CPU performance issue since December '25 update

1st Official Post

    Hi, I have an issue with CPU Frametime performance in VR since the December 2025 update. I used to have smooth 45 fps in VR on my configuration using Vulkan, with CPU Frametime usually being around 6ms. However, after the last update my CPU Frametime frequently suddenly jumps to 40ms in a lot of areas, making the sim unplayable. It seems that something is blocking CPU? Meanwhile, CPU usage in task manager is lower than 20%, no cores at 100%.

    My graphic settings were previously all on High. If I turn the trees down to Low, it becomes better, but I still hit that CPU (?) bottleneck frequently which kills the framerate. If I turn my head in another direction, it drops to the usual 6ms.

    Tried clean install and deleting User folder, but no improvement. Also tested with several versions of SteamVR and nVidia drivers.

    I have reverted to the previous sim version, 4.7.4.4 from September '25, and it works perfectly, no issues at all, with stable low CPU frametime.

    Configuration: laptop with 4060 graphics and 7840HS CPU on Windows 11.

    Is there anything to test with sim settings, to try narrowing down the cause of the issue?

    Some additional info: in some locations, I can trigger the CPU issue just by turning on the plane. For example, sitting in cold & dark c172 in Bolzano, CPU frametime is low. As soon as I switch on the battery, without moving my head, frametime jumps to 40+ms. If I turn the battery off, it drops back to 6ms.

    Another: sitting in the same plane when the frametime is very high, if I put my head outside of the window, or above the roof (still looking in the same direction), frametime drops to normal. As soon as I re-enter the plane, it jumps to high.

    • Official Post

    The latest version uses a little more memory compared to previous versions. If your system was almost utilizing all GPU RAM, this version might now exceed it. Verify this by setting the graphics options even lower and report back.

    Does the drop occur in less populated areas also?

    Are you using 3rd party user content? If so, please disable this.

    How much RAM does your GPU have?

    If possible, please post your tm.log file located in Documents/Aerofly FS 4/tm.log

  • Post by 777Driver (January 12, 2026 at 2:14 PM).

    This post was deleted by admin (January 12, 2026 at 2:31 PM).

    Here is additional info:

    v4.8 (VR, Vulkan):
    Everything on high: VRAM used 4.5/7.8 GB, frequent CPU issues (frametime 40+ms)
    Everything on low: VRAM used 3.7/7.8 GB, CPU issues only in some areas
    Everything on low, trees on medium: frequent CPU issues

    v4.7 (VR, Vulkan):
    Everything on high: VRAM used 4.3/7.8 GB, no CPU issues (frametime 5-6 ms)

    System RAM usage: 11/15.2 GB

    CPU frametime issues are present even in areas like high above ocean (but only in complex planes, not gliders and c172).

    All 3rd-party content removed and user folder deleted.

    Attached 2 log files from 4.8 when issues occur.

    • Official Post

    Thank you for this detailed report.

    So even on everything at LOW setting you observe CPU issues if flying over the ocean, correct?

    But this only happens in complex airliner models and not with C172?

    Can you describe those 'CPU issues' a little?

    Do you see those CPU issues if you are not flying VR?

    And last question: Can you run Aerofly FS in native Oculus VR mode?

    Correct, even with everything on low, over the ocean, there is heavy stuttering when moving my head and looking inside the cockpit; CPU frametime graph in fpsVR looks like this then:

    If I look outside, CPU frametime returns to normal (5-6 ms).

    On ground, CPU frametime is solid red, 40+ms.

    Note: pausing the sim does not change anything, even then the issue is present.

    Cannot run it without SteamVR, using PSVR2 headset.

    Over the ocean, issue happens in airliners and KingAir, but not gliders, choppers, c172, b58, military planes. On ground, happens in all.

    I do not see such stuttering in non-VR mode (probably because it is not taxiing enough on HW as VR).

    No problem, I am happy to experiment to get to the bottom of this. Yes, issue happens on freshly loaded game & plane.

    I do not notice such stuttering in non VR mode, and fpsVR does not work in non VR mode, to see the CPU graph. Looking at Steam Performance Monitor overlay, I do not see any glaring changes in CPU usage when moving the view.

    Here is a video showcasing this issue, in a glider: https://we.tl/t-NkyqDm8HOf (60 MB). Note how CPU frametime graph changes when the view is moving.

    And in the end, closing the canopy (and not moving my head) also causes the spike. So looking in the same direction with canopy open, no problem. With canopy closed - problem.

    Let me know if it would be useful to record another such video, with another plane/location.

    • Official Post

    Thank you for the details. The video is clear, the view direction influences the CPU a lot, but it shouldn't influence it as much as the video shows. The strange thing is, that you don't observe it in non VR.

    In non VR you can enable the FPS display with CONTROL + F1. If you set FPS to unlimited and do the same video with the glider, can you upload that as well?

    When we fly the KingAir over open ocean we hardly see any view dependance on the FPS. It runs rock solid smooth in all view directions.

    Again, can you confirm no 3rd party user content is installed?

    Here are non VR videos for the glider, for sim v4.7 and v4.8, both in Ultra settings (any movement jerkyness is due to my mouse): https://we.tl/t-xaw3IZpHDT (2 videos)

    Note that fps is noticably worse in v4.8, roughy 100 fps in v4.8 and 150 fps in v4.7.

    And a couple more VR videos over ocean on High settings (shadows low): https://we.tl/t-wNRz3brieH (2 videos)

    Also noticed in all planes where canopy can open - as soon as I open it, there is no problem while looking out of open space. If I look through the open attached canopy (e.g. Extra330 on the right side), the problem remains there. Is this maybe some issue with transparency rendering?

    Canopy being closed seems to add a lot of CPU frametime in v4.8. Example with Extra330 on v4.8:
    - Looking 90 deg left with canopy closed, CPU frametime is 7.5 ms
    - Same direction, canopy open: 3.5 ms
    On v4.7, there is no difference in open vs closed canopy (3.5 ms).

    No 3rd-party components, I have completely removed user folder and game re-created it.

    • Official Post

    Ok, thank you for your patience and the information. What we do see from the videos is, the v4.8 version is actually using a lot more memory and rendering more objects. We currently think this is the cause of the issue you see.

    As a last test for now, can you send a screenshot of Aerofly FS for both versions ( 4.7 and 4.8 ) and with the same view configuration ( roughly! ) and after a clean start with no other things done. E.g. run Aerofly FS go to simulation and take screenshot. We then compare the numbers at the bottom and try to find out why the memory usage is much higher and more objects are rendered.

    • Official Post

    Ok, thank you. We need some time to investigate. From the images one can see there are more 'power poles' for example in the new version. This is due to the new data being used in v48 compared to older ones. However this shouldn't cause this huge FPS drop.

    Also memory usage is a lot higher, this also shouldn't cause the FPS drop.

    Just for our reference: Did you download the v47 version from Steam for the test, or did you make a backup and start from the backup?

    Have you installed the DLCs Europe 1 and 2? If yes, v47 uses the OLD cultivation files and v48 the NEW ones. From the images it looks like it. But again, the new cultivation data shouldn't account for this FPS drop even though there might be more objects.