Vuichard technique for settling with power?
 

Anyone have anything to say about the Vuichard technique? According to Wikipedia:

I was flying with an instructor and a friend at the weekend and we had a for-real SWP, trying to hover OGE close to gross in an R44. (We were at or very close to redline, though my experience in other R44s is that HOGE at 1000 feet at gross is no problem, no idea why this one is different).

The recovery was simple and quick, but my friend got interested and asked me what I thought of the Vuichard technique. Since I'd never heard of it, I thought I'd ask here.

Claude's Maneuver
 

It actually works on any helicopter. Left pedal and right cyclic to pull out or vice versa. It helps. :ok:

Probably worth clarifying whether you are talking about recovery from VRS or SWP since they are not the same.

I'm sure that technique would work for VRS but not convinced for SWP (where you haven't got enough power to hover and begin to overpitch).

Didn't know it had a name....I was taught that technique back in the 70's by my flight instructor.

Just did it in direct comparison to "normal" recovery technique during a base check with someone the other day. It is really astonishing just how much quicker the recovery is and would recommend anyone to give it a try. In a side by side comparison both of us on board managed recovery from fully developed VRS within 50 feet consistently while the normal technique always required at least 100 to 150 feet. However it does feel a lot more violent going through the Vortices.
When it comes to SWP I don't think I'd use that technique though: pushing full left pedal, entering a 10-20° bank, exposing the whole fuselage to more drag by going sideways and the need to bring in collective would certainly aggravate any settling with power situation.

I am not questioning that the technique might or might not work.

I find that impossible to believe. Hawkeye0001, how long were you established in VRS for, and what was your ROD when you initiated the recovery action using this technique?

If your ROD lets say was only a mere 2000fpm in VRS, then a 50 ft recovery would take only 1.5sec, a huge deceleration.

Perhaps your definition of "fully developed VRS" may not be correct? I don't want anyone thinking they can recover from this condition in 50 ft, because in my humble opinion, that isn't possible.

Helilog 56
 

For both VRS and SWP?

Starting into VRS at 1,500' AGL we let it develop until we hit a descent rate between 800 and 1,100ft / min, started recovery at approx. 1,200' AGL and were able to arrest the descent by about 1,150' AGL give or take some 20ft.

Perhaps my definition is not correct, I'm sure that with a 2,000ft/min descent rate (if that is the definition of "fully developed" we go by) you are right in that the 50' quoted are definitely not manageable. But 1,100ft/min is bad enough in my book that you should have begun your recovery a long time before you even got to that point.
And the point is that in direct comparison to the method of lowering collective, accelerating forward, hit ETL, and then raising collective to climb out the Vuichard technique consistently saved us approximately 1/2 to 2/3 of the way on side-by-side comparision throughout 6 attempts of using each method.

The type I fly isn't even likely to get into VRS until it reaches a ROD of 900ft/min. At least, not according to the RFM, which advises pilots to avoid RODs of greater than 900ft/min at low airspeeds.

The one time I saw "proper" VRS on the Puma HC1 the VSI needle was pegged at the bottom, 2,500 ft/min or more.

Echo that. Bigger (higher mass) helicopters get into VRS at a higher rates of decent, and correspondingly require more height to recover. Simulating incipient VRS and recovery at trainer helicopter heights is only for the soon to be dead or unemployed. Ditto zero speed autos.

the coyote
Perhaps that depends on your definition of "recover"

Almost 50 years ago I flew with an ETPS graduate in a RN Wasp. He demonstrated fully developed VRS - and I do mean it was really fully developed - we started at 9000ft, commenced the recovery at about 8000ft and recovered at just above 4000ft with the ROD having been pegged to the bottom of the dial. No way can you recover from fully developed VRS within 50 ft!!!!

I do appreciate that a Wasp in auto is like a brick built outhouse anyway but it was a very sobering demonstration of how much height it took to get out of VRS. I shall remind him of that trip when we meet for lunch next month.

