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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      • any one fix this problem?

        • Hi DR WHO ....  

          Did you fix this problem .... I have the same isue. AltHold works OK and retain altitude even in poshold mode but in poshold it start to drift away.

          I'm a really new pilot so when it drift away I ended doing an emergency landing ;-( 100 m away. 

          GPS looks OK with 3D fix and 1,0<hdop<1,5....

          My GPS is a NEO-6. I have a Neo-8 wich I can replace but I think i'ts not the problem.

          • No not yet I'm going to try moving the gps up from the propellers but please keep me posted on your progress

            • OH yet make sure you hoover above half throttle that fixed it so it would even work but it still drift to far

  • I am having this same issue.  I purchased the complete arducopter setup and all flew good.  I wrecked it rebuilt it and still flew fine.  I swapped frames, went to an F450, and now my loiter and Alt H are acting real strange. 

    Loiter is all over the place.  It seems if I leave it be when I first turn it on it holds for a second but when I move the sticks it just continues off in that direction without stopping.

    Loiter and ALT H are playing with the throttle also.  Like 35-45% throttle changes which is causing the craft to kind of bounce a little in the air. 

    I also notice when I am plugged into the computer when I look at the flight planner I notice it drifts all over the place just sitting on my desk.  It seems to show a good 30-40ft drift in any direction.  Just floats around.

    I am showing 3D Fix on the flight data but how can I see how many Sats. I am locked onto?

    I have tried reducing loiter PID to .5

    Re-calibrated the compass

    Re-calibrated the Accel

    Both about 4 times lol.  What can I do to get this resolved?  I am not the best pilot and need some assistance with my flying haha.

    Standard Arducopter kit.  850motors 10x4.5 props, apm2.5 w/ internal compass?

    Is their a "place" the GPS needs to be?  I have it in the front of the bottom plate.  It gets good sky view but it an inch away from the APM itself.

  • Not to hijack your thread, but I have pretty much the same issue.  I originally thought it was my compassmot (180+%), so I setup an external compass (6%), but it's behaving exactly the same.  Stabalize and alt-hold are very acceptable, but put it in loiter and it starts to pitch, increasing until I put it back in alt-hold or stab. 

    F550, 750kv motors, 3.0.1, external compass, 10" props


    Here are my logs in case anyone can see a problem.

    logs.rar

    https://storage.ning.com/topology/rest/1.0/file/get/3692782957?profile=original
  • Updated log

    2013-07-24 10-08 32.log

    https://storage.ning.com/topology/rest/1.0/file/get/3692782630?profile=original
  • No sign of it even going into loiter in those logs. Its just going into alt-hold, which probably explains your drifting:

    1594 MODE, ALT_HOLD, 599
    2044 MODE, STABILIZE, 599
    2734 MODE, ALT_HOLD, 602
    2972 MODE, STABILIZE, 602
    3402 MODE, ALT_HOLD, 617
    4323 MODE, STABILIZE, 616
    5401 MODE, ALT_HOLD, 612
    9262 MODE, STABILIZE, 622
    9947 MODE, ALT_HOLD, 622
    11023 MODE, STABILIZE, 626

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