, but would love to try with the data you are using to see if we can reproduce the problem, and thereby improve on it.

Thanks!

[Bazz]

Hello and thank you sincerely for your help

 

I tried again and got the same erroneuos result, just to check what I had done.

So then I managed to get it right by playing around with the arrival page.  Previously I had not entered a SID or a STAR and only entered RNAV 14 W, nothing else.

This time I went into arrival and selected RNAV 14W then selected VAPMU as a via and it then it chose and displayed the correct constraints.

However it also dropped IRPOD of the FPLAN page, interesting, it seems it should be where "LIM" is

So wondering if you can let me know what you entered on the arrival page, because that changed a lot which makes sense.

It also wanted to change the cruise altitude to FL10 so I went in and changed it back to FL4

Really appreciate your help, thank you again

 

[Azlog]

IRPOD is the first waypoint on the ILS/LOC approach. An RNAV without a transition would perhaps default to that as the straight in waypoint in the absence of a VIA

New cruise altitude happens if you set an altitude on autopilot panel that is higher than the cruise altitude that was set on the INIT page

[richboy2307]

On 6/11/2024 at 3:18 PM, Bazz said:

So wondering if you can let me know what you entered on the arrival page, because that changed a lot which makes sense.

The only thing I had done was select RNAV-W 14 via VAPMU transition.

 

On 6/11/2024 at 3:18 PM, Bazz said:

However it also dropped IRPOD of the FPLAN page, interesting, it seems it should be where "LIM" is

The waypoint IRPOD was already in my flightplan as the last enroute waypoint (as seen on simbrief screenshot). Selecting a procedure simply adds the points starting from VAPMU after it. IRPOD remains as a waypoint before it. (Ignore the EFOB - that is just because I was not at the departure airport when I took this screenshot).

On 6/11/2024 at 3:18 PM, Bazz said:

It also wanted to change the cruise altitude to FL10 so I went in and changed it back to FL4

As Azlog mentioned above, this is likely because you dialed 10,000ft on the FCU  and pushed in the knob at some point.  As the new managed altitude was higher than previously planned CRZ Alt, it will update to the new CRZ FL as entered on the FCU (10,000ft in this case).

 

[Bazz]

You and your product, and your support are amazing thank you