Mission aborts followed by crash

Hi everyone:

I’m flying a DJI F550 hex. Just installed a new Pixhawk 1 module from mRobotics and flashed with PX4 1.8.0. During testing, I gave it a simple mission to fly. It started the mission, but quickly aborted going into Descend mode (whatever that is). I put it in Loiter mode to save it (actually QGC said it was HOLD mode), but it kept descending. I gave it full throttle but it ignored all attempts to control it manually. Then it crashed gently into a bush.

Here is the flight review:

Hope you can provide some answers.


Descend mode is a failsafe mode that has the vehicle descend to the ground without requiring horizontal positioning.

Your vehicle entered this mode because it lost it’s position fix. This is also why going to hold mode did not work.

Your log shows that the GPS did not lose satellites. But the estimator watchdog complained about the mag. Mag fusion is necessary for proper position estimation, so this might have been the reason for the “no global position” warning.

It is difficult to interpret the meaning of the estimator watchdog bits and particularly what their consequences are as there is no documentation of this that I’m aware of. So I can’t say for certain that the above is accurate. Perhaps @Paul_Riseborough or somebody else who is more familiar with the estimator can provide more help.

Refer to the uORB message definition for estimator_status message https://github.com/PX4/Firmware/blob/master/msg/estimator_status.msg

There are large errors in the magnetometer data. The measured field strength is varying significantly and magnetic field and magnetic heading innovations innovations are large. This causes the EKF to have the wrong heading which means it is unable to use the GPS to correct the inertial navigation calculation.

Today I re-calibrated all sensors and flew it again with better results. However there are some error messages in the logs that I have not seen before, regarding “log_writer_file low on stack: 284 bytes left” Can anyone shed light on what this means? Also I frequently get a message that microSD card cannot be read. What is happening with this and what effect does it have on the flight? I noticed that this usually occurs during a mission, but the mission always completes.

Anyway, here are the two flight logs from the missions I ran today. There is still some estimator watchdog activity, but much less than before the re-calibration.

Also, what is the chart labeled “acceleration power spectral density” and what does it mean? What can I glean from this data?



As usual , thanks for the help.