Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

Is it possible to get a vortex ring state while hovering?

Discussion in 'Phantom 2 Vision Discussion' started by jetdust, Aug 15, 2014.

  1. jetdust

    Joined:
    Feb 12, 2014
    Messages:
    72
    Likes Received:
    0
    My brother's phantom recently came crashing out of the sky from what appeared to be a motor failure from what I could tell while there. The phantom was leaning to one side and came down to the ground and crashed. We sent it in and were told that it crashed due to a vortex ring state which can occur while hovering. Ive heard of this occurring while descending but not from hovering. Ive let my phantom hover for several minutes and never had a problem and I thought this problem was fixed in one of the recent software updates as far as decent speed goes anyway?
     
  2. Damon

    Joined:
    Jun 25, 2014
    Messages:
    674
    Likes Received:
    5
    Location:
    Eastern Wa.
    Re: Is it possible to get a vortex ring state while hovering

    Did he have prop guards?
     
  3. jetdust

    Joined:
    Feb 12, 2014
    Messages:
    72
    Likes Received:
    0
    Re: Is it possible to get a vortex ring state while hovering

    no prop guards, completely stock..
     
  4. BigTulsa

    Joined:
    May 29, 2014
    Messages:
    207
    Likes Received:
    1
    Location:
    Tulsa, OK
    Re: Is it possible to get a vortex ring state while hovering

    If there was truly a motor failure then the quad would have started tumbling *** over teakettle until the power was removed, then it would have fallen like a stone.

    VRS CAN happen during a hover, especially in very light winds. Having prop guards seems to increase the occurrence from what I've read and heard. That's why I will not ever use propguards on anything other than my little Hubsan nano.
     
  5. ProfessorStein

    Joined:
    Jun 20, 2014
    Messages:
    1,136
    Likes Received:
    3
    Location:
    Portland, OR
    Re: Is it possible to get a vortex ring state while hovering

    Seems unlikely. How did "they" determine it was VRS??
     
  6. jetdust

    Joined:
    Feb 12, 2014
    Messages:
    72
    Likes Received:
    0
    Re: Is it possible to get a vortex ring state while hovering

    ased on your report of the crash, I would theorize that what you experienced is what is known as "vortex ring state" in short, when a drone hovers in one place, a vortex of propeller wash can be created underneath the drone, the drone then tries to compensate for the low pressure (which it interprets as a rapid descent) by spinning the props faster (which would account for the loud whirring you heard before the crash). This causes a greater vortex beneath the drone, and it essentially falls through its own wake. The solution is to rapidly steer the drone out of the wake by directing it either forward or backward, without throttling up (higher speed only increases the effect).

    Unfortunately, since this is avoidable, it is considered operator error and is therefor not covered under warranty.


    It was 100' or so up and we were 100' away from it. Basically sounded like it was full power and came out of the sky at an angle and crashed. We've had these since Feb and have flown just about every day without a glitch until this happened. It seemed like a motor went out to me but then again I've never seen one go out.
     
  7. ProfessorStein

    Joined:
    Jun 20, 2014
    Messages:
    1,136
    Likes Received:
    3
    Location:
    Portland, OR
    Re: Is it possible to get a vortex ring state while hovering

    I just came in from hovering my Phantom for 16 minutes. No sign of VRS. I suppose, technically, it's possible... but it's feeling like they just want to get out of a warranty replacement. There's no way they can get a report of "loud whirring" and definitively attribute it to VRS (or, at least definitively enough to void a warranty), IMHO.

    Plus... I don't really believe that VRS is fully "operator error". One, it's not something that DJI itself tries to train pilots to recover from. And while the pilot CAN learn to avoid and recover from VRS, actually getting INTO the situation is as much a design issue as it is an operator issue (as proven by DJIs release of newly-styled props to try to mitigate prop wash).
     
  8. Damon

    Joined:
    Jun 25, 2014
    Messages:
    674
    Likes Received:
    5
    Location:
    Eastern Wa.
    Re: Is it possible to get a vortex ring state while hovering

    Go to 3:35 of this quad crash video. http://www.youtube.com/watch?v=Vs02CQpg1Vs Notice it flips and rolls numerous times. That's a motor failure.

    You describe leaning and falling more like an IMU failure.
     
  9. GerdS

    Joined:
    Aug 14, 2014
    Messages:
    83
    Likes Received:
    0
    Location:
    Germany, lake of Konstanz
    Re: Is it possible to get a vortex ring state while hovering

    I think it's very unlikely to get into a VRS during hovering over flat surface. But I can imagine if you are flying at a hilly location where upwinds or thermik could occur.

    Regards, Gerd
     
  10. CarlJ

    Joined:
    Feb 24, 2014
    Messages:
    782
    Likes Received:
    19
    Location:
    Peru, Indiana
    Re: Is it possible to get a vortex ring state while hovering

    Props cause VRS, prop guards have zero movement, and are not the cause of VRS. If you think you're experiencing VRS simply move from the area of disturbed air, if it goes away then you just experienced VRS. Prop guards "MAY" exacerbate VRS, but we have no data that proves this is true.

    Again, there is zero evidence that prop guards have any effect on VRS, and any claim to the contrary is supposition.
     
  11. jetdust

    Joined:
    Feb 12, 2014
    Messages:
    72
    Likes Received:
    0
    Re: Is it possible to get a vortex ring state while hovering

    Calm night with no hills or anything out of the ordinary, just flying around the house basically in flatland Illinois.. I was flying also and had no problems..
     
  12. general01

    Joined:
    Feb 27, 2014
    Messages:
    468
    Likes Received:
    4
    Re: Is it possible to get a vortex ring state while hovering

    Sounds like the imu had a issue to me

    I have hovered for 6-8 minutes at a go during some flights and never had a problem like this

    Decent (its possible) but rarely in a hover
     
  13. John Shaw

    Joined:
    Mar 26, 2014
    Messages:
    198
    Likes Received:
    0
    Re: Is it possible to get a vortex ring state while hovering

    Some thoughts...
    I have never experienced a problem while hovering but I imagine it is possible.
    VRS is a law of physics type thing and therefore is not DJI's responsibility - therefore it is the pilots responsibility.
    You should always be aware of the wind direction and if your sinking move in the upwind direction.
    If your hovering in GPS mode and there is a breeze it should be no problem as the downwash is being blown away. In ATTI you will drift with the air mass and with your downwash which could be a problem.
    Be aware that if you increase the weight of the Phantom you are also increasing the downwash and the likelihood of encountering a VRS problem.
    I suspect the prop guards act a little like a ducted fan and make the downwash worse - just a suspicion.