Z84 Tailisitter - Q landing issue

ArduPlane Plane 4.1
1

Hi Folks,

I ve built a tailsitter with a Z84 platform.

My setup :
Motor 2205 2350kv
Esc 30A
Prop : 6x4

The transition Qloiter or Qhover to Fbwa is smooth and successfull.
The flight on fbwa or stabilize is ok.
The transition Fbwa to QLoiter is done in 4 seconds and the wing climbs of 10 meters.

After there is an issue for landing. When I decrease throttle for loosing altitude, the wing is vertical and little by little it becomes horizontal. I must then switch to fbwa and leave in airplane mode.
I ve never succeded land in Qmode. The attempts were done without or with few wind.

Please could you help me and analyse my log and params enclosed.
Params : https://drive.google.com/file/d/1Lwc_nRIlbwCiaLkasONnYTHPJdzJuBqr/view?usp=sharing
Log : https://drive.google.com/file/d/1wvYAdaCqL9yvkJBYp_FNumlNstSgc1Y1/view?usp=sharing

Thanks

2

hello Guillaume,
If you compare att_despitch and attpitch you will see that your plane is unable to follow despitch. CG position and control surface size are two main parameters. CG must be as close as possible to the quarter mean chord and control surface about 1/3 of the wing. There is a dedicated thread in the development team category and 2 examples of successful tailsitters are given in the last 15 posts.

3

Thanks Losawing for your reply. I ve just succeed landing in Qmode only one time : Z84 Tailsitter 1st attempt - YouTube

I ve made larger elevons for my last attempt. I will read topics you mentionned.
Thanks again

4

Another attempt but the issue is still the same. Next step is to lowered the axis of the motors under the wing line of flight.
Enclosed the last log.

https://drive.google.com/file/d/1iP-imh5UqbBxWYKwyLrgcQLoWCh015V8/view?usp=sharing

I ve seen des yaw and yaw are very different and des pitch and pitch are closer than before.