Did I get myself into Vortex Ring State?

[JulesTEO]

In addition to the documented footage from this event, here's another video including the aircraft's POV.

The audio on this clip was recorded from the aircraft

Greetings!

 

[FlushVision]

Just for discussion purposes, I have platforms where throttle control is completely different from consumer drones. Bottom stick = low idle RPM, mid stick = hover, anything above middle is climb, with rate dependent upon aircraft weight.

Previous experience has shown that reduction of throttle from a high hover would permit the aircraft to descend at a speed commensurate with throttle reduction, which could be quite fast. The more throttle was reduced the more “wobbly” the aircraft became. However, with enough reduction of throttle the aircraft would enter a momentary unstabilized free fall before rolling inverted into an uncontrolled descent. If allowed to continue a crash was assured. If enough altitude was present, resuming full throttle would cause the FC to right the aircraft and resume controlled flight.

Those experiments are why I don’t believe multirotors experience actual VRS. What I know happens is that not enough current is being provided to the motors to effectively stabilize the aircraft, with the “wobbles” caused by motors provided only enough current to attempt stabilization, but lacking adequate current the motors induce destabilization as they cannot generate enough thrust to compensate for the weight of the aircraft. As one corner drops it is provided current to lift it back up but a shortage of total available current causes opposing motors to end up in a current shunt, starting the cycle all over again. The FC ends up fighting itself in see saw trying to provide current it is being denied through throttle position.

That’s my story and I’m sticking to it

That's a pretty good argument. While I still disagree with you regarding the ability of a multirotors to enter VRS...I think they can in extreme and now fairly rare circumstances...I do see what you are saying and agree that a good proportion of 'untimely' descents can be attributed to what you describe. So, while I say that VRS can be achieved in a multirotor, I agree that we must not be convinced that all apparent VRS events are, well, VRS events.

At first, looking at Jules video, I was of the opinion that the aircraft entered into VRS after it's initial loss of the ability to fly. I changed my mind after a second closer look.

 

[PatR]

I think Jules put the right name on the second video. IMO it stalled. It reminded me of some old textbook stuff describing how an aircraft can stall at any airspeed and and any attitude if angle of attack is exceeded.

Just for giggles, the 920 does exactly the same thing as his H under the same conditions. Somewhat greater pucker factor though.