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Aircraft in GPS mode is "twitchy"

Discussion in 'Phantom 2 Vision + Discussion' started by Mlaudisa, Jul 14, 2014.

  1. Mlaudisa

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    Hi, I just wanted to bounce something I have noticed with my 2nd PV2+ (the first was a wonderful flyer that I hopelessly crashed...). When flying in GPS mode, I have noticed that the aircraft visibly twitches while hovering in the same spot. I thought it may be related to wind, and I'll be testing it with no wind to see if that's the problem, but my first Phantom wasn't doing that. When I switch to ATTI mode, the "twitching" stops and the aircraft floats nice and stable (ex. of course if floats with the wind, which is normal in that mode).

    Note that I have done advanced cali at home, have recalibrated on-board compass just prior to the flight, I'm in an open field with no interference, and show 10 satellites locked in. Just wondering if anyone else has notice the same issue, this may be connected to TBE and the dreaded Magnetic Declination issue, yet I wasn't getting the aircraft circling around as it would in TBE.

    Thanks for any insights!
     
  2. Phantom Phixer

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    Hi, i test fly repaired P2 drones pretty much all day and have come across this problem multiple times. The problem isn't TBE, but rather a GPS malfunction (at least in my cases). it can be easily corrected with a new GPS which is somewhat expensive (around 165.00) but simple to install. if you don't like working on the internal components you can always send it in to a local R/C shop or something of the like. hope this helps! :)
     
  3. Mlaudisa

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    Thank you Phixer, it makes complete sense and I really appreciate your help. I will transplant the GPS from my old machine and see if it fixes it, thank you!
     
  4. Phantom Phixer

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    Not a problem :)
     
  5. Phantom Phixer

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    did it work by the way :?:
     
  6. kymedic121

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    Just sent one back today that was not even a week old. Using the 3.04 assistant I calibrated remote, then phantom. Took her out to fly and did the compass calibration. On the first rotation I got the green light and the second nose down calibration on axis it would turn yellow for a few seconds than slow flash green. Had 8 satellites. Lifted of the ground maybe 5' and she would drift horribly left and right with no input. I performed another calibration and even did the advanced IMU calibration. My levels are between 1400-1600. Same thing every time, with the constant drift even though the flight control lights flash slow green which indicate GPS lock. I was able to land ok with the test flight. I just don't get how a brand new unit could act like this, what could be the cause? I know one thing I don't want that one back as I have no confidence it this unit. After barely having in 7 days and it does this no thank you. New unit or my money back and I will buy elsewhere.
     
  7. Mlaudisa

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    Haven't had the time yet, will try this weekend hopefully
     
  8. Phantom Phixer

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    1400-1600 are perfect compass mods so that rules out a bad compass. the LED flashing slow green does mean GPS is activated too. the only possible thing i can think of is gains/ atti. gains were changed but that would mean the craft tilts somewhat horizontally. i wish i could provide some better assistance but troubleshooting something over the computer and in person makes a world of difference. hope i helped a little! :)
     
  9. Mlaudisa

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    Let us know how you make out with your new one... nothing more irritating than this kind of unexplained hit and miss... I'm putting my hopes in the new 3.05 firmware to correct the compass declination issues, hopefully that will help cure these kinds of symptoms
     
  10. Phantom Phixer

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    one can only hope! :lol:
     
  11. kymedic121

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    Thanks so much, your input is very appreciated. I checked the gains and they were all still at factory settings and I was still running in Phantom Mode as I had not changed to Nazam yet as I wanted to see how it handled with it being a new aircraft. I sent it back to Dronefly and hopefully they will make it right being that I only had it one week.
     
  12. happydays

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    Sorry to hear this. I (and I am sure many others) have been following your diligent process of studying and preparing for your Phantom experience. You really have been a model of preparation.

    I, luckily, have had 2/3 good phantoms. No 1 wouldn't allow me to do a compass calibration, but like an excitable teenager, I flew it anyway about ten times before it ended up in the sea. The other two have behaved impeccably and allowed me to capture some impressive footage.

    I hope your replacement works as well as you hope it will. Keep in touch.

    CBS
     
  13. fastsmiles

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    A malfunctioning GPS would explain the twitchyness I have been having as well. It was solid from day one until just a few days ago and now it has trouble keeping itself within a ten-twelve foot area. I have only had it 7 weeks.
     
  14. Mlaudisa

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    Mission accomplished! This morning I decided to follow Phixer's suggestion and transplant the GPS unit from the old crashed Phantom to the new "twitchy" one. Unfortunately, the old GPS seemed to have a cracked aluminum surface for what I believe is the receiver antenna, whereas the new GPS unit was flawless. So I decided to replace the Naza module instead, reasoning that it may be the culprit.

    It's a relatively simple job, as long as you pay close attention to the wiring. I took a few photos of it with my iPhone just in case I got in trouble on re-assembly. After replacement and closing the shell, I upgraded the firmware to 3.04 performed advanced Cali, etc. In the field the aircraft performed very well: in GPS mode it no longer exhibited the TBE behavior and hovered steadily with no signs of drift. Switching to ATTI and back to GPS felt predictable and uneventful. Bottom line, it seems to fly as the earlier unit now, which would make sense since I basically replaced the entire brain of the unit.