Limited drone control leading to crash

I’m using a hexacopter multicopter with Cubepilot, Arducopter 4.0.7 and Skydroid H16 R/C. My battery is a 6s 22000mAh li-ion and the drone has more than 50 flights under its belt. Recently we used this drone to carry a scientific sensor that was also transmitting at 2.4GHz, the same frequency as the R/C. The area of flight had a diameter of 30 meters by 20 meters height and the wind was calm.

After about 10 successful flights with this particular setup, I took off in Alt hold and immediately I notice that I had very limited control. The drone was moving in a circular pattern without any input and after a few seconds of trying to control it, I committed to crushing in order to avoid any third party damage.

Analysing the log file I notice plenty of EKF Yaw Resets most probably due to heavy payload, and large magnetic variances NKF4.SM. On the map, the drone seems to get GPS glitches of 50 meters or more. I have never experienced such large external (or internal) interference that affects the RC input on a flight.

Could you please help me figure out what was the problem with this limited controlled flight?

Could it be the transmitting frequency of the payload?

Flight log

Right after the GPS glitch Vibration FS activated, enabling Vibration Compensation, which is likely why it seemed like limited control. This is one of 3 things that will happen:

  • The vehicle will not change mode but its altitude hold will be less accurate than normal. The vehicle may overshoot it’s altitude targets and/or respond more slowly to pilot input.

We experienced something like this in our heavy-duty platforms due to the power lines of ESCs located closely to the magnetometer (in the GPS module) sensor. So this results in poor “in flight yaw alignment”. So you never seen this anomaly before in your 10 flights? How are your electronics located on the frame?

This may occur if your power lines interfere with the magnotometer. I strongly suggest you to take a closer look and place the module as far as possible from the power lines.

RC input can not be affected with the power lines in shot distances or electromagnetic waves (of course if someone not jamming you :smiley:).

I don’t think so since communication is modulated.
This might be because the heavy payload results in more power consumption of motors lead a high current at the power lines.

Thank you both for your answers.
What Dave suggested about the Vibration Compensation failsafe makes sense for the limited control authority.
Indeed, at least above the ground, the area of the flight had powerlines.

This is common when Vibration Compensation is activated. “Vibration” can be problem but poor positional information is more often what triggers it. In your case the GPS glitch was the final straw. Read the Wiki entry and look at the 3 Innovations in your log when the FS was activated and you will see why.

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I think he means the power cables from your batteries to your speed controllers (ESCs) and/or from the ESCs to the motors. Not power cables on pylons nearby! :slight_smile:

Yea, I fly all around those without issue. I even collided with one once while it was on an auto mission and recovered the log. Everything was good up until it hit and these were very large power lines.

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OMG :smiley: Interesting to hear that.

I think the circling after start sounds like a toilet bowl which is something which I would expect when adding something to the drone which alters the magnetic field.