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Help - Phantom 2 Flips backwards/upside on takeoff.

Discussion in 'Phantom 2 Help' started by thelordsnod, Jul 11, 2014.

  1. thelordsnod

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    So, after my unfortunate crash into a tree and consequently into the fresh water below, I have managed to bring my Phantom 2 back online with everything functioning (gopro, gimbal, motors, gps etc, everything appears to function as normal).

    But every time I try to take off, it immediately flips backwards and lands upside down, it doesn't even manage to get 1ft off the ground before it does this.

    Things I have checked and tried: 1. Re-calibrated compass 2. Checked all propellers are spinning in right direction, and correct props are installed on the motors they should be 3. Replaced all props with new props 4. Checked all cable connections to be sure they are connected properly and in the right position 5. Ensured that everything is clean 6. Checked and re-checked motors and they seem to be spinning equally and in the right directions

    I have done the basic IMU calibration, but when I try the advanced IMU calibration it says that the MC is too hot and I need to shut it down for 5 minutes and try again. But no matter how long it's been shut off, it will always give me this message.

    I checked the compass mod settings and they are all within the proper ranges.

    The one setting that concerns me is the Z value under "Compass(Raw)", which is at around 217 to 220 at all times. When I tilt the phantom backwards at about a 75 degree angle the Z value will reach zero (further tilting it backwards will continue to decrease the Z value into the negative.)

    Is the Z value for the compass(Raw) data supposed to be at or around zero when the phantom is level?

    I've searched every where to find out what could be the cause of the instant flipping on takeoff, and so far nothing has worked. My conclusion is that my compass magnet is damaged or the Naza is damaged, but I want to try out all possible fixes before buying replacements to test. The other possible issue is that it might be problems with the rear motors/ESC's, the rear motors were the ones that came into contact with the tree, but somehow I doubt they are the problem as they all spin up perfectly fine and accelerate just fine, to me it really seems like the Phantom thinks it is tilted due to problems with the compass and is trying to level itself out.

    Thanks for your help!
     
  2. thelordsnod

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    Another thing to note: The location where I landed was very soft mud/silt at the bottom of the lake (it was in 2ft of water where I found it). So the magnet for the compass was definitely submerged in the soft mud, and I did not realize that it still had some minor dried dirt on it after taking it home, and only managed to clean the dried dirt off after over a week of the phantom sitting in its box covered with rice.

    Just took the magnet off the landing gear now, and its still slightly dirty, so I'm wondering if this might be an issue. I have 99% isopropyl rubbing alcohol and distilled water which I can use to clean the dirt off, but I'm curious if the magnet will not like being rinsed with the isopropyl alcohol (I know the tiny circuit board will not be an issue with it).
     
  3. thelordsnod

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    I think I just figured out what was wrong. I never adjusted the Naza position, but I did unplug all the cables that lead into it. When I got home after the water crash, I took off the top cover of the phantom, and began unplugging the cables to the Naza. I realized after I pulled out the motor cable (M1 or whatever) that I should take photos for later reference so I can plug it all back in after 10 days of drying.

    I reinserted the cable to the Naza so I could take the photo, but I apparently put it in upside down for the photo, thus my reference photo was reversed completely, so when I matched my reference photos yesterday, I was matching it completely wrong.

    Basically I was testing out the motor reaction without propellers on the motors, and when I tiled the Phantom backwards, the forward propellors would start spinning faster, and vise versa when I would tilt the Phantom forwards the back props would spin faster, which is pretty counter intuitive considering you want your forward propellers to spin faster if the quad tilts forward, thus stabilizing the quad by countering the forward angle with the forward props.

    I found some images online of the interior setup for the Phantom 2, and sure enough, the colors for the motor cable where they plug into the Naza were reversed in comparison to mine.

    Flipped that cable over and plugged it back in, put the cover back on and screwed it down, and tested it without the propellers again.

    Now when I tilt the phantom backwards, the back propellers spin faster to compensate, same thing for when I tilt it forwards. Going to test fly it in the morning, but I'm 99% certain this was my problem!

    Noob mistake, but making mistakes is all part of the learning process. As Homer Simpon says... "Trying is the first step towards failure, so the lesson is, never try." Wait a sec...

    TLDR; User error when plugging in the motor cable to the Naza controller, it was flipped the wrong way and thus reversed all motors, causing the quad to flip immediately upon attempted takeoff.
     
  4. DKDarkness

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    Is this the behaviour you are experiencing: http://youtu.be/iZkb1475Scg (and how the frog do I use these [youtube]iZkb1475Scg[/youtube] tags?!?)
     
  5. OI Photography

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    [youtube]http://www.youtube.com/watch?v=iZkb1475Scg[/youtube]

    Use the full link like that and wrap it in the tags
     
  6. DKDarkness

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    I'm guessing it just doesn't work from an iPad :)
     
  7. OI Photography

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    Ahh quite possibly, never tried it from any mobile device. I've seen it act odd for some though, and that might have been the cause.