vortex ring alt + vsi
So topend - you are saying that you are right and that the rest of the known helicopter world is wrong.. I'm surprised there is room for your ego in the cockpit
If engineers call VRS 'settling with power' it is because they do not understand the difference between the 2 which is vast. And a 23 year old reference doesn't help your argument that we are slow to embrace new ideas.
There really is a fully developed VRS which will give several thousands of fpmin RoD and it won't go away in 200 feet.
You are either deliberately winding people up by posting b*ll*cks or you really do believe your own theories - which is worrying.
If a lot of R22s crash during mustering I would suggest that maybe it's because letting cowboys fly an aircraft that was designed as a commuter and is always underpowered is not a great idea (even if it is cheap). Excellent manoeuvreability requires lots of excess power, good control power and good control margins, none of which are demonstrated by the R22.
If engineers call VRS 'settling with power' it is because they do not understand the difference between the 2 which is vast. And a 23 year old reference doesn't help your argument that we are slow to embrace new ideas.
There really is a fully developed VRS which will give several thousands of fpmin RoD and it won't go away in 200 feet.
You are either deliberately winding people up by posting b*ll*cks or you really do believe your own theories - which is worrying.
If a lot of R22s crash during mustering I would suggest that maybe it's because letting cowboys fly an aircraft that was designed as a commuter and is always underpowered is not a great idea (even if it is cheap). Excellent manoeuvreability requires lots of excess power, good control power and good control margins, none of which are demonstrated by the R22.
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crab,
I fully agree with you - in the US the terms are used (improperly) interchangeably, even in texts. If you want proof, here is an entire Army that has the confusion:
http://www.dynamicflight.com/aerodyn...ettling_power/
The best definitions (IMHO):
Vortex Ring State [note - all ROD figures are for light training helos, turbines will have much higher VRS onset RODs]- when the aircraft forward speed is slow enough (below 12 knots) and descent is steep enough (faster than 700 fpm) that the rotor begins to consume its own downwash. In VRS, the torque oscillates and the aircraft bumps, pitches and rolls. In spite of pilot lore, VRS cannot be sustained at high rates of descent because beyond about -1200 fpm, the rotor is in autorotation, and not anywhere near VRS.
Settling with Power (SWP)- when the engine produces less power than the aircraft needs at the weight, altitude and hover condition. The aircraft bogs down, descends and is unrecoverable unless accelerated above translational lift. In bad cases the rotor rpm is pulled down by the enthusiastic pilot so that the tail rotor can also be swamped and a yaw can develop.
Why do pilot confuse the two? because virtually ALL VRS demos are began by descending slowly from an OGE hover, where the instructor is inducing settling with power by not raising the collective enough to stop the descent. In the typical training scenario, the instructor is demonstrating SWP at the onset, then as the ROD builds enough, he is showing VRS, then as the ROD goes to astronomical values (pilots love to wet their pants and brag about 4000 fpm) the instructor is actually demonstrating a vertical autorotation.
Myths about VRS:
Myth 1) VRS makes the aircraft descend so rapidly that the only way to recover is to dive out of it. Not true, if there is lots of altitude, the aircraft can simply be allowed to descend to vertical autorotation, where the rotor is eating clean air, and is powered by the descent. For light helos, autos are at about 1500 fpm, for heavier ones, 2 to 3000 fpm. For helos with lots of power, you can raise the collective while in VRS and motor up out of it. VRS typically raises the power required by something like 10 to 40% so this trick is not useful unless you are in a SkyCrane or a Black Hawk.
Myth 2) VRS causes the rotor to become dead aerodynamically, and if you don't do something, you will die. Only true low to the ground, the natural state of the helo in VRS is to accelerate downward until the rotor is eating clean air in autorotation.
Myth 3) If you descend in a hover at 300 fpm, you will get VRS. Not true, no helo will experience VRS at such low descents unless the pilot does nothing and lets the descent increase to real VRS speeds. At 300 fpm descent, the pilot is actually entering an artificially induced SWP regime, where the power is kept purposefully too low, and the descent is allowed to build.
Myth 4) High altitude or high gross weight makes VRS more likely - NOT true, the opposite is true, but since high weight and altitude make SWP more likely, it is easier to demonstrate the classic SWP becomes VRS becomes Autorotation demonstration that is labeled VRS by instructors and worshiped by students.
