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Condition for Vortex Ring

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Condition for Vortex Ring

Old 29th Nov 2017, 09:34
  #121 (permalink)  
 
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Would now somebody please post what the CAA in its endless wisdom has to say about it. Just to get everybody on the same page here.
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Old 29th Nov 2017, 21:42
  #122 (permalink)  
 
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Originally Posted by Rotorbee View Post
Would now somebody please post what the CAA in its endless wisdom has to say about it. Just to get everybody on the same page here.
You took the time to research the Canadian one, why not put some effort in researching the CAA? seems to be in your neighborhood according to your avatar, CAA sure closer than TC.

JD
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Old 30th Nov 2017, 07:16
  #123 (permalink)  
 
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Well dear fijodor, how about you doing some research work? Bit lazy aren't we?

Seriously, don't you think I tried? Unfortunately the CAA of UK does not provide this information easily. If you search on the aforementioned site for SWP, it does not find anything and suggests to try "setting wing paper" which makes no sense at all to me and surprisingly does not find anything useful either. Therefore we need somebody who has at least an idea, where the CAA does hide this information or the books latest issue.

Satisfied?

BTW: Being closer to the UK than to Canada does not mean, that we understand their way of thinking better than yours. The Brits way of thinking is puzzling to the rest of the world.
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Old 30th Nov 2017, 11:51
  #124 (permalink)  
 
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I don't think the CAA actually address this issue with a 'handbook' or 'flying guide'.

There may be an advisory notice or a circular somewhere but I couldn't find it easily.

The British Helicopter Association have some guidance documents but nothing detailed on VRS or SWP.
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Old 30th Nov 2017, 15:06
  #125 (permalink)  
 
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SWP in the UK is partly a misnomer. SQUEP pilots (suitably qualified and experienced persons) know that SWP is a construct which is drilled into anyone who operates machinery over here: (Buses, cars, lawn mowers, planes, boats, helicopters). F = MA.
If you don't have sufficent F in your engine(s) to equal MA, you will crash! Simples. Basic law of physics. There is no need to exagerate or obfuscate over it.

VRS, I would suspect is more akin to being discussed in aerodynamics/flying manuals/teaching aids, not a CAP from the regulator.

TC is leaving the building.........................shall I switch the lights off now. Are we all done?
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Old 30th Nov 2017, 15:14
  #126 (permalink)  
 
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Pst ... is he gone?
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Old 30th Nov 2017, 15:33
  #127 (permalink)  

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Originally Posted by Rotorbee View Post
Well dear fijodor, how about you doing some research work? Bit lazy aren't we?

Seriously, don't you think I tried? Unfortunately the CAA of UK does not provide this information easily. If you search on the aforementioned site for SWP, it does not find anything and suggests to try "setting wing paper" which makes no sense at all to me and surprisingly does not find anything useful either. Therefore we need somebody who has at least an idea, where the CAA does hide this information or the books latest issue.

Satisfied?

BTW: Being closer to the UK than to Canada does not mean, that we understand their way of thinking better than yours. The Brits way of thinking is puzzling to the rest of the world.
Rotorbee, I put "CAA vortex ring" into my usual search engine box at the top of my browser and guess what happened? It came up at the top of the list.
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Old 30th Nov 2017, 15:38
  #128 (permalink)  
 
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Originally Posted by Rotorbee View Post
Well dear fijodor, how about you doing some research work? Bit lazy aren't we?

Seriously, don't you think I tried? Unfortunately the CAA of UK does not provide this information easily. If you search on the aforementioned site for SWP, it does not find anything and suggests to try "setting wing paper" which makes no sense at all to me and surprisingly does not find anything useful either. Therefore we need somebody who has at least an idea, where the CAA does hide this information or the books latest issue.

Satisfied?

BTW: Being closer to the UK than to Canada does not mean, that we understand their way of thinking better than yours. The Brits way of thinking is puzzling to the rest of the world.
No need to be so critical about TC describing what VRS and SWP are, at least TC and the FAA (describe and teach) are telling us to be careful about it, right or wrong in their definitions of it.
So far you seem to be the only one being insulted about it. Little sensitive aren't we?