Thanks for the replies everyone. Very interesting. I'll ask the instructors where I fly if they know about it.

Not sure I follow the distinction between VRS and SWP. Looks as though the idea is that one is what happens in (e.g.) a steep approach, where you're descending at reduced power, while the other is what happens when you try to hover OGE and don't have enough oomph to make it work (as happened to me). But it also looks as though Crab and Hawkeye are using them opposite ways round.

Aerodynamically, aren't they the same thing? The FAA Rotorcraft Flying Handbook has a section called "Vortex Ring State (Settling With Power)". The ASA book has the same section heading.

Shawn's book does make a distinction (p. 174) but then goes on to say "Vortex ring state is a more clear, precise definition". I think that what he's saying is that you can be in a situation where you don't have enough power to maintain altitude, without necessarily getting into VRS. Though if you're HOGE with no wind (or sort-of hovering with zero airspeed) then VRS must surely rapidly follow. (And he has a footnote which says "The term [SWP] is very misleading and won't be used. I'd ask you to remove it from your vocabulary.")

Nice and simply differentiation of VRS and SWP from Transport Canada:

The term Power Settling is apparently the equivalent of VR - SWP is different, as mentioned.

phil

I think the 'settling with power' term is used more widely in the Americas than in UK - don't know about the rest of Europe/world.

Often the consequence of not having enough power to arrest the RoD, or even achieve the hover, is pulling past engine limits until the Nr decays which just increases the RoD. That is why SWP and VRS are often confused and SWP accidents are often given a VRS cause incorrectly.

Theoretically if you have enough power to overcome the enormous rotor drag, it should be possible to get out of VRS just using collective.

It is disc loading that determines the speed of the rotor downwash and hence the RoD required to catch up with it and encounter VRS.

I think many demonstrations of VRS are stopped at the incipient stage (probably quite wisely) to highlight the stage at which recovery should have been initiated rather than going the whole hog into full VRS.

That could be it - all the instructors I've worked with, about 6 (all in the US), have used this term rather than VRS, though they know what VRS is. And indeed the FAA evidently uses the two terms interchangeably.

My understanding is that a true fully developed VRS is pretty seriously scary, whereas incipient VRS is no big deal. Just like a fixed-wing spin, really. And in both cases, the only reason you'd ever get in the fully developed flavour is either because you really want to (and presumably know what you're doing), or because you just have no idea what to do at the incipient stage (in which case, you're seriously out of luck!).

Anyway thanks for all the answers, lots to think about.

On learning to fly over 50 years ago, we were taught to do VRS recoveries. When the rate of decent was around 4000 to 6000 ft/min we would initiate recovery by lowering collective & pushing stick forward. When the air speed came alive we would pull the stick back & apply power to initiate a climb.

The point was made very strongly that the tail rotor hadn't stalled, only the main rotor, so if the cyclic was too sloppy & wouldn't nose down, we would put in a boot of pedal as all you wanted was airspeed & it didn't matter in which direction you were going. Worked every time!

Because of this confusion in terms ( SWP / VRS ) Transport Canada requires that an ACP ask this specific question during a PPC. The FAA really makes no distinction and as mentioned uses the 2 terms interchangeably when in fact they are as different as chalk and cheese.

VRS requires 3 things to come together. A relatively high rate of decent ( most modern helicopters this is at least 500ft/min). Partial power, and airspeed less than translation. Gross weight is not a factor and actually it is easier to get into VRS at a low GW.

SWP or PS as it is also called is simply a condition which requires more power than is available for the conditions. Think loading your 206 to gross at sea level and then trying to land on a mountain at 10,000 ft on a warm day.

It is a factor simply because it is easier to get into VRS at lower weights - low weight equals less downwash speed (less collective pitch) equals lower RoD required to catch up with the downwash.

Pilots can be lulled into a false sense of security flying a lightly loaded helicopter - they have bags of spare power and VRS is often the last thing on their mind.

