Degraded Su-27 aerodynamic lift

[Mars Exulte]

11 hours ago, Maverick Su-35S said:

Yes, I'm quick to counter 

I wouldn't exactly call four years quick, but I now believe you really are some sort of project lead or middle manager with this kind of time management.

11 hours ago, Guppy said:

**Wall of text crits you for 9000**

**Dead**

Looks like you struck a nerve with that one. I can already sense Nineline and Bignewy closing in.

Edited November 1, 2022 by Mars Exulte

[Guppy]

Look... If you are expecting a game to be 100% to real life you are setting yourself up for failure. ED never has claimed these modules are 100% accurate; they've said they are the best recreations of these fighters using the data they have. That's not 100%. Further, like all software and development activities there is a point of diminishing returns... you can spend millions making something as close to perfect, as possible, or be happy with 90%. A recreation in a digital universe can never be 100% accurate in all aspects to real life; it's not possible, at least with tech today.

Additionally, posting youtube videos is not a definitive resource. How much fuel does the jet have? What were the weather/atmospheric conditions? How fast was the wind? Was there wind? Was the pilot flying into the wind to create lift in certain aspects? There are so many unknowns.

My observations over the years is that typically Maverick posts when he got shot down on some server by an F-15 driver and he comes on to these forums fuming because he did not win. I've seen it here, I've seen it on discord, it's absurd. So absurd that he necro posts to go on a soliloquy.

Until ED makes his '27 absolute perfection he's going to continue to go on these rants about how "under powered" the '27 is and how uber the 15 is.

 

[jackmckay]

Wooow. The bad kinetics conversation is back. OMG. Maverick is resurrected! Thank you buddy for kudos. Kudos goes back.

 

 

 

Edited April 13, 2024 by jackmckay

[Mars Exulte]

On 11/2/2022 at 8:02 PM, jackmckay said:

Let me tell you a bit about my background. I studied three collogues, Air Traffic, Mech engineering and IT. Quit all before finals. Why? Cos I felt I'm on wrong places, many materials were outdated and I somehow too often managed to outperform my professors.

 

 

 

 Big Gecko45 vibes from this guy.

Edited November 5, 2022 by Mars Exulte

[MiG21bisFishbedL]

1 hour ago, Mars Exulte said:

 Big Gecko45 vibes from this guy.

 

At least the IT part is believable.

[jackmckay]

Question everything boyz. I might be a big mouth liar though? Nothing on topic? No critics, comments, suggestions? Only raw helpless personal tagging. I'm sad, lonely and disappointed.

 

[jackmckay]

Let me get this straight. DCS might have right reference charts, and performance numbers might also match those charts, except in one little important thing - time to chart spot aka acceleration and deceleration intervals. And that data sniping is a damn BIG deal. If set wrong, it will make quarter mile run 1000HP car inferior to 500HP car at near equal weight.
Core issue. Tnx.

[Top Jockey]

4 hours ago, jackmckay said:

Question everything boyz. I might be a big mouth liar though? Nothing on topic? No critics, comments, suggestions? Only raw helpless personal tagging. I'm sad, lonely and disappointed.

 

 

What for, so they delete one's posts like in the F-16 forum ?

Just a waste of time.

[Mars Exulte]

3 hours ago, Top Jockey said:

 

What for, so they delete one's posts like in the F-16 forum ?

Just a waste of time.

 

[Top Jockey]

By the way, would anyone know the: total lifting area of the Su-27 ?

I've been searching through the web, but so far no avail.

Thank you.

[Pavlin_33]

On 4/9/2023 at 7:10 PM, Top Jockey said:

By the way, would anyone know the: total lifting area of the Su-27 ?

I've been searching through the web, but so far no avail.

Thank you.

Looks like the wing area is 62m² - https://www.digitalcombatsimulator.com/upload/iblock/ed7/Su-27 DCS Flaming Cliffs Flight Manual EN.pdf, [10]
No idea about the rest :(.

[HwyStar]

An extension is available for both Google and Brave browsers that allows the ChatGPT response to be displayed simultaneously with Google's reply, making it a useful tool to have for queries like this.

Me: Total lifting area of the Su-27

ChatGPT: I'm sorry, but I cannot provide the total lifting area of the Su-27 as it is not a well-defined term in aircraft design.

