Vortex Ring State

[last1976]

I recently flew the Huey after a long time, and I got to admit that in my opinion you have sacrificed the maybe more realistic earlier (last months, not the very early ones) flight model to a more arcade like. The vortex ring state seems to be practically non existent.

 

I dont claim this to be correct. It just felt like that for me.

Edited January 7, 2015 by last1976

[outlawal2]

I recently flew the Huey after a long time, and I got to admit you seem to have sacrificed the earlier realistic flight model to a more arcade like. The vortex ring state seems to be practically non existent. So is this the future of sims? Giving in to all time winers?

 

Those who couldnt get along with earlier flight model should have gone to game mode.

 

 

Would that be like the whining you are doing right now with this very post?

 

The fact of the matter is that when first released the Huey was FAR too prone to VRS (And this is not my opinion, but based on real world Huey pilots that have commented on this very forum..) Belsimtek revised the flight model in response to actual real life pilot feedback, not whining..

 

If you enjoy fighting VRS at every point in a flight please be sure to try the MI-8 as it still is too prone to VRS (In my opinion) and if you can land that thing without scaring yourself silly then you ARE the man...

[ricktoberfest]

If you research it properly, you'll see that VRS is actually over simulated in DCS. I believe the realistic value of descent for a Huey would be in the range of 1500 fpm or more. 800 fpm is the recommended max for safety

[last1976]

Would that be like the whining you are doing right now with this very post?

 

Well you got a point. But as ricktoberfest said you would expect a descend rate of up to 1500 fpm. But right now it is possible to recover without gaining forward speed of descends 3000 fpm plus.

 

You was right the very early fm was to prone to VRS and I was aware of that, but right now its the other way around in my opinion.

[HuggyBear]

...you seem to have sacrificed the earlier realistic flight model to a more arcade like...

 

What is your opinion based on?

 

You post with such confidence and certainty I assume you are a UH-1H pilot...

 

You prefer an unrealistic, mission-wrecking simulation of a situation most UH-1H pilots have never experienced?

 

The current FM isn't perfect, no sim FM is perfect, but it's far more accurate than earlier versions.

 

- Bear

[b00ce]

While I'm certainly no real-life Huey pilot and can't vouch for the realism in this regard, you appear to be correlating difficulty with realism. Just because it may be easier than it used to be, doesn't make it particularly unrealistic.

 

http://forums.eagle.ru/showpost.php?p=2209715&postcount=16

[msalama]

in my opinion.

 

Yes, exactly, in your opinion ;)

[last1976]

What is your opinion based on?

 

You post with such confidence and certainty I assume you are a UH-1H pilot...

 

You prefer an unrealistic, mission-wrecking simulation of a situation most UH-1H pilots have never experienced?

 

 

 

- Bear

 

 

??

 

As allready posted in my second post, I acknowledge that my first post was a little overacted? So now you do ?

 

But my statement of the second post remains, I doubt the UH-1 with full tanks, is capable to recover from a dive about 3000+ fpm in hovering state, without the need of gaining some forward speed.

Edited January 6, 2015 by last1976

[last1976]

When performing a vertical descent from an altitude of 15 ft or higher, ensure a sink rate less than 8.3 ft/sec (500 ft/min). A sink rate greater than 8.3 ft/sec can result in a vortex ring state (VRS), during which the sink rate can rise uncontrollably within 1 – 2 seconds up to 2000 ft/min, which will lead to a hard landing and possible damage or destruction of the helicopter.

 

From Belsimtek flight manual.

[Flagrum]

??

 

As allready posted in my second post, I acknowledge that my first post was a little overacted? So now you do ?

 

But my statement of the second post remains, I doubt the UH-1 with full tanks, is capable to recover from a dive about 3000+ fpm in hovering state, without the need of gaining some forward speed.

Could you post a track, please? I just tried it a few times and 1/5 times I could recover ... but I am not 100% confident that I had no fwd speed in that attempt. The other 4 attempts I found it difficult to even get a descent rate of >3000, but once archieved, I could slow it down only up to those 3000 ft/min. Maybe if one is very carefull and has LOTS of air beneath the skids ... but I could not do it (starting at 3500 ft AGL).

[last1976]

Could you post a track, please? I just tried it a few times and 1/5 times I could recover ... but I am not 100% confident that I had no fwd speed in that attempt. The other 4 attempts I found it difficult to even get a descent rate of >3000, but once archieved, I could slow it down only up to those 3000 ft/min. Maybe if one is very carefull and has LOTS of air beneath the skids ... but I could not do it (starting at 3500 ft AGL).

 

Well to be honest I couldn't reproduce it that way either.:music_whistling: The Vrs exists at about 1500fpm - 2000fpm ? Maybe it is just easier to recover. When I hold the heli exactly in position it wont recover from higher descent rates.

