APM drifts in loiter/position hold, alt hold is acceptable

I've read what I could find on the topic and most of them point to it being a compass or vibration issue.  Compass drifts slightly but stays in the correct direction +/- 5 degrees, so I don't think it's that.  compassmot was run which significantly improved compass.  Vibration looks acceptable to me, not the best but it should be low enough to hold position with toilette bowling or some drift.

Essentially what happens is as soon as it goes into loiter it starts drifting.  The most consistent drift is it pitching back and flying towards me.  Occasionally it drifts wherever I feel like.  I'm at a total loss of what to look at or try to tune.  If anyone could take a look at the logs and see if there is something I missed I'd appreciate it.

EDIT:  Using SimonK ESC's with 750kv motors, 9 inch props, on an HT-FPV frame with APM 2.5 and ArduCopter 3.0.1 loaded with default settings.

(ESC calibrated, compass/accel calibrated, compassmot run)

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  • I've been going through the same thing with the same suggested fixes but even alt hold isn't reliable. It's not "toilet bowling" or anything regular. It's all seemingly random. Kind of like my daughter when she was 2. Sometimes it will just hover at 20 feet for 30 seconds and then just decide to land someplace 30 off diagonally in a random direction. Then after hitting the ground, will decide it would rather fly for a bit and go back into position but 30 ft off.

    I've been suspecting GPS glitch, barometer glitch, gremlins and ghosts but I think I've narrowed it down to "it's alive!"

    • well I'm going to order some new lipos then get back to testing I'm having the same problem but when I had the same gear on a 900mm tricopter with the gps away from propellers it seemed to work better now  have it on a 450mm with the gps close to prop and it will drift left to right about 30 feet or just keep going up slowly I need it to hold position so I can test a object Avoidance system I been working on hope to be back in the air in a few days

      • Well... Im been making som reserch and looks like there are too many recomendations I missed out about the magnetometer. 

        1) distance from power and motor wires >10cm ...mine was no more than 6cm.

        2) twisted wires... I leave all of them as flat as posible because they fold better ;-D

        3) compassmot utility ... I didnt used it.

        I will do all of them and maybe on sunday I can make some flight-crash tests.

        • did auto tune now flies a lot  better some drift but that could be the wind because it floats back to position

          • Hi.

            Last sunday I made field tests with the quad.

            It performs wel. litle unstable at first with the default params but next I did the auto tune and everithing worked OK.

            I dont know exactly what was the major isue because I made lots of changes.

            1. Changed the GPS.MAG to a better and taller stand. Away from power wires.

            2. Recalibrated the Mag.

            3. Do a CompasMot utility run.

            4. Corrected the pitch direction on the radio stick.


            Now, it flies well and can do a mission with WP etc. RTL and geo-Fence works well too.

            • Great mine flies great after auto tune please post video

        • Hi. 

          I put a new stand for the GPS-mag and calibrated both, the internal and external. CompassMot is stil pending.... and didn't do any field test yet.

          Last nght I found one of the mayor isuses on my configuration, beleave or not .. it was the radio. Pitch stick on the radio was on the wrong direction. When I push the stick forward the PWM increses to te value to 1900, so pixhawk tihinks it has to incress pitch and moves the copter backward.

          So any time I tried to get the copter back It goes out and I ended hard landing it. ;-)

          Looks like it's not the fist time it hapend. 


  • did you get this fixed Im having the same issue looking for answers

  • Try adjusting trims...
    • have you guys fixed the problem? I also have the same GPS module NEO-6M and I found a video showing how to configure this module. But mine does not have flash memory, so I cannot save the configs. Apparently the default config is to automotive filter and we should use pedestrian filter. I believe the GPS starts rotate because it thing it is in a car that cant just stop and go back, it tries to turn around to go back to the WP. Probably the solution is to buy another type of GPS or buy one whit configs for quads already stored in it.

      If someone have the problem solved just let me know. Thank you.

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