Vortex Ring Advise?

[skullcap]

RH;

Been there too and on the left seat, downflow can be very dangerous and unpredicatable, but to avoid it is only necessary when you have too, pretty hard to do most days when the wind is blowing and there is something,somebody to get and best know how to do it. Have to keep the back door open, take your time, don't commit til proven otherwise that you can get there and back. Can't count how many times have landed in the east facing cirque on flat bit of ground, in downflow, smooth, 7300', 2 people on board, 50 gals gas, 95% Q to hover 6 inches. Yeah, not much fun but is doable(that a word?).

VR;

Strongs winds either side better have your attention, better not stick your tail to the wind in upflow unless you gotta place to run when your cyclic goes full aft, even when a line goes thru the middle of a cirque, which is just not supposed to happen eh, KW?

VX;

As I mentioned, I haven't tried it but know many who have and do and it works. The key is to not pull more power to aggrevate the VR state, thus a high rate of descent does not build and the ground cushion helps dissipate the VR's. And only works in flat terrain and is not recommended by me. I still hold true to reduce power if able, fly away, if you have a heavy load on line and are unable to reduce power you may have to punch the load if you can't fly it in.

Spookiest thing had happen was entering VR state in turn, was turning into wind(30-35kts) halfway thru turn pulled power and a/c fell like stone, landed with 100% Q 200 feet back of intended lz. When analyzing situation realized that the a/s had fallen but thought big deal, am turning into wind. The wind died down while in turn which was then a skid, upflowing air thru rotor disc, low a/s, and power=bad sh#t. Moral=always have a/s thru turn, period. Only other alternative is to keep disc flat and let wind blow you round the turn with pedals, many drill pilots do it, not good for dealing with an emergency though but gotta do what works sometimes. Flat disc in most situations saves your but I like airspeed for quick turn arounds even though it is sometimes slower than drifting downwind, as VR says, personal preference.

sc

 

[skullcap]

And another thing, ha. The best bet is to know how to stay out like VX says, my thanks go to Kieth Veroni, whereever you are Kieth thanks. Without him demonstrating it, well the first time it happened to me after would have been ugly. Was on 150 line empty, staring down the hole of an Astar line was 50 above the ground, bingo, pushed forward stopped, looked back down and the line was coiled on the ground 50', so lost 100' in a blink of an eye.

sc

 

[Skids Up]

From many a manual; You need 300-1500(transport says 500-1500, military says 300 1500 and believe that number is more accurate) fpm rate of descent, low airspeed <20, and POWER applied, have been in vortex ring many a time with no sling load and little power, is all a ratio to how high the rate of descent is.

Sometime when you have LOTS of height, from level height, reduce power to around 40% TQ (jetbox is where I was shown) and cyclic back to maintain your height. As you speed aproaches zero center the cyclic, pull in some power, and hang on.

It will shudder a bit, and if your are stopped, and continue to pull power in, (nothing rapid) it will fall out from under you. :blink: Cyclic will be sloppy in all quadrants and to recover, down collective a bit, and cyclic forward or sideways and it will fly out.

I had been flying for 20 years before anyone showed this to me. Its a good demo of what it feels like. We were quickly in about a 3000 fpm desent.

Enjoy the other comments - good advice

 

[VERTICAL REF]

A real nice cream puff astar tried that flat land technique once, and ended up quite flat itself I do believe. YHT was her name... :huh: Have not seen her since?


Skully,
You are correct. A good/experienced/professional/competent (what ever you want to call it) mountain pilot always has a backdoor or two left open. Knows how to play both sides of the rock and has those days when man and machine have both reached their limits and the rock wins!

 

[downwash]

Just to be clear, there are quite a few references to 'low airspeed' in here, but I'm sure everyone realizes that it's really a matter of being without translational lift. Great input from VR, VX and skullcap, though.

There are, friends, various of reasons for not experiencing Vortex Ring early in one's career. Hopefully, most instructors, if not prepared to demonstrate the phenomenon, will explain it well enough (plant enough fear?) that most new pilots will be able to avoid it until they get far enough along to have it demonstrated, voluntarily or otherwise (unless, of course, the instructor believes you need a higher rate of descent than 300 fpm, in which case, come along with me while I show you). I, for one, had over 2,000 hours before I got off Hiller 12E's, on which the 'paddle' system controlling cyclic pitch, when in VR, was too ineffective to get you out to 'clean' air. I then had some great involuntary experiences in Bell 47's and ground effect did make the difference, in a lot of cases.

 

[skullcap]

VR;

That a/c had a bleed valve tach box failure, this was not detected for two years due to everyone thinking that the pilot had vortex ring. The truth came out when the company which bought the wreck went to overhaul the tach box and found that a diode had burnt out. If the driver had had some gauges in the floor he would have be able to tell that the bleed valve had not closed and topped the engine which caused the low rotor problem. He thought that his engine had failed like had happened not too long before to a sister ship, lowered collective and pulled at the bottom, walked away sans helicopter. Shoulder harness and helmet saved his life, floor of cabin buckled, cabin roof broke open, was not pretty. His story was true and no one would believe him, I did because I was there to do the investigation, he had dropped one of the bags already and was heading off to drop another when the rotor rpm decayed, pretty hard to get into VR state on takeoff over flat terrain. The bags were all on top of each other but there was one that was not hooked to carousel and under all the rest, showing that infact he had released one bag. Kodiak data showed average rate of descent on final to be under 300 fpm as well. Seemed like no brainer to me but the investigation was dropped as was easier and cheaper to blame the pilot for VR state. Lesson-do not stop the investigation unless you are COMPLETELY satisfied with the results.

sc

 

[VERTICAL REF]

It is good to finally hear the accurate data there Skully! All these years the experts were dictating Vring! As per the other topic - maybe our TSB investigations need to be more through and processed a little faster to get need to know info out to the rest of the operaters for a life saving, insurance reducing benifit to all involved! They are short staffed as we all are but maybe this is where Ottawa shoud put in some extra effort!

