Zero speed auto > Hover (without gaining airspeed)
Some 'americanisms' need sorting out first before one can answer the Q. Correct me if I'm wrong:
Auto Vs EOL:
When a yank states "auto" he means that the engine(s) is/are OFF. Brits call this an EOL (engine off landing) to differentiate from a brit auto which means power available throughout the manoeuvre (Brit spelling!).
VRS Vs SWP
When a yank says VRS (vortex ring state), they sometimes mean SWP (settling with power). The two of course are completely different phenomena. The former is a state where the pilot has NO control over the machine. The latter is where the a/c remains within its flight envelope and the pilot simply has too little collective margin left to compensate for the ROD at the bottom of a descent.
VRS Vs IVRS
Perhaps not an americanism, perse (french not american!) but sometimes when pilots talk about VRS, they mean the incipient stage where there is still the ability by a pilot to input a control demand and expect a response. As Nick stated earlier - "powering out of VRS"...actually it should read IVRS.
VRS - fully developed is where the pilot and crew (against their wishes) become passengers and aerodynamic forces will decide if control is returned to the pilot (by falling out of the VRS state of their own accord) or not.
Assuming the above:
A yank auto (EOL) cannot experience VRS, because the induced airflow decays as it is being injected (Decaying Nr).
A zero speed auto (EOL) ending in a massive collective input to position it in the hover cannot result in SWP, because there is no 'power'.
An auto with the engine running - ending in a massive collective input to the hover requires well above average skill, judgement and practice. But provided the ROD is inside the a/c's margin for collective recovery (Nr and AUM), then SWP shouldn't develop.
An engine running auto to a full stop in the hover from zero speed wouldnt incur VRS because the immediate onset of VRS is not possible, it wouldnt have time to precipitate.
Observations invited..............................
Auto Vs EOL:
When a yank states "auto" he means that the engine(s) is/are OFF. Brits call this an EOL (engine off landing) to differentiate from a brit auto which means power available throughout the manoeuvre (Brit spelling!).
VRS Vs SWP
When a yank says VRS (vortex ring state), they sometimes mean SWP (settling with power). The two of course are completely different phenomena. The former is a state where the pilot has NO control over the machine. The latter is where the a/c remains within its flight envelope and the pilot simply has too little collective margin left to compensate for the ROD at the bottom of a descent.
VRS Vs IVRS
Perhaps not an americanism, perse (french not american!) but sometimes when pilots talk about VRS, they mean the incipient stage where there is still the ability by a pilot to input a control demand and expect a response. As Nick stated earlier - "powering out of VRS"...actually it should read IVRS.
VRS - fully developed is where the pilot and crew (against their wishes) become passengers and aerodynamic forces will decide if control is returned to the pilot (by falling out of the VRS state of their own accord) or not.
Assuming the above:
A yank auto (EOL) cannot experience VRS, because the induced airflow decays as it is being injected (Decaying Nr).
A zero speed auto (EOL) ending in a massive collective input to position it in the hover cannot result in SWP, because there is no 'power'.
An auto with the engine running - ending in a massive collective input to the hover requires well above average skill, judgement and practice. But provided the ROD is inside the a/c's margin for collective recovery (Nr and AUM), then SWP shouldn't develop.
An engine running auto to a full stop in the hover from zero speed wouldnt incur VRS because the immediate onset of VRS is not possible, it wouldnt have time to precipitate.
Observations invited..............................
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I hate to establish an argument (yea right!) but when you land an autorotation, you go into Powered flight! The concept is that the "power" comes from the rotor inertia, and is applied to make the rotor behave as if the engines were connected. There is no aerodynamic difference between a touchdonw auto in the final landing sequence and a hover touchdown.
If you took a snapshot of the helo at the touchdown phase, you would find the rotor pumping air downward, in mass sufficient enough to develop thrust that is more than the weight of the helicopter (because the rotor is slowing down the vertical speed, and thus accelerating the helo upward). A G meter will read slightly above 1 g when the landing is being accomplished.
If you took a snapshot of the helo at the touchdown phase, you would find the rotor pumping air downward, in mass sufficient enough to develop thrust that is more than the weight of the helicopter (because the rotor is slowing down the vertical speed, and thus accelerating the helo upward). A G meter will read slightly above 1 g when the landing is being accomplished.
Last edited by NickLappos; 22nd Dec 2005 at 19:46.