Myth 5) VRS occurs often and is a cause of many helo accidents. Not a chance, the conditions are very far away from where we operate (700 fpm downward, less than 12 knots). Most accidents where the VRS label is applied are mis-identified by the investigators, and are actually the much more common, much more dangerous SWP.
To recap: VRS is not what your instructor showed you, or at lease not all that he showed you. He demonstrated a complex SWP entry into VRS followed by a screaming vertical autorotation. In real life, the three distinct pieces of what he showed you are separate, controllable and in fact, very predictable.
I fully agree with you - in the US the terms are used (improperly) interchangeably, even in texts. If you want proof, here is an entire Army that has the confusion:
http://www.dynamicflight.com/aerodyn...ettling_power/
The best definitions (IMHO):
Vortex Ring State [note - all ROD figures are for light training helos, turbines will have much higher VRS onset RODs]- when the aircraft forward speed is slow enough (below 12 knots) and descent is steep enough (faster than 700 fpm) that the rotor begins to consume its own downwash. In VRS, the torque oscillates and the aircraft bumps, pitches and rolls. In spite of pilot lore, VRS cannot be sustained at high rates of descent because beyond about -1200 fpm, the rotor is in autorotation, and not anywhere near VRS.
Settling with Power (SWP)- when the engine produces less power than the aircraft needs at the weight, altitude and hover condition. The aircraft bogs down, descends and is unrecoverable unless accelerated above translational lift. In bad cases the rotor rpm is pulled down by the enthusiastic pilot so that the tail rotor can also be swamped and a yaw can develop.
Why do pilot confuse the two? because virtually ALL VRS demos are began by descending slowly from an OGE hover, where the instructor is inducing settling with power by not raising the collective enough to stop the descent. In the typical training scenario, the instructor is demonstrating SWP at the onset, then as the ROD builds enough, he is showing VRS, then as the ROD goes to astronomical values (pilots love to wet their pants and brag about 4000 fpm) the instructor is actually demonstrating a vertical autorotation.
Myths about VRS:
Myth 1) VRS makes the aircraft descend so rapidly that the only way to recover is to dive out of it. Not true, if there is lots of altitude, the aircraft can simply be allowed to descend to vertical autorotation, where the rotor is eating clean air, and is powered by the descent. For light helos, autos are at about 1500 fpm, for heavier ones, 2 to 3000 fpm. For helos with lots of power, you can raise the collective while in VRS and motor up out of it. VRS typically raises the power required by something like 10 to 40% so this trick is not useful unless you are in a SkyCrane or a Black Hawk.
Myth 2) VRS causes the rotor to become dead aerodynamically, and if you don't do something, you will die. Only true low to the ground, the natural state of the helo in VRS is to accelerate downward until the rotor is eating clean air in autorotation.
Myth 3) If you descend in a hover at 300 fpm, you will get VRS. Not true, no helo will experience VRS at such low descents unless the pilot does nothing and lets the descent increase to real VRS speeds. At 300 fpm descent, the pilot is actually entering an artificially induced SWP regime, where the power is kept purposefully too low, and the descent is allowed to build.
Myth 4) High altitude or high gross weight makes VRS more likely - NOT true, the opposite is true, but since high weight and altitude make SWP more likely, it is easier to demonstrate the classic SWP becomes VRS becomes Autorotation demonstration that is labeled VRS by instructors and worshiped by students.
Myth 5) VRS occurs often and is a cause of many helo accidents. Not a chance, the conditions are very far away from where we operate (700 fpm downward, less than 12 knots). Most accidents where the VRS label is applied are mis-identified by the investigators, and are actually the much more common, much more dangerous SWP.
To recap: VRS is not what your instructor showed you, or at lease not all that he showed you. He demonstrated a complex SWP entry into VRS followed by a screaming vertical autorotation. In real life, the three distinct pieces of what he showed you are separate, controllable and in fact, very predictable.
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Good point Shawn in a count of one to five for the time sequence of the airframe vibes, I’d suggest that the sinking feeling first comes in at about number three.
Crab, you must have had god awful day at the office,
If you qualify the rest of the world as four people only on this forum who speak about the deadly characteristics of one helicopter type only, the pommy built sycamore, as the rest of the world then I’d suggest that you’re odds are a bit long.
I’m still keen to find out just what it is that it carries downwards for 8000 feet, a stalled set of blades perhaps?? A single vortex ring bubble it is not.
