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Degraded Su-27 aerodynamic lift


Maverick Su-35S

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Hello,

 

After some update (don't know in which one), changes have been made to both the F-15 and Su-27 in terms of aerodynamic simulation (lift capabilities being easier to spot).

 

Initially (after the PFM came out), both the F-15 and Su-27 were capable of achieving quite authentic turn rates compared to the real planes (of course, depending on IAS and weight). The F-15 only had some critical AoA handicap (initially, now is better) as the plane's lateral-directional control was almost impossible to attain above 20 AoA (30 on the F-15's in cockpit indexer), while the Su-27 was worked quite well from the start in this area.

 

For whatever reason, after later updates (didn't stand to test aerodynamic parameters after each update) the Su-27's wings produce a quite lower lift for a given AoA (lower lift slope) while the F-15 does exactly the opposite.

 

Now, (a bit absurd one will find it), the F-15 turns better than the Flanker at both low (full aft stick full AB) and high speeds (around the best turn corner). For short, with both planes fueled the same (30% fuel), the F-15 completes the fastest (full aft stick from around corner speed) 360 turn in about 14.4 seconds, while the Flanker in no less than 15.8. How did this happen?

 

Here is a track and some output data from it:

 

Su-27 turns badly after latest updates.trk

 

1764564104_F-15liftingperformance(turningcapabilities).thumb.jpg.b156e2e37ff81d1611857bcbb2426a11.jpg

 

1460747302_Su-27liftingperformance(turningcapabilities).thumb.jpg.410c4b0813f1269e232e01cc2d955945.jpg

 

And here's a video of the Su-27's proven turning capabilities:

 

Aerodynamic modelers, can you please tell us what's going on?

 

Kind regards!


Edited by Maverick Su-35S
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When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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Haven't noticed any loss in performance myself except that temperature now has an effect on available thrust at lower altitudes. But this should effect on the F-15 similarly. Then again I also haven't been specifically testing for anything either.

YouTube Channel: https://www.youtube.com/channel/UCU1...CR6IZ7crfdZxDg

 

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Your graph shows quite impressive lift for Su-27.(24deg/s at 550km/h)

Try to use Stick Deflection Limiter Override( Y is default).

Su-27's FLCS only allows very slow onset G so there may be problem.


Edited by opps
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only red air that ever worked well for me was mig29.

 

su family all flamed out with nose down attitude, very nose heavy aircraft, into inverted flat spin death. also had problems with wings ripping off and rear stabs dying when a little rudder applied.

 

Shes made of glass, or I need more practice, maybe a bit of both. its interesting to see your graphs. the flanker should crank the eagle in comparison, but I can't say if its slow or fast contrasting IRL.

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only red air that ever worked well for me was mig29.

 

su family all flamed out with nose down attitude, very nose heavy aircraft, into inverted flat spin death. also had problems with wings ripping off and rear stabs dying when a little rudder applied.

 

Shes made of glass, or I need more practice, maybe a bit of both. its interesting to see your graphs. the flanker should crank the eagle in comparison, but I can't say if its slow or fast contrasting IRL.

 

Right control + enter and a lot of trim change in pitch/AOA changes.

 

As for cranking Eagles...Think combat configurations. :smilewink:

Lord of Salt

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Your graph shows quite impressive lift for Su-27.(24deg/s at 550km/h)

Try to use Stick Deflection Limiter Override( Y is default).

Su-27's FLCS only allows very slow onset G so there may be problem.

 

I know what you are talking about with the G limitation, but this is not the problem. If people still can't see the difference between the initial PFM and the latest updates, I have to detail things a bit more thorough.

 

24deg/s at 550km/h with 30% fuel is impressive? Then what do you say about the F-15, did you look at it? Sorry, but you prove to not know how these values are in reality.

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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only red air that ever worked well for me was mig29.

 

su family all flamed out with nose down attitude, very nose heavy aircraft, into inverted flat spin death. also had problems with wings ripping off and rear stabs dying when a little rudder applied.

 

Shes made of glass, or I need more practice, maybe a bit of both. its interesting to see your graphs. the flanker should crank the eagle in comparison, but I can't say if its slow or fast contrasting IRL.

 

Su-27/33s don't flame out cause of attitude angles, if this is what by mistake you refer to, but below a given G-load, no matter the plane's orientation from the Earth. Nose heavy? Just the opposite. If it would be nose heavy then it couldn't reach high angles of attack, maybe not even reach the critical AoA (less to say the supercritical). Sorry, don't look bad at me, but you have to learn / understand a bit of flight dynamics. The plane's CG (center of gravity) seems realistic where it is, the only problem that comes on when you push the stick until reaching an AoA below -20 is that the elevators become shadowed (turbulent and inefficient airflow) by the wing due to the relative position between the wing and elevators in the plane's vertical plane. The way to get out of the negative deep stall is quite simple, but you need a bit of altitude (at least 2000 meters). Set the controls to direct pitch (needed for high alpha or cobra), fully pull the stick and wait until the AoA goes as much negative as it can get, then release it to neutral once the AoA wants to reduce. If the AoA managed to get below -20, pull the stick and get out of this unstable region. If not, repeat the process..., full stick pull until the AoA reaches a maximum negative value, then release until it drops to below -20.