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Thomas Coupling, I know where you're going when you talk about the "time required to precipitate" but I'm not convinced.
How long is this time to precipitate and how long will you be in the VRS likely conditions? Until those questions are answered I don't think you can make your statement.
In the worst case your ROD in the auto is the highest that puts you in danger of VRS and when you apply full power you can only slow to the minimum ROD that puts you in danger of VRS. Okay, that's a bit of a stretch but pretend you tried to power out of a zero speed hover at 8000' DA, max AUM. In this odd case, how can you say there isn't time? If it's possible in this case, isn't it possible in many others? What if the pilot doesn't use enough power to vertically accelerate out of the condition?
It might make for some interesting research flying if nobody has studied this before.
As far as terminology, very little is standard. It seems that most are using auto or autorotation to indicate when autorotative forces are turning the rotor rather than an engine. Whether this is because the engine is shut down or if the clutch is not engaged is not acknowledged. The EOLs are sometimes called "full autos" or "autos to touchdown" but again, not standardized.
How long is this time to precipitate and how long will you be in the VRS likely conditions? Until those questions are answered I don't think you can make your statement.
In the worst case your ROD in the auto is the highest that puts you in danger of VRS and when you apply full power you can only slow to the minimum ROD that puts you in danger of VRS. Okay, that's a bit of a stretch but pretend you tried to power out of a zero speed hover at 8000' DA, max AUM. In this odd case, how can you say there isn't time? If it's possible in this case, isn't it possible in many others? What if the pilot doesn't use enough power to vertically accelerate out of the condition?
It might make for some interesting research flying if nobody has studied this before.
As far as terminology, very little is standard. It seems that most are using auto or autorotation to indicate when autorotative forces are turning the rotor rather than an engine. Whether this is because the engine is shut down or if the clutch is not engaged is not acknowledged. The EOLs are sometimes called "full autos" or "autos to touchdown" but again, not standardized.
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Matthew,
Please don't confuse ROD in autorotation with ROD in powered flight. In autorotation it is IMPOSSIBLE to get VRS, because there is no rotor downwash. The flow is going UP through the rotor, and is powering the rotation by what is called the "windmill brake state" where the rotor is a pinwheel. Any vortex pattern from the rotor is swept up and away from recirculation. There is no downwash to get captured and recirculated through the rotor, thus no VRS.
When Thomas talks about "not enough time" he is referring to the very brief event at the end of a touchdown autorotation where the rotor is recovered from autorotation to a powered operating state (by your application of collective pitch), with or without engine power applied just prior to touchdown.
I think you are right about the terminology, Autorotation is what the rotor does, engines on, engines off or engines missing (autogyros!)
I don't agree with thomas about the distinction between IVRS and VRS. The loss of control and lack of response to power demands that we experience in underpowered and low control helicopters is not because VRS removes ALL control and climb. It is because VRS removes more than those helicopters have. The data is clear and available to support this. To support Thomas's point though, the distinction is theoretical if you are in a typical training helicopter.
Please don't confuse ROD in autorotation with ROD in powered flight. In autorotation it is IMPOSSIBLE to get VRS, because there is no rotor downwash. The flow is going UP through the rotor, and is powering the rotation by what is called the "windmill brake state" where the rotor is a pinwheel. Any vortex pattern from the rotor is swept up and away from recirculation. There is no downwash to get captured and recirculated through the rotor, thus no VRS.
When Thomas talks about "not enough time" he is referring to the very brief event at the end of a touchdown autorotation where the rotor is recovered from autorotation to a powered operating state (by your application of collective pitch), with or without engine power applied just prior to touchdown.
I think you are right about the terminology, Autorotation is what the rotor does, engines on, engines off or engines missing (autogyros!)
I don't agree with thomas about the distinction between IVRS and VRS. The loss of control and lack of response to power demands that we experience in underpowered and low control helicopters is not because VRS removes ALL control and climb. It is because VRS removes more than those helicopters have. The data is clear and available to support this. To support Thomas's point though, the distinction is theoretical if you are in a typical training helicopter.
Last edited by NickLappos; 23rd Dec 2005 at 11:40.
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Nick,
I didn't mean to imply VRS in an autorotation. The idea here is to transition from autorotation to a powered hover (using engine power, obviously). Once the engine is providing power, the ROD will still be near to what the ROD during autorotation was, hence my reference to the autorotation ROD.
