ATTI mode mid flight - causing the Mavic to almost crash

Discussion in 'Mavic Pro Discussions' started by mattmjm, Nov 22, 2016.

  1. mattmjm

    mattmjm Active Member

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    I had my first scare, my first near crash, and my first learning lesson tonight.

    Setup: I set everything up as per normal routine. However, after the craft and RC were powered and ready to go, I did not get a Compass Error - which I usually do. So, I did not calibrate the compass on this flight. I thought the compass calibration was similar to the RC calibration and the IMU calibrations - if the app doesn't say to do it, then it's best not to do it.

    Flight: I got the Ready to Go and lifted off. I hovered a few feet off the ground. After moving approximately 30 feet away and ascending 20 feet or so, the drone started to slowly rotate left on it's own (as if I was using the left stick to turn it to the left). It was gradual at first, but when I tried to input a slight correction, it got worse and faster. At this very point is when I realized something was wrong.

    When I tried a larger correction, the drone began to bob and sway around randomly as if hanging by a bungee cord. There was little to no control. Not good. At this point, the app announced an audible "ATTI mode". Aw crap. My senses kicked in. I quickly looked down and saw the "No Positioning" message across the top in yellow.

    I thought back to an earlier post from today or yesterday about using the Pause button. Pressed it. Nothing. Pressed it again. Nothing. Pressed and held, nothing. What is this thing supposed to do? All while I'm trying to maintain control as it's bobbing, weaving and rotating on axis randomly.

    At this point, the craft has rotated a few times and is pointed in a different random direction that I was not in tune with. I realized my inputs are reversed and its facing me. I have experience controlling crafts with reversed inputs, but those first few seconds are critical to diagnose and correct with the reversed sticks. I had a difficult time controlling it and it flew around wildly. Luckily, it did not crash into anything or anyone.

    A moment later (which felt like an eternity), I was able to regain control when the GPS positioning lock came back on. I landed haphazardly immediately after (and likely largely while the GPS was still "locking on").

    Result: She's safe and sound, but not without giving me a scare.

    Learning lesson: Now, I am realizing I should have done the compass calibration and should probably continue to calibrate the compass before every single flight from now on.

    TLDR;
    Didn't calibrate compass, took off, aircraft went into ATTI mode, went wild, barely managed to land safely and in one piece. Calibrate the compass before every single flight.

    What else can I learn from this experience? Lay it on me.
     
    #1 mattmjm, Nov 22, 2016
    Last edited: Nov 22, 2016
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  2. msinger

    msinger Well-Known Member
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    That's not a good idea. Perhaps that's what got you into this mess in the first place. It would be best to follow these guidelines instead.
     
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  3. mattmjm

    mattmjm Active Member

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    I'm confused now.

    1.) 9 out of 10 times, I get a compass error and I am forced to calibrate it before flight.

    2.) The guidelines sort of go back and forth on whether you need to calibrate it and how often:
    When Should I Calibrate?

    You do not need to calibrate before every flight and in some cases you definitely should not calibrate. That doesn't mean you shouldn't ever bother doing it. It only takes one time for it to go very wrong. The most important aspect of compass calibration is making sure the magnetic "neighborhood" around your Mavic is consistent between calibration and during flight.


    3.) In the guidelines, the first paragraph reads: "Inclination and deviation that isn't corrected through compass calibration will cause inconsistencies between GPS and compass that can result in "toilet bowl effect", a swirling motion that can cause the Mavic to fly out of control." - I believe this is sort of what I was experiencing.

    4.) What else could cause the automatic turning of the AC and the ATTI mode?
     
  4. msinger

    msinger Well-Known Member
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    What is the exact error message you see in DJI GO?

    Poor or no GPS connection
     
  5. mattmjm

    mattmjm Active Member

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    Red background, scrolling across the top: "Compass error, move the aircraft and calibrate the compass". Tapping on that takes you to the Aircraft Status screen where the "Calibrate" button for the Compass will have a yellow exclamation point alert next to it.

    Had 15 or so satellites connected during take off. Could all 15 disconnect 30 feet away and so quickly?
     
  6. msinger

    msinger Well-Known Member
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    Did you see this compass error the first time you flew your Mavic? Have you ever crashed your Mavic?

    Your Mavic is connecting to satellites in the sky. 15 satellites is plenty, so the ATTI switch is most likely being caused by your compass issue.
     
  7. mattmjm

    mattmjm Active Member

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    Yes. The first time I powered it up was indoors and it gave the error message immediately.

    No. Never.
     
  8. msinger

    msinger Well-Known Member
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    Did you still see the message when you moved outdoors?
     
  9. mattmjm

    mattmjm Active Member

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    Depends. Sometimes it does it, sometimes it doesn't. I haven't figured out a pattern yet. All the while, I sometimes have to wait extended periods for IMU calibration {proper term?} to complete.
     
  10. msinger

    msinger Well-Known Member
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    When you're outdoors, what type of surface is your Mavic sitting on when you normally see this compass error? Are there any magnetic metal objects in the area?
     
  11. mattmjm

    mattmjm Active Member

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    Concrete typically. But other times, just a gravel driveway or road.

    Yes, and I typically have to move far away from them for compass calibration to complete successfully. I've noticed even a small drain pipe cover in the ground can affect the results of the calibration. I also make sure to remove my phone and keys from my pockets.
     
  12. msinger

    msinger Well-Known Member
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    Most concrete is chock-full of metal. That definitely could cause compass errors to display in DJI GO. Try starting your Mavic up in a grassy area.
     
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  13. mattmjm

    mattmjm Active Member

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    I'll have to give that a try and report back.

    Will calibrating the compass over a grassy surface lock in the calibration for good or will I need to calibrate it again often (even if an error doesn't exist - which it didn't before tonight's flight).

    What about taking off from concrete?
     
  14. msinger

    msinger Well-Known Member
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    I'm suggesting you power on your Mavic from a grassy area to rule out any possible interference from magnetic metal objects.

    This is not a good idea. The compass should not be near any type of magnetic metal objects when flying your Mavic.
     
  15. mattmjm

    mattmjm Active Member

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    Got it. Good plan. I will do this tomorrow and report back.

    So, no concrete take offs? Ever?
     
  16. msinger

    msinger Well-Known Member
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    Never.
     
  17. mattmjm

    mattmjm Active Member

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    :( This is news to me. So, other than the obvious mishap tonight, I am lucky to have not had any other mishaps after taking off from concrete?
     
  18. msinger

    msinger Well-Known Member
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    Now you know for next time ;)
     
  19. MavicProMX

    MavicProMX Member

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    Thats too bad, i have no grass only concrete every where and pavement. :(


    Sent from my iPhone using MavicPilots
     
  20. msinger

    msinger Well-Known Member
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    The pavement most likely has no metal in it.
     
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