Hello everyone, could someone help me figure out why my plane crashed?
I took off normally in takeoff mode, and since the plane is overpowered and made of light foam, it gained speed very quickly. After climbing a few meters above the ground, I switched to autotune mode, and the plane suddenly nosedived. I tried to pull up using stick input, but it didn’t seem to respond.
Here’s the flight log.
The first thing I see is that your EKF3 is absolutely wrong (specifically the position and velocity estimates).
I check the main sensor (not the only one) from which these estimates are obtained (GPS). It turns out that you are flying with only 4 satellites and a very high HDOP (high is bad).
In these conditions Ardupilot should not have allowed you to arm the aircraft. Your solution was to disable the pre-arming verification system.
If there is a system that verifies that everything is in order to fly and you disable it you have to assume what can happen afterwards.
With all of the above your EKF3 restarts and your plane crashes.
Thanks for your support. That morning, I disabled the arm check for an indoor test. I made sure the plane had 8 satellites locked before arming. However, I believe ArduPilot should be able to handle GPS loss properly, correct? The plane flew well in takeoff mode, but it nosedived when I switched to autotune.
Anyway, I will turn on all nesssery arm check and test again.
How do I can view full log messages like you.
I am using plot.ardupilot.com and can not see EKF force reset message.
Oh I see. But I think EKF reseted due to I disarm after crashed. I think it is not related to why the plane nosedive when I switch to autotune mode.
This afternoon I also thought that this could be the cause of the disarm.
But that the quality of the EKF3 estimates was lousy, of that I have no doubt.
EKF3 was not active at any time during the flight. Active EKF type was 0 (=DCM)
DCM was of course lousy. Only 4 sats and no compass didn’t make the attitude estimate any better.
The crash had nothing to do with switching to autotune, but was caused by switching off the arming checks. The nose went down earlier, recognizable by the loss of altitude.
Rolf
I tested again this afternoon with all necessary pre-arm checks enabled. This time, I let the plane gain more altitude than before, but it behaved exactly the same as before. It still nosedived for several meters. Fortunately, this time it slowly recovered just 2-3 meters above the ground. I believe my mistake was starting autotune at level 8 at a low altitude, as level 8 is quite aggressive.
I often take off without GPS lock. When I don’t plan to use auto mode or RTH, I just use FBWA and acro modes without any issues.
Life might have other plans 
Indeed, Levels above 7 are not recommended.
I tried 8 after initial tune on 7 and it caused oscillations on my swordfish.