As far as what Thomas Coupling meant, he's the best judge, but he did say, "An engine running auto to a full stop in the hover...[VRS] wouldnt have time to precipitate." Doesn't sound like an auto to touchdown to me.
Mr Selfish,
You\'re right that its a compromise between minimizing ROD and maintaining Nr. If you\'re authorized to do zero speed autos you can determine what ROD and Nr will stabilize and how quickly it will happen. However, the Nr will decay quite quickly if you\'re hovering OGE and to reach a stabilized condition you first need an even lower collective to recover Nr, then increase to maintain.
I did these in a 206 starting at 10 feet - not difficult, increasing to 30 feet - things happening quickly, but minimal loss of Nr...more difficult, then to 50 feet - again things happening quickly, more loss of Nr...most difficult (of what I tried), and finally from about 75 feet...entry the same, time to stabilize, time to peek inside and see what\'s happening...less difficult than 50 and maybe 30 feet. Any higher and I\'d extrapolate that the stabilized condition just lasts longer or you\'d opt to achieve forward flight.
In a Gazelle, I did these from 2 feet up to almost 10 feet. It was not comfortable above 5 feet. Rotor decay didn\'t seem to end and the reduction in collective effectiveness was dramatic.
Technique then is to learn from type experts about what works for what you\'re flying. In general, you\'d have to recover Nr with the lowest collective comfortable, then raise to stabilize, and check at the \"right\" height. Very much a learned technique not a written one.
I didn't mean to imply VRS in an autorotation. The idea here is to transition from autorotation to a powered hover (using engine power, obviously). Once the engine is providing power, the ROD will still be near to what the ROD during autorotation was, hence my reference to the autorotation ROD.
As far as what Thomas Coupling meant, he's the best judge, but he did say, "An engine running auto to a full stop in the hover...[VRS] wouldnt have time to precipitate." Doesn't sound like an auto to touchdown to me.
Mr Selfish,
You\'re right that its a compromise between minimizing ROD and maintaining Nr. If you\'re authorized to do zero speed autos you can determine what ROD and Nr will stabilize and how quickly it will happen. However, the Nr will decay quite quickly if you\'re hovering OGE and to reach a stabilized condition you first need an even lower collective to recover Nr, then increase to maintain.
I did these in a 206 starting at 10 feet - not difficult, increasing to 30 feet - things happening quickly, but minimal loss of Nr...more difficult, then to 50 feet - again things happening quickly, more loss of Nr...most difficult (of what I tried), and finally from about 75 feet...entry the same, time to stabilize, time to peek inside and see what\'s happening...less difficult than 50 and maybe 30 feet. Any higher and I\'d extrapolate that the stabilized condition just lasts longer or you\'d opt to achieve forward flight.
In a Gazelle, I did these from 2 feet up to almost 10 feet. It was not comfortable above 5 feet. Rotor decay didn\'t seem to end and the reduction in collective effectiveness was dramatic.
Technique then is to learn from type experts about what works for what you\'re flying. In general, you\'d have to recover Nr with the lowest collective comfortable, then raise to stabilize, and check at the \"right\" height. Very much a learned technique not a written one.
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Mr Selfish
I do remember taking the collective all the way down, but I must say I am no expert at this, I just feel comfortable having seen what the helicopter can do if the need ever arises.
170'
I vaguely remember that the 206 with floats flew pretty close to a normal 206, can recall feeling any difference.
I do remember taking the collective all the way down, but I must say I am no expert at this, I just feel comfortable having seen what the helicopter can do if the need ever arises.
170'
I vaguely remember that the 206 with floats flew pretty close to a normal 206, can recall feeling any difference.
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Thomas
Yanks!
What? are we back in '43 and stealing your womenfolk agin?
'Yanks' are not an homogenous mass, staring eastward, looking for collective ways to confuse your sense of what's proper and correct, and further distort the Queens English.
We have types like Lappos,yourself and several others who have put in the time and developed, what for me, seems like an uncanny level of knowledge...
Then we have your common or garden!yank/polack/frog/canuck/et al, such as myself, who just fly helicopters.No great aviation education other than what we learned in flight school, just been out flying for a living all my life.
No claim on being any kind of Guru, but nonetheless like to throw in our 'two bits' ...Just for the fun (as the French say!)
The Spanish milled dollars were easily cut apart into equal "bits" of 8 pieces. One "bit" would be equal to 1/8 of a dollar, and 2 bits would equal 2/8 (a quarter of a dollar). So, that's why the coins were called "pieces of eight", and "2 bits" was commonly used to refer to 25 cents.
