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HeliboyDreamer
18th Nov 2017, 10:57
I have recently read an article mentioning that vortex is likely to occur around lower than 30kt and more that 500ft/min decent.

As far as remember from school I have been told lower than 20kt and more that 300ft/min decent.

1) Who is right ?
2) I guess those figures will vary depending on aircraft, right?
3) Is there any aircraft out there that has a vortex warning light based on any combination of parameters stated above?

For the 3rd question I specially have in mind the Puma accident in the north sea a few years ago where such a warning light would have been usefull.

ShyTorque
18th Nov 2017, 11:09
This subject comes up very often.
I politely suggest you use the search facility on the yellow bar at the top of the page because almost everyone here has discussed it (and argued about it) many times.

HeliboyDreamer
18th Nov 2017, 11:49
I ran a search vortex previously and didn't find specific post I will run it again and look more carefully, thanks

Edit: indeed I have used the advanced search this time on rotorhead only and found a few posts. Hopelly some will answer my questions

paco
18th Nov 2017, 14:42
The original 30 kts/300 fpm was for when helicopters were very light in weight and had very little downwash, but nowadays I believe the CAA would expect to see 400 ft per minute. It is in fact a safety margin - in reality you would need to be inside ETL (around 12 knots) where the downwash stays more or less within the rotor disc.

The figures for rate of descent will vary with the aircraft, but the heavier it is, the less likely you will get into VR because you will need to go down faster to catch up with the downwash.

Never heard of a warning light for VR..... Is that like the red light that comes on when the engine falls off a DC 10? :)

Phil

ethicalconundrum
18th Nov 2017, 14:43
OK, it's been a long, long, long time since I've had to work with this. The answer to your questions is 'it depends'. There are multiple independent variables(height of disk above surface, dia of disk to height, cabin size/shape, mass, and mass moments, etc) and also a number of dependent variables. One cannot use a fixed number for all shapes.

Lucky, there is a calculator for all that stuff, and damned if I can remember the name of it but something like Kutte-Jukowitz(?) formula. It's a derivative of the above variables which will predict the potential for things like ring-vortex state. You can find it in some obscure aerodynamic texts from the 50s and 60s. Maybe also now on one of those software packages for finite element analysis.

Also, while it's not that important to know the speed or descent rate, what's important is to recognize it and implement recovery very quickly. For US built rotorcraft I prefer hard right pedal, right cyclic. For the backward crowd from Yerrup rotorcraft, I would presume hard left pedal, left cycle, but that is only theory as I have no time in the backward spinning machines. Of course, if there are path obstructions preventing that 'out' you better have something figured out before things get out of hand. Rarely fatal, but it will turn a collection of spare parts, all operating in close formation to a collection of expensive metals being flung out at remarkable speed and distance.

MightyGem
18th Nov 2017, 20:44
Here are a few Threads/Topics on the subject. Should occupy you through the long dark winter.
http://www.pprune.org/rotorheads/600813-vortex-ring.html?highlight=vortex+ring

http://www.pprune.org/rotorheads/557861-vuichard-technique-settling-power.html?highlight=vortex+ring

http://www.pprune.org/rotorheads/595532-best-approach-speed-techniques-avoid-vortex-ring-condition.html?highlight=vortex+ring

http://www.pprune.org/rotorheads/592404-settling-power.html?highlight=vortex+ring

http://www.pprune.org/rotorheads/574962-vortex-ring-autorotation.html?highlight=vortex+ring

http://www.pprune.org/rotorheads/116124-vortex-ring-settling-power-merged.html?highlight=vortex+ring

n5296s
18th Nov 2017, 22:58
Oh yippee! Another vortex ring thread just when things seemed to be getting quiet! OP, no this has never ever been discussed before. Well, not in the last week or so anyway.

gulliBell
19th Nov 2017, 03:33
Almost invariably when helicopters are put in vortex ring state the pilot has been unaware of the wind, or airspeed, or rate of descent, or power settings at the time. So the question really only holds academic merit, and as others have pointed out, that discussion has been widely discussed before.

Agile
19th Nov 2017, 05:47
I concur with the idea of GulliBell, the question has academic merit mostly, because:

My impression, its hard to enter Vortex ring you have to be looking for it, and even still before it happens, you get so much vibrations and uneasy feeling that any normal pilot would wake up look at the instruments and make the proper correction.

if you know where the wind come from, keep your airspeed in the green, don't go crazy on your rate of descent and add bunch of power to fix it. it does not matter 300 or 500ft per minute, you are nowhere close.

gulliBell
19th Nov 2017, 07:06
@Agile is correct. When teaching/demonstrating Vortex ring recovery - settling with power - or whatever you wish to call it, you need to concentrate and physically fly the helicopter and establish the necessary parameters to demonstrate the manoeuvre. The helicopter gives you clues it is not happy doing what you are asking it to do. So pilots who inadvertently enter vortex ring state are more than likely not concentrating on things they should be concentrating on immediately before entering this predicament. And when I hear excuses from pilots who pancake their helicopter in the steaming swamp late on a sunny afternoon when doing a low level pipeline inspection, and then blame it on an autopilot malfunction, yeah right, what a load of bollocks.
The big thing is, when you are low and slow in a helicopter, it is critical to know where the wind is coming from. Whether vortex ring state onset happens at 30/20/10 knots or 100/200/300 ROD or in any combination of parameters, knowing those parameters is secondary to knowing where the wind is coming from, concentrating on the job at hand, and listening to the helicopter if it starts to complain about what you are asking it to do.

And @paco, I highly respect your experience, but I'd need to think about that explanation about being heavier is less likely to result in VR. I'm inclined to disagree with you on that one. At the training weights we work in I'd need to feel a little braver - or higher - about being heavier before experimenting with that one.

paco
19th Nov 2017, 07:21
In theory - if you are heavier, you need more downwash, and it's more difficult to get the vertical speed to catch up with it, but I agree with you, it's not always true. I remember when we used to do base checks at 95% all up weight. I still think it's a good idea.

Phil

BOBAKAT
19th Nov 2017, 08:37
The worst place to go in "VRS, is when you make a "vertical approach" in a small/confined area : You don't have any escape if the Vortex Happen
You have to be really aware at your rate of descent all time, but with a low flying speed : Above 300 ft/min, you enter in the Vortex zone, under 300 ft/min, no problem....So if in "ANY " case you maintain your rate of descent below 300 ft/min, you never risq to go in VRS..

gulliBell
19th Nov 2017, 09:48
In theory - if you are heavier, you need more downwash, and it's more difficult to get the vertical speed to catch up with it, but I agree with you..


I've got a hunch the accident stats will probably show that prangs where VR was the cause is more common where the helicopter is well below MAUW. If so I'd put that down to pilots probably being more vigilant of their performance parameters when slow and heavy, and thus less likely to being caught out unaware of a flight condition exposing them to VR onset. Rather than the opposite case, when light they are probably less inclined to monitor their performance numbers.

I don't agree yet that being at a heavier AUW puts you less at risk of VR onset for aerodynamic reasons. With a higher angle of attack on the rotor blades the pressure difference between the top side and the bottom side of the rotor disc is greater; the high pressure side air is more prone to want to escape around the rotor tips to the low pressure side, and thus establishing a vortex ring which quickly deepens towards the blade root. As this happens the equation of lift vs gravity rapidly goes in the direction of gravity.

gulliBell
19th Nov 2017, 09:54
The worst place to go in "VRS, is when you make a "vertical approach" in a small/confined area : You don't have any escape if the Vortex Happen....

Speaking from experience, I can think of worse places. Like on a pitch black night over a pitch black sea when all of a sudden there is salt spray all over the windscreen. It sure gets your attention, even with the enormity of the open space around you.

paco
19th Nov 2017, 16:16
"I've got a hunch the accident stats will probably show that prangs where VR was the cause is more common where the helicopter is well below MAUW."

Exactly!

BOBAKAT
20th Nov 2017, 02:31
Speaking from experience, I can think of worse places. Like on a pitch black night over a pitch black sea when all of a sudden there is salt spray all over the windscreen. It sure gets your attention, even with the enormity of the open space around you.

I say, the worst place for "VRS".... I enjoy the landing in a dark night at sea too. When you are down wind leg and when the boat due to operationnal reason go on " full black-out conditions" = no radio, no beacon, no radar, no light, and no boat in sight until some people light a cigarette...Not a big deal...but not the funniest ;)

20th Nov 2017, 06:22
I don't agree yet that being at a heavier AUW puts you less at risk of VR onset for aerodynamic reasons. With a higher angle of attack on the rotor blades the pressure difference between the top side and the bottom side of the rotor disc is greater; the high pressure side air is more prone to want to escape around the rotor tips to the low pressure side, and thus establishing a vortex ring which quickly deepens towards the blade root. As this happens the equation of lift vs gravity rapidly goes in the direction of gravity. Gullibell - that vortex is present regardless of stage of flight, as I am very sure you know - but for VRS to occur, there must be re-ingestion of that vortex at the tips and that requires you to catch up with your downwash.

The downwash speed is important regarding how quickly you have to descend to catch it and, although it can vary widely between aircraft types, I suspect the difference on the same aircraft between being at 70% AUM and 100% AUM is probably not very great and probably not measurable with the standard VSI in order to avoid VRS.

fijdor
20th Nov 2017, 12:39
Like already said in this tread before, this subject "VRS" has been discussed before from just about every angles by a lot of knowledgeable people (and there are in pprune) that went from the simplest explanations to the more elaborate ones, from the practical side of VRS to the theory side of it.
The consensus here seems to be that VRS is a dangerous condition to be avoided, if not recognized or understood or reacted upon it could end up in an accident and i am in agreement with this, being an experience (39 years in this) VFR, utility and VertRef pilot all my career I have experienced VRS many times during my carreer, almost unavoidable with more than 8,000hrs VertRef.
But as I said earlier VRS has been discussed from "just about every angles" but not all of them, I never heard anybody say anything good about it, so my question here is.

Does anybody here sees a good practical/useful side to VRS? just asking.

JD

Thomas coupling
20th Nov 2017, 14:45
Fijdor:

It's like asking:

Does anyone see the useful side of a stall or spin? :rolleyes:

PS: You probably haven't experienced 1 x VRS in your 8000hrs vertref (?).
Maybe the odd IVRS but that's about it.

PPS: VRS is ALWAYS avoidable. You obviously haven't been listening to the knowledgeable people have you? :ugh:

heliduck
20th Nov 2017, 14:50
Does anybody here sees a good practical/useful side to VRS? just asking.

JD

Absolutely - anyone who has done some production longline work in an AS350 would understand that VRS is VERY practical & uselful for teaching us to slow the f@#$ down & pay attention to what we are doing!!

albatross
20th Nov 2017, 16:12
How many times are we going to dance around this Maypole?

Self loading bear
20th Nov 2017, 18:54
Slightly off topic but interesting and positive use of vortex ring:

TV7jOEWVQHU

Or the vortex ring blower:

Ring Blower (http://www.aquatec.vn/ring-blower-25/?hl=en)

Cheers SLB

fijdor
20th Nov 2017, 21:29
My question still stands, has anybody see a useful side of VRS?

To Thomas Coupling, I do not know your experience and what you have done in your career and you don't know nothing about mine. Now to answer your comments in the order they have been written, you don't see any useful side of stall and spins, let me tell you this, there is a usefull side to spin and not to long ago it was used on a day to day basis and SAVED a lot of lives. Ask around. You are simply not aware of it.

You say that I probably never experience VRS in my 8000hrs of VertRef, not to sure what you base your info on? But HeliDuck seems to think otherwise for a vertref pilot and he is not the only one.

Always avoidable you are wrong on that one, it shows that you have never done any longline worth talking about and never work in Mountains or at altitude worth talking about.

I said there was a lot of knowledgeable people on this site and I meant it but I never said they were "All knowing beings"

On the subject of VRS, I have found the condition to be very useful on certain occasion and altitude. You see you can get a tremendous rate of descent (if you don't mind the rock&roll ride on the way down) also you get a STEADY rotor RPM all that time, no overspeed, quite handy at High altitude.

Understand there is no malice or intention of it in my writings.
Also understand that everybody has his own experience and done all sort of different things in this industry.

Question still stands, anybody else that have used that condition on purpose to attained a desired result?

newfieboy
20th Nov 2017, 21:49
Thomas Coupling,
I have worked along side Jacque , believe me he knows what he speaks of. Probably the most impressive experienced 214ST pilot on a longline in the World. Amongst thousands of hours on other mediums/heavies.
I respect your knowledge and experience in all things Mil and HEMS/Police. If you have never done production/precision longline I imagine you wouldn’t know.
Same as Jacque, I have over 8 grand hours on a longline doing production stuff i.e seismic. It is very easy to get into VR.
Just out of interest, how many hrs you got single pilot on mediums doing precision longline 10 hrs a day?

