**crash** ev:motors_emergency_stop

Hello All,

I could use a little help determining what caused a crash of a VTOL Drone.

It was the maiden flight. The plan was to test all of the qmodes and if they went well initiate an autotune.

Took off QStabilized, transitioned to Qhover and finally to Qloiter. The drone was very stable in qloiter and responded well to pilot input.Initiated qTune. While in qtune the battery voltage steadily decreased to 21v, which triggered my battery failsafe. The drone stopped qtune and switched modes to QLand. Although it seems like it should have switched to QRTL instead of QLand (we’ll save that discussion for another thread). As the drone was approaching the ground, I added a bit of throttle to arrest the rate of descent. About that time, the drone abruptly pitched nose down and crashed into the ground nose first. Even from 5ft, the foamie Freeman 2300 was destroyed. Fortunately, all of the electronics are salvageable.

Immediately following the crash, after numerous swears, i suspected a brown out or voltage sag was the cause of the accident. The logs don’t support either theory. The battery voltage never dropped much below 21v. I am using a Mauch PowerCube V3 BEC that provided impressively stable voltage to the Pixhawk.

The big red flag (literally) is an EV: MOTORS_EMERGENCY_STOPPED message. So the motors were command to stop, which lead to the crash. It wasn’t a pilot initiated emergency stop. What would event would trigger this command?

After reading the notes and warnings associated with qland, I suspect the Pixhawk thought it was on the ground and commanded a stop. Although my baro readings look good throughout the flight.

Any help diagnosing the root cause of this crash is much appreciated. I’d rather not crash the next one I build.

Thank you,


Link to the log.

You have E-Stop setup on RC3_OPTION. When you added throttle it went over 1800us and the E-stop was triggered. Not sure how you manged to end up with E-Stop on your throttle channel but that was certainly the cause of the crash.

@rmackay9 @peterbarker Another good reason to kill rcmap.



Thanks for the reply and assessment. I do have an emergency stop linked to the throttle. I used a logic output on the taranis, which is set to kill the throttle if rotary knob S2 is full clockwise. Looking at RC3out the PWM went above 1800us several other times. Where is the E_stop limit set to 1800 US? And why does E_stop activate at 1800US?



FYI when it believes it has landed, it would simply disarm. It would not initiate an emergency stop, which is a whole other thing. Pete pointed out the problem, I just wanted to clarify how the vehicle disarms on landing for you.

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thanks for the clarification

That’s just how the aux switch functions work. The input is considered high >1800us. Mid is 1200-1800. Low is <1200.

well shit. I figured I did something stupid. And everything was going so well. Hard lesson to learn, but it’s good to know that I caused the error.

Thanks for the explanation.