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Old 10th Mar 2015, 00:35   #1 (permalink)
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Vuichard technique for settling with power?

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

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Another recovery technique is called the Vuichard Recovery Technique: initiate the recovery by increasing the collective to takeoff power, then simultaneously applying power pedal to maintain heading and opposite cyclic (15-20 degree bank) cross controls to get lateral movement. As soon as the rotor disc reaches the upwind part of the vortex the recovery is completed. Average loss of altitude during the recovery is 20-50 ft depending on the duration of the recovery procedure.
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.
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Old 10th Mar 2015, 09:28   #2 (permalink)
 
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Claude's Maneuver

It actually works on any helicopter. Left pedal and right cyclic to pull out or vice versa. It helps.
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Old 10th Mar 2015, 10:18   #3 (permalink)
 
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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).
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Old 10th Mar 2015, 13:52   #4 (permalink)
 
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Didn't know it had a name....I was taught that technique back in the 70's by my flight instructor.
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Old 10th Mar 2015, 16:39   #5 (permalink)
 
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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.
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Old 10th Mar 2015, 23:34   #6 (permalink)
 
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I am not questioning that the technique might or might not work.

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recovery from fully developed VRS within 50 feet
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.
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Old 11th Mar 2015, 05:14   #7 (permalink)
 
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Helilog 56

For both VRS and SWP?
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Old 11th Mar 2015, 08:23   #8 (permalink)
 
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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?
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.

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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.
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.

Last edited by Hawkeye0001; 11th Mar 2015 at 08:37.
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Old 11th Mar 2015, 10:55   #9 (permalink)

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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.
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Old 11th Mar 2015, 13:28   #10 (permalink)
 
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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.
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Old 11th Mar 2015, 13:52   #11 (permalink)
 
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the coyote
Quote:
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.
Perhaps that depends on your definition of "recover"
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Old 11th Mar 2015, 14:03   #12 (permalink)
 
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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.
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Old 11th Mar 2015, 18:08   #13 (permalink)
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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.")

Last edited by n5296s; 11th Mar 2015 at 18:36.
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Old 11th Mar 2015, 19:12   #14 (permalink)
 
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Nice and simply differentiation of VRS and SWP from Transport Canada:

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There are some uninformed pilots [sic!] 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.
[...]
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. Always control your rate of descent carefully on these occasions, and make sure an escape route is available.
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Old 11th Mar 2015, 19:32   #15 (permalink)

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

phil
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Old 11th Mar 2015, 20:18   #16 (permalink)
 
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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.
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Old 11th Mar 2015, 20:43   #17 (permalink)
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I think the 'settling with power' term is used more widely in the Americas than in UK
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.

Quote:
I think many demonstrations of VRS are stopped at the incipient stage (probably quite wisely)
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.
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Old 12th Mar 2015, 03:57   #18 (permalink)
 
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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!

Last edited by Nigel Osborn; 13th Mar 2015 at 07:25.
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Old 12th Mar 2015, 05:32   #19 (permalink)
 
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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.
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Old 12th Mar 2015, 06:49   #20 (permalink)
 
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Gross weight is not a factor and actually it is easier to get into VRS at a low GW.
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.
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