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Crashed... Expert Opinion Required Please

Discussion in 'Phantom 2 Vision Discussion' started by BazzaUK, Apr 11, 2014.

  1. BazzaUK

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    Hi folks,

    Last night, I had quite a scare whilst flying my Vision over the fields at the rear of my house. This resulted in me crashing the Vision and thankfully (or at least I hope) not doing any major damage. Let me give you a little info...

    I recently installed one of the 3D Power 2-axis Gimbals which I ordered. Did a flight with it and whilst it wasn't quite as rock-solid as some videos i've seen done with it, it worked fine. No problems at all. That is, until last night.

    I took the quad out and flew it up to about 500ft and took a few photos and videos etc. Battery was still on 70%+ on the quad, controller batteries were fine and the repeater batteries also fine. I started to bring the quad home and when it was around 60ft up and around 100ft away from me, I started to reduce height vertically... and thats when disaster struck!

    Suddenly, it began rocking from side to side uncontrollably and losing height. Nothing that i tried would gain control of the quad.. and this resulted in it crashing into the ground. Now, between me and the quad was a 6ft fence, so it also lost connection. Just as i was lifting up the fence panel to clamber under, I head rotors and it was hovering above me again!! Obviously it had somehow hit the ground, recovered itself, realised it had no connection and the "Coming Home" function had kicked in. Despite a slice in one of the props, it managed to land successfully where it was launched from (thankfully saving me a job of clambering under the fence).

    My question is... does anybody know what may have caused the sudden rocking side to side of the quad? Could it have been the gimbal freaking out, causing the quad to somehow try to compensate for it, and rock... hence losing control? It scared the life out of me and thankfully the quad didn't appear to be damaged (i've not had time to test it fully as yet).

    Also, does anybody else have a 3D Power Gimbal and can advise, from a newbie point of view, how to calibrate one? It came with absolutely no manual at all. Thanks very much for any help.
     
  2. AmosMoses

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    Were you descending when it started the side to side rocking?
    Sounds like a classic case of a vortices or a prop wash crash.

    Sent from my XT1080 using Tapatalk
     
  3. DaveTown

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  4. SilentAV8R

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    Severe rocking while descending is most likely a result of coming down through your own rotor wash. I come down in a spiraling arc so I am always in "clean" air. I almost lost mine of the 2nd flight due to this reason. Carry some forward momentum or spiral down. Stay out of the "dirty" air.

    Interesting situation yesterday. i was flying with a friend and he decided to hover his P2 directly over mine while in a hover. After a couple of seconds mine started to wobble severely as the his wash came down over me and disturbed the airflow around me.
     
  5. rfernandez

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    What they said!!! gimbal has nothing to do with it.
     
  6. SlackerATX

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  7. jimdenburg

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    Did it look like this...

    [youtube]http://www.youtube.com/watch?v=sw4Ej41niO8[/youtube]


    I was descending after a speed run in ATTI, but switching to gps, applying thrust or any other stick input didn't help. I was also using some cheap after-market props which made the thing act a little squirrely from time to time. While the weight of the gimbal might not have been the main reason for your issue, it very well may have played a part. Mine only stabled out when it was a few feet above the ice, and after it started to yaw a bit (at that point I was moving the sticks all over trying to get some reaction). In the event it happens again, I will try yawing. Sorry about the crash...it happens.
     
  8. gunslinger

    gunslinger Moderator
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    +1

    been there, done that, got the stained fruit of the looms...

    -slinger
     
  9. BazzaUK

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    Thanks for your help folks. Really do appreciate it. I suspect it may well have been to do with the fact i was coming down quite rapidly into my own down-draft.

    I have now replaced the broken prop, re-calibrated the compass/GPS and took it for a test drive in the garden. What i did notice is that where before it would hover almost perfectly steady, now it tends to do a lot of wandering, both horizontal (mostly) and also vertically (occasionally). In short, it just doesn't seem as stable as it once was, if you let go of the sticks. In fact, if you dare let go of the sticks, it doesn't stay still at all and wanders more than it doesn't.

    Any thoughts on what i could have done to make it this way? The lights are flashing green, and good GPS etc. The garden is about 10m wide by 30m long, so i don't think it's own draught off the fences either side is responsible. I've flown it in the garden a few times with a very steady hover if you let go of the sticks.

    Any help would be hugely appreciated. I have searched the forum and not found anything i think could be conclusive.

    Thank you in advance
     
  10. xgeek

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    Did you do an IMU calibration after your crash?. What are you mod values looking like in the the assistant?
     
  11. BazzaUK

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    I haven't done a IMU calibration for 2 reasons...

    1) I cannot for the life of me find a guide on how to do one. Not even on DJI website..

    2) When plugged into the assistant software, it tells me that i dont need to do an IMU calibration, so i trusted it.

    Do you think this could possibly be the issue?
     
  12. xgeek

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    It can't hurt doing one to rule it out. Especially after a crash.

    Its pretty simple. Just place the phantom on a level surface. I use a spirit level across the diagonals and shim the legs with business cards to get 100% level. Then just do an advance IMU calibration. Takes 5 minutes.

    You may get a warning about the IMU being too hot when you got to calibrate. Ignore that and continue anyway.

    Once done do another compass calibration in an open space away from any interference and test again.
     
  13. BazzaUK

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    Thanks for all the help so far. I've uploaded by IMU settings, just to see if they look about right?
     

    Attached Files:

  14. Drone-Outlaw

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    I'm sure it this has happened to every P2V pilot! Happened to me once when only a few feet off the deck and before I knew it the bird was props down on the ground with the prop spinners getting groung down a few mm's! Very lucky. It has happened 6 or more times to me, and vest advice is "not to panic"! Easier said than done I know, but crutial not to make any drastic stick moves. I have always just made a point not to make any adjustments and the letting the bird settle down on irs own. I mean "Maverick" even crashed and burned right......

    Speaking of "Mav" I have watched this video 10+ times and I laugh harder each time, very funny. It's as though you were able to time your incident to the movie soundtrack!
    Moose
     
  15. BazzaUK

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    Thanks for the feedback guys, really appreciate it. It seems pretty conclusive, it's a "flat spin out to sea" then (aka, decending too quickly into my own rotor wash). Have to agree with you Moose, that video is fantastic and had me chuckling like a good 'un!

    So, do those IMU stats look about right to the experienced eyes on this forum? The Vision thinks so, but as we know, that doesn't mean a great deal...