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Condition for Vortex Ring

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Condition for Vortex Ring

Old 27th Nov 2017, 01:00
  #81 (permalink)  
 
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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.
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Old 27th Nov 2017, 01:45
  #82 (permalink)  
 
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Originally Posted by [email protected] View Post
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!

Originally Posted by Ascend Charlie View Post
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!
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Old 27th Nov 2017, 02:48
  #83 (permalink)  
 
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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. 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.

Last edited by Lonewolf_50; 27th Nov 2017 at 03:00.
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Old 27th Nov 2017, 04:19
  #84 (permalink)  
 
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Originally Posted by Lonewolf_50 View Post
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!
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Old 27th Nov 2017, 07:00
  #85 (permalink)  
 
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Does anyone know if Prouty had anything to say on the subject? If so, be interested.
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Old 27th Nov 2017, 08:59
  #86 (permalink)  
 
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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.
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Old 27th Nov 2017, 10:00
  #87 (permalink)  

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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.
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Old 27th Nov 2017, 10:15
  #88 (permalink)  
 
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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
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Old 27th Nov 2017, 11:07
  #89 (permalink)  
 
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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............
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Old 27th Nov 2017, 12:01
  #90 (permalink)  
 
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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 “.

Last edited by JohnDixson; 27th Nov 2017 at 12:35. Reason: Added thought
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Old 27th Nov 2017, 12:33
  #91 (permalink)  
 
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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...
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Old 27th Nov 2017, 13:15
  #92 (permalink)  

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Chop jock, at what sort of airspeed do YOU normally hover?
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Old 27th Nov 2017, 13:45
  #93 (permalink)  
 
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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.
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Old 27th Nov 2017, 14:37
  #94 (permalink)  
 
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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?
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Old 27th Nov 2017, 15:58
  #95 (permalink)  

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Originally Posted by chopjock View Post
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.

Last edited by ShyTorque; 27th Nov 2017 at 16:21.
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Old 27th Nov 2017, 16:20
  #96 (permalink)  
 
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Settle down everybody.....
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Old 27th Nov 2017, 16:23
  #97 (permalink)  

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Originally Posted by 212man View Post
Settle down everybody.....
That's what causes VRS....
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Old 27th Nov 2017, 19:37
  #98 (permalink)  
 
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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
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Old 27th Nov 2017, 23:17
  #99 (permalink)  
 
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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).
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Old 28th Nov 2017, 01:15
  #100 (permalink)  
 
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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.
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