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First close call with Phantom 3 Pro

Discussion in 'Pro/Adv Discussion' started by phantomized, Jul 8, 2015.

  1. phantomized

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    I always calibrate my compass but today almost found out first hand what could happen. Taking off from the same spot as last time and didn't calibrate. Auto-takeoff and within seconds I sense something is wrong. My indicators have satellites I got the safe to fly go-ahead, but no good. Phantom is drifting in air and my weak manual skills had to be used to land her. Find a patch of grass close to a metal fence, land right beside the fence with the winds blowing me around, safely landed but my propellers sliced the fence and broke. She didn't even tip over just propeller damage. Replaced and calibrated. Next flight was as smooth as always.

    Just a heads up, always calibrate your goods.

    NOTE: It has been brought to my attention by others on this forum that this has nothing to do with compass calibration, it was in fact a loss of GPS signal.
     
    #1 phantomized, Jul 8, 2015
    Last edited: Jul 9, 2015
    Mike Mauk likes this.
  2. Meta4

    Meta4 Moderator
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    Sorry but there's not enough detail here to know what the problem was.
    It wasn't related to you not calibrating the compass though and calibrating before every flight is like using a good luck charm.
     
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  3. phantomized

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    What kind of detail is needed.? It felt as if she could not hover and going with the wind. I had to manually control the altitude and speed to land her properly. Although my manual skills are not the greatest and I had some obstacles, I recovered and only lost 2 propellers against a fence. If there is a way for me to post flight data (i wasn't recording video), please be a champ and guide me how to do it and you can analyze if you desire.
     
  4. louforgiveno

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    DJI recommends it.
    As a pre-response to what will come...
    62231693.jpg

    The P2 is a different beast from the P3
     
  5. Meta4

    Meta4 Moderator
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    First, it's fine to get a good compass calibration and stick with that if you are within 100 miles of home..
    Doing it every flight introduces the potential for getting a bad calibration and that would cause problems.

    Second, flying or landing close to obstacles like that fence is the biggest danger to Phantoms.

    You said .. I got the safe to fly go-ahead, but no good. Phantom is drifting in air.
    Can you explain what this means? How much/what direction was it drifting?
    Any other details?
     
  6. acherman

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    I think the last compass calibration I did was 2 weeks and 15 flights ago. I haven't flown in that same spot again, but as far as ~100 km away and as close as 1km. No problems at all.
     
  7. Flyboy

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    I calibrate after Firmware upgrades. NEVER before every flight. I don't travel with it so I am always in the area.
     
  8. phantomized

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    Sure. In the app I got the green "safe to fly", I was locked in to 11 satellites and I auto took-off. Once in the air she wasn't hovering as I'm use to. She would drift in the direction of the wind, it was about 10km/h southbound. I landed in a safe spot as possible and replaced the propellers on the spot. Loaded her up and did a compass calibration. Auto took off again and the bird was stable as always. I think it was the compass, but if you have other ideas or more info as to what may have happened I am all ears.
     
  9. Meta4

    Meta4 Moderator
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    There's still no information beyond She would drift in the direction of the wind.
    And without details no-one can make any useful interpretation of what the cause may have been.
    How far did it drift?
    How long was it drifting for?
    How did it respond to your control?

    If you had a temporary loss of GPS, the compass would have no influence on drifting.
    The compass does nothing for position holding but affects the ability to fly straight.
     
  10. Khador

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    Replay the flight in the app, if you have the iphone version it will show the stick inputs.

    I've seen from teaching my daughter to fly my P3 and sometimes its easy to have slight /subtle stick inputs and not realise you are doing it because you are focused on something else... She for example has a habit of leaning on the right stick because she is a 'leftie' and is using her right hand to bear the weight of the controller while tapping on buttons etc. in the app, her thumb rests on the stick and i have to remind her whats happening.

    Just an idea anyhow... reply the flight in the app see if there were any inputs recorded.


    As regards the 'weak skills' comments...everyone learns at least once. I've never met a natural flier in all my years. To help maintain control of the bird during take off and landing I personally find its easier to take off and land with the bird facing away from me so that left on the stick moves the craft left, right goes right etc, and i always land like this... there's nothing worse than panicking to screw up your spatial awareness / orientational awareness.

    EDIT: Just though on that depends on what mode you are using the controller in but you get the idea hopefully.

    Just an idea anyhow. Hope it helps.

    Fly safe
     
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  11. nhoover

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    I have flown P2s and P3s over 300 times without calibrating the compasses. I think it's a non-related coincidence in this case. I only calibrate when traveling more than about 50 miles away or upgrading firmware.
     
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  12. phantomized

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    I think we know what it is now. It was gps. Strange but it is what it is.
     

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  13. Mako79

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    P-ATTI - explains the drift.
     
  14. Mako79

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    +1
    What I luurve about the P3 is that all the information is at the touch of your fingertips. You can check the compass mod values (Settings > Sensors) whilst the phantom IMU is warming up. If the values are 1400-1800, I take off. If they are out of whack, then I find another place or take off from a cardboard box (rebar in the ground). If it continues to be whacked, I then google the closest open field/park and redo the compass dance.

    With the P2, you had to lug around a laptop with a 2 meter cable to check compass mod values.
     
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  15. ianwood

    ianwood Taco Wrangler
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    Posts about compass calibration always bring out the extreme perspectives:
    • The fanatics: "I always calibrate! Every flight!"
    • The deniers: "I haven't calibrated since 1987!"
    Neither of these are the right approach. To not calibrate at all is bad. To calibrate too often is potentially worse. The answer is, you calibrate under specific circumstances. There is an established criteria for calibration. And if you understand how calibration works and why it is done in the first place, you'll see that it makes perfect sense.

    Do yourself a favor and read this link: http://www.phantompilots.com/threads/compass-calibration-a-complete-primer.32829/

    Finally, some people say you don't need to calibrate the compass unless the Phantom gives you a compass error. This is also bad advice.
     
  16. phantomized

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    Great info by you guys.
     
  17. snerd

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    I fly at the same 3 spots here so far, all within 4-5 miles of each other. There is no need to recalibrate the compass for me, unless I get an error from the app. I went to Arkansas a couple weeks ago................. 535 miles. I calibrated the compass before first flight. Use common sense and you'll be fine.
     
  18. snowghost

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    Amen.
     
  19. Meta4

    Meta4 Moderator
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    SO it looks like your Phantom lost GPS signal, but the reason for that isn't clear.
    It may have been because part of the sky was obscured by trees/buildings etc? or maybe an unexplained temporary glitch that may have cleared itself after a few seconds (or not?).
    When the Phantom loses GPS, it switches to atti mode and everything is the same, except you don't have position holding and so the drone can drift with the breeze.
    You still have full control and with a little practice this is no big deal.

    If the problem was that your sky was obscured, GPS position holding will come back as soon as you get a good view of the sky again.
     
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  20. zobiwu

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    most of the recalibration stuff generally is the generic "reboot your pc" and busy work stuff people throw around because nobody's 100% sure if its useful or not.
    in reality most of the time you do not need to recalibrate. in fact, the phantom will detect if you need it rather reliably.

    even with poor calibration it'll still fly / wont just flip.

    the only thing that could be really bad is an improper calibration.. which .. i sort of bet is 50% of the crashes/fly aways due to people recalibrating every 5min without understanding how it even works.