Now you may not have noticed but i did research the subject in Canada and posted what TC had to say about it in this tread and I am thinking that you probably copied and pasted what I put here already instead of researching it.. Again Rotorbee why don't you put some effort in looking up VRS and SWP and telling us what YOUR Aviation Authority in YOUR country has to say about it, unless it is too complicated to get to it.

PPRuNe being an International Aviation forum why not get what other Aviation Authorities have to say about it. So far only Canada and the US has something to say on VRS/SWP (and they are being criticized about it)

I thought Canadians were so nice and polite?
Not all of us (sorry to vex your sensitivity)

JD
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Old 30th Nov 2017, 15:53
  #129 (permalink)  
 
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Shy - I just got a link to a CAA safety Sense leaflet which mentioned VRS but only briefly.
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Old 30th Nov 2017, 16:24
  #130 (permalink)  
 
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But that does provide a link to this
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Old 30th Nov 2017, 16:38
  #131 (permalink)  
 
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So far only Canada and the US has something to say on VRS/SWP
This is a very entertaining thread. It's a subject that just goes on giving... just when you think PPRuNe is getting boring, someone says the magic words "Vortex Ring" and off we go again. It's nearly as good as A vs B on the airline forums.

But seriously... why do people get so het up about the finer distinctions? As a low time heli pilot (but I think I'd feel exactly the same if I had 10,000 hours) I know what I need to: don't go there. Keep your descent rate low when flying slow, and if you're HOGE and don't have the power to hold altitude, get the h*ll out.

As for true fully developed VRS - why would anyone ever, ever, ever go there? From what I've read here, it sounds truly terrifying, far worse than a FW spin, which does even have its uses. I wonder for every person who writes a tale of "I started at 10,000 feet, and when I recovered I could count the flies on the cows" how many people didn't recover in time and ended up splatted on the ground? For sure I don't want to find out first hand.

So is there more we need to know than Just Don't?

(I know it's different for long line and mountain rescue and such, but that's a whole separate speciality. I guess just easing in a bit of forward cyclic isn't such a great idea if the effect is to knock half a dozen people off the roof of the building with the A/C unit you're supposed to be putting there).
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Old 30th Nov 2017, 20:01
  #132 (permalink)  
 
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96S, it's because most helicopter pilots are pedantic morons who love to argue over the stupidest of things. Get two helicopter pilots together in a room, and (if you're not one of them) you might come away not knowing exactly *what* colour the sky is - because the other two will argue about it interminably. Ho-lee crap.

"It's cyan!"
"It's azure!"

It's friggin' BLUE, boys.

As I've said...as I've always said...these issues with descending vertically into your own downwash only happen down low at the bottom of a f'ed-up approach. It probably won't matter what technique you use to get out of it, but if you've waited too long to figure it out then it's not going to matter and you're probably going to crash the ship.

The stupidest of the stupid are the ones who claim that you can, in your heavy helicopter, make a fast approach, do a big flare at the bottom, then fall through and hit the ground hard and then call it SWP. Oh. My. God. But yet there they are.

There is an infamous video of a U.S. Navy CH-46 doing a very shallow, very fast approach to the aft landing pad of some helicopter carrier/boat/ship. The pilot misjudges things a bit and gets one wheel stuck in the fencing just short of the deck. The helicopter stops, but the ship keeps moving forward. Guess what? Before you know it, over she goes! Backwards into the water. And somebody in this very thread called it a "settling with power" accident.

Yeah. Uh-huh. Right.

