Plane dived down and crashed after auto takeoff

Hello everyone,

I could use some help to analyze my flight log.
As a new Ardupilot user, my first and maiden flight using auto launch was a success (yes I know I shouldn’t have use auto for the maiden but it’s a heavy plane). But the second flight resulted in a crash as the plane dived down right after completing the takeoff mission and initiating a RTL.

Looking at the log it seems I made a mistake uploading the mission as it had two takeoffs commands, one for a 15 m and a second one for 50 m takeoff. However they seem to have been executed properly as the dive happen right after it switched to RTL.
So my suspicion points toward a faulty airspeed sensor: before takeoff it was logging a 60m/s arspd which is nonesense. I remember pressing the Preflight_calibration command before takeoff (while covering the pitot tube) and it changed to around 0, but it stayed around 0 during the flight as well.
Could it have forced the autopilot to try to dive down to get some airspeed? Since throttle value remained at 100% even after takeoff complete message it makes me think that could be the case.
Airspeed sensor worked fine the previous flight and I didn’t do an auto calibration nor a manual one.

Ardupilot version 4.0.8
Matek F765 Wing
GPS: M8Q-5883
Analog Airspeed Sensor Matek ASPD-7002
Plane: MFD Crosswind Mini

Thank you for your help!

Haven’t looked at the log, but you mentioned you are using an analog airspeed sensor. We don’t use analog airspeed sensors since long time ago as they were giving many problems. Drift, inaccurate just to name a few. You could also have had a “kink” in one of the tubes that connect the sensor with the pitot tube, thus preventing the pressure reaching the sensor. From what you describe, that seems the most likely cause.

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Ah interesting I didn’t know that analog wasn’t a good idea
Maybe the analog sensor not being recommended anymore should be mentioned in the Docs, I don’t remember reading about that.
I will switch to digital from now on
Many thanks for your reply

Well, I have to be careful here. I don’t mean in general not being recommended. For us, I2C airspeed sensors just work better because of what I mentioned.

Alright no problem I see what you mean