 

So well, I acknowledge that under this conditions this thread is becoming unnecessary as my experience is not that great, that i would claim this is realistic or not. Maybe it is.

 

At the time I opened the thread I had a situation where it seemed the VRS is not implemented anymore.

 

I think opening this thread was an act of precipitation

Edited January 6, 2015 by last1976

[ricktoberfest]

Vortex Ring State

 

Another thought- if the collective is zeroed out (which it probably needs to be to achieve 3000fpm descent) you're actually in autorotation, not VRS. VRS requires collective to e above 20% I believe

[HuggyBear]

I acknowledge that...this thread is...unnecessary...

 

It helps to figure these things out before shooting your mouth off.

 

Or at least ask politely.

 

- Bear

[b00ce]

Another thought- if the collective is zeroed out (which it probably needs to be to achieve 3000fpm descent) you're actually in autorotation, not VRS. VRS requires collective to e above 20% I believe

The trick is once you start descending about 1500 fpm pull a little more and more collective and you'll fall faster.If you pull too much

too quickly you'll be able to pull out of it.

 

Contrary to popular belief, there are in fact two ways out of VRS; the lesser known being Jeremy Clarkson screaming at the top of his lungs. This is assuming you have the power required to do so. If you don't, you'll just make it worse. And then the ensuing fireball will probably kill you.

 

 

 

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.

Under certain conditions the helicopter may descend at a high rate which exceeds the normal

downward induced flow rate of the inner blade sections (inner section of the rotor disk). Therefore, the

airflow of the inner blade sections is upward relative to the disk. This produces a secondary vortex

ring in addition to the normal tip vortex system. The secondary vortex ring is generated about the point

on the blade where airflow changes from up to down. The result is an unsteady turbulent flow over a

large area of the disk which causes loss of rotor efficiency although engine power is still supplied to

the rotor system.

 

1-193. Figure 1-73 shows normal induced flow velocities along the blade span during hovering flight.

Downward velocity is highest at the blade tip where blade speed is highest. As blade speed decreases

nearer the center of the disk, downward velocity is less.

 

1-194. Figure 1-74 shows the induced airflow velocity pattern along the blade span during a descent

conducive to settling with power. The descent is so rapid, induced flow at the inner portion of the

blades is upward rather than downward. The upflow caused by the descent has overcome the

downflow produced by blade rotation and pitch angle.

 

1-195. If this rate of descent exists with insufficient power to slow or stop the descent, it will enter the

vortex ring state (figure 1-75). During this vortex ring state, roughness and loss of control occur due to

turbulent rotational flow on the blades and unsteady shifting of the flow along the blade span.

 

1-196. The following conditions must exist simultaneously for settling with power to occur:

• A vertical or near-vertical descent of at least 300 feet per minute (FPM). Actual critical rate

depends on gross weight, rotor RPM, density altitude, and other pertinent factors.

• Slow forward airspeed (less than ETL).

• Rotor system must be using 20 to 100 percent of the available engine power with insufficient

power remaining to arrest the descent. Low rotor RPM could aggravate this.

 

1-197. The following flight conditions are conducive to settling with power:

• Steep approach at a high rate of descent.

• Downwind approach.

• Formation flight approach (where settling with power could be caused by turbulence of

preceding aircraft).

• Hovering above the maximum hover ceiling.

• Not maintaining constant altitude control during an OGE hover.

• During masking/unmasking.

 

1-198. Recovery from settling with power may be affected by one, or a combination, of the following

ways:

• During the initial stage (when a large amount of excess power is available), a large application

of collective pitch may arrest rapid descent. If done carelessly or too late, collective increase can

aggravate the situation resulting in more turbulence and an increased rate of descent.

• In single-rotor helicopters, aviators can accomplish recovery by applying cyclic to gain airspeed

and arrest upward induced flow of air and/or by lowering the collective (altitude permitting).

Normally, gaining airspeed is the preferred method as less altitude is lost.

• In tandem-rotor helicopters, fore and aft cyclic inputs aggravate the situation. By lowering thrust

(altitude permitting) and applying lateral cyclic input or pedal input to arrest this upward

induced flow of air, the aviator can accomplish recovery.

 

1-199. Several conclusions can be drawn from figure 1-76, page 1-62—

• The vortex ring state can be completely avoided by descending on flight paths shallower than

about 30 degrees (at any speed).

• For steeper approaches, the vortex ring state can be avoided by using rates of descent versus

horizontal velocity either faster or slower than those passing through the area of severe

turbulence and thrust variation.

• At very shallow angles of descent, the vortex ring wake is dispersed behind the helicopter.

Forward airspeed coupled with induced-flow velocity prevents the upflow from materializing on

the rotor system.