Scardy
21st Nov 2017, 01:54
VRS is deadly!
Spent many a years coming down the mountain with a dangling load in everything from lights to the big heavies.
Avoidable, yes! Just have to know it is there waiting to bite you. My Canadian Colleagues may disagree me, but personally I witnessed two drivers on same job experience VRS.
There was a reason for it, production!
It can happen anywhere anytime. (If you are not aware and tired)
My "teacher" retired a short time ago. He was in his 70's yes 70's and had over 30k.... said he only experienced it twice because he was not flying the machine it was flying him.
Wise man!

Thomas coupling
21st Nov 2017, 08:43
Fijdor/Newfie:

I'm going to put your lack of knowledge about this subject down to definition misunderstanding.

And I'm not going to waste any more of my life trying to educate people who haven't thoroughly researched the subject properly.

I can't force you to DYOR.

VRS is a DEVELOPED state. It is a situation where you as the pilot become a passenger. VRS will always end in disaster if there isn't sufficient height between you and the ground. If you have sufficient height - then an attempt at recovery often leads to a successful outcome - but not always.

INCIPIENT vortex ring [IVRS] is what people like you have 'probably' been into (due to your long line work) several times. You have 'probably' noticed the symptoms of the ONSET of VRS (which is IVRS) and responded appropriately, resulting in a fairly rapid and unexciting recovery. Probably within a couple of hundred feet.

Now there are DOZENS of very well discussed conversations on Pprune which dive deep into this subject matter. My advice to you two is to find an hour or two and go sit in a quiet corner and research more thoroughly the subject of VRS.

If you are either american or american trained, it is also essential you learn the difference between VRS and Settling with Power (SWP), because for some obtuse and bizarre reason, even your own FAA believe the two, are one and the same :=

Please find time (even at your level of competency) to research the following:

VRS versus IVRS.

and

VRS versus SWP.

I continue to be amazed by how many so called professional helicopter pilots out there STILL don't understand basic aerodynamic concepts.

Frightening............................

fijdor
21st Nov 2017, 14:45
I am a Canadian born and raised here, also trained in Canada by an experience pilot/instructor which seem to be out fashion these days (trained by an experience pilot/instructor that is).
In Canada, Transport Canada (our aviation authority here) is well aware of the difference between VRS and SWP and so am I. But you are right that the FAA do not recognize the differences.
So I will bow to your great knowledge of the subject and leave this tread and when I retire in 2 years from now I might take the time to read on VRS, IVRS and SWP and try to understand how I have been able to survive 40 years + doing what I am doing without knowledge of this condition called VRS (in it's fully developed state of course)

JD

Thomas coupling
21st Nov 2017, 15:16
Fijdor:

I did a 3 year exchange with the RCAF. During that time (helicopters) they trained me to be a waterbird instructor and also gave me my mountain flying instructors badge courtesy of the Rockies. Lovely people, gorgeous country.

With reference to your Transport Canada piece:
https://en.wikipedia.org/wiki/Vortex_ring_state
In it you will see that the FAA see it the same as SWP whereas Transport Canada don't. (thank god there appears to be common sense somewhere in N America).

When it comes to VRS Fijdor - believe me you have not knowingly entered fully developed VRS, or you'd probably not be here today / bent your aircraft.

You have probably entered Incipient VRS - which is "relatively" common amongst chopper pilots who are in a slow and descending / downwind / updraft scenario. But you have trained yourself to identify the conditions - quickly. Therefore you are out of the condition before you can say Justin Trudeau!

Fully developed VRS:
VERY high RoD. (thousands of feet per minute).
cyclic / collective/yaw - erratic.
Vibration.

{Just in case you weren't aware}. :ok:

fijdor
21st Nov 2017, 23:37
Thomas Coupling, I am glad you had a chance to fly the Canadian Rockies and liked your stay in Canada. Don't hesitate to come back and visit again.

.:ok:

JD

Here it is straight from the Transport Canada website. Copied and pasted here.

EXERCISE 26 - VORTEX RING

If the helicopter pilot chooses a flight path, airspeed and a rate of descent that coincides with the aircraft’s downwash, the helicopter could enter a condition known as the Vortex Ring state. The stall condition formed by the rate of descent flow in opposition to the induced flow, combines with the tip vortices present in all regimes of flight to produce a turbulent rotational flow on the blades and an unsteady spanwise shifting of that flow. This condition induces a very rapid rate of descent, vibrations, excessive flapping and a reduction in cyclic authority that could result in an accident. Obviously, this condition is to be avoided and the helicopter pilot should be able to recognize the incipient stage and be able to affect a safe recovery.

Your instructor will review the causes, conditions and symptoms of vortex ring. During a steep approach, at a high gross weight, high-density altitude and in a downwind or light wind condition; the helicopter may enter its own downwash and the development of vortex ring state. This situation would certainly contribute to the onset of vortex ring, but not necessarily cause it. The phenomenon is most likely to occur when all the conditions listed below are present:

in powered flight;
high rate of descent, in excess of 500 feet per minute; and
low airspeed, less than 20 MPH indicated.

Almost every transition from forward flight to a hover utilizes a powered approach, a rate of descent and a reduced airspeed. To prevent the occurrence of vortex ring, control your rate of descent less than 300 feet per minute.

Recovery Techniques. There are two methods of effective recovery from the vortex ring state. Both change the airflow conditions causing it and both involve a loss of height:

Dive out. Normally this technique will result in less altitude loss than with the autorotational recovery. The pilot should apply forward cyclic while reducing the collective; the vortices will leave the disc as the airspeed increases and the helicopter will move forward of its downwash. Normal flight may then be resumed.
Enter autorotation. By this method, the airflow through the rotor changes from the disturbed flow of the vortex ring to the upward autorotational flow. Once autorotational descent has commenced then the pilot may ease the cyclic forward to gain airspeed while power is increased and normal flight resumed.

You should note that an increase in collective alone may not result in a recovery and indeed may only serve to increase the rate of descent. This increase in blade pitch will cause the vortices to intensify in strength and will result in a more rapid descent.

There are some uninformed pilots who use “settling with power” to describe vortex ring, in fact some publications use the terms interchangeably. Confusion results when symptoms are related that do not describe true vortex ring but rather describe “settling with insufficient power”. This may occur when a pilot attempts to arrest a rapid, low power descent only to find that he has insufficient power available to bring the helicopter to either a hover or a no-hover landing without exceeding the engine limits. However, this is not a vortex ring situation.

Another situation, ‘over-pitching’ is often misinterpreted as vortex ring. This is where the pilot rapidly increases collective considerably and the engine cannot produce enough power to overcome the large, swift increase in drag on the rotor system. The result is that the rotor system quickly slows down and loses efficiency causing the helicopter instantly to sink. Again, this is not vortex ring.

The most common situations, where you would be most likely to encounter vortex ring, are usually when you misjudge the wind with a heavy load on a hot day. Downwind approaches to a confined area, or a mountain pad, are two good examples. Always control your rate of descent carefully on these occasions, and make sure an escape route is available. Your instructor will discuss the symptoms and recovery techniques more fully. Demonstration of this exercise is not generally performed, as the stresses on the airframe and rotor system are unknown.

PREVENTION IS BETTER THAN CURE!!!

r22butters
22nd Nov 2017, 00:12
...I never heard anybody say anything good about it, so my question here is.

Does anybody here sees a good practical/useful side to VRS? just asking.

JD

Once while scuddrunning in an R44 I went IIMC, but eventually got clear of the clouds when I started falling after getting into VRS as well!

r22butters
22nd Nov 2017, 03:12
Fijdor/Newfie:

I'm going to put your lack of knowledge about this subject down to definition misunderstanding.

And I'm not going to waste any more of my life trying to educate people who haven't thoroughly researched the subject properly.

I can't force you to DYOR.

VRS is a DEVELOPED state. It is a situation where you as the pilot become a passenger. VRS will always end in disaster if there isn't sufficient height between you and the ground. If you have sufficient height - then an attempt at recovery often leads to a successful outcome - but not always.

INCIPIENT vortex ring [IVRS] is what people like you have 'probably' been into (due to your long line work) several times. You have 'probably' noticed the symptoms of the ONSET of VRS (which is IVRS) and responded appropriately, resulting in a fairly rapid and unexciting recovery. Probably within a couple of hundred feet.

Now there are DOZENS of very well discussed conversations on Pprune which dive deep into this subject matter. My advice to you two is to find an hour or two and go sit in a quiet corner and research more thoroughly the subject of VRS.

If you are either american or american trained, it is also essential you learn the difference between VRS and Settling with Power (SWP), because for some obtuse and bizarre reason, even your own FAA believe the two, are one and the same :=

Please find time (even at your level of competency) to research the following:

VRS versus IVRS.

and

VRS versus SWP.

I continue to be amazed by how many so called professional helicopter pilots out there STILL don't understand basic aerodynamic concepts.

Frightening............................

Here in America VRS and SWP are the same thing, so there's no need to learn the difference!

BOBAKAT
22nd Nov 2017, 03:15
For years, i don't understand the big mistake/confusion/ of the FAA about VRS and SWP. I am a " old French school helicopter pilot" and when we are young duck, we learn the difference...Why the FAA not ?

Rotorbee
22nd Nov 2017, 07:24
Please cut the FAA some slack. They are not that stupid. Actually at least to me they proved to be a quite educated, helpful and very polite bunch of people. Well nicer than some other aviation authorities I had the misfortune to deal with.

If you read the FAA Helicopter Flying Handbook in its latest version in chapter 11 page 9 you find this:

Settling With Power (Vortex Ring State)
Vortex ring state describes an aerodynamic condition in
which a helicopter may be in a vertical descent with 20
percent up to maximum power applied, and little or no climb
performance. The term “settling with power” comes from
the fact that the helicopter keeps settling even though full
engine power is applied.

The FAA sees Vortex Ring State as an aerodynamic condition and Settling with Power as the phenomenon the pilot will experience. A reasonable explanation, if you ask me. I could live with it (apparently the confusion is a result from a time the US Navy messed it up). The FAA is certainly aware of the mess about VRS and SWP in its own country and having read their stuff about it in several editions, there is a clear tendency to straighten things out. But they have to deal with a whole bunch of different types of pilots who raise their voices about everything all the time. Especially the old FI's do not read that book again they have read 30 or 40 years ago (at least nobody here did it). To keep the confusion to a minimum, the FAA has to do this slowly. One day, everybody will be on the same page.

Somebody should probably go and change the wikipedia article to be more precise.

If you want to read the whole chapter about it go HERE (https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/media/hfh_ch11.pdf)

PS: What many of us will not like too much is the recovery part. Read it, it might annoy you.

SuperF
22nd Nov 2017, 07:53
fijdor, is that a lesson that is taught to students in Canada? Reading it looks like you go out and show the newbies VRS, how to get in and out, ho to recognise that you are getting in, so you can avoid, or at least know that you are getting close.

I'm sure I went through a lesson like that a couple of decades ago in a 22....

Thomas coupling
22nd Nov 2017, 08:51
Fijdor:
It seems TC and TC (get it: transport canada and thomas coupling) are singing from the same hymn sheet. Probably because they are not american:ugh:
Are we all agreed now that you and others who say they have entered VRS several times - haven't really? It;s almost certainly IVRS.

R22butters:
C'mon now sunshine - you can do better than that, three or four hooks on your fishing line (R22, IIMC, scud running, VRS). - no subtlety at all. :D

Rotorbee:
For clarification - what do the FAA call the engine performance phenomena where the power available to a helicopter attempting to stop a descent is insufficient to prevent that aircraft from stopping - IE: Settling with Power?
Do they call it: Power Settling?:ooh:

paco
22nd Nov 2017, 08:58
I have always thought that your example is power settling.

A Canadian friend of mine explained VRS/SWP it this way (if it helps):

You could probably say that VRS is “settling with a bit of power applied” and SWP is “settling with lots of power applied.” One will happen with an empty water bucket, as you descend into the dip-site and the other will happen with a full water bucket as you prepare for a drop.

Phil

Thomas coupling
22nd Nov 2017, 10:17
I can't help myself - I did say I'm not wasting my life getting back into this, but it really does worry me that very experienced pilots like you Paco, still haven't gripped a fundamental phenomena like VRS or PS or SWP.

Watch and learn!

VRS is an AERODYNAMIC EVENT - it's all to do with bernoulli and air flow.
swp is an ENGINE PERFORMANCE EVENT - it's all to do with horse power and AUM.

and neither the twain shall meet (except in la la land in america :ugh:).