Regrettably this may be the statistics of the not too distant future, many cowboys are indeed getting themselves PHL’s and helicopters (10 in the NT alone in the last two years) and venturing into our increasingly unregulated commercial world out here and the result of course may be regrettable. However that is off thread. Many ex mustering jocks are flying worldwide with excellent cred.
So as far as ego is concerned I have no idea, I’m still learning.
You obviously know so much about the underrated, over powered, highly manoeuvrable R22 that it’s not worth my while presenting another side. As a commuter, only, you should get out and read more; it might be a commuter in less than five percent of its world market.
As I have said before anyone who under sell the R22’s inventor’s intelligence so much by saying that ALL he was ever designing it for was as a commuter, than they must be indeed a poor judge of character if not downright insulting?
Nick, I think most of your points are in confirmation with mine. Also the entire army you talked about may be same one that gave rise to Manningham’s article because of their “approaching to land crash statistics” over a ten year period.
The highest common denominator being those in calm winds despite a cross section of operations and aircraft (all of which had sufficient power to hover OGE).
It’s a great pity more practice had not been done to prevent that. Remember the important point, done at ab-initio to recognise and avoid is most important, there is no need to try it on later in big aircraft.
The only reason i teach it is because slack instructors have not.
Crab, you must have had god awful day at the office,
you are saying that you are right and that the rest of the known helicopter world is wrong.
If you qualify the rest of the world as four people only on this forum who speak about the deadly characteristics of one helicopter type only, the pommy built sycamore, as the rest of the world then I’d suggest that you’re odds are a bit long.
I’m still keen to find out just what it is that it carries downwards for 8000 feet, a stalled set of blades perhaps?? A single vortex ring bubble it is not.
If a lot of R22s crash during mustering I would suggest that maybe it's because letting cowboys fly an aircraft
Regrettably this may be the statistics of the not too distant future, many cowboys are indeed getting themselves PHL’s and helicopters (10 in the NT alone in the last two years) and venturing into our increasingly unregulated commercial world out here and the result of course may be regrettable. However that is off thread. Many ex mustering jocks are flying worldwide with excellent cred.
So as far as ego is concerned I have no idea, I’m still learning.
that was designed as a commuter and is always underpowered is not a great idea (even if it is cheap). Excellent manoeuvrability requires lots of excess power, good control power and good control margins, none of which are demonstrated by the R22.
You obviously know so much about the underrated, over powered, highly manoeuvrable R22 that it’s not worth my while presenting another side. As a commuter, only, you should get out and read more; it might be a commuter in less than five percent of its world market.
As I have said before anyone who under sell the R22’s inventor’s intelligence so much by saying that ALL he was ever designing it for was as a commuter, than they must be indeed a poor judge of character if not downright insulting?
Nick, I think most of your points are in confirmation with mine. Also the entire army you talked about may be same one that gave rise to Manningham’s article because of their “approaching to land crash statistics” over a ten year period.
The highest common denominator being those in calm winds despite a cross section of operations and aircraft (all of which had sufficient power to hover OGE).
It’s a great pity more practice had not been done to prevent that. Remember the important point, done at ab-initio to recognise and avoid is most important, there is no need to try it on later in big aircraft.
The only reason i teach it is because slack instructors have not.
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TT,
I suggest you stop doing what you are doing because you obviously don't know what you are doing!! I used the Sycamore as an example of early crap blade design (based on a fixed wing) merely to demonstrate that modern design has improved helicopter handling immensely. I've been teaching this **** since 1972 and I think I know what I'm doing (as does Crab et al).
GAGS,
E86
I suggest you stop doing what you are doing because you obviously don't know what you are doing!! I used the Sycamore as an example of early crap blade design (based on a fixed wing) merely to demonstrate that modern design has improved helicopter handling immensely. I've been teaching this **** since 1972 and I think I know what I'm doing (as does Crab et al).
GAGS,
E86
OK Nick now you have confused me (it is easily done) - how do you get to vertical autorotation without lowering the lever? To get into VRS you have to aggravate the incipient condition by applying power thus worsening the root stall and the tip vortex. How can this configuration (presuming you take no recovery action) get you to a windmill brake/autorotative state?
Topend - only eagle mentioned the sycamore and only once, all the other comments have been regarding modern helos.
