What the heck happened here?

[RkyMtnHI]

I am glad to see this come up for review, my hopes are that everyone can learn as much as we did from the incident (and we continue to learn from it).

 

When i saw the video posted i wished that i had posted it and sincerely apologize for not doing so sooner, we were all very lucky that no one was hurt. Mike and i discussed posting here and decided to wait to see what others had to say, there are many correct comments in the posts above and i hope everyone reads them over and over and can put themselves into this position in their mind and hopefully keep it from happening to them. Hoping more good could come out of it.

 

I also hope others will continue to put in their constructive points.

 

I already have two pages composed but have almost another page of notes that i want to add, i’ll try to get to it tomorrow.

 

sincerely,

 

dp

[eagle5]

SWP and VRS are not the same thing.

 

Yes they are.

[helonorth]

Yes they are.

No, they are not. You can be descending vertically with power, but not be in VRS. It's really quite simple.

[eagle5]

No, they are not. You can be descending vertically with power, but not be in VRS. It's really quite simple.

 

If you're descending vertically, because of insufficient power (i.e the rpm starts to droop, and/or the low rpm horn/light come on) its not Settling With Power!

 

...but to each his own!

Edited January 19, 2013 by eagle5

[Gomer Pylot]

When you're using all available power, and it's not enough to arrest your descent, you're settling with power. It need not be vertical (and it needn't be for VRS, either), and the rate of descent can be high or very low. It requires certain conditions for VRS, but for settling with power, it just requires that you don't have enough power available to stop your descent. You can get it at sea level while well below max gross, if your approach is fast enough.

[eagle5]

When you're using all available power, and it's not enough to arrest your descent, you're settling with power. It need not be vertical (and it needn't be for VRS, either), and the rate of descent can be high or very low. It requires certain conditions for VRS, but for settling with power, it just requires that you don't have enough power available to stop your descent. You can get it at sea level while well below max gross, if your approach is fast enough.

 

In your scenario of settling, but not in VRS, what is the recovery technique?

[Nearly Retired]

It's kind of disturbing to me to think that there are helicopter pilots out there who think that there must be vortex ring recirculation to get into a settling with power situation.

 

In the bad old days of heavy, underpowered piston-engine helicopters...you know, back when I learned to fly, you could easily get yourself into a below-ETL descent in which you did not have enough power to stop. You were settling with power all right, right to the ground! Fall right through the ground cushion and end up with smiling skids. No recirculation necessary. Because of this we learned to watch our power, stay above ETL as much as possible and of course make our landings and takeoffs into the wind - things which seem to have gone by the wayside, if I'm reading these threads correctly on forums like this.

 

Yes, I'm in the "SWP is not always VRS" camp. On the other hand, VRS most definitely *is* SWP.

[iChris]

Some of these statements can make you cringe. After all the passed posts on this subject the confusion persist.

 

Lets hear from two highly respected individuals in our industry on this issue, and then we can move on from there:

 

“Vertex 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 state. Vortex ring state is a more clear, precise definition.”

 

“The term settling with power is very misleading and won’t be used. I’d ask you to remove it from your vocabulary.”

 

Shawn Coyle, Cyclic and Collective – Art and Science of Flying Helicopters.

 

“Pilots use two terms, “settling with power and “power settling” – sometimes interchangeably and sometimes to represent two different situations. One is the vortex ring condition discussed above. The other is simply entering into a flight condition where the required power is more than the available power – for instance, finding it impossible to hover at the top of a mountain that was no trouble getting to with forward speed.”

 

“I propose dropping both terms and substituting “thrust instability” for the vortex-ring phenomenon and “running out of power” for the other.”

 

Ray Prouty, Helicopter Aerodynamics, Settling With Power – An Explanation

 

Remember, most of what you’ve learned in these flight schools is an approximation of the truth for easy explanation. Further study is required to learn the rest of the story.

Edited January 19, 2013 by iChris

[Whistlerpilot]

Vortex Ring State and "Settling with insufficient power" are two different problems. Below is a description at the end of the section on VRS in the Transport Canada Helicopter Flight Training Manual.

 

I made the low RPM settling mistake and tried to fly out of it. This resulted in getting into a whiteout and losing all reference over a glacier. It was a similar outcome. Lesson learned the hard way, fortunately just bent metal.

 

Here is what Transport Canada has instructors teach students:

 

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.

[Velocity173]

“The term settling with power is very misleading and won’t be used. I’d ask you to remove it from your vocabulary.”

 

Apparently the Army didn't get that memo because they still use the terms interchangeably in the Fundamentals of Flight. I agree though, they both have have two different meanings.

[Gomer Pylot]

 

 

In your scenario of settling, but not in VRS, what is the recovery technique?

