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Flying with just 3 props/motors?

Discussion in 'General Discussion' started by jwegener, Oct 10, 2014.

  1. jwegener

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    What happens if one of the quadcopter's motors dies midflight? Can the phantom stay afloat with just three? Or at least make a somewhat graceful landing?

    Any videos of this happening that you guys have seen?

    Jonathan
     
  2. N017RW

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    No chance of a controlled 'landing' with a P1 or 2... it's a crash for sure.

    Quads are under-actuated and not fault tolerant of a motor, ESC, and to some extent a prop failure.

    Edit: Fixed spell-check replacement, replaced actuated with articulated.
     
  3. jwegener

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    I could imagine a world where the opposite propeller suddenly starts shifting backwards to achieve wobble balance and the two other ones go extra hard to keep it up in the air. Or is that impossible?
     
  4. N017RW

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    Anything is possible. But would it be affordable to the masses?

    Another scenario is to shut off the opposite motor, apply as much power as possible while adding yaw for stability and softening the impact.

    No guarantees though.
     
  5. dlunk

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    I watched a TED Talk about quadcopters a while back. In one part he talks about a similar scenario dealing with (in this case) prop failure. He trims two of the props so that only two are lifting the craft. It begins around the 6:15 mark (https://www.youtube.com/watch?v=w2itwFJCgFQ#t=373). I don't know how something like the Phantom would handle this situation being that it's probably not balanced in a way to allow the type of spin shown in the video necessary to maintain airborne. Basically it seems like a possible idea that if you have one motor failure a quadcopter could be programed in a way to shut off the opposing motor and not fall like a rock, admittedly though it wouldn't be a smooth landing.
     
  6. N017RW

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    Yea of course. It was established the Phantom is doomed and I guess I moved more towards the theoretical.
     
  7. Monte55

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    Even if two props ....opposite corners of quad could lift the craft or at least slow the decent and the odd motor shut down, how could the quad yaw at all to provide any level attitude if the two working motors are turning the same direction
     
  8. HarryT

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    This is precisely why all professional multi-rotors are hex- or octo-rotor craft, because they can land gracefully after a motor failure. You really don't want your professional video gear to fall out of the sky if a motor fails!
     
  9. derrickduff

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    dlunk provided a link that explains how this is done. https://www.youtube.com/watch?v=w2itwFJCgFQ#t=373

    You basically give up yawin order to keep control of pitch and roll. This would be an excellent fail safe feature to at least minimize damage from a lost motor.
     
  10. N017RW

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    It would Yaw uncontrollably by nature of both (remaining) motors spinning in the same direction.
     
  11. Monte55

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    After I posted that I thought it would yaw but by itself without control. That may be a good thing. If only two opposite motors were lifting, it would want to tilt to either one of the downed motors. But if it is constantly yawing it might try to stay level enough to get it to ground providing two rotors could even keep it in the air and gyro didnt freak out.
     
  12. BWJ

    BWJ

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    Try to take off one prop and start up, it can lift and fly, but not stable like normal, - have tryed indoor.
     
  13. Monte55

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    Are you saying you have done this.?
     
  14. SteveMann

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    I had a hex lose a prop at 100ft that was able to stay mostly under control. I was able to land it with minimal damage but steerage was wobbly and it lost another prop when it hit a mailbox.
     
  15. jwegener

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    Thanks so much for the interesting discussion everyone!
     
  16. IflyinWY

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    I disagree Geert,
    I think it will go in a bunch of different directions on it's way down. That's what mine did tonight when the prop guard broke and tangled in the prop. Darn power pole.
    :lol:
     
  17. rjstone

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    Supposedly the Naza controller can handle a single motor failure with the hex or octo configurations, but not with a quad configuration. So if you want to be able to deal with motor/rotor failure then you'd need to get something with 6 or 8 props on it.
     
  18. Wedeliver

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    I had a prop fly off, it went straight to the ground.
     
  19. Noël

    Noël Guest

    Some time ago I posted a video of multi rotors losing props with special software running on it.
    They managed to fly okay after losing a prop.

    I believe that it could still do a controlled landing when losing 2 props.

    Again it was using special software to do this.


    I'm using my phone at the moment and searching is kind of hard to do with it, but the post is on this forum some where.