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The Vortex Of Death

Discussion in 'General Discussion' started by Ton4, Feb 4, 2014.

  1. Ton4

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    Changed some Parameters in the SimpleBGC setup, will not bother to list them, it could not hold Horizon. At then at the end of the flight I descended too fast and with carbon fiber props, this means an instant loss of control, the "vortex of death"; descending in your own prop wash causes loss of control. Did some moves with the sticks, no effect. Saw it go down through my FPV goggles.

    Actually I was in forward flight, but I just pushed the stick a bit down more. It reduces the forward speed enough to crash.

    After a 30 minute search, FPV signal was still broadcasting but just a showing a close wall I guess, searching for the strongest video signal, I found the DJI Phantom by listening on a high roof, after I started the motors. After an hour or what, long enough ladders were found and I got sight of the Phantom again. Intact, and still showing the fail safe flashes. I already brought my transmitter home. The Gopro had been recording a long time (50 minutes) until the battery was finished. The Phantom was still intact, gave it a quick start at home, everything looked fine.

    The power plug of the Gimbal had to be renewed only, just lost some softballs.

    Calibrated IMU, although it said it was not needed, and did a test flight after the crash. With the default CM3000 parameters. It still wobbles too much, but holds horizon. Phantom still flies as before the crash.

    The crash video:

    [youtube]http://www.youtube.com/watch?v=IEtUgIbkC1U[/youtube]
     
  2. justflie

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    Ouch, but glad you got it back ok.

    Does throwing it into manual mode allow a chance at recovery or are you just screwed everytime this happens?
     
  3. Ton4

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    At first I tried fiddling the sticks a bit, and then I lost signal on the goggles. It happened too quick to weigh options :)

    I thought forward flight, must be ok, but lost too much speed when I started to descend a bit faster.

    Anyway, these cf props are ****. Probably there are better quality around, but mine :(

    I tried to solve a wobble in my gimbal, only to find that also this wobble was due to these props. And they were balanced, by yours truly. There must be other problems with these props as well. There are people around selling ****.

    Better stick to real brands, balancing is not enough.
     
  4. LeoS

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    Good info, Ton. I'm glad it all worked out for you, your latest video is super smooth. I guess it's worth it ;)

    Btw, where did you get the CF props? Link to ebay/amazon please, so we know what to avoid.
     
  5. Ton4

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    Amazon. Afaik there is only one seller with these.
     
  6. LeoS

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  7. Ton4

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  8. EMCSQUAR

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    Location:
    N 44.895 W 93.354 Minnesota
    Ton,
    the Amazon props may have contributed to the death spiral, but P2 props w/the aggressive pattern are a little less forgiving when descending. I have to remind myself to land slowly and to not descend straight down - she gets real wobbly
     
  9. Ton4

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    No more cf vision style props for me. Plastic it is.
     
  10. Ton4

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    And BTW, I balanced them quite good. But they still gave me wobble in my video. So they have other issues as well, I guess.
     
  11. justflie

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    Are APC plastic props generally more forgiving than the CF blades?
     
  12. LeoS

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    By balancing you evened out the weight between the two ends of the props, but they could've been manufactured with uneven shapes/angles in the first place. Or even differences between blades.
     
  13. ElGuano

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    i know you will, but stay careful with the plastic. There are many, many reports of wobble and crashes with plastic 9443. VRS won't be much affected by the small difference in material stiffness, but the difference in profile with a 9.4" diameter is tremendous, x4 it's like 40% more surface area. That's the main culprit.

    Also, as with knockoffs, you may have gotten a bad prop. Mine have been ok but I always test the profile and fit, just in case. I do like the DJI plastic props, I wish they made the 9443s in non-self-tightening.

    Sorry to hear about the crash! Glad everything was recovered ok.
     
  14. Ton4

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    Would not know how to test a profile?
     
  15. Ton4

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  16. ElGuano

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    I mean stock DJIs :) I think the risks for knockoff plastic are the same with knockoff carbon props (quality control is probably nonexistent).
     
  17. Ton4

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    So, how to test a profile??
     
  18. ElGuano

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    Gotta eyeball the pitch very closely between props (and if you have them, compared to a genuine DJI prop), make sure there are no noticeable deviations (blade defects). When you install on motors, make sure that the tips are the same height to the ground, and the same height as each other from the top of the shell (hub defects). If one of the blades rides higher or lower, you're going to have excess vibration and you can't eliminate that with gains or balancing. The DJI props are ok, but I've had knockoff 8" props (plastic and CF) that had to have hubs sanded a bit to true.
     
  19. Ton4

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    Ok, thanks..,
     
  20. Ton4

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    Someone at rcgroups suggested I may have shutdown motors accidentally, so this vortex thing may not have been the case...

    I may have been below 10% throttle too long.

    It could be a shutdown, because the props were not damaged, and they didn't seem to be rotating after the crash....

    DJI should be slapped in the face for creating a flight controller not knowing it's flying and therefore a pilot is able to shut down motors while its flying, accidentally.

    Something like an Airbus would be able to raise its gear while parked on the terminal.