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Wobble of Death...But Survived

Discussion in 'Phantom 2 Vision + Discussion' started by srandall25, Jul 3, 2014.

  1. srandall25

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    BLUF: Phantom flying near rock ridge in mountains, wobbles violently uncontrollably about 30' high, doesn't respond to any control inputs including my full throttle left stick up to ascend.. it keeps wobbling while descending.. hits rock ridge (side of mountain), tumbles down about 15'... Battery ejected but good. 3 broken props, gimbal and camera NOT harmed!!!! Thank you, thank you, gimbal guard!!!

    Screen shots of Assistant Software here: https://picasaweb.google.com/srandall31/ScreenShots02
    -- Connected phantom to computer with software running and powered phantom for first time since crash...
    -- States it's in failsafe mode... and compass error!!
    -- Recalibrated compass & did an advanced calibration - compass is now good... I had to use a magnet... followed Colin's method.. https://www.youtube.com/watch?v=kCT1rRE_UIg

    Ok, so this same thing in almost the same area, happened to me once before... I sent the phantom back, got a new one. The new phantom has been flying flawlessly... flew 3 batteries perfectly fine today. Installed 4th battery (fully charged)... at around 50% charge, 30' high, near the side of a rock ridge, this violent wobble happens. It appears something may have disturbed the compass.. some signal interference of some sort; however, I'm not sure if the crash itself could have caused the compass calibration to be off and there might be some other problem. I would like to think that it was some outside interference with the compass because that would mean that there is nothing wrong with the phantom. Just not sure... I hate when this happens because I lose faith and afraid this can happen again...

    I was flying NAZA mode, both switches full up... when wobble happened, I switched to ATTI, pushed up on left stick to ascend, and nothing changed... still wobbling and falling... I'm reliving the same nightmare I had with my first phantom.... again, I hope I chalk this up to a fluke outside signal interference with the compass... Your thoughts?
     
  2. FrankPA

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    I'm a glider pilot, so I know from seat of the pants experience (though thankfully, not at 30'):
    1) Windward side of a ridge can have some amazing updrafts, and conversely,
    2) Leeward side of the ridge can have some vicious downdrafts!

    Flying on the lee to stay out of the wind perhaps?
     
  3. srandall25

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    Oh, there was less than 5mph winds... VERY calm.. and I was standing about 30' away from the bottom of the ridge.. There had been very calm winds for the past 2 hrs prior to this also, so it was very consistent. I'm certain that wind was not the cause of this... also the fact that there was absolutely no response to my control inputs, tells me it was most probably something else... anything is possible but watching that violent wobble and no winds near me being so close... i'm almost certain it was something else... I'm still thinking compass interference... Thanks for your input though... good to keep in mind.
     
  4. FrankPA

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    Here's another possibility: VRS.

    If you're on the windward side, a 5mph wind is 2.23 m/s (pointing up). If you're running current fw, then you can descend at 2m/s for a total of 4.23m/s down in the "fluid" of atmosphere, more than enough for VRS. Now, if you're running older fw, it could be even faster... the "wobble" does sound like VRS.
     
  5. srandall25

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    Ya, i've read a lot in these forums about VRS... There was just no wind at all at this time, now i know it's possible there could have been something near the phantom that I didn't feel, but it was just so calm this morning... I just really don't think this was it.. the compass calibration was completely off when I hooked up the phantom to the assistance software.. I'm wondering what could have interfered with that...
     
  6. Skynet1

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    The values as it relates to phantom's compass mod settings vary depending on where the info comes from, Collin, mentioned a 1400 -1800 mod value, while DJI support staff, has advised a lesser value of 1200 -1500. These values I had thought may vary depending upon other external affects on the compass in conjunction with the local of the phantom at any given time.
    An interesting comment made by Collin in his compass fix video is at approx. 6.13 minute mark on the video, where he states that the compass should not affect flight control when in (Att. mode), but more so when flying in GPS mode.
    I have re-read your comments, and noticed you had no control when you had tried switching to Atti, and so as you have mentioned, there very well may have been something else going on with your Phantom affecting control at that point.
    Just a thought!
     
