Power settling?

[Irlandés]

Could someone venture an authoritive definition of Power Settling? It seems that half the people I speak to consider Settling with Power and Power Settling to be one and the same and the other half seem to know they're different but then go on to give varying different definitions of Power Settling!

Thanks!

Irlandés

[Arm out the window]

Well, I'll put myself up to be shot down by saying that I reckon settling with power, power settling and vortex ring state are all the same thing.

[Nick Lappos]

Usage varies as to terms, but the training manuals agree with Arm.

A class of instructors seem to teach that "settling with power" has something to do with power limitations, loss of rpm and settling short on approach, but they only help to confuse things.

[Big Beres]

In the "Principles of Helicopter Flight" by Walter Wagtendonk states that Settling with Power and Vortex Ring State are one in the same thing....No mention of Power Settling though!!

[[email protected]]

Irlandes, are they talking about recirculation when they say power settling? It can be as much of a gotcha as vortex ring if you are operating into small sites with fences and buildings around them (Northern Ireland forts for example). Someone once bounced a Wessex 5 feet back into the air in a lovely place called Forkhill when he flared to the high hover just above the fence and then ran out of power as we sank into the fort and recirculation help us plummet earthwards. Thank God for the Wessex undercarriage!!

[Irlandés]

Hi Crab,
yes, now that you mention it, recirculation was one of the explanations given for 'power settling' by one of the more authoritive sources I know. Someone else said that it was coming in to land without enough power but I think that's just called 'bad power management'! ;)

Just to add fuel to the fire here is an excerpt from an article on VRS by Ken Armstrong that appeared in Issue #11 of Pacific Rotors...

"When More Power Seems Like Less - There is some disagreement in the rotary wing world about the terms settling with power and power settling with various pundits defining each differently. However for this treatise, I will use the generally accepted terms settling with power and vortex ring state to define the same condition. Power settling will be discussed separately as a separate installation."

But I never got to read that 'separate installation' so never found out exactly what power settling was!

Irlandés :rolleyes:

[Xnr]

The Canadian or should I say Transport Canada definition does not treat each the same.

Settling with power is a situation that develops when the power available is not enough to arrest your rate of decent.( i.e. take off at sea level and climb to altitude, attempt a landing at lets say 6000' asl, have not consulted the charts and you find yourself in a situation where the power available cannot arrest your rate of decent.)
You can also create the same situation by making a hot approach with a high rate of decent and find yourself behind the power curve by the time you meet mother earth.
How many of you guys have entered a confind area with a sling load and felt that sinking feeling.....settling with power once again. Lets face it if you were in VRS in that situation you would be a statistic.

VRS is created by decending (300-1500 fpm, type dependent) at low airspeed, (0-30 knots, type dependent) , with power applied. You end up decending through your own downwash thus creating the vortex ring.
Recovery technique is to lower the power and gain airspeed. You can also autorotate but I like the first option better.

Therefore, (in Canada) VRS and Settling with Power are not considered as equals.

Settling with Power should be called "Settling without Enough Power"

Cheers

Xnr

[flygunz]

The terms 'vortex ring'(European) and 'settling with power'(US) are definitions for the same situation, i.e significant vertical descent (>500fpm) with power applied(>50%tq) at low airspeed(<30ktas).
Having taught in the US and UK I found i could use the term settling with power effectively when descibing how to recognise the early stages of the effect in order to not let it manifest into the full and irrecoverable condition. Incipient vortex ring state as a term falls a little short for me and I save that for the full monty.

Power settling once again is a US term that is sometimes used to descibe limited power operations, i.e that point during the approach when a max power limit is reached and technique takes over as the means to arrive safely.
It can be confusing and I dont tend to use it, after all limited power is precisely that, limited power.

[canuk1]

The way to go XNR!
I do totally agree with you...hey guys, here in Canada we do treat settling with power and VSR as two different things because they are!
Settling with power is when you don't have any more power available to stop de descent of the helicopter(even if you are within de 300fpm and less than 30 kts).For this to happen you need a combination of the 3 H: Hot High and Heavy!
On the other hand, VRS , can happen anytime, you can be as light as a feather and at Sea Level....that if you descent at more than 300fpm and at less than 30Kts you are flying in your own downwash! As my instructor at Canadian Helicopters said VSR is as if you farted in your own sleeping bag!
Hope it helps!

