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Compass error.

Discussion in 'Pro/Adv Discussion' started by maxwell smart, Apr 17, 2016.

  1. maxwell smart

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    I have P3P and FW 1.5 I was flying last night, at about 3,000 ft out I got loss of signal ,then go home kicked in. Then I got compass error. I am glad this happen at night because I have a bright strobe light on my Phantom.
    I could see on my Navida Shild that the return home was not going back to me. So I corrected cores and took back control.
    The screen sead GPS Compass error.. If it would have bin daylight I would have lost it. As I got the P3 back in sight I could see it was now very high. So as I was bringing it in closer I was also bringing it lower. I could see the P3 clearly now it was over the naibbers house. [ there are lots of trees here] I was trying to get down lower and the P3 was trying to go north ,and I mean it had a mind of its own. It was still vary high up. I gave it down throttle and it just started to fall, I thought it was all over.
    And all this time I am trying to keep it from flying North. As it fell very fast, I let off the stick and it came back alive. I could not believe it. It was about 30 feet up now, so I brought it over head and down, as it got close I tried to grab it ,and as soon as I let go of the sticks it shot to the north again, just missing the phone lines. It took 3 tries to get a hold of it.
    Well I got it home and safe now. I have no idea what caused the compass error. I don't know anything about Healthy drones, Or flight data. I haven't even ever done a FW upgrade.
    I will do a compass cal and IMU cal today. Anyone have this happen before?? If it had been daylight I would have had a fly away.
    Thought I would try to tell you guys what happens with a compass error. My first, and I hope last.
     
  2. garykeithmead1

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    You can use your radar to see aircrafts orentation.
     
  3. maxwell smart

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    Is there a flight record in my Nvidea Shield ??
     
    #3 maxwell smart, Apr 17, 2016
    Last edited: Apr 17, 2016
  4. maxwell smart

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    I do have the flight on my shield. I just don't know how to export it to here.
     
  5. Meta4

    Meta4 Moderator
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    Go to http://www.phantomhelp.com/LogViewer/Upload/
    Follow the instructions to upload your flight record.

    If you are using an Android phone or tablet, the flight records are in Internal Storage/DJI/dji.pilot/FlightRecord
    They are all txt files and the file name includes the date.

    Come back and post a link to the report it provides

    When/where did you last calibrate the compass?
     
  6. Mark The Droner

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    Curious - did you hover pre-flight to test the compass as many do?
     
  7. alokbhargava

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    In real words it's a victory of man over machine, patience over nervousness Well done.

    I'm waiting to see the logs.
     
    treerichard and Sagebrush like this.
  8. maxwell smart

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    I tried this ,an my shield wont open. I am looking at youtube to see what I am doing wrong.
     
  9. maxwell smart

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  10. Meta4

    Meta4 Moderator
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    Interesting and mysterious flight record.
    There's no obvious cause showing there.
    You had compass errors show up 3 times for 8, 24 and 12 seconds.
    Each time the Phantom switched to atti mode to deal with the different data it was getting from the compass and GPS.
    This may have accounted for the problem you mentioned in handling things as you had lost the position holding of GPS.
    At the altitudes you were at, I wouldn't expect any ground influence causing the problem and the distance away from the start suggests that it probably wasn't caused by compass calibration problems at the start.
    I note that you also had Yaw Errors twice and wonder if this is a separate issue but it might be related to the compass issue.
    That the errors went away is also interesting.


    When/where was the compass calibrated before the flight?
    Have you modified the Phantom or added the last compass calibration?

    I'd definitely be giving it a good new compass calibration and careful test flight to see how it behaves.
     
  11. maxwell smart

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    I haven't calibrated the compass in a long time, I usually do it once a week. But this time it has been over a month. The map data is not right ether. On the return flight It shows coming back that the phantom was of to the right as you look at the screen. It was way of to the left, not what the flight data shows. Don't know how that can be.
    I was watching the screen on RTH and when I saw the shop down the street I knew it was going the wrong way.
    If this would of happened in daylight I would have lost it. I cant see anything on the screen in daylight.
    I think when it went in to ATTI that the wind got it. It was a little windy.
    At one point it fell about 60 feet and restarted, I think I accidentally put it in CSC or whatever it is called. Because I was trying to back it up come down all at the same time.[ I panicked ]
    I have a lot of antennas hanging off this bird, so that may be part of the problem. But it never did this before ,with the extras on there. Thanks for looking.
     
    #11 maxwell smart, Apr 17, 2016
    Last edited: Apr 17, 2016
  12. Oso

    Oso

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    I agree sir. When I first read the original post, I was sure this would end up being another case of calibrating the compass in a bad spot leading to a wonky flight as soon as the phantom left that spot. Now I'm not so sure.
     
  13. Reed L

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    When you let go of the sticks in atti mode and it went north, that's normal. Great job in landing :) Atti can be really hard especially in wind. It looks like because it was going in and out of atti mode and P-gps, it was messing with you a bit. It would feel like you have control and then it changes into atti so manually flying and then back into P-gps at the end. Looks like a stressful flight. If this is not where you normally fly then I wouldn't go back because there's a lot of obvious interference.
     
  14. maxwell smart

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    I fly here a lot ,it is my house. There is however a lot of interference. Cell towers power lines,TV towers, I can count 10 towers from my driveway. I was very close to one when this happened. I think that may be why.
     
  15. BudWalker

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    Since the .DAT wasn't posted I used @ferraript 's txt converter to extract more info.

    The "compass error" and "yaw error" are both values from a field called nonGPSCause. There's been a lot of discussion about what exactly this field means. It could mean either an error that causes GPS to not be used or an error that is not a GPS error. I favor the latter. Usually, but not always, switching to ATTI from GPS-ATTI, and a nonGPSCause indication occur at around the same time. One doesn't always precede the other.

    I've looked at some flights where these errors were caused by gusty, not just windy, conditions. My theory is that the flight controller sees large errors in predicted versus measured sensor measurements and has to switch to ATTI to let the pilot do the navigation. From the pilot's description it sounds like it was windy, but not gusty?

    I had a flight where this happened. The Go App kept saying "compass error". When I replayed the flight later there wasn't an error indication of any kind. Now, with a new version of the Go App, when I replay the flight the screen turns grey and says GPS error. Go figure. Has the pilot replayed this flight? It wasn't windy or gusty that day. It occurred twice, once over some power lines close to my house. I've flown close to those power lines many times since trying to recreate the problem. I've had to conclude the power lines were not a cause.
     
  16. maxwell smart

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    There was some wind, my have gust some to.
     
  17. BudWalker

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    By gusty I mean variations of 20 MPH or more. That, and coming from different directions.

    Are you using the Go App? If so, did you replay the flight?
     
  18. maxwell smart

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    well I cant find a playback in there.
     
    #18 maxwell smart, Apr 17, 2016
    Last edited: Apr 17, 2016
  19. alokbhargava

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    What are these mods? Have you modified antenna system?

    It appears GPS loops are working but resulting direction correction results are incorrect, thus resulting into a message of non GPS compass error.
     
  20. Jason Lawrence

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    Good thing you had line of site at 3000ft in the dark...Otherwise who knows what would have happened.