As for the R22 - with anything other than one person on board it has a woeful power margin unless the fuel tanks are empty or you are in the habit of ignoring the MAP limits. I believe Frank himslef stated that his intention was to produce an affordable helicopter for the masses (a bit like the VW Beetle) - but it gets used for all sorts of other things because it is very cheap to run compared to a turbine helo. I also believe it is used most for training and private use.
Can it be chucked around? yes. But don't try to compare that to really manoeuvreable helicopters like Lynx, Commanche etc. There are hundreds of pilots who think because the rotor doesn't drop off that they are not doing any damage operating the aircraft like that - the R22 was not designed for mustering and you guys only use it because it is cheap.
As for the office - well mine is in a big yellow Sea King and I get to rescue people in it, it's always a good day at the office
) - how do you get to vertical autorotation without lowering the lever? To get into VRS you have to aggravate the incipient condition by applying power thus worsening the root stall and the tip vortex. How can this configuration (presuming you take no recovery action) get you to a windmill brake/autorotative state?Topend - only eagle mentioned the sycamore and only once, all the other comments have been regarding modern helos.
As for the R22 - with anything other than one person on board it has a woeful power margin unless the fuel tanks are empty or you are in the habit of ignoring the MAP limits. I believe Frank himslef stated that his intention was to produce an affordable helicopter for the masses (a bit like the VW Beetle) - but it gets used for all sorts of other things because it is very cheap to run compared to a turbine helo. I also believe it is used most for training and private use.
Can it be chucked around? yes. But don't try to compare that to really manoeuvreable helicopters like Lynx, Commanche etc. There are hundreds of pilots who think because the rotor doesn't drop off that they are not doing any damage operating the aircraft like that - the R22 was not designed for mustering and you guys only use it because it is cheap.
As for the office - well mine is in a big yellow Sea King and I get to rescue people in it, it's always a good day at the office
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crab,
The real question to ask is "How can a helicopter be descending at 3000 fpm and NOT be in windmill brake state?" By definition, VRS can only exist around about 0.7Vi to 1.2Vi (give or take). Here is a plot for a jet ranger, where the true VRS (the dark oval) is clearly between 1000 and 1600 fpm:
http://www.safetycenter.navy.mil/MED...n03/vortex.htm
For a low disk loading helo, the position of the collective in a vertical auto can easily be high enough to be in the powered flight range.
The real question to ask is "How can a helicopter be descending at 3000 fpm and NOT be in windmill brake state?" By definition, VRS can only exist around about 0.7Vi to 1.2Vi (give or take). Here is a plot for a jet ranger, where the true VRS (the dark oval) is clearly between 1000 and 1600 fpm:
http://www.safetycenter.navy.mil/MED...n03/vortex.htm
For a low disk loading helo, the position of the collective in a vertical auto can easily be high enough to be in the powered flight range.
Yes but we are talking about getting into VRS with lever positions so high that without the engine running, the Nr would decay rapidly - it doesn't sound like autorotation to me. If what you say is true then all the stories of aircraft falling out of the sky or taking several thousands of feet to recover are not true and all they had to do was wait and it would fly out by itself. Sorry but I will need a lot more convincing evidence than a Jetranger graph to disprove the accepted theory on VRS
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Crab,
In a descent, you start with a mild powered descent, drop thru VRS and then into auto. I have done maybe 500 of them (for some reason, 0 knot autos is a big deal with the FAA).
The guys who tell tales of dropping at thousands of feet per minute are either in autorotation, or they are kidding (and they aren't kidding!)
In a descent, you start with a mild powered descent, drop thru VRS and then into auto. I have done maybe 500 of them (for some reason, 0 knot autos is a big deal with the FAA).
The guys who tell tales of dropping at thousands of feet per minute are either in autorotation, or they are kidding (and they aren't kidding!)
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Nick,
Would one of the variables not be the amount of power applied, ie, more collective in a governed aircraft? As variable as there are aircraft types.
Thus, if more collective were applied during the mild powered descent just as you are dropping through, the situation would be exacerbated and potentially find a state where there is enough power being developed to stop you dropping through and continuing in VRS.
Could that happen?
Would one of the variables not be the amount of power applied, ie, more collective in a governed aircraft? As variable as there are aircraft types.
Thus, if more collective were applied during the mild powered descent just as you are dropping through, the situation would be exacerbated and potentially find a state where there is enough power being developed to stop you dropping through and continuing in VRS.
Could that happen?
