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2 Props come off mid flight!!

Discussion in 'Phantom 2 Vision + Discussion' started by srchadwi, Jan 3, 2015.

  1. srchadwi

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    What a bad day for me.

    I'd been flying around totally normal for about 10 minutes. I was doing a nice slow pan about 30metres up, not far from me. Suddenly the engines cut out and as it fell - I SAW TWO PROPS FLY OFF!!

    The phantom is a total wreck but more of a concern for everyone is what happened. After about an hour I found both props. They had landed about 100m from the crash site (there was a bit of wind which would have helped to carry them) and about 10 metres from each other. They were like new - I can screw them back on the phantom just as normal - nothing was threaded etc.

    They had been tightened to the same amount as always - hold the motor and make sure they are snug.

    So what happened - I assume, contrary to what DJI claim, the props can loosen and given the particular flight maneuver you are doing can come off. I assume that once they are off somehow this can lead to the engines failing.

    It doesn't appear that two of the motors locked up and this is why they came off because the motors still turn by hand nice and free.


    Of all those people out there that have experienced a sudden fall from the sky is there anyone who had a prop missing when it landed? If so this could be the reason.
     
  2. crash1sttime

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    The props are supposed to self tighten and i dont know of anyway for them to come loose during flight, do you have video of the crash you can upload, i know there isnt sound but someone may be able to advise using the flight behaviour.

    Have you tried powering on the phantom since and see if the motors spin up ok (dont put props on)
     
  3. flyNfrank

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    Which quad do you have, and how old is it?
     
  4. srchadwi

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    I've recovered the video but the last 30 secs is missing unfortunately.

    Three of the motors power up perfectly - unfortunately the other one hit the ground directly so that arm is totally dead. So at least one of the motors that had the fly away props on is working perfectly.
     
  5. srchadwi

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    The Vision plus version 2 and I've had it about three months - no MODS.
     
  6. crash1sttime

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    Might want to take a look here

    viewtopic.php?f=27&t=32368

    not saying its your issue but its worth a read

    take the cover off and check the cabling to the other motors for signs of failure.
     
  7. Meta4

    Meta4 Moderator
    Staff Member

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    Bummer about your Phantom crashing.

    I'm no aircrash investigator and I'm not certain of the cause of your crash but I can't see how the props can come off in flight the way you suggest. If props could somehow come loose while flying, the stopping of the motors would be an even bigger mystery.

    The props can't "loosen" while the motor is spinning normally. The direction of spin will only tighten the prop and the speed is several thousand rpm. No flight manouevre will change this. The motors just keep on spinning in the same direction. The cause has to be something else.
    To undo a prop, the motor would have to reverse or, it has been suggested that inertia could cause the prop to unscrew with a sudden stopping of the motor and I think this is the most likely explanation for what you observed.

    Your initial description says .. Suddenly the engines cut out and as it fell - I SAW TWO PROPS FLY OFF.
    It seems highly probable that the motors cutting is what caused the props to come loose.
    That two motors did this at the same time is a puzzling factor.
     
  8. CannibalRobotics

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    If the engines stopped suddenly that might be enough loosen them or they were not that tight to start with.
    In freefall, the direction of the airflow would unscrew loose props.
     
  9. rotorwash

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    I have read about the wiring and the ESC being bad but wouldn't that be odd that two motors stopped at the same time? Thats the only thing that would cause the props to fly off IMO. Im thinking that the motors could appear fine after the accident. That a command/signal was sent to the motors that made them stop.
     
  10. syotr

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    I think you have the cart before the horse. Props will not come off in any normal maneuver since the direction of motor rotation is tightening them. The motors never turn backwards under power. The props do have inertia such that if a motor stops suddenly, the prop will continue spinning and unscrew from the shaft. Losing a prop should not damage the motor.
    I suspect that you simply had a complete and sudden power loss as in a battery wire separating from the board (bad solder joint.) Two of the props were loose enough to unscrew. It is best to use the wrench to tighten your props even when they are "self-tightening." Even if the two props remained on the motors, the bird would likely suffers as much damage in a fall from that height. Open up the bird and you may find the cause.
    I have had one incident where a motor stopped and a prop unscrewed in flight. I think it was caused by a loose bullet connector. This was on a Dex quad using DJI E300 system.
     
  11. gunslinger

    gunslinger Moderator
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    Props flying off during flight are almost always due to the motor suddenly stopping and the props unscrewing from the shafts due to inertia. Having two fly off at once is extremely rare and cause for concern.

    Have you ever had prop guards on this bird?

    -slinger
     
  12. rbhamilton

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    Self tightening also means self loosening IF the motor stops. Props flying off isn't uncommon. It means motors abruptly stopped.

    Two failed motors simultaneously? Means one or more of your ESC's failed. Probably a V3, right? The wires overheated and shorted - happens lots. Those wires are defective from the factory. Too small for the current. Overheating melts through the insulation on two wires causing a short.

    Hopefully you bought it through Amazon? If so you are in good shape - just send it back and it becomes someone elses problem. Otherwise? Well... Good luck getting DJI to replace the unit. And even if they did the new unit would have the same fault.
     
  13. crash1sttime

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    But the OP posted

    So it cant be the ESC or cabling issue we have seen prevalent on other Vision units or can it ?
     
  14. srchadwi

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    No never used them,
     
  15. rbhamilton

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    Intermittent short? Something stopped those motors. Or the props wouldn't have flown off.
     
  16. crash1sttime

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    yeah that would work, might be best get the lid of and have a good look inside
     
  17. tritontr21

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    Does your controller have the thumb wheel top left side of TX?

    (Figuring out what version he has)
     
  18. dbfletcher

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  19. tritontr21

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    I only saw "about three months ago." Did I miss something?
     
  20. dbfletcher

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    Looks that way.. here is the text from the link i posted above.