Vortex Ring State Vs. Settling With Power

[thrilsekr]

Ok, so this has been argued before. But, I have not been able to find an answer that actually clears anything up for me. Are they the same creature?

I have found several sources that say they are the same. Look up VRS and they will tell you it is the same as SWP (ie ch 2 "vortex ring state" of "Fatal Traps for Helicopter Pilots". But look up SWP, and they also tell you it is the same thing as VRS, although you will find some that it says is not.

 

Like whistlerpilot says from the "Landing Technique" thread:

 

"In Canada commercial training distinguishes between vortex ring state and settling with power. Aerodynamically they are different. This is a subtle but crucial distinction for these high power slow rate of closure approaches. Don't want either surprise close to the ground!"

 

...Sorry for calling you out, bro. Here is proof (I got your back).

 

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”. 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."

Which seems to me to be more like pilot error rather than an aerodynamic issue. And this manual gives no more of a definition than that.

 

 

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,

[AngelFire_91]

Sounds to me like they are trying to differentiate between not having enough power to arrest the descent, and the actual aerodynamics of settling into your own downwash. One is an engine/power limitation, and the other is an actual aerodynamic effect. I've always been taught that they are the same, however it makes sense given certent situations that they be differentiated between.

[West Coaster]

Settling with Power can be brought on by many factors of your environment and phase of flight.

 

-If you turn downwind, IGE can instantly become OGE, and if heavy you could very well settle with power.

-Misjudge your performance (high/hot/heavy) and you can very easily settle with power if you can't hover IGE at your destination.

-Once you get into a situation where you're settling with power, there is almost zero chance of escape. You simply won't have enough power left to fly out of it, nor time to get enough airspeed to do you any good.

 

Settling with Power is often labeled as a aerodynamic phenomenon, but this is a myth. It is always a result of a limitation imposed on the helicopter either by the environment, the pilot, by mechanical failure or any combination on the three. It it impossible to get into settling with power hovering at the top of a 150' longline with a heavy load under you. You can however create a Vortex Ring State in this situation...

 

Vortex Ring State is an aerodynamic phenomenon. It can be induced in a OGE hover or during the landing phase of a flight, which is where it gets mistakingly called Settling with Power. Unlike SwP, a Vortex Ring State can be easily flown out of if recognised early. VRS can also afflict the tail rotor, but don't call it LTE.... again this is not the same. LTE happens when the torque of the drivetrain becomes too much for the tail rotor to effevctivly counteract. High winds acting against the tail rotor can also cause LTE. The torque takes over and the heli becomes a spinning top. The result is the same with VRS in the tail rotor, but the cause is different. With VRS in the tail rotor, the thrust vector from the tail rotor is nulled as it starts to recirculate it's own wash. Torque has nothing to do with it (though it doesn't help either!). Well I guess you could call it LTE really, as the tail rotor is no longer effective, but really it's not LTE in the true sense of the words. Whatever lol.

 

My 2 bits on the matter anyways. Clear as mud?

[IGM]

welcome to the topic ...

it all depends - if you in preparation for oral - repeat what the book said and fly safe before check ride, during and well beyond ..

let's look from the inside ....

now - VORTEX is NOT SETTLING WITH POWER .

SETTLING WITH POWER - can happen if the Power Required exceeds Power Available or Used by You or me For THAT Exact Conditions, well for That AIRSPEED.

The Helicopter may Settle or descend with Power on, and if You apply more power You just descend faster and uglier down below... But You are not in Vortex state at all ..or not yet - as You try to recover regardless of altitude - Dive gently , gain Airspeed slowly , don't worry about altitude - go in ground effect - ifAll in green - it's as solid airfoil - You fly out ...

Vortex state - if You allow Yourself to be there on any recover except intial one - You will roll helicopter as well as pitch up - so the roll 'll be nasty ....

 

In any way - it is semantics..............

However - Vortex ring state is most likely to be encoutered whenever helicopteris placed by US, Pilots downwind at low speed out ofground effect - turn base to final - wind, slow try to catch up - you are in Vortex, try to catch more with collective with LZ - You are settling with power - then pronounced Vortex ring - ground either way..

or aggressive flare in calm winds or with tail wind....

 

In any way , clarify for Yourself... and not check ride ...

 

More - how about US/ FAA " quick Stop " - as straight forward into wind exercise - not a thing to do with stop or quick... if You want quick stop - turn sideway and stop..

and CAA? Canada - " quick Stop" - by flying downwind, Banking 30 degrees , and same as FAA/US ...after that...

either way it's greta coordination exrecise - take all and the longest RWY - use it all on one exercise - enjoy it !!