You, 96S will find, as you go through your career, that some people who claim to know a lot about how helicopters fly really do not. They'll quote you textbook upon textbook as proof. (There are even those who claim that the advancing blade of a rotor in forward flight flaps *up*! Amazing. But that's a different subject.) Everybody is an expert on the internet! Am I? Pfft, hell no. But I do know not to come in vertically (or even below ETL). On a no-wind day. In a heavy helicopter.
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Old 30th Nov 2017, 21:54
  #133 (permalink)  
 
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The stupidest of the stupid are the ones who claim that you can, in your heavy helicopter, make a fast approach, do a big flare at the bottom, then fall through and hit the ground hard and then call it SWP. Oh. My. God. But yet there they are.
No-one has called that SWP so I'm not sure what your point is.

I agree that CH46 isn't SWP, it is just a punchy arrival gone wrong when the wheel gets caught - sadly people died in that one.

(There are even those who claim that the advancing blade of a rotor in forward flight flaps *up*! Amazing. But that's a different subject.) Everybody is an expert on the internet!
it tries to but is prevented by the pilot input on the cyclic or the autopilot moving the actuators. Take a helicopter, trimmed to a 90 kt cruise - then add another 30 kts of wind without doing anything else to the controls - what happens???? Flapback, so which way is the advancing blade flapping????? Then you push the cyclic forward to compensate and that makes the blade flap down instead.
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Old 30th Nov 2017, 22:07
  #134 (permalink)  
 
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Originally Posted by FH1100 Pilot View Post
...these issues with descending vertically into your own downwash only happen down low at the bottom of a f'ed-up approach.
Then I guess You've never done any hoisting at 100-200-300feet or higher in mountainous terrain with bad vertical references.
It's more than f... up aproaches that might lead You into that (vrs)
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Old 1st Dec 2017, 06:16
  #135 (permalink)  
 
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Shy,
the results of a search depends of a lot of things, search engine, localisation, cockies, browsing history and many more. My search results are certainly different than yours and I can not find anything useful on the CAA site.

Robbo Jock,
the link is dead for me (server not available) and points to an eurocontrol site for registered users. That would not be the UK CAA then.

Fijodor: Sensitive? Not at all. I think it is funny. I just find the wording amazing, as if the author was really annoyed with the rest of world not understanding the difference between VRS and SWP. But I believe, that this is inappropriate for a training manual. Just imagine a class where one student came from the US and uses SWP. For the rest of the class he would be the uninformed one. That's counter-productive in a training environment.

Here they call it VRS with a hint that SWP is a synonym. That's what EASA land does. But if you haven't realised by now, I am FAA trained. I am one of the "uniformed" ones, but do understand the difference between VRS and SWP as the Canadians use it. I just don't think that insisting stubbornly on one definition is constructive, when the rest of world sees it (due to practical reasons, not logic) as a synonym. And I believe, this is also the FAA's view.

What it boils down to is, that everybody understand the term VRS, no problem there (even the uninformed ones, after all it is in the FAA training manual). What all the fuss is about is, that SWP is either used as the "not enough power left" or as a synonym for VRS. Apart from the Canadians, it looks like no aviation authority uses SWP other than as the synonym. Therefore no official training manual will contain it. To the big dismay of the Canadians and some Brits, this will result in a lot of young pilots trained as half uninformed ones (half wits if you want). Does it matter? I don't think so, as long as they know, what is going on, how to avoid it and how to get out.

I personally find the thread highly entertaining. It started on how to get into SWP/VRS and instead of being an aerodynamic or power availability discussion, we can't even agree on the terms to use. Nick Lappos tried it years ago, suggesting that we on PPRuNe just agree on one term - VRS preferably - and move on. Well ...
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Old 1st Dec 2017, 07:57
  #136 (permalink)  
 
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But if it makes just one pilot think about hover performance or operating conditions and what he is trying to do with the helicopter and prevents a mishap (or worse) then it makes all the discussion (most of it quite civilised) worthwhile.
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Old 1st Dec 2017, 08:56
  #137 (permalink)  
 
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Sorry about the broken link. After a bit of experimentation, I think the page is generated when clicking through to it, so won't exist for anyone else. Strange way of going about things, but there y'go.
Try this link then scroll down to Vortex Ring (under 2010). It's a UK Aeronautical Information Circular, Pink 020/2010
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Old 1st Dec 2017, 09:14
  #138 (permalink)  

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Rotorbee, one thing is for certain, I'm sure my "cockie" is different to yours. But from your last reply I'm not sure if you're uniformed or uninformed.