When contributing my little piece to this august forum, I write as if I'm speaking to a guy in the hangar...I don't really think about the pedantics.As most guys (I think) just intrinsically understand the jargon. If the check airman says to me, "give me a 180 to the ground"...I don't ask, a 180 What?......I just kinda know what he means! and go ahead and do it best I can...
I appreciate that some people want to get to the marrow, but then again, some of us just throw out a few comments without needing to write something for peer review.
Your clarification of the nomenclature makes sense to me, although I don't know that you'll find too many people adhering to it, with this degree of accuracy.
I'm not arguing the need for accuracy, just that many of us 'cousins' are a little more relaxed about nomenclature, or maybe just a little more relaxed period...
Most 'Yanks' think of an auto, simply as an auto! with the codicil attached... to a power recovery or a full down...touchdown...take it to the ground etc...
VRS v SWP....In my working world (logging) the approaches might start out as upflow/upwind, and just as everyone gets in the groove, we get a windshift and you end up falling thru a little....Am I in VRS or SWP....I don't know? because as soon as I feel it happening, I fly out of it before I get bent too far outta shape..... I work with it, until the next cycle break, and try to get the guys/landing reset. It's just not that big a problem... But when I read that in VRS I'm just along for the ride, makes me wonder if I'm safe doing what I've done for a long time. maybe I just don't get it? but I get paid for heading downhill (normally) as fast as I can and somehow I always seem to stop at the bottom...Go figure?
I've heavily edited this from the original to remove the apparent vitriol, I got a couple of emails saying I'd gone overboard...
You see! ....I find the way you say 'Yanks' offends me...Don't know why exactly,some folks can say it fine. The way you say it just irritates the hell outta me!
I feel better now!
170
Yanks!
What? are we back in '43 and stealing your womenfolk agin?
'Yanks' are not an homogenous mass, staring eastward, looking for collective ways to confuse your sense of what's proper and correct, and further distort the Queens English.
We have types like Lappos,yourself and several others who have put in the time and developed, what for me, seems like an uncanny level of knowledge...
Then we have your common or garden!yank/polack/frog/canuck/et al, such as myself, who just fly helicopters.No great aviation education other than what we learned in flight school, just been out flying for a living all my life.
No claim on being any kind of Guru, but nonetheless like to throw in our 'two bits' ...Just for the fun (as the French say!)
The Spanish milled dollars were easily cut apart into equal "bits" of 8 pieces. One "bit" would be equal to 1/8 of a dollar, and 2 bits would equal 2/8 (a quarter of a dollar). So, that's why the coins were called "pieces of eight", and "2 bits" was commonly used to refer to 25 cents.
When contributing my little piece to this august forum, I write as if I'm speaking to a guy in the hangar...I don't really think about the pedantics.As most guys (I think) just intrinsically understand the jargon. If the check airman says to me, "give me a 180 to the ground"...I don't ask, a 180 What?......I just kinda know what he means! and go ahead and do it best I can...
I appreciate that some people want to get to the marrow, but then again, some of us just throw out a few comments without needing to write something for peer review.
Your clarification of the nomenclature makes sense to me, although I don't know that you'll find too many people adhering to it, with this degree of accuracy.
I'm not arguing the need for accuracy, just that many of us 'cousins' are a little more relaxed about nomenclature, or maybe just a little more relaxed period...
Most 'Yanks' think of an auto, simply as an auto! with the codicil attached... to a power recovery or a full down...touchdown...take it to the ground etc...
VRS v SWP....In my working world (logging) the approaches might start out as upflow/upwind, and just as everyone gets in the groove, we get a windshift and you end up falling thru a little....Am I in VRS or SWP....I don't know? because as soon as I feel it happening, I fly out of it before I get bent too far outta shape..... I work with it, until the next cycle break, and try to get the guys/landing reset. It's just not that big a problem... But when I read that in VRS I'm just along for the ride, makes me wonder if I'm safe doing what I've done for a long time. maybe I just don't get it? but I get paid for heading downhill (normally) as fast as I can and somehow I always seem to stop at the bottom...Go figure?
I've heavily edited this from the original to remove the apparent vitriol, I got a couple of emails saying I'd gone overboard...
You see! ....I find the way you say 'Yanks' offends me...Don't know why exactly,some folks can say it fine. The way you say it just irritates the hell outta me!
