Vortex Ring State in Quadcopter 'Drones'

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CharlieOneSix
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Vortex Ring State in Quadcopter 'Drones'

#1 Post by CharlieOneSix » Sat May 20, 2023 4:20 pm

I have a DJI Phantom 3 Advanced quadcopter 'drone' which has served me well for 7 years. I always knew there was potential - as there is of course in helicopters - for Vortex Ring State if I descended vertically too fast and then pulled in power. Today, with pleasant calm conditions and good visibility, for the first time ever I climbed to the maximum permitted 400ft AGL to do some area video overhead the house. When I finished I intended to land the drone but couldn't see the Phantom 3 too clearly in respect of its rate of vertical descent. I changed my mind and decided to do some more video and at about 300ft I pulled in power and re-established a hover.

That's when it went pear shaped. Although the gyro stabilised camera view on my linked iPad didn't show it to any extent, I could see that the Phantom 3 was rocking and falling out of the sky. Being a wise old helicopter pilot I didn't do what the uninformed would do, ie pull power which would make the situation even worse, but I put in full forward 'cyclic' and reduced power slightly. The Phantom recovered at about 50ft. If anyone was in doubt, you can certainly get into Vortex Ring State in quadcopter drones - including those with six or eight powerplants of course.

Many years ago I went up in a RN Wasp helicopter with an ETPS test pilot. At 8000ft he deliberately put the helicopter into full VRS. We recovered at 4000ft. A vivid demonstration!
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Re: Vortex Ring State in Quadcopter 'Drones'

#2 Post by OneHungLow » Sat May 20, 2023 6:54 pm

Very interesting post C16. Do you have recorded footage of the descent. I imagine the multiple rotors on the quadcopters would make for a complicated vortex state with the potential for a lateral upset as well if one, or more rotors, were slightly outside the vortex ring.

Have done some simulated Vortex Ring State recoveries, the most recent being just north of Rye at about 5000 feet in the R44 and it recovers quickly using the technique you used on the quadcopter, but clearly these weren't fully developed and apparently the aircraft descends very quickly if recovery is not initiated immediately. One thing to recover at altitude, another when descending too quickly at too low a speed near to terra firma. Was also interesting hovering the aircraft at 7000 feet, a little bit like balancing a pencil on the tip of one's finger.

I see that VRS recovery for drone pilots is covered here but I don't think much of their recovery advice.

https://www.propelrc.com/vortex-ring-st ... %20tornado.
For example, if your rotors are spinning at 1000 rpm, you should descend at a rate no faster than 500 feet per minute.

If you find yourself in a vortex ring state, you should first stop descending. You may need to increase power to maintain altitude, but stopping the descent as quickly as possible is important.

Once you have stopped descending, you can then start to recover by slowly flying out of the vortex. It is important to fly out of the vortex slowly, as sudden movements can worsen the situation.
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Re: Vortex Ring State in Quadcopter 'Drones'

#3 Post by OneHungLow » Sat May 20, 2023 8:22 pm



I wonder if the Vuichard Recovery Technique would work with a drone!
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Re: Vortex Ring State in Quadcopter 'Drones'

#4 Post by CharlieOneSix » Sat May 20, 2023 9:17 pm

Well I certainly disagree with the advice to drone pilots to pull in power if they get into VRS!! I’m surprised the guy in the video lost control as he didn’t seem to have much rate of descent but he certainly got some lateral shaking although not as much as in my incident.

I wasn’t filming during the descent, just monitoring the camera view on my iPad.
The helicopter pilots' mantra: If it hasn't gone wrong then it's just about to...
https://www.glenbervie-weather.org

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