Skywalker x8 weaving during flight in AUTO mode

Hi guys,

I have problem with navigation of my Skywalker x8 in AUTO mode. As you see on the picture below, the plane cant fly straight between waypoints and also makes unnecessary turnings. I am using mission planner ver. 1.3.44.


First I tought the problem is with navigation tuning and tried to change some parameters, Here are the parameters from which I started:




RLL2SRV_D 0.02

RLL2SRV_I 0.04




After that I tried to make some changes in the values but it didnt help. Do you have any idea which parameter can cause this issue? Some other parameter what I didnt change? Or could it be something else like compass error? The plane is flying well in manual and FBWA modes. I will appreciate any help!!

I also uploaded the logs to google drive, here is the link for download:

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  • Moderator

    Your RLL2SRV_I and PTCH2SRV_I seem quite low, is this after autotune? Way back I used RLL2SRV_P = 1.4 and RLL2SRV_I = 0.3 on an X8 I tested with. NAVL1_PERIOD was 20 and NAVL1_DAMPING 0.75 with max roll at 45°

    This was 60km of flight in auto:


  • Hi Mira,

    Did that X8 ever flown straight? Is the Board firmly attached to the plane? may it have vibrations? Have that X8 been tuned via Autotune flight mode?

    Hope we can solve this!

  • I would study your GPS signal, and all the error/noise values.  I have found that mounting the GPS high up and away from all other electronics & motors can radically improve the GPS signal, and adding a grounded copper tape insulator between the GPS and the electronics can help.  I was seeing EPH/EPV up to 3 meters, and not very nice autonomous missions, but after remounting and insulating it is always sub 1 meter, and as a result GPS tracking is much better.

  • Moderator

    I cannot get at any logs until much later today.., 

    The easy way to see this issue is in manual control, The X8 flys well under RC control and if Adverse yaw is the problem then when the aircraft is in level flight and you command a medium RIGHT turn the aircraft will Yaw LEFT and then you will see the planes nose drop and it will turn RIGHT.


  • Here is a screenshot with WPs and the worst flight with NAVL1_PERIOD 19


    Mira said:

    Hello Anton,

    thank you for your reply! Do you also have a screen with waypoints? 

  • Hello DwgSparky,

    First, thank you for your reply. Your post sounds reasonable because I did some elevon changes in the past. I will definitely try it tomorrow and let you know about our results. Could you please send me some of your logs using fixed wing? Thank you in advance.


  • Mechanically the plane is just fine. I am not using STALL PREVENTION because it wasn't allowing for good AUTO takeoffs from the catapult. Analyzing today's logs seems like the answer to my issues are indeed STALL PREVENTION algorythms. I have ROLL limited to 35°, while NAVL1 set to 20, these angles were exceeded during navigation up to 45°. While NAVL1 set to 19 these raise to 60° during all those pirouettes seen in the log flight path. So STALL PREVENTION was smoothing out this behaviour, once it is switched off NAVL1_PERIOD has to be tuned precisely.

    Just to mention, before turning off STALL PREVENTION the plane was navigating very well.

    As for other planes, those have STALL PREVENTION ON and use runway takeoff, navigating fine using stock NAVL1_period - 20.

  • Moderator

    This may be a mechanical issue? does the aircraft fly OK in stabilize?  or is it hesitant to turn ?

    I have seen a similar example of this with a flying wing where the down going Elevon in a turn was causing the aircraft to Yaw in the wrong direction 

    ie. if you want to make a turn to the right your Left Elevon will drop and cause the aircraft to Yaw to the Left instead of making a good banked turn to the right. 

    If this is the problem then AUTO will never work right. 

    its easy to fix, reduce the maximum downward deflection or the Elevon to 50% of the Up going deflection. now all my aircraft are set up like this .  

  • Hello Anton,

    thank you for your reply! Do you also have a screen with waypoints? Btw. did you try to turn STALL PREVENTION back ON? You also mentioned that only one of your planes does that. Other planes works fine for you with same navigation parameters? Thank you and good luck for tomorrow.


  • Here is a direct comparison of same almost square mission with different NAVL1_PERIOD values.


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