[flygunz]

It would appear that you guys in Canada use the term settling with power for limited power situations. My two Principle of flight bibles are quite clear about the two terms (swp & vrs) as the same.
What fundamentals of flight reference do you use which states the case differently?

[Irlandés]

So summing up this particular can of worms so far, here are the various different takes on the situation...

1. VRS is the same as Settling with Power. Power Settling is a Recirculation type situation.

2. VRS is the same as Settling with Power. Power Settling is 'Settling without enough power'.

3. VRS is not Settling with Power. Settling with Power is 'Settling without enough Power' (Xnr's suggested definition). So what is Power Settling according to this posture?

And when I originally posted I assumed that the VRS=SWP part was beyond dispute! Apparently not. That said, all the texts I've ever read have treated the two as one and the same. It was the Power Settling I was worried about! I suspect that because the two terms are so similar people have been using them interchangeably for years without suspecting that they could be in fact two different conditions. Then you end up with 'old dog, new tricks' syndrome. Just a possibility of course.

Anyway, all this has given me a headache. I'll find something easier to think about. Nuclear fission perhaps... ;)

Irlandés

[John Eacott]

XNR has the correct interpretation. Vortex ring is one thing, Settling with Power another.

Another description of settling with power would be the SA365C, with the fixed pitch limit on the collective, where a moderately hot approach could (and sometimes does) finish with plenty of engine power available, but unuseable because the collective has reached its physical limit. Strange bit of French design, which has caused a few heavy landings along the way. I'm sure that there would be other helicopters with a similar feature.

[Steve76]

Is it necessary to go back down this well trodden road?
Do a search on PPRUNE for this subject, read Nick Lappos's site and you will have plenty to do for the next months.

[Nick Lappos]

Unfortunately, the ad hoc definition of "settling with power" as a purely power phenomina is not correct, in Canada or elsewhere. The idea that such a definition is needed for "an approach where insufficient power is available" is right on, but settling with power is not the term.

Check here:
http://www.dynamicflight.com/aerodynamics/settling_power/


XNR, do you have a reference to a publication of the Canadian usage of settling with power for a purely power problem?

Evidence of the confusion caused by misuse of the terms is shown by the confusion about recirculation, which is the cause of VRS/Power settling/settling with power. It is the recirculation of the downwash that causes all the misery of VRS.

We should actually agree on a term for the falling through on an approach that is caused by insufficient power, and stick to it.

Otherwise, we should declare this thread to be "Condition Alpha" and simply re-run it every 3 months, which is about how long it takes PPRUNE to forget the last time we all tossed this ball around!

[Hingeless Rotor]

There is no way I can wait 3 months to toss my balls !!

[Irlandés]

Steve76,
I'm not naïve enough to think I'm the first person who has asked this question nor will I be the last and sorry about flogging a dead horse but when I went to do a search on power settling, I couldn't find the search button (ironic, isn't it?). I could have sworn it was on the top of the page. Anyway I subsequently found it after posting. Is it my imagination or did it get moved?? :confused:

Good idea Nick about coining a phrase that everyone can agree on. I mean it can't be that hard to make all the world's helicopter pilots agree on something. Ha ha! :D For what it's worth, here's my suggestion: "Power Deficit Landing". Any takers? :rolleyes:

Irlandés

[Randy_g]

How about looking to Mr. Webster to help. :D

Settling:

v. intr.
To discontinue moving and come to rest in one place.
To move downward; sink or descend, especially gradually"

When one uses the word settling in it's proper usage, one tends to think of settling with power as a power limitation problem. Taken to a bit of an extreme every landing we make is a form of "settling with power". Just because a word is used in a book does not make that word correct, if it isn't used properly.

