Hi Everyone,

I've recently installed a pixhawk running Plane 3.4 into a 2015 Skywalker 1830. The plane flies pretty nicely in Manual and FBWA modes but there seems to be an imbalance in the aggressiveness of left and right turns in AUTO mode.  When turning left, the plane seems to under steer and take a long time to get back on track. The opposite happens when turning right however, with the aircraft over steering a lot, which often results in tip stalling. 

If one or the the other action happened for both directions I would usually be able to tune it out, but if I tune for one circumstance it makes the other worse in this case. 

The plane is balanced about the longitudinal axis, and there doesn't seem to be any uneven twisting in the wings. The propeller is spinning in a clockwise direction when viewing it from the aft of the plane, which I'd assume would aid the aircraft to turn left with torque roll,  if there is enough torque roll to make a noticeable difference.

Has anybody else experienced a similar issue? Am I missing something obvious? Any help would be really appreciated!

I've attached param and tlog files of the plane doing a survey grid. Here is a dropbox link to the .bin file.

Thanks,

Luke

2016-01-29 13-06-22.tlog

skywalker2015.param

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Replies

  •   Hi  Luke I going to  install a pixhawk into my first  skywalker 1900 mm, can you shares your parameters?

     cheers

     

  • Hi everyone, 

    I flew my skywalker again yesterday, and it turned out a reversed rudder was indeed the problem. I didn't pick it up in my preflight checklist as my rc controller was moving the rudder in the correct direction. It seems that the rudder mixing was reversed however.

    Rookie error I guess! She flies like a dream now.

    Thanks for your help everyone!

    Cheers,

    Luke

    • Hi Luke,

      just these days I'm enjoying first flights with my very new Skywalker 2015 / 1830mm. She flies great in manual as well as in FBWA (juts litlle bit lazy to turn at this time as roll and pitch P constants are at default value of 0,4 yet). During my next flights I want to tuneup Roll and Pitch PID paramaters. Looking to .param you provided I see relatively low RLL2SERV_P and PTCH2SERV_P values. How did you get these values? By passing Autotune procedure or just guessing them "from the sky"?  And what motor/prop setup do you use? At this moment Im using 2820 / 830kV with APC 12x8 prop, but it seems to be too much power for this airframe.

      Radek

    • Try using a 3S battery and see how the power is. If you need more try a Slow Fly 12x6
  • What prop are you using? 12x12 and 12x10 exacerbate the spiral slipstream issue iskess mentioned. A simple fix is to get a prop with smaller advance ratio and add some mechanical offset to your rudder to the left. Also turn down throttle slew, the quick motor spin-up while turning right is a big part of it. the E384 uses 45% throttle slew.

    • Jeff,
      What prop and KV did you choose for the E384?
  • Does the plane always track to the right of the course when flying the grid? If do, this is s common Skywalker issue. The fix is tuning the yaw controller, and tons of rudder trim.
    • I have a new aero-m that is always tracking to the right and flying at about 10-15deg roll. Havnt had time to check it out properly yet but everything looks good on the ground. Its on the default tuning it come with as this works well on our other aeros.
    • Moderator

      Are there shims on the engine mount?

    • I believe the issue is spiraling slipstream on the tail, so I don't think shims will help much.
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