Pitch oscillation with tail wind

Zohd dart 250g
FC is Speedybee f405 wing mini

Issue: I was not able to complete a good autotune, especially pitch is always not well tuned.
During flight, the plane slowly goes up and down.

Log: 2024-12-17 15-52-02.bin - Google Drive

I tried using webtools, but no idea of what i am look at, sorry.

I think the pitch trim needs some adjusting first. The plane seems to fly mostly with negative pitch so that might be causing it to fight. Fly a level flight in FBWB for a few minutes (no big climbs) and that will show you how much to trim it by. (This log is either a steady climb or descent so it’s hard to say what’s best)

Also check the C of G. Wings are really pitch sensitive to C of G position.

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That makes sense.

I flew half flight going slightly up with no oscillations.
Than 180 turn and flew back slightly descending: this is where oscillations began.

C.G. seems ok: on the marks and plane fly perfect in manual mode.

Just to clarify, the trim I’m talking about is PTCH_TRIM_DEG.

Under the tab accel. calibration there are 3 buttons.
One of that should make the same function?

The param you mention, i used it on my other wing, to mantain altitude at trim speed on fbwa. Useful!

I would use the in-flight data to make the correction. Then you know how it’s really acting in flight. Most planes will have a few degrees of nose up in flight, different from what’s on the ground, so by using the data you can take out the guess work of what you think it needs to be.

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So, i am back home.

How can i detrmine how many degrees i need to correct, looking at the log?

If you’re flying in FBWB or Cruise mode, the plane will automatically maintain altitude for a given throttle setting. Assuming you have the cruise throttle set where you want it you can look at the desired pitch of the plane. If you see the plane is holding a 2 or 3 degree nose up attitude in level flight then you can the trim that amount.

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