Please will anyone who can't or hasn't grasped this very basic phenomena (VRS/SWP) go find time to research it properly and learn to UNDERSTAND it before it bites you hard in the damn ASS FFS.:mad:

paco
22nd Nov 2017, 10:52
But Bernoulli only accounts for about 2% of why anything flies....

Be that as it may, VRS only happens when power is applied, so it can't be just aerodynamic. I use the term power settling to try to avoid confusion. That way the guys over the other side of the pond can be happy as well.

Rotorbee
22nd Nov 2017, 13:39
@TC: Frankly I did not have the time to read the whole latest issue of the FAA book. It's online, it's free, why don't you have a look around, too? Who knows, with time we might find something.

But there is something else you might consider. About the only organisation that really does that differentiation is TC. Until now, I have not found the term power settling or settling with power other than as synonym for VRS in any other newer official publication.
What I have found so far is that almost everybody calls it VRS(SWP) - with the brackets -, even EASA, and when pilots do have the "real" SWP it is called pilot error, plain stupid or that dreaded "sudden power loss on approach" the pilot said in the accident report.
Nick Lappos once wrote that this effect was also called HTG (Hit The Ground).

From the dumb fat and happy pilot's perspective the two terms are not that far apart. From SWP/PW you can get into VRS, circumstances permitting. To solve the problem, the pilot must do the same thing - speed up, flee, get out of there, try again. Having said that, Vuichard disciples would be in for a surprise, if it was SWP and not VRS.

I personally think we should consider the following. Get rid of one of the terms, preferably SWP and never to bring it up again in any pilot handbook or publication.
It would probably save a lot of bytes in the long run. On the other hand, that would deprive us from a very funny discussion theme.

BOBAKAT
22nd Nov 2017, 14:24
1/You make a vertical approach but you are :
heavy
down wind
low speed , nearly zero..
High rate of descent...
You are in good conditions to going to VRS...but not sure at 100% Sometimes nothing happens...

2/From the edge of the Grand canyon, you go in hovering just at the power limit nearly 95 %... you translates slowly to te grand Canyon....When you arrive above the Grand Canyon, you lose the IGE and you falling down : That is Settling with power and sure at 100% it's happens all the time..

The really one difference is , you need much more power in OGE than IGE....no matter with thewind, yourspeed or your rate of descent asYour are hovering..but VRS is aerodynamic and SWP is justa power matter.. and exactly 7%...No more, no less

Thomas coupling
22nd Nov 2017, 14:53
Breath deeply and count..............................

OK..........mindfullness over.

Rotorbee - you disappoint me.

Bobakat:

When an a/c develops VRS or IVRS, 'stuff' happens inside the lift drag curve where big green arrows and vectors and angles of attack all start moaning and complaining they aren't happy and as a result of this quiet revolution going on around your rotor disc, the aircraft says F-u-*-k it, I'm outta here and goes into freefall.
No one else has come along and spoilt the party - it's all down to that nasty neighbourhood and bunch of trouble makers the "aerodynamic gang".

When an a/c develops SWP, you're in a different neighbourhood. You're in the engine neighbourhood - the hot gas clan - those nasty individuals who spend all day hitting that huge compressor at the back of the class.
The a/c needs to stop as it ends its decent to land or is approaching an obstacle and the hot gas clan come out in force until all of them that are available are hitting the compressor kid as hard as possible, to the extent where the engine says to hell with this excessive violence in my classroom, enough is enough, we cannot continue to produce the output you require from this compressor to bring the MASS of this a/c to a stop (before it hits the ground/obstacle).

Look at it another simplistic way:

You are landing your jumbo jet at Heathrow and for that given AUM you decide to apply maximum reverse thrust to prevent yourself running off the runway. But all the reverse thrust available is not sufficent to arrest the AUM in time to keep it on the runway. Your engines aren't powerful enough (IN THE REMAINING DISTANCE OFFERED) to arrest your particulr AUM.

It is an engine thang! Nothing to do with little green arrows/updraft/alpha.

Learn the difference guys and don't show your ignorance in basic helicopter theory FFS.

Calm..............close my eyes.....relax........:cool:

Rotorbee
22nd Nov 2017, 17:32
TC, you break my heart. Nothing could be more hurtful than your accusation that I disappoint you ...Er, why exactly?

PS: BOBAKAT and TC - don't you two mean the same thing but keep misunderstanding each other? VRS - aerodynamics, SWP - Pooooowwwweeeer

r22butters
22nd Nov 2017, 17:36
R22butters:
C'mon now sunshine - you can do better than that, three or four hooks on your fishing line (R22, IIMC, scud running, VRS). - no subtlety at all. :D

Rotorbee:
For clarification - what do the FAA call the engine performance phenomena where the power available to a helicopter attempting to stop a descent is insufficient to prevent that aircraft from stopping - IE: Settling with Power?
Do they call it: Power Settling?:ooh:

He wanted to know if anyone had anything positive to say about VRS? Well I do,...it saved my life once!,...and it was in a 44!:=

I don't know what the FAA calls it when you have insufficient power to stop your decent, but I call it FTS.
FULL THROTTLE STUPID!:eek:

"Sunshine"? HA! No one who's ever met me would ever call me that! It was a good laugh though! :ok:

r22butters
22nd Nov 2017, 19:38
Breath deeply and count..............................

OK..........mindfullness over.

Rotorbee - you disappoint me.

Bobakat:

When an a/c develops VRS or IVRS, 'stuff' happens inside the lift drag curve where big green arrows and vectors and angles of attack all start moaning and complaining they aren't happy and as a result of this quiet revolution going on around your rotor disc, the aircraft says F-u-*-k it, I'm outta here and goes into freefall.
No one else has come along and spoilt the party - it's all down to that nasty neighbourhood and bunch of trouble makers the "aerodynamic gang".

When an a/c develops SWP, you're in a different neighbourhood. You're in the engine neighbourhood - the hot gas clan - those nasty individuals who spend all day hitting that huge compressor at the back of the class.
The a/c needs to stop as it ends its decent to land or is approaching an obstacle and the hot gas clan come out in force until all of them that are available are hitting the compressor kid as hard as possible, to the extent where the engine says to hell with this excessive violence in my classroom, enough is enough, we cannot continue to produce the output you require from this compressor to bring the MASS of this a/c to a stop (before it hits the ground/obstacle).

Look at it another simplistic way:

You are landing your jumbo jet at Heathrow and for that given AUM you decide to apply maximum reverse thrust to prevent yourself running off the runway. But all the reverse thrust available is not sufficent to arrest the AUM in time to keep it on the runway. Your engines aren't powerful enough (IN THE REMAINING DISTANCE OFFERED) to arrest your particulr AUM.

It is an engine thang! Nothing to do with little green arrows/updraft/alpha.

Learn the difference guys and don't show your ignorance in basic helicopter theory FFS.

Calm..............close my eyes.....relax........:cool:

Hmm, the way you are describing it here makes it sound more like a distance thang to me! Its not settling with power, its just not paying attention!:=

Its like driving in the rain or ice, if you want to stop in time, you need to start slowing down sooner!

fijdor
22nd Nov 2017, 20:19
Fijdor:
It seems TC and TC (get it: transport canada and thomas coupling) are singing from the same hymn sheet. Probably because they are not american
Are we all agreed now that you and others who say they have entered VRS several times - haven't really? It;s almost certainly IVRS.

TCoupling bare with me as you have probably noticed the English language is my second language, I am French Canadian.

No worries I see your point. Also I realized last night that there are no confusion in what VRS actually is or what it can do to you or how to recognize the first signs of it or confusion on how get out of it. The confusion/misunderstanding here is in the word itself.
Now let see if you will see my point. The text from TC pasted earlier says "incipient" you are right, but nowhere in any books or anywhere else during your initial training or annual training do they use IVRS. For us here in Canada the term incipient means you are at the beginning , first stage, the start of VRS. We have no separate or different terms to describe the different stages or the evolution of the condition from its beginning/early stage to its fully developed condition.
That you are in it at the beginning or at the end coming down 25,000ft a second it is still only called VRS. First time I heard of IVRS is here on this forum. (earlier tread)
This winter when I start giving training and if I start using the term IVRS they will all look at me and say something like, Are you sure you want to wait another 2 years before retirement. lol Now if you say that before we can call it VRS, it has to be in its full development or solidly on its way there then that might take while to get implemented in this industry.
But again I see your point.

For SuperF, yes it is a lesson or exercise 26 and part of what a student pilot should learn to get his license. But I am not not an instructor and I am not up to speed with how they teach it. I am a training pilot and give annual company training to professional pilots on Mediums (205 nowadays) and also longLine training where VRS SWP are an important part of it. 205 are notorious to get into SWP on a hot and humide day when loaded. Most of the pilots here have a good understanding on the differences of the two conditions. I do have a way of explaining both conditions if needed.

JD

SuperF
23rd Nov 2017, 00:50
fijdor,

my memory must be still working alright. it was in a 22 a long time ago, and I'm now far more comfortable in a 204 myself. totally agree that you can get all sorts of "fun" in a Bell medium if hot, high, heavy or a combination, especially sitting on top of a longline as you try to sink 200" into the "hole" in the trees!

RVDT
23rd Nov 2017, 01:52
Tabernac!

Careful boys - this is what fijdor looks like after he gets frustrated!

https://pbs.twimg.com/profile_images/1394693837/Black_Jacques_Shellac_400x400.jpg

Ça va, JD?

23rd Nov 2017, 06:03
The other way of considering the difference between VRS and SWP is to look at Nr.

In SWP, you have run out of power - but keep pulling anyway - the Nr will decay and you will descend - often to ground impact.

In VRS, you have run out of lift - because of the stalled roots and the vortex-ingesting tips - you can get to this stage without running out of power.

The 'lesson' given to students about VRS often involves flying downwind at 1500' or so, reducing speed below 30 kts and then allowing a slight RoD to develop - at this point the lever is raised and the ensuing vibration is described as VRS (it isn't VRS) and immediate recovery is made by increasing speed and flying out.

The student is scared by the vibration and the instructor has shown the conditions for entry - everyone goes away happy but there has been no VRS demonstrated or recovered from - only what we are now calling IVRS.

It's a bit like the difference between FW spin recovery (from a fully developed spin) and incipient spin recovery - one involves a specific series of actions to recover from the high RoD into controlled flight and the other usually just requires centralisation of the controls.

The difference between incipient spin and fully developed spin is large - in exactly the same way that the difference between IVRS and VRS is large.

SuperF
23rd Nov 2017, 06:21
Hi Crab,
Some of us got the other lesson. Climb out to about 8,000’ in a 22. Yes it took a while from memory... same start of lesson, turn down wind, pull airspeed back to zero, start a descent, shaking scary stuff, pull power, going down faster, I remember the VSI being pegged as low as it would go. After what seemed like an hour, and loosing a few thousand feet, we started a recovery and came out about 1000”.

Scared the crap out of me, but I made sure everything was done into wind after that!

23rd Nov 2017, 16:12
Hi Super F - yes that sounds like the real deal alright - I hope everyone reads your post and realises the difference between what you experienced and what so many others get.

I wonder how confident Mr Vuichard would have been in his 'technique'...........

r22butters
23rd Nov 2017, 17:35
Hi Crab,
Some of us got the other lesson. Climb out to about 8,000’ in a 22. Yes it took a while from memory... same start of lesson, turn down wind, pull airspeed back to zero, start a descent, shaking scary stuff, pull power, going down faster, I remember the VSI being pegged as low as it would go. After what seemed like an hour, and loosing a few thousand feet, we started a recovery and came out about 1000”.

Scared the crap out of me, but I made sure everything was done into wind after that!

Last time I did SWP downwind like that I got an immediate, surprise 90° yaw,...startled the **** out of me! He had me do that new sideways recovery technique,...its pretty cool!:ok:

23rd Nov 2017, 18:25
No butters, your trolling still doesn't have any subtlety....................:ugh:

r22butters
23rd Nov 2017, 18:54
No butters, your trolling still doesn't have any subtlety....................:ugh:

Nope, that actully did happen!

FH1100 Pilot
23rd Nov 2017, 19:20
I don't know where some of you guys are coming from. The U.S. FAA teaches now...has always taught...that "Settling With Power" is recirculation of the vortices produced by the main rotor. I won't reprint or repost the applicable section of the FAA's Helicopter Flying Handbook - you can read it yourself. But it's what I was taught when I was learning to fly in the 1970's. To recap: The FAA says that SWP *is* VRS.

But because the current generation of Robbie Rangers have to over-complicate and try to quantify EVERYTHING, some of you have invented your own definition and explanation of SWP - that of a botched approach (vertical or otherwise) in which the engine does not have enough power to stop the descent. Fine. Sounds like pilot screwupery to me. And strangely, the FAA does not address this "phenomenon" or aerodynamic condition directly. I guess they leave it up to the pilot to know the performance characteristics of his or her particular helicopter and abide by them and not land on a runway so short that full reverse won't stop you. You know, that's not the plane's fault.

