Split: Vortex Ring Recovery

[EtherealN]

Next time, do a hard left or right roll at about 45 degrees and hold it steady until your out of the vertical tunnel of your downwash and into fresh air.

 

Huh? Hard left or right? The way to "get out" is to simply increase horizontal speed, which is easiest to do forwards since you won't have to work with as much drag while rotating the craft.

 

Generally, get out through increasing horizontal speed in whichever way you are currently travelling - if you are flying with 10km/h horizontal speed backwards, just apply more aft stick until out. If you are "strafing" right or left, just do it faster. No need to turn.

[StarHopper]

Actually, pushing the nose down and going forwards doesn't work well. I've found through experience that flying sideways gets you out of it much faster. And I said "roll" above, not turn. I guess it would have been more correct to say "bank". I also noticed in the wikipedia article that they say if the heli is single rotor, to go forwards, but if its tandem, go sideways. Something in the design.

 

Lol, I know, "wikipedia", but its that way in the sim as well. Going sideways rips you out much quicker for some reason.

 

As for track, I fast forwarded a for a little while, then let off. He's hovering, looking at something, then he just starts descending at high speed, around 15 m/s, looks like he's fighting it a little, but never recovers, so maybe were all seeing something different. Can someone with a good computer make a movie of the track? I tried to, but my comp nots good enough to do that and fly the sim at the same time.

Edited October 6, 2011 by StarHopper

[EtherealN]

I also noticed in the wikipedia article that they say if the heli is single rotor, to go forwards, but if its tandem, go sideways. Something in the design.

 

But the Black Shark is not Tandem. It's Coaxial; both rotors are one the same axis in the shark, thus it is not a tandem. For an example of a Tandem, think Chinook, Knight, etcetera. The reason to go sideways is that you want both rotors to go into "clean" air, and if you go forward or backward with a tandem configuration only one rotor will do so since the first rotor will have introduced a vortex for the second rotor to interact with.

 

With a Coaxial rotorcraft, this is all N/A, since no matter which way you go it's all the same - one rotor is always above the other, meaning that the lower rotor will always have disturbed air no matter what you do.

 

Going sideways rips you out much quicker for some reason.

 

I've never actually clocked it in DCS:BS (especially since it's extremely difficult to replicate parameters exactly the same each time), but your experience contradicts mine. Exiting an RVRS is done very easy for me: enter the vortex ring, stick forward and collective down, hold that attitude two seconds, then stick gently back and start arresting the fall with collective now that you have clean air.

[StarHopper]

Ahh, you put your collective down to get rid of the vortex. I usually keep mine about mid level and lean out sideways with a hard bank so my rotors can grab clean air and rip me out of the downwash. I guess with collective down, and forward, you kind of slide out of the downwash. That's why me trying to go forward wasn't working. I still had the collective up. And yeah, I was thinking tandem meant co-axial.

[EtherealN]

But Starhopper, sideways, forward, back, it doesn't change the way the rotors take on the air. The only thing this changes is the drag of the helicopter's body.

 

Going forward or to the side does not change whether or not you grab clean air or what is required to do so - in all cases it is to get enough speed to get outside of the vortex.

[Rusty_M]

I was surprised how easy it is to get out of this state. Having read about how very bad it is in the manual and on forums, I was surprised at quite how quickly you exit the VRS. Never killed or downed me yet (although plenty of other mistakes have)

[EtherealN]

StarHopper, to perhaps illustrate my point a bit better, consider the following illustration of the coaxial rotor system and the airflow induced:

 

 

The important thing to note with this picture, is that it does not matter from which direction you look - is this from the side so the front is at the left and the stern is at the right? Or are we looking through the length axis so that left is left and right is right? As far as the aerodynamics of the rotors, this does not matter.

