The plane crashed.
Loss of altitude on turns. Please help understand why the accident occurred.
In AUTO mode, when the plane moves to the next waypoint that is at an angle, it loses altitude.
Model Heewing T-2 Cruza.
Binary log file here
To me it looks like poor configuration, there is an extreme mismatch between TECS airspeed estimate (along with AIRSPEED_* parameters) and GPS speeds.
During the descent TECS is in underspeed state.
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The compass reliability estimates became invalid immediately after take-off (XKF4[0].SM>1). Similarly, velocity estimates were so inaccurate (XKF4[0].SV>0.5) that they were within 2% of being invalid. As a consequence of the former, an emergency yaw reset occurred and for the remainder of the flight there were no compass estimates (XKF4[0].SV=0).
With all this the TECS system is no longer reliable and given that you were flying an autonomous mission anything can happen.
On the flight you had two nose stalls (divergence between pitch demanded and pitch executed). The second one caused the accident.
There were not 2 but 3
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It appears that the pitch controller is not properly tuned and the airplane is unable to track changes in target altitude, resulting in altitude oscillations.
For an airplane that has not been properly tuned, the tracking error for changes in target altitude could be 20 meters or more.
By making the altitude of all waypoints the same, the risk of a crash would be reduced for the time being.
A better solution is to perform AUTOTUNE.
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To be more specific, AUTOTUNE at level 7 or maybe even lower.
Configuring and tuning TECS will be necessary too.
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Thanks for the reply. This model does not have a speed sensor. Only GPS can provide speed information. So I don’t understand why the underspeed state appears.
Thank you very much. I understood your conclusion regarding the compass. Your second thought is regarding the desired and received pitch. Perhaps the pitch channel is not tuned properly, I was hoping for the factory settings.
Thank you . I completely agree about the inconsistency of the pitch data.
I see that the barometer and GPS gave the flight altitude correctly.
And thanks for the advice to perform the AUTOTUNE procedure! (I thought it only applied to copters 
).
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Thank you very much!