Quadplane without airspeed sensor problem

or i can change the title to “quadplane transition problem”

hi, sorry for my bad english…
i have been testing Quadplane for a while. i never use airspeed before.
it was great if i “play” with transition from Qhover to FBWA and FBWA to Qhover.

2 weeks ago i try quadplane auto mission for the 1st time, the result is “not good”.
After vtol_takeoff the horizontal motor seem to spin nicely for about 10" (i set Q_TRANSITION_MS to 10000), what happen next is the horizontal motor act sooo weird, its looks like on and off. quadplane heading to waypoint 2 with all of 4 motor spin (quad mode) and horizontal motor on and off, ground speed is only 3 m/s. i try different setting, its just no luck. the horizontal motor wont spin correctly.

So i plant airspeed sensor to my quadplane and test auto mode. its work just great (unlsess the QRTL mode is not stable-- but that’s another problem and i can change it to vtol_land).

i was thinking the problem is the airspeed sensor (for awhile).
2 days ago i try to simulate quadplane on SITL (the target is try different setting, so i can use quadplane without airspeed sensor). what i found next is really interesting…

i don’t think the airspeed sensor is the real problem, its the “TRANSITION”.
on this video (skip to 2:25)

the transition (to quad mode) triggered after airspeed drop below Q_ASSIST_SPEED and never transition back to plane mode again.

i have alot of log file about quadplane auto problem, but is so big ( almost a day long). if someone interesting, i can appload it.

owh, btw i never try to drop airspeed below Q_ASSIST_SPEED with use_airspeed =1.
ill try and report soon.