 

The thing with sideways RVRS exit for tandem helicopters is best illustrated like this:

 

 

Note how as the two rotor discs move forward, the aft rotor enters the space previously occupyied by the forward rotor. If you are trying to get OUT of a vortex, this is obviously not efficient. If you instead go sideways, both rotors can exit the vortex immediately.

 

Now consider the difference of the above with the below:

 

 

This could be a conventional, single-rotor design, or a coaxial, doesn't matter - whichever way you go, you have the same "travel distance" to get your rotor disc out of the vortex. (This is a bit simplified since of course the rotors continually generate the thing, so unless sufficient speed is built it will never get out.) Thus it makes sense to elect to go for the direction that is easiest, which is usually forward - partly due to simple aerodynamic considerations (the thing accelerates faster when it doesn't have a broadside into the air), but obviously also because this is usually the velocity vector you already have. If you entered the state by accident while decelerating towards a FARP or something, you're usually travelling in a forward direction, making it easier to get to the required speed to exit the vortex: only needing to add 40 km/h instead of 50km/h can very easily be the difference between safety and your family being sent a very unfortunate telegram.

 

Finally, there's another consideration: what happens if you are so close that you end up touching the ground? If you are going forward, well, your landing gear is history, you probably broke the Skhval and doppler, but wheels and gear took enough of the motion to keep you alive and flying. If you are flying sideways, touching the ground will most likely cause you to flip, set your rotors into the dirt, and quite possibly explode into an impressive fireball.

[dok_rp]

Simple, yet, very elegant explanation, EtherealN. Thanks a lot for that. :smartass: :thumbup:

[StarHopper]

But Starhopper, sideways, forward, back, it doesn't change the way the rotors take on the air. The only thing this changes is the drag of the helicopter's body.

 

Going forward or to the side does not change whether or not you grab clean air or what is required to do so - in all cases it is to get enough speed to get outside of the vortex.

 

Yeah, since its a round tunnel, that makes sense. Have to try it with the blades flat. Just that in the sim, when I had the blade half way pitched, it seemed to take forever when going forward, but faster when going sideways. Maybe its just me.

[Nate--IRL--]

I was surprised how easy it is to get out of this state. Having read about how very bad it is in the manual and on forums, I was surprised at quite how quickly you exit the VRS. Never killed or downed me yet (although plenty of other mistakes have)

 

I guess you've never tried to show off online when landing at a FARP then :).

 

Remember Kids VRS is not just about your decent speed, it also applies very much to flaring hard from high to low speed. :(

 

Nate

[StarHopper]

I was surprised how easy it is to get out of this state. Having read about how very bad it is in the manual and on forums, I was surprised at quite how quickly you exit the VRS. Never killed or downed me yet (although plenty of other mistakes have)

 

Wait till you get in it 30 meters above the ground. To bail or not to bail, that is the question! :lol:

[power5]

I guess you've never tried to show off online when landing at a FARP then :).

 

Remember Kids VRS is not just about your decent speed, it also applies very much to flaring hard from high to low speed. :(

 

Nate

 

Guilty. I try to see if I can do landings like in movies. Where they zoom in at like 100km IAS and flare at the last second and come out of the flare a few meters off the ground. That will either get me in vortex or 100agl. I then try to get back to my desired altitude of like 30agl very quickly. Thus starting a vortex state in this way. I have done it good sometimes, but usually I am unsuccessful. Helps in the movies that they are not trying to land inside a small FARP circle I guess.

[Jaximus Decimus]

Guilty. I try to see if I can do landings like in movies. Where they zoom in at like 100km IAS and flare at the last second and come out of the flare a few meters off the ground. That will either get me in vortex or 100agl. I then try to get back to my desired altitude of like 30agl very quickly. Thus starting a vortex state in this way. I have done it good sometimes, but usually I am unsuccessful. Helps in the movies that they are not trying to land inside a small FARP circle I guess.

 

It also helps that they can make a helicopter that's doing 30 knots look like it's going a hundred miles an hour.:thumbup:

[Rusty_M]

I guess you've never tried to show off online when landing at a FARP then :).

