New D-9 FM since 2.0?

[Solty]

@Humming

 

Isn't NACA 66 airfoil of P-51H? Not P-51D? You know that we have P-51D right?:huh:

Edited December 19, 2015 by Solty

[Hummingbird]

@Humming

 

Isn't NACA 66 airfoil of P-51H? Not P-51D? You know that we have P-51D right?:huh:

 

Drag bucket is the same for both and most laminar flow airfoils, there's no difference. It's simply how they behave due to their shape with a sharp leading edge and max thickness being at around 60% chord length.

 

 

This shape is great for straight and level flight but worse for flight at high AoA's. Only way to remedy this is by use of LE devices.

[Crumpp]

I don’t want to put words in Yo-Yo’s mouth but, what he’s seems to be saying is that the linear equations Crumps charts are based do not accurately predict lift coefficients at high angles off attack. the NACA came to this conclusion around 1947 while testing swept wings. Even ignoring other factors not taken into account by Crumps model, propeller effects, etc, the margin of error in his methodology is so great that it renders the predictive and comparative power of the equation moot in high alpha conditions.

 

Perkins and Hage is fine for most circumstances, but in the case being examined here a different approach is needed. The NACA, then NASA ran into similar issues as the performance of aircraft increased. Equations were no longer predicting experimental data. To reconcile this new methodologies were adapted, including Panel and Vortex Lattice methods.

 

Even if such methodologies were adapted to predict CL, CD, etc in Crump’s model. The predictive power of the model would be doubtful because it needs to take in to account, the variability of propeller efficiency and propeller downwash effects.

 

My interpretation of Yo Yo’s statements are, that there are limitations to the methodology used which say the flight model is wrong. The current test case exceeds the limitations of Crumps modeling and the more advanced modeling used in the sim would be a more accurate predictor of reality. Thus the 190 will stay the same until someone comes up with a proof or more accurate model which shows the current implementation is wrong.

 

 

Section lift curves are not linear particularly at high angles of attack and analytical solutions are not feasible.

 

Links to info on Vortex Lattice Method

http://www.dept.aoe.vt.edu/~mason/Mason_f/CAtxtChap6.pdf

http://www-mdp.eng.cam.ac.uk/web/library/enginfo/aerothermal_dvd_only/aero/vlm/vlm.html

 

I just read the NACA paper you posted. I definitely do not think Yo-Yo is making the claim you believe based off this evidence.

 

The induced angle of attack changes are the topic and the error that exists between linear and non-linear equations.

 

Induced angle of sttack effects the body angle and has absolutely nothing to do with turn performance.

[Crumpp]

Drag bucket is the same for both and most laminar flow airfoils, there's no difference. It's simply how they behave due to their shape with a sharp leading edge and max thickness being at around 60% chord length.

 

 

This shape is great for straight and level flight but worse for flight at high AoA's. Only way to remedy this is by use of LE devices.

 

The basic characteristic of laminar flow being a low angle of attack event is a characteristic of all laminar flow airfoils. A discussion of laminar flow at high angles of attack or any effect at all on turn performance is a waste of time.

[VO101_MMaister]

I don`t have the 2.0, but for me it looks like this topic went a bit off from the original question.

 

Is it approved by proper tests that the FM changed in 2.0 compared to 1.2 or not?

 

If it didn`t change then you guys are questioning the original D9 FM, and it is another topic.

 

If it did change then the question is why and how did it change? Was it intentional or not? If it is an intentional change then what is the reason of it? If it is not, then how can it be recovered to the original?

 

I think you should concentrate on these questions.

 

MM

[Crumpp]

If it didn`t change then you guys are questioning the original D9 FM, and it is another topic.

 

If it did change then the question is why and how did it change? Was it intentional or not? If it is an intentional change then what is the reason of it? If it is not, then how can it be recovered to the original?

 

The original FM is not being questioned. That agreed with standard performance estimates.

 

It appears that the propeller efficincy and effective angle of attack have changed in the FM. In order for the propeller efficiency to absorb the 450 hp advantage of the Dora, the P-51's propeller must be 15% or more greater power transfer.

 

It is highly unlikely that would not have been caught in testing are would represent a significant departure from normal propeller engineering.

 

The second point seems to be an issue with the effective angle of attack of the polar. In very low aspect ratio wings, this is correct assumption. Unlike the jets found in most of DCS, however, the high aspect ratio designs of World War II it is insignificant. For Aspect Ratio's above 3, the 2D is very applicable and is industry standard.