Just the sort of time you might be tempted to continue with a steep approach that you would otherwise have gone around from - you've got loads of power so where's the problem - if you had been heavy, you would be more careful about your approach.

You are correct Crab....actually I should have said "high gross weight is not a factor" Thanks for clarifying that...

Wow! That is 3555 knots downwards.....What sort of helicopter was that? :ooh:

(Reminds me of the Specsavers advert where the bloke and his wife get on a roller coaster by mistake while he eats a cheese sandwich. What sort of cheese was that?). :E

Sorry, Nigel ;)

Settling with power term in the US
 

might have come from the preponderance of Vietnam era pilots at one time. Not at all unusual for a Huey driver to be heavy, pulling all the power the engine would make, be within limits, and still not have enough to arrest the descent. I don't recall ever hearing the term VRS at that time although we did demonstrate and teach recovery in Primary, in a TH 55.

I was taught to recognise that as over pitching, not VRS!

It's not overpitching until the Nr decays:ok:

Oh, but it will.... :p

FFS this again! I get the feeling that either modern day helicopter pilots get less and less training in these areas or FI's are more dumbed down than before and don't understand it themselves. Other than CFIT, I would argue that these two phenomenon's alone - are one of the biggest causes leading to a crash.

STILL this subject rears its ugly head. One would have thought that over the years almost all 'experienced' helo drivers are acquainted with the issues, done their own research or spoken to someone who fully understands it. Probably the best "experienced practitioners" for flirting with IVRS - are long liners and cattle musterers, who can sense these states almost instinctively if they live long enough!

For the "Nth" time and for as long as it takes to educate the lumpen proletariat, here it is all over again:

http://www.pprune.org/rotorheads/116...merged-14.html

Go straight to post 261 by Nick Lappos who used to be Chief Test Pilot for Sikorsky. This is 'probably' the closest anyone will get to trying to illustrate the difference between VRS and SWP.

In a nutshell and K.I.S.S:

VRS: This requires a descent (usually >70% of the induced flow). It requires a LOW fwd speed and finally it requires application of power (You cannot have VRS in auto). 3 FACTORS.

SWP: Descent needed, Velocity (vertical or fwd), Application of power. 3 FACTORS.

To the ignorant (and I chose that word carefully), they appear similar. Far from it.

What then is the difference (drum roll):

VRS is an AERODYNAMIC phenomenon - it is to do with developing blade stall/induced flow/big green arrow movements/vortices.
SWP is a PERFORMANCE phenomenon - it is to do with the engine(s) NOT providing enough power to arrest the 3 defining factors.

Both require height to recover. Fully developed VRS requires 1000's of feet. Let no-one be in any doubt about that.
SWP requires a tiny fraction of this amount.

{Tail rotor effectiveness (TRE): diminished as it enters dirty air from the main rotors during VRS.}

Of course if mother earth chooses to intervene during the recovery phase............:rolleyes::rolleyes:

See you all here again in 2021......:ok:

Well done TC :ok:

TC - you are right - there's a lot of junk information around including your incorrect but confident statement:

"Fully developed VRS requires 1000's of feet. Let no-one be in any doubt about that." wot no-one?

It's as bad as the ETPS story further up 4kft to recover - please, really, come on, get a grip man.

If you actually thought you were plumetting in a barely controlable helicopter in some almost impossible VR then:

In ('Fully Developped') VR with a RoD in the order of an autorotative RoD then simply lowering the lever to eliminate Positive Induced Flow and make Negative Induced Flow places you in a docile Autorotative State, the recovery from which into powered flight doesn't take more than a few 100s of feet - duh!

From fully developed VR to climb can be accomplished in better than 120ft (indicated, ie not taking account of local pressure errors due to local static pressure changes between the 2 states) - of course none of that actually has much to do with what you do about VR at say 50ft on short final - other than to impress upon the happless pilot that it is worth avoiding scenarios that lead you there.

