I don't know why you think you'd get flak for adding some real-world experiences to the mix - out of interest what was the helicopter type you were flying?

Sounds like you invented the Vuichard technique before he did:)

Did a similar exercise at night using a Smoke Stack, NVG's, and FLIR.....hover at several assigned heights above the stack (using FLIR to peer down the inside of the Stack for position and RadAlt for height) and hold position for a minute or two until told to move up to the next height.

We were not told the reason for the Test Program.....as we did not have a need to know....as it was at a sensitive location.

I can only imagine how hard maintaining position using a laser must have been....as we had far more tolerance but far less accurate a measuring system.

Odd thing....we never experienced VRS.....unless only in the incipient stage. Light aircraft with ample surplus power margin and I always used a heading into the prevailing wind as that made the exercise very much less a chore.

Edit: Upon some reflection I recalled there were onsets of some loss of control....felt as sloppiness in being able to control Pitch and Yaw....always combined with a loss of height...but never an elevator ride kind of loss of height.....perhaps we were just powering out of it as we accelerated forward into cleaner airflow through the rotor system.

It was pretty much an Instruments only process with the added cross check of the FLIR Screen.

I am guessing our target was about a Three Foot Diameter hole at the top of the Stack.

The Boffins sure seem to have an uncanny ability to conjure up challenging tasks for us lesser beings to perform.

At times it allows you to empathize with a Lab Rat.

It was a AS350 D Crab.
Starting from 100 ASL to 8000 ASL Temps -20 to +25C. Terrain100 ASL to 1500-2000.
Well some folks are going to say that entering VRS in still air and zero rate of descent is impossible.
In discussion years later with a very experienced and well respected test pilot he was surprised to hear of it but thought that it was just amazing that the circumstance was created. The ‘Laser’ keeping the aircraft in a +- 24 inch hover for extended periods and the aircraft being tracked with a theodolite. The chance to operate in the conditions described and stay in VRS for up to 1-2 minutes try various things and observe results was a unique opportunity. He said that they had never even thought of doing it and it would have been a separate test programme during which it would have been difficult to achieve the test parameters.. I agreed totally with him. It was an interesting thing but not worth the candle to spend time to explore. In the end what would have been the benefit of it a except the “Been There Done That” T-shirt.
You always lost the ‘Laser’ dot when it happened so you had to descend back down to ground level so staying in VRS was quick way to get there. I found exiting at a +-45 degree from aircraft heading with a +- 10 degree nose down attitude to gain fwd speed seemed to work best. You could exit by entering autorotation but this involved a considerable height loss. Exiting fully developed VRS with power applied and fwd speed was the most easy but when you are looking at VS anywhere from -1500 to -2500 it is going to take TIME and ALTITUDE to return to straight and level flight. As I stated before aside from the sloppy controls the aircraft never entered any unusual attitude or did anything scary. It seemed happy in the state it was in, no RPM, Torque or heading changes.

Fascinating Captain to quote Mr Spock:)

I wonder if there was some convective updraught that brought your downwash closer?

It doesn't matter, you were there and experienced it repeatedly with time and height to experiment a bit.

Would it be fair to say you never got it out of VRS in 50' -100'?

I can imagine a light 350 doesn't produce a very powerful downwash - I've only flown the BB version.

Where is a really smoking engine when you need one. To see the airflow around that ship would have been fascinating.
How to get VRS without descending? Something I really like to try. But let's think about it. In a very light ship, one should be capable to pull more and more power to stay in place, but the tip vortices could in this condition grow and have the desired effect. After all, there is never no lift. Could that be what happened here?

Given the huge range of density altitudes that albatross has described there must have been some occasions when high pitch angles (for high DA) would have produced strong tip vortices and high AoA at the root - classic VRS conditions if you then start to descend.

Here is a suggestion.

It is not only the tip vortices, but also the root stall that allows the vortex ring state.

