Vortex Ring State Vs. Settling With Power

[eagle5]

...You DON'T need to be in VRS in order to experience a loss of lift that leads to an unintentional rendevous with the ground.

 

But you DO have to run out of power available, which is why I don't understand why anyone would call that "settling with power"?

[nightsta1ker]

Clearly this is one of those arguments that is going to play on a loop.

 

In my opinion: if the needles are married, then power is applied to the helicopter. Therefore if the helicopter settles beyond the pilots control, it's settling with power. As discussed though, there is more than one cause for a settling condition while power is applied to the helicopter.

 

One other point, you tried to debunk my theory by saying that insufficient power means the helicopter is not settling with power because that power was insufficient, therefore it cannot be called settling WITH power. Well what amount of power do you need to have to develop a vortex ring condition? 20% was what I was taught. 20% of available power would not be enough to terminate an approach even if you werent in a VRS. So what should we call this then? Settling WITHOUT power?

Edited May 6, 2012 by nightsta1ker

[eagle5]

Clearly this is one of those arguments that is going to play on a loop.

 

In my opinion: if the needles are married, then power is applied to the helicopter. Therefore if the helicopter settles beyond the pilots control, it's settling with power. As discussed though, there is more than one cause for a settling condition while power is applied to the helicopter.

 

One other point, you tried to debunk my theory by saying that insufficient power means the helicopter is not settling with power because that power was insufficient, therefore it cannot be called settling WITH power. Well what amount of power do you need to have to develop a vortex ring condition? 20% was what I was taught. 20% of available power would not be enough to terminate an approach even if you werent in a VRS. So what should we call this then? Settling WITHOUT power?

 

This is how I see it.

 

#1 You have a high decent rate. Your airspeed slips below ETL. You pull up on the Collective, but continue to decend. You pull up more on the Collective, but still continue to sink. This is VRS. The throttle is not wide open. You have plenty of power available, thus the term, "settling with power"!

 

#2 You pull up on the Collective, but the throttle is wide open. The rpm starts to droop, and you start to decend. You pull up more on the Collective, but continue to decend. Yes you are settling, but its because the engine has run out of power, thus it makes no sense to call this one, "settling with power".

 

#3 You are flying a helicopter without a Governor or a Correlator. You pull up on the Collective, but do not roll on the throttle. The rpm starts to droop, and you start to decend. You again pull up more on the Collective, but of course continue to decend. The throttle is not wide open. The engine has plenty of power, yet you are still decending! Can you call this "settling with power"?,...sure, but I suspect most of us would call it, "A Robbie Guy flying an Enstrom"!

 

As for what amount of power you need to develope VRS:

 

#4 You are in an OGE hover at 5000'. You start to sink. You pull up on the Collective, but the throttle is wide open, therefore you continue to sink. Paniking you continue to pull up on the Collective, and as you sink faster, a VRS developes. Was this SWP? No, VRS developed, but the initial settling was caused by your engine not having any more power to stop its sink rate, thus VRS was developed with no available power! So, in this scenario the terms VRS and SWP are not interchangeable!

 

I'm not trying to debunk you, I just don't understand your point of view.

Edited May 6, 2012 by eagle5

[C of G]

This is how I see it.

 

You have plenty of power available, thus the term, "settling with power"!

 

 

Yes you are settling, but its because the engine has run out of power, thus it makes no sense to call this one, "settling with power".

 

 

 

This is the funny thing about perspective and in this instance the unspoken word.

 

In both instances you are settling, but in one you have power applied. The other you have power available.

 

So, settling with power applied or settling with power available.

 

Tomato tomato.

[eagle5]

This is the funny thing about perspective and in this instance the unspoken word.

 

In both instances you are settling, but in one you have power applied. The other you have power available.

 

So, settling with power applied or settling with power available.

 

Tomato tomato.

 

I had a cfi scold me once for not pulling in some carb heat (the CAT was in the yellow) while in a hover. I also had a cfi yell at me once for taking my hand off of the collective (to pull in carb heat) while in a hover!

 

I guess your perspective just depends on who taught you!,...toe-may-toe

[rotormandan]

The problem with this argument that everyone is thinking of the action of settling by itself. There are many things that cause a helicopter to settle or decend wether with power applied or not.