• At steep angles, the vortex ring wake is below the helicopter at slow rates of descent and above

the helicopter at high rates of descent. Low rates of descent prevent the upflow from exceeding the

induced flow velocities. High rates of descent result in autorotation or the windmill brake state.

 

 

[ff4life4]

Ill let someone else more experienced than me chime in, but from my understanding the Mi8 is easier to get into Vrs due to low loading on the rotor system, if the aircraft is light.

[b00ce]

Ill let someone else more experienced than me chime in, but from my understanding the Mi8 is easier to get into Vrs due to low loading on the rotor system, if the aircraft is light.

You also should have the power available to recover simply by pulling more collective. In theory... :music_whistling:

[dahui]

You also should have the power available to recover simply by pulling more collective. In theory... :music_whistling:

 

 

Correct. An empty Helicopter with much power is easy to recover from the Vortex. (AS350B3) While a fully loadet is quite dangerous.

 

But, you can also play with the Vortex to descent fast and before hitting the ground just recover it and perform a normal approach

[last1976]

It helps to figure these things out before shooting your mouth off.

 

Or at least ask politely.

 

- Bear

 

As your tone is arrogant and offensive, I suggest you shift your coarse manners. If you managed it I maybe consider to take advice from you.

 

Yours Sincerely

[derelor]

HuggyBear, what is your opinion on the current VRS simulation in DCS: UH-1H? Should anything be changed?

 

AFAIK you're the only real UH-1H pilot around here.

[Cibit]

In my humble opinion the huey is easier to recover if you happen to enter vortex state than the Mi-8 but really don't get so out of control that it happens;)

[HuggyBear]

As your tone is arrogant and offensive, I suggest you shift your coarse manners. If you managed it I maybe consider to take advice from you.

 

Yours Sincerely

 

Do you seriously have no idea why I responded to you like that?

 

Your original post was not only arrogant and offensive, but also stupid.

 

Using words such as 'I believe' or 'I think' can make all the difference when you have no idea what you're talking about.

 

I don't care if you take my advice, I'm not offering you any.

 

I'll ignore you from now on.

 

- Bear

[HuggyBear]

HuggyBear, what is your opinion on the current VRS simulation in DCS: UH-1H? Should anything be changed?

 

AFAIK you're the only real UH-1H pilot around here.

 

G'day Derelor,

 

Hard to tell with certainty. I did some silly things with the Huey and never approached anything resembling VRS, so I can't suggest where the onset lies exactly.

 

The original implementation was definitely wrong though.

 

I've experienced an 800-1000 fpm vertical descent which we incorrectly arrested with collective (tired, distracted and careless) with no problem.

 

I apologise if I sounded like only pilots have a right to post facts, that's not my intention at all.

 

Sometimes I just get sick of hearing nonsense proclaimed as fact with absolute certainty, while belittling those who feel otherwise as whiners.

 

- Bear

[msalama]

The original implementation was definitely wrong though.

Yah, you dropped into a VRS if you so much as sneezed :D

 

But here's my inconsequential $0.0002 about this: I think it's realistic now, based on what I've read about the phenomenon, and I also think I've read that the RL Huey is actually quite forgiving as it comes to VRS. Not that you can't get into one in v1.2.14 if you're stupid enough however; happened to me just the other day when I let my vertical speed fall below 1500fpm! Did survive the encounter, though - but barely, with literally inches to spare :cry:

 

Anyway, I'm inclined to believe that it's actually quite well modelled now (but am also willing to be corrected if someone comes up with tangible and unequivocal data proving otherwise).

[P3CFE]

Followed this thread wit interest.

Shows the quest for reality in simulators...specially DCS.

 

The last answer from " Huggybear" made me think.

 

Whe, as users want the realism so bad that we even want to experience things and situations that a real pilot wouldn't dare to try out in real live, or just does not meet during normal operations.

 

Im my opinion the goal of a simulator is met, if whe as simmers, can experince what e real live pilot goes through and has to do during flight, including the emergency situations which are included in the pilot training in RL.

 

So i Hope that most effort of the devs goes in to meeting the realism as is known from real live.

 

Maybe it is to much to ask to simulate situations after random damage or after an aircraft is completely departed from normal flight envelope.

 

But .just my thoughts..was just wondering !!

[outlawal2]

In my humble opinion the huey is easier to recover if you happen to enter vortex state than the Mi-8 but really don't get so out of control that it happens;)

 

Absolutely...

 

Not sure if there may be some differences with different input controls, but I know some folks say the MI-8 is much better about VRS than it used to be, but I can still hardly fly the thing and yet NO ISSUES at all with the Huey...

 

Weird, and I have no explanations for it...

(Not going to call it a bug, but definitely an issue for me with MI-8 and no idea why that is)

 

Anyone else feel this way?