The steady increase in DA would have increased the stalled area, perhaps to a critical state where there was not enough thrust to maintain height.

Once descent started, however small, there could be a flow up through the large stalled area of the rotor disc and VR was established.

Edit: Bah! Beaten to it by crab.

I would not try to do this purposely today. In fact I would actively discourage it.

Some of the stuff formerly normally done in daze of yore are now seen as, reckless negligence, dangerous and foolhardy especially by Lawyers, their evil spawn, ilk, minions and sycophants

It would never occur if you maintained even a very slow rate of climb once the customer had you in sight, some guys always did that .Sometimes the customer asked you to hover or even descend “on the dot”. It would not happen in a steady state hover if there was any wind to speak of. In the case I speak of I recall the following conditions were present. 0 wind, hover maintained for at least a minute with probability increasing the longer you sat there, very steady air mass with no or very little thermal activity either upwards or downwards. You would sit there happily pulling perhaps a steady 80 to 85 torque. once you got that “little flicker” on the VSI application of power only accelerated the process. When it entered VRS, which was not violent in any way but very abrupt with the VSI going to -1000+FPM in seconds. if you didn’t do anything except pull more torque the aircraft would just fall faster in the exhilarating vertical descent. You had to initiate horizontal movement to fly out of the vortex. Having at least your former hover power applied as you exited the vortex certainly helped stop the rate of descent ASAP as you flew back into good clean air.

I am told that they don’t even demonstrate fully developed VRS anymore in training. Much as they only demonstrate incipient spins in fixed wing. One had to be signed off in olden daze for full spins in order to get a private fixed wing licence and would be required to demonstrate competency during your check-ride.

NB Remember that VRS is not Settling with Power and can occur at very low gross weight.
. ( Now referred to as Mass for reasons known onto Gawd. I would have liked to be a fly on the wall at the long series of committee meetings where that earth shattering decision was made. “Gentleman, we must appear to be doing important things while in actuality not doing anything. We’ve beaten both the constant ‘Rad Alt Setting Changes’ and ‘change the font on the checklists to improve efficiency’ to death so it’s time change something else. Last year’s forbidding use of “Roger, Wilco, Over, Standby-One, CAVU, WOXOFF ” and other clear, concise but archaic terms was brilliant. Changing ZULU time to GMT and then immediately to Co-ordinated Universal Time was a stroke of pure genius. Any new useful but useless suggestions?”)

I wish there was a "Like" button at pprune......some of these posts would certainly earn some Clicks.

Great stuff albatross:ok:

Just one more comment:
It is all fun and games discussing VRS here but:
After the debate of best practice for avoiding VRS, Recovering from incipient VRS and recovering from fully developed VRS.
It is imperative that you have a proper technique in your bag of tricks.
If you encounter VRS in any state there will be no time to have a debate with yourself as to what you should do before things go from bad to awful.
Have a plan in place, carry it out.
Even if you just suspect you are entering VRS recover to a safe flight regime immediately.( IE Forward speed, altitude level or climbing, Power and RPM in limits. )
Fly safe everyone.

Am sorry to hear that, Was chatting to him in May, and his health issues seemed to be stable but still concerning at that point. Shawn was a refreshing character in test, and I will miss his input and comments. He was a fitting presenter of Rays lectures. Through to the start of 2021 he had remained active in helping test programs, working with the Turks last time we chatted.

This section was drafted by him for NTPS, back when Nadia and Sean were still involved in the place. Was a good alternative to FTM-106 Ch 5. He maintained his enthusiasm throughout.






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Now it is getting interesting.

why, what’s happening?

Well, Dan Gryder claims, and substantiates his claim in a recent YouTube video, that

- The latest (and several other before) VRS-related accidents are not caused by inadvertent entry into VRS but by people voluntarily going out to practise VRS recovery in flight.

