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The vortex trap


Rongor

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Let me repeat myself:

 

After about 30 descents from hover, with various mid-level loads I find out that the VRS threshold is around -1200fpm in the version we have. Any vertical descent slower than that can be easily arrested by pulling collective (provided we have the power, if we don't then we deal with settling with power). But once we go near or cross the -1200fpm, the helicopter fall through, and pulling the collective won't change the situation... although I didn't notice for it to aggravate it either.

 

Now the question is: does the -1200fpm right or not? When we look at what Nick Lappos wrote about the VRS, as the vertical speed of descent being equal to rotor downwash, and therefore dependent on the disc load, we can deduct, that ~25kg/m^2 rotor of Huey will have that speed 1.8 times greater than that of 14kg/m^2 rotor of Robinson R22. Now, thanks to the magic of internet we know that R22 enters VRS at about 700-800fpm at gross weight. So taking the averages we get around -1230fpm with Huey at 8500lb load... so I'll say we're pretty darn close.

 

So I'm surprised that people are still having problems with VRS... therefore I have to ask two questions:

1. How do you fly ?

2. Are you absolutely sure it's VRS ? Or maybe flying heavy and you simply running out of space because of the enormous power required to perform what you're trying to do ? - meaning you're settling with power, and not experiencing vortex ring state.

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Not sure how to answer the question "How do I fly?" but here goes...

When flying the HUEY with no load and nothing special... I make my approach at around 80 knots.. I slowly drop the collective.. (And I MEAN slowly ) and I watch to make sure the descent is around 100 feet per minute... (this is really hard to keep consistent and requires really tiny adjustments withe the collective..) Anyway, as I descend I start to pull the cyclic back with the intent of keeping the diamond where it was during takeoff.. As the nose comes up slightly, I push the collective SLIGHTLY down so the helicopter doesn't shoot straight up due to the pulling back of the cyclic. As the speed drops, my descent is constant around 100 feet per minutes until I reach almost zero knots.. At this point it drops like a rock and I have tried pulling a lot of collective. No dice. the only thing I can do is the standard response for VRS which is slightly reduce collective and move in any direction to get out of VRS and once the rotor starts to bite once again then apply collective.. My issue is that lately this happens to me so close to the ground I don't have enough time (altitude) to complete the maneuver and auger into the ground.

 

To me this seems to be VRS.. and I have read a lot of books and very few of them agree about VRS vs. settling with power etc.. Whatever the issue and whatever you wish to call it, I feel that there is still an issue with the sim .. Now the only thing I can compare to is my very limited experience flying a Robinson R22... I am no exeprt but I can say that I have only ever experienced VRS (or whatever the issue is that I am experiencing in this sim) in a Robinson when I was TRYING to. At a safe altitude... and once again everything I have read and heard is that the Huey is more difficult to get to this state than a Robinson is...

"Pride is a poor substitute for intelligence."

RAMBO

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....meaning you're settling with power, and not experiencing vortex ring state.

 

......and I have read a lot of books and very few of them agree about VRS vs. settling with power etc.....

 

The US Army says as follows:

 

SECTION VIII – EMERGENCIES

 

SETTLING WITH POWER

 

1-192. Settling with power (figures 1-73 through 1-75 ) is a condition of powered flight in which the helicopter settles in its own downwash. This condition may also be referred to as vortex ring state....

 

Excerpt from manual:

 

FM 3-04 SWP.pdf


Edited by 159th_Viper

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Let me repeat myself:

 

 

 

So I'm surprised that people are still having problems with VRS... therefore I have to ask two questions:

1. How do you fly ?

2. Are you absolutely sure it's VRS ? Or maybe flying heavy and you simply running out of space because of the enormous power required to perform what you're trying to do ? - meaning you're settling with power, and not experiencing vortex ring state.

 

Totally agree it happens in real life it will happen in the game, it might be a pain but real pilots have to deal with it so will you unless you go for game mode.

