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Which is the most likely cause of my sudden near fly-aways?

Discussion in 'General Discussion' started by Jozii, Feb 2, 2015.

  1. Jozii

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    So since December I've been having this issue that my Vision+ loses GPS signal when up in the air - no obstacles in sight - and it starts drifting away, sometimes very fast. When I got the quadcopter in October I was skeptical about its reliability, but my trust quickly grew and before I knew it I was flying at great distances or with Ground Station without any fear at all. I knew it would always return. Now, I'm scared every time and more often than not something bad does happen.

    What could be the reason for these sudden GPS signal issues? I have a few theories. What are your thoughts, and which one do you think is most likely?

    1) I don't always do the GPS calibration. I *always* have a good GPS signal before take-off (at least 6 satellites). But I read somewhere that you don't need to do the thing where you hold the quadcopter out and spin it as described in the manual before every time you fly, so I don't. As long as it gets the slow green blinking light before starting. RIght?

    2) Bad weather. When I flew in October and November it was still sunny. In December and January, almost all my flights have been on very cloudy (though not too windy) days. Can clouds affect the signal? Since there are usually no obstacles remotely near the quadcopter when it's up there, I can't think of anything else that would block the signal. The weather theory is not always true - I once lost signal on a Ground Station flight on a fairly clear day. It wasn't, however, a perfectly clear day so the weather could still be relevant.

    3) Damaged wires. I've crashed into a tree, and it was about the same time that the GPS issue started. On a visual inspection I can't find anything wrong, though, and I always have a good signal (at least 6 satellites) prior to take-off. Could something still be glitchy?

    4) Bad flight locations. I've used hand-held GPS devices a lot and know that some places on earth - no matter how clear the surroundings are - simply aren't good. Satellite reception is always bad in those areas. This is my least likely theory, though, as on several occasions I've experienced these GPS signal failures when flying on locations where in October and November I had no issues at all.

    So what do you think?
     
  2. msinger

    Approved Vendor

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    Re: Which is the most likely cause of my sudden near fly-awa

    To answer your questions:

    - There is no such thing has a GPS calibration. What you're describing is the compass calibration. And, you only need to do that when flying in new locations.

    - I don't think clouds have much affect on GPS -- if any at all.

    - It could have something to do with your location -- or the time of day you fly. Satellites are always moving.

    Do you have a Vision+ version 3? If not, try these things:

    Copper Satellite Shield Mod: viewtopic.php?f=27&t=31054
    Tighten GPS Plug: viewtopic.php?f=27&t=33453
     
  3. 4wd

    4wd

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    Re: Which is the most likely cause of my sudden near fly-awa

    Probably a slightly lose connector plug from the GPS antenna.
    If it drops below 6 satellites you have essentially ATTI mode and the wind will take it and any corrections can soon make things wildly worse if not careful.
    It also will not know where the homepoint is.

    You really aren't up to speed if you think you are calibrating the "GPS" like that (1)
     
  4. Andrey320

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    Re: Which is the most likely cause of my sudden near fly-awa

    I vote for 3
     
  5. Narrator

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    Re: Which is the most likely cause of my sudden near fly-awa

    I'll be kinder by suggesting you probably meant compass but had GPS in your brain.

    Option 1 is out if it happens often, unless you're at a new location each time it happens?

    Option 2 is not a consideration. The only thing that blocks GPS signal is dense trees or obstacles - not weather.

    Option 3 is the most likely of all scenarios, not just the 4 you've picked. By visual inspection, do you mean you opened it up?

    Option 4 is possible if your flight locations include electromagnetic interference, including near concrete foundations (with metal mesh).
    What are the characteristics of the locations you fly?

    To my mind, the consistency and timing suggests some sort of damage from your crash.
    Drift isn't what I would call a fly-away. With drift, you still have control, as long as you can still see it well enough to navigate.
    And yes, without 7+ satellites, you're flying in Atti mode, which means it will drift with the breeze.

    Where are you located? You might want DJI to fix it. Or you can risk your warranty by opening it and trying yourself.
     
  6. Meta4

    Meta4 Moderator
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    Re: Which is the most likely cause of my sudden near fly-awa

    5) Loss of 6+ sats causes your Phantom to drift with the breeze in atti mode.
    Losing satellites and drifting is not a near flyaway.

    A number of things said indicate your understanding of things GPS is sketchy.
    1 & 2 have been addressed already.
    Your point 4 isn't valid. The G in GPS stands for global.
    The only way a location will have sub-standard sat coverage is if a good chunk of the sky is obscured by trees, buildings or terrain.

    You haven't mentioned how good your satellite lock is or whether your Phantom has the foil mod.
    Satellite reception is critical for most Phantom operations and if your Phantom isn't picking up the full complement of sats you run the risk of losing your Phantom because it cannot RTH without proper sat lock.
    DJI made the Phantom with a critical flaw that causes poor sat reception and only addressed this recently.
    If your Phantom has the foil mod - it's not working.
    If not, it needs it. - check msinger's excellent post viewtopic.php?f=27&t=31054
     
  7. flyNfrank

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