Slip indicator broken in forward flight. Long standing issue. Proof Included.

[Tim_Fragmagnet]

EDIT: I have done a large amount of personal research on this topic and have posted my findings later in this thread, however I will quote them here

 

There is a lot of confusion, misinformation, and straight up speculation in this thread, I originally barely knew what was going on with any of this when I first posted. The contents of this quote are my current belief on this topic and I'm sure are the definitive answer as well.

 

On 6/6/2022 at 1:44 PM, Tim_Fragmagnet said:

So I have gone on quite the journey of research and information gathering. I have spoken with some very interesting people and looked through some interesting documents, and they all point to the same thing, the slip indicator is modeled wrong in DCS.

It also uncovered some other very serious concerns about the module as a whole, things like the de-ice reducing available power by almost 3x as much as it's supposed to, the overall performance of the aircraft being too high in most situations, and the fact that a large portion of the huey files are named AB212 after the italian twin engined UH-1N, but I won't go into detail on those here as that is not what this bug report is about.

I'm here to provide undeniable proof that the huey cruises with the pedals to the right. @fapador had provided charts of the control positions for hueys in forward flight, however those charts were of a huey with experimental equipment installed. Now, while that huey with the experimental infrared equipment is stated to have "essentially unchanged handling" in its document, I wasn't happy with just that, I wanted it to be unquestionable. So I located that document, and others like it. It turns out that the flight engineers had the foresight to run the data twice, once with their experiment installed, and once with the huey in a clean configuration. I have compiled the most relevant charts of this data.
Not only are the proceeding sets of data gathered from clean hueys, but they are from 2 separate hueys.

Minus the variance from differences in the test variables and the aircraft themselves such as physical control limit differences, weight, density altitude, center of  gravity, etc, this is 2 separate hueys, showing the same data, their serial numbers are provided.

The first set of data is much like what fapador posted, the positions of the controls while in trimmed level forward flight.

null

To simplify this, "directional control" is the anti-torque control, and it has about 6.8 inches of total travel, it is measured as "inches from full left" meaning if the datapoints are at 3.4 inches, the pedals are centered, if they are above 3.4 inches, they are to the right. Calibrated airspeed is at the bottom of the charts. The only datapoint below centered pedals is the 112knot datapoint for the second chart. IE, data gathered from a huey at a weight of 8980lbs. The heavier the aircraft, the more torque is required, and thus the more left pedal is required. The pedals only go to the left at a very high weight and at high speed with the collective raised by nearly 7 inches.

You'll notice that before that, the pedals are nearly at least 1 inch to the right of center, in the case of the first chart, even more than that.

Lets complicate things.

These charts depict data gathered from hueys in flight with the collective remaining in the same position across the entire set of data.

I see data showing hueys flying at 90-110 knots with pedals that are 3.6-4 inches from full left, ie 0.2-0.6 inches to the right, at a weight of 8960-9306lbs.
Now I just got done saying that the pedals were to the left because of the huey being at a high weight load. Why is this one saying they are to the right at an even higher weight.

That is because these hueys are flying without the increase in torque from a high collective setting. So yes, again, more collective DOES MEAN the pedals should be more to the left. However at the same time, it very clearly shows that the huey flies with pedals to the right in most situations.

Now how about a change of pace.

This is a chart depicting how the aircraft performs in a sideslip.

One huey, 2 situations, the square datapoints are at 66knots, the circular data points are at 97 knots. The Shaded datapoints are there to represent a trimmed state. IE the slip indicator is centered.

I'm seeing pedals to the right in a trimmed state. Not only that, I'm seeing a trimmed state with a slip angle of about -0.5 degrees. not even remotely close to what the DCS huey flies with in trim.

The huey flies mostly straight with the slip indicator centered. Yes, there are situations where the slip indicator will be centered but you will be crabbing, but not in normal flight.

If you're thinking "oh they just mean trim as in not crabbing, not with the slip indicator centered", I have proof of otherwise.

Here's the first proof

The trim state is very clearly not 0 degrees of slip. Not enough?

The trim state isn't even touching the zero degrees line. Somehow still not enough?

You want worded proof that they use the slip indicator ball as the trim reference?

 

Ballwidths from trim

 

It is undeniable, these documents use the slip indicator as the measurement of trim.

As a sidenote, that last one is far from a clean huey, it's just there to provide the worded proof of the slip indicator being used to trim, that huey actually has a massive radar dish on the right side, do not use that for flight performance reference.

Also, if you're questioning the source of all this data

These are the 2 main sources but there are others for secondary knowledge.

 

 

 

 

So.

 

NOT ONLY, does the huey fly with the pedals to the right in most situations, but it also flies almost perfectly straight with no sideslip with the slip indicator centered.

