Hey there, I have encountered a from my perspective very very strange error for the first time since flying PX4.
During a flight what was supposed to be a mission flight on a Fixed Wing, du to flight performance issues, I changed into Stabilized Mode and wanted to land my FW, but suddenly I got this error saying :
Critical: Failsafe activated: Autopilot disengaged, switching to terminate
No valid attitude estimate
All my failsafe settings are I have set to Return Mode, I don’t know where this terminate came from.
This then resulted in a horribly crash and my Plane broke 
The Firmware I am using is the 1.15.4 Stable version downloaded from QGroundControl
Hardware : Holybro 6X Autopilot
What can be the issue here?
That doesn’t sound good. Sorry about your crash!
Any chance you have the ulg file and can upload it to logs.px4.io and link it here?
No due to the crash the Flightcontroller and the SD-Card got totally destroyed…
was able to get some screenshots of some error messages and behaviour
And this was the errors i suddenly got and then it crashed.
Ok, what I can tell based on the screenshots and what you wrote is that the estimator actually no longer had attitude information, which means Stabilized flight is not possible.
I have never quite seen this, usually attitude control isn’t just lost like that, usually, unless you would loose all your IMU sensors, so that’s very strange. It’s possible that this is a software issue - of course - but I wouldn’t know where to look for it.
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Hi there. I’m both happy and sad to see that you encountered a similar problem. I had two flights in a row both with a similar setup. I used v.1.15.4 on a Holybro 6X on a fixed wing plane. One flight had a strange behavior as the plane out of nowhere in Mission mode started to increase climb rate by a lot which lad to a quiet high pitch value but I could get it back on track and after a while during a role maneuver (stabilized mode) it just terminated, and compass and gyroscope went black as in your case (I even got the same Unknown error). The second flight was even shorter and ended in the same situation. Both planes unfortunately completely destroyed therefore no log or anything. I checked a lot on the internet but couldn’t find anything (also controlled my failsafe settings again). With earlier Firmwares I never had this issue. Any ideas what it can be because right now I’m a bit worried how to proceed as I don’t want another plane to crash.
It’s possible that you have some telemetry logs (tlogs) saved by QGC, which could be useful if you can’t recover the actual flight controller or SD card.
You’ll the relevant folder on QGC → Application Settings → Miscellaneous → App Load/Save path.
And just below the folder path you’ll see checkboxes on when and how to save tlogs.
Replay the tlog: Replay Flight Data | QGC Guide (master)
Might even be possible too to analyze it further, and since it’s a Mavling Telemetry Log format you might be able to export some data using Mission Planner.
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Just wanted to chime in w/ a semi-related issue (seems to be a different cause) - Unexpected terminate when operating in Mission Mode.
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Yes I agree with that, it looks like some Software failure. I did not think this is Hardware related because I have done more then 100 flights with this hardware but on 1.14.3 and 1.15.1 on both FW and VTOL, I never experienced any error of that kind. But as soon as I changed to 1.15.4 Stable I got this issue in my 4th flight if I am not wrong, I am still trying to get out at least some log related graphs or something to share with you…
What should I look for in you oppinion? Hardware errors? Sensors?
Thank you a lot for this advice, I will have a look at it and will see if I can find something or recover in a different way…
FYI @ryanjAA have you seen that sort of thing?
Where you able to solve your issue? I notices as well that in my flight/crash the attitude, angular velocity, local position, local velocity and global position as invalid all of the sudden
