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Phantom crash - was it due to descending over powerlines?

Discussion in 'Phantom 2 Help' started by CharSiuFan, Oct 11, 2014.

  1. CharSiuFan

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    Hi All

    http://youtu.be/OySt_iRUj6c

    The clip above is the final 30 seconds of a flight using my Phantom 2. The battery level was showing around 25%. As I brought it down slowly to land it started to wobble and lose height. I tried to throttle up but it wasn't responsive. Luckily its fall was broken by trees and the damage was minimal. Total flight time around 10 minutes. Was it due to descending over powerlines that caused this wobble and crash? I have seen it do a similar thing back in February. It dropped about 20 meters but did recover and I was able to land it. Any ideas or thoughts? Thanks.

    http://youtu.be/OySt_iRUj6c
     
  2. CallMeAlan

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    Re: Phantom crash - was it due to descending over powerlines

    VRS!
     
  3. CharSiuFan

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    Re: Phantom crash - was it due to descending over powerlines

    Hi Alan

    Do you think definately VRS? I do try to descend whilst moving in another direction but I guess when concentrating on other things one might forget.
     
  4. phantomi

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    Re: Phantom crash - was it due to descending over powerlines

    I think powerlines has not about, but a not so slowly descent. I also think VRS.
     
  5. Wedeliver

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    Re: Phantom crash - was it due to descending over powerlines

    beautiful country side. Realy looks like you were making a nice video.
    that said, I have seen that wobble. could you hear the motors and did you notice what kind of sound they were making? are you sure there is no damage? what kind of gimbal/camera is onboard this p2? do you know the weight?.

    Either way you have documented a problem that should be corrected. I would not be surprised if you have the occur again. I wonder if a combination of factors need to be present for this event to progress from a little wobble to crash?
    thanks for sharing.
     
  6. CallMeAlan

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    Re: Phantom crash - was it due to descending over powerlines

    CharSiuFan, it looks like VRS to me. It's that telltale unstable wobbling that declares VRS, as Wedeliver said. I have seen it in my own videos when I first used my Phantom, and before I knew anything about VRS. Now I try to circle or move side to side, but I also avoid too much height too.
     
  7. N017RW

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    Re: Phantom crash - was it due to descending over powerlines

    Yep.

    Your crash was due to aeronautics, not radio or electronics.
     
  8. CharSiuFan

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    Re: Phantom crash - was it due to descending over powerlines

    Thanks everyone. That makes sense. For those who might be interested that was the last thirty seconds of a clip where I flew to the top of Lantau Peak, Hong Kong's second highest mountain (934m, took off from about 400m) to get some footage for a race that was held last night. I then was getting some footage of the Lantau Buddha (seen at the start of the clip) which is, I'm told, the world's largest outdoor sitting Buddha.

    I had installed an H3-3D gimbal, upgraded from my original H3-2D. I also swapped the gopro connector from the old gimbal to the new. This was the first flight with the new gimbal and it really wasn't behaving, often pointing at the Phantom leg as can be seen. It behaved like it was 'drunk'. Guess I need to try calibrating it. Fortunately no obvious damage to any of the kit. I did lose one of the gimbal rubber dampers. Consider myself very lucky. :)
     
  9. MrGof

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    Re: Phantom crash - was it due to descending over powerlines

    I have a simular problem but not nearby any powerlines. I was flying in a big field and about 25-30 meter up andeverything worked very good. The I decided to decend the Phantom and now it happend the 3 rd time for me. Sowly decending a couple of meters when suddenly the Phantom starts to wobbel and after with engines working falling like a stone to the ground. As I said, I was all times flying in a open field, so no more damage than some propellers, but can somebody tell me what went wrong? Nearly about the same thing three times now and I had all batteries full charged when it happend.

    Hope anybody out there can give a newbie some tips what to do to awoid this a fourth time.

    Mr Gof
     
  10. CharSiuFan

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    Re: Phantom crash - was it due to descending over powerlines

    VRS - Vortex Ring State. Keeping it simple it means the air coming into your props is the same air it just pushed down for lift. So your quad loses lift. Have a read of the article on Wikipedia - it might help.

    http://en.wikipedia.org/wiki/Vortex_ring_state
     
  11. Wedeliver

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    Re: Phantom crash - was it due to descending over powerlines

    After reading some folks description of how their bird crashed as they were desending I wonder if somehow CSC is somehow engaged and that is why some of the crashes happen. I think this can happen by holding the left stick down and toward the center or ourside and then bringing the right stick into the same position...on my table it turns off the motors instantly.

    MrGof, it makes sense and I have heard that sometimes when a quad is going into a VRS situation the motors will rev up to try and compensate for the lack of lift. You mention you could hear your motors, do you think they were trying hard to stop the event before you hit the sticks? Are you using a stock Vision plus.. any extra weight? Are you using special props? Have you ever crashed or landed in sand that could be effecting the motors...

    The problem I have is it falling to the ground like a stone from over 50' in the air. I would think it would at the very least try and recover, so then I start to think of the motors being turned off, which would make sense from how it fell, but not your report of the motors still working. I hope we can all get a grip and an understanding of this issue.

     
  12. Damon

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    Re: Phantom crash - was it due to descending over powerlines

    My vote is VRS. I also found it real strange that the camera was turned severely left catching shots of landing gear all the way down, not trying to center after making yaw turn. What gimbal/camera are you using?
     
  13. CharSiuFan

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    Re: Phantom crash - was it due to descending over powerlines

    Hi Damon - I'm assuming that question is aimed at me. It's an H3-3D gimbal with a gopro attached. It was my first flight with that gimbal having just upgraded from the H3-2D - except for a couple of tiny flights for testing after I installed it (when it appeared to be working ok) . You are right, it did keep pointing at the leg. It was very erratic. Worked part of the time but not others. Seemed to over compensate on turns and end up filming the leg. I saw some videos on YouTube on how to recalibrate. I'll try that next time I have time.
     
  14. Damon

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    Re: Phantom crash - was it due to descending over powerlines

    Definitely do a full IMU calibration after crash. Then a compass calibration in the field before flight.

    With that gimbal looking to the far left might also be an indicator of a bad gimbal or a gimbal in need of balancing. The gimbal acts like it lost power or was stuck rebooting, as they tend to snap to that position in flight on reboot.
     
  15. MrGof

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    Re: Phantom crash - was it due to descending over powerlines

    Thank you very much for your answer CharSuiFan.

    I shall read about VRS directly and see what it can help me to avoid this in the feature. I have never heard about VRS before but you ever learn something new as long as you live. Thank you.
     
  16. MrGof

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    Re: Phantom crash - was it due to descending over powerlines

    Hello Wedeliver and thanks for your answer.
    No, I have not been landing in sand as I know of. Yes the engines sounds to work as they did moments before it started to wobble. I have A Phantom 2 with a 3D gimbal with a GoPro Her 3+ mounted and equipment for FPV and it is a specialist who has build it for me when I bought it some months ago.What I can not understand is, that I totally loose control of it and it does not react on anything I do on the transmitter when it has started to fall down.
     
  17. houldsworth1

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    Re: Phantom crash - was it due to descending over powerlines

    Now that is very interesting.

    I had a crash in my back yard, just hovering about 4' off the ground. The bird suddenly started behaving very oddly and not responding to any inputs as I would expect.

    Up to now I have been assuming that this was a low level "fly away" but now I think it might have been VRS. Hmmm...wondering how I can tell the difference.