I have no axe to grind either way on this subject (life's too short to get my undies in a bunch about it) which is why I wrote my initial post (#2) on this thread.

But my thoughts; how about:

The approaching IGE situation.
1: "Under pitching" = not pulling enough power early enough to arrest a high ROD at very low IAS near the ground.
2: SWP= following situation 1, you pull to all the power you've got, too late - you keep on going down!
3: Over pitching = what follows from 2. No more engine power, but you can't stop your left hand from pulling pitch!

The OGE situation.
1: Under pitching = as per 1 above, but OGE.
2: SWP / IVRS. As per 2 above, but you don't have the visual cues and the ROD builds. The airflow through the disc begins to recirculate but you could fly away because you still have good cyclic response (Vuichard technique might work here). Call it IVRS if you prefer.
3: Fully developed VRS. Use whatever technique you like to regain some forward speed to stop the recirculation, but you are going to lose a lot of altitude because you no longer have good cyclic response, the aircraft will be pitching and rolling all by itself and your ROD will be higher than you've ever seen before. You can forget all about a recovery in "20 to 30 feet" as I read in an article about the Vuichard technique!
Most helicopters are rigged with more pitch control than roll control. We Brits prefer to use forward cyclic, and lots of it.

I'm off to work very soon (late shift today) so can't participate further. Obviously, as usual I'll be avoiding situation 1 above so the subject won't crop up in practice.
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Old 1st Dec 2017, 09:31
  #139 (permalink)  
 
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I could not agree more, but we have also to think about the common student pilot who does not have (yet) the background needed to understand the fine differences.
We as FIs can not prepare them for every possible situation they will find themselves in. We provide them with a limited set of tools to manage the most common types of problems.

We use tons of "Lies to children" in the teaching process, just not to overwhelm the learner. For example: Everybody learns about Bernoulli for their PPL, but this is just part of the equation. But do we want student pilots to solve the Navier-Stokes-Equations?
Hell, no! Just conservation of momentum, mass and energy will be too much for many, FI's included.
While we all agree that VRS is the right word and SWP should be used in another context, reality is unfortunately different. During the teaching process we can use one tool to get out of both of it. In both cases reaching ETL will solve the problem. If we now use Vuichard (we have thread for that, don't start it, it is just the example closest to it) in on situation where you have enough space to the side to use it and forward stick in a case if not and forward stick in a not enough power situation but only if ... - you probably get my point by now - we probably do more harm then good. Too many "if's" are bad.

While I absolutely love the banter here and chip in whenever I can, the really fruitless discussion about who uses the right words does not provide any insight for the newbie. I see no harm in using both terms, as long as everybody knows what we are talking about.

Or we just should set SWP on the list of forbidden words. That's a thought.
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Old 1st Dec 2017, 09:34
  #140 (permalink)  
 
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1. UNITED KINGDOM AERONAUTICAL INFORMATION CIRCULAR
AIC: P 020/2010 20-MAY-2010

Safety

VORTEX RING.
NATS Ltd UK Aeronautical Information Service Heathrow House Bath Road Hounslow, Middlesex TW5 9AT

