The tail rotor is implemented incorrectly.

[Tim_Fragmagnet]

This has major implications on the flight model, to the point where the entire flight model could be considered incorrect.

 

null

This document has a lot of interesting information in it, but what we care about is this graph.

This graph shows the relation between the position of the anti-torque pedals and the pitch of the blades of the tail rotor.

It shows that at full left (0%), the tail rotor blades have a pitch of 18 degrees.
It shows that centered (50%), the tail rotor blades have a pitch of 4 degrees.
It shows that 65% from full left, the tail rotor blades have a pitch of 0 degrees, making no thrust.
It shows that 100% from full left, the tail rotor blades have a pitch of -10.5 degrees, making nose right thrust.


The DCS huey's tail rotor blades don't even come close to that.

Here is a picture with the pedals full left. The blades have a pitch of about 22-25 degrees.

 

Here is an image with the pedals centered. The blades have a pitch of about 10-12 degrees.

Here is an image of the pedals all the way to the right. The blades have a pitch of about 0- -2 degrees, we'll assume 0 degrees and the camera isn't directly above the top of the blade so it looks a little angled.

 

 

OK, so maybe you think it's just an animation error.

I can prove that it is not.
I can prove that is how it is modeled in the flight model.

But first lets look at that graph again

about 24% from full left (52% left of center) shows the blades at a pitch of around 10.5 degrees.
100% from full left (full right) shows the blades at a pitch of around 10.5 degrees in the other direction.

With the helicopter stationary on the ground, either of these positions should place the exact same amount of stress on the driveshaft.
This means that if we turn the governor off, both positions should reduce RPM by the same amount.

Not even close.
The bottom left example shows the pedals 25% from full left, considered 50% left of center, this means that the tail rotor blades will be at a SMALLER pitch than what full right should be, therefore should reduce RPM by LESS than the pedals full right would.

The top middle example shows the pedals 100% from full left, all the way to the right, barely even touching the RPM, infact the RPM is slightly higher.

 

 

The tail rotor, as modeled on the DCS UH-1H, is modeled incorrectly, not only visually, but also in terms of how it affects the flight model.

The tail rotor is modeled as if full right pedal puts the blades at a pitch of 0 degrees. Producing no thrust.

The repercussions of this encompass basically the entire flight model. With the tail rotor acting the way it does, it means that the phyiscal strength of relative torque values is entirely incorrect, and proper trim in a properly modeled aircraft would technically be impossible in some basic turns.

Edited April 13, 2023 by Tim_Fragmagnet

[Tim_Fragmagnet]

So how messed up does this actually make the flight model?

Well we have graphs from the research into the slip indicator bug, the most important one being the lateral stability graph.
Here is that graph.

 

So we can do a bit of math, if 65% from full left is flat blade pitch for the tail rotor
We can calculate that 4.45 inches from full left is flat blade pitch.
Looking at the directional control position graph at the bottom there, we can see we are in trim at 4 inches from full left, or 58.8% from full left.

Since the tail rotor is at flat pitch when full right in DCS, we can now calculate something very funny.
If we consider 4.45inches from full left to be full right, just like it is in DCS.
If we also consider we need to trim at 4 inches from full left.
To properly trim the DCS huey if all of the forces were prorperly tuned, the pedals would need to be 89.8% from full left.

OK but where would that put us on the graph in a real huey?

Here, with the nose 29 degrees to the right

 

Absolutely incredible.


Now if we consider, the real thing is trimmed 4 inches from full left.
What does that put the blade pitch at?
Well at 58.8% from full left, our tail rotor blade pitch graph puts the blades at a pitch of about 2 degrees.
Meaning the tail rotor is doing VERY LITTLE.
This is because at speed the tailfin applies its own anti-torque force alongside the other aerodynamic effects doing similar things to either counter or lessen the required torque.

Edited September 15, 2022 by Tim_Fragmagnet

[Tim_Fragmagnet]

Here's more tail rotor blade pitch data

 

From this document

[DishDoggie]

I know you know way more then I do about the subject. When I worked as a State Certified Laboratory Analyst in the Water Industries a valid point to watch for and then Question is coming to be asked. Your reference material is without a doubt true and can be trusted as Factual. From 1972 and 1988 going forward but what about before that time? The UH-1h is from before the dates used and I have no Idea if that matters but I must question what is was for this model from a earlier time line. Even so you can tell by flying the Model that you are correct that i fell it is not modeled correctly when real Huey pilots have said so as you do. I am impressed with your knowledge and the information display you have presented. Very Good Job.

Edited December 18, 2022 by DishDoggie

[ams999]

2 hours ago, DishDoggie said:

[...]From 1972 and 1988 going forward but what about before that time? The UH-1h is from before the dates used[...]

 

Hmm, what I usually found is the opinion that the DCS Huey is probably a version from the 80s, so I guess it should apply to it.

 

[Tim_Fragmagnet]

13 hours ago, ams999 said:

Hmm, what I usually found is the opinion that the DCS Huey is probably a version from the 80s, so I guess it should apply to it.