 

"Settling with power" is a phrase, a term, a nickname applied to main rotor vortex ring state. My only experience is in the U.S. but it sounds like it's an american term

 

 

 

This is how I see it.

 

#1 You have a high decent rate. Your airspeed slips below ETL. You pull up on the Collective, but continue to decend. You pull up more on the Collective, but still continue to sink. This is VRS. The throttle is not wide open. You have plenty of power available, thus the term, "settling with power"!

 

This may or may not have been vrs. You may have settled into your own downwash or may have simply not enough power to arrest your decent.

 

#2 You pull up on the Collective, but the throttle is wide open. The rpm starts to droop, and you start to decend. You pull up more on the Collective, but continue to decend. Yes you are settling, but its because the engine has run out of power, thus it makes no sense to call this one, "settling with power".

 

#3 You are flying a helicopter without a Governor or a Correlator. You pull up on the Collective, but do not roll on the throttle. The rpm starts to droop, and you start to decend. You again pull up more on the Collective, but of course continue to decend. The throttle is not wide open. The engine has plenty of power, yet you are still decending! Can you call this "settling with power"?,...sure, but I suspect most of us would call it, "A Robbie Guy flying an Enstrom"!

 

I would call both of these low rpm. With the 2nd one being pilot induced. Both involve settling and ther is power applied buy you're not sinking in your own downwash.

 

As for what amount of power you need to develope VRS:

 

#4 You are in an OGE hover at 5000'. You start to sink. You pull up on the Collective, but the throttle is wide open, therefore you continue to sink. Paniking you continue to pull up on the Collective, and as you sink faster, a VRS developes. Was this SWP? No, VRS developed, but the initial settling was caused by your engine not having any more power to stop its sink rate, thus VRS was developed with no available power! So, in this scenario the terms VRS and SWP are not interchangeable!

 

If you run out of power because you're at wot then you would be sinking due to low rpm. I don't think you would get vrs because as your m/r slows you won't be creating enough vorticies. Either way though the terms are interchangable because swp is a nickname for vrs.

 

 

 

My conclusion is that "Settling with Power" is just another term for VRS. Whenever I practice that other scenario, we call it Low-RPM Recovery!

 

 

My point exactly

 

 

It doesn't need to be "fully developed" for you to settle. It just needs to be developed enough that it is overcoming any lift being

 

That's the thing with "settling with power," aka m/r vortex ring state. You are not generating lift. The more power applied the less lift you are generating. Its like having oppisite day with your collective. You add power, create more vorticies, which shrink the angle of attack.

That's the nickname comes from. Because, as you all know, you settle even faster the more power is applied.

 

So, yes, there are many reasons to settle wether in control or not with power applied, "settling with power" is only a term applied to m/r vortex ring state. It's the lamens term(at least in america) while m/r vrs would be the scientific or smart persons term.

 

Disclaimer: please excuse the typos. I'm on an iphone and this is a pain in the rear end.

[nightsta1ker]

Well after looking up the definition of "Settling with power" in every source of helicopter information I could get my hands on, I have to concede my argument. They are all directly associated with Vortex Ring State.

[aeroscout]

Well after looking up the definition of "Settling with power" in every source of helicopter information I could get my hands on, I have to concede my argument. They are all directly associated with Vortex Ring State.

It takes a big man to admit they're wrong. I'm pretty big on many occasions myself !

[eagle5]

There's one thing I don't quite get. Why do they say you need to be using between 20 and 100 percent of engine power? Can you not enter VRS using only 10%?

[iChris]

In the Transport Canada TP9982E Helicopter Flight Training Manual which you can find here: http://thrilsekr.com/Flight_Training/TP998...ng%20Manual.pdf

It states...

 

"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".

 

So. I understand the principles VRS. And how to recover from it, why that recovery works. I am looking for someone to tell me how SWP is actually different. What are the subtle differences? What I have found in my searches yields the same definition for both terms.

 

Thanks,

 

The OP may have answered his own question with that quoted reference.

 

 

Settling with power” and “power settling” are more so, layman’s terms that describe symptoms caused by specific aerodynamic phenomenon.

 

It’s a cause and effect relationship in which an action or event will produce a certain response to the action in the form of another event. A similar concept in logic is necessary and sufficient causes.

