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New Vortex Ring State Recovery Technique

wink

VS NFO. Blue and Gold Officer
None
Super Moderator
Contributor
So, I ran this by the Army guys that fly the Cobra in my AAHF chapter. I got some very good comments (at least I thought so as a non helo guy). The best came from the retired CW5 NTPS trained Army and Boeing Helicopters test pilot who is familiar and performed it. WRT training and overall knowledge of this technique, one of our crew chiefs is a former Army mech who is working as a helicopter A&P and building helo time while he puts together a WO pilot app to go back in. He learned this technique from in a small flight school flying Schweiser 296's and demoed it in the 296 to one of our very high time Army pilots who hadn't seen it. So it is out there. Retired Boeing test pilot comments excerpted below.

There are a couple of errors in the article but none that would impact the effectiveness of the technique, however, I do not agree that one would be measurably better then the other. The reason is simple, the amount of side wards thrust imparted by the tail rotor during the maneuver is minimal in light helicopters and is the only difference between flying out of the condition forwards or sideways. That, plus the fact that the attitude of the aircraft is not taken into account when the onset begins would skew the data. Assuming that the aircraft is fairly level at onset there should be very little difference. If however the nose is 20 degrees nose high then the lateral move would be quicker then lowering the nose and flying out of it with forward airspeed.

Regarding the applicability of the technique to tandem rotor aircraft.

It is common in a Tandem to have one rotor enter Vortex Ring State before the other. That is exactly what happened in the fatal Marana accident several years ago. Roll or pitch control in a Tandem is achieved through dissimilar thrust application of the rotors. In a Chinook forward pitch is achieved through increasing thrust in the rear rotor and decreasing it in the front. In the Osprey roll is done the same way. Right roll would be achieved by increasing thrust in the left rotor and decreasing thrust in the right. In the Marana accident the right rotor got into Vortex Ring State so the aircraft began a right roll. The pilot used the technique described in the article and applied additional power and left cyclic to stop the roll. Which increased the thrust on the right rotor and decreased it on the left. This put the aircraft deeper into Vortex Ring State, without any of the desired lateral translation. The aircraft went deeper into Vortex Ring State, rolled inverted and impacted.

I have always found this fascinating. As a non helo rated "copilot" in law enforcement I tried to make myself familiar with all the unique ways a helicopter can kill you so I could actually BE a copilot and recognize impending stupidity or carelessness. The flight profiles in LE flying could lend themselves to vortex ring state, so I have tried to educate myself on the issue. I am smarter now then I was several hours ago.
 

SynixMan

Staff Life
pilot
Contributor
No mentions of applicability in something bigger than a Robbie. Call me a bit of skeptic.

Also what does this gain you that accelerating forward doesn't? You already dorked up the approach and got into VRS. Go around and try again.
 

wink

VS NFO. Blue and Gold Officer
None
Super Moderator
Contributor
No mentions of applicability in something bigger than a Robbie. Call me a bit of skeptic.

Also what does this gain you that accelerating forward doesn't? You already dorked up the approach and got into VRS. Go around and try again.
Not intended as a challenge, because I don't have the rotary chops, but an honest effort to learn, I think you have the Robinson reference backward. My test pilot buddy indicates the technique is limited in a light civ helo because you don't get enough excess power from the tail rotor. Leads me to believe it might be more effective in a more powerful aircraft. Although the author of the article mentions it being demoed to him in a Robbie, the namesake of the technique was flying long line in the Alps. Certainly not in a R44.

Now here is your chance to truly edumacate me. Most all my left seat time has been in an OH-58, and I have never seen vortex ring state demoed. It is clear from the article that the benefit to the technique in question is less altitude lost in recovery. So, how much altitude do you usually lose recovering in traditional forward acceleration recovery in a -60? If you can minimize altitude loss in recovery, then isn't that a good reason to have this technique in the tool box? Then there is the case where accelerating forward may not be an option. Although I don't recall if VRS was a factor in this mishap, I am left thinking in a similar circumstance, and alternative to forward acceleration may be a good option.
 

SynixMan

Staff Life
pilot
Contributor
Maybe it could work in something different than a Robbie, I don't know. The little I've heard about them has indicated their rotor system is different than the Bell/Sikorsky stuff I've flown and more temperamental. All anecdotal.

The video you posted I've seen before. My understanding is the got into a mountain downdraft which can get crazy high fpm rates. They pulled the guts out to not hit the mountain, then drooped the rotor (power required exceeds power available, which is very doable for 60s at altitude), spun, crashed.

VRS is a different aerodynamic phenomenon (paging TPS nerds) where you're settling into your own down wash by getting high sink rates at low speeds (think very steep approach to a spot). You recover by reducing power, nosing over for airspeed, get out of your down wash, and wave off. *Maybe* you could make another play to land on that pass but you'd have missed your original spot and not accounted for the shit in your pants after sorta almost crashing.

Full disclosure, never had it happen to me, but we preach avoiding the entry parameters and what to do recovery technique to everyone from day one in the 60.
 

