Please Help with stability issue on BIG D-130 X8

Hi All 

Having some stability issues on my D-130 X8

In light wind or (as today) in suspected thermals it gets very unstable Scary on a 10 000Usd rig!!

If I compare Roll des roll and Pitch Des pitch it has a big gap right betore i aborted the mission and climbed accidentally over 120 m fence in stab mode...  between the both...

I have manually tuned the D-130 and it is VERY stable in STABILIZE mode but as nov in AUTO or RTL mode it becomes very wobbly!! I have also lowered the CG by moving the lipos to below center plate. Got somewhat better but still scares the sh..t out of me when it starts wobbling in any autopilot mode... Maybe i have to lower the nav gains on this big bird??? Or what??

Please tell me what to do. :-(

29.BIN

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Replies

  • Hey Ronny, you ever have the wobble show up again?  I'm getting instability at anything over 5m/s.  My setup is pretty much exactly like yours.  I put the batteries on the bottom as well, but it's not by choice, I needed to mount a GNSS antenna on the top for the RTK.

  • Found it out myself..

    After my latest mod with lowering lipos for more static staility I did not tune accordingly.

    Just made an Autotune flight and ended up with Rate P from 200 to 305 Rate I from 180 to 305 and was lower D 0,008 down to 0,002

    If this could help someone.

    Now Roll and des roll and Pitch and Des pitch is following each other perfectly fine...

    I would kiss the guy that invented autotune on the forehead if i met him ;-)

    • Glad you figured it out.

      Side note:  A lower CG on a multicopter does not improve static stability.  There is a very common misconception that making a drone more "pendulum like" improves stability.  This is not the case.  There are a number of very good explanations hiding somewhere in this silly forum describing why this is.

       Any weight shifts to improve stability should be aimed at reducing moment of inertia (move weight towards a central point).

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