 

To get a perfomance estimate our method must change based on Aspect Ratio of the wing.

 

Our formula for Angle of Attack for High Aspect Ratio Wings then becomes:

 

Angle of Attack = 2D Polar Angle of Attack + Induced Angle of Attack

 

For a 3D wing with an Aspect Ratio of 3 or Less, that model breaks down and our methodolgy changes to a better approximation becomes:

 

Angle of Attack = Effective Angle of Attack + Induced Angle of Attack.

 

Effective Angle of Attack is calculated thru the section 2D using formulation designed for a LOW ASPECT RATIO wing.

 

Here is a fairly easy to understand lecture from Stanfords Engineering Department. Page 40 Figure two nicely illustrates why wings are divided into low aspect ratio and high aspect ratios for calculating performance. Two different methods are required and they are not to be confused!

 

 

 

[ame]http://adl.stanford.edu/aa200/lecture_notes_files/lecture11_1.pdf[/ame]

 

 

Think about it, for the Dora to suddenly loose 450 hp in a turn...... it would be immediately noticed by the pilot and picked up by standard data recording instrumentation of the day.

[NineLine]

I don`t have the 2.0, but for me it looks like this topic went a bit off from the original question.

 

Is it approved by proper tests that the FM changed in 2.0 compared to 1.2 or not?

 

If it didn`t change then you guys are questioning the original D9 FM, and it is another topic.

 

If it did change then the question is why and how did it change? Was it intentional or not? If it is an intentional change then what is the reason of it? If it is not, then how can it be recovered to the original?

 

I think you should concentrate on these questions.

 

MM

 

No, not that I know of, no one has showed comparative vids or data between 2.0/1.5/1.2. So mostly its feelings and impressions that it has drastically changed somehow.

 

Yo-Yo has stated that nothing changed in the FM.

[Nedum]

Please wait a second!

There were vids and if I can outturn a P51D in 1.2.6 with ease and at the same height in 2.0 I can fly as long as my fuel is empty an I am not even near the six of the P51D what should a video show?

As soon as some guys a video show the next announcement was "Pilot did it wrong!", "The other pilot was better!". So I would really see a video from the guys telling us all is ok how they outturn the P51D in 2.0!

If nothing has changed than those guys can show it in no time!

I am waiting for such a vid but never saw one!

To ask the people feeling here changed something and after they showed it tell them they did it right it’s your right, but please show us how you guys did it the right way please!

At soon as I reach 3G during a turn in 2.0 my wings flip over. In 1.2.6 I can pull 4,5 Gs before this behavior starts. 1.5 Gs more. That’s a world for a plane!

The D9 has now the same ugly behaviors like the K4. But I have not one tool to show it to you the 100% right way and this is the returning point please!

Please show me that I am/my feelings are wrong!

[NineLine]

Please wait a second!

There were vids and if I can outturn a P51D in 1.2.6 with ease and at the same height in 2.0 I can fly as long as my fuel is empty an I am not even near the six of the P51D what should a video show?

As soon as some guys a video show the next announcement was "Pilot did it wrong!", "The other pilot was better!". So I would really see a video from the guys telling us all is ok how they outturn the P51D in 2.0!

If nothing has changed than those guys can show it in no time!

I am waiting for such a vid but never saw one!

To ask the people feeling here changed something and after they showed it tell them they did it right it’s your right, but please show us how you guys did it the right way please!

At soon as I reach 3G during a turn in 2.0 my wings flip over. In 1.2.6 I can pull 4,5 Gs before this behavior starts. 1.5 Gs more. That’s a world for a plane!

The D9 has now the same ugly behaviors like the K4. But I have not one tool to show it to you the 100% right way and this is the returning point please!

Please show me that I am/my feelings are wrong!

 

This is not meant as an insult, but you said you couldnt do a loop in the 109, I am not sure I cant take you word that something is wrong with the Fw 190, and again, Yo-Yo has looked into it to see if there was any changes or roll backs, and its all fine. Its not on ED to prove you guys wrong.

 

I am closing this, if and when someone comes up with something new, PM me, I can reopen or better yet, an new thread without all the excess noise maybe.

