Vtol 3.5m wingspan near to crash after transition failed

Hi All
After updating the firmware to the newest 4.5.3 in my VTOL it failed transition after about 1mn of fly and the plane was far away from me it switch to land mode.
i noticed that is a speed problem because the speed in CTUN was about 16m/s where in gps was about 40m/s .
Kindly look into this problem.
here imy log file:
(2024-06-08 08-06-39.bin - Google Drive)

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Hi All,
Today flight is okay after activating Q_option_19 and changing Q_fail_act to return home, note that Cube Orange Plus with F9P RTK GPS was a good Choice.
Any Feedback is much appreciated especially with CTUN.AS and GPS.Spd difference.
Thank you.

I will take a look in the evening (hopefully).

Do you have an airspeed sensor? If so ai would suspect it being covered during flight or wrong configuration of the sensor.

thanks for your response
for air speed , no i haven’t installed it yet.

I would recommend installing it as soon as practical because it makes transition easier and safer.

Have you configured transition parameters?


Hello and thanks for your answer,
unfortunately using airspeed caused me a lot of problems especially with the firmware version 4.3.x, so I prefer not to use it until i get a high performance one, but my problem remains the same, and I would like to know the answer to why there is such a huge gap between the CTUN.AS and GPS.Spd, epecially the plane has reached 40m/s but the controller didn’t capture that speed since CTUN.AS stayed low and the plane entered Q_fail_act and started landing after exceeding the time limit (20 seconds).
I really need at least some guidance on why this is happening, as this project is time sensitive and I would like to test my vtol again ASAP.
Thank You ALL.

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Like @LupusTheCanine said , I would highly recommend installing airspeed sensor for this big aircraft.

Get this :

I use it personally for my all the aircrafts, quite accurate.
Q_ transition becomes much smoother when your AP has idea of ALT airspeed for transition and Q_ASSIST helps to maintain aircraft stability when you switch to FBWA.

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Thanks alot Idiota_Keen for your advice
Yes the next step is to install an airspeed in my aircraft with a long pitot tube.
however teh actual behavior of the aircraft is very stable during takeoff, transition, flying and landing.
Thanks a lot to all the Ardupilot teams really Great job.

Try to keep airspeed tubing length under 15cm.
As it’s CAN bus , you can extend its wire length.

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Ok i’ll take in consideration your advice thanks.

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