Compass issues with AC 3.3


I am using AC 3.2.` on pixhawk and it works good.

When I uploaded AC 3.3 I got compass issues, I was getting errors compass variance

Also when I tried to fly , I almost crashed it, my tarot got very unstable and banked to left and right

any thoughts about it?



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  • I agree on that, you should keep the compass away from high current wire. I remember when the AC of my grandmother's room was getting damaged and pouring water on the walls, one of the neighbour suggested to call the professionals who will look after the issue and will give some helpful hints that will cover the future problems if they face any.

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  • Hello,

    Don't know where to post my issue, but I think it's related to compass issue. Or IMU1 or IMU2 issue.

    I'm not really familiar how things are going inside the Pixhawk, with IMU sensors and EKF. It's a bit complex, but maybe developers can help.

    Very powerful, just the core things on board:

    Y6B carbon frame
    5010-360KV motors
    17x5.5 CF props (balanced)
    30A BLheli ESC
    5.2 Ah LIPO
    X8R and Taranis radio
    NEO-M8N GPS with compass
    v3.3.2 ArduCopter Y6B

    The whole system is calibrated and pre tested, and necessary parameters set via Mission Planner.

    The flight:
    Calm weather, 1-2 m/s wind max. Takeoff was normal in stabilized mode. Copter was almost climbed in a steady position. Climbed to 3-4meter height. I've set back the throttle and climbing stopped at around 4 meters. And there the copter started drifting away from me to the left side.
    I wanted to direct it back to me, but was still drifting away and ahead.
    Turned the copter's nose towards me with yaw, and pushed the right stick to change flight direction but no respons. Still drifted away.
    Copter was about 100meters away from me, descended a little, and hit ground around with speed of 10-15 km/h. Lawnmover mode 
    Just minor crack in plastic part of landing skid.

    2nd attempt:
    Takeoff normal in stabilized mode again, climbed vertically to 3-4 meters again to headwind, and there a weird thing happened.
    Copter made a swinging to forward and back, like if it would hanged in the CG and pushed from the back, and then immediately turned to its left side and crash landed.

    I have log file attached. I'd more than happy if someone could help to analyze the log file that what could cause this faulty operation.
    I suspect some kind of disorientation of Pixhawks inertial system. But there was no bad AHRS alam pre flight.
    Bad quality GPS maybe? SAT coverage was 8 or more at the time of the flight, and HDOP close to 1.0.

  • I think the best solution is to just recalibrate the compass in an open field. avoid doing it inside the building since there are hidden wires. keep compass away from high current wire. the problem should get resolved. also check orientation of compass.

    • you will be right!, yesterday I had an another issue, hexa, custom build just just like DJI 550,  on APM2.6 with extrnal compass,   it was flying in stabilize mode, but position hold was bad, the quad was jumping up and down up and down,  for the second attempt, it was holding the position and went down, I was able to recover it, so I didn't crash, anyway I looked at the log, and there was some GPS issues, so  I need to try again, maybe the GPS didnt lock when I was taking off, or whatever hmm

      I will try it all again today

  • Hi, despite the BAD AHRS errors I get even when the copter is standing still, I also now have problems with the compass...

    I am running Copter 3.3.2 on my Hexa.

    I just did 2 compass calibrations.

    First one with auto dec, second one with declination set to my town.

    Why are the compass 2 (internal compass?) offsets so incredibly high?

    The wiki says that the sum of all absolute values shouldn't exceed 600... Well, I have nearly 2000!


    • Hi,

      thanks for your answers.

      I changed the mounting from a 3D printed case to a selfmade mount that uses 4 screws through the holes in my AUAV-X2 board.

      It just came to my mind that those screws are causing the trouble with the compass.. will try to find M2 nylon screws..

      Now I just have to find out, what's causing the Bad AHRS error all the time..

      will check baro, but the board is really high quality, so it shouldn't be the cause..

      • Regarding your bad ARHS readings with the Pixhawk, I just want to remind you about the barometer sunlight problem as you said you are using your own 3D printed case.

        (with the APM2 I could get baro drift by shining a maglite torch onto the controller)

        • I got rid of the 3D printed case and am using no case now, as it is too high to fit between the 2 center plates without producing vibrations.

          I am aware of the sunlight problem, thanks for reminding.

          Just did the still standing baro test and it climbed to 6,6m in around 1 hour...

          The BAD AHRS error however didn't come back yet.

          I disabled the internal compass now until my nylon screws arrive.

          • For compass slow drift is not problem, it is caused by the heating, most of the barometers doing so.

            Bad if oscillatiing in height more than 20-30 cm with period several seconds.

      • Dave, let us know if it solves your issue.
        I have an auav-x2, and have never gotten its internal compass to work properly.   It's not very close to any metal (it is a small frame, so there's a steel frame screw maybe a couple cm away).
        But, even sitting on my workbench, I can't get it calibrated.  The offsets are very high, and north doesn't point north.  Pixhawk sitting on the same bench is fine. 

        I have disabled the internal compass on my auav-x2 copter, and it works great w/ the external one.

This reply was deleted.


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