 

I do hope there is no more confusion as when we started ...

 

I do agree with all !!!

 

Stay safe for ever !

 

Cordially,

IGM.

[Jeff]

Who cares? I suggest that anyone who wants to take the time to troubleshoot the situation in the air should install smoke generators so you can see if there really is a vortex ring state or not. Regardless whether it is VRS or SWP, I am going to apply the corrective control inputs first and then worry, uh... I guess I won't really care what is was--exactly. I'll be glad I promptly applied the proper recovery technique.

 

~Jeff

[West Coaster]

I can see your point Jeff, but it's worth talking about. Many don't know the difference or what situations they can put themselves into to create either one. You are right though, doesn't matter at the time so long as you correct it asap.

 

As for the question subtle differences, ask your instructor to demo a VRS at altitude. It's perfectly safe if you have a few thousand feet between you and the ground, and you'll need it as you fall like a brick. One of the first indications can be pronounced yaw back and forth as the air around the tail swirls about. As you fall into full VRS the pedals become much less effective, but heading control is not lost. You begin to freefall at a very high rate similar to an auto rotation, with the VSI almost pegged at the bottom. The fall happpens so smoothly though that you hardly notice the sink rate till you look at the gauge. The recovery is easy and near immediate. Lower the collective a touch and nose forward and your out of the VRS in a second or two.

 

Settling with power feels similar, but you have more tail rotor authority.... till your pedal hits the stop! Often you'll get uncommanded yaw due to the high torque you've demanded but exceed the capability of the tail rotor to counteract. So now you're sinking and yawing. Joy! Like in VRS the recovery is to lower collective and noce forward for airspeed. If you don't have enough time/room for this, lower collective to straighten the nose for a run on landing. If you've gotten yourself into a settling with power situation, odds are you're landing right now whether you like it or not. Try not to break anything!

[thrilsekr]

Thanks for the info. I think, with your help, I have developed clarity on this matter. At least, clear to me.

 

Basically, I think it boils down to:

 

VRS can happen at any altitude, and is an aerodynamic issue caused by maneuvering (ie slow speed and high rate of descent) and/or natural forces (ie tailwind).

SWP is typically encountered during a landing in which a mechanical issue is caused by maneuvering (ie overshot landing) and/or natural forces (ie tailwind or downdraft).

 

Thanks.

[West Coaster]

You got it amigo.

 

If you do go out and have an instructor demo a VRS it's actually very reassuring. In school you're always warned about it like some begotten boogeyman from a bad story. But in reality it's very hard to create, even if you're trying to.

 

VRS can happen:

-prolonged OGE hover if you're not smooth on the collective

-Landing downwind if your groundspeed falls below the windspeed with a high rate of decent (you're now decending into the 'dirty air' of your thrust vector).

 

SWP can happen:

-poor planning (over gross weight, etc)

-turning downwind OGE to final or departure & near gross weight (main cause)

-landing downwind and not knowing you're downwind to begin with (2nd leading cause)

-partial failure of any number of engine systems on final/departure (governor, FCU, carb heat stuck open, compressor stall, etc)

 

There is a lot of talk among some people of getting rid of the term Settling with Power all together. It's a very vague and general term that encompasses so many situations. As settling with power is almost always a result of pilot error, why not just call it that. I've read so many accident reports blaming settling with power that go like this;

"The pilot of the MD500 departed in VMC conditions at 1245Z. On the initial climb he turned downwind at about 50' AGL and the helicopter began an uncommanded decent. The pilot could not stop the decent and the helicopter impacted trees 150' from the pad. Winds were estimated to be 15-20 kts, the helicopter was near it's gross weight limits for the conditions that day. "

Classic settling with power.... and pilot error.

 

I've had my own brush with bending a machine thanks to SwP, guilty as charged. Again a classic example too. On short final to a mountain pad, max gross weight (couldn't hover OGE) and a lovely 37°C/98°F on the OAT gauge. Fun times! About 50' back from the elevated pad the wind swung around 180° into a tail wind. I was already pulling 100% torque and the wind shift pulled the rung out from under me.

Not enough room to make the pad as I began to sink and fall short, but I luckily had an out. To the left the mountain dropped off fairly steeply and by nosing over just a hair I kept the airspeed needed to clear the trees before the drop. The tree tops lightly brushed the belly, and I nearly soiled myself. I was extremely lucky.

[Whistlerpilot]

thrilsekr, thanks for covering my back.

 

WC you eloquently wrote about the difference between VR and SwP.