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I think we are still being confused here - to recap - conditions for entry into IVR are 1. low KIAS < 20, 2. ROD > 200ft/min, 3. increasing power from minimum to a lot. What happens next? Witrh collective still under your armpit ROD rapidly increases to in excess of 5000 feet plus, airframe vibration, random yawing. What is happening aerodynamically? Outboard section of blade not producing lift due to ingested vortices increasing induced flow reducing angle of attack, inboard section exceeding stalling angle of attack, decreasing middle section producing insufficient lift. Recovery action - lower lever - yes entering auto even - forward cyclic to "blow" vortices "back" to prevent ingestion. Need lots of AGL. Lesson? Recognise conditions of flight required to reach IVR and take corrective action before fully developed VR is encounted.
Had this discussion with a VERY experienced mate yesterday and it was clear to me that he did not understand the regimes of flight that put him in the danger zone!
GAGS,
E86
Had this discussion with a VERY experienced mate yesterday and it was clear to me that he did not understand the regimes of flight that put him in the danger zone!
GAGS,
E86
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Eagle,
By "IVR" are you referring to Incipient Vortex Ring? If so, yes there is still confusion, because you then go on to describe a developed VRS.
VRS is VRS, I personally believe there are variables which affect its severity and they range exactly between what you describe and what Nick Lappos describes.
I don't understand why anyone would be demonstrating anything other than a recovery at the incipient stage. I don't even believe that is necessary.
By "IVR" are you referring to Incipient Vortex Ring? If so, yes there is still confusion, because you then go on to describe a developed VRS.
VRS is VRS, I personally believe there are variables which affect its severity and they range exactly between what you describe and what Nick Lappos describes.
I don't understand why anyone would be demonstrating anything other than a recovery at the incipient stage. I don't even believe that is necessary.
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HH,
It's like spinning a fixed wing (which when fully developed is actually autorotation) - you demonstrate the flight situation which will get you into it, note the symptoms, demonstrate the recovery methods. What I am trying to do here is let young/inexperienced pilots understand what flight regime MAY lead to IVR/VR. And no I don't demonstrate VR but I do demonstrate IVR.
GAGS,
E86
It's like spinning a fixed wing (which when fully developed is actually autorotation) - you demonstrate the flight situation which will get you into it, note the symptoms, demonstrate the recovery methods. What I am trying to do here is let young/inexperienced pilots understand what flight regime MAY lead to IVR/VR. And no I don't demonstrate VR but I do demonstrate IVR.
GAGS,
E86
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eagle86,
You are just spouting the old myths ("to recap - conditions for entry into IVR are 1. low KIAS < 20, 2. ROD > 200ft/min, 3. increasing power from minimum to a lot."
The attempt here is to describe PRECISELY what VRS is and how to know/control/avoid it. It seems that my points below (post #42) are not clear enough.
Some facts:
It is impossible to get VRS at 200 to 300 feet/min rod.
It is impossible to get VRS at 20 knots airspeed
VRS is not a power-caused problem, it has little to do with power.
Over pitching (SWP) is so often confused with VRS that the two are a mish-mash in most pilot's heads, so we get quotes like eagle86 above. The common training guides are of no help, because they repeat the same mish-mash.
hihover,
The variability for different helos and rotors is tied into the disk loading, where low disk loading rotors have less downwash velocity (Vi) and thus can get VRS at a lower rod. Power has little to do with it, your instructor was confusing VRS with SWP, as does eagle86.
You are just spouting the old myths ("to recap - conditions for entry into IVR are 1. low KIAS < 20, 2. ROD > 200ft/min, 3. increasing power from minimum to a lot."
The attempt here is to describe PRECISELY what VRS is and how to know/control/avoid it. It seems that my points below (post #42) are not clear enough.
Some facts:
It is impossible to get VRS at 200 to 300 feet/min rod.
It is impossible to get VRS at 20 knots airspeed
VRS is not a power-caused problem, it has little to do with power.
Over pitching (SWP) is so often confused with VRS that the two are a mish-mash in most pilot's heads, so we get quotes like eagle86 above. The common training guides are of no help, because they repeat the same mish-mash.
hihover,
The variability for different helos and rotors is tied into the disk loading, where low disk loading rotors have less downwash velocity (Vi) and thus can get VRS at a lower rod. Power has little to do with it, your instructor was confusing VRS with SWP, as does eagle86.