In reality...in the real world of helicopter flying, it *almost* doesn't matter what you call it, or whether it's "settling without enough power to stop" or true vortex recirculation. You're probably going to crash. Yeah, yeah, if you recognize it early you might be able to employ Sr. Vuichard's technique (good luck!)...*or*...you might be able to fly out of it forward. But you usually get into it until the very bottom of a poorly-executed approach...you know, where it usually happens to those of us who don't have things dangling under our helicopters on longlines. And if it does happen at the bottom of such a messed-up approach, and you're a little slow to recognize what's happening (welcome to the club!), then you'll probably end up with smiling skids and your peers will be calling you by the nickname Bing Dang Ow from now on. (Ohhhh, just remembering that bimbo newscaster blithely reading the fake names of those Asiana Airline pilots makes me chuckle.)

I often tell the story (faithful readers of my crap have all heard it by now) of sitting in the Vibro-Massage chair attached to the Bo-105 I was flying in the Gulf of Mexico. I'd be on approach to some drilling rig which was situated in a way that the heliport was on the exact WRONG side of the rig for the winds that day. And I'd sit there, pretty much at full power as the 105 did it's notorious shake, rattle and roll coming back through ETL...I'd sit there wondering, "Is this just the 'normal' Bo-105 vibrations, or are we on the edge of SWP?" I'd be super-attentive to the collective, waiting for it to become "unhooked" from the RoD. Because you never know, right? No, you never do.

People ramble on and on about the "differences" between SWP and VRS. They say that during SWP, because you're pulling more than the engine can supply then the RPM will droop. Well...you know...aaaahhhh...most of real helicopter pilotos fly real helicopters powered by this new invention called the turbine engine. We don't pay much attention to the trials and tribulations of the unwashed, bearded riff-raff in the R-44's. I mean, really. And these modern turbines don't droop.. (At least not anymore! Anybody remember the Allison C-18 days? I do. And not fondly.)

So prattle on, boys...drone on and on about how there's such a BIG difference between SWP and VRS. The more experienced pilots among us will just chuckle and shake our heads and fly 'em the way we know how.

chopjock
23rd Nov 2017, 19:22
What difference does it make going down wind at several thousand feet? Might as well practice your VRS entry in any direction?

r22butters
23rd Nov 2017, 20:05
I don't know where some of you guys are coming from. The U.S. FAA teaches now...has always taught...that "Settling With Power" is recirculation of the vortices produced by the main rotor. I won't reprint or repost the applicable section of the FAA's Helicopter Flying Handbook - you can read it yourself. But it's what I was taught when I was learning to fly in the 1970's. To recap: The FAA says that SWP *is* VRS.

But because the current generation of Robbie Rangers have to over-complicate and try to quantify EVERYTHING, some of you have invented your own definition and explanation of SWP - that of a botched approach (vertical or otherwise) in which the engine does not have enough power to stop the descent. Fine. Sounds like pilot screwupery to me. And strangely, the FAA does not address this "phenomenon" or aerodynamic condition directly. I guess they leave it up to the pilot to know the performance characteristics of his or her particular helicopter and abide by them and not land on a runway so short that full reverse won't stop you. You know, that's not the plane's fault.

In reality...in the real world of helicopter flying, it *almost* doesn't matter what you call it, or whether it's "settling without enough power to stop" or true vortex recirculation. You're probably going to crash. Yeah, yeah, if you recognize it early you might be able to employ Sr. Vuichard's technique (good luck!)...*or*...you might be able to fly out of it forward. But you usually get into it until the very bottom of a poorly-executed approach...you know, where it usually happens to those of us who don't have things dangling under our helicopters on longlines. And if it does happen at the bottom of such a messed-up approach, and you're a little slow to recognize what's happening (welcome to the club!), then you'll probably end up with smiling skids and your peers will be calling you by the nickname Bing Dang Ow from now on. (Ohhhh, just remembering that bimbo newscaster blithely reading the fake names of those Asiana Airline pilots makes me chuckle.)

I often tell the story (faithful readers of my crap have all heard it by now) of sitting in the Vibro-Massage chair attached to the Bo-105 I was flying in the Gulf of Mexico. I'd be on approach to some drilling rig which was situated in a way that the heliport was on the exact WRONG side of the rig for the winds that day. And I'd sit there, pretty much at full power as the 105 did it's notorious shake, rattle and roll coming back through ETL...I'd sit there wondering, "Is this just the 'normal' Bo-105 vibrations, or are we on the edge of SWP?" I'd be super-attentive to the collective, waiting for it to become "unhooked" from the RoD. Because you never know, right? No, you never do.

People ramble on and on about the "differences" between SWP and VRS. They say that during SWP, because you're pulling more than the engine can supply then the RPM will droop. Well...you know...aaaahhhh...most of real helicopter pilotos fly real helicopters powered by this new invention called the turbine engine. We don't pay much attention to the trials and tribulations of the unwashed, bearded riff-raff in the R-44's. I mean, really. And these modern turbines don't droop.. (At least not anymore! Anybody remember the Allison C-18 days? I do. And not fondly.)

So prattle on, boys...drone on and on about how there's such a BIG difference between SWP and VRS. The more experienced pilots among us will just chuckle and shake our heads and fly 'em the way we know how.

Easy there turbine boy! Don't blame this crackpot "SWP isn't VRS" crap on Robbie Rangers! We're the ones who still believe the textbook!:=

fijdor
23rd Nov 2017, 20:43
Tabernac!

Careful boys - this is what fijdor looks like after he gets frustrated!

https://pbs.twimg.com/profile_images/1394693837/Black_Jacques_Shellac_400x400.jpg

Ça va, JD?

RVDT, you funny guy you. lol Oui ca va. Looks like they took THAT picture out of the message.

JD

Ascend Charlie
23rd Nov 2017, 20:47
FAA's Helicopter Flying Handbook - you can read it yourself. But it's what I was taught when I was learning to fly in the 1970's. To recap: The FAA says that SWP *is* VRS.

Your FAA "Bible" has a lot of Fake News in it, being designed to teach the lowest common denominator, so it glosses over things and simplifies them to the point of error.

For example, it states as a fact that the air pressure increases under a rotor disk in IGE, causing less induced flow. Wrong.

On page 2.19 it shows a diagram from above with coloured part on the right saying that with forward motion, the advancing side gets more lift, and the retreating side gets less lift (IF NOTHING IS DONE ABOUT IT) and this will cause the aircraft to roll left. Garbage.

It preaches gyroscopic precession, which should only be used as a guide to understanding the delays in blade movement and the advance angles built into the swash plate to make up for them, not as the reason the disk behaves like it does.

So don't quote the FAA book as being absolute truth, it is merely a teaching aid, and not a particularly good one at that.

newfieboy
23rd Nov 2017, 22:53
TC,
We hear where you coming from Mate. Your experience seems to be Mil/Police/Medevac etc. We get that.
One simple question how much time you got in the mountains, and I don't mean the Beacons, at altitude, heavy all day, single pilot doing the longline stuff we do in Canada?

SuperF
24th Nov 2017, 01:03
What difference does it make going down wind at several thousand feet? Might as well practice your VRS entry in any direction?

I guess that was asked to me? I've got no idea, except maybe if you are doing it into wind, that when you get into the falling out of the sky part, that you are actually travelling backwards relative to the ground. I doubt if that makes any difference to the actual experience, but "maybe" it was proving the point that its best to make an approach into wind when you can.

Having never done any instructing, i would only be guessing.

eagle 86
24th Nov 2017, 02:29
Crab and Charlie are exactly correct on all counts - end of story full stop.

Thomas coupling
24th Nov 2017, 08:32
I love a good slanging match especially when it comes to 'us' and 'them'.

FH100: Sorry big guy - you're talking boll o cks (like the FAA do - much of the time). Europe and Canada bow to the superiority of the FAA (not).
As Ascend Charlie said - there's a lot of mischief in those FAA manuals.

And this is definitely one of them: SWP.

For the record, this clip is perfect SWP from a very well trained and probably experienced yank driver. He's done these approaches numerous times and is aware of many of the gottcha's out there, I would argue, especially vortex ring.
Which is why he wasn't expecting this:

https://www.youtube.com/watch?v=1DDDpI263qE

And do you know why he wasn't expecting this? Because it wasn't VRS it wasn't even close to VRS. The conditions for VRS were a million miles from this guys approach (into wind/ >30kts to start with / minimal RoD), I bet he wasn't even close to IVRS (vibration, increasing RoD).

This is THE perfect example of SWP and you yanks really do need to wake up and smell the coffee - the rest of the world (for once) aren't wrong with this.

[Day after day - more and more "experienced" pilots come on here and display a level of ignorance which is becoming more and more endemic as we speak. Christ, if experienced driver's are behaving like this - how, in the name of faith can we ever slag off lesser mortals???].


If helicopter pilots don't understand basic aerodynamic/ engine related phenomena like : VRS / IVRS / SWP / PS / LTE / LTA, they should be ashamed to call themselves pilots.:ugh:

Newfieboy - don't get where you are coming from? Is there a link to God - through long line - to VRS, or something? Is long line the dog's boll o x, then? Are longline pilots world experts in VRS? Keen to know more about this band of brothers gospel according to?

chopjock
24th Nov 2017, 12:51
TC,
If that video was an example of SWP, how come there was enough power to lift off again?
Looks more like SPE (simple pilot error).

FH1100 Pilot
24th Nov 2017, 15:46
TC, sorry to break it to you, but the CH-46 accident wasn't even SWP. It was merely a misjudged approach. He probably had plenty of power. But he screwed up. His approach angle was nice and constant, but the boat was moving up and down - something obviously not taken into account. The '46 pilot came in way too shallow and caught a wheel on the fencing. Oops! Happens. It's why PHI taught us to come into oil platforms steep and slow, never shallow and fast - just for that reason. Worked for me.

To those of you who say the US FAA is wrong about this or that...well...whatever. If it makes you guys feel superior or something, that's fine.

If you guys want to narrowly define SWP as something other than VRS...well...I think y'all are wrong.

r22butters
24th Nov 2017, 16:43
Its always the internet "pilots" bragging about how "experienced" they are who say the textbook is wrong,...always!:=

In the real world, I have never met a pilot who thinks SWP is anything other than VRS!

,...but carry on God's gifts to aviation!:D

Hughes500
24th Nov 2017, 18:18
Havent met me then !:ok:

JohnDixson
24th Nov 2017, 19:39
This link provides some detailed background for the 1999 CH-46 accident:

Sea Knight off San Diego (http://www.check-six.com/Crash_Sites/SeaKnight-USMC-1999.htm)

Ascend Charlie
24th Nov 2017, 20:21
Butters, as you admit on that other forum, your real world experiences weren't particularly successful, were they?

And what you said tells me that the pilots you have met have been poorly taught. There is a huge difference between SWP and VRS.

Thomas coupling
24th Nov 2017, 22:02
Ascend charlie: you are wasting your time i'm afraid.
A pilots ego is often bigger than his brain.
What a shame because so called experienced pilots have so much to offer those who look up to them. It's a big responsibility ensuring those coming up behind you do it properly.
It is literally a life saver.

BOBAKAT
25th Nov 2017, 09:44
Butter you meet all Helicopter pilot in the world ?

Sure if you talk only with ATPLH pilot flying from base A to baseB and back with AP on.... It's really rare for them to meet Mr SWP and VRS...
but for the utility pilot long line and many others, is the reality.. For myself i experiment both situations. In both case i finish my flight safe, but maybe have to change my pants... I teach really my studient about VRS above 1000 ft. I want they feel the vibrations and the stick dribble. I simulate the power limit for the SWP.... And i am happy when they understand what happen... ;)

Devil 49
25th Nov 2017, 14:44
Its always the internet "pilots" bragging about how "experienced" they are who say the textbook is wrong,...always!:=

In the real world, I have never met a pilot who thinks SWP is anything other than VRS!

,...but carry on God's gifts to aviation!:D


Your ignorance and inexperience is showing. My memory is that we taught VRS as 'settling with power' in 68-70 US Army. I was taught to teach it in exactly the conditions of VRS, including the application of power accelerating the descent. It was hard to reliably induce the fully developed state in a TH55, as zero airspeed is hard to determine at the altitudes we did this. We, the pilots in my cohort, interchanged the terms until the late '70s early '80s when the recirculating rotor down wash was broadly taught. This I think lead to the confusion.