 

Another term to further stir up the conversation "over pitching". Related to SwP because the pilot due to flying errors has to pull tons of collective to stop the aforementioned alarming descent. The engine can't maintain the rotor rpm with the sudden high angle of attack and RRPM decays. This can lead to further descent, and uncommanded yaw as tail rotor rpm decays at the approximate 6 to 1 ratio to main RRPM.

 

A vicious cycle.

 

Vortex Ring is pretty easy to stay out of because the conditions that set it up are obvious and known.

 

SwP though can catch even very experienced pilots off gaurd. What do you think of the term "uncommanded descent" to describe those harrowing close calls. Wally described one in the landing techniques thread that he was able to fly out of by quickly recognizing it and flying away before he lost his out.

 

Here is another close call "uncommanded descent" that I experienced as px with a very experienced pilot who made a mistake about 8 years ago with a company I used to fly with as a heliski guide.

 

We were coming in to land at almost 9000' True Alt on a warmer than usual winter day. The machine was near max gross weight. The landing was near the summit plateau of a glacier with flags set up for the usual prevailing SE through SW winds. That day the winds up high were 15 to 20 kts outflow from the N. We flew up the glacier the usual approach direction and the pilot set up for the standard SW landing. I mentioned to him that the winds were from the N and I thought we should go around. He said no problem I've got it or something to that effect, and started a descending pedal turn to land facing the other way. Very rapidly we fell out of the sky 75' and actually hit the ground (compact snow) with one skid on a 25 degree slope. The pilot ****ed up huge, but did an amazing job recovering by pulling collective and cushioning the impact so that we bounced gently back into the air and dove off the precipice that was conviently near by.

 

When the clients asked me what happened I kinda lied and told them we hit unexpected wind shear and the pilot used the mountain to stabilize. I actually thought we were crashing and going to roll 3000' off the mountain as it happened.

 

He was one of the most skilled pilots I've flown with but several questionable PDM situations led to our "requesting" another pilot.

 

Here is some good PDM of a pilot maintaining over 1/2 mile viz coming back down to the valley after our ski day yesterday. Today the same pilot showed good PDM by not even getting us skiing because the same inversion fog wouldn't let us lift off and keep 1/2 mile viz. Argh, knowing it's totally clear above and only a few hundred feet thick. Could even see the occasional silouete of peaks lit up by the sun as we ate lunch in the valley gloom.

 

Edited February 6, 2009 by Whistlerpilot

[roundwing]

Disregard.

 

Found the answer to my question in the Rotorcraft Flying Handbook.

 

The handbook has a section listed as "Vortex Ring State(settling with power).

 

On page 11-5 to get the full explanation.

[r22butters]

...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...

 

I've never heard that description for "settling with power",... poor pre-flight planning, or flying stupidly, yes,...but not "settling with power" (which is just the "slang" term for the Vortex Ring State anyway).

[iChris]

Disregard.

 

Found the answer to my question in the Rotorcraft Flying Handbook.

 

The handbook has a section listed as "Vortex Ring State(settling with power).

 

On page 11-5 to get the full explanation.

 

 

Also covered in detail on the other form during the same time period (link below)

Subject: Settling with Power & Vortex Ring State

 

 

[SBuzzkill]

This is what I learned:

 

https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/23947-1/FM/3-04.203/chap1.htm#_Toc147118313

Edited February 23, 2011 by SBuzzkill

[nightsta1ker]

I was taught that they were one in the same, and had never heard anything to negate that until now. All training in regards to the alternate definition of settling with power was lumped in with density altitude and aircraft performance (run on take-offs amd landings, calculating your oge/ige hover altitudes and being aware of "mushing" on downwind at high gross weights with a tailwind etc).

 

I can definitely see the advantages of training to differentiate the two as it does make sense, but I have to wonder if it could lead to some poor student failing a checkride with an examiner who uses the Rotorcraft Flying Handbook as their knowledge standard. Over the years I have leaned that a lot of stuff in that book is incorrect or incomplete!

[jjsemperfi]

In my opinion there are a couple ways to look at this. Terminology wise, one could get confused with thinking that Settling with Power is being used to describe what Vortex Ring State produces, which is a high descent rate with power applied, but not because of insufficient power. Then one could describe Settling with Power as having insufficient power or rotor rpm to arrest the descent rate, but not because of a fully developed vortex ring state. There are two sides of the coin. I had a huge arrgument with someone about Vertical Autorations. Turns out, after countless threads, he meant power failure at hover. So I think people use incorrect terminology to describe aerodynamics all the time. Because what I was taught, is that when you have a fully developed vortex ring state, then it doesn't matter how much power you apply, you will descend even more rapidly, hence settling with POWER.

[eagle5]

In my opinion there are a couple ways to look at this. Terminology wise, one could get confused...