Nick, your posts are quite clear but you are debunking a big urban myth if you are essentially stating that VRS doesn't exist and that the aircraft will get itself into vertical auto if you do nothing after the incipient stage. If all you have to do is wait for the RoD to get to 1500'/min so the vortiex disappears then this is a very major change to accepted theory and I am very sceptical about it.
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crab,
What I am saying is not a change from aerodynamic understanding at all. It is however a major change from the pilot mythology that has been allowed to accumulate, unchecked by anyone who actually understands VRS, for decades.
The article I provided in post 42 is an example, here I also provide the papers of Gordon Leishman from U of MD who, based on the V22 accident, became quite expert on the methods of analyzing the rotor flow:
http://www.glue.umd.edu/~leishman/Aero/vring.html
It is exactly correct to say that when the rotor is descending at 1.3 times Vi there can be NO VRS. When we demonstrate it (I have done so only about 1000 times!) we pass thru that condition (and of course also the .2Vi and 1.0Vi) and call the whole mess VRS.
Can the collective be up to your armpits in auto? Yes, in fact, and a verical auto, it will be fairly high.
What I am saying is not a change from aerodynamic understanding at all. It is however a major change from the pilot mythology that has been allowed to accumulate, unchecked by anyone who actually understands VRS, for decades.
The article I provided in post 42 is an example, here I also provide the papers of Gordon Leishman from U of MD who, based on the V22 accident, became quite expert on the methods of analyzing the rotor flow:
http://www.glue.umd.edu/~leishman/Aero/vring.html
It is exactly correct to say that when the rotor is descending at 1.3 times Vi there can be NO VRS. When we demonstrate it (I have done so only about 1000 times!) we pass thru that condition (and of course also the .2Vi and 1.0Vi) and call the whole mess VRS.
Can the collective be up to your armpits in auto? Yes, in fact, and a verical auto, it will be fairly high.
VRS...SWP...who cares? It's all theoretical anyway. I mean, we never get into those conditions up high. Nope, either/or happens down low, at the bottom of an approach when there may be no time or altitude to recover. Bottom falls out when you're up at a nice, high 5,000' OGE hover? Here's the procedure:
1) Lower collective,
2) Get some airspeed,
3) Land,
4) Change shorts.
Bottom fall out when you're on short-short final to a confined area?
1) Instinctively pull collective all the way up,
2) Say to self (if there is time), "Thiiiiiis is gonna leave a mark,"
3) Wake up in hospital.
Oh, and another thing. Nick sez that it's a physical impossibility to get VRS at a 300 fpm RoD. Oh yeah? It would be nice if we flew inside of computer hard drives...or if we flew in wind tunnels. But we don't, do we? We fly in the outdoors (well, most of us do, except for that Hanna Reich chick, but that was a long time ago). And, owing to the rather chaotic nature of, well, nature, things don't happen with laboratory regularity and precision. The wind outdoors does not always blow consistently horizontally. There are drafts, both up and down. Now, stick with me for a sec', just supposing we're in a OGE hover, coming down at 300 fpm and we get an updraft of 500 fpm? This updraft lasts for, oh, a couple of seconds, tops. The rotor is now "seeing" a RoD of 800 fpm, no? Enough to incite VRS? Impossible? I think NOT!
I have read Prouty (and Proust, but Prouty was harder to understand). I have seen the actual derived-from-test-flights performance chart plots for a certain helicopter (hint in SN). And I know that the behavior (behaviour, if you prefer) of a rotor is erratic and unpredictable in the absolute. Graph plotpoints all over the place, in other words. Within a given range, of course, and the resulting curves are "close enough for government work" but there's always a "flier" or two or three...anomalies which don't get included because we like our graphs to have nice, smooth curves, not jagged, Alpine-like outlines that look like something off a heart-monitor oscilloscope. And, we humans like to "round-off" stuff whereas nature does not always see things that way.
Still, the difference between SWP and VRS is moot, and makes no difference whatsoever to the rotary-wing pilot. If you get into either at exactly the wrong time, it probably won't matter which recovery technique you try to use. And you won't have time to ask yourself, "Heyyyyyy, is this SWP or VRS?"
1) Lower collective,
2) Get some airspeed,
3) Land,
4) Change shorts.
Bottom fall out when you're on short-short final to a confined area?
1) Instinctively pull collective all the way up,
2) Say to self (if there is time), "Thiiiiiis is gonna leave a mark,"
3) Wake up in hospital.