AFAIK, there is none, unless you have lots of altitude. When you run out of power, you're in a corner it's hard to get out of. It's usually only evident when you're too low to recover. The way it's taught by flight schools, coming to a hover at a couple of thousand feet, descending and getting a shudder, isn't even close to reality. It just checks a box on a form, nothing else. The thing to do is not get into it in the first place, by proper planning and approach techniques.

[eagle5]

AFAIK, there is none, unless you have lots of altitude. When you run out of power, you're in a corner it's hard to get out of. It's usually only evident when you're too low to recover. The way it's taught by flight schools, coming to a hover at a couple of thousand feet, descending and getting a shudder, isn't even close to reality. It just checks a box on a form, nothing else. The thing to do is not get into it in the first place, by proper planning and approach techniques.

 

I've been under the impression that, that "shuddering" was entering VRS? Anyway, the PTS task is called SWP, and whenever I have been asked to demonstrate it (by a CFI or DPE) the idea has been to get into VRS and then get out of it. Even the Rotorcraft Flying Handbook calls it "Settling With Power (Vortex Ring State)", so you can probably see why I would consider them one in the same.

 

However;

 

I'm flying along, its hot and heavy, so I'm at full throttle. The rpm is in the green and the VSI reads 0,...everything's cool so far. Then suddenly I find myself descending! Throttle's at full so I can't pull up on the collective, but rpm's in the green, so its not low-rpm recovery! My descent rate isn't high enough for VRS, yet down I go!

 

Call it SWP? I guess you can, but the only place I have ever heard the term SWP to mean anything other than VRS, is here, on this forum!

 

Anyway, po-tay-toe / po-taw-to, I'll just call it "Oh' sh*t!".

[iChris]

“The term settling with power is very misleading and won’t be used. I’d ask you to remove it from your vocabulary.”

 

Apparently the Army didn't get that memo because they still use the terms interchangeably in the Fundamentals of Flight. I agree though, they both have have two different meanings.

 

The Army took that same path of least resistance (approximation of the truth for ease of explanation) in newer editions starting with Fundamentals of Flight May 2007 (FM 3-04.203). They spent about two pages on the subject. The newer books concentrate more on flight operations and performance of normal mission tasks in the field and less on aerodynamics.

 

In contrast, an earlier edition, Fundamentals of Flight October 1988 (FM- 1-203) while still using the term “settling with power,” spent over six pages on the subject of vortex ring state and the other flow states. Very few books discuss the aerodynamics of vertical climbs, descents, and rotor flow states.

 

“Settling with power is a conduction of powered flight in which the helicopter settles in its own downwash. The condition may also be referred to as the vortex ring state, which is one of the four flow states regions. Before this condition is further explained, a discussion of the flow states regions is necessary.” Fundamentals of Flight October 1988 (FM- 1-203)

 

Remember, most of what you’ve learned in these flight schools is an approximation of the truth for easy explanation. Further study is required to learn the rest of the story.

Edited January 19, 2013 by iChris

[eagle5]

It's kind of disturbing to me to think that there are helicopter pilots out there who think that there must be vortex ring recirculation to get into a settling with power situation.

 

In the bad old days of heavy, underpowered piston-engine helicopters...you know, back when I learned to fly, you could easily get yourself into a below-ETL descent in which you did not have enough power to stop. You were settling with power all right, right to the ground! Fall right through the ground cushion and end up with smiling skids. No recirculation necessary. Because of this we learned to watch our power, stay above ETL as much as possible and of course make our landings and takeoffs into the wind - things which seem to have gone by the wayside, if I'm reading these threads correctly on forums like this.

 

Yes, I'm in the "SWP is not always VRS" camp. On the other hand, VRS most definitely *is* SWP.

 

Its not the techniques that have "gone by the wayside", just what we call them!

[pilot#476398]

In contrast, an earlier edition, Fundamentals of Flight October 1988 (FM- 1-203) while still using the term “settling with power,” spent over six pages on the subject of vortex ring state and the other flow states. Very few books discuss the aerodynamics of vertical climbs, descents, and rotor flow states.

 

I remember back when I took College Algebra, when we got to logrithms, he said, there is the old "long way" of doing them, but we're going to use our calculators, which have a "log" button on them!

 

Times change! There may come a day when they no longer teach dead reconing, or VORs,...two things I haven't used since flight school!

[iChris]

Be careful when flying photographers. They tend to scream out last minute directions ( slow down, more,... now hover) to get their shot. May just have caught the pilot off guard for a only a second. Game over.

 

Curious what you all would have done in here. It looked like the rotor slowed in the video just as he hovered, .. probably got the horn then and pitched it forward a bit. But it was too late and too much decay so he nursed it around to the slope. Looked pretty low to begin with to dive forward with success. Thoughts?

 

You're right, game over.

