Vortex Ring / Settling with power (Merged)

[NickLappos]

Helisphere,
Good thoughts, I really agree that the updraft could make things worse. Maybe not VRS, because SWP is strongly influenced by descents. I think you might be on to something.

FAA does VRS testing - no, not required, maybe not necessary.

KMax? Great question! Different flow patterns might yield different/no VRS.

BTW nice excel spread sheet, good work!

[helisphere]

Well the spreadsheet certainly makes you think... I wouldn't have thought to make it if I wasn't reading through this thread.

A little background, I've got about 4000 hours and about 700 longline mostly in BHT205/210, AS350 and 369/500. In any type of normal flying I have never had any issues with VRS. But longlining in mountainous terrain has definitely givin me a few thoughful moments. I think with that experience I have a pretty good feel/sense for when it's an issue and I have to agree that I don't think it's near as big an issue as many instructors teach, and yes SWP without VRS is a more common problem. But I have to say that mountain longlining really makes me fly more respectfully regarding VRS or SWP than when I'm doing any other type of mission.

[helisphere]

Nick, I have a question for you. When you are taking data with an instrumented aircraft specifically on VRS, does the aircraft have angle of attack or vertical airspeed (besides VSI/ASI) instruments? And what parameters do you then look at and analyze from the data?

I think it would be cool to instrument a logging helicopter at work. Might scare you manufacturing types though, I mean for the stresses your strain guages would record, I know it scares me. I don't know, maybe it's already been done but for airflow data and to see if they are getting closer to VRS than one might think.

[pcpahari_IAF]

Finally... I got it....

copy text from wherever, paste same on your reply, highlight again, click on the icon, it comes up with the word quote in brackets before and after, don't worry, just tab down, say the rest of your message.
magic.
cheers mate I had to ask heliport how to not so long ago.

.... GOTCHA.... aint' I ???

Thankyou MightyGEM

[MightyGem]

That's ok. Errrr....thanks for what?

[Boslandew]

Vortex Ring

Going back to the original question, I heard about a chap in Aden back in the 70's who thought his rotary experience should include VR and recovery. He apparently put a Scout into VR at 10000' and finally came out of it, a very chastened aviator, somewhere below 2000'

[jimf671]

You Tube

You Tube

You Tube

[[email protected]]

So many half-truths in those Jim - at least Transport Canada highlights there is a difference between VRS and SWP, even if that guy doesn't understand it doesn't have to be a vertical descent for VRS, just a steep one.

The Vuichard video shows recovery action taken immediately which is really an incipient VRS condition as he never lets it develop. If he did, his technique wouldn't work any better than the standard recovery. Going sideways out of the dirty air or going forwards - the rotor doesn't know which way it is going - clean air is clean air.

[SLFMS]

I enjoyed the first video and found it refreshing for someone to differentiate SWP and VRS but he lost me when he started talking about the tips stalling during VRS.
My understanding is it's the centre of the disk that stalls and propergates outward whereas the tips are at very low angles of attacks due to blade washout and increased tip vorticies increasing induced airflow as well as the amount of the blade tips exposed to it.
Perhaps I'm hopelessly wrong but its logical to me and explained well in Wagtendonk.

[pilotmike]

Originally Posted by [email protected]

The Vuichard video shows recovery action taken immediately which is really an incipient VRS condition as he never lets it develop. If he did, his technique wouldn't work any better than the standard recovery. Going sideways out of the dirty air or going forwards - the rotor doesn't know which way it is going - clean air is clean air.

... except for use of pedal which is a required ingredient of the technique, which makes a difference to whether you are poling forwards or sideways with the cyclic. Probably that's why the technique is careful to specify WHICH pedal is to be used, with opposing cyclic.

[[email protected]]

except for use of pedal which is a required ingredient of the technique, which makes a difference to whether you are poling forwards or sideways with the cyclic. Probably that's why the technique is careful to specify WHICH pedal is to be used, with opposing cyclic.

That just induces a sideslip which doesn't get you into clear air any sooner than just applying forward cyclic.

Note also that he grabs a handful of power which, in developed VRS would aggravate the condition but, since he only ever does it in the incipient stage, just powers out of the IVRS condition.

Exactly the same result would be achieved if you just pulled power at the incipient stage without any of the sideslip

[pilotmike]

Originally Posted by [email protected]

That just induces a sideslip which doesn't get you into clear air any sooner than just applying forward cyclic....
Exactly the same result would be achieved if you just pulled power at the incipient stage without any of the sideslip

Though I'd have to defer to your doubtless greater knowledge and experience, I believe that the pedal opposing the cyclic allows the additional translating force of the tail rotor to assist with moving out of the VRS sideways, whereas forward cyclic alone has no such benefit, and would rely solely on the result of cyclic, ie. main rotor vectored thrust only.

As for sideslip. I'm not sure I understand your point, as that would only apply in flight with significant forward (air)speed, whereas in this case, by definition, there's negligible horizontal speed. So it seems the technique is designed to use every means possible in order to translate out of the VRS ASAP, which undoubtedly is swifter with the assistance of the tail rotor thrust.

But I'll be happy to be corrected if I've missed something obvious in your reasoning.

[[email protected]]

Though I'd have to defer to your doubtless greater knowledge and experience, I believe that the pedal opposing the cyclic allows the additional translating force of the tail rotor to assist with moving out of the VRS sideways, whereas forward cyclic alone has no such benefit, and would rely solely on the result of cyclic, ie. main rotor vectored thrust only.

