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Newbie Question - How Much Drift is normal

Discussion in 'Phantom 2 Discussion' started by Maverick7, Feb 1, 2015.

  1. Maverick7

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    Hi,

    I took my ph2 out for the second time yesterday and correctly callibrated the compasss.
    In GPS mode I flew the phantom at 10 feet and then did nothing to monitor and It slowly drifted down to the ground.
    Wind was approx 15-20 km/h and battery was full.

    Is it normal for the phantom to drift down to the ground if you perform no input?

    Any advice appreciated. Thx.
     
  2. Meta4

    Meta4 Moderator
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    No ... normal is for the Phantom to hold altitude quite closely
     
  3. Hughie

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    Are the gains set to defaults?
    How much battery did you have when this happened ?
     
  4. crash1sttime

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    I think at 10ft you may suffer ground effect ( i think thats the term) so it will sink down, try going up higher and see what happens
     
  5. Meta4

    Meta4 Moderator
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    10 feet should be clear of ground effect and a Phantom should hover there easily
     
  6. rudyr89

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    Your phantom should easily hover at 10 ft. Make sure when calibrating the compass your cell phone and anything else that can interfere isn't in your pockets.
     
  7. Meta4

    Meta4 Moderator
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    Compass issues are completely unrelated to altitude hold issues.
     
  8. Maverick7

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    Any suggestions for me to check?

    Could it be the result of a small crash land incurred on my first flight?
     
  9. Mako79

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    Yes.
    Have you done an IMU calibration since crash?
    Do it when the phantom is cold and do it the moment you plug it in to prevent the "MC too hot warning". It should be done in 2minutes or less and you should get green ticks.
    When the calibration is done when the phantom cold, the calibration is faster and more accurate for the phantom.
    Find a surface levelled to the horizon in both axis. This will minimise/correct wide yaws. And inspect the legs if crashed. A bent leg will affect the IMU calibration.

    The other thing to look at is the gain settings. Shipped settings are different to default settings. The shipped settings are lower and over time the firmwares change and somehow affect the gain settings. Just set to default.
     
  10. Maverick7

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    Thanks all for your responses.

    Can someone please explain the 'ground effect' mentioned earlier in the thread.
     
  11. Clipper707

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    In this context, I believe ground effect is the prop thrust bouncing off the ground and affecting the Phantom's hover characteristics.

    My Phantom 1 (sold) used to sink when I put it in a hover on its first flight of the day. Once it warmed up, it hovered fine. This usually lasted about a half a minute or so.
     
  12. Woody

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    I think it has to do with air pressure and barometric pressure being altered by the props pushing air down at or near ground level. then bouncing back off the ground. Your problem is probably related to barometric sensors that were knocked out of whack during your first flight, not ground effect. Have you tried an advanced calibration yet?

    Sorry to hear about your descent issue. Hope it's just a calibration problem.
     
  13. SteveMann

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    Ground effect occurs when the air below the rotor or wing can't get out of the way and has the effect of reducing rotor or wingtip vorticies, making the rotor or wing more effective. However, ground effect diminishes quite quickly as the aircraft altitude is more than half the rotor diameter or wingspread.

    In your case, the problem is not the ground effect, and also none of the above. The clue is in "Wind was approx 15-20 km/h". Altitude is measured by an atmospheric pressure barometer in the NAZA controller. Zero is set when you acquire the home point. While you were hovering the gusty breeze was telling the phantom that you were going up, so it descended to stay on target. the next time you see this, look at the altitude on the OSD and it should be pretty stable.
     
  14. Maverick7

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    Thanks guys - took the ph2 for a spin today and seems to be resolved.
     
  15. Woody

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    Glad to hear it. I had the same problem with a new Phantom a few months ago. The very first test flight I took it up about 8 feet or so and let it hover to see if it would drift. There was no wind. It didn't drift horizontally but it did slowly descend about a foot every ten seconds untill it reached the ground. Then it bounced up and down like a yoyo. Spoke to one of DJI's service techs and he suggested it was a bad sensor so I returned it to Adorama for a refund.