My memory may be wrong, but VRS signals subtly that something is happening, vibrations and uncommanded attitude changes and then when in the fully developed VRS, the aircraft feels 'sloppy', less crisp in response. SWP seemed to be more normal aircraft response in the descent, you ran out of power (or NR in the Huey) . We didn't intentionally fly into full SWP, but demonstrated it with power limitation.

Final point: In the real world, I have never had a textbook defined issue in flight. One teaches somewhat simplistic, defined issues in primary instruction to teach the most appropriate resolution clearly and emphatically. The flying part of the instruction is especially simplistic in my opinion, insisting on specific airspeed, altitude and approach procedures as though that kept hobgoblins away. It ain't that clear and easy when you're working the line...

heliduck
25th Nov 2017, 15:54
It ain't that clear and easy when you're working the line...

An important point has been made here by Devil - in longline work when things don’t go to plan there’s just no time to consider if your in VRS, SWP, over pitching, or any other plethora of situations which ruin our day. You just need to react, listen to what the aircraft is telling you through your backside/eyes/ears & fix it. You need to be aware of this BEFORE the condition develops, almost subconsciously, firstly to avoid it but also to ensure you take the correct action should you fail in the avoiding part.
I think I’ve been in a VRS situation once, I say “think” deliberately as I didn’t hear a change in aircraft power train noise & couldn’t tell you what the gauges were saying (didn’t look!) as within a few seconds I had to fix it or hit the ground therefore my eyes were outside the cockpit & apparently my hands & feet were busy fixing this problem I had created. I’m happy to report I fixed it. There won’t be a second time.
There has been many comments on this thread re “here we go again” & I get that, but personally I enjoy reading all of these opinions & using the information to cross check & confirm that what I thought I knew still makes sense to me so that when my hands & feet need to react there’s no delay. Keep the discussion alive, it shouldn’t matter what our instructor said, once we have the licence it’s up to us to continue to learn, challenge what we were taught & verify, verify, verify. Theology can be debated, but physics & aerodynamics in 2017 are pretty well understood - VRS is VRS, SWP is SWP, over pitching is overpitching.
Misinformation is widespread though; despite Transport Canada differentiating between VRS & SWP I noticed yesterday that the Saskatchewan & Alberta National Aerial Pesticide Application Manuals both state that rotary pilots should pay particular attention to “vortex ring state(settling with power)”. Here we go again.

r22butters
25th Nov 2017, 17:17
Your ignorance and inexperience is showing. My memory is that we taught VRS as 'settling with power' in 68-70 US Army. I was taught to teach it in exactly the conditions of VRS, including the application of power accelerating the descent. It was hard to reliably induce the fully developed state in a TH55, as zero airspeed is hard to determine at the altitudes we did this. We, the pilots in my cohort, interchanged the terms until the late '70s early '80s when the recirculating rotor down wash was broadly taught. This I think lead to the confusion.

My memory may be wrong, but VRS signals subtly that something is happening, vibrations and uncommanded attitude changes and then when in the fully developed VRS, the aircraft feels 'sloppy', less crisp in response. SWP seemed to be more normal aircraft response in the descent, you ran out of power (or NR in the Huey) . We didn't intentionally fly into full SWP, but demonstrated it with power limitation.

Final point: In the real world, I have never had a textbook defined issue in flight. One teaches somewhat simplistic, defined issues in primary instruction to teach the most appropriate resolution clearly and emphatically. The flying part of the instruction is especially simplistic in my opinion, insisting on specific airspeed, altitude and approach procedures as though that kept hobgoblins away. It ain't that clear and easy when you're working the line...

,...and you just made my point!

You call running out of power "settling with power",...even a college dropout can tell that makes no sense!:ugh:

,...but I know, keep stroking your egos and looking down your noses at the poor little, gullible, Robby guy who dares to believe the logical explanation given in the textbook!:rolleyes:

megan
26th Nov 2017, 01:11
Posters may wish to peruse this thread, and note Nick Lappos's input. I'm not about to argue with Nick.

http://www.pprune.org/rotorheads/67635-power-settling.html

r22butters
26th Nov 2017, 02:49
Posters may wish to peruse this thread, and note Nick Lappos's input. I'm not about to argue with Nick.



I did find this point of his a nice read!

Nick Lappos , 2nd Jun 2002 04:32
Blenderpilot,
I have to agree with squirrel. You and sultan are mixing up the fundamental problem of having too little power with the other aerodynamic condition specifically related to reingestion of the downwash known as Vortex Ring State or settling with power.

What I think you are concerned about is a true issue for pilots - the behavior of the machine when you are severely performance limited. That causes most helicopter accidents that occur on landing, is especially a problem at altitude and high temperature, and has nothing at all to do with settling with power
:ok:

Devil 49
26th Nov 2017, 16:31
,...and you just made my point!

You call running out of power "settling with power",...even a college dropout can tell that makes no sense!:ugh:

,...but I know, keep stroking your egos and looking down your noses at the poor little, gullible, Robby guy who dares to believe the logical explanation given in the textbook!:rolleyes:

Dude, the point I was attempting to make was that the textbook was wrong. If that single mistake, identifying SWP and VRS as one and the same, wasn't sufficiently problematic, it added to the confusion for, what? Five decades now?

VRS is NOT SWP, even though several tens of thousands of pilots were taught to interchange the terms. Knowing the difference is the important point. It's especially important as you may expose yourself to conditions that could lead to bad outcomes from either or both in professional flying while in sanitary school settings you may not, or you may be taught by the book answers that aren't inclusive of ALL options. Example- my last several recurrent sessions did not include anything that wasn't in the FAA syllabus- until I asked for demonstration, practice. Vuichard recovery technique chief among them. The check airman was very familiar with it, he was a long line mountain pilot and an exceptional teacher...

26th Nov 2017, 17:23
So, I mess up my pre-flight planning and make an approach to a OGE hover a few hundred pounds above my RFM MAUM for OGE hover at that temp and pressure. I am aiming for a 70' hover to confirm my ground position before descending vertically into a smallish LS with some obstacles around it.

As I get to 70' in a level decel and start to lose translational lift, I raise the lever and pull as much power as the engine will give me but the aircraft starts to sink - I raise the lever some more but the engine has topped out and I hear the Nr start to decay and I keep going down - I am clearly going to hit the ground but why?

Is the answer

a - I have settled with power because I don't have enough to hover OGE but tried it anyway?

or b - I have entered VRS because aerodynamics weren't on my side today?

I have ended up in an overpitching state trying to arrest the descent but I am going down with full power applied and the Nr decaying. I haven't caught up with my downwash because the RoD is fairly low and I might just be saved from a hard impact by ground effect.

On a different day, I have done my pre-flight planning perfectly and I know I have OGE hover performance plus some in hand for the wife and kids. I make my approach with a slight tailwind that I didn't notice and I end up a bit steeper on finals to my OGE hover point than I intended. I have some forward speed when I look out of the window so I accept the higher rate of descent thinking that a combination of flare effect and power will sort things out near the bottom. I feel a sink and some vibration I don't much like so I grab a handful of lever - the aircraft shakes some more and sinks a bit faster so I add more collective. Suddenly I feel as though I am falling out of the sky and the ground is coming up really fast. I am clearly going to hit the ground but why?

Is the answer

a. I have run out of power and am therefore settling with it?

or b - I have entered VRS because I didn't realise I was downwind and let the external references fool me into thinking I still had forward airspeed on? I allowed a high RoD to develop with very low airspeed and tried to recover with lever. I may or may not end up with max power applied and I might even get to the point where I get Nr decay as well but that is a symptom a long way down the list and not the cause of my problem.


There may still be some who can't tell the difference and all I can say is I don't want to go flying with you.

r22butters
26th Nov 2017, 18:58
So, I mess up my pre-flight planning and make an approach to a OGE hover a few hundred pounds above my RFM MAUM for OGE hover at that temp and pressure. I am aiming for a 70' hover to confirm my ground position before descending vertically into a smallish LS with some obstacles around it.

As I get to 70' in a level decel and start to lose translational lift, I raise the lever and pull as much power as the engine will give me but the aircraft starts to sink - I raise the lever some more but the engine has topped out and I hear the Nr start to decay and I keep going down - I am clearly going to hit the ground but why?

Is the answer

a - I have settled with power because I don't have enough to hover OGE but tried it anyway?

or b - I have entered VRS because aerodynamics weren't on my side today?

I have ended up in an overpitching state trying to arrest the descent but I am going down with full power applied and the Nr decaying. I haven't caught up with my downwash because the RoD is fairly low and I might just be saved from a hard impact by ground effect.

On a different day, I have done my pre-flight planning perfectly and I know I have OGE hover performance plus some in hand for the wife and kids. I make my approach with a slight tailwind that I didn't notice and I end up a bit steeper on finals to my OGE hover point than I intended. I have some forward speed when I look out of the window so I accept the higher rate of descent thinking that a combination of flare effect and power will sort things out near the bottom. I feel a sink and some vibration I don't much like so I grab a handful of lever - the aircraft shakes some more and sinks a bit faster so I add more collective. Suddenly I feel as though I am falling out of the sky and the ground is coming up really fast. I am clearly going to hit the ground but why?

Is the answer

a. I have run out of power and am therefore settling with it?

or b - I have entered VRS because I didn't realise I was downwind and let the external references fool me into thinking I still had forward airspeed on? I allowed a high RoD to develop with very low airspeed and tried to recover with lever. I may or may not end up with max power applied and I might even get to the point where I get Nr decay as well but that is a symptom a long way down the list and not the cause of my problem.


There may still be some who can't tell the difference and all I can say is I don't want to go flying with you.

This first one is called Full Throttle, which if you continue pulling, will lead to Low-rpm Rotor Stall, which would most likely happen before you reach settling with power (vortex ring state)!

In the second one you have clearly induced settling with power (vortex ring state) because you chose to ignore the warning signs and began settling into your own downwash!

Perhaps if we gave you all a Full Throttle Lite that would end your confusion?:ugh:

26th Nov 2017, 20:39
R22butters - if you don't want to learn (and possibly save your life) then carry on.

The first one is a classic for underpowered helos like the R22 - you end up with the lever under your armpit and hitting the ground hard - usually without getting anywhere near rotor stall - it is a function of poor piloting skills and only a partial decay since the engine is still pushing max power - it's not like an EOL where there is no power. It is this scenario that is often attributed to VRS when it absolutely is not the case.

The second one is where your confusion arises because you can't see that you haven't reached a power limit - it is simply VRS.

newfieboy
26th Nov 2017, 22:23
Err...TC
No there is no link to God, being a competent safe longline pilot. Just thousands of hours doing it for real.
My question was pretty simple, here I'll rephrase it. How much experience you got in the mountains,(not the UK titties) on a line doing production stuff, single pilot. If I was a betting man I would say Zero!!!
Merry Christmas and all the best for the New Year. I'm outta here going to go on a drill job, just packing my bags....ooh longline TC. Guess I'm a God. Funny that my bday is on Xmas Day....!!!

Ascend Charlie
27th Nov 2017, 00:00
Butters, you really have NFI.

Listen to the old heads, it might help your own head to get a bit older so that after you save up for your next half hour in an R-22, you might survive it.

r22butters
27th Nov 2017, 00:45
R22butters - if you don't want to learn (and possibly save your life) then carry on.

The first one is a classic for underpowered helos like the R22 - you end up with the lever under your armpit and hitting the ground hard - usually without getting anywhere near rotor stall - it is a function of poor piloting skills and only a partial decay since the engine is still pushing max power - it's not like an EOL where there is no power. It is this scenario that is often attributed to VRS when it absolutely is not the case.

The second one is where your confusion arises because you can't see that you haven't reached a power limit - it is simply VRS.

Agreeing with your lack of understading will not save my life!

,...and the 22 is not underpowered! In fifteen years of flying it I have yet to reach full throttle!

Butters, you really have NFI.

Listen to the old heads, it might help your own head to get a bit older so that after you save up for your next half hour in an R-22, you might survive it.

I just recently passed my twelfth flight review, I think I'll be just fine!:hmm:

Lonewolf_50
27th Nov 2017, 01:48
You need to understand that the terminology "power settling" and "settling with power" was used in the US Army about before you knew how to hover. Before I did, for sure, and a hell of a lot of people were brought up with that phrasing as the basic distinction between to different problems that can make you fall.

What was then called Power settling is what I would now call "Power Required Exceeds Power Available" (Sadly, PREPA has not yet caught on as the acronym of choice).
Settling with Power was phrased that way since your condition was similar but different, and lethally so: "you have power" (so the above isn't the problem) but you are still settling/falling. (We now call that condition VRS here in the States in most places I've been).
Your crap about "college drop out" only shows your ignorance.
I was taught the above in flight school (and yeah, it was easy to confuse the two terms) in the early 80's, but one of the things going on in the profession as people trying to make more sense of what "settling with power" is. In the USN, as I recall, the collective wisdom began to call it Vortex Ring State in the late 80's/early 90's. Not sure what the Army's teaching anymore, but in the Navy VRS had displaced "settling with power" to describe that problem in low speed flight ... because it can cause a crash if you don't know what your aircraft is doing and what you need to do about it.

