Pitch drop when switching to AUTO

Hello guys, please help me diagnose the following behaviour: Launching the wing in STAB mode from a catapult, gaining around 40m alt then switching to AUTO, plane drops like 20-30m of height, then starts gaining alt towards the waypoint with 40m set alt. After that navigaiton proceeds with no visual problems. please help.
Please see the logs here :

It looks like your trim values for RC1 and RC2 don’t match the “in-flight” trimmed values for the radio. Both are set to 1500 but the actual in flight trimmed values are about 1380 and 1560. So when you flip to auto the plane has to build up those trims slowly using integral gain on the pitch controller. You can re-do the radio calibration after trimming the aircraft or adjust the trim values manually to fix this.

But the reaction is still slower than I’d expect for this level of trim error. I suspect that the gains could be a little higher for pitch control, and an autotune may be a good way to help tune that.

Thanks @jmack , autotune scheduled for today.

Interested to know how it goes. Note that the real issue that should be fixed is the trims, the autotune will just be a cover-up for incorrect trim values.

Hi @jmack, could you please elaborate regarding the “in-flight” trims? The only trims I have adjusted are the RC1 and RC2 trims, I have set those from full param list. Weather is bad today so most likely will be autotuning and testing tomorrow, would be great to sort the “trims” things, too.

Looking over the log, the trimmed values for RC1 and RC2 in level flight are different from what are set in RC1_TRIM and RC2_TRIM (which occurs during radio calibration).

Have you flown this in manual mode? If so, you can re-do the radio calibration after flying and trimming the airplane in manual mode to “remember” your manual mode trims.

Today managed to do the autotune, first at level 6, which appeared to be too agressive for the frame, retuned at level 5. Indeed auto transition is way smoother now. But a new issue showed up. Now when launching in STABILIZE from the catapult the plane pitches down briefly on launch which is not good for a takeoff, it pitches ignoring my ELE stick input, after the pitching it resumes to the stick inputs and starts gaining alt. I wonder if there is a way to fix this pitching issue on start, other than launching in MANUAL, as I set the plane for some unexperienced people, for AUTO missions only.

Here is a log of one of the flights:

This is the same issue as before. Because the autopilot parameters have the aircraft trimmed nose down (RC1_TRIM and RC2_TRIM) it will initially start nose down when in a stabilized flight mode, until sufficient time flying in that mode so integral gain can correct for it. Re-do the radio calibration after trimming out in manual mode and both of these behaviors should go away.