Cheers

http://randyspics.tripod.ca/gifs/naughty.gif Randy_G

http://randyspics.tripod.ca/gifs/man_grilling_hamburgers_sm_wht.gif

[S76Heavy]

IMHO, landing hard due to insufficient engine power/Tq available carries the label "pilot error". I know you've either done it, or will in the future (and I have, no mistaking that), given the nature of the job, but it is as simple as that. Unfortunately..:(

But Hot Approach sort of sums it up and is nice and concise. Any takers?:D

[Randy_g]

S76 Heavy VRS is usually caused by "pilot error" too (and is 100% preventable too). As you say the label of pilot error is usually attached to any hard landing due to insufficient power. As we all know, an error may not have been made at all.

For instance; you are on short final, and have done every single kind of recon known to humans, you note where the prevailing wind is, and the surface wind, and then the wind can still change suddenly and become a downdraft causing a hard landing. I would be rather cautious to call that kind of scenario "pilot error". You only have to ask anyone who heli-skis, or just flies at something higher than sea-level, and a hard landing can be just a gust away.


Cheers

http://randyspics.tripod.ca/gifs/naughty.gif Randy_G

http://randyspics.tripod.ca/gifs/man_grilling_hamburgers_sm_wht.gif

[S76Heavy]

Randy G, been there, done that. After all the trouble I went through to check everything, I found that it wasn't enough. I was lucky in the sense that we stopped inches off the surface, saved by the ground effect.
If something breaks it will be labeled pilot error, that's my point.
I am NOT pointing fingers at anybody who has had the misfortune.
Perhaps me flying mostly at sea level with (usually) no power shortages will explain why I chose to express myself that way. But hey, better men than I have been caught.

But I was taught that "settling with power" =VRS. I understood that to mean that "even with application of lots of power, the A/C will settle towards terra firma". Therefore I hope that a less confusing description will be found soon.

So I hope no offense taken, as it was certainly not meant to offend.

[Nick Lappos]

The term settling is certainly not in dispute, we could easily settle on a definition (Ouch!) but the idea that power settling means too little power is not just cross-wise to current usage, it is logically backwards.

In the case where you pull up the collective and not enough engine exists to cash the check, the term could be "falling through" which is a term we used in Vietnam to describe the foolish attempt to become OGE with IGE power.

This term also tells what it feels like, is not confused with any vrs/settling terms.

The concept of something being pilot error is not worthy of our consideration. Let he who is innocent cast the first stone. Today's helos provide precious little help to the pilot.
In Comanche and S-92, the torque gauge is marked with two variable indices which are computer updated. One marks the power available from the engines under current conditions (alt, temp, engine degradation), the other marks the power required to hover OGE under current conditions (alt, temp, gross weight). If the required is below the available, you are cool, and will not fall through. If not, try to not be terminating OGE.

[Irlandés]

That sounds like a very useful gauge. How much is it? ;)

[FlawTolerant]

$15 million U.S. !! :)
Comes with it's very own S-92 wrapped around it!

[S76Heavy]

Falling through, I could go for that description. Unfortunately, I still fly yesterdays helo, not todays..;)

[[email protected]]

What is wrong with the term overpitching for the situation Nick describes, where the collective position writes a cheque that the engine power can't cash - the Nr will slow down unless the lever is lowered but if you lower the lever you will go down faster. It is a no win situation and can be avoided by doing the sums to ensure you have an adequate power margin for landing/hovering - the standard in Brit Mil Ops is HOGE plus a 5% Thrust Margin to counter slight turbulence/ mishandling/ windshear etc
We do not use the term settling with power or power settling in UK and therefore avoid the confusion. VRS is VRS, running out of power is running out of power - c'est tout ca! Recirculation (just at the tips due to obstacles not at the root as well like VRS) can cause you to run out of power because it increases your induced flow, but you have still run out of power. If your engines torque/temp/fuel flow limit the Nr will decay (overpitching)- if they do not you will overtorque/temp (bollocking from the boss).