There are a variety of other discussions on this topic here at PPRuNe that I suggest you read. For one reason or another, wind up artists like TC and some others try to make a big production out of an archaic bit of terminology from the past. Nick Lappos made a point late in this thread about the terminology mismatch (http://www.pprune.org/rotorheads/116124-vortex-ring-settling-power-merged.html?highlight=Vortex+Ring+State). There isn't actually a concrete standard phrasing, and more's the pity. Read that thread: there are some very good points for learning in that thread from a few people who understand that rotary wing problem.

Current teaching regarding VRS calls it VRS.

I am about tired of the so called professionals continually engaging in this pissing contest about VRS versus the problem of running out of Nr when power available has topped out, and who calls it what.

My suggestion: grow up, or shut up.

r22butters
27th Nov 2017, 03:19
You need to understand that the terminology "power settling" and "settling with power" was used in the US Army about before you knew how to hover. Before I did, for sure, and a hell of a lot of people were brought up with that phrasing as the basic distinction between to different problems that can make you fall.

What was then called Power settling is what I would now call "Power Required Exceeds Power Available" (Sadly, PREPA has not yet caught on as the acronym of choice).
Settling with Power was phrased that way since your condition was similar but different, and lethally so: "you have power" (so the above isn't the problem) but you are still settling/falling. (We now call that condition VRS here in the States in most places I've been).
Your crap about "college drop out" only shows your ignorance.
I was taught the above in flight school (and yeah, it was easy to confuse the two terms) in the early 80's, but one of the things going on in the profession as people trying to make more sense of what "settling with power" is. In the USN, as I recall, the collective wisdom began to call it Vortex Ring State in the late 80's/early 90's. Not sure what the Army's teaching anymore, but in the Navy VRS had displaced "settling with power" to describe that problem in low speed flight ... because it can cause a crash if you don't know what your aircraft is doing and what you need to do about it.

There are a variety of other discussions on this topic here at PPRuNe that I suggest you read. For one reason or another, wind up artists like TC and some others try to make a big production out of an archaic bit of terminology from the past. Nick Lappos made . There isn't actually a concrete standard phrasing, and more's the pity. Read that thread: there are some very good points for learning in that thread from a few people who understand that rotary wing problem.

Current teaching regarding VRS calls it VRS.

I am about tired of the so called professionals continually engaging in this pissing contest about VRS versus the problem of running out of Nr when power available has topped out, and who calls it what.

My suggestion: grow up, or shut up.

So sick of people telling me what they learned back in the day! You know when I was in college Pluto was still the ninth planet and the very edge of our system, now there's a whole lot more out there and its been demoted to dwarf planet! Times change, get used to it!

What you would call PREPA I would call FTS, full throttle stupid, whoopie we both have our own ideas and acronyms no one care about!

As for "settling with power", I'm with the Helicopter Flying Handbook's glossery, "see vortex ring state"!

Now as much fun as its been arguing with you internet know-it-alls, vacation's over and its time to get back to the real world, so enjoy thinking you're right and the textbook is wrong, 'cause in the end no one really cares!

I have experienced the vortex ring state in the real world and afterwards the guy next to me said, "good job with that settling with power recovery"! So, what do ya know, I'm not the only one who belives the textbook!

Butters has left the building!

megan
27th Nov 2017, 06:00
Does anyone know if Prouty had anything to say on the subject? If so, be interested.

27th Nov 2017, 07:59
I am about tired of the so called professionals continually engaging in this pissing contest about VRS versus the problem of running out of Nr when power available has topped out, and who calls it what. Lonewolf - you acknowledge there is a difference between VRS and running out of power - the problem is what to call it.

In Canada and UK there isn't a problem - we refer to the latter as SWP since it perfectly describes the phenomenon.

Those taught in the US don't seem to want to break away from the erroneous use of SWP to describe VRS.

Yes, I know SWP isn't defined anywhere (other than being used as a synonynm for VRS) but VRS doesn't need another name, especially when there are similar situations - with different causes - that can cause problems at low speed.

I'm not trying to piss on anyone - just trying to highlight the difference, especially since SWP (or running out of power if you prefer) is far more common than VRS.

The acid test is that you can get VRS without SWP (no Nr decay) even though SWP can lead to VRS if no adequate recovery is initiated - maybe that is where the confusion for the US Mil arose.

ShyTorque
27th Nov 2017, 09:00
More than 25 years ago I was involved in a covert military role which required a "free air" OGE hover by night. OGE in that context meant up to altitudes where oxygen would ideally be carried. We didn't have oxygen so that was one of the things we had to be aware of.

At those altitudes there were no accurate visual references so we had to learn how to achieve a hover on the normal flight instruments. To hold a fixed position over the ground the aircraft had Doppler tied into the artificial horizon, which had a lateral/fore and aft needle presentation similar to ILS on other aircraft (the aircraft we flew didn't have ILS fitted).

A critical instrument was the VSI. The ASI stopped working below 40 kts and we had no performance figures in the manuals; so when the people we were working with wanted maximum altitude, we had to attempt it on a try it and see basis. We were working at the limits of the aircraft's performance (and ours). Once in the hover I used to set maximum continuous power and see if the aircraft was climbing or descending. If it climbed ( it seldom did) I let it do so and find its own maximum altitude. We might be hovering there for a couple of hours.

The part relevant to this discussion is that sometimes we had literally aimed too high and the aircraft simply didn't have enough power to achieve a hover. If we persisted, with airspeed "off the clock", the aircraft would begin to descend, despite full power being applied. I would call this "settling with power". It was recoverable by lowering the nose, flying away, then descending 500 feet or so, then trying again. At no stage was control lost.

However, on one memorable occasion, after a very long night and approaching first light, we were all very tired. The handling pilot momentarily lost his concentration and after a prolonged hover, things suddenly went very badly wrong. I believe the aircraft gained a slight negative airspeed and this was coupled with an increasing descent, despite full power. The aircraft suddenly began randomly pitching nose up and down (nose above and below the horizon) and rolling left/right and I noticed the VSI needle had hit the bottom stop (2500 fpm). I called "Airspeed, Airspeed!" The HP didn't respond at first, so I repeated the call and "assisted" him to apply full forward cyclic. The aircraft was slow to respond but very suddenly did so and we flew away, the ground not far below us. We had lost a lot of altitude, thousands of feet. Now THAT was certainly vortex ring state. The difference being that the aircraft didn't respond to normal control inputs until airspeed was regained.

BOBAKAT
27th Nov 2017, 09:15
We can talk about it for hours, but really the VRS / SWP confusion is an "American debate" for a French pilot ...

The main difference between VRS and SWP is ... the understanding and the good use of abacus.

If you use the Abacus correctly it is impossible to go to SWP ...: ALWAYS you go to SWP with full power (and that's not enough ...)

If you use the Abacus correctly it is possible to go in VRS: Sometimes you reach the VRS conditions with a normal or weak power and inside the curves of the abacus ...

example:

You want to take pictures at 300 ft hovering: You check the abacus and they say : you have the power, to hold the stationary OGE: OK Do it ! If they say you do not have the OGE Hovering, (because of the OAT, the pressure. .. the load) and you still want to do it and get out of the abacus: It's an SWP.

You want to cross the Grand Canyon slowly to take pictures:
If you have the power and you can hold the IGE that hovers over the edge ... But if you are already in limit, and want to go over the edge, you pass OGE [B] above [/ B] Grand Canyon, you will lose hovering, it's a SWP .....

You make a vertical approach with average power, far from the limits, and the abacus says you have the power to hold the OGE hovering, without problems, BUT you let the rate of descent rise above 300 ft. minute: you CAN enter the VRS

27th Nov 2017, 10:07
We can talk about it for hours, but really the VRS / SWP confusion is an "American debate" for a French pilot ... or an English pilot or a Canadian pilot or pretty much everyone except US pilots.

A whole lot of us are singing from the same hymn sheet here............

JohnDixson
27th Nov 2017, 11:01
Megan: Prouty, Page 102-109 incl tail rotor VRS. Perhaps not complete enough to end this thread. The tailrotor VRS treatment could have included the work on main rotor down wash roll-up in sideward flight as the two tend to meet in that condition ( IGE anyway ). Prouty ends the tail rotor VRS discussion with an AH-64 anomaly for which he writes that the explanation is “ not known “.

chopjock
27th Nov 2017, 11:33
ShyT.
I called "Airspeed, Airspeed!" The HP didn't respond at first, so I repeated the call and "assisted" him to apply full forward cyclic.

I'm not surprised the HP didn't respond at first, he would have had to work out if you were warning of airspeed being too high or too low and pondering whether to pull back or push forward on the stick...

ShyTorque
27th Nov 2017, 12:15
Chop jock, at what sort of airspeed do YOU normally hover?

chopjock
27th Nov 2017, 12:45
SkyT
If I was trying to hover at high altitude without visual references and a non existent ASI, if my co pilot yelled "airspeed" "airspeed" at me I would probably wonder if I should increase or decrease it. On the other hand, if my co pilot yelled "airspeed too low" I would be able to respond quicker and in the correct manner.

RVDT
27th Nov 2017, 13:37
RW Prouty - Helicopter Aerodynamics II

My Suggestion
Pilots use two terms "settling with power" and "power settling" - sometimes interchangeably and sometimes to represent
two different situations. One is the vortex ring condition discussed above. The other is simply entering into a flight condition
where the required power is more than the available power - for instance, finding it impossible to hover at the top of a
mountain that was no trouble to get to with forward speed. I propose dropping both terms and substituting "thrust instability"
for the vortex ring phenomenon and "running out of power" for the other.

A Final Word
I can't explain why re-ingestion comes stronger with rate of descent in the turbulent vortex-ring state, but I don't feel too bad,
knowing what famed aerodynamicist, Theodore von Karman, was reported to have said: "Only God understands turbulence"

It appears that "settling with power" is a generalisation used to cover two different phenomena which was possibly correct.

Was lucky enough to meet Mr Prouty on a couple of occasions - and if you didn't ask dumb questions he would casually talk to you all day.

Enough already?

ShyTorque
27th Nov 2017, 14:58
SkyT
If I was trying to hover at high altitude without visual references and a non existent ASI, if my co pilot yelled "airspeed" "airspeed" at me I would probably wonder if I should increase or decrease it. On the other hand, if my co pilot yelled "airspeed too low" I would be able to respond quicker and in the correct manner.

Chop jock, I'm not sure what point you're trying to make, apart from find fault. To address your criticism:

Firstly, those of us who did this job knew the problems we were likely to experience and knew the calls we needed to make if things went wrong.

Secondly, the ASI wasn't "non existent", but it didn't read below 40 kts, due to pitot static issues and was well known on the type. If you had an instrument rating you would realise that from a hover attitude and zero airspeed it's really not possible to exceed Vne, the other end of the scale. We were all trained to recover from UPs on instruments, but not from fully developed VRS - we were trained to avoid it instead. In this case the HP was slow to realise we had actually entered VRS due to a lack of airspeed coupled with the very high ROD. I must add that it happened very quickly indeed and we were all very tired.

212man
27th Nov 2017, 15:20
Settle down everybody.....

ShyTorque
27th Nov 2017, 15:23
Settle down everybody.....

That's what causes VRS.... :cool:

Thomas coupling
27th Nov 2017, 18:37
Crab said it all really - most of us are almost on the same hymn sheet.
Now that r22 butters has left the building common sense will prevail.

If I said fanny to an american - they would all assume I'm talking about someone's bum!
If I said spanner, they wouldn't understand what that meant.
If I said closet, it would mean a toilet. In america it means cupboard.

So I'm of the opinion that americans or american trained pilots use SWP to often describe (our) VRS.
American trained pilots have never heard of IVRS.
American trained pilots use Power Settling (PS) where others use/mean: SWP.

Perhaps if we based our conversations around these 'langauage differences', we would be able to interprete matters more readily.

Expert helo pilots on this thread - tend to be singing from the same sonnet sheet.......sorry hymn sheet.

The important bit is to get the message of each (SWP/PS/VRS/IVRS) across in a language the ab initio understands and avoids the circumstances that allows any of these to flourish.

Let's not get our knickers / pants in a twist / helix :ouch:

Lonewolf_50
27th Nov 2017, 22:17
American trained pilots have never heard of IVRS.False. I note that your wind up act continues, TC.
That said, Prouty has a decent suggestion.
I propose dropping both terms and substituting "thrust instability" for the vortex ring phenomenon and "running out of power" for the other. Problem is, one has difficulty in putting a genii back into a bottle.