 

It's not an opinion, 

From the WSPS our huey is AT THE EARLIEST from 1982

Here's the document of them testing it on the huey specifically. 

 

 

But that is irrelevant, as our huey, as per the module's manual, has the composite blades installed. In the second post you see the document for them testing the composite blades, in 1988.

Our huey is at the earliest from 1988.

Edited December 19, 2022 by Tim_Fragmagnet

[DishDoggie]

Good Discussion and awesome facts. I will add just a few things from ED's Web Site and From the Museum of Flight.

It looks to me like Belsimtek "MAY HAVE" I can not speak for them and I may not have it right. "Belsimtek is not around any more" Belsimtek use reference material from many people and many years for the model. I have no idea how it was used for the making of the UH-1H. So a point I will make is just the Big one that stands out for me. and that is the TYPE of Huey we are talking about. The UH-1 Iroquois NOT UH-1D or any other upgraded version. P{lease read the Museum's facts on production years and numbers made. Making me still feel we are pre 80's for the Huey Iroquois version we have in the Sim.

[Tiger-II]

I don't think this issue is limited to the Huey. All the helicopters have issues when it comes to pro-torque input.

I think ED think that it is purely torque that rotates the helicopter in one direction, but this actually isn't the case. The tail rotor is quite active even in the pro-torque direction.

It has another effect, too: the helicopter should be harder to turn in the same direction as the main rotor, but the opposite is true in the sim.

[Tim_Fragmagnet]

On 12/19/2022 at 9:52 AM, DishDoggie said:

Good Discussion and awesome facts. I will add just a few things from ED's Web Site and From the Museum of Flight.

It looks to me like Belsimtek "MAY HAVE" I can not speak for them and I may not have it right. "Belsimtek is not around any more" Belsimtek use reference material from many people and many years for the model. I have no idea how it was used for the making of the UH-1H. So a point I will make is just the Big one that stands out for me. and that is the TYPE of Huey we are talking about. The UH-1 Iroquois NOT UH-1D or any other upgraded version. P{lease read the Museum's facts on production years and numbers made. Making me still feel we are pre 80's for the Huey Iroquois version we have in the Sim.

 

 

So you think we have a UH-1H from the 70s even though I've proven that we don't, and you think that would make a difference?
Well fine
Here is the flight test data of the YUH-1H from 1970, the literal pre production UH-1H, the one every single UH-1H would be based off of.

 

 

Here is page 224

 

full left 19 degrees to full right 7 degrees in the other direction

From the START, the UH-1H has had the tail rotor blades able to pitch inverted to push the nose to the right faster.
Because if it COULDN'T, then it wouldn't be able to properly trim in certain flight profiles.



It's not an opinion, it's not some crazy made up scheme.

It's a fact with raw data to back it up.
The tail rotor on the DCS UH-1H is implemented wrong.

Edited February 23, 2023 by Tim_Fragmagnet

[DishDoggie]

Wow so if I made you mad I am sorry and I can be wrong but I think the Creator of this Computer Huey combined parts of many years of the making of the Huey to make a general version of the Huey not a absolute this year only version. You have a lot of good intelligent points and I hope you understand I didn't want to insult you but to just debate the issue of the post. with a opinion I have on the subject. It is okay if you feel my opinion sucks. I enjoyed the debate. Good Day. 

[Tim_Fragmagnet]

here's a photo of the huey's tail rotor blades pitched in the nose right direction.

 


With the knowledge that our huey has been producing far too much torque due to needing too much power, this issue will hopefully gets fixed alongside that one, otherwise our pedals are going to be in very strange positions in flight.

Edited April 13, 2023 by Tim_Fragmagnet

[FusRoPotato]

Nice work Tim, I can appreciate a keen eye for flight model abnormalities. 

I've been getting into DCS lately flying some of these choppers and they all seem to have strange behaviors when it comes to torques, moments due to velocity (on all axis), stability, and vrs. When I go in and dig through some of their files, I often find what can only be described as a careless butchering of invented numbers. "FalseTailArea"??? Makes no sense to me.

I just tried out this module and the Mi8 recently after going through the Ka-50 a few months back. At first I couldn't tell if the yaw moments were just off, weak, or what, but I did notice that all of these choppers have a very strong yaw stability that increases with speed, nearly nullifying most yaw input so long as there's just 10 or 20 m/s forward speed.

Once they fix (if they fix) the power and tail issues you describe, I suspect you'll find it doesn't end there.

[Tim_Fragmagnet]

Further research has found that the tail rotor on the DCS huey rotates too fast.

At 324rpm on the main rotor, the real huey's tail rotor should have an RPM of 1,655.070084
More specifically the real version of our huey has a tail rotor to main rotor gear ratio of 5.108241:1

The DCS huey by the same metric has a gear ratio of 5.5:1
A tail rotor RPM of 1,782 at 324rpm on the main rotor.

 

You can test this yourself by watching the huey's rotors at a low RPM from an external view

 

 

From page 41 of this document, a performance profiling of our exact variant of huey.
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Edited April 11, 2023 by Tim_Fragmagnet