 

So what's happening with the DCS huey?

At this point I believe I know.

As you gain speed, several things happen in relation to this

The tail rotor gains power
The tail fin starts generating its own anti torque due to its shape
The slipstream of air over the airframe wants to force the tail behind the body of the aircraft (also known as weathervaning). Like the fins on a dart or arrow keeping it flying straight.

If the pedals remained untouched, all 3 of these things combined would cause the nose to kick left, and the slip indicator to move to the right.
In game, the nose DOES kick left if you don't correct with the pedals, as far as I can tell, the flight model IS CORRECT. If you ignore the slip indicator and fly with the pedals to the right in dcs, you even get that left skid low attitude for straight level flight.
However the slip indicator does not move to the right. Why?

That is because the slip indicator is mostly tied to the collective, it is mostly tied to the amount of torque you are generating, this isn't wrong, this mostly works, but the flaw is that it is completely ignoring the aerodynamic effects of forward (or even rearward) flight.

These aerodynamic effects start immediately upon gaining speed, they don't wait until you reach cruise, they don't wait until you have entered translational lift.

The flight model seems to includes these, but the slip indicator does not take them into account.

In short, the slip indicator is incorrect at ANY forward speed.

 

It is now entirely unquestionable, the slip indicator does not work properly.

It has been almost a decade, I don't think it has ever worked.

Please, I think it's time.

 

Note: I have changed the title to more accurately reflect the nature of the issue which has in turn cleared the "investigating" prefix tag from the title, if someone could return it to its place I would appreciate it. @Flappie

 

Anything past this quote is the original text of the opening post.

 

This issue has been present in this module since at least 2016, if not earlier. I figured something as major as a broken flight instrument would be fixed relatively quickly but here we are.

This has been reported before as the flight model not requiring right pedal input at speeds nearing and passing cruise.
That is entirely false.

The flight model has the right pedal requirement at these speeds properly implemented.

The actual issue is that the slip indicator does not properly operate alongside this. As the need for right pedal increases, the leftward motion of the slip indicator increases, almost as if its effects are completely inverted.

 

This is not some aerodynamic effect, it's not wind, it's not translating tendency, it's not the fact that the map is not projected on a globe, it's not user error, it's not a flight model issue.

 

This is a genuine bug with a flight instrument.
Don't believe me?

Here is an image of the huey in cruise with the ball centered alongside an image of that exact moment in tacview.

Notice anything?
Because I do

For comparison, here's an image of the huey in cruise that's actually closer to coordinated flight, look at the slip indicator

Notice anything?
I do, the slip indicator is wrong.

 

Oh but surely the SMEs didn't let this slip by, surely this is how it's supposed to be. Right?

No.

Go look up any flight videos of the huey that show the cockpit during level cruise flight.

You'll find that at 90knots, the slip indicator will be centered with the pedals slightly to the right, pretty much exactly as much as is required in DCS.

The flight model is correct, it's quite good.

The slip indicator is broken.

 

I just want to be able to trust my flight instruments.

Please, it's been long enough.

Edited June 8, 2022 by Tim_Fragmagnet

[Fakum]

Im all for fixing it, Im not sure they will even if deemed broke. If it is in need of repair, what can we do about it if it falls on deaf ears?

[Flappie]

4 hours ago, Tim_Fragmagnet said:

Go look up any flight videos of the huey that show the cockpit during level cruise flight.

You'll find that at 90knots, the slip indicator will be centered with the pedals slightly to the right, pretty much exactly as much as is required in DCS.

Would you please find one for us? I'd be happy to ask devs about this, but I'm still not sure if it's a bug or not. Having a real life Huey cockpit video in action would be a good proof.

[Tim_Fragmagnet]

7 hours ago, Flappie said:

Would you please find one for us? I'd be happy to ask devs about this, but I'm still not sure if it's a bug or not. Having a real life Huey cockpit video in action would be a good proof.

Absolutely

lets start with this

94 seconds in we get this gem of a frame 

Pedals, slightly to the right
Speed, around 105 knots
Slip indicator
Centered
You can watch it throughout that whole flight, even when it's going around 100 over the runway near the end, pedals to the right, ball centered.

 

here's another

There aren't many moments of interest but, at 5:20

70 knots
pedals right (you can tell because you can see the left foot and small amount of pedal back from center)
ball centered
you can even see the LINES
If anything it's almost as if the ball is slightly RIGHT

 

here's a video of a UH-1B, the airframe is shorter and it's a different engine in the airframe most likely, but the flight dynamics are pretty much the same.