The other issue is to know your aircraft's characteristics thoroughly (as pointed out in numerous threads on this topic previous to this edition).

gator2
28th Nov 2017, 00:15
I must be too simple minded.


If you are going down, and you don't want to, and all you need is more HP (that you don't unfortunately have) then it is SWP.


If you are going down, and you don't want to, and more HP makes it worse, or at least no better, then you are VRS.


If you start out with SWP, and more HP doesn't stop it, you may end up in VRS.


Two terms. SWIP and SWEP. Insufficient power, or excess power.

28th Nov 2017, 06:13
Lonewolf - the trouble with Mr Prouty's suggestion is that the term 'Thrust Instability' is at least as ambiguous as SWP as a description for VRS.

And, since getting the genie back in the bottle won't happen, we will just have to keep having debates like this one to at least highlight to the less experienced that there is a real difference between the two conditions.

Thomas coupling
28th Nov 2017, 08:06
And to think our Royal's have to go through this langauge barrier - now.:ugh:
I bet the words "thrust" and fanny come into it somewhere, no doubt.:eek:

BOBAKAT
28th Nov 2017, 08:12
USA / Great Britain, a whole community only separated by a language....

JohnDixson
28th Nov 2017, 11:54
To our friends in the UK, from the colonies:

Please go to Amazon UK and pick up a copy of:

“ Made in America, An Informal History of American English” by Bill Bryson,2016. L8.99.

All will be revealed.

All kidding aside, it’s a fun read about how a great number of Americanisms originated.

( Less VRS and SWP )

FH1100 Pilot
28th Nov 2017, 14:55
In Post #41, TC writes a fixed-wing analogy to SWP:You are landing your jumbo jet at Heathrow and for that given AUM you decide to apply maximum reverse thrust to prevent yourself running off the runway. But all the reverse thrust available is not sufficient to arrest the AUM in time to keep it on the runway. Your engines aren't powerful enough (IN THE REMAINING DISTANCE OFFERED) to arrest your particular AUM.

It is an engine thang! Nothing to do with little green arrows/updraft/alpha.

And see, this is why we Americans seem to be confused. Our FAA would not attempt to put a silly name on such a thing other than "Pilot Stupidity." Running off the end of a too-short runway doesn't deserve it's own term of excusability, if you will. You exceeded the performance limitations of your aircraft, simple as that, next!

Getting into a situation in which you're making too steep of an approach or too fast of an approach and the engine does not have enough power to stop you at the bottom is *not* a phenomenon worthy of its own category. It's just a dumb thing to do. You might want to call it "settling with power," and that term certainly seems to fit because blaming things on an invisible boogeyman makes you feel better, but FOREVER we Yanks have called SWP "a condition in which the rotor is re-ingesting its own tip vortices."

Which is why the FAA uses the VRS and SWP terms interchangeably: For all intensive purposes they are the same thing in our book. To hijack one of the term (SWP) and make it mean something else is just...I dont' know...weird.

heliduck
28th Nov 2017, 17:17
” but FOREVER we Yanks have called SWP "a condition in which the rotor is re-ingesting its own tip vortices."

Which is why the FAA uses the VRS and SWP terms interchangeably: For all intensive purposes they are the same thing in our book. To hijack one of the term (SWP) and make it mean something else is just...I dont' know...weird.

FH1100 has just helped me understand something - I was just about to make a smart Alec comment about “but Sir we’ve always said that the earth was flat” but then an epiphany; my understanding while following this thread was that the FAA was not differentiating between VRS & SWP because they didn’t acknowledge the difference, but reading FH1100’s post I now realise that the FAA understands that the rotor disc is reingesting it’s own vortices, they just call it SWP. Yes the disc is in a vortex ring state, they get that, but they refer to the condition based on what the aircraft is doing, not what the rotor disc is doing.

Did I get that right FH1100? It all makes sense to me now, I can relax & feel better knowing that the FAA aren’t aerodynamically challenged.

28th Nov 2017, 18:33
FH1100 - the problem is that what you call pilot stupidity causes lots of accidents and incidents.

When it comes to OGE hover performance, the military solution is to ensure an adequate thrust margin ie that you have more power available than is needed for hover OGE - that way you are unlikely to be embarrassed if you encounter slightly unfavourable conditions or don't fly so brilliantly.

To my knowledge, RFMs for civil aircraft don't include a percentage thrust margin graph, only an OGE hover graph for calculating MAUM for given pressure and temp conditions.

So, no problem as long as your maths and use of the graph are spot on - except that those graphs are for completely still conditions in a stable hover and don't take into account any turbulence or the fact that you need more power to get to the hover than you do to maintain it.

No wonder then that when extracting max performance from your aircraft (for whatever reason) you can get caught out and end up in a gentle descent with the lever up and the Nr slowly decaying (you are overpitching) - the solution is a gentle accel to gain speed.

Compare reacting correctly to this situation (because you know it is SWP and not VRS) to what would happen if you only thought SWP and VRS were the same and therefore had the same recovery ie dump the lever and try to get forward speed.

You can continue to pretend the FAA see-all and know-all but if they truly recognise the difference between running out of power and being in vortex ring, they should say it loud and clear to remove any confusion.

28th Nov 2017, 19:07
Instead the FAA handbook says this Settling With Power (Vortex Ring State)
Vortex ring state describes an aerodynamic condition in
which a helicopter may be in a vertical descent with 20
percent up to maximum power applied, and little or no climb
performance. The term “settling with power” comes from
the fact that the helicopter keeps settling even though full
engine power is applied. talk about a wide spread of conditions and the misleading statement that would lead you to believe you have to have full power applied to be in VRS.

FH1100 Pilot
28th Nov 2017, 19:25
I guess I'm what they call "old school." Look, I learned to fly in a Bell 47 powered by a Franklin engine. In the summer. We spent a lot of time at WOT - literally wide-open throttle. You did NOT allow your engine/rotor rpm to droop on approach. Nobody taught us the modern term of "over-pitching." I guess that came with the Robbies.

By the same token, we learned quickly not to go into really tight or "hover-hole" LZ's where you might not be able to get back out even if you managed to not crash going in.

The thing about "SWP" (as we knew it) was the "disconnect" between the collective and the rate of descent. If you pulled up a bit and the helicopter went down faster, you were re-ingesting your own rotor vortices. Without that bit of evidence, you weren't in SWP. You still might not have enough power to stop at the bottom (if you couldn't get it into ground cushion before the skids hit), but that was your own screw-up, not that of the aircraft.

(Why any self-respecting pilot would continue to pull collective and bleed the rotor rpm down is beyond me. Rotor rpm is life. If you sacrifice it, it's your own damn fault.)

Same thing in governed, turbine helicopters. If moving the collective still modulates the rate of descent, then you're *not* in the FAA's version of SWP.

If you are at a power limit and the helicopter still keeps going down, then if you have the altitude you better get the hell out of there because something bad is about to happen; it's not going to get better. It doesn't matter at this point whether your vortices are above or below the rotor disk - you're about to crash.

Finally, I have never, ever heard of "SWP" being applied to a condition of flight when you're above ETL. If you come in fast, above ETL, and you don't for some reason have enough power to stop at the bottom, it's not SWP. It's you being a dumbass.

r22butters
28th Nov 2017, 20:01
I think I finally see the real issue here? It looks like the Brits and Canadians feel that there aren't a lot of crashes due to entering the vortex ring state, so using the term "settling with power" to describe it, is kind of a waste of a perfectly good term, so they decided to repurpose it?

The problem is, in there incorrect use of these words!

If you have "run out of power" then its not "with power"!

If you have "run out of room", but can still slow down, it may still be "with power", but its not "settling"!

Perhaps you should spend more time teaching your pilots to start slowing down sooner, instead of coming up with names for what happens when they don't!

Sorry for coming back in, but I really had to pee! Besides, the mods probably won't even post this! :{

28th Nov 2017, 21:29
Butters If you have "run out of power" then its not "with power"! outstanding logic, no wonder you are struggling with this concept:ugh:
If you have run out of power, you are at max power so it most certainly is 'with power'.

FH1100 - If you are at a power limit and the helicopter still keeps going down, then if you have the altitude you better get the hell out of there because something bad is about to happen; it's not going to get better. It doesn't matter at this point whether your vortices are above or below the rotor disk - you're about to crash. completely agree - it is just about recognising why and not trying to enter auto to get out of VRS when all you need is a few knots of airspeed to get above ETL again.

(Why any self-respecting pilot would continue to pull collective and bleed the rotor rpm down is beyond me. Rotor rpm is life. If you sacrifice it, it's your own damn fault.) again, completely agree but, just like CFIT, supposedly self-respecting pilots seem to manage it.

Whatever we choose to call the scenarios - prevention is far better than cure in both cases but that is made more difficult if they are rolled in to one broad-brush term.

These are both conditions you or I would recognise instantly and recover appropriately and instinctively - plenty out there who wouldn't.

r22butters
28th Nov 2017, 23:01
Butters outstanding logic, no wonder you are struggling with this concept:ugh:
If you have run out of power, you are at max power so it most certainly is 'with power'.


Yes, the engine is running, and thus producing power, but by that logic you could call a normal landing, "settling with power"!

You've been banging your head against that wall too much!:rolleyes:

The term "with power" means "with power available", not simply, with the engine running!

Being at max power by itself will not cause you to settle. However, if max power is not enough, then you will begin to settle due to a lack of additional "power available"! It is not called "settling with power" because you have no more power available!

If you did have more power available the only way you would start to settle is because you have entered the vortex ring state, which is why we call it settling "with power". You have power available, but are still settling!

Just when I think I'm out, they drag me back in!

Devil 49
28th Nov 2017, 23:16
(Pull your pants up, Butters!)

There is a difference between SWP, "over-pitching" (whatever that is) and VRS. Each of these may be whatever the test-giver wants it to be. Give that answer.
Know what each is and have a plan to deal with eventualities as required to assure your survival when you are actually flying.

VRS? When the airspeed indicator bottoms out and the little orange yarn on the nose of an Astar starts dancing I have to be descending real, real slow. If it twitches or acts like it wants to twitch and that isn't part of my plan- abort and plan a better way in.

SWP? Know you're heavy and plan for a run-on or a fly out, and fly that profile. Or don't do it at all. It's easier to make a couple trips with an intact helo than it is to recover a broken one.

"Over-pitching"? Airplane drivers say "airspeed, altitude and ideas, never run out of one without lots of the others". Lack of NR makes it a moot point.

r22butters
29th Nov 2017, 00:17
(Pull your pants up, Butters!)


Now you know I can't do that Wally!

,...not until every helislave is free to take his lunch break!:* :(

BOBAKAT
29th Nov 2017, 02:32
One of the perfect example of SWP it is a few years ago a 747 Captain, freshly dual rated on helicopters . One day he fly with friends on an Alouette 2 ( turbine engine remember..) He check the weight and balance, check the abacus with Zp and OAT : everything is limit, but ok !
Full passengers, no doors but just at limit on the MTOW, smooth take off on the limit off power and climbing at 500 ft...few minutes later, one passengers ask him to make an hovering in front of his house to take picture.
The Captain say OK ! He slow the speed until stop at 300ft and....Surprise, the helicopter settling with power...and finish in a pond, nobody hurt ...

Why ?
He take off at the power limit IGE, In Ground Effect = Right !
Few minutes later and few liters of kerozen burned but not enough to change the chart......
He stop (try to stop ) his helicopter OGE : Out Ground Effect...FAULT ! he don't check the abacus for OGE, only IGE...
He was a young pilot on helicopter and don't feel the limit when he reach the hovering. If he can , it was easy to escape, just take some speed....
If you follow a French helicopter Course, you learn the hovering power difference between IGE and OGE is around 7% ( or 7% oflift weight capacity)
If you have the power to standard hovering ( 5 ft) IGE at 100%, that's really at the limit but enough for take off...BUT if you want to make an hovering OGE, you need 107% at the same place ( Zp/OAT ) and same load...
If you don't have the 7%....You go sure in SWP...
For sling or the hoist, if the charge weight augmentation exceed the max power available, you know it immediatly ! : the NG (turbine engine) NR ( piston engine) decrease, when you want to lift more than you can.
At this point you have 2 choice ! ....
You continue to increase the pitch and sure, you go down slowly....
OR
you decrease the pitch a little be , the NG/Nr increase and you reach the OGE hovering... your are safe. End of the story..
No one can talk about VRS, it's only a power story and abacus good reading ;) ....

n5296s
29th Nov 2017, 02:45
Finally, I have never, ever heard of "SWP" being applied to a condition of flight when you're above ETL. If you come in fast, above ETL, and you don't for some reason have enough power to stop at the bottom, it's not SWP. It's you being a dumbass.
Another occasion when I regret that PPrune doesn't have a "like" button!

