VTOL nose down and lose altitude very fast after transition, I suspect changing to use air speed is the clue for finding reason

ArduPlane VTOL Plane
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1

(1) Situation :

My VTOL nose down and lose altitude very fast after transition.

after I engage auto mission, after 5 seconds, it suddenly nose down and nearly crashed to sea surface.

FBWB also works same. I tried this experiment more than 5 times and everytime the result was same.

after losing altitude and downing nose, I changed to QLoiter and very long time(more than 5 seconds) it couldn’t retrieve its altitude even though I put full throttle.

(2) Log Link :

(3) Previous Status :

I installed airspeed sensor but until now I didn’t use that(AIRSPD USE parameter was set to 0)

so my VTOL maybe used ground speed instead of air speed. in that time, it flew very well.

I tried FBWA, FBWB, Guided, Auto, RTL more than 20 times with this VTBird plane.

(4) Model : XuWing VTBird

(5) Flight Contorller : Pixhawk Cube Orange+

(6)GPS : Here3+

(7)Remote Controller (RC): H16 Pro

(8)Ground Control Station (GCS): Mission Planner

(9)Telemetry: Using the H16 Pro’s Hotspot

2

I found one of aileron servo was bad(it sometimes stuck)

and edited some speed parameters.

I will fix this problem and try tomorrow.