 

What to do should have been figured out before the flight began. The NTSB reports the pilot calculated the in-ground-effect hover to be 8,500 feet pressure altitude, the out-of-ground-effect hover to be 5,000 feet pressure altitude, and estimated the gross weight to be 2,320 pounds.

 

However, Golden Colorado has an elevation of 5,675 feet and the Lookout Mountain road he was flying travels up Lookout Mountain from Golden Colorado to over 7,000 feet. The pilot began the flight with unrealistic performance expectations.

 

Whenever you’re low and slow and near the OGE gross weight of the aircraft, you must remain alert to flight on the backside of the power curve (the aircraft is unstable with respect to airspeed vs. power under this flight condition).

 

In this case, the pilot is on the backside of the power curve and makes a left pedal turn downwind, OGE, and simply enters into a flight condition where the required power is more than the available power. The pilot's first reaction is to pulling collective; however, the engine power available can’t support the required increased blade pitch and drag so the RPMs start decreasing. The pilot then lowers collective, but there’s not enough time or altitude to recover, game over.

 

Edited January 20, 2013 by iChris

[iChris]

I remember back when I took College Algebra, when we got to logrithms, he said, there is the old "long way" of doing them, but we're going to use our calculators, which have a "log" button on them!

 

Times change! There may come a day when they no longer teach dead reconing, or VORs,...two things I haven't used since flight school!

 

That's why I say:

 

Remember, most of what youve learned in these flight schools is an approximation of the truth for ease of explanation. Further study is required to learn the rest of the story.

 

Were talking about the Physics of how things work. Physics is one of the oldest academic disciplines. It involves the study of matter and its motion through space and time, along with related concepts such as energy and force. It extents into the physics of aerodynamics:

 

What is Aerodynamics? The word comes from two Greek words: aerios, concerning the air, and dynamis, which means force. Aerodynamics is the study of forces and the resulting motion of objects through the air.

 

Youre correct, times change; very little knowledge in aerodynamics is needed on your part to fly the helicopter. So, youre free to remain unfamiliar with, inexperience in, lacking knowledge of, and information about the profession in which youre engaged and the aircraft you fly.

Edited January 25, 2018 by iChris

[Nearly Retired]

Eagle5:

I'm flying along, its hot and heavy, so I'm at full throttle. The rpm is in the green and the VSI reads 0,...everything's cool so far. Then suddenly I find myself descending! Throttle's at full so I can't pull up on the collective, but rpm's in the green, so its not low-rpm recovery! My descent rate isn't high enough for VRS, yet down I go!

 

Call it SWP? I guess you can, but the only place I have ever heard the term SWP to mean anything other than VRS, is here, on this forum!

 

Not true. Nick Lappos, former Sikorsky/Bell famous person has often said on PPRUNE that they are different. He suggested that we call SWP "settling with INSUFFICIENT power." In practice, we just kind of lump them together for the sake of simplicity and because one is easier (and a lot safer) to demonstrate than the other.

 

Look, if you're really heavy and you're in a steep (below ETL) descent and you're at full power, you can still be descending into your own downwash without it recirculating. You're simply in a condition in which thrust required is less than thrust available to stop the descent. But if you had more power, you could. This is SWP.

 

But in true VRS, no amount of extra power will stop the descent because the rotor is ingesting its own downwash¹.

 

Why is this so hard for some people to grasp?

 

It's hard to demonstrate SWP because you have to be really heavy and power-limited. It's "easier" to demonstrate VRS...to a degree...some helicopters are harder to get into it than others. Nevertheless, the corrective action for *both* conditions is the same: reduce power and get some air flowing sideways through the rotor. So we treat SWP and VRS the same way even though they are fundamentally different conditions.

 

I have sat in a Bolkow on short-final, plenty of power to spare, wondering if all the vibrations and shaking were the onset of VRS. I have also sat in a loaded-to-the-max 206B, making a steep approach, coming in below ETL and at nearly full-power, wondering if I was going to have the power to stop the descent at the bottom. In both cases, you don't have a whole lot of time to recognize whichever problem is happening and take corrective action. And sometimes, you're too low to do much of anything anyway.

 

 

1. That's not entirely true. You can get into VRS even when you're fairly light. Helicopters with tons of extra power...e.g. UH-60's and the like...can sometimes "power out" of VRS because some part of the rotor is always producing lift.

[pilot#476398]

You’re correct, times change; very little knowledge in aerodynamics is needed on your part to fly the helicopter. So, you’re free to remain unfamiliar with, inexperience in, lacking knowledge of, and information about the profession in which you’re engaged and the aircraft you fly.

 

I know what they want me to know to be a safe and competant pilot,...and that's enough for me. I have no interest in learning this stuff to the level of an engineer, or physicist!