...So I think people use incorrect terminology to describe aerodynamics all the time.

 

A cfi and a student (also a rated pilot) are flying a 500. As they come in to land the rpm gets low, the cfi cries out, "add power, add power!". The student raises the collective, they hit hard, and the tail gets chopped off! I guess the cfi should have cried out, "roll the throttle on!"?

 

Yes, correct (or more importantly "consistant") terminology might be better for us all?

[rotormandan]

I've always known m/r vrs and settling with power to be 1 and the same. What you guys are describing i've always known as power settling.

[aeroscout]

The way I understand it is, you have to fully develop the vortex ring state to settle with power, at that point the two are interchangeable terms. Winds or downwinds have nothing directly to do with vrs or swp, although poor wind management can make swp easier to enter.

[nightsta1ker]

Here's the difference, you can settle with power while in VRS. But you don't need to be in VRS to settle with power. You can settle with power because of low rotor RPM, you can settle because you are not able to generate enough lift for conditions, you can settle because your descent rate is too great to check with an application of power (not necessarily VRS if this happens above ETL). Most of these scenarios would happen high, hot and heavy. So there IS a distinction between the two. It should be taught as such.

[eagle5]

Now lets try Loss of Tail Rotor Effectiveness vs. Loss of Tail Rotor Authority.

[pilot#476398]

Well here's my opinion:

 

I believe you need power to get into the Vortex Ring State (i.e. it won't happen in an Auto?), therefore Settling with Power is another term for VRS (plus every time I practice VRS recovery the CFI says, "Now let's do Settling with Power").

 

If you start to "settle" because the throttle is wide open, you are settling because you have no more power available, but are still pulling up on the Collective! If there is no more power available, I would not call that "Settling with Power", or even "Power Settling", because ,again, there is no power left!

 

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!

 

Opinion # 476,398

[aeroscout]

Here's the difference, you can settle with power while in VRS. But you don't need to be in VRS to settle with power. You can settle with power because of low rotor RPM, you can settle because you are not able to generate enough lift for conditions, you can settle because your descent rate is too great to check with an application of power (not necessarily VRS if this happens above ETL). Most of these scenarios would happen high, hot and heavy. So there IS a distinction between the two. It should be taught as such.

 

I think you are confusing settling with insufficient power, with settling with power. Settling with power must include a fully developed vortex ring state, at least the way I understand it.

[nightsta1ker]

Where does it say that it needs to include a fully developed vortex ring? And what's more, what do you consider "fully developed" to be? I have read accounts of pilots who got into VRS so developed it was nearly unrecoverable, even with nearly unlimited altitude (Shawn Coyle describes one such scenario in one of his books) 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 generated.

 

But I digress. I guess my point is that there can be two causes for "Settling with power" 1: insufficient power 2: VRS. VRS needs power applied in order to develop, but you can settle due to insufficient power without being in VRS.

 

In both cases, power is applied, but you are still descending beyond your control. Hence "settling with power".

[rotormandan]

Here's the difference, you can settle with power while in VRS. But you don't need to be in VRS to settle with power. You can settle with power because of low rotor RPM, you can settle because you are not able to generate enough lift for conditions, you can settle because your descent rate is too great to check with an application of power (not necessarily VRS if this happens above ETL). Most of these scenarios would happen high, hot and heavy. So there IS a distinction between the two. It should be taught as such.

 

 

I'm not trying to be rude by calling you out but that is wrong. There is not a distinction between the two. The term "Settling with power" is a term or nickname given to m/r vrs because when in this condition, as you add more power you decend or settle faster. It is a term for that condition.

 

 

 

 

But I digress. I guess my point is that there can be two causes for "Settling with power" 1: insufficient power 2: VRS. VRS needs power applied in order to develop, but you can settle due to insufficient power without being in VRS.

 

In both cases, power is applied, but you are still descending beyond your control. Hence "settling with power".

 

By your definition then anytime in a decent one is settling with power. If on approach one would have power applied but only enough to control the decent or settling rate.

 

Once again "settling with power" is a term applied to m/r vortex ring state where one is settling in their own downwash.

[nightsta1ker]

Good points. But I what I meant was that any time you are settling uncontrollably with power applied.

 

Also, it was brought up that these two are taught in Canada as distinctly different causes for an uncontrollable settling of the helicopter in the OP. I was always taught about them interchangeably as well. But after reading this I believe it should not be taught that way as it can cause confusion.

 

I'm not saying you shouldn't use the term Settling With Power along with Vortex Ring State, but I think it should be taught that there is more than one reason for a helicopter to settle uncontrollably while power is applied. 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.