 

IMO the current flight model is very hard to get in to the VRS opposed to what it was like at the release of the beta unless you've flown the Huey in real life its hard to call out the current VRS in the flight model without that knowledge unless something is totally wrong.


Edited by TimeKilla
Added more info.

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Totally agree it happens in real life it will happen in the game, it might be a pain but real pilots have to deal with it so will you unless you go for game mode.

 

IMO the current flight model is very hard to get in to the VRS opposed to what it was like at the release of the beta unless you've flown the Huey in real life its hard to call out the current VRS in the flight model without that knowledge unless something is totally wrong.

 

Did you even read my previous post?

??

"Pride is a poor substitute for intelligence."

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Yeah I've also heard someone say its meant to be hard to get into VRS in the Huey but unless you've flown it that's the problem not getting at you directly.

 

I am not sure what that means... ??

If I am understanding what you are saying is that since I haven't actually flown the Huey how would I know whether it is "Difficult" to reach VRS or not... I think that is what you are saying..

 

I CAN say that I have flown an R22 and it is MUCH more difficult to reach VRS in a Robbie in real life...

 

My point is that the Huey is stated as being more difficult to get into VRS than an R22 and I can tell you from experience that this sim is 100 times EASIER to hit VRS than a real R22 is so that means that the SIM is not totally accurate.

 

And I am not picking on Belsimtek, I think this module is awesome, but I still feel the flight model in reference specifically to VRS needs to be tweaked further...

"Pride is a poor substitute for intelligence."

RAMBO

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Np fair points. :thumbup:

 

From what I've heard it was hard to get into VRS in real life. Suppose what I mean is they can only take what real pilots say as the flight model is getting very close now to what it should be in other respects IMO its getting harder for people to just call it out unless there's figures Belsimtek/testers can look at to confirm the issue.

 

Scrap the real pilot thing, If we can find figures that show that the flight model out it's easy to confirm and fix.

 

Sundowner.pl, Pointed out a'lot of stuff he found that's being fixed as-well.


Edited by TimeKilla
I confused my point and mislead.

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The US Army says as follows...
Funny that I'm saying this, but the manual is wrong :smartass:

 

Like I wrote in the other topic, there are two approaches to those phenomena:

1. Putting all the cats into one bag - so according to those VRS is Settling With Power, and vice versa - this what this manual is doing (either dumbing down so a young pilot can understand, or is simply copying the manuals from 1950s, that simply didn't know better);

2. Settling with power is a state of high rate descent that can be arrested by applying enough power, and VRS is going through its own downwash, where applying more power only makes things worse.

 

The best I can do is direct you to PPRuNe forum where you will find gentlemen like Nick Lappos, and Shawn Coyle, who actually wrote books on those phenomena, and spend a lot of their career to study them in practice.

 

Now, outlawal2, if what you write is what's going on to you, then my response is simple: this can't happen. I have never experienced sudden increase in descent in steady deceleration, that couldn't be arrested before going through the VRS threshold (with light helicopter it will be around -1000fpm). It appears you're omitting something, can you please provide a track of such behavior ?

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Agree 100% with Outlawal2 , I fly the KA-50, no VRS ever. Fly the Huey: VRS Every time

 

Is the KA-50 reputed to have almost no VRS ?

Is the Huey reputed to be much worse than the Kamov ?

 

To me there is no doubt that the VRS is too strong in UH-1H, I had never heard of VRS before the Huey.

 

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Funny that I'm saying this, but the manual is wrong :smartass:

 

Like I wrote in the other topic, there are two approaches to those phenomena:

1. Putting all the cats into one bag - so according to those VRS is Settling With Power, and vice versa - this what this manual is doing (either dumbing down so a young pilot can understand, or is simply copying the manuals from 1950s, that simply didn't know better);

2. Settling with power is a state of high rate descent that can be arrested by applying enough power, and VRS is going through its own downwash, where applying more power only makes things worse.

