Good Evening,

I have been searching high and low since I made the switch from FBW to Fenix on Monday and I have encountered an issue that I cannot seem to find a resolution to.

Upon departure in the A321, passing around 40ft (AGL), the elevator starts rapidly pitching up and down. If this behavior is not aggressively handled (pulling my TCA sidestick almost full back) the issue will cause the plane to start descending uncontrollably. Additionally, in the A319/A321, during short final, this same behavior will occur (even with autopilot engaged). When this occurs, the Fenix MCDU shows that there are no inputs and that the aircraft isn't doing anything with the elevator; however, you can see on the F/CTL page that the elevator is rapidly oscillating.

I have spent extensive time messing with my settings (adjusting the sensitivity of my calibrations, redoing all of my calibrations in Fenix and on MSFS, etc.). I have also tried adjusting speeds for rotation and final approach and I cannot find a solution. I have also searched almost every resource I can think of (including forums) with no luck. I also did a reinstall of the aircraft just to be sure. I am not using any add-ons and I currently have live weather turned off and turbulence is set to low. 

Here is a short video (I am descending into a neighborhood and the MCDU is not configured by any means but it does show the behavior that is encountered): https://streamable.com/ksudbj   You can see (in the video) that there are absolutely no inputs being made on my sidestick (the MCDU is displaying the config page). The only thing (in this video) that I can imagine would cause this behavior is the degree shift in the wind (no speed changes) but I cannot figure out why the aircraft would behave this way.

I do not have this issue with FBW or PMDG aircraft.

Any help/resources/pointing in the right direction would be really, really appreciated.

Thank you so much!

Edited August 22, 20241 yr by Alex Handsaker

5 hours ago, Alex Handsaker said:

Upon departure in the A321, passing around 40ft (AGL), the elevator starts rapidly pitching up and down. If this behavior is not aggressively handled (pulling my TCA sidestick almost full back) the issue will cause the plane to start descending uncontrollably. Additionally, in the A319/A321, during short final, this same behavior will occur (even with autopilot engaged). When this occurs, the Fenix MCDU shows that there are no inputs and that the aircraft isn't doing anything with the elevator; however, you can see on the F/CTL page that the elevator is rapidly oscillating.

 

I see the same. It is more prominent in the A321 but also occurs in the A319. It does not happen on every flight but often. It seems to be related to turbulence by wind and terrain.

I first thought it might be an incompatibility of an addon. But the issue still occurs even after deactivating RealTurb, ASFS and FSR from the exe.xml. I also ruled out any controller issues by completely deactivating them.

 

Someone else has reported that as well in the "released"-thread:

On 8/20/2024 at 12:43 AM, Azapata87 said:

Had some serious porpoising after rotation on my first departure with the A321. Not sure what that was about. 

 

EDIT: I did some more tests. Your video seems to show very low FPS. I also run the sim at quite low FPS (and use a feature of my Samsung TV to upscale these to the TV refresh rate to get a fluid motion). I increased my FPS limit and found that the issue was gone when I run the sim at a minimum of 20 FPS. The issue seems to only occur when the FPS are below 20 FPS.

So it seems that the new fly-by-wire logic of Fenix requires at least 20 FPS to work properly.

It would be nice if @Aamir or @FNX_Dave could confirm that for reference.

 

Edited August 22, 20241 yr by RALF9636

So far I didn't run into this issue. Did you report it to Fenix via a support ticket?

I believe Fenix are aware of this.

Thank you OP for your detailed description of the bug, also identified in one of his streams by A320 Sim Pilot:

GLOVO SONG 6s Portugues DIGITAL (youtube.com)

I never used their Discord forum, but many users told me they're very active there. Maybe you could post your findings there?

 

 

I mentioned in another post on this site that something very similar to what the video in the op shows occurred on my first flight with the 321 out of JFK.  I also have a low end graphics card and suspected this was the contributing factor.  It was also a windy day so it’s possible that those multiple contributing factors create this situation.  I’ve not had a chance to fly the 321 or 319 out of a less demanding airport yet.  I did not experience any issue on landing( into Orlando which is far less taxing than JFK) so I think the low FPS seem to really be the likely cause.  Perhaps the 321 could use a bit more optimization( and I need to upgrade my computer to be fair) because I’ve never had this experience in the 320 with well over 50 flights in that plane.

Edited August 22, 20241 yr by jspilot

56 minutes ago, jspilot said:

I mentioned in another post on this site that something very similar to what the video in the op shows occurred on my first flight with the 321 out of JFK.  I also have a low end graphics card and suspected this was the contributing factor.  It was also a windy day so it’s possible that those multiple contributing factors create this situation.  I’ve not had a chance to fly the 321 or 319 out of a less demanding airport yet.  I did not experience any issue on landing( into Orlando which is far less taxing than JFK) so I think the low FPS seem to really be the likely cause.  Perhaps the 321 could use a bit more optimization( and I need to upgrade my computer to be fair) because I’ve never had this experience in the 320 with well over 50 flights in that plane.

Watch that video by A320 Sim Pilot I linked just above your post. it's not you or your system... Must be something with the Fenix and they're aware of it.

Good Morning,

Thanks for all of the responses. The video is absolutely terrible quality, I am getting well over 50fps but that video doesn't do it any justice (the video is noticeably TERRIBLE fps) but my sim is not anywhere near that bad (I think the website I uploaded it to reduced the quality because the actual video isn't that bad, either). I have a high-performance gaming computer so that rules out the low fps issue. 

It's a shame this may be more than I can fix on my own. I was really looking forward to these aircraft. 

It’s a known issue. They will surely fix it ASAP

On several flights around KPHX last night while testing the A321 IAE I experienced this fluttering on both, takeoff as well as during the very final stage of the final approach.  I initially thought it might have been a weather related issue or even wake turbulence, but I was able to reproduce on every circuit.

17 minutes ago, DMullert said:

I initially thought it might have been a weather related issue or even wake turbulence, but [...]

It's "code" turbulence 🤣

Second flight with a321 today, the first no problem during to, second flight limit tailstrike.

Didn't see this with 319 

To follow-up, yes, I did open a support ticket with Fenix yesterday afternoon. I'm glad it's a known issue and not just me, I couldn't find anyone else describing the issue so I started to worry I was missing something. 

Long thread in their discord support forum about this oscillation issue. People saying that they are aware of it. I’m hoping they can get it handled by the end of the day tomorrow so we can all enjoy a weekend of flying without this buggered issue.

That would be awesome! I don't use Discord, anymore, so I'm glad it's being reported and addressed on there. That gives us hope!