(2 factors for VR: 1 power 2 directly opposing airflow)

AnFI, serious question for you:

Have you ever been in VRS that has developed past the initial phase, lowered the collective as you say is the smartest thing to do and tried to "fly out of it" but for the first few seconds nothing happens and the VSI is still pegged? You move the cyclic either far forward or off to one side but the helicopter doesn't respond to your control inputs all the while the flying brick that you are seatbelted to continues to plummet towards cumulo-granite? Have you ever experienced this?

hearing you TC, ......and it is almost time for the LTE v LTA to start up again...

:}

It has already been hit on the head, asking "Why haven't the experienced pilots passed this knowledge on?"

BECAUSE.....

The instructor you are flying with has only 100 hours more than you do. He doesn't have any experience. Zip. SFA. NFI.

ShyT
There's a smart one in every family! Definitely a grey hair moment, now fixed!!:ugh:

The S55/Whirlwind was great to demonstrate VRS. As you applied a little power the helicopter would shake & go into VRS ( that's if the other factors are present ) The ROD would settle about 3000 ft/MIN, apply lots more power, then the shake would increase & the ROD could get up to 6000 ft/MIN. Remove all power & out she comes, get some airspeed & climb away if required.

Oh, how refreshingly unusual - NOT!

A certain self-professed expert in all matters aviation and especially aerodynamic (yet with no visible CV) rubbishes a bunch of very experienced helicopter pilots (most of whom are well qualified instructors).

Once more the pronouncement of his theory which is supposed to trump ACTUAL experience.

Absolutely no Frickin' Idea who I mean????

AnFI - so you are calling me a liar? I was there on that occasion and experienced the 4000ft to recover. With that accusation and your incessant ramblings about how two engines are unnecessary I really can't be bothered with reading any more of your drivel. Be proud that you are the only person on my ignore list as of now. PPRune suddenly becomes a better place.

AnFI

As a few of the posts have already indicated, you are just wrong on this. It WILL take a frightening amount of height to recover from VRS in a higher mass helicopter. And autorotating out won`t fix the problem in a hurry either, because that will also be an auto with a huge ROD. In fact, the odds are that the VSI wouldn`t even indicate the real value, because it will run out of numbers.

TT

But presumably autorotating out will mean instantly no longer being in VRS.
Maybe not a full recovery anytime soon, but no longer in VRS non the same.

Autorotating out is unlikely to have any advantage over other methods of recovery, including the method which is the subject of this thread. If you don`t have the height to recover, which aerodynamic condition you were in will be of little consolation when the ground comes up to bring events to an ugly end.

Well all I can say I have been in full VRS once, terrifying .
In a S300 had demonstrated recovery from incipient state with a ROD of 800 ft a minute to a student and let him recover 6 times. All from 3000 ft agl. Recovery was to dump lever and forward cylic.
Decided to do one last one, as a relatively young instructor had hands close to controls but not on. Had heli at 3000 ft started to go into incipient state, ac shaking pitching and rolling ROD 800 ft min asked student to recover, his action was to apply max collective......... f..k me. We were suddenly falling tail first, from seeing mother earth in a normal plain to sitting with one' s back to her in a split second is a bit of a brown trouser moment ! IVSI almost instantly went to 3000 ft a min. Lever fully down, cylic full forward nothing happening still falling tail first. Could see ground coming up to met us very quickly, applied full left pedal ( don't know why instinct maybe or nothing else left to do ), instantly from looking up at the heavens now looking straight down at mother earth!! Ac then seemed to pick up speed ( don't remember too much ) then stopped shaking, full power applied and levelled the shop at about 200 ft from ground. Student then commented would you like to punch me when we get back to the field.
As they say by the Grace of God. Cant really say I thought too much about what happened as it happened unbelievably quickly !!

Crab
The poster is an experienced helicopter pilot (at least 30 years) and a well qualified instructor/examiner.

NB: Just for info. I don't have sufficient knowledge or experience to join the discussion.