 

Vortex Ring State (VRS) maybe a sufficient cause of settling with power (SWP). So the logic of sufficient cause would say:

 

VRS maybe a sufficient cause of SWP, then the presence of VRS may imply the presence of SWP. However, another cause “x” may alternatively cause SWP. Thus the presence of SWP does not imply the presence of VRS.

 

Shawn Coyle writes in his book “Cyclic & Collective:

 

“Vortex ring state is often mistakenly called “settling with power.” To be very clear, “settling with power” is a misnomer – it could happen if the power required exceeds the power available (or used) for that airspeed.”

 

Ray Prouty writes in his book “Helicopter Aerodynamics Volume II”:

 

“Pilots use two terms, “settling with power” and power settling – sometime interchangeably and sometime to represent two different situations. One is the vortex ring condition. The other is simply entering into a flight condition where the required power is more than the available power… I propose dropping both terms and substituting “thrust instability” for the vortex-ring phenomenon and “running out of power” for the other.”

 

Quote:

 

“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…”

REF: Transport Canada Helicopter Flight Training Manual

 

Quote:

 

“A horizontal rotor creates a downward flow induced by the thrust generation. If the rotor moves along the direction of its induced flow, i.e. down, the downward induced flow will compete with the upward flow due to the descent motion. As a result, the smooth slipstream around the rotor disk is gradually destroyed.

 

In particular, when the descent rate approaches the rotor induced velocity, the rotor enters its own wake, resulting in blade tip vortices recirculation. These vortices will then tend to pile up at the disk plane to create a so-called doughnut-shaped vortex ring. Moreover, the onset and development of this so-called vortex ring state can be viewed as a spatial and temporal wake instability.

 

By instability one means vortex rings as a result of wake recirculation in the plane of the rotor. Periodically however the character of this recirculation changes, as a partial vortex collapse causes flow asymmetry at the rotor disk. This phenomenon results in large fluctuations in rotor lift and torque.

 

For a helicopter main rotor, VRS may occur for example in a descending flight, while for a helicopter tail rotor, VRS may occur during a sidewards flight, or while in hover with a crosswind. For the case of a main rotor VRS condition, the symptoms are generally excessive vibrations, large unsteady blade loads, thrust/torque fluctuations, excessive loss of altitude, and loss of control effectiveness. Hence flight in the VRS is a dangerous flight condition, especially if entered at low altitude. For the case of a tail rotor VRS, it is the vehicle yaw control (i.e. heading) that may become difficult or impaired.”

 

REF: A Qualitative Introduction to the Vortex-Ring-State, Autorotation, and Optimal Autorotation

 

Quote:

 

“Flow in vertical descent. One of the most striking flow studies is that of Reference #6 from which figure #8 was prepared. Figure 8(a) shows the wake of a hovering helicopter, which gathers air, largely from above the rotor, and funnels it downward to produce lift. As soon as the rotor begins to descend its motion produces a flow upward past the rotor opposing the induced flow, until the so-called point of ideal autorotation is reached.

 

For this condition, the mean induced velocity is just cancelled by the helicopter's rate of descent. The flow becomes more violent as the r a t e o f descent increases further (fig. 8(d) and 8(e), and then finally smooths out again at very high rates of descent where the rotor operates in a true windmill brake mode. The highly disorganized flow shown is termed the vortex-ring state. All though large vortices are present, there is no semblance to the regular ring-like vortices, which are usually conjured up by the name "vortex-ring state." This flow is so complicated and unsteady that no complete treatment has ever been attempted; instead, only simple one-dimensional analyses are used. These treatments are usually referred t o as momentum theory.”

 

REF: NASA Technical Memorandum 81920 SOME WAKE-RELATED OPERAT1ONAL LlMITAT1ONS OF ROTORCRAFT

Edited May 10, 2012 by iChris

[iChris]

There's one thing I don't quite get. Why do they say you need to be using between 20 and 100 percent of engine power? Can you not enter VRS using only 10%?

 

The vortex-ring region is not that wide. The lower the power setting the higher the rate of descent and the sooner the transition from the vortex-ring flow state into the autorotation flow state. Remember, you can also escape vortex-ring state by bottoming the collective (if altitude allows) and entering autorotation.

