Resume Mission, RTL, Crash


I just crashed my Flamewheel 550 with Pixhawk controller board running ArduCopter 3.2.1. It was not first flight with this setup, but I was just the second flight after updating to 3.2.1. In the first flight I was playing around a bit with stabilize, althold, loiter and RTL modes. In the second flight I wanted to test an automated mission. I planed a simple course within my line of sight using the Mission Planner 1.3.30. The copter was sitting on the ground and I started the copter with the “Resume Mission” action in the Mission Planner (connected via 3DR radio). It took off and proceeded to waypoint 1. I noticed that I forgot to reduce the height of the waypoints, so it was climbing up to 100 meters. That was a bit high for my taste, so I wanted to bring the copter back and change the mission. I flipped the mode switch on my RC transmitter to RTL. The RTL mode was activated (according to Mission Planner’s voice out) but also the engines stopped and the copter fell out of the sky.

Back home I wanted to check the log files, but the SD card from the pixhawk is missing! It seems, it got lost during the crash! WTF? This can happen?! I even went back to the crash site to find it, but I had no luck (although I found the exact spot of the crash, there were some other parts left over).

Has anyone experienced something like that before? The copter was not armed before issuing the “Resume Mission” command. What caused the engines to turn off…?! Was it a mistake to use “Resume Mission” instead of “Auto”?

Also, I’m not sure were my throttle was when activating RTL, probably all the way down because I did not take off manually. Might this be the cause?

ArduCopter V3.2.1 (36b405fb)
PX4: ce602658 NuttX: 475b8c15
Frame: HEXA
PX4v2 002F001C 31334705 39343031

Best Regards,

Any logs from the groundstation?

Thanks for asking! I didn’t know the tlogs are created automatically… :slight_smile:

Checking the tlog confirms that the throttle stick was down. The servo_output shows that the ESCs went to standby the moment I flipped the mode switch to RTL. There was no mechanical failure.


In the graph you see that the copter was flown manually before starting the mission, first in loiter mode, then stabilize and then disarmed. Re-arming was done by the “Resume Mission” command through the ground station. RC mode switch remained in “stabilize” position until I flipped it to RTL. … /rtl-mode/ states:

The throttle stick controls the altitude while returning or loitering above home and not the motors directly.

What does that mean? Has this crash really been caused by the setting of the throttle stick? When activating RTL, the copter should be autonomous until it loiters over the home position, why is the throttle input considered at all? Would this have behaved differently when I had activated RTL through the ground station instead with the RC mode switch?


Damn. Seems my the MPU6000 in my pixhawk is destroyed:


Since the crash I have trouble booting the pixhawk, it tries to start but aborts with a double beep and a solid red LED indicator.

I should add that the microSD card was lost during the crash and has been replaced with a new, empty one. It seems to be found because an “APM” directory has been created on it, but no boot.log. I hoped that the new SD card could be the cause of the boot issues, but after checking the IMU output in the tlog, I think it is really the IMU that is broken.

Isn’t there another IMU on the board? Is it possible to activate that one as primary IMU and to ignore the broken MPU6000? Or could I connect an external one over the I2C bus?

Best Regards,

Push. Engines stopped on RTL? Anyone?

too little information in .tlog - the .bin file would be useful.

And no, throttle stick down will not stop motors in RTL (or any altitude-controlled mode)