[Whirlybird]

I thought I understood all this stuff till I read this thread; now I'm totally confused. I just remembered why I usually ignore these sort of threads. :confused: :confused: :confused: :confused: :confused:

[Nick Lappos]

Crab is right, again. Overpitching has been around, and is a good term. Regarding margin above OGE power to help you really do the mission, the US Army uses 500 ft/min climb rate, which is almost 10% power margin. Power or climb might be a better margin than thrust which is weight, although any will get you safer. I have found out that a 2% power margin is needed to turn an OGE hover into a vertical climb.

Whirlybird,
Don't be confused. We have discussed the fact that Vortex Ring State has three names (settling with power, power settling, and vrs) and that we have no name for the plain old garden variety smacking of the ground when you try to terminate an approach without enough power (except in Canada, where they are reported to use settling with power). Terms have been suggested, overpitching seems to be there already.
Up to speed?

[flygunz]

Unless you're Canadian there should be no confusion whatsover, VRS and SWP are the same. I like the time honoured term overpitching as it sums up limited power exceedence very well. Its also very English, almost a cricket term, perhaps we can find a use for the term googly and bouncer!:)
Crab, even though you're a bit blue you aint so bad after all!!!
GB.

[Irlandés]

Nick,
your words to Whirly might be falling on deaf ears. She didn't seem too enthusiastic about revisiting this thread! :rolleyes:

Irlandés

[Whirlybird]

Nick,
Nice summary, thank you.

Irlandes,
I can rarely resist revisiting any thread I've contributed to. ;)

[the coyote]

Does it really matter what the terms are?

Understand the parameters for VRS (or whatever you want to call it) and dont' mix them all together

Understand when your limited on power and why (hot, high, heavy, OEI etc) and and don't get your bird out of its own depth

Are we pilots who know our stuff or literary critics?

[S76Heavy]

Coyote, I think most of the pilots on this forum know their stuff very well. But a thread like this allows us to explore several ways of thinking about a subject and hopefully leads to a better understanding of the subject, or to another thread about a related subject. I see it as akin to the crew room chat, where every now and then I pick up a little gem that helps me improve my flying ability.

And if you get bored with it, just stop reading.

[SASless]

Nick ol' buddy.......if I am using "x" amount of power for my HOGE....and I apply "X + 2%".....you state I shall now ascend vertically.

I accept that statement in total.

What happens if I apply "X + 1%" or "X + 1.5%"........would I not also ascend vertically but at a slower rate ???

Or did my alcohol ravaged brain miss something....honest...I read it two or three times.....and still got the same impression that you stated a 2% power margin over OGE was required to ascend vertically from a stable OGE hover.

Now I only flew Chinooks and being tandem rotor....they defied several laws of physics and commonsense but.....it seems to me...if I apply power in excess of that required for a stable...steady OGE hover....the birdie goes up.....! What am I missing here?

Also....I assume the fancy dancy computer whizbang on the 92 requires some manual input for aircraft weight.....or you got squat switches or something that senses the actual ramp weight of the aircraft? Now assuming that same 92 is engaged in Offshore Oil Operations.....using the GIGO theory of computers....just how reliable are those performance figures going to be. (You ever seen an oilfield scale that was accurate to within a few hundred pounds per item?) Daily I get to watch some knuckle draggers stagger under the weight of their 20 lbs of baggage which consists of a Snap-On four component roll around tool box worth of tools.....stuffed into a duffle bag. The thought of having such a lovely device fills me with joy....but I know the helicopter operators will still want to ignore the numbers because that means they will have to cut one passenger or something equally silly.

[heedm]

Post becoming big time anti-Canadian, thought I better step in. Gloves off.

Consensus seems that there are two effects, one where air recirculates, another where it doesn't. With both of them the helicopter descends and sufficient power to normally stop the descent is applied. Yes, in Canada we call these VRS and SWP respectively. Most of the world uses VRS. Some strange types confusingly apply at least two names to the first condition of flight mentioned. They're the ones that screwed up the terminology.

Overpitching is used elsewhere to describe the second condition. A comment was made that since its already in use why not adopt it. NEWS FLASH, same argument can be said for SWP.