At 4:50 in the simulated rocket dive

85 knots
pedals right
ball centered

 

OK

1 example, that's an outlier
2 examples, that's a coincidence
3 examples, that's a pattern

Not enough? How about a fourth. 

 

Check the cockpit at 1:35

80 knots
pedals right
ball centered

The slip indicator in the DCS Huey module does not function properly.

To reclarify the flight model is fine, it properly has the requirement for right pedal input to fly straight at speed, the issue is that the slip indicator in DCS acts in direct opposition to this and instead incorrectly asks for left pedal input.

Edited January 14, 2022 by Tim_Fragmagnet

[fapador]

Thanks for this post, and for using all the videos I have meticulously searched and posted about this issue. I have personally contacted many people over the years about this discrepancy but to no avail... . They consecutively  doubted me, called me complete ignorant and that I don't know what I am talking about. They always kept insisting on the ground that  since the UH-1H model is developed by SME's it is the seed of perfection.  If only  ED  developers will stop flying kite and pay some attention at once...  

Edited January 14, 2022 by fapador

[Flappie]

24 minutes ago, fapador said:

If only  ED  developers will stop flying kite and pay some attention at once... 

ED devs do listen carefully. DCS is like their baby, and they need proof to get confirmaton of a bug or an inaccuracy. These videos might do.

[Tim_Fragmagnet]

For a comparison I have put the freeflight huey into the same parameters as the first video while it's going down the runway
I even have about the same fuel and the ground track is heading down the runway. (that's how much sideslip the slip indicator makes you fly with)
there is one exception
the pedals, look at them
the slip indicator is mostly centered (IT WANTS EVEN MORE LEFT PEDAL)
but the pedals are left

 

If at this point, you don't think there is anything wrong with the slip indicator, I don't know what else to show or tell.

Edited January 14, 2022 by Tim_Fragmagnet

[Flappie]

I prefer video proofs to be honest. I just remembered Black Shark Den posted a great 360 video of a Huey flight, here:

The ball is not always easy to distinguish from the pixels, but it seems centered here as well while the Huey is fast. I'll report and see if devs agree.

Edited January 14, 2022 by Flappie

[Flappie]

I've found something interesting when going fast: the ball goes to the left when the cyclic is pushed forward, but it goes back to the center (where it should be when going straight ahread) as soon as the cyclic is pulled backward.

[Tim_Fragmagnet]

The issue isn't the placement of the ball on it's own

it's the placement of the ball in relation to the pedals

 

in the real thing, at speeds seemingly as low as 70 knots, to fly straight, you are required to have some right pedal input
this seems to be mostly modeled in the module

however also in the real thing, the slip indicator is centered with the pedals to the right
however in the module, if you apply the correct amount of right pedal to fly straight, the slip indicator incorrectly moves left

 

in the module, you can center the slip indicator with enough left pedal, but you will be flying with a disgustingly large amount of sideslip, despite the slip indicator saying otherwise.

something is wrong with the slip indicator, I'm sure you see it now as well. I just hope it's portrayed to the team in an effective manner. This issue has been brought up before but worded in such a way that it was made to look like a flight model issue instead of an issue with the slip indicator itself.

Edited January 15, 2022 by Tim_Fragmagnet

[Flappie]

11 minutes ago, Tim_Fragmagnet said:

something is wrong with the slip indicator, I'm sure you see it now as well. I just hope it's portrayed to the team in an effective manner. This issue has been brought up before but worded in such a way that it was made to look like a flight model issue instead of an issue with the slip indicator itself.

We shall see...

And if I fail, you can become a beta tester too and use the proper wording.

[admiki]

7 hours ago, Flappie said:

We shall see...

And if I fail, you can become a beta tester too and use the proper wording.

How?

 

[Flappie]

Casting couch, of course.

[admiki]

1 hour ago, Flappie said:

Casting couch, of course.

If interviewer isn't a nice blonde girl, I'll pass TYVM

[War_Pig]

I noticed a while ago that when flying at high speeds and using external views, with the ball centered the aircraft seems to be flying sideways relative to the direction of flight.  I assumed it was just something helicopters did, but it's definitely a thing in DCS.

[sLYFa]

The ball doesn't indicate sideslip as in ground track vs heading, you need doppler or INS for that. What the ball shows is lateral forces. You can have a sideslip of 90° (i.e. flying sideways) and a centered ball as long as you dont have any lateral acceleration. In stationary forward flight, there are basically two options (assuming zero wind): accept a small crab angle but no lateral forces (i.e. center ball) or have no crab angle but a small lateral force (i.e. ball of center). This is owed to the tailrotor pushing you sideways, which either creates crab or has to be cancelled out with a bit of bank, the latter moving the ball of center (you are basically rotating the gravity vector relative to the aircraft, resulting in a small lateral force). Your screenshots showcase just that, although you have left bank in both so the first shot should also show some left ball, maybe there was a tad bit of left turn involved which cant bee seen.

