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Phantom 2 (non vision) Altitude Drop

Discussion in 'Phantom 2 Help' started by Xrover, May 8, 2015.

  1. Xrover

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    On my P2 with Zen H3-3D running FW 3.14 SW 3.08, I am finding that at an Altitude of 8 feet or less the copter does not want to maintain Altitude. In GPS Mode and hovering at an Altitude of around 8 feet, it starts descending and doesn't try to maintain Altitude. I can apply some throttle and it will rise but as soon as I release the stick, it starts dropping slowly.

    Is this common for the P2?
     
  2. IflyinWY

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    My FC40 never used to do that, but now it does something similar. I'm thinking my GPS shielding is the cause.
     
  3. SteveMann

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    GPS has nothing to do with the altitude. The altitude is measured by a barometric pressure sensor, so if the wind is gusty it can change the altitude during a hover. You may also want to adjust your altitude gain in the assistant program.
     
  4. Xrover

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    I tried bumping up the Altitude Gains.First I bumped it 10% then 20% and it didn't help.
     
  5. IflyinWY

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    I fly sometimes in 15 to 25 mph winds which are typically gusty.

    Was there a gusty wind when your bird descended from 8 feet?

    Maybe a high pressure area was moving in really fast and it fooled the bird. <--That's a joke:p
     
  6. Xrover

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    No Wind. It does it every time with or without wind. It has been doing this with past FW's also. Where is the Barometer located? I'm guessing inside the FC.
     
  7. IflyinWY

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    It's in the NAZA and I don't think it's a barometer in the typical sense of the word. Personally I think steve is wrong. Can you picture an altimeter in the phantom which is capable of measuring altitude to the inch? Now 10 or 12 satellites, that sounds a bit more feasible to me. I've been wrong quite a bit lately, so keep that in mind.
     
  8. TeamYankee

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    GPS altitude is pretty inaccurate to be honest... It's typically 1.5 times the horizontal accuracy. So at best accurate to 3 or 4 meters... which is fine if it's in a plane at 30,000 feet, but no good close to the ground. Hence the altitude barometer inside the NAZA. The Flytrex also has one, inside a little metal can with a pin hole in it.

    upload_2015-5-8_9-39-20.png

    Like any barometer, it needs a baseline to zero itself and it does this at power up so it knows where the ground pressure is... as you ascend the pressure drops in a linear fashion so it can work out the height, it also takes into account the temperature...

    I used a similar system when launching balloons for the met office down in the Falklands.. way back in another life!
     
    #8 TeamYankee, May 8, 2015
    Last edited: May 8, 2015
  9. jason

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    When testing my P2 in the backyard the altitude will drift up and down about 2 feet due to winds moving around the buildings from different directions. Out in an open field that isn't a problem.