Jim123

DD-214 in hand and I'm gonna party like it's 1998
pilot
VRS is like Sylvester the cartoon cat trying to row a boat up a waterfall. The harder he rows, the more screwed he is.
 

Pags

Pope of Chili Town
pilot
Not intended as a challenge, because I don't have the rotary chops, but an honest effort to learn, I think you have the Robinson reference backward. My test pilot buddy indicates the technique is limited in a light civ helo because you don't get enough excess power from the tail rotor. Leads me to believe it might be more effective in a more powerful aircraft. Although the author of the article mentions it being demoed to him in a Robbie, the namesake of the technique was flying long line in the Alps. Certainly not in a R44.

Now here is your chance to truly edumacate me. Most all my left seat time has been in an OH-58, and I have never seen vortex ring state demoed. It is clear from the article that the benefit to the technique in question is less altitude lost in recovery. So, how much altitude do you usually lose recovering in traditional forward acceleration recovery in a -60? If you can minimize altitude loss in recovery, then isn't that a good reason to have this technique in the tool box? Then there is the case where accelerating forward may not be an option. Although I don't recall if VRS was a factor in this mishap, I am left thinking in a similar circumstance, and alternative to forward acceleration may be a good option.
We discussed the mishap in the video at ASO school. If I remember correctly they lost tail rotor effectiveness authority due to limited power at high altitude. This resulted in them starting to spin. Pulling power exacerbated the condition causing them to droop further, spin more, and impact the mountain.

I'm not too familiar with many instances of VRS in H-60s other than the loss of the super secret H-60 during the Bin Laden raid.
 

Randy Daytona

Cold War Relic
pilot
Super Moderator
If I remember correctly, intentional vortex ring state was a prohibited maneuver in the training command and perhaps in the grey aircraft as well. Conversely in the civilian world it seems to be a mandatory item to be checked off on every checkride. I especially remember doing them in South Africa in the Puma - the bottom would fall out at over 3000 FPM. (make sure you give yourself a lot of altitude). Hoping to get some feedback from test pilots - anything that can give us a fighting chance down low would be a great improvement. As Wink alluded to, if you get into it down low - there is nowhere to go. You really have no altitude to trade to lower the collective and get clean air into the rotor to fly out.
 

phrogdriver

More humble than you would understand
pilot
Super Moderator
The sideways cyclic seems to be the key component.

The problem with the conventional technique is that forward cyclic and lower collective is not an optimum solution, since you're probably in the landing environment anyway, since you were slow and vertical to avoid obstacles in the first place. Less altitude loss is a good thing. Of course, if that doesn't work either, now you crash with sideward drift and probably rolled it over.

PS The Marana V-22 didn't really crash due to VRS, IMHO.
 

ChuckM

Well-Known Member
pilot
This article surfaced at the HSM FRS about two years ago.

The consensus was that the maneuver was conceivable in a -60, though since it's not what NATOPS puts out, most of us just squirilled it away for our own pilot tool kit and went on teaching the vetted procedure. At most it was a discussion point with CAT II and III types.
 

wink

VS NFO. Blue and Gold Officer
None
Super Moderator
Contributor
...
PS The Marana V-22 didn't really crash due to VRS, IMHO.
Well, OK. You have more insight then the rest of us and I don't need you to talk about stuff you may not want to. But, again, so as to learn, couldn't a V-22 get one rotor in VRS not unlike a phrog or -47, causing roll instead of a tandem rotor pitch up? And the net result might be a mishap similar to Marana?
 

phrogdriver

More humble than you would understand
pilot
Super Moderator
Well, OK. You have more insight then the rest of us and I don't need you to talk about stuff you may not want to. But, again, so as to learn, couldn't a V-22 get one rotor in VRS not unlike a phrog or -47, causing roll instead of a tandem rotor pitch up? And the net result might be a mishap similar to Marana?
It could, but the V-22 is far more resistant to VRS than traditional rotorcraft. It takes well over 2000fpm to induce it.

Due to my own personal experience and having talked to some of the original DT crew, I believe the mishap was due to saturation of the fly-by-wire system's control authority due to flying into the -1 aircraft's wake.

I nearly bought it in a very similar manner to Marana (recovered from a 67-deg uncommanded roll at 47') The NATOPS formation checkpoints have since been revised. I'll take my small share of the credit for that change. Sometime NATOPS is just written in almost-blood.
 

HokiePilot

Well-Known Member
pilot
Contributor
It could, but the V-22 is far more resistant to VRS than traditional rotorcraft. It takes well over 2000fpm to induce it.

Due to my own personal experience and having talked to some of the original DT crew, I believe the mishap was due to saturation of the fly-by-wire system's control authority due to flying into the -1 aircraft's wake.

I nearly bought it in a very similar manner to Marana (recovered from a 67-deg uncommanded roll at 47') The NATOPS formation checkpoints have since been revised. I'll take my small share of the credit for that change. Sometime NATOPS is just written in almost-blood.
I remember talking about that in ASO school. It seem that a cross under in helicopter mode is a huge no-no in the Osprey.
 
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