I was recently asked to explain this to a couple of observers. I was able to back up my explanation with my own experience of this, but I haven't heard of anyone else suffering from it. Anyone prepared to share their experiences? P.S. We've heard the curry jokes!
[This message has been edited by Skycop (edited 12 July 1999).]
Hi there, Vortex ring is a state of power on flight if you like when you injest your own downwash,an amusing feeling I used to get when flaring downwind in an old Bell 47j Ranger many moons ago.Fortunatly,helicopters like the R22 are hard to vortex ring but that never stops me showing my students as if you try hard enough,you will find that they all will vortex ring given right conditions!!Bye the way,its hard to recover your rrpm from low altitude in big bladed machines when vortex ring occurs,this is because most of us mortals try and arrest the ROD with collective which only makes the situation worse!Hope this is of help.
Thanks for that. I am aware of its causes (ex beefer!) but I was rather hoping for some "war stories". One of mine is that I watched another pilot get us into it (despite my warning) while trying to hover at a large height at night - we lost 3000ft. I eventually helped out on the cyclic forward bit as he hesitated too long...
The only war story I ever heard about VR was from an old beefer who was instructing on the QHI course at cfs who said that he got it in a Whirlwind in Cyprus once and it took significant effort and height to get out of it. He was very high and in a hover (or was supposed to be) when he was distracted and then, when he noticed a v. high RoD, knee-jerked and pulled a load of pole.
He also used to tell the story of experiencing retreating blade stall in the same type (quite alarming by his account & I believe him). I used to think that he perhaps wasn't the best helo puke in the world but, as he was also an ex Lightning jock, he must have had something about him. Can't remember his name but only his nickname!
Vulture, I can confirm that RBS in a Whirly is spectacular, having been inadvertently been shown it at about 150ft agl during a "spirited" low level manoeuvre a good few years ago. Fortunately the undemanded violent roll brought the aircraft upright rather than inverted...
it is generally accepted that increased rotor tip vortex action is one factor in the development of vortex ring state, can anyone explain why this intensifies? My guesses are: increased AoA in the decent and/or increased interaction with previously shed vortices (also a result of the decent).
As the a/c continues to descend, the rate of descent flow increases which increases the AoA on the underside which increases drag which moves out more and more from root to tip which increases the vortices which feed the induced air flow on the upside which increases AoA which increases lift which increases drag which incresas the vortices which...then the ground spoils it all. The end.
I agree, it is a phenominal series of events that cause it and the biggest problem is that if you don't react it increases in intensity exponentially.
I'm not trying to preach to the choir, but something I learned many years ago has served me very well when trying to explain the recovery procedures.
If you remember back to your boy scout days when you were learning about fire you'll probably remember the term "The Fire Triangle" which required three things, Fuel, Heat and O2. Think of Vortex ring state as having a similar 'must have' triangle. It requires three things, take one away and it doesn't exist, they are ROD in excess of 500 fpm, High power setting and an airspeed below translational.
As in the fire triangle, if you take any of those items away, it no longer exists. I know this was a little off topic, but if any of the younger less experienced guys out there can benefit from it, well there you go.
My understanding is that "descending (or 'settling') with power" has always been the US description of what the UK terms vortex ring. We opted for the latter, I believe, because it implies something rather more urgent than the former.
True - it should have referred to something like 'rate of descent airflow'.