However, the Su-27 is a Russian fighter jet that was designed and built by Sukhoi. It has a wingspan of 14.7 meters (48.2 feet) and a wing area of 62 square meters (667 square feet). The specific lifting area of an aircraft can vary depending on the design and configuration of the wings, and is typically measured in square meters or square feet.

 

[Top Jockey]

Thank you for your time people!

I know that some specific data on jets isn't always easy to find.

My motive to try knowing this stuff is related to have a rough idea of some jets aerodynamic capabilities.

 

Yep, wing area is easily available at wikipedia, but overall / total lift area / surface / etc. might not be that easy.

But it is know for some jets, i.e. the MiG-29:

- total lift area: 60,9  (square meters)

- wing area: 38  (square meters)

 

Thank you eitherway!

[F-2]

Paper by Su-27 designer with some useful info for calculating aero performance 

Fo.pdf

[BBCRF3]

В 23.04.2023 в 18:32, F-2 сказал:

Статья конструктора Су-27 с некоторой полезной информацией для расчета аэродинамических характеристик

Fo.pdf 193.37 \u043a\u0411 · 36 загрузок

nothing significant. And then the data is not correct

[DummyCatz]

On 10/31/2022 at 7:34 AM, F-2 said:

I have this if it’s helpful. I think everyone else found inner peace and moved on with their lives.

TsAGI SU27???????.pdf 2.24 MB · 60 downloads

While waiting for the recent review and rework for both the flight performance of F-16 and F-18, I think I'll give the Su-27 a late shot.

In Su-27, m * Ny max = const = 171000kg for M < 0.85. So the weight for Ny max = 8.5g from those TsAGI turn rate charts would be 171000 / 8.5 = 20118 kg.

This would clarify the aircraft weight in those charts from the TsAGI document.

 

[DummyCatz]

I've completed my testing at 200m and 5000m, standard day (15°C at sea level) with 20% Fuel and 2*R-73 + 2*R-27, so that aircraft weight is around 20000 kg.

1. 200m ITR: above 30deg, checks with TsAGI 200m ITR curve.

 

2. 200m STR: 8.4g at around 21 deg/s, checks with 200m STR curve.

 

3. 5000m STR: 6.6g at around 14 deg/s, checks with 5000m STR curve.

 

So looks like it agrees with the TsAGI chart rather than the Su-27SK manual. For example, 5000m sustained Ny is ~7.5g (hits the g-limit) in the manual compared to 6.6g in TsAGI chart and in DCS.

As to why ED chose the data from TsAGI instead of the manual is unknown to me.

[NineLine]

4 hours ago, DummyCatz said:

I've completed my testing at 200m and 5000m, standard day (15°C at sea level) with 20% Fuel and 2*R-73 + 2*R-27, so that aircraft weight is around 20000 kg.

1. 200m ITR: above 30deg, checks with TsAGI 200m ITR curve.

 

2. 200m STR: 8.4g at around 21 deg/s, checks with 200m STR curve.

 

3. 5000m STR: 6.6g at around 14 deg/s, checks with 5000m STR curve.

 

So looks like it agrees with the TsAGI chart rather than the Su-27SK manual. For example, 5000m sustained Ny is ~7.5g (hits the g-limit) in the manual compared to 6.6g in TsAGI chart and in DCS.

As to why ED chose the data from TsAGI instead of the manual is unknown to me.

Your assessment of the data we used is not correct, we did not use this as a source but we are also unable to share our sources. As well, you should be careful leaning too hard on Tacview, while it is a good tool to feed speculation, it is not necessarily valid for diagnosis. 

[AeriaGloria]

6 hours ago, DummyCatz said:

I've completed my testing at 200m and 5000m, standard day (15°C at sea level) with 20% Fuel and 2*R-73 + 2*R-27, so that aircraft weight is around 20000 kg.

1. 200m ITR: above 30deg, checks with TsAGI 200m ITR curve.

 

2. 200m STR: 8.4g at around 21 deg/s, checks with 200m STR curve.

 

3. 5000m STR: 6.6g at around 14 deg/s, checks with 5000m STR curve.

 

So looks like it agrees with the TsAGI chart rather than the Su-27SK manual. For example, 5000m sustained Ny is ~7.5g (hits the g-limit) in the manual compared to 6.6g in TsAGI chart and in DCS.

As to why ED chose the data from TsAGI instead of the manual is unknown to me.