 

The best I can do is direct you to PPRuNe forum where you will find gentlemen like Nick Lappos, and Shawn Coyle, who actually wrote books on those phenomena, and spend a lot of their career to study them in practice.

 

Now, outlawal2, if what you write is what's going on to you, then my response is simple: this can't happen. I have never experienced sudden increase in descent in steady deceleration, that couldn't be arrested before going through the VRS threshold (with light helicopter it will be around -1000fpm). It appears you're omitting something, can you please provide a track of such behavior ?

 

Well I can't suply a track now as I am at work, but maybe I CAN explain what I am doing that may be causing this.. It is possible that I am not reacting quickly enough to the rapid descent and not applying enough collective to beat settling with power.. Then once it continues to drop it then reaches VRS and drops like a friggin rock.. I will definitely keep this in mind and see if I can fix these issues...

 

I will still say that even if that is true, I have never had this issue in the Robbie so i still think something is amiss... (but thanks for the clarificaton as it may be settling with power that then turns into VRS) Slight difference but very important when trying to figure out exactly what is happening!

"Pride is a poor substitute for intelligence."

RAMBO

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Agree 100% with Outlawal2 , I fly the KA-50, no VRS ever. Fly the Huey: VRS Every time

 

Is the KA-50 reputed to have almost no VRS ?

Is the Huey reputed to be much worse than the Kamov ?

 

To me there is no doubt that the VRS is too strong in UH-1H, I had never heard of VRS before the Huey.

 

Lou

 

The U.S. Department of Transportation has published a “Basic Helicopter Handbook”. One of the chapters in it is titled, “Some Hazards of Helicopter Flight'. Ten hazards have been listed to indicate what a typical single rotor helicopter has to deal with. The unique coaxial rotor design either reduces or completely eliminates these hazards. The following list indicates which:

 

Settling with power — Reduced

Retreating blade stall — Reduced

Medium frequency vibrations — Reduced

High frequency vibrations — None

Anti torque system failure in forward flight — Eliminated

Anti torque system failure while hovering — Eliminated

The reduction and elimination of these hazards are the strong points for the safety of coaxial rotor design

 

The KA-50 has a reduced VRS due to being coaxial rotor design but it can be done as I've had it a good few times.


Edited by TimeKilla
Forming better statements.

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Well I can't suply a track now as I am at work, but maybe I CAN explain what I am doing that may be causing this.. It is possible that I am not reacting quickly enough to the rapid descent and not applying enough collective to beat settling with power.. Then once it continues to drop it then reaches VRS and drops like a friggin rock.. I will definitely keep this in mind and see if I can fix these issues...
Few things we can try here:

 

- make sure you have the current DCS version, because the VRS in previous build was rather over-exaggerated and would result in what you're describing;

 

- practice deceleration in the city at rooftop level, without any descending, just keep the altitude steady;

 

- forget the controls position display, fly by what is required in current situation, not what was at take-off;

 

- be certain that everything you do is either in dead calm, or into the wind, never, EVER decelerate going downwind !

 

 

I will still say that even if that is true, I have never had this issue in the Robbie so i still think something is amiss... (but thanks for the clarificaton as it may be settling with power that then turns into VRS) Slight difference but very important when trying to figure out exactly what is happening!
It's a problem of lack of sensory input, in a real aircraft a change of few fpm is noticeable by feel, here you won't notice when the VVI goes from positive, to negative 2000 fpm, and the higher this happens it's harder to notice.

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Few things we can try here:

 

- make sure you have the current DCS version, because the VRS in previous build was rather over-exaggerated and would result in what you're describing;

 

- practice deceleration in the city at rooftop level, without any descending, just keep the altitude steady;

 

- forget the controls position display, fly by what is required in current situation, not what was at take-off;

 

- be certain that everything you do is either in dead calm, or into the wind, never, EVER decelerate going downwind !

