# Flight termination **URL:** \ **Category:** PX4 Autopilot\ **Created:** [August 12, 2025, 7:11am UTC](https://discuss.px4.io/t/flight-termination/46964 "2025-08-12T07:11:20Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![ShlomiRR](https://discuss.px4.io/user_avatar/discuss.px4.io/shlomirr/32/18890_2.png) [@ShlomiRR](https://discuss.px4.io/u/ShlomiRR)\ **Post date:** [August 12, 2025, 7:11am UTC](https://discuss.px4.io/t/flight-termination/46964/1 "2025-08-12T07:11:20Z")
why i had flight termination during this flight? > **[Flight Review](https://review.px4.io/plot_app?log=6da88ceb-dcde-4489-849f-4a46da806fd9)** ---
**Author:** ![JulianOes](https://discuss.px4.io/user_avatar/discuss.px4.io/julianoes/32/30_2.png) [@JulianOes](https://discuss.px4.io/u/JulianOes)\ **Post date:** [August 13, 2025, 8:59pm UTC](https://discuss.px4.io/t/flight-termination/46964/2 "2025-08-13T20:59:19Z")
I’m not so sure, but I have come across a similar report recently: [Sudden Motor Stop Mid-Air [Autopilot disengaged, switching to terminate]](https://discuss.px4.io/t/sudden-motor-stop-mid-air-autopilot-disengaged-switching-to-terminate/45042) For some reason it could no longer go into Stabilized mode. ![image](https://discuss.px4.io/uploads/default/original/3X/3/e/3e8ffbe57521bda2fb0e1d7a12a38a9c80b5b5a5.png) It basically had no longer an attitude estimate: ![image](https://discuss.px4.io/uploads/default/original/3X/2/f/2fe78345255a6a286f0fed105e03497eeafc9e68.png) Not sure why that would happen though. What I can see is that you have both high accelerometer bias warnings and at the same time mag warnings. The mag warnings are due to the fact that the compass is measuring a lot of interference from your motor/ESC wiring, as you can see given the correlation here: ![image](https://discuss.px4.io/uploads/default/original/3X/9/6/964ba49f77c21aa5a9c095944d43e369d69bba12.png) ---
**Author:** ![ShlomiRR](https://discuss.px4.io/user_avatar/discuss.px4.io/shlomirr/32/18890_2.png) [@ShlomiRR](https://discuss.px4.io/u/ShlomiRR)\ **Post date:** [August 14, 2025, 8:05am UTC](https://discuss.px4.io/t/flight-termination/46964/3 "2025-08-14T08:05:05Z")
what can cause bias warning? ---
**Author:** ![JulianOes](https://discuss.px4.io/user_avatar/discuss.px4.io/julianoes/32/30_2.png) [@JulianOes](https://discuss.px4.io/u/JulianOes)\ **Post date:** [August 14, 2025, 11:13pm UTC](https://discuss.px4.io/t/flight-termination/46964/4 "2025-08-14T23:13:30Z")
Bad calibration and/or bad vibrations. ---
**Author:** ![simopanzer](https://discuss.px4.io/letter_avatar_proxy/v4/letter/s/90db22/32.png) [@simopanzer](https://discuss.px4.io/u/simopanzer)\ **Post date:** [August 17, 2025, 9:42am UTC](https://discuss.px4.io/t/flight-termination/46964/5 "2025-08-17T09:42:58Z")
@ShlomiRR thanks for sharing your experience. We had a very similar issue; in our case we used a VTOL in standard quadplane configuration and we experienced the issue during FW mode. We were using PX4 v1.15.4. It looks like flight termination was triggered in flight, leading to loss of control and subsequent crash. Unfortunately we could not recover the .ulg log, but looking at the telemetry .tlog file logged by QGC we were able to reconstruct the following: - “Preflight Fail: High Accelerometer Bias” - In the next seconds, attitude estimate was declared invalid (we got NaN values in the ATTITUDE\_QUATERNION mavlink message), and immediately after, also the angular velocity estimate was invalid - “Failsafe activated” - “Preflight Fail: Flight termination active” I did some research and I found this other issue which looks related: [Autopilot disengaged, switching to terminate](https://discuss.px4.io/t/autopilot-disengaged-switching-to-terminate/46655) @diana_diaz Based on your log I see that at a certain point the flag `estimator_sensor_bias/accel_bias_stable` goes to 0, and from that point on the `accel_bias` estimates diverge and saturate to the limit value. We never experienced this kind of issue before with previous PX4 versions; I guess it might be related to the fact a new EKF implementation was introduced in v1.15, @JulianOes what do you think? I also suspect it might be related to IMU autocalibration. ![Screenshot 2025-08-17 114018](https://discuss.px4.io/uploads/default/original/3X/a/8/a84c6cfe5980bece5f616feacee373ba309f8859.png) ---