 

By the way, I'm from the "SWP is the same as VRS" camp. That other scenario, I pre-flight plan for, and do power checks to avoid, but have no term for.

[eagle5]

Why is this so hard for some people to grasp?

 

I'm with Nick, they're two seperate things, but I would call it, "settling due to insufficient power", or SDIP! The VRS, I would still call SWP.

 

What's so hard to grasp?

[iChris]

By the way, I'm from the "SWP is the same as VRS" camp.

 

The VRS, I would still call SWP. What's so hard to grasp?

 

Since both of you are from the SWP=VRS camp…

 

1. How about Tail Rotor Vortex Ring State, is that the same as SWP too?

 

2. Were did the term Vortex Ring State originate from?

 

3. If SWP=VRS why can we have one without the other?

Edited January 20, 2013 by iChris

[lelebebbel]

You're simply in a condition in which thrust required is less than thrust available to stop the descent. But if you had more power, you could. This is SWP.

 

But in true VRS, no amount of extra power will stop the descent because the rotor is ingesting its own downwash¹.

 

Why is this so hard for some people to grasp?

 

It's hard to demonstrate SWP because you have to be really heavy and power-limited. It's "easier" to demonstrate VRS...to a degree...some helicopters are harder to get into it than others. Nevertheless, the corrective action for *both* conditions is the same: reduce power and get some air flowing sideways through the rotor. So we treat SWP and VRS the same way even though they are fundamentally different conditions.

 

 

I get people to pull the helicopter into an out of ground effect hover, 100ft-200ftAGL or so, but tell them they can only use 'X' amount of power, with X being a bit less than what I think is required to hold the hover.

 

What happens is that the student slows the helicopter down, and until the last second it looks like the helicopter will actually be able to hover with this power setting X. In fact, they might even be using less than that. It takes most people a few seconds to realise that it was only the effect of the flare, and residual forward airspeed that was keeping the helicopter afloat. Once the machine is truly stopped, it starts to sink much like in all those accidents. At that point, there is no way to stop the descent with the remaining power, even if they pulled a bit more than X. It is settling with insufficient power (but not in VRS! Not unless you let the ROD get out of hand).

Only forward airspeed will save the day.

 

I think this little exercise is not 100% realistic, but not far off - and much more useful than for example that silly "VRS" thing they do at 2,000ft AGL, just to tick the box in the syllabus.

Edited January 20, 2013 by lelebebbel

[Wally]

I know what they want me to know to be a safe and competant pilot,...and that's enough for me. I have no interest in learning this stuff to the level of an engineer, or physicist!

 

By the way, I'm from the "SWP is the same as VRS" camp. That other scenario, I pre-flight plan for, and do power checks to avoid, but have no term for.

 

But they're not the same thing, both are considerations in preflight planning, develop differently in application. The remedy might be similar, but that's it. If I anticipate SWP, I might be able to plan around it- a flat approach to a flat elevated surface or a landing in or near ETL, for instance, and never getting behind the airspeed/power curve without recovery altitude in this case.

VRS is always a possibility in the real world, and you can develop it out of SWP. The FAA parameter is 300 fpm vertical descent, and if the pig fell thru at of above and you held it there, instead of the descent rate stabilizing at or near 300 fpm, it would accelerate even with limited power.

[THE_COYOTE]

In reference to an accident that is very close to my heart (Iron 44), I had a great discussion with an extremely high time S-61 pilot. He described the difference as Power settling (i.e. trying to arrest a decent and not having the necessary available engine power to maintain rotor RPM) and VRS a.ka. settling with power. On a the main topic I definitely think that the pilot ran out of power to arrest his decent; power settling. A more shallow approach without an aggressive pedal turn before may have avoided this incident.

[pilot#476398]

Since both of you are from the SWP=VRS camp…

 

1. How about Tail Rotor Vortex Ring State, is that the same as SWP too?

 

2. Were did the term Vortex Ring State originate from?

 

3. If SWP=VRS why can we have one without the other?

But they're not the same thing, both are considerations in preflight planning, develop differently in application. The remedy might be similar, but that's it. If I anticipate SWP, I might be able to plan around it- a flat approach to a flat elevated surface or a landing in or near ETL, for instance, and never getting behind the airspeed/power curve without recovery altitude in this case.

VRS is always a possibility in the real world, and you can develop it out of SWP. The FAA parameter is 300 fpm vertical descent, and if the pig fell thru at of above and you held it there, instead of the descent rate stabilizing at or near 300 fpm, it would accelerate even with limited power.

 

Its seems that some of you are hung up too much on nomenclature! It really doesn't matter what these things are called, as long as you learn how to recognize and handle them!

 

I'd say this discussion is making me "pissed", but some of you may think that means I'm getting drunk?