[Hummingbird]

Crumpp did a blade analysis theory check on the Dora & P-51 ingame, and it turns out that currently there's three things that possibly are wrong ingame: 1) The ingame Dora features a prop efficiency that is way lower than the real aircraft or 2) The Dora is missing a whopping 450 hp or finally 3) the ingame P-51 features a prop effiiency of 100%.

 

That's how bad it is.

 

We did several tests to prove the point and provided original documentation along the way to illustrate the problem. Sadly however nothing was done, and as I see it most likely because of a desire to artificially balance things out - That's the only thing that makes sense to me after how our concerns were treated at least. A real shame, but that's how it is

Edited March 2, 2016 by Hummingbird

[Yo-Yo]

Crumpp did a blade analysis theory on the Dora & P-51 ingame, and it turns out that currently there's three things that possibly are wrong ingame: 1) The ingame Dora features a prop efficiency that is way lower than the real aircraft or 2) The Dora is missing a whopping 450 hp or finally 3) the ingame P-51 features a prop effiiency of 100%.

 

That's how bad it is.

 

We did several tests to prove the point and provided original documentation along the way to illustrate the problem. Sadly however nothing was done, and as I see it most likely because of a desire to artificially balance things out - That's the only thing that makes sense to me after how our concerns were treated at least. A real shame, but that's how it is

 

I would be very greatful if you explain to the audience the meaning of "blade analysis theory check" you operate with....

 

And for future I beg you not to broadcasting the statements you do not understand.

[Hummingbird]

Thanks for the kind words Yo Yo.

 

Anyway Crumpp did the check, and he would've gladly answered your questions Yo Yo, but since he's banned (oddly as are most who've complained about this issue so far infact) he can't.

 

If you operate with only a 75-78% prop effeciency for the Dora and a 85-87+% efficiency for the P-51 at speeds of 350-400 km/h it is without basis in reality. As is it if its 85 vs 100.

 

It is how it is.

 

And to prevent this from going OT as Sith says its doing, people who are interested can simply read this thread: http://forums.eagle.ru/showthread.php?t=154573&page=15

Edited March 2, 2016 by Hummingbird

[Yo-Yo]

Crumpp did the check, and he would've gladly have answered your questions Yo Yo, but since he's banned he can't.

 

That you operate with only a 75-78% prop effeciency for the Dora and a 85-87+% efficiency for the P-51 at speeds of 350-400 km/h is without basis in reality.

 

It is how it is.

 

If you could read the diagrams he mentioned you would never write this statement. And what is "100% efficiency" of P-51 prop you mentioned??

 

And what about the blade? :D

[Hummingbird]

All that needed to be said was said in this thread: http://forums.eagle.ru/showthread.php?t=154573&page=15

 

I'm not going to drag this anymore OT.

[Yo-Yo]

All that needed to be said was said in this thread: http://forums.eagle.ru/showthread.php?t=154573&page=15

 

I'm not going to drag this anymore OT.

 

I did not see "blade analysis theory check" there... so I agree - you have not to drag here this stuff anymore.

[Hummingbird]

I see I forgot a word in my intial post.

 

Should've read blade element theory analysis check.

 

Hope that clearly things up - eventhough I know you understood from the beginning.

[Pilum]

 

We did several tests to prove the point and provided original documentation along the way to illustrate the problem. Sadly however nothing was done, and as I see it most likely because of a desire to artificially balance things out - That's the only thing that makes sense to me after how our concerns were treated at least. A real shame, but that's how it is

 

 

Anyway Crumpp did the check, and he would've gladly answered your questions Yo Yo, but since he's banned (oddly as are most who've complained about this issue so far infact) he can't.

 

 

 

Was not planning to post at all here since I can't see that you or Crumpp have "proved" anything but seeing the two quotes above changed my mind.

 

If we find a little red cross by your name it won’t be because you have been martyred and silenced. It will be because you continuously bring up the same subject again and again and even hint that other who have “complained” have been banned, i.e. silenced by the DCS moderators. To crown it all, you even suggest that the DCS developers have “balanced” the sim, i.e. premeditatedly doctored the performance. Both pretty serious allegation so I would not be surprised if you end up in ban-land. You make your own bed so don’t be surprised if you get to lie in it……

 

Also can’t see why you bemoan Crummp’s fate: That he is still banned is IMHO well deserved since he has been badmouthing DCS products over at the Il-2 Battle of Stalingrad forum and even put up his DCS P-51 key for sale there so I'm not loosing any sleep over that either.