**Author:** ![MikeRogerIt](https://discuss.px4.io/user_avatar/discuss.px4.io/mikerogerit/32/19994_2.png) [@MikeRogerIt](https://discuss.px4.io/u/MikeRogerIt)\ **Post date:** [August 18, 2025, 12:12pm UTC](https://discuss.px4.io/t/flight-termination/46964/6 "2025-08-18T12:12:18Z")
Hi there. As the topic came up again and I myself had such an unfortunate experience before I looked more into it again and have the impression that using the quick mag calibration that was enabled in v.1.15 could have led to this result. I just recently red more into it and it seems that quick mag calibration can’t replace the normal one (as I assumed). And as far as information out there are concerned it can lead to yaw estimate errors and also issues with ekf. Maybe that helps? ---
**Author:** ![simopanzer](https://discuss.px4.io/letter_avatar_proxy/v4/letter/s/90db22/32.png) [@simopanzer](https://discuss.px4.io/u/simopanzer)\ **Post date:** [August 28, 2025, 4:19pm UTC](https://discuss.px4.io/t/flight-termination/46964/7 "2025-08-28T16:19:27Z")
@MikeRogerIt thanks for sharing your experience. Based on my understanding, there are two issues to be addressed here: 1. investigate why the EKF fails, resulting in an invalid attitude estimate; 2. discuss whether it is appropriate that the failsafe state machine does lead to flight termination in case of loss of attitude estimate (for instance in manual flight, fixed wing mode, one would still be able to fly even without attitude estimate available). In my opinion point #1 is the most critical one - losing the attitude estimate would be catastrophic with multirotors in particular. To be honest, I do not feel much confident flying knowing that the EKF may fail at any time… There have been already multiple crash reports which look related to this issue (and there may be even more unreported…), and it might occur again if this is not addressed. I think this is an issue of concern and should be investigated more in depth. Any comments? @JulianOes ---
**Author:** ![dakejahl](https://discuss.px4.io/user_avatar/discuss.px4.io/dakejahl/32/20420_2.png) [@dakejahl](https://discuss.px4.io/u/dakejahl)\ **Post date:** [August 28, 2025, 4:51pm UTC](https://discuss.px4.io/t/flight-termination/46964/8 "2025-08-28T16:51:02Z")
Looks like this issue > > > \### Solved Problem > I recently crashed a VTOL vehicle in FW after disabling bot…h GPS and baro fusion in air, which made it switch from AUTO to TERMINATE mode. > > \### Solution > \- remove mode requirement for a valid altitude estimate from DESCEND > \- similar to \[what is done for MC\](https://github.com/PX4/PX4-Autopilot/blob/e234b583b75b0500e1584ca4c2dbcceef15eb52e/src/modules/flight\_mode\_manager/tasks/Descend/FlightTaskDescend.cpp#L50-L59) handle invalid v/vz in the FW position controller. For FW we in case of invalid v/vz measurements would likely just want the thrust to be 0, such that the vehicle glides down to the ground while still tracking the loiter (assuming it doesn't stall). > > \### Changelog Entry > For release notes: > \`\`\` > Improvement: Remove mode\_req\_local\_alt from Descend mode and handle it in FW position controller > \`\`\` > > > \### Test coverage > Can be easily tested in SITL: Disable Baro fusion (EKF2\_BARO\_CTRL), then takeoff in auto mode, then disable GPS fusion --\> with current main it goes to Termination mode, with this PR to Descend. ---
**Author:** ![system](https://discuss.px4.io/uploads/default/original/3X/7/3/73ce918bdcd64854de904f0c8d9ab70ca9723f2a.png) [@system](https://discuss.px4.io/u/system)\ **Post date:** [November 26, 2025, 4:51pm UTC](https://discuss.px4.io/t/flight-termination/46964/9 "2025-11-26T16:51:35Z")
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.