- And that those people practising VRS recovery put themselves into full VRS, which directly or indirectly (eg, inappropriate control inputs) led to the accidents that he discusses (including the Miami Bell 429 EMS / training accident).

- That the high publicity around the Vuichard recovery technique (as promoted since 2017 in every Heli-Expo, also officially adopted by Robinson, and via Tim Tucker's efforts included in the FAA helicopter syllabus) and the premise that it is easy to use this technique to deal with incipient VRS, have triggered the wide-spread practising of VRS recovery across all areas of ab initio and recurrent training.

According to Dan Gryder, the NTSB misread a 2017 Bell 407 VRS accident, assuming that it was caused by inadvertent entry into VRS, whereby possibly the two pilots went out - only a few days after having attended Claude Vuichard's seminar at Heli-Expo 2017 - to practise VRS recovery in flight on their own.

Most importantly, the NTSB - believing that lack of training in dealing with VRS contributed to the accident - then proceeded to formally recommending more and frequent VRS recovery training across the board. In other words that the cure that the NTSB recommends (frequent VRS recovery training) in itself is the cause for the VRS-related accidents.

At the beginning of the video, Dan Gryder mentions several times that he isn't a helicopter guy and that is blindingly obvious from the rest of the video. He equates settling with power to VRS - something I hope that has been made clear is that they are similar but separate situations that superficially look the same but have different causes.

His assertions that pilots may have been 'experimenting' with VRS recovery, post the fanfares about Vuichard technique, may or may not be valid.

I have said frequently that believing Vuichard will get you out of full VRS is likely to give pilots false confidence - if that false confidence leads to pilots flirting with full VRS instead of just recovering at the incipient stage then Mr Vuichard and Tim Tucker have a lot to answer for.

If you know what country a guy is from, you'll know what he means by SWP.

I know what he means by SWP and it is the wrong terminology - even the FAA have caught up now.

Its not "the wrong terminology" its just different cultures using the same words to describe different things.

,...and the FAA hasn't "caught up" they just gave up and removed the term SWP from the books. That thing you and Canada call SWP is still too ridiculous to be in our books. In the US (officially) the term SWP doesn't mean anything anymore.

Page 11-9Vortex Ring State

https://www.faa.gov/sites/faa.gov/fi...k/hfh_ch11.pdf

Yes, I know the description mentions it. My point is that SWP has been removed from both the glossary and the indext (as well as in the Robby POH). Thus it no longer has a definition in our FAA book. Just a small blip of what it used to mean.

More importantly, there is nothing in our FAA book that says;
Settling With Power - A condition where the pilot comes in hot, waits too long to apply the brakes, then crashed as a result.

No because that's not where settling with power generally causes crashes.

When you have barely enough power to achieve and maintain a steady OGE hover and then try to make very steep approaches into confined areas - for example - then you try to arrest the rate of descent, reach your maximum power available and keep going down with the RRPM decreasing (overpitching) - THAT is settling with power

Or manoeuvring in and around an OGE hover, losing ETL due to wind change or using excessive power pedal to counter crosswind for example - any scenario where you run out of power and keep pulling to try and stop the descent, drooping the Nr and hitting the ground - THAT is settling with power.

The main difference between VRS and SWP is that VRS is an aerodynamic condition whilst SWP is a performance (or lack of it) condition - the result is often the same but the cause is different.

If the FAA can't understand that then something is wrong with their system.

I have never understood why you insist on calling situations where you "run out of power" (like overpitching and being too heavy to HOGE without a headwind) Settling "with" Power? So, I'm guessing THAT'S why the FAA isn't adopting YOUR use of the term, because it doesn't make sense to them either.

Nor do I understand why YOU have to be right and THEY have to be wrong. Just like how Canada put it in their texbook that we are wrong. Such arrogance! Its just a frickin' term. Why are you so attached to it?

To prevent a much longer debate here....perhaps a bit of ancient history being introduced might help.

