A310 ( MSFS ) VNAV during descend

[Beardyman 604]

I have done 3 flights so far and not even one-time VNAV was working as intended.

Initially i see descend scale and marker but after a while marker disappears and plane continue level flight, so i must descend manually.

I think that Inibuilds should focus on correcting VNAV and LNAV ( plane overshoots sharp turns quite seriously ) as plane with present issues do not fall nicely into study level sim category.

[Mace 1,902]

19 minutes ago, Beardyman said:

I have done 3 flights so far and not even one-time VNAV was working as intended.

Initially i see descend scale and marker but after a while marker disappears and plane continue level flight, so i must descend manually.

I think that Inibuilds should focus on correcting VNAV and LNAV ( plane overshoots sharp turns quite seriously ) as plane with present issues do not fall nicely into study level sim category.

Are you sure VNAV and LNAV aren't working as intended?  This isn't a modern airplane.  There are times where frequently I'll have to drop out of PROFILE mode and into FL CH with managed speed to correct the descent profile.  Then I can re-enter PROFILE mode sometimes.

In the big A310 thread people are discussing this right now, and one thing that was said -- in real life A310 pilots reported that they rarely descended in PROFILE mode because the real plane is that inaccurate.

[Fiorentoni 4,132]

I'm not an A310 pilot but I'm sure VNAV is not so bad it completely levels off... I'd guess it was a user error.

[Beardyman 604]

Just now, Fiorentoni said:

I'm not an A310 pilot but I'm sure VNAV is not so bad it completely levels off... I'd guess it was a user error.

During climb it works ok, but in descend it does not

[Beardyman 604]

5 minutes ago, Mace said:

I'll have to drop out of PROFILE mode and into FL CH with managed speed to correct the descent profile.  Then I can re-enter PROFILE mode sometimes.

Will have to try this way.

I do not know if ur way is correct, or VNAV for descend phase was not perfect and such is simulated, i just assumed that autopilot should react as long as it properly recognizes top of descend.

[Flic1 972]

8 minutes ago, Beardyman said:

Will have to try this way.

I do not know if ur way is correct, or VNAV for descend phase was not perfect and such is simulated, i just assumed that autopilot should react as long as it properly recognizes top of descend.

You need to hit the Profile button in order to start descent unless you have it armed ahead of time.  If armed, you should see 'P.Descend' in blue on the FMA and it should automatically start descent at TOD.  Make sure you check to see your altitude restrictions are also correctly showing in MCDU and new altitude is set.  I have not had any issues with a VNAV descent on my 8-10 flights so far.  The ILS GS capture is another story...that only captures about half the time...

[Maxis 1,857]

22 minutes ago, Beardyman said:

During climb it works ok, but in descend it does not

Descends fine for me but if i recall this isn't a situation where you lower the alt on the MCP and forget about it .. I think you have to trigger it at the TOD (see post above).

Edited November 22, 2022 by Maxis

[Beardyman 604]

Ok, thanks to all of u for ur notes, will try those on my next flight

Edited November 22, 2022 by Beardyman

[JSmith2112 317]

18 minutes ago, Maxis said:

Descends fine for me but if i recall this isn't a situation where you lower the alt on the MCP and forget about it .. I think you have to trigger it at the TOD (see post above).

You set a lower altitude then pull the alt knob. The aircraft will automatically descend at the TOD point similar to how it works in the PMDG 737.

[crimplene 631]

In this video it is explained. Descend starts at 30 mins or so.
 

 

[Maxis 1,857]

28 minutes ago, JSmith2112 said:

You set a lower altitude then pull the alt knob. The aircraft will automatically descend at the TOD point similar to how it works in the PMDG 737.

Thank you .. That's the trigger. was not in front of the virtual panel to fully flesh out the instruction. ( Pulling the alt button after setting the alt is a reflex item for me in an airbus). With the PMDG .. there's no pulling involved .. set the lower alt at anytime before TOD ... thats it. 

Edited November 22, 2022 by Maxis

[btacon 1,772]

1 hour ago, JSmith2112 said:

You set a lower altitude then pull the alt knob. The aircraft will automatically descend at the TOD point similar to how it works in the PMDG 737.

Yes to pull the knob. No to just like PMDG 737.  Boeing aircraft will self descend without pilot initiation if a lower altitude is in MCP AND the aircraft has passed the TOD. Regardless, no Pilot initiation is needed. 
 

BTW the Pull to begin descent is an Airbus trademark and you will find the same behavior in the FBW a320, the Fenix a320 and of course the entire suite of FSLabs a3xx offerings for P3D and FSX

-B

Edited November 22, 2022 by btacon

[JSmith2112 317]

3 minutes ago, btacon said:

Yes to pull the knob. No to just like PMDG 737.  Boeing aircraft will self descend without pilot initiation if a lower altitude is in MCP AND the aircraft has passed the TOD. Regardless, no Pilot initiation is needed. 

To clarify: In cruise on the 310 you dial in your lower altitude, pull the alt knob and the aircraft will stay at cruise altitude and follow whatever waypoints you have in your flight plan up until TOD is reached. It will then initiate descent automatically.

From what I've read about the 320 it won't initiate a descent at TOD.

[Maxis 1,857]

18 minutes ago, JSmith2112 said:

 

From what I've read about the 320 it won't initiate a descent at TOD.

hmm I don't think that statement is correct ( You will for sure be chasing the "tennis ball" but it descends)  I tend to set the lower alt and not pull until within 5 miles of TOD because from my experience if pulled during cruise at any appreciable distance before TOD than that usually results in aa shallow descent  until reaching the calculated TOD and then it initiates the full descent until it converges with the optimum descent profile.

snippet taken from 

https://www.smartcockpit.com/docs/Airbus_Descent_Monitoring_1.pdf

Initiating descent (DES Mode) The aircraft will not start its descent automatically when reaching the top of descent (T/D). In order to initiate the descent, you set the ATC lower clearance altitude on the FCU, then push the ALT selector knob. The aircraft will then descend immediately.  If the descent is initiated before the FM computed T/D, the aircraft descends at a constant V/S converging on the descent path from below. The A/THR operational mode will be SPEED/MACH.  If the descent is initiated after the FM computed T/D, the aircraft descends at idle thrust and attempts to converge on the descent path from above. The A/THR operational mode will be THR IDLE.  If the descent is initiated at the FM computed T/D, the aircraft is descending on the FM calculated vertical descent profile. The A/THR operational mode will be THR DES.

Edited November 22, 2022 by Maxis

[JSmith2112 317]

15 minutes ago, Maxis said:

31 minutes ago, JSmith2112 said:

From what I've read about the 320 it won't initiate a descent at TOD.

hmm I don't think that statement is correct

What I'm saying is that in the A310 you can literally reach top of climb and immediately dial in a lower altitude and arm the descent. The aircraft will continue the cruise at your previously selected cruising altitude until TOD is reached and without requiring any further action from the pilot, it will initiate the descent.