There's also the 'pull out the dictionary' argument. Settling with power would mean very little if it described a condition where a small amount of power were applied. Perhaps the intent of that terminology was settling with FULL power, or settling with NORMALLY SUFFICIENT power. I'm not protecting my country, just don't see what the big deal is, eh.

Pick up stick, pick up gloves, five minutes and a game misconduct....worth it. :)


p.s. Not really mad, just wanted to join in.

[flygunz]

One thing I'm not is anti Canadian, even though I still bear a scar from a lively albeit hazy night in the Asinoboa club in Medicine Hat!
My view is clear and I'll stick with my understanding, what I want to know and have asked for here, is a reference that backs up what ya'll saying. Simple.
Asking for a reference is not a UK trait but the southern rebel in me just kicks in now and then.
;)

[the coyote]

S76Heavy

Good point and I agree with you. I was trying to emphasise that as long as you understand thats the most important thing.

Words don't seem to come out right when your having a bad hair day.....

[S76Heavy]

Coyote, could not agree more with your last..:D

[helmet fire]

Love this old hairy monster!

I like calling a spade a spade, therefore I vote for calling the downward fall through your own vorticey "Vortex Ring State" 'cause that is what is happening. I reckon that all the talk of settling with power has simply confused too many people - this thread is a case in point.

And I dont find nothin "settling" about VRS at all!!:eek: :D :D

I am less a fan of the suggestion to use "over pitching" when terminating with insufficient power though. The reason is that I do like to call a spade a spade. Over pitching is still used to describe an actual state - when you have increased collective pitch to the point that RRPM begins to droop - ie you have "over pitched". I agree that this might cause you to fall through your termination, but it might also occur during take off, or especially for the piston guys, any time you have forgotten to roll a bit of throttle on when you have increased pitch.

Perhaps we could call it what it is: terminating with insufficient power! or Attempting to take off with insufficient power! Or attempting to [insert manoeuvre here] with insufficient power! How about that?

One of my old instructors used to call it "Engine failure: the engine failed to produce the squillions of horsepower required to complete the attempted manoeuvre"
:D :D :D :D

[Nick Lappos]

SASless:

I base the comment about +2% for vertical takeoff on my own experience, and invite you to try it and see what happens. On a still morning in the tropics, I found that charted OEI power produced a steady 60 foot hover in an S76A. If I carefully squeezed 1% more, the aircraft went up to 70 feet and stopped, then settled down to 50 or so, then climbed back up to 70, and sort of hung there. It took+2% to keep the aircraft actually moving up and out of the hover.
If I used OGE power only and gently lowered the nose to fly away, virtually no descent occurred (unlike IGE takeofffs). I could immediately climb when I got to about 5 knots, and by 10 knots, the climb rate was very nice (maybe 300 to 500 fpm).
Conclusion: OGE power means OGE power, not vertical takeoff power.

Go ahead, ask me why 2% is needed and not 1%.

OK I'll answer your question! I dunno.

Nick

[Irlandés]

How about this idea: In an ideal OGE hover the average inflow angle is a constant. If you bring in a small amount of power (say 1% above OGE), total rotor thrust increases slightly, enough to start a slow rate of ascent. As we know, the slow rate of descent will cause a small increase in inflow effectively trying to negate that rate of climb. Is it possible that there's a very small range of values (less than 2% above OGE) where this inflow actually succeeds in preventing a sustainable rate of climb? Instead you get this situation where the aircraft oscillates between trying to climb, realises it can't, settles back down again, tries again etc. ad infinitum. Are the terms 'phugoid' or 'hysterisis' applicable here?

I've always likened an OGE hover to being half way up a stationary escalator. If you start walking towards the top of the escalator, suddenly it starts moving down (increased inflow) but normally you're walking fast enough to make progress up the escalator to the top (OGE +2% Power). And the opposite holds true. Start walking down and the escalator starts moving up (decreased inflow) but not enough to arrest our rate of descent. We get to the bottom.

Is this total hogwash?? Be honest, I can take it! :)

Irlandés