  7. srandall25

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    I'm not 100% i gave the ATT enough time to engage... it all happened so fast. I so wish there was better on-board diagnostics to help determine reason for a crash. I need to install my flytrex soon!!
     
  8. Dirty Bird

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    Location:
    Glen Burnie, MD - USA
    Glad your Phantom survived her mishap. Good thing you had that camera plate on there!

    You sound like me...still have my Flytrex sitting in the box. :oops:

    Still haven't received my Trax either and its been almost two weeks since you got your's! :twisted:
     
  9. srandall25

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    You can have my Trax if you like... haha
     
  10. jspradling7

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    Is there a chance that these machines are getting into the computer equivalent of Pilot Induced Oscillation?
     
  11. srandall25

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    So i've been watching youtube videos of peoples self proclaimed VRS with their Phantoms and the wobble does indeed look very similar to what I experienced today. I'm thinking this actually could have been what happened. The nugget of information that I got from my research was that full throttle up in this state can or will only make it worse. I've read in the past that the best way to fly out of a VRS is to use the right stick and and pitch forward/backward or left/right out of it.. What I didn't realize is that I should not have full throttled up with the left stick....

    So assuming this was a VRS, if I experience this again, I will do two things. 1) Flip S1 to ATT. 2) Quickly move right stick in any direction away from any obstacle. This is the only thing I know I can do if this happens again. It's important to know and visualize what you might do in certain situations before they happen because when it happens, you have very little time to react. If you haven't thought of it or studied it, you won't react appropriately when the time comes. Because I've read a lot about this in the forums, I did think quickly enough while in the wobble to switch to ATT.. something I would have never thought to do if it weren't for the forums. Unfortunately, that didn't save me.. however, maybe next time (if there is one) I will have enough time to perform an S1 switch and pitch control to save it. Also, having been a student of the forums enabled me to know immediately how to calibrate my compass after the crash, when the software wasn't able to. And while I was messing with all this, my Tx started beeping.. Normally I would have thought that the batteries were low, but I knew better, because I remembered reading that the controller is designed to beep after left on and idle for so many minutes. Reading these forums will teach you so many things that you just can't learn from a manual... Now I'm not saying the battery issue wasn't in the manual... ;)
     
  12. Skynet1

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    Evaluating your options and responding within a split second decision is most definitely a difficult and challenging task, to say the least.

    Many government agencies, Armed Forces and First Responders alike train for various incidents requiring immediate action.
    Fighter pilots practice various combat scenarios which may require quick thinking and response to any given situation, and the end result is what may be termed Muscle Memory action, and or reaction to a given situation.
    That having been said, it's not a bad idea to practice various scenario's which may require a quick and immediate response, one which will not necessarily compound the issue, but help rectify it.
    Eg. Imagine, if you will that your quad is flying away from you at a rapid rate of speed, what would be your 1st step or immediate action to regain control, and follow-up actions should that not work, etc.
    This concept of training your yourself in anticipation of such incidents will help you to react without thinking, and hopefully regain control, eliminating the time normally taken to decide a course of action, thus preventing what may ultimately turn into a disastrous conclusion.
    Again, this training concept would work on an number of potential situations, including VRS.
    Simply apply the scenario within your mind, and immediately take an appropriate course of action as you respond to such recognized flight symptoms, such as fluttering, downward toilet bowl effect, and other such erratic behavior with an immediate predetermined response, as you have mentioned is spot on.
    " An ounce of prevention is worth a pound of cure" I believe is the adage.
    Fly safe, and may the force be with you.
     
  13. srandall25

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    Very good points... So I will summarize very briefly my take away from this experience.

    If my phantom exhibits an uncontrolled wobble:

    1) NO left stick actions (throttle up with left stick is known to only make it worse)
    2) Switch S1 to ATT
    3) Right stick out of it in any direction, but choose a direction and stick with it. Moving the right stick in many directions within seconds may not do anything to rid the VRS.