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Lose of propeller during flight

Discussion in 'Phantom 2 Vision + Discussion' started by greyphantom2, Sep 10, 2014.

  1. greyphantom2

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    Hi there

    I had been flying for about 1min 20seconds at an altitude of about 80-90m. I was in a rural area with the only other things around being a 33kV power line running along the road I was flying above, but I was about 70m clear of this.

    Suddenly the P2V+ went into a dive bomb (according to my Flytrex reaching a speed of 80kph) and landed in thick bush. There were only three propellers on the Phantom and the 4th one I found on the road side approximately underneath where it started to dive bomb. The lost prop was in good condition, no damage to the thread on the prop or on the Phantom.

    How did the prop come off? They are self tightening.
    Has this happened to anyone else?

    When I first connected to the Phantom and went to the Camera screen in the app it showed the battery level as zero even though the battery indicator lights said it was full. I turned everything off and on again and it was OK. Strange.

    Thanks for your help. I'm a bit nervous to fly it again now.
     
  2. Damon

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    Motor stopped, inertia spun it off. Since they are only hand spun tightened. Just my theory. Does that motor spin freely now?
     
  3. DBS

    DBS

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    Correct assessment... the only thing that can make a self tightening prop come off in mid flight is a sudden motor jam at speed...

    Motor stops ... prop keeps going due to inertia... boom... done deal :ugeek:
     
  4. Damon

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    Bad bearing to stop that quickly?
     
  5. LuvMyTJ

    LuvMyTJ ADMINISTRATOR
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    Call me OCD but I snug each prop with the wrench to prevent just such an issue.
     
  6. Damon

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    Hey OCD...Just messing with you. But honestly if the motor stopped that violently. It was going to tumble to an awful death anyways...right?
     
  7. Damon

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    On the bright side..he probably has a Flytrex descent speed record ;)
     
    IflyinWY likes this.
  8. LuvMyTJ

    LuvMyTJ ADMINISTRATOR
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    If it re-started and he was at a good height it may have recovered. No way to know really.
    Besides, I would assume the inertia of the prop would have made them tighter, not looser.
     
  9. Damon

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    Quite the opposite the blades are spinning in the direction the blades come off. The sudden stop of motor shaft will allow them to spin off by the props own inertia.
     
  10. LuvMyTJ

    LuvMyTJ ADMINISTRATOR
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    You sir are correct. I was backwards on that one. What would cause a dead stop in the first place? A seized motor, but that would be obvious.
     
  11. Damon

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    I can only think that the bearings seized up on that motor. Or something like piece of metal got magnetically sucked in between the stator and bell housing causing the bind. I would definitely at the very least take the suspect motor apart and change out the bearings. But trust being the issue, complete motor change out might be most comforting.
     
  12. DrJoe

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    You are correct:
    The motor jammed so violently that the prop's inertia carried spun it off, resulting in the plummet.
    Or, maybe, you have a cracked propeller hub.
    Or maybe, the prop didn't come off until after the crash (like 3 of mine did when it crashed), and you have a mysterious loss of control incident.
    The bird never lost power, correct?

    At the very least, I would recommend removing your gimbal, and performing some ground tests and then low level flight tests (1-3m) above some grass IF the prop attaches and the motor spins freely.

    Please note, there was a thread on this in May or June. One poster reported poor/defective threads on the motor. Replace that motor and ESC, or you'll worry every time you fly.
     
  13. ToThePoint

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    Yep that motor needs attention and/or dismantling @ least for a inspection on lose parts and/or damage.
     
  14. dannytroy

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    Yes, I'd replace both to be on the safe side. They are cheap enough to replace both. A lot cheaper than a possible broken camera/gimbal on the next crash.
     
  15. gunslinger

    gunslinger Moderator
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    Check to be sure the E ring and/or thrust washer on the bottom shaft of the motor didn't come off and get sucked into the motor... It's happened... Grab the threaded shaft of the motor and pull up and down... Does it move?

    -slinger
     
  16. greyphantom2

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    Thank you all for your helpful replies.

    Yes, the 'sudden motor stop and propeller inertia' theory came to my mind last night too. I did not put the props on very tight, trusting in the self-tightening. I will definitely be cinching them down now.

    I turned the Phantom on and ran the motors with no props on after the incident and they all seemed to run OK. So if there was a jam or very sudden decrease in motor speed then I could not tell. I'm positive that the rotor did come off before the crash, the phantom was in thick bush about 50-80m from the prop which was on the road verge.

    I will run a test on self-tightened props this weekend. I will fasten the Phantom to the ground, loosely put props on, start it up and slowly increase lift and then cut the motors and see what happens. This might give insight into what could have happened. I'll let you know how it goes.

    Camera is still working but the gimbal thrashes around frantically, so I'll be taking it off to have a look at.

    Cheers
     
  17. greyphantom2

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    I fixed the Phantom to the ground, screwed the props on until they made contact and then just eased them off so that they we just loose. I started it up and it didn't seem to matter if I just let it idle or power it up more, the props seemed to tighten up as much as I would normally finger tighten them. When I cut the motors none of them come loose.

    I could not simulate a motor jamming and stopping instantly which I believe would have had to happen for it to come of due to prop inertia, but the Phantom appears to fly fine during a flight around my back yard.

    I will be making sure the props are on good and tight in the future just in case.
     
  18. Damon

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    Did you take the suspect motor off frame to check if e-clip and brass shim are still on bottom of shaft. Did you take suspect motor apart to check stator and bell? Something could be lurking inside.

    Check wiring from motor to ESC short could cause motor to stop or actually reverse.
     
  19. Damon

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    How ironic, I have now fell prey to this exact failure. Flying on third battery all of a sudden free fall and that signature floating prop following the quad down.

    It looked like a white hand grenade went off when the Phantom hit the ground. Two props 1 battery and 1 white zenmuse dampener and 1 tk102 with cross brace flying from impact zone ;)

    Checked the motors and they hand spun freely, no grinding or indication of seizing.

    Gathered everything. Went home took off vtx and gimbal go pro combo.

    Pulled lid and everything looked fine inside except for minor cracking in lower shell. All wires looked good.

    Put just the P2 back together, full IMU calibration and out to test after compass calibration.

    Lift off hovering about 10 feet fine, then close maneuvers. All of a sudden off flies the prop and another fall.

    Now that I identified the suspect arm. Put prop back on and the suspect motor just sputters. Once home tore it apart again. Spun up the motors while moving wires from ESC to the motor. It appears to be lose connection at base of motor, as all the solder joints at ESC are good, but I can get it to work and then sputter while wiggling wires at the shrink tubing at base of motor.

    I guess I now get to brush up on my soldering :0
     
  20. singapore_phantom

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    Hi Damon,

    Quite unnerving, that. But how do you think the prop managed to pop off? Is its thread worn perhaps? Is the hub a goner?

    Cheers.