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Brief compass failure after take off

Discussion in 'Inspire 1 Discussion' started by online421, Feb 8, 2016.

  1. online421

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    I am a noob to the RC world, I do my Pre-flight check religiously as per DJI instruction, Inspire is my first RC unit.

    I have a question/problem:
    I am getting compass failure mid air for 3-5 seconds approximately 10-15 seconds after airborne.


    First time this happened was a few days ago while we were on Honeymoon in Bora Bora, it was my 4th-5th Flight, I calibrated my compass as per system requirement, made sure I had more than 9 satellites, and took off from the deck of my above water pontoon.

    About 10-15 seconds after I took off I got this compass failure message on my screen, I look up, the Inspire is slowly spiralling in the sky (altitude between 4m-8m), it seems I have lost control of the horizontal movement of the copter, I look at my screen to see if there is anything I can do, meanwhile my wife is screaming at the background about the copter is going to hit the water that’s when I raised my head and realised the copter is only 2m above the sea, I tried to stay calm and elevated the copter slowly, a disaster was averted… the loss of compass was only about 5 seconds but it made me shxt bricks.


    I launched my copter again yesterday at home, still got this compass failure very briefly for 3 seconds shortly after I took off, again I moved the copter up to avoid hitting a tree.

    I only have this compass failure within 10-15 seconds after I took off, its a very short period of time, and never again during flight.

    Has this happened to you? Have I done something wrong in the pre flight?
     
  2. ianwood

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  3. The Editor

    The Editor Moderator
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    Firstly you do not need to calibrate the compass before every flight. In fact it's not good practice to do so.
    My reasoning behind this is well documented over the forum.
    The more you calibrate, the more you run the risk of introducing an error. It is far better to rely on checking your mod values prior to each take off.
    Having said that, what firmware are you running?
    Earlier versions of the FW suffered an intermittent compass error and this was later corrected via updated firmware.
    If you are running up to date FW then its strange you are experiencing persistent compass errors and I would investigate further.
    What are your compass mod values at rest?
    Go App/MC Settings/Sensors - bottom values 'compass' what is the mod value? (It will fluctuate slightly)
     
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  4. online421

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    Thanks Editor, I will need to check all of these once I get home tonight.

    I have a feeling it maybe the firmware. I know for certain the firmware is not the latest.

    Cheers
     
  5. Meta4

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    This is totally unrelated to firmware. It is 100% compass.

    The problem is not that you are getting a compass failure at all.
    Your compass is working fine but what you are doing to it is the problem.
    What you are calling a compass failure, DJI calls Compass Error but this is misleading.
    It's not that the compass is malfunctioning at all.
    The compass is identifying a significant difference between the magnetic field where it is and where it was calibrated.
    If you calibrate where the earth's normal magnetic field is distorted by cars, structural steel. buried pipes or reinforced concrete (most common), and then fly away from the magnetic influence, and ....Bingo!!.
    The compass tells you something is wrong and confirms this by flying a curve instead of a straight line or it will slowly corkscrew.

    It's possible to "successfully" calibrate in a distorted magnetic field and have compass data that appears correct - as long as your compass is within the distorted magnetic field.
    So checking the compass mod value is not proof against a bad calibration.

    Do your compass calibration in a magnetically clean area well away from cars, structural steel. buried pipes or reinforced concrete etc.
    Get a good calibration and stick with it.
     
    #5 Meta4, Feb 9, 2016
    Last edited: Feb 9, 2016
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  6. The Editor

    The Editor Moderator
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    Yup - having re-read OP's original post I would concur. It sounds as though he is expericing TBE after take off due to a skewed compass calibration on deck.
    Apologies to online421, although there were two updates in firmware to correct and lower the threshold that the aircraft switches to P-Atti in erroneous compass data situations you're sounds more like poor compass calibration.
    Have a search on the forum - there is plenty of advice about doing a compass calibration and leaving it (you do not need to do one each time)
    Thanks Meta for the correction. Too many posts and I shouldn't speed read. :)
     
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  7. online421

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    Thanks for the input, Meta4.

    come to think of it, I did have to re-calibrate several times on the deck, and still getting error message asking me to calibrate the compass at a place where there is no magnetic fields.

    and when I flew it at home I calibrated it next to two cars - within radius of 2m.
     
  8. online421

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    I will certainly do this as well.
    However the firmware my inspire came with is older than 1.3. I've updated it last night.