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  1. FlushVision

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    Recently, I've seen some instances where pilots have reported that their UAVs have fallen from the sky for no apparent reason. And that got me thinking...

    I was wondering if some of these instances are really the result of VRS (Vortex Ring State).

    This is a phenomenon that the more experienced UAV pilot will be familiar with, but I wonder if some of the newer pilots on this forum are aware of it.

    I'm not going to explain it...I'll leave that to a video from Simon Newton for explanation and how to avoid it.
    The following video makes heavy reference to quadcopters but the principle is the same for a Hex or any rotor aircraft.
     
    Robert Brooks and mcbutler like this.
  2. mcbutler

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    Very interesting, thank you,
     
  3. FlushVision

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    Probably the best way to avoid VRS is always to have some lateral movement from your right stick into the wind when on a descent and on a still day (no wind) descend in a cork-screw pattern.
    Even the professionals sometimes are victims of VRS as this video shows:
     
  4. PatR

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    Highly unlikely VRS had anything to do with the system failure events. Our multirotors use bi-directional offset propulsion methods which largely negate the airflow disturbance created by a single direction rotor head that promote VRS.
     
  5. samsflite

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    Plus also the manufacturers test and test this sort of thing and then limit the descent speed to painfully slow to stop it happening.
    Interesting theory though, and things do get out of hand very quickly with VRS, but I think the majority of 'fall out of sky issues' have been not connecting the battery properly, over-discharge of the LiPo until it falls off the cliff and everything just browns out. I think I've read of one where Yuneec confirmed it was power distribution board failure.
     
  6. FlushVision

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    I agree. All too often the root cause of a unit doing the death plummet is down to not making sure the battery is 'clicked' into place, and folks taking their batteries too low. I just put forward the issue of VRS as something to consider.
    One thing that's for sure: although the wizardry contained within the TH is impressive, it's not perfect...nothing is!