I feel better now!
170
Last edited by 170'; 24th Dec 2005 at 03:30.
170 - that's what us limeys love so much about you yanks - your easy going nature, ability to take criticism and sense of humour.
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He who walks sideways...
Think you need to re-read my post with a less jaundiced eye. No problem with you supporting your countryman, you and he can't help being British, any more than I can help being American. I guess it's clear neither of us would want to swap places...
Unfortunately, I resemble your remarks regarding SOH, criticism etc!
I used to possess some of the your stated qualities until hitting the UK shore...After many months of exposure to the few, I'm just not the man I used to be...Try dealing with the CAA as a foreigner...
Before I'm accused of widening the existing chasm between Yank and Brit, let me state clearly that my feeling about the British are by no means a blanket disapproval.
I've met a bazillion great people, along with the pompous, self serving few. The majority of us, Yank and Brit alike, laugh at pomposity wherever we find it, and from whatever nationality the source...Just sometimes the tone of voice or style of written word, makes the laughter stick in the craw!
....170
edited for grammar!
Think you need to re-read my post with a less jaundiced eye. No problem with you supporting your countryman, you and he can't help being British, any more than I can help being American. I guess it's clear neither of us would want to swap places...
Unfortunately, I resemble your remarks regarding SOH, criticism etc!
I used to possess some of the your stated qualities until hitting the UK shore...After many months of exposure to the few, I'm just not the man I used to be...Try dealing with the CAA as a foreigner...
Before I'm accused of widening the existing chasm between Yank and Brit, let me state clearly that my feeling about the British are by no means a blanket disapproval.
I've met a bazillion great people, along with the pompous, self serving few. The majority of us, Yank and Brit alike, laugh at pomposity wherever we find it, and from whatever nationality the source...Just sometimes the tone of voice or style of written word, makes the laughter stick in the craw!
....170
edited for grammar!
Last edited by 170'; 24th Dec 2005 at 09:47.
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I didn't realize this went so deep. I just thought the use of 'yank' was in reference to the collective action at the touchdown/full auto/EOL with a parallel to a frequently misused term for someone from the US. 
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Mathew
Probably not as deep as it looks, I just read one too many comments that I thought to be condescending and pompous.
I'm no better than anyone else, and often refer to someone using common argot. Gotta say though, that Limey and Yank are from Dad's generation not mine, and I'm early fifties!
Not such a big deal I suppose!... but when you hear constant criticism of the US system. It gets old real soon!
Especially when they spend 10 minutes telling you whats wrong with US licensing, and the reckless nature of US Operations. Followed be tales of what great vacations they have in FL and how they'd move across tomorrow if possible! This was a recent episode from a local, not referenced to TC
Anyway, back to fixing the brand new dining table and chairs that arrived this morning, just in time for dinner for 14 tonite.
Unfortunately I missed the small sign saying " Some assembly required" been at it 2 hours and so far got 4 of the chairs together...170
Probably not as deep as it looks, I just read one too many comments that I thought to be condescending and pompous.
I'm no better than anyone else, and often refer to someone using common argot. Gotta say though, that Limey and Yank are from Dad's generation not mine, and I'm early fifties!
Not such a big deal I suppose!... but when you hear constant criticism of the US system. It gets old real soon!
Especially when they spend 10 minutes telling you whats wrong with US licensing, and the reckless nature of US Operations. Followed be tales of what great vacations they have in FL and how they'd move across tomorrow if possible! This was a recent episode from a local, not referenced to TC
Anyway, back to fixing the brand new dining table and chairs that arrived this morning, just in time for dinner for 14 tonite.
Unfortunately I missed the small sign saying " Some assembly required" been at it 2 hours and so far got 4 of the chairs together...170
170' chill out big guy....do u c any other yanky doodle dandies getting their knickers in a twist old boy?
Wouldn't like to be cooped up in the space shuttle with you for more than a couple of hours.
Brits / yanks/ japs/ frogs......who cares.
Wouldn't like to be cooped up in the space shuttle with you for more than a couple of hours.
Brits / yanks/ japs/ frogs......who cares.
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Zero Speed..
I have shown pilots vertical decent auto's in bell 47's. No problem, as people have said must have good judgement at the bottom. A slight wind always helps....
I always found it nice to know I could land it where I wanted it...
Darren
I always found it nice to know I could land it where I wanted it...
Darren
