A32NX Unstable on landing - Pilot Question

Hi All,

Quick question - I am finding the A32nx very unstable when trying to land at 140 knots with flaps out. The auto thruster is on. Basically, it starts to drop gradually out of the sky and the nose won’t life. I have been landing with around 9000KG of fuel on board (the default amount) having done very short UK domestic flights.

Is this a symptom of the plane being over weight? And how many KG of fuel should be in the plane on landing with a 30% (default) load?

I have also experienced difficulties with the A32NX specially when it comes to follow the Navigation and on approach after setting the flaps I need to reduce power in order not to overspeed but the pitch is almost at 10% so it makes it very hard to land due to visibility

Hopefully it gets ironed out soon…

This from another posting regarding the approach, I believe its the same issue?
I have been having this issue too, see my previous posts above. There is a problem with the CofG and the autotrim since the last update. On approach in particular, the aircraft requires too much “up trim” even when descending. It often descends below glide because there is no “up elevator” left to apply in order to maintain the correct descent path. (look at the stab trim when this is happening) If you apply more power you just then overspeed. It doesn’t happen in the stock A320.
I have tried all variations of CofG, made it nose heavy, tail heavy, same result, goes to full up trim on approach. I have now sorted this as a temporary work around. I replaced the flight_model CFG file in the A32nx, with the stock one from the Asobo Neo. I have all of the functionality of the brilliant A32nx and the flight characteristics of the stock. It worked for me (make a backup first)
The file can be found at Community/A32NX/Simobjects/Airplanes/Asobo_A320_Neo/ flight_model (CFG file)
I backed it up first, and copied and pasted the same file from the stock Neo. I haven’t had an issue since.

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Thank you will try this now

That seems to be the problem! Nice explanation!

So where do you find the default file from Asobo?

Thanks!

FYI in the latest master build they reverted the flighmodel changes so it is essentially stock now and no longer need to swap files.

From Github pull request:
The actual inflight behaviour should now be identical with the default plane again, with all the changes Asobo has made to it so far.

Only thing they left in was the ground handling.

Ok thanks for that, if they have reverted to the stock “flight_model” CFG file, that has been done since I downloaded the A32nx file two days ago, shortly after it was announced that it was running again after the last Asobo patch. I had the stock and A32nx CFG files both open side by side on my desktop. I compared line by line and there were many differences. Swapping the stock CFG file into the A32nx allowed approaches again without running out of pitch up elevator.
There is still something not quite right with the stab trim. Even with an aft CofG almost at the limit, there is still a silly amount of “up” trim applied at times, even taking into account CofG shifts, centre of pressure changes, thrust variations etc. With a tail heavy aircraft at its limits of CofG, the auto stab trim should be expected to trim forwards to counteract the heavy rear, it doesn’t. Sadly, programming and coding isn’t my thing, am sure anyone with that knowledge could adjust the settings easily. Thanks again for the update, its great to see that we can all pull together and help each other. We all have expertise in different areas. A great community.

No, this pull req was merged about 18hrs ago. At 140 the plane will now give you appropriate AOA and not struggle to stay in the air. Here is the full notes on the PR:

Flightmodel hotfix #1029

Summary of Changes

This brings most of the flightmodel.cfg back in line with Asobo’s version while keeping the changes we made to ground behaviour, MMO/VMO as well as slat positions

Additional context

The actual inflight behaviour should now be identical with the default plane again, with all the changes Asobo has made to it so far. To me this feels good, but I’m no expert on how it should feel and behave.
This PR is mostly just there to fix #1014 (as I view it as critical) until we figure out which changes to the flightmodel are causing the behaviour described in the issue.


1014 was the higher than normal stall and approach speeds. Just did a flight and the approach and landing was much smoother without having to mess with the AP. Just wish Asobo would fix the autoland flare. Still have to take it from about 300ft or it slams you in the runway @650ft per sec.

Brilliant. I will download the new version, thanks very much. The A32nx guys are outstanding.

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I re-downloaded the A32nx again an hour ago, and can confirm that for me, it’s still broken with the same issue. On approach with everything set, CofG correct, weights correct, speed correct, it undershoots the ILS, stab trim is full up, lack of elevator pitch up, same problem. Undershoot and crash.

I changed the flight_model.CFG file in the a32nx to the stock one again from the Asobo A320, had another flight with the same parameters, weights, loadings, flaps, speeds etc, problem gone.
In my opinion, there is an issue with the flight_model .cfg file in the a32nx.

As a temp work around, i found that if you put the minimum required amount of fuel in, this makes the aircraft very stable on final at 139 knots.

The default A320 flight model is currently broken due to the unrealistic slats simulation/implementation.

The lift increase/pitch change with flaps 1 we are presently seeing is way off.

Odd I haven’t run into this on my ILS landings. Just flew into KDEN and ILS brought me down right to the threshold at 140. Of course I fly AP ILS until the last 500ft so maybe I am just not seeing it.