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Help! Fixed Wing Pitch movement (oscillation) on Auto Mode

Hi everybody! I need some help. My fixed wing (delta plane) works perfectly in all the modes. Although I have made an autotune, I’ve not been able to find out why there is a pitch movement when The UAV is flying (when it is on takeoff)… In the video it is possible to see a sudden downward motion when the plane reaches the expected fligth height. Then, it continues flying at the expected height for the mission. Could it be due to a configuration parameter or can it be a consequence of some problem in the plane’s center of gravity?

In the next links will find a video and the params file.

https://drive.google.com/file/d/1nJfRHwkigAdBaIaaM9R01vHO2FciLfLT/view?usp=sharing

https://drive.google.com/drive/folders/1KuzWaVHe9uT4zqh8XYUzuUqwSGclHVlD?usp=sharing

at first glance it seems like your pitch gains might be a little high, but i see your pitch P is set pretty low already. i think we really need a log file to diagnose.

on a sidenote you’ve got ARMING_REQUIRE set to 0 which basically disables the whole arming process. is this intentional?

Hi, Hi! How are you? Thank you very much for your help.
The Arming_require parameter is at zero since I assemble it before the flight, when the plane is still on the ground, by means of a button located on the top. is it right?

A few minutes ago I did a flight test. The plane flew well, with a slight oscillation during the takeoff and, when the plane reached flight height, a downward fall.
But I had a new problem today … at the time of landing, the plane touched down just after the do_land_start event and at 30 meters high.
I send you logs of autotune, fbwa and auto flight modes, and the flight plan.
Thank you very much for helping me!!!
I look forward to your reply.
Regards

https://drive.google.com/drive/folders/1_tZBU0fvr3-nt0UMfE6ere6hC0l5g4Hz?usp=sharing

hey dronar, seems your pitch gain is still a bit too high for your individual setup, there’s still some flutter at lower airspeed. actually pitch P is 0.4 now while it was 0.3 before. chances are your elevon throws are compareably large, so i’d suggest to check your mechanical setup, maybe post an image of your elevon linkage geometry.

re arming and safety switch handling it might help to check the wiki on those topics:
https://ardupilot.org/plane/docs/arming-your-plane.html
https://ardupilot.org/plane/docs/common-safety-switch-pixhawk.html

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