Crash when RTL ,Pos alt changed suddenly. is this a BUG?

It was on RTL at 140meter which I set this , But suddenly it went down ,I was so confidence this rtl ,I even didnt watch it , until I heard the “telemtry lost” from my RC, I realized it crashed.

SO : why the pos Alt will glith but that time the alt is good with GPS and Baro .
Is that a BUG of arduPlane v4.05
It flew with f405win n880 GPS

I upload the log , hope somebody help me to find out the reason ,and aviod this happen again.

@sunwon2018 you’ve got all GPS arming checks disabled, which allowed you to launch without noticing your home alt wasn’t set correctly, until ~5 mins into the flight your EKF finally fused GPS and the initial 295 m alt error got corrected.

why is it you unticked your GPS checks?

I got your answer but when the plane finally got to know where she is in reality, why did she hit the ground, knowing she will? Doesn’n make sense to me.

You took off too early. The plane was not ready as mentioned by Basti. The message “EKF2 IMU0 origin set” should be done BEFORE take off.
You can avoid it by set up a more stringent ARMING_CHECK.
It is not a bug. It’s a user error.

@Gabor_Csontos I try to explain it in your words: The plane doesn’t “knew” where it is. The plane started to “know” it’s relative position at the moment of “EKF2 IMU0 origin set”.
Unfortunately a discrepancy of “POS.RelHomeAlt” of approximately 400m and “BARO.Alt” = 140m as used by EKF2 was left. The autopilot tried to fix this by descending …

omg, I understood, Thank you . I disabled it because I did some test ,I need arm it indoor …

Thank you very much , I should wait till the GPS hdop < 1.0

Yes , I did … it was too early. cause that time I was testing the 4G video transmiter. And It cost the LTE data, It spent the data very fast,like one hour 1GB , SO i just wanted to take off soon ,and forgot to check the HDOP. and then When I fly 2KM away I lost the 4g connection , that means I have no vison on my cellphone , I have no choice but set RTL , then EKF finally fused GPS on the way back home , and then that bad thing happend …

Wont make this simple mistak again ,Thank you

@sunwon2018 no offense, but that’s exactly what the arming checks are there for. i’d have lost quite a few airframes for sure if i hadn’t been noticed by prearm messages that something wasn’t ready for launch yet…

Yes , you are right . I have the GPS arming check enabled today . just incase i will take off in hasty again.
thank you again.