 

Remember Kids VRS is not just about your decent speed, it also applies very much to flaring hard from high to low speed. :(

 

Nate

 

I've been online all of once. I should do it again. Show off? It's all I can do to get the thing to land on the FARP and not fall off the edge of the square thing. (see how much technical knowledge I have)!

[StarHopper]

Flaring hard from high to low speed seems to do all kinds of wicked things to your engine in the sim. I always get the sense of metal tearing and engines groaning.

[Smokin Hole]

I recently put together an Align TRex 250 RC helicopter. Assembling one of these things is one of the most pleasant experiences a helicopter fan will ever have, btw. Anyway, not only does it build nicely but it flies very nicely. I just figured that small RC helicopters with a 4000 RPM head-speed would be immune to VRS. Wrong! It happens all the time. You can actually hear the sound of the rotors change as they take big bites out of the turbulent downwash. Fortunately they are so overpowered that no cyclic is needed, just a hefty amount of pitch. Its possible that DCS exagerates the violence of VRS but I am comfortable that they got it right with the ease at which one enters the state.

[WildBillKelsoe]

Huh? Hard left or right? The way to "get out" is to simply increase horizontal speed, which is easiest to do forwards since you won't have to work with as much drag while rotating the craft.

 

Generally, get out through increasing horizontal speed in whichever way you are currently travelling - if you are flying with 10km/h horizontal speed backwards, just apply more aft stick until out. If you are "strafing" right or left, just do it faster. No need to turn.

 

 

WADR, the back flying is very negative, and a wash of air can jam the rudders.. Not tested or tried, but if I get into a vortex, its usually correctable for'ard... Not sideways.. :book:

[adam12]

Is this RVRS and if so how did it happen?

rvrs.trk

[159th_Viper]

Is this RVRS and if so how did it happen?

 

You were operating the Helo in its own downwash, ie you were descending through descending air. As such you were generating no lift and any attempt to increase lift via the 'normal' way, ie to increase the collective will, rather than helping, merely make matters worse.

 

At that altitude recovery was next to impossible. If you are at a low altitude, establish a hover by keeping a very, very close eye on your VVI (vertical velocity Indicator). Either keep it at zero or maintain a positive climb whilst stabilizing. Once you get the hang of it, you can maintain a 3-5m/s descent and not more, unless you know what you're doing.

 

Bottom-Line: Eyes on VVI - If you're dropping more than 5m/s you're in trouble. Drop the collective, nose down and ride the Helo out into clean air if altitude permits.......and don't forget to pray :D

 

 

Your VVI:

 

Edited October 26, 2011 by 159th_Viper
Pic added

[msalama]

flaring hard from high to low speed

 

Yup. Most definitely. And most of mine are actually just these, on- or offline...

[jib]

and don't forget to pray

:megalol: that sounds like the best advice I have heard for vortex down-wash recovery.

[EtherealN]

Regarding VVI - remember that as long as you don't have weapon systems active, you have a variometer repeater on right side of hud.

[adam12]

You were operating the Helo in its own downwash, ie you were descending through descending air. As such you were generating no lift and any attempt to increase lift via the 'normal' way, ie to increase the collective will, rather than helping, merely make matters worse.

 

At that altitude recovery was next to impossible. If you are at a low altitude, establish a hover by keeping a very, very close eye on your VVI (vertical velocity Indicator). Either keep it at zero or maintain a positive climb whilst stabilizing. Once you get the hang of it, you can maintain a 3-5m/s descent and not more, unless you know what you're doing.

 

Bottom-Line: Eyes on VVI - If you're dropping more than 5m/s you're in trouble. Drop the collective, nose down and ride the Helo out into clean air if altitude permits.......and don't forget to pray :D

 

 

Your VVI:

 

 

Too freaking awesome. I love this sim :)

 

Thanks for the answers!