 

 

It's a problem of lack of sensory input, in a real aircraft a change of few fpm is noticeable by feel, here you won't notice when the VVI goes from positive, to negative 2000 fpm, and the higher this happens it's harder to notice.

 

I will try all of the above when I get home this evening.. Thanks for working with me on this! :thumbup:

"Pride is a poor substitute for intelligence."

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No problem, I just find it strange that there are still problems even though the VRS was addressed in the last patch.

 

Maybe a piece of the problem is the perception of helicopter operations - you really shouldn't operate in the vertical much, any approach should terminate at the correct altitude you want to achieve when the airspeed gets to zero. Especially with the Huey.

 

For example if we would take the Apache, we have twice as high disc load, so we could do pop-ups and masking in the vertical up to 2000+ fpm in descent safely. What I like to do is to play in the city a cat and mouse game with Shilkas - but if I do a pop-up, I never return to hiding spot in hover, it's to slow to do it safely in vertical - I just brake off to the side and dash to another concealed spot.

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  • ED Team

I just want to add

 

when I fly the ka-50 it try's to kill me every time with VRS . . . .

 

...... But I don't have a problem with the HUEY :)

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I just want to add

 

when I fly the ka-50 it try's to kill me every time with VRS . . . .

 

...... But I don't have a problem with the HUEY :)

 

OK and that makes ZERO sense as far as my experiences go.. Shark is MUCH easier to fly than the Huey especially since I am dialing in my flying.. Due to the Huey being so much more difficult..

 

The only way that this makes sense is if what we are feeling and why it is so different must be because of hardware differences and individual setups for each module.. Otherwise this makes zero sense at all...

 

SUNDOWNER..

What hardware are you using for throttle, stick and rudder? And also, have you made any changes to the settings for these devices?

"Pride is a poor substitute for intelligence."

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remember that KA-50 and UH1 is different helicopters

personally i found the UH1 much more responsive

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I have found that I do much better with landings without using the Ctrl-ENTER Axis view graph. Not sure if this is much help, but it does tend to save me all the time since I tend to slow down much sooner than just throwing the force trim around at will and falling like a meteorite. :doh:

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SUNDOWNER..

What hardware are you using for throttle, stick and rudder? And also, have you made any changes to the settings for these devices?

Thrustmaster HOTAS Cougar for cyclic and collective, and Saitek Pro Flight Cessna rudder pedals.

 

The rudder is not modified, the Cougar on the other hand has ball bearings installed in both stick and throttle, and springs replaced with custom - much lighter ones (they only give feedback on where is the center position - won't center the stick by themselves). Electronics and sensors are stock, so are the arm lengths, although I do have plans on changing those too.

 

The devise settings are standard for axes: linear, no deadzone.

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I've found that the sim will enter vortex ring/settling with power much more easily since the last update - any chance of going back to the last flight model?

 

Normal approaches to hover in ground effect are now very tricky indeed. I did a test last night and found the only safe way to get on the ground is to arrive at a tall reference feature like a block of flats at 100' agl in the hover and then descend VERY slowly to the surface.

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remember that KA-50 and UH1 is different helicopters

personally i found the UH1 much more responsive

 

Ditto same here.

 

I also found the shark easy to get into VRS at times, I think people are forgetting slightly they are different helicopters ones a attack helicopter with a coaxial design and ones a utility/light support helicopter so why are we comparing them I do not know.


Edited by TimeKilla

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I have no problems with this now and think it should left how it is, it is by all accounts so easy once its clicked in your brain and landings now are right on the money troop deployments for me are milli seconds of time I just wish they could deploy from a low hover.

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I agree it's nice to master a challenging FM but I just can't reconcile the aggressive VRS implementation the current FM has with real world heli pilots comments about VRS not really being an issue and easy to deal with.

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VRS = WIP.

 

just don't remove it altogether, Please!!!!

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