Su-27SK is 570 kg heavier in empty weight then Su-27S due to reinforcement of landing gear and structure for higher takeoff and payload weight. So I would assume the Su-27SK manual turn performance to be slightly lower then what we would of expect from an “ideal” Su-27S flight model 

[DummyCatz]

2 hours ago, NineLine said:

Your assessment of the data we used is not correct, we did not use this as a source but we are also unable to share our sources. As well, you should be careful leaning too hard on Tacview, while it is a good tool to feed speculation, it is not necessarily valid for diagnosis. 

Well the only tool I’m leaning on is the Info Bar (ctrl+y), in which TAS and G are checked against the chart. Tacview was only for illustration purposes in this post. But thanks for mentioning that.

And it doesn’t change the testing result and the fact that DCS agrees more with TsAGI data than the manual.

28 minutes ago, AeriaGloria said:

Su-27SK is 570 kg heavier in empty weight then Su-27S due to reinforcement of landing gear and structure for higher takeoff and payload weight. So I would assume the Su-27SK manual turn performance to be slightly lower then what we would of expect from an “ideal” Su-27S flight model 

Yes but be aware that the manual chart is for a fixed gross weight of 20000kg too, so empty weight wouldn’t matter. Same for F-16CJ charts being checked against our CM.

[Xhonas]

3 hours ago, NineLine said:

 

we did not use this as a source but we are also unable to share our sources. 

Hi, excuse me for asking, but this is very weird. Aren't DCS modules supposed to be based on public available, verifiable information? Are you using any kind of classified / restricted information that the public can't access to model the Su27? Because if that is the case... How much of DCS is allowed to be modelled after restricted info? a little bit off topic, but Heatblur also said that they are using restricted information to model the Phoenix. What is up with this trend? i'm confused. 

[NineLine]

1 hour ago, Xhonas said:

Hi, excuse me for asking, but this is very weird. Aren't DCS modules supposed to be based on public available, verifiable information? Are you using any kind of classified / restricted information that the public can't access to model the Su27? Because if that is the case... How much of DCS is allowed to be modelled after restricted info? a little bit off topic, but Heatblur also said that they are using restricted information to model the Phoenix. What is up with this trend? i'm confused. 

Yes, we use legally sourced documents, that does not mean that we can share or reference them. We do not just look at the internet for sources. 

3 hours ago, DummyCatz said:

And it doesn’t change the testing result and the fact that DCS agrees more with TsAGI data than the manual.

And that fact means nothing as neither of those sources was used according to our dev team, thanks. 

[DummyCatz]

3 minutes ago, NineLine said:

And that fact means nothing as neither of those sources was used according to our dev team, thanks. 

So unverifiable. Thanks for confirming.

[DummyCatz]

Nevertheless, I can use another source and method to calculate the instantaneous performance, using the wind tunnel and flight tested Cz data, obtained by TsAGI performing a Cobra maneuver, from Figure 6 of https://arc.aiaa.org/doi/10.2514/6.1993-4737

Some basic equations:

Total Normal Force = 0.5 * ρ * V^2 * Sref * Cz

Nz (normal load factor, or Ny in Russian convention) = Total Normal Force / Weight

 

Note: Cz is not the same as CL in that Cz = - CL * cos(AOA) - CD * sin(AOA).

Now dial in the data:

Sref = 62m^2

ρ = 1.225 kg/m^3 at sea level, standard day, for example

V = 350 km/h = 97.2 m/s, at sea level for example

Weight = 20000 kg = 196200 N, for example

Cz = -2.0 at 60 deg AOA if only considering steady wind tunnel tests and not considering dynamic pitch rate effects like Cz_q. (See flight test curves)

 

So the resulting normal force = 0.5 × 1.225 × 97.2 × 97.2 × 62 × 2.0 = 717563 N

And Nz (russian Ny) = 717563 / 196200 = 3.66g, at 350km/h + 60 deg AOA + sea level, which should be the bare minimum as we're only considering steady flows. Now you're good to perform a Cobra to test it out.

Edited December 17, 2024 by DummyCatz

[Skuva]

I know of a famous big developer studio on the combat flight game genre, which also claim they develop vehicles based on non publicly available (but legal) documentation, and in their case it has been proven to be just an excuse to model it however they like. I hope this isn't the case for ED.