Oh, and another thing. Nick sez that it's a physical impossibility to get VRS at a 300 fpm RoD. Oh yeah? It would be nice if we flew inside of computer hard drives...or if we flew in wind tunnels. But we don't, do we? We fly in the outdoors (well, most of us do, except for that Hanna Reich chick, but that was a long time ago). And, owing to the rather chaotic nature of, well, nature, things don't happen with laboratory regularity and precision. The wind outdoors does not always blow consistently horizontally. There are drafts, both up and down. Now, stick with me for a sec', just supposing we're in a OGE hover, coming down at 300 fpm and we get an updraft of 500 fpm? This updraft lasts for, oh, a couple of seconds, tops. The rotor is now "seeing" a RoD of 800 fpm, no? Enough to incite VRS? Impossible? I think NOT!
I have read Prouty (and Proust, but Prouty was harder to understand). I have seen the actual derived-from-test-flights performance chart plots for a certain helicopter (hint in SN). And I know that the behavior (behaviour, if you prefer) of a rotor is erratic and unpredictable in the absolute. Graph plotpoints all over the place, in other words. Within a given range, of course, and the resulting curves are "close enough for government work" but there's always a "flier" or two or three...anomalies which don't get included because we like our graphs to have nice, smooth curves, not jagged, Alpine-like outlines that look like something off a heart-monitor oscilloscope. And, we humans like to "round-off" stuff whereas nature does not always see things that way.
Still, the difference between SWP and VRS is moot, and makes no difference whatsoever to the rotary-wing pilot. If you get into either at exactly the wrong time, it probably won't matter which recovery technique you try to use. And you won't have time to ask yourself, "Heyyyyyy, is this SWP or VRS?"
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Interesting thread.
In one of my previous lives we did a lot of this type of training for a very good reason: our pilots were at risk and there many SWP/VRS incidents/accidents. We wanted to stop that.
We would get them to take us to 1500-2000' and enter a typical regime of flight (low ROD, low A/S, partial power) and hold it until the a/c would noticeably accelerate down, noting the warning signs it was giving us.
Once well established on the elevator ride down we would recover, generally with forward cyclic. Of particular note was how long and how pronounced the control input needed to be to recover. That was the key as the normal theory of cyclic recovery wasn't telling htem just how much would be required to recover, and how much of an attitude change would result.
The training was effective, they learned a lot. I would say it felt like a VRS not SWP but who am I?
We called it VRS recovery training. We did it in the R22, R44, B206, HU500, and AS350: everything involved in seismic work at the time. The incident rate went way down.
In one of my previous lives we did a lot of this type of training for a very good reason: our pilots were at risk and there many SWP/VRS incidents/accidents. We wanted to stop that.
We would get them to take us to 1500-2000' and enter a typical regime of flight (low ROD, low A/S, partial power) and hold it until the a/c would noticeably accelerate down, noting the warning signs it was giving us.
Once well established on the elevator ride down we would recover, generally with forward cyclic. Of particular note was how long and how pronounced the control input needed to be to recover. That was the key as the normal theory of cyclic recovery wasn't telling htem just how much would be required to recover, and how much of an attitude change would result.
The training was effective, they learned a lot. I would say it felt like a VRS not SWP but who am I?
We called it VRS recovery training. We did it in the R22, R44, B206, HU500, and AS350: everything involved in seismic work at the time. The incident rate went way down.
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FH1100, I think you have it just about right. The academics of the two are almost meaningless in the operators' world.
I'm tending towards SWP being the end result of a VRS when that VRS is not corrected and the aircraft is generating enough lift to sustain the VRS and does not drop through into autorotation. It matters not. They sound the same to me.
I did get it at 4000' in the hover at night but recovery at the first sign of trouble was instinctive and very easy to fly out of.
I'm tending towards SWP being the end result of a VRS when that VRS is not corrected and the aircraft is generating enough lift to sustain the VRS and does not drop through into autorotation. It matters not. They sound the same to me.
I did get it at 4000' in the hover at night but recovery at the first sign of trouble was instinctive and very easy to fly out of.
Fantastic stuff Nick and it made my head hurt - but...even though you are at least a thousand times cleverer than me, there is nothing I can see that supports your argument. In the three single rotor examples, in each case a significant reduction in collective pitch was introduced to create the RoD - there was no opposing application of lever which you would expect a pilot to apply once he got the RoD and vibration associated with incipient VRS.