A quick read of this thread done in the past right here at Rotorheads might produce a way to better frame the two competing views.

Of interest is one post made by Nick Lappos who is a very astute individual when it comes to such issues.

https://www.pprune.org/rotorheads/11...-merged-6.html


Nick is not here to discuss the following post but it is just one of many he has contributed during other discussions of VRS and SWP.

For what it is worth....I agree with both Crab and Nick for an array of reasons.

There most certainly is a difference between SWP and VRS. and to say otherwise fails to fully consider all of the factors that affect each....and both.

I recall Nick saying in one of his posts that in some modern helicopters there is enough power in the Rotor Systems to simply climb out of VRS....although for sure I am oversimplifying what he had to say about that.




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Robbie, just as a hint for the future. Crab has a huge knowledge, but also is a bit old and hard headed by now. Use the old geezers knowledge, but don't argue. Think a bit in terms of a retirement home where you try to get information from your great grandfather, where he hid all the money and jewellery.
If he does not agree with you, he will argue until the cows come home. Therefore, let it go.
Never forget, he was formed by the British military and therefore a flying god (now retired).
AFAIK, there is now no national aviation authority anymore that uses the term SWP at all. From a "do not confuse" point of view, it is better, just to let it die. End of story.
Regarding the Canadians, it's either a dig towards the US or they wanted to make a point for pilots coming from the US to fly there. Makes sense, if you have some godlike pilots from the US who argue until the cows come home (Actually, you find them in every country). Make a point in the regs and you save a lot of Canadian FI's nerves.

so what would you call it then? You are descending at a low forward speed or even straight down but at maximum available power with the RRPM gently decaying - you have the descent (which you can't arrest) so you are settling and you have max power - seems straightforward to me.

Sasless - yes I remember Nick saying it was possible to power out of VRS but you needed a huge amount of power to overcome the rotor drag caused by the vortices. :ok:

Rotorbee - I may have retired but I am still flying, helicopters and FW.

Understanding SWP is even more important than VRS since light helicopters are often operated with minimal excess of power beyond OGE and are also flown by less experienced pilots in the main - that spells accidents to an old dinosaur like me.

One of the first things I was demonstrated on my R22 type rating back in 92 was overpitching and how to recover from it.

If I were on a descent at max available power and the RRPM was decaying, I'd say I am clearly too heavy to HOGE and am overpitching.

Rotorbee,

Just like your Grand Dad in the Old Fart's Home....do remember he got Old for a reason....especially if he was a Helicopter Pilot.

As to the FAA being the All Knowing God....that kind of thinking might prevent you from ever being that Grand Dad in the Home.

They certified a lot of Jet Rangers and later had to coin the concept of LTE as a result of the poor Tail Rotor Design....they also certified helicopters without crashworthy fuel tanks....and have issued rules and regulations that allow people to go out and kill themselves.

You did read Mr. Lappos' post I quoted....the part where he mentioned all those different experts?

Perhaps you might be a bit more kind in some of your comments as if you live long enough you may have reason to regret making them.

I have had many an argument with Crab down through the years...but have always considered his experience and knowledge to be a real asset.

This Forum is a virtual Crew Room in my view....and my experience has been a lot of learning goes on over Tea when Pilots discuss their stock and trade as much of it is art and not science....although science plays a large role. The Art is the Pilot learning to apply that science and be able to discern when and how said science is about to do him in.

Trust me....you are not young enough to make all the mistakes yourself and survive....best you learn from others....and I always tried to learn from everyone I flew with no matter their experience or license level. Sometimes it might simply be to never do what they did....usually it was a well appreciated tip or trick that worked.

Now you have angels dancing on the head of a pin...........