 

[cap]

Keep the disc loaded on approach and keep it under 500fpm. If you don't....wellll "it's a long alley without trash cans". Allouettes II & III will tell you before you get into VR unless you are legally deaf.........Bells don't.

 

[Winnie]

OK,
My input on how to get into it:
Fly into wind at HIGH height (2000-3000 AGL), slow down, with slight power on, when about 30 KIAS turn downwind and watch yourself go down! You don't need to actively slow down any, as the turn will do that for you, and when you are downwind, you WILL go down (if you have any wind at all). Its out of Shawn Coyle's book, Cyclic and Collective.

It works! Almost scared the #### outa' me! 😀

 

[skullcap]

There is another scenario to watch for, sometimes in seismic you are required to move equipment downwind, not an issue for the astar but have heard that if the wind is strong and can push your vortices ahead of the aircraft and you settle into them the vortex ring state that you enter is extremely fast and violent. Have never had the pleasure but know some who have and say that normal VR state is a gentle #### cat compared and you slow WAY down after that.



sc

 

[dammyneckhurts]

Skully.....I have had that happen in a 407.... had my head up my ass, moving from one line to another, about to overfly the first drop. Did a tight 180 degree turn with lots of peddle so's not to loose sight of the flag and did a flat "skid" of sorts. (the flight path was level, disk was tilted) It was very sudden, definatly not a downwind/mushing lack of power kinda thing. That was the first and last time for that one! I was a bit downwind when I started the turn ..(it was off my 7 or 8:00 I think)...still not sure if it was because I had air coming in through the top of the disk (downflow) or if I was skidding enough to have air effectivly hitting me from below (upflow)

DMNH

 

[downwash]

Probably doesn't need repeating but, like so many phenomena we deal with on a daily basis, know how to RECOGNIZE it, BE PREPARED for it, and KNOW HOW to deal with it. That's how we get to tell more stories. B)

 

[flying monkey]

Anyone ever get into it in an S76? Shudder and twitchy tail?

I've heard it is not very good for the airframe.

cheers

 

[Rotorhead]

Anyone ever get into it in an S76?

Part of my training at Helijet included a demonstration of vortex ring state, at night over the water between Boundary Bay and the Gulf Islands. Scared the crap out of me.

The night autos in Abbotsford were fun in comparison.

RH

 

[Harmonic_Vibe]

That a/c had a bleed valve tach box failure, this was not detected for two years due to everyone thinking that the pilot had vortex ring.

His story was true and no one would believe him, I did because I was there to do the investigation.

Lesson-do not stop the investigation unless you are COMPLETELY satisfied with the results.

sc

I don't think it's quite true that no one believed his story. There were certain elements that didn't make sense but I believed that something had gone wrong. As you may recall SC, I convinced that former Royal Navy insurance investigator of that fact (you remember the guy...his name was Ian but FN kept introducing him to everyone as "John"...at which time Ian would produce a card that said "Ian" in large letters...but FN failed to notice this...that was repeated at least 10 times over 2 days...and then, finally, Ian was walking down the hall with FN chasing him yelling "John! John!" CU and I couldn't stop laughing).
It was the input of Bob Waldron and the acquiesence of the parent company (which simply wanted the cheque...of course the company entered bankruptcy protection within a couple of days of this incident) that resulted in a "Pilot Error - Case Closed" situation. The final report I wrote specifically denied the possibility of Vortex Ring...so I'm not quite sure who you think should have kept investigating (you've hurt my feeling slightly). When they told me the engine "ran fine" in the test cell, as if that was a surprise, I knew no one was listening. The engine was "running fine" on the ground and had to be shut down by the pilot...so where's the surprise that it ran in the test cell? You may also recall that I told you last year that I was theorizing it was the bleed valve and that's when you told me about the diode in the tach box...but, to paraphrase Sherlock Holmes, "have you considered the dog barking in the night Watson?"

As for Vortex Ring in general, there is an excellent thread on this subject on PPRUNE. The input of Nick Lappos and Shawn Coyle is spectacular. They are in agreement, for instance, in denying the possibility (or at least the "likelihood") of entering VR at a low rate of descent such as 300 fpm. Although I don't agree with everything they say (some of it seems contrary to my personal experience)...the raw data is excellent. Many pilots do not know that VRS begins near the mast. When the induced downward velocity of air through the disc is exceeded by "upflowing" air (whether from a ROD or from "upflow"), the air begins to recirculate. This explains why a "light" helicopter does, in fact, get into VRS more easily than a "heavy" one (at least that has been my experience with 500's and Astars). Windtunnel tests (I have read the results...I don't have any personal involvement in that kind of thing) have shown that in all cases of VRS the mainrotor continues to produce lift. BUT, when the air through the centre of the disc stalls out a portion from the mast to outboard, and this combines with the ever-present "Wingtip Vortices", there (in most cases) isn't sufficient lift to support the weight of the helicopter. This also explains why a light, falling helicopter stops, almost magically, in a low hover...if you're lucky enough to have a nice, flat spot under you that is! Not for the squeamish in any case...and I'm way too squeamish.

HV