Which control do you use to fly the helicopter in pretty much any direction? The cyclic - it has far more authority than the TR.

If the IAS is so low then full pedal will create yaw but not much else - the main movement will always come from the cyclic input.

Far more experienced people than me dismiss the Vuichard technique as window-dressing for IVRS recovery which can be achieved just by raising the lever.

[pilotmike]

Originally Posted by [email protected]

Which control do you use to fly the helicopter in pretty much any direction? The cyclic - it has far more authority than the TR..

Far more authority, yes. However the tail rotor can still add some more. This isn't an either / or call, it is all about adding more. Even if the TR can only add 10% more, that's a whole lot better than 0% more.

Did you ever turn down a 10% pay rise on the basis that you already earned far more than the pay rise being offered?

Originally Posted by [email protected]

If the IAS is so low then full pedal will create yaw but not much else - the main movement will always come from the cyclic input..

The TR is the sole cause of translating tendency. Yes, it is INTENDED for yaw, but without question, it causes translation too. Are we saying the cyclic alone is so very powerful by itself that there is no need for any further assistance from wherever that help might come? If that was true, we wouldn't even be discussing escaping VRS ASAP with minimum height loss as by definition, the only time nil further assistance is required is when we can already do it with zero height loss using cyclic alone. That clearly isn't the case.

Originally Posted by [email protected]

Far more experienced people than me dismiss the Vuichard technique as window-dressing for IVRS recovery which can be achieved just by raising the lever.

I didn't even consider that to be a possibility!

[[email protected]]

How much angle of bank do you use in the hover to compensate for TR Drift/translating tendency? 2, 3, 4 degrees? Maybe 5 max in some aircraft - so a very small amount of cyclic easily overcomes the TR power - I think you are greatly over-egging the effect of the yaw - if you want more lateral movement just use more bank.

Back to the standard recovery of pushing the cyclic forward - you are far more aerodynamic moving forward since that is the way the aircraft is designed to fly, unlike trying to drag it sideways with opposing cyclic and pedal.

My point about the use of collective to power out of IVRS is that with enough power available you can do exactly that so why mess about with the roll and yaw. The problem is that not rasing it to max immediatley runs the severe rsik of aggravating the condition and putting you into VRS proper. You could also just take yourself into overpitching and Nr decay

If Vuichard can produce a video where he can go past the stage he normally recovers by just raising the lever enough to worsen the stall and enter fully developed VRS and then recover from full VRS using his technique in 50', I for one will be gobsmacked but I doubt it will happen.

He also needs to demonstrate his technique on bigger and heavier aircraft for it to be valid.

[pilotmike]

Originally Posted by [email protected]

Far more experienced people than me

That was the bit I dismissed as being beyond the bounds of possibility....!
Returning to the technical discussion, you haven't taken on board my points, and you have argued against things which I have NOT said - I was not saying yaw had any particular purpose in this, nor was I advocating yaw for yaw's sake, if you read what I actually said. My point was in favour of adding the translating effect of TR in ADDITION to cyclic, which can only help the cause. However, your mind appears made up and closed to other ideas, therefore further discussion appears pointless, unfortunately.

[[email protected]]

Mike you misunderstand my point - why use a combination of yaw and lateral cyclic when simple forward cyclic will do the job just as well if not better?

People have got hung up on the 'magic' of this technique and, to be fair, it has been sold well with the glossy videos. If he just used the same amount of power and pushed the cyclic forward instead of laterally, he would fly out just as easily because it is IVRS and not VRS.

People can believe what they want but my concern over the publicity this 'technique' has gained, is that people might really think they can mishandle the aircraft sufficiently to get into VRS in the misguided belief that the Vuichard technique will guarantee recovery in 50'.

Just avoid the conditions in the first place.

[Vertical Freedom]

Originally Posted by [email protected]

Mike you misunderstand my point - why use a combination of yaw and lateral cyclic when simple forward cyclic will do the job just as well if not better?

People have got hung up on the 'magic' of this technique and, to be fair, it has been sold well with the glossy videos. If he just used the same amount of power and pushed the cyclic forward instead of laterally, he would fly out just as easily because it is IVRS and not VRS.

People can believe what they want but my concern over the publicity this 'technique' has gained, is that people might really think they can mishandle the aircraft sufficiently to get into VRS in the misguided belief that the Vuichard technique will guarantee recovery in 50'.

Just avoid the conditions in the first place.

You're bang on Crab....I've pushed the envelope on VRS many times (training) in the 350, 125, 130, 206, 407 & G2; & I can tell ya once Your fully established in full blown VRS the Vuichard technique does diddly squat, absolutely nuttin, the machine continues accelerating like a greased anvil towards Mother Earth. Sure it works ok (just) in IVRS, but only for very mild IVRS as the demo vid shows! But, nothing works as well as poling forward which is the way the machine is designed to go (not side-ways).....it's no surprise then how the Robinson company is now pushing this flawed technique as the new saviour for VRS?

As You stated Mate; VRS is best avoided with good airmanship, unless deliberate for the purpose of training.

Happy landings

[SASless]

We can move two controls simultaneously can we not?

Key is to do something....and that which best resolves the problem.

It might just be you need to turn to gain an advantage afforded by terrain....so let's not get locked into exactly one response can we?

[[email protected]]

VF -

Sasless - getting locked into exactly one response is exactly what Vuichard is selling. I agree that there needs to be flexibility but based around good techniques.