... and that's why I am really fond of your knowledge Crab. No, really. Still going strong.:ok:

I mean, it is obvious, if we keep the term SWP, the confusion will continue. Overpitching is a good term to replace it.
Isn't it ironic, that SWP/Overpitching/etc. kills way more people than VRS and we are killing a perfectly good description. Still, it's OK with me.
The paper with the graph of the blade flapping is at least for me an eye opener. I will never ever demonstrate - or trying and failing - to get deeper into VRS anymore. Incipient is good enough and no flying sideways.
Should the investigation really show, that there are now several training accidents with VRS, boy I would not want to be in Vuichard's shoes.

Because it isn't VRS but has been wrongly used to describe VRS by those who can't see the difference.

You know there is a difference so why are you so hung up on using a perfectly reasonable term to differentiate VRS conditions from SWP conditions?

Let’s agree to call it SWB (Settling Without Power)

,... because it isn't a reasonable term to describe it. You are crashing because you were simply too heavy for max power to stop your rate of descent (or in Canada because you waited too long to apply the brakes) not because of some mythical gremlin you want to call Settling with Power.

SWP (the way you use the term) just seems like a cop-out for pilots to blane external forces for why they crashed,...kinda like LTE. "Gee it wasn't my fault your expensive aircraft crashed, it was SWP."

Take responsibility for why YOU crashed their aircraft. "Sorry boss, but I was just too heavy to come in like that".

By your logic we should do away with VRS as a term as well then - it's far more of a mythical gremlin than SWP.

If that's the road you choose to follow, then knock yourself out.

Years ago while getting my license, I listened carefully to the instructor trying to explain VRS and SWP. It seemed then, and still does, that SWP should just be amended to SWEP, and stand for "settling without enough power". No spooky and weird response to any of the control inputs. I just tried to pull pitch to stop a descent and even though more pitch helped, as I kept pulling I ran out of power and thus rpm.

The few times I tried VRS with the instructor in a 44 were plenty, and did convince me never to get there. We were in a different state, the controls didn't work, and more pitch DID NOT HELP up and until and past where I ran out of power. I like vertical ring STATE because it is like you and the machine are in some strange and bad place where controls don't work.

VRS= more pitch doesn't help
SWEP= more pitch helps until you run out of power.

That seems simple to me.

So just to be clear - I don't care what you call SWP Robbiee - all I care about is that pilots know there is a difference between VRS and running out of power in an OGE hover.

If this whole discussion serves to highlight that difference then it was worth me banging my head against a brick wall for so many posts.

SWP/SWEP/overpitching/or whatever, causes far more accidents - as rotorbee points out - yet the reason for those accidents has often been attributed to VRS because the FAA were confusing the terminology.

That leads to pilots confusion which is always a bad thing especially if something as important as good pre-flight planning and power awareness is ignored because of that confusion.

gator2 - I agree, keep it simple. I thought it was simple since I clearly understood the difference between the two situations but I appear to be in a minority.

Crab, please leave the brick walls alone, they haven't done anything to you.
Just to make one thing clear, the NTSB does accident investigations, the FAA doesn't. Since I tried to find those thousands of VRS accidents, I can claim, that the NTSB knows the difference between VRS and running out of power. They used the term SWP "correctly" only for VRS accidents. There are apparently only 3 in the NTSB database, since 2000 to 2015. When somebody runs out of power, it is stated as such. Just not as SWP. And there are many. About 30% of the accidents have not enough power as a factor. The whole world talks about VRS, only the US have the SWP confusion. The FAA decided correctly to not use the term SWP anymore. They fixed an old thing that started in the Navy. I don't see any reason to keep SWP as a term. It would cause just more confusion in the future, therefore SWP has to go and should under no circumstances used for something else.
I don't think that any accident investigation agency uses the term SWP for running out of power. Today, old US-pilots think in terms of VRS, when they hear SWP, younger ones talk more often about VRS, not all though, because the old still teach SWP. To change the use of the term, is much more difficult and confusing, than just dropping it. Let it die in peace.

Fear not, I have known the difference since 2003 when I passed my PPL checkride.