A321 physics issues

I and a few others have had a bit of a chat about what you’re experiencing. We don’t necessarily think that what you’re experiencing is an issue per se.

Firstly, you haven’t provided us with your weight and balance. The speed at which you pull out your flaps is hugely affected by the weight of the aircraft. Hence, can you screenshot your weight and balance page?

I have tested with the following parameters (which I would consider to be “realistic”) to simulate a landing:

  • 174 passangers
  • 5,220 kgs of cargo
  • 1 hour of fuel left

…and I have not really experienced the issue you’re describing.

Secondly… what you’re describing could be there by design. If you’re descending towards an airport, and you pull flaps from 0 to 1, the lift would increase and hence your vertical speed would decrease. As a result, the autopilot will compensate for the incease in lift by bringing the nose down. This is intentional, not just in Infinite Flight but in real life too.


The only issue i have with this A321 is that the autopilot makes waves by continuously going up and down even at normal altitude and speed cruise.

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That’s not an issue anymore.


This has been tweaked in 19.2. Have you experienced this after the release?


No i didn’t flown the A321 today. Sorry for being late on this. Thanks to devs for the fix

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I did take the A321 out for a brief spin-I noticed I needed much less trim than before. That’s all.

Solid reply @Maxim I have the Vref speeds for the A32X family and they work amazingly well for Approach when corrected for wind.

Last two pages of this document:


If he’s at 160K lb or ~72000kg and there’s no wind, the approach speed should be 149kt and the touchdown speed should be 144kt.

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Daniel after further review-you’re 100% right. The plane requires way less trim and the landing speeds I’ve been using religiously for well over a year are a bit off-m (as it relates to flaps full/2.5° pitch angle etc)

Is this an issue in terms of real life physics or is it just different?
I’m relaying all of this to the right people, but the more info… the better.

Nothing should be different as i mentioned before, but obviously something seems to be.

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As referenced above in my previous posting, I’ve been flying the A32X family in IF by the numbers on the chart listed above and they work PERFECTLY and I do mean perfectly. In this update it seems the A321 is more “slick” as it were.

-Descents between -500 to -1200 or so where it would normally bleed off speed slowly, it’s now sticking at speed or increasing where it has not done that before (this part feels more real tbh)

-For Takeoff/landing, I’ve tested multiple weights multiple times and also cross tested w the A320 to be sure-the A320 seems “normal” on takeoff and approach.

-For Takeoff I’ve previously used 25%-40% trim in the A32X family (its the same wing-it’s always flown the same before in IF) now, the A321 with heavier weights comes flying off the runway with neutral stick at the trim settings I’ve used prior to IF 19.2-where I put in negative stick up to 100kt, ease it to neutral, then rotate at VR-the nose is coming right off at the neutral stick/elevator setting.

-In 19.2, on approach in the A321, the Vapp calculations by gross weight that I have used for the better part of 2 years to get consistently good landings seem too fast, require a lot less trim than before (pre 19.2 required ~60% or better trim at Vapp for flaps full)

I attempted a different Airbus calculation for Vapp and it seemed to work slightly better-but again the trim % and the feel from pre 19.2 aren’t the same at all.

I would be happy to test and answer questions in any way that will help.
Below is a screen I sent to my VA after first reading this thread and testing out the A321


As per above which corroborates what I’ve said, it is different. Potentially the changes made to counter the bobbing have had an unexpected knock on effect.

Thanks for the info

yes, rotate speed and control input is now much more neutral. You almost then need negative trim to counter the pitch up on climb out with flaps still extended. Once you retract, it returns to normal.

As you’ve said it also seems to have a more profound pitch down on descent in general and this could amplify the pitch down tendency when flaps are extended.

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Hi everyone,

Thanks for the feedback, and you were right, some change I thought had been reversed actually made it into the release :-/ I apologize for that…

Now… the changes make sense to build and tweak upon rather than reverting. Basically, the CG in 19.1 was too far back and made the whole plane unstable. The elevator had very little leverage to make things stable.

If you’ve got some reference points I could use to tweak the model, please send my way. But not things based on 19.1, real world numbers. I will look at my info, but if you’ve got some more I could cross reference too, it would be nice.

Having a list of Flaps/Pitch/N1/IAS is what I can work best with. Of course, with a source :)



Don’t compare trim settings vs previous versions. The trim in IF works differently than the real thing. So whatever numbers worked great for 19.1 need to be adjusted. What matters is the IAS/attitude/power required at various flight configurations.


I’m trying now, at 62,000kg, descending through FL190, i’m slowly bleeding speed at -1200vs…


To all who want to assist with the tuning of the model, we need data from an actual flight manual or trusted source, not something based off of 19.1 which may not have been accurate to begin with.

It’s always best to go from actual data :)

I’ve spent some time working on the physics this morning. If you restart Infinite Flight and pick the A321, you should have those changes. Here are a few things I changed:

  • Adjusted lift for all configurations so stall speed is more accurate (150kts at 62,000 Kg with Flaps 0 for example)
  • Adjusted pitch in cruise (was 3.5 deg, should have been 2.5)
  • Adjusted landing attitude.

These changes may require pilots to adjust their trim tables. Bear in mind that we’re a simulator working from external data with no access to manufacturer internal flight model parameters. So while we always try to get closer to the real numbers, we’ll always have to approximate things as long as we don’t simulate every single atoms on the plane.


Thanks Laura. Is this coming in the hot fix?

There is no need for a hotfix for these changes. Simply follow the instructions above and you will have those changes.

So do u delete the app and reinstall it