Btw, coordinated flight does not mean zero crab angle but no lateral forces on the airframe (i.e. the sum of force vectors pointing straight up or down relative to the airframe). The term "slip indicator" is a bit confusing for helicopters. In an airplane, lateral forces are often the result of some aerodynamic slip, e.g. adverse yaw (very noticeable in the Tomcat at moderate and high AoA) and the ball can therefore be used as a reference for actual aerodynamic sideslip. For a helicopter its not that simple, since there are more forces, both aerodynamical and mechanical, involved. I made a little sketch showcasing the zero crab situation and where the lateral force relative to the airframe comes from.

[admiki]

I believe what sLYFa is saying is correct. I don't know what is modeled in DCS Huey,  but there is a reason a lot of IRL helicopters rely to piece of string glued to windshield instead of ball.

 

Edited January 18, 2022 by admiki

[Tim_Fragmagnet]

What you're describing is translating tendency, which is not the source of this.

I say this in the first post.

Because if it were, the pedals and slip indicator would match the real thing.

Edited January 18, 2022 by Tim_Fragmagnet

[admiki]

28 minutes ago, Tim_Fragmagnet said:

What you're describing is translating tendency, which is not the source of this.

I say this in the first post.

Because if it were, the pedals and slip indicator would match the real thing.

 

Well, translating tendency exists all the time, only in forward flight it's vertical tail that is doing most of the work. to a point where you need right pedal to counteract it

[sLYFa]

Claiming something to match or not match "the real" thing based on a few short videos where we don't know which fuel/payload and specific Huey model is flown is not enough I'm afraid. Are there any balancing curves (i.e. what control inputs are needed for level flight at xx KIAS and yy GW) for the Huey? Russian chopper manuals are full of them so maybe there are some for the Huey too.

On 1/13/2022 at 2:41 PM, Tim_Fragmagnet said:

The actual issue is that the slip indicator does not properly operate alongside this. As the need for right pedal increases, the leftward motion of the slip indicator increases, almost as if its effects are completely inverted.

So you are basically saying that translating tendency is reversed as in more right pedal requires more bank? Maybe look for the bank angle in stationary, no crab flight at various speeds to confirm that.

 

Edited January 18, 2022 by sLYFa

[Tim_Fragmagnet]

I have provided 4 separate pieces of evidence that support my claim. It's up to you to provide real evidence that supports your claim.
So unless you're saying all 4 helicopters have broken slip indicators, or all 4 helicopters are operating under the exact same parameters. An absurd idea either way.
Either hop in the module and show us, or find at least 3 videos of a huey cruising with the pedals to the left and the ball centered.

 

And you know what

here's a F I F T H, now provide me 4 supporting your claim
 

2:16

65 knots
Pedals right
ball centered

Edited January 18, 2022 by Tim_Fragmagnet

[admiki]

OK, I took a look at all 4 videos. Only 3rd video you can see both pedals, but that is not important. In all of those videos, every single helicopter is crabing to the right. Not as much as in DCS, but it is there.

I said it already, there is a reason that IRL helicopters are gluing on yaw strings

 

Edited January 18, 2022 by admiki

[Tim_Fragmagnet]

22 minutes ago, admiki said:

OK, I took a look at all 4 videos. Only 3rd video you can see both pedals, but that is not important. In all of those videos, every single helicopter is crabing to the right. Not as much as in DCS, but it is there.

And every single one of them has the ball centered with the pedals to the right.

even the 5th one I just posted.

That's FIVE separate hueys with slip indicators centered with the pedals to the right.

The DCS huey is wrong.

Edited January 18, 2022 by Tim_Fragmagnet

[gnomechild]

Yeah the crabbing isn't the issue here. Obviously translating tendency is always present. But watching those videos vs flying in DCS it's very plain to see there's a difference in the instrument. If you start out coordinated and keep moving the pedals to stay coordinated (eventually needing to add right pedal as speed picks up), the instrument just wanders off to the left. It doesn't make any sense. It's not about translating tendency its about the turn indicator being broken. 

Edited January 18, 2022 by gnomechild

[Tim_Fragmagnet]

It's almost like the slip indicator takes the absolute torque value (such as from the torque indicator) into account for where the ball should be, which would explain quite a lot.
I don't know though, I can't confirm that, because I don't have proof.
I just know the slip indicator has some serious issues to the point where it heavily degrades flight performance and enjoyment.

Edited January 19, 2022 by Tim_Fragmagnet