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P3 Unexpected Loss of Control upon landing

Discussion in 'Pro/Adv Discussion' started by Serpent, May 17, 2015.

  1. Serpent

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    After completing an approx. 10-15 minute flight, upon landing my P3P started behaving erratically:

    - Note: Visual Positioning System turned off (some flights ago).
    - Flew for around 10-15 minutes around a farm area in comfortable flying conditions. Flight was normal. Battery around 40% with 3 charges.
    - Touched down for landing.
    - I was lowering left stick for stopping the motors. (You can see it start to slow down in the video)
    - P3 suddenly shot up in the air on it's own at high speed. I brought the stick back to upward / middle position then tried to counter it with downward movement.
    - P3 then started to descend rapidly (far faster than usual). I countered with upward movement.
    - This 'yo-yo' effect carried on for a few seconds.
    - Eventually it was like an added descent force against the stick. I was pushing up against it but it was coming down.
    - Once down it would not stop with downward stick motion.
    - Finally I got it to stop by cornering both sticks in lower middle position.

    Has anyone else had this happen to them?

    I've never seen this happen before on P2V or P3.

    I flew later in different places with out any re-calibration / change to the VPS and everything acted normal. One of those was a short flight on the same battery without recharging.
     
    #1 Serpent, May 17, 2015
    Last edited: May 17, 2015
  2. DrewFlies

    DrewFlies Guest

    First, it kinda looks like you descended to fast

    Second, theres an air cushion once you get 1 foot above ground from the propellers pushing the air down and bouncing off the ground back up at the quad..

    Mine does the same thing. Once I get 1 foot above ground I just push the left stick all the way down and hold til shuts off.
     
  3. gaspimp

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    While both of those things may be true, it can't possibly explain the P3 shooting up again that fast without stick input?
     
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  4. envisionabove

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    Mine have been fine about 26 total, That tree looks a bit close for comfort. I just watched nxiguy do his RTH demo and it was 9 feet off the mark.
    Maybe the moisture in the tree messed with the compass settings? Pine trees hold a lot of water? Like you said after moving to a new location no problems.
    I would test by the tree again maybe?

    Looking at the large pile of galvanized roofing a large pine tree to close for comfort your choose for a perfect spot to land and take off? you can see one sheet lifted up from the down blast and sent the air right back at the drone.
     
    #4 envisionabove, May 17, 2015
    Last edited: May 17, 2015
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  5. DrewFlies

    DrewFlies Guest

    Also you should never land in dirt. The wind kicks the dirt up. You could possibly have a lot of dirt in your motors now.
     
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  6. Buzz313th

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    Scary..
    Looks like a feedback loop where sensors weren't jiving and the P3 was confused how high it was.
     
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  7. DrewFlies

    DrewFlies Guest

    Also just for advice. When landing I too point the camera down. But after Im about 6 feet from ground I roll the camera up. You can severly damage your lens if you havent already. Damaged lens = new camera.
     
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  8. UAVScrappy

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    I'm brand new at flying Phantom's I flew Blade FPV before this. Been on here watching and reading and learning before my P3 arrives. I can say for sure that I will be flying with prop guards. Especially after watching the way she almost tipped over. Thank you for posting the video and the replies about being near the metal and the pine trees, very informative.
     
  9. delirious

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    The roofing is suspect. I know that if I calibrate my compass anywhere close to my F150 pickup or garage door. I get errors. If I step away by 10-20 feet. No calibration errors. I bet that's suspect. Also, Learn to catch it by hand. It's very easy to do and I personally wouldn't come in so hot like that. It's an expensive toy to be putzing around with. But it's your toy. Just my opinion.
     
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  10. IflyinWY

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    Great idea having a second camera rolling. That would have been difficult to believe without seeing from both videos.

    Strange behavior for sure. Is there a possibility of underground utilities where you were?
     
  11. DrewFlies

    DrewFlies Guest

    Irs
    Its not even about it being an expensive toy. If you descend to fast your quad will enter vortex ring and it will crash for sure.
     
  12. IflyinWY

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    The video was fast forwarded during the descent. Watch the people on the ground during that portion of the video.

    VRS would have caused a very noticeable wobble and the bird would not have hesitated. It would have just kept right on going until the earth stopped it.
     
  13. F6Rider

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    I would say that pile of metal roofing or whatever it is messed with your compass, it was close enough. The P3 compass is more sensitive than the P2 one, any close metal will confuse it, another reason I always hand catch, not to mention the debris kicked up when the bird goes into ground effect.
     
  14. DrChris

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    Any possibility that you have tweaked your attitude sensitivity? An attitude gain that's too high can cause oscillating type effects in some circumstances. Probably not your issue, but it's a thought.

    Chris
     
  15. snerd

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    ......
    So, yeah, the video was fast-forwarded, the people on the ground plainly give it away. So the descent was not as crazy-fast as you're implying. What's the back story here? Just because you're over 30 posts doesn't give you a pass lol!!
     
  16. IflyinWY

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    I guess you are asking why I made that post.
    I understood the previous poster, whom I quoted, to believe the rapid descent may have been a contributing factor. I was pointing out that I did not believe that was the case.
     
  17. dirkclod

    dirkclod Moderator
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    blank stare.png o_O
     
  18. IflyinWY

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    I gotta wonder too.

    Kinda in the middle of an important topic here snerd. ;)
     
  19. snerd

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    No, I was thinking that you were pointing out that when he said....................

    - P3 then started to descend rapidly (far faster than usual)...............

    that it was fast-forwarded to make it "seem" that the descent was faster than normal. Maybe my spidey-senses are working overtime, and there is nothing here to wonder about. If that is the case, please disregard my post with my apologies.
     
  20. Meta4

    Meta4 Moderator
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    This has nothing to do with the compass.
    The compass only has any effect in 2D flight.
    It can't make a Phantom go up or down.

    You can't descend too fast. DJI have taken care of that for you.

    I'm not certain what the issue was but I'd be wondering if it is related to kicking up dust and how that might affect the VPS?