Edited May 10, 2012 by iChris

[nightsta1ker]

Hmm... Some of that stuff sounds strikingly like the point I was trying to make earlier.

 

What I am getting out of this is that they seem to know more about helicopter aerodynamics in Canada.

 

Thanks for your input Chris.

[rotormandan]

What I am getting out of this is that they seem to know more about helicopter aerodynamics in Canada.

 

I think you're right. It was starting to get late here and I was wondering when I'd learn my lesson for the day. Dang Canada.

[nightsta1ker]

 

 

I think you're right. It was starting to get late here and I was wondering when I'd learn my lesson for the day. Dang Canada.

 

Well, they do have a lot more helicopters per capita than the U.S.

[aeroscout]

Well, they do have a lot more helicopters per capita than the U.S.

Are you counting the military helicopters ?

[Chitty777]

probably not

[nightsta1ker]

 

Are you counting the military helicopters ?

 

Hard to say. I did say per capita though, and because Canada's population is smaller than the u.s. that does not necessarily mean they have more helicopters period, it just means that there is a higher ratio of them. There are a lot more of the types of industries that require helicopters in Canada, and a lot of the terrain is not well suited to ground travel. So naturally, helicopters get a lot more use up there than down here. It only makes sense that they have figured out a thing or two that the average Robbie Ranger here in the U.S. doesn't need to think about.

 

What I want to know is... If we are teaching the physics in a generalized way here in the states, rather than being more specific about what is going on, are we missing something or putting ourselves at a higher risk? Probably not. We all know that if we are hot/high/heavy and have a tailwind or are on a steep approach that we are at risk of entering a dangerous condition that could lead to loss of control. So does it really matter if we know the difference between a settling condition versus a vortex ring (because apparently there is a difference)? When it comes right down to it, no. I don't think it does as long as we know to avoid those danger areas and know the recovery techniques. But knowledge is power and the more you know about what's going on up there and why, the better off you will be.

 

 

[Pohi]

Canadian aerodynamics, like their currency, holds little value in the US.

[Airhead]

My take on this bickering is that settling with power is a broader term than vortex ring state. VRS is a specific aerodynamic condition. When this condition occurs you also experience settling with power. The theoretical disparity between the two conditions, in this case, may not be isolated and that would explain why books couple the two together as the same thing.

 

However, if conditions are those which cause the aircraft to have less vertical thrust than required to maintain flight then it will descend. The power being created by the engine may or may not be the maximum amount it can produce but it is producing enough to allow stable flight in different conditions. The factors we know, and have been mentioned, so as long as the proposed conditions are not those which generate a VRS and the aircraft still is descending "un-commanded" then it would be settling with power. It could also result in generating a VRS...hence the circular logic that mirrors this thread.

 

Think about the words settling with power. It sounds to me as, basically, any descent other than an auto, but, I think the key is that the pilot doesn't want it to happen. So it seems like there is a real difference between the terms, but it is mainly semantic or academic, and plenty of people don't give two poops about the difference and get along just fine.

[iChris]

My take on this bickering is that settling with power is a broader term than vortex ring state. VRS is a specific aerodynamic condition.

 

 

For a follow-up post on this Vortex Ring State Vs. Settling With Power see the following post:

What the heck happened here?

[eagle5]

Atheists are good people too! Just because a pers...awh sh*t!,...wrong dead horse, AGAIN!...GODDAMMITT!!!

[aeroscout]

Atheists are good people too! Just because a pers...awh sh*t!,...wrong dead horse, AGAIN!...GODDAMMITT!!!

I can plainly see you have been fudging your cherries !

[ridethisbike]

I can plainly see you have been fudging your cherries !

 

Cherry syrup on my logbook?

 

All these horses look the same...

[aeroscout]

 

Cherry syrup on my logbook?

 

All these horses look the same...

Hmmm, maybe there is a way to combine all 3 phenomena with an opportunistic result ?

[eagle5]

Hmmm, maybe there is a way to combine all 3 phenomena with an opportunistic result ?

 

You come to the realization that VRS and SWP are the same thing, which causes you to lose your faith and renounce your god. Subsequently all your networking friends shun you, forcing you to fudge your logbook, because no one will hire a low time atheist!