29th Nov 2017, 06:34
No-one said SWP/VRS occurs above ETL................

Butters Just when I think I'm out, they drag me back in! feel free to stay out since you are either trying to wind people up or just don't understand helicopters very well.

Rotorbee
29th Nov 2017, 07:16
Since TC makes such a fuss about the superiority of Transport Canada I looked up what they have to say:

There are some uninformed pilots who use “settling with power” to describe vortex ring, in fact some publications use the terms interchangeably. Confusion results when symptoms are related that do not describe true vortex ring but rather describe “settling with insufficient power”. This may occur when a pilot attempts to arrest a rapid, low power descent only to find that he has insufficient power available to bring the helicopter to either a hover or a no-hover landing without exceeding the engine limits. However, this is not a vortex ring situation.

Another situation, ‘over-pitching’ is often misinterpreted as vortex ring. This is where the pilot rapidly increases collective considerably and the engine cannot produce enough power to overcome the large, swift increase in drag on the rotor system. The result is that the rotor system quickly slows down and loses efficiency causing the helicopter instantly to sink. Again, this is not vortex ring.

Being called "uninformed" (or in plain English "stupid") is rather arrogant. I thought Canadians were so nice and polite?

Well apparently the Canucks have even more:
Settling with power is when a pilot can not arrest the sink rate after a RAPID, LOW POWER descent. What about a slow, high power flat descent where the pilot isn't able to hover either and falls on the landing spot, bending things giving enough height. That's not settling with power? Does the "may occur" mean, that this is one situation or this is THE situation but it does not always happen?

Over pitching is again something else. You can increase the collective slowly and still over- pitch. There is no need of a swift increase of drag. Anyway, nobody I can think of ever called that SWP nor VRS.

Anyway, after reading Transport Canadas view, I think, instead of having less confusion in the terms, there is even more.

After insulting everybody, they made it even worse.

29th Nov 2017, 09:02
Yes, they haven't really got the wording right at all.

In this sentence This may occur when a pilot attempts to arrest a rapid, low power descent only to find that he has insufficient power available to bring the helicopter to either a hover or a no-hover landing without exceeding the engine limits. However, this is not a vortex ring situation.they didn't need to put 'rapid, low power descent', just the word descent would have been clearer.

Similarly in the overpitching sentence, this This is where the pilot rapidly increases collective considerably and the engine cannot produce enough power to overcome the large, swift increase in drag on the rotor system doesn't need the words 'rapidly, considerably, large or swift' in it

29th Nov 2017, 09:06
So perhaps it should read There are some pilots who use “settling with power” to describe vortex ring, in fact some publications use the terms interchangeably. Confusion results when symptoms are related that do not describe true vortex ring but rather describe “settling with insufficient power”. This may occur when a pilot attempts to arrest a descent only to find that he has insufficient power available to bring the helicopter to either a hover or a no-hover landing without exceeding the engine limits. However, this is not a vortex ring situation.

Another situation, ‘over-pitching’ is often misinterpreted as vortex ring. This is where the pilot increases collective and the engine cannot produce enough power to overcome the increase in drag on the rotor system. The result is that the rotor system slows down and loses efficiency causing the helicopter to sink. Again, this is not vortex ring.

Perhaps it could also add that overpitching is often experienced following the 'settling with insufficient power' as described in the first paragraph.

Rotorbee
29th Nov 2017, 09:34
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.

fijdor
29th Nov 2017, 21:42
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

Rotorbee
30th Nov 2017, 07:16
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.

30th Nov 2017, 11:51
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.

Thomas coupling
30th Nov 2017, 15:06
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?

Rotorbee
30th Nov 2017, 15:14
Pst ... is he gone?

ShyTorque
30th Nov 2017, 15:33
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. ;)

fijdor
30th Nov 2017, 15:38
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

30th Nov 2017, 15:53
Shy - I just got a link to a CAA safety Sense leaflet which mentioned VRS but only briefly.

Robbo Jock
30th Nov 2017, 16:24
But that does provide a link to this (http://http://www.ead.eurocontrol.int/eadbasic/pamslight-1FF23CBE2F627ACBEC1D9E460671A441/7FE5QZZF3FXUS/EN/AIC/P/020-2010/EG_Circ_2010_P_020_en_2010-05-20.pdf)

n5296s
30th Nov 2017, 16:38
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).

FH1100 Pilot
30th Nov 2017, 20:01
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.

30th Nov 2017, 21:54
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.

Tailstinger
30th Nov 2017, 22:07
...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)

Rotorbee
1st Dec 2017, 06:16
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 ...

1st Dec 2017, 07:57
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.:ok:

Robbo Jock
1st Dec 2017, 08:56
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 (http://http://www.nats-uk.ead-it.com/public/index.php%3Foption=com_content&task=blogcategory&id=161&Itemid=58.html) then scroll down to Vortex Ring (under 2010). It's a UK Aeronautical Information Circular, Pink 020/2010

ShyTorque
1st Dec 2017, 09:14
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.

Rotorbee
1st Dec 2017, 09:31
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.

Thomas coupling
1st Dec 2017, 09:34
http://www.ead.eurocontrol.int/eadbasic/pamslight-CE0CCA1C74FB5A3530056B2FD21A9B3E/7FE5QZZF3FXUS/EN/AIC/P/020-2010/EG_Circ_2010_P_020_en_2010-05-20.pdf


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/eadbasic/pamslight-CE0CCA1C74FB5A3530056B2FD21A9B3E/7FE5QZZF3FXUS/EN/AIC/P/020-2010/EG_Circ_2010_P_020_en_2010-05-20.pdf

Thomas coupling
1st Dec 2017, 10:02
From the Chief Instructor - Robinson Helicopters.

“Settling With Power”

In the U.S., there seems to be a great deal of confusion on whether the vortex ring state should be properly or improperly referred to as “settling with power.” The controversy stems from a condition completely different from the vortex ring state, in which engine power required exceeds engine power available.

Over the years, various aviation organizations have used conflicting terminology in discussing these very different conditions.

In the 1950s, the U.S. Navy referred to the vortex ring state as “power settling” and used the term “settling with power” for the power-available-vs.-power-required situation. Not wanting to let the Navy set the standard, the U.S. Army reversed the terminology in the 1960s. Army pilots in Vietnam used the term “settling with power” to refer to the vortex ring state and “power settling” when they were trying to get out of a tight landing zone with too many troops onboard.

The FAA uses “settling with power” in its discussion of vortex ring state in both the Rotorcraft Flying Handbook and the Practical Test Standards (probably because there are more former Army pilots in the FAA than former Navy pilots).

Outside the U.S., the picture is much clearer; for the most part, the term used is “vortex ring state.”

I say, let’s call it what it is—the “vortex ring state,” not some vague term that has different meanings to different pilots.—Tim Tucker

Unfortunately he then spoils it all by supporting the Vuichard technique.

Lonewolf_50
1st Dec 2017, 12:44
TC your UK source is simply wrong.
The usual American term for this condition is 'power settling', a description that sums up the potential predicament for the unwary pilot. Nope. Not correct.


Mr Tucker provided a nice summary, however to correct his little anecdote, since I was trained by the Navy (and Marines) in the early 80's, by the early 1980's the Navy was teaching the same terms that Mr Tucker attributes to the Army.
Not wanting to let the Navy set the standard, the U.S. Army reversed the terminology in the 1960s. Army pilots in Vietnam used the term “settling with power” to refer to the vortex ring state and “power settling” when they were trying to get out of a tight landing zone with too many troops onboard.
The FAA uses “settling with power” in its discussion of vortex ring state in both the Rotorcraft Flying Handbook and the Practical Test Standards (probably because there are more former Army pilots in the FAA than former Navy pilots).Sadly for his speaking somewhat outside of his experience, Mr Tucker has never bothered to read Navy flight training instructions.
For example:
2. Do not let the helicopter hover on the glide slope prior to the intended point of landing, as the risk of entering the vortex ring state will be greatly increased.
and later in paragraph 4
a waveoff shall be initiated to avoid the possibility of entering the vortex ring state. See Vortex Ring State, TH-57 NATOPS, Part IV or Chapter 11.
Source is the current Navy training manual for the TH-57 (a variant of the Bell 206), or current as of 2015.
NAVAL AIR TRAINING COMMAND NAS CORPUS CHRISTI, TEXAS CNATRA P-457 Rev (01-15) Pages 4-30 and 4-31.

The TH-57 NATOPS manual addresses vortex ring state, as does the ground training in basic helicopter aero.

You and quite a few others are simply wrong, due to being about 30 years out of date in what you think is true about what someone else teaches.


I wish to salute crab, and completely agree that in getting people to think about this, regardless of these bun fights over terms, we hope that rotary wing aviatiors will know the difference and know what to do about:
What VRS is, how one may approach or get into VRS in real flying, and how to avoid/prevent/deal with it.
The problem of "Power Required Exceeds Power Available" and how to avoid that creating problems for you when flying.
I would also like to salute you, TC, for your long standing rants on VRS because whatever silly bickering goes on, you have never let up on the importance of making sure it never bites you. In aid of that, one has to know the phenomenon, know when one is exposed to that risk, and how to dealing with entry into it (ie, get out of this before it gets worse!).


On that we can all surely agree.

ShyTorque
1st Dec 2017, 15:17
I agree. There is a similar situation in the fixed wing world, albeit not about the terminology used. The PPL syllabus no longer includes fully developed spinning and recovery, but concentrates on how to avoid spinning in the first place.

That argument has been going on for about thirty years and rumbles on just like this one.

r22butters
1st Dec 2017, 16:32
All throughout flight school as well as with my twelve flight reviews so far, I have never heard the term "power settling"! The only place I have ever heard that term is on the internet from old military pilots.

As for the condition of "power required exceeding power available", that is brought up during the SFAR 73 discussion of rotor decay, low-rpm rotor stall, low-rpm recovery, and power management, but has no name for itself.

fijdor
1st Dec 2017, 19:49
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).

Rotorbe, I will keep it short since you seem to have a tooth against the Canadians and British and it seems the English language as well so nothing constructive will come out of this.
But just for you I will inform Transport Canada that they could be responsible for the stupefying of future generations of pilots by using words (actually, just one) not appropriate to certain persons (actually, just one) and defining certain conditions (VRS, SWP) that do not fit certain individuals.
Rotorbe, just keep flying circuits around the airport and be careful not to hurt yourself.

JD

r22butters
1st Dec 2017, 21:06
How about this for a univeral term that everyone can enjoy?

"Too Heavy To Hover"

Its even fun to say, "Oh' ****, we're about to TOOTOO!
:ok:

1st Dec 2017, 21:41
Butters All throughout flight school as well as with my twelve flight reviews so far, I have never heard the term "power settling"! The only place I have ever heard that term is on the internet from old military pilots.

As for the condition of "power required exceeding power available", that is brought up during the SFAR 73 discussion of rotor decay, low-rpm rotor stall, low-rpm recovery, and power management, but has no name for itself. then consider this discussion part of your continued aviation education:ok:

Rotorbee
2nd Dec 2017, 05:12
My dear Fijdor I am so sorry, that I have offended you. I can not deny the fact, that English is not my mother tongue. You should hear me speak, my accent is truly horrible. In all the three languages I have to deal with day in day out, I have an accent. Even in German. My French teachers gave up on me early and then I married a francophone woman. Imagine what she has to endure.

What makes you think I don't like the Canadians or the Brits? I do apologise, if I hurt you, while it was meant as a mere joke. A bad one probably. Sorry about that, but that happens when one is not capable of mastering a single language.

I do not like a word? Sorry to hear that, but I think you got that wrong. SWP or VRS, I don't care, as long as I know what we are all talking about. I like the TOOTOO. That goes perfectly with big eyes and a light panic.

While I do like a nice educational flight around the circuit, I cherish more the time I had in the bush, despite having realised not being on the top of the food chain. It is a revelation that all the racket one does, the common grizzly sees you as tinned food. I am all for the silent helicopter, at least then bears don't react like children to the bell of an ice cream truck.
Lately I have discovered that aerobatics is my thing. My stomach tends to disagree and any selfie would require quite a bit of photoshopping to get the face colours partly human. But my instructor says this will get better with time ... with most pilots ... not always ... I might be a rare exception. Despite that, I do understand that you are well beyond my experience level and I can not apologise enough, if I have offended you with my presence on PPRuNe.

You know, Fijdor, in the future, you might want just to ignore my posts. The time you loose while reading my sorry attempts of explaining my thinking, you will not get back. But allow me to read your posts. I find them most interesting.

Since this will be the last post you read from me, I wish you all the best and a the most satisfying time for the rest of your career.