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Advanced Phantom 3 Advanced Flyaway (Almost)

Discussion in 'Phantom 3 Help' started by Douglas Struble, May 18, 2016.

  1. Douglas Struble

    Sep 11, 2015
    Likes Received:
    Taylor, MI
    I was wondering if anyone may have some technical insight on a flyaway I had today. I have read about flyways before, but thought it almost impossible for it to happen. I have only been using quad copters for a year now. While I have had crashes, this is the first time I have had a flyaway and it was very alarming. Fortunately with a lot of struggling, I was able to fight it and get it back. I fly it for both business and personal use. Whenever I am out in nature, I never ever have problems. Today I was using it for the first time this year shooting a TV commercial for a junk yard. I was getting compass errors, so recalibrated it a couple times until all lights were green. See attached photo. Plenty of space around it away from the autos too. I let it hover for a while and it seemed okay, so I took off and then it went flying off in the opposite direction. The autos don't seem like they would be enough to cause that sort of a problem/interference. Thoughts? Also, wouldn't the onboard computer be doing a hand shack with the other sensors like the GPS? You would think the GPS would add as a redundant backup telling the compass, hey you are screwing up. Really weird. Any insight would be greatly appreciated.

    Attached Files:

  2. msinger

    Approved Vendor

    Oct 30, 2014
    Likes Received:
    It sounds like you had a bad compass calibration. That's not surprising though since that location appears to be chock-full of metal.
  3. Mimoid

    Apr 18, 2016
    Likes Received:
    This sounds to me like a typical compass calibration error. You have calibrated the compass at a wrong place, and thereby messing up the automatic systems of the Phantom. Here are my tips on how to get minimize the risks for this to happen:

    1) Find a good place to calibrate your compass. Preferably an open grass field far from any kind of magnetic anomalies: no cars, no buildings, no concrete, no antennas and no big slabs of rocks. No phones in your pockets.

    3) Put down the remote at least 15 feet from the drone and do the compass dance. The lights should be slowly blinking green.

    3) Perform a test flight. Climb to 300 feet and fly a predefined rectangle 1000 feet wide and 1000 feet long. Make sure to turn and fly in each cardinal direction (N-E-S-W).

    4) During the test flight, pay close attention to compass issues, like (the obvious) compass error messages or (the not so obvious) tilted gimbal issues. If you see anything funny, land and find a new field for calibration.

    5) If things go fine, consider your Phantom to be perfectly calibrated to the Earth's magnetic field lines in your generic geographic location.

    When going flying from now on, do not recalibrate again (unless travelling like 100km or so).

    Why? Every new calibration is a risk for introducing compass issues that might incapacitate the automatic GPS-based navigation functions. This also includes Home Lock and the failsafe RTH.

    From now on, if you run into compass error messages at startup or a steady drifting or circling direcly on takeoff, land and find a different spot to take off from, as there might be some kind of geomagnetic anomaly at that precise point (e.g. ferrous objects nearby or underground).

    If you recalibrate your compass there (as you did at the junkyard), you actually "program" the Phantom to extend the correction for that local anomaly through the entire flight path, (and actually for all future flights too), and then run into all kinds of compass issues as soon as you leave the disturbed area. You will thus risk ending up with severely crippled GPS functions and in the worst case, a possible flyaway as result. Which you almost did.

    Ask me how I know.

    #3 Mimoid, May 19, 2016
    Last edited: May 19, 2016
    matt74 likes this.
  4. Paul Schulze

    Feb 23, 2016
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    Knowing what I know about the earth's magnetic field and P3s is that for the compass to work properly depends on the uniformity of the field. If the local field, especially the tangential component, is altered drastically, like any compass, directions are screwed up. A junk yard has the potential for more field change than moving 100 miles away. I would venture to guess that once the drone moved away from the junk yard you were able to gain proper control.

    Concrete slabs have some rebar in a whole lot of sand, rock, and cement yet compass calibrations can fail easily. The calibration is basically to obtain a sample of the undisturbed local field which it assumes does not change much over the flight area of the drone.

    Sent from my iPad using PhantomPilots mobile app