Edited March 3, 2016 by Pilum

[NineLine]

Guys, lets talk facts about the 190 module and the real aircraft, lets not talk about people who have been banned or anything else not related.

 

To be clear on all this, ED isnt doing any sort of balancing, they never have, they dont have any plans to do so now.

 

The evidence shown here has been acknowledged, but nothing has been brought forward to prove anything is wrong with the FM or that anything has changed. (no matter how many times it gets brought up, that isnt going to change without some better evidence)

 

So lets try and focus. And remember, discussing admin action against users is against the rules, repeatedly bringing up the same issues that have been acknowledged is against the rules, and being mean to one another is against the rules... if we can stick to all that, everything will be fine, and I wont have to pull this car over ;)

[Anatoli-Kagari9]

I can't think that any factors affecting the modules performance are in any way related to bias / balance - this looks like complete nonsense to me.

 

What I do think is that sometimes there appears to be some lack of coordination between internal fixed items and what becomes available for the next builds of the sim, resulting in some confusion, misinterpretation of what is actually supposed to be fixed / identified as need to be fixed, or not considered as a bug / limitation.

 

I did have the sensation that some changes ( mostly for better ) sometimes occurred with them being in sync with the published list of items for a given aircraft module and release. A good example was my experience landing the P51d, my first ever DCS module, and it's huge tendency to ground loop on landing... I am almost sure it wasn't "just my practice" with the PC hardware I bought to play these simulation games at home, that made the difference, but rather that there were actually changes to the aircraft that made it a lot more plausible under / controllable under such circumstances...

[Solty]

Yeah, that kind of balancing is just wrong, and I am sure DCS is not doing so. Otherwise they would never fix the Bf109K4's speed. :P

 

Anyway, I saw a very wierd behaviour of the 190. I am not sure it is the FM or is it the game's netcode. But the stalling and snaping is so violent it almost feels like there is animation missing or the plane switches CoG... I can't explain it. But it sure does feel unnatural. I would assume the plane would stall out with such violent movments.

 

Here is the video, it is exceptionally visible at 30 sec-50 sec:

[Yo-Yo]

Yeah, that kind of balancing is just wrong, and I am sure DCS is not doing so. Otherwise they would never fix the Bf109K4's speed. :P

 

Anyway, I saw a very wierd behaviour of the 190. I am not sure it is the FM or is it the game's netcode. But the stalling and snaping is so violent it almost feels like there is animation missing or the plane switches CoG... I can't explain it. But it sure does feel unnatural. I would assume the plane would stall out with such violent movments.

 

Here is the video, it is exceptionally visible at 30 sec-50 sec:

 

It's a netcode. It's not a bug - as the MP synchronised, all positions of the net phantoms (players' aircraft flying at your computer) go from the past due to network lags, more or less, depending on the net.

So, all phantoms on your computers are extrapolated from the past. Abrupt movement like fast roll, especially snap rolls can cause these effects.

[Solty]

Ufff, thx YoYo. I hope ED can get that net code upgraded (it was somewhere down the line after 2.0 right?). Cause it is a immersion breaker. I have never seen a behaviour like that outside DCS :).

 

Thx for clarification.

Edited March 4, 2016 by Solty

[Ala13_ManOWar]

Keeping on topic. Dora is awesome :lol:. Talking about manoeuvring speeds, this is an unintentional test happening a few days ago while testing flying some DCS newbies. 11:20 You can see how Dora easily outmanoeuvres P-51 at high speed and then keeping turn looses energy to see P-51 outmanoeuvring Dora. DCS 1.5.3, I don't see a change,

 

 

S!

Edited March 4, 2016 by NineLine
fixed vid

[Solty]

Your video doesn't work, you need to take the link from "share" tab and take the only last part of the link and put it in between the YT brackets on the forum.

[Anatoli-Kagari9]

So, it's mostly due to online lag! Great to know!

 

In some occasions the lag effects are evident, that's for sure.

 

Overall I also notice a bit lower medium fps on my system with the latest 1.5.3, even having lowered the settings. Instead of a stable 60 fps I sometimes visit the high twenties.... but at the ACG Bloodandsummer/winter server, still very payable :-)

 

I miss an "instantaneous" duel / furbal server, where we can choose to respawn already airborne and ready for combat :-)