1.1 Introduction
The following paragraphs are a reminder to helicopter pilots of the ever present danger and insidious nature of vortex ring.
The usual American term for this condition is 'power settling', a description that sums up the potential predicament for the unwary pilot.
2 The Vortex Ring State
2.1 Vortex ring state is a phenomenon that occurs when the main rotor tip vortices are recycled into the induced airflow. This state
can exist when the vertical rate of descent is greater than half the air velocity induced by the rotor and is normally experienced at low
forward speeds and significant rates of descent. The effect of this is to produce severe instability of the airflow around the rotor disk
with subsequent aerodynamic inefficiencies and loss of rotor thrust.
2.2 Many modern helicopters with high disc loading (high induced flow) will require a relatively high rate of descent before the possibility of vortex ring exists and it may be this factor, combined with greater amounts of power generally available today, that has led to a view that modern helicopters do not develop vortex ring. This is not the case and whilst it can be difficult to induce vortex ring deliberately, the possibility of a vortex ring occurrence always exists if the helicopter is operated in the relevant flight conditions.
3 Conditions for Entry
3.1 Vortex ring becomes a possibility when the airspeed is below about 30 kts, with a rate of descent greater than 300 fpm and with
power applied. This can be a very unpredictable process so there may be occasions when, operating beyond these conditions, vortex
ring is not encountered. However, the greater the time spent within these conditions, the greater is the chance of encountering the
problem. The inaccuracy of helicopter airspeed indications at low airspeeds should also be considered and allowed for, particularly
when operating out of wind or with a rate of descent.
4 Symptoms
4.1 The symptoms of vortex ring are typically:
(a). The Incipient Stage:
i. Increased vibration and buffet;
ii. The onset of small amplitude 'twitches' in roll and yaw;
iii. Longitudinal, lateral and directional instability.

(b). The Established Stage:
i. A very rapid build up in rate of descent which can exceed 3000 fpm;
ii. Reduced effectiveness of cyclic inputs in roll or pitch; and
iii. Application of collective pitch having no effect in reducing the rate of descent (possibly increasing it).

4.2
It is possible to pass through the incipient stage very quickly; the warning cues for the pilot may not be obvious. A fully developed
vortex ring state may therefore result with very little warning; especially at night, in poor visibility or at high altitude when visual cues are
absent. Even when the vortex ring state is fully developed the flight can be very smooth with little or no increase in vibration; the only real
clue being the sudden indication of a very high rate of descent.

5 Recovery
5.1 The Incipient Stage
5.1.1
As soon as the incipient stage is recognised, immediate recovery action must be taken. This is best attempted by maintaining
the collective position and applying forward cyclic to achieve a nose down attitude, in order to increase airspeed without delay. More
power can be applied if required as soon as steadily increasing airspeed is indicated - it is not necessary to wait for the best rate of
climb speed. The effectiveness of the incipient stage recovery must be carefully monitored and more positive action taken, as described below, if any signs of slow recovery or established vortex ring become apparent.
5.2 The Established Stage
5.2.1
In order to recover from established vortex ring, the flow state around the rotor must be changed in some way. Application of forward
cyclic should increase airspeed but it must be borne in mind that a large amount of cyclic may be required and held for several seconds
before a significant pitch attitude and speed change is achieved. It may be necessary to reach a large nose down attitude to obtain positive
airspeed. Lowering the collective to reduce power towards auto-rotation is also effective, but forward airspeed must be gained before power
is reapplied during recovery. Both methods will result in an inevitably large height loss. The best technique for recovery is to combine both
actions positively, then reapply power when steadily increasing airspeed indications are regained. It is not necessary to wait for best rate of
climb speed before adding power.
6 Applicability
6.1 All helicopters are susceptible to vortex ring and all helicopters suffer from unreliable airspeed indications when operating below
about 30 kts. Flight at low airspeeds, particularly with poor visual cues, must be treated with caution because it only requires a relatively small increase in the rate of descent for there to be a significant probability of vortex ring development.
6.2 Vortex ring can occur at any height above the ground cushion.
6.3 At typical helicopter operating heights, particularly during photographic and surveillance tasks or during steep or vertical approaches, the conditions referred to in paragraph 3 must be avoided since lack of height will make recovery from the condition uncertain. Pilots should therefore always maintain airspeed when turning or descending in high wind conditions. Pilots should therefore always maintain airspeed when turning or descending and especially when downwind in high wind conditions


http://www.ead.eurocontrol.int/eadba...2010-05-20.pdf

Last edited by Thomas coupling; 1st Dec 2017 at 09:46.
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