VNAV seems odd after the latest update

[UA124567]

Anyone else noticed that VNAV no longer provides accurate profile for descents after the recent update. I did couple of flights after the update and every time VNAV prediction seems to be odd, I had to manually take over to stay on profile yet VNAV tells me I'm too high. 

[richboy2307]

Hi @UA124567

There have been changes implemented to the VNAV based on feedback provided by IRL operators of the type. The computed VNAV infamously imperfect and "quirky" on the A300 so it may be what you are noticing.

However please submit specific examples of where you are facing this issue. In your report please include

• Full route including runways, SID/STAR/APP used
• CI, Weights (ZFW/Fuel), Cruise Alt
• Navdata source - Navigraph or Default
• Screenshots of your PFD/ND & MCDU F-PLN page & PROG PAGE (showing VDEV) in instances where you notice this issue

This will allow us to reproduce the scenario and make refinements if it is not working as intended.

Thanks!

[UA124567]

On 7/26/2024 at 12:32 PM, richboy2307 said:

Hi @UA124567

There have been changes implemented to the VNAV based on feedback provided by IRL operators of the type. The computed VNAV infamously imperfect and "quirky" on the A300 so it may be what you are noticing.

However please submit specific examples of where you are facing this issue. In your report please include

• Full route including runways, SID/STAR/APP used
• CI, Weights (ZFW/Fuel), Cruise Alt
• Navdata source - Navigraph or Default
• Screenshots of your PFD/ND & MCDU F-PLN page & PROG PAGE (showing VDEV) in instances where you notice this issue

This will allow us to reproduce the scenario and make refinements if it is not working as intended.

Thanks!

Hi there!

Thanks for your response, I was flying HYTHR3 arrival into KMEM with ILS 36L selected as my landing runway. Even today I was flying this arrival and VNAV got me down quite early - in fact I changed to V/S to better match the profile. 

- Route used "-N0466F340 DCT BACEN DCT BLOKR DCT BEKKI DCT ENL DCT NMANN HYTHR3" KORD/KMEM.  No SID on dep, STAR/APP as per above

- CI - I use 35 for all flights, (ZFW was around 120.0 Tonnes, Block fuel around 13.6 Tonnes), Cruising altitude FL340

- Nav data - I use Navigraph as my primary navigation database. 

Unfortunately no screenshots available for this flight however I got 1 more flight planned for this evening, If I encounter any anomalies then I shall take screenshot and post it here. 

[UA124567]

On 7/26/2024 at 12:32 PM, richboy2307 said:

Hi @UA124567

There have been changes implemented to the VNAV based on feedback provided by IRL operators of the type. The computed VNAV infamously imperfect and "quirky" on the A300 so it may be what you are noticing.

However please submit specific examples of where you are facing this issue. In your report please include

• Full route including runways, SID/STAR/APP used
• CI, Weights (ZFW/Fuel), Cruise Alt
• Navdata source - Navigraph or Default
• Screenshots of your PFD/ND & MCDU F-PLN page & PROG PAGE (showing VDEV) in instances where you notice this issue

This will allow us to reproduce the scenario and make refinements if it is not working as intended.

Thanks!

Okay I just did another flight from KMEM to KJAX and this time VNAV worked fine in showing the vertical profile - one thing to note however on T/D the target speed went back to 210 kts way below green dot speed at this stage, The 210 kts restriction doesn't come into effect until STAR termination point at CEDOT. I flew the OHDEA1 arrival for RNAV Z RWY 08. 

[richboy2307]

Thanks we'll look into it. Meanwhile if you have any other instances, please continue to report and try to include the screenshots as well where possible.

[jjcamb]

I have the same issue. Profile Descent worked very well before 1.1.2 update. Now seems completely broken for me. VDEV indication appears at least 20nm before TOD point indicated on ND. Example below is from an approach to KORD via WYNDE2 Arrival with a 5000ft crossing restriction manually entered at PAPPI. Calculated TOD point shown on ND appears to be in the correct location based on the 5000' constraint at PAPPI, but aircraft wants to start the descent 20nm out from this point. In the example below I am level still about 10mn from TOD, but VDEV is already off the scale indicating I am high on profile.

Even after initiating the descent at the TOD VDEV indication continues to indicate high on profile.

[richboy2307]

Hi @jjcamb

We have identified issues with VNAV when there are "MANUAL" or vector legs involved. For now if you're facing issues, we recommend to remove the discontinuits and MANUAL legs, and just be mindful of obeying them for ATC purposes.

Thanks!

[jjcamb]

4 hours ago, richboy2307 said:

Hi @jjcamb

We have identified issues with VNAV when there are "MANUAL" or vector legs involved. For now if you're facing issues, we recommend to remove the discontinuits and MANUAL legs, and just be mindful of obeying them for ATC purposes.

Thanks!

I tried the workaround you suggested on another STAR (KEWR FLOSI4) that I was having similar problems with and P.DES behaved as expected. 

Thank you