 

On the other hand, yes, the Flanker won against the Eagle in real tests and beat it in turns. The Eagle had an impossible chance to stay or get behind the Flanker. Now (after latest updates) in DCS we see the opposite, so we need a fix.

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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Right control + enter and a lot of trim change in pitch/AOA changes.

 

As for cranking Eagles...Think combat configurations. :smilewink:

 

Very good pointing! Yes, think combat configuration..., it still beats the Eagle in turns if both have dogfight missiles left (usually those are the missiles they remain with).

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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Why 30%?

 

Is that what the real charts are for (obviously, the ones available!)? Haven't looked at the Flanker charts in a while...

 

Because that is usually the maximum amount of fuel the airshow planes remain with when starting this manoeuver. I might be wrong about the exact amount left when they do this, so ask a real airshow fighter pilot for this info if you have the possibility.

 

And because of this quantity as a benchmark for having the Flanker being able to do a 360 in 12 seconds (no other fighter can do this), I also used it in the sim (game at the moment) for a better comparison.

 

Regards!

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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One might want to take a look at this as I'm bothered talking in the name of truth!

 

At page 28 you can read the following:

 

"Alleged results of so called simulated combat between Su-27 and F-15 during the

Su-27’s visit to U.S. were not serious because the Sukhoi even without afterburner, not

exceeding 18 º α, succeeded to outmaneuver F-15." Sometimes, the word "alleged" is used on purpose by some who don't accept the truth.

 

 

Regards!


Edited by Maverick Su-35S
  • Like 1

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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Although inconvenient, showing turn performance test data from 1.5 would show that it has indeed changed in 2.5

 

Made me curious, are the changes in a temporary wrong direction? Nothing new! What's important are the long term corrections!

 

Regards!

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model simulation advisor!

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Made me curious, are the changes in a temporary wrong direction? Nothing new! What's important are the long term corrections!

 

Regards!

 

I thought the point you were trying to make is that turn performance is significantly worse in the latest update. Maybe I’m misunderstanding.

 

Just to clarify, stick deflection limiter override (Y key) mentioned by opps is not a button in real life but enabled when applying >34lbs (15kgf) of backpressure on the stick. Also, I think you’re misunderstanding it’s function, it isn’t simply a G limiter. While held it allows the aircrafts normal 26 deg AoA limit to be exceeded.

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I just found out that Eagle bleeds energy way quicker now. Which should be realistic as RL buffeting occurs at high transonic speeds in max G turn limiting laminar turn. Eagle pilots are not happy about that but Flanker guys had much worse problem in wing rips and Eagle OPd so they'll have to adopt.

 

Flanker has one issue remaining still and that is inverted flat spin entry and recovery. Engines are dead in secs and hyd power too so there's no way to deflect control surfaces at all to recover. Is there a backup system or negative G tank in Flanker? On the other hand, when turning off FCS and if not trimmed up (trim limit is not sufficient for high transonic stabilization so manual work is only solution which is hard to believe to be RL feature) plane goes in instant flat spin and pilots blackouts. Next, pilot is unconscious all the way to the ground even plane is stable inverted in free fall. That is hard to believe to be truth.

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I know what you are talking about with the G limitation, but this is not the problem. If people still can't see the difference between the initial PFM and the latest updates, I have to detail things a bit more thorough.

 

24deg/s at 550km/h with 30% fuel is impressive? Then what do you say about the F-15, did you look at it? Sorry, but you prove to not know how these values are in reality.

 

Sorry completely misunderstood graph.

But Stick Deflection Limiter is key.

 

Simple math gives that F-15 pulling 10.75G at 750km/h and your track shows around 10.9G. Su-27 doing about 8G due to FLCS limiting G, Not LIFT limitation.

While one aircraft clearly pulling OverG, you bring another FBW controlled aircraft and complain about you cannot pull OverG is not just fair.

I hope you just try Stick Deflection Override and draw graph again. You will see.


Edited by opps
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I just found out that Eagle bleeds energy way quicker now. Which should be realistic as RL buffeting occurs at high transonic speeds in max G turn limiting laminar turn. Eagle pilots are not happy about that but Flanker guys had much worse problem in wing rips and Eagle OPd so they'll have to adopt.

 

Flanker has one issue remaining still and that is inverted flat spin entry and recovery. Engines are dead in secs and hyd power too so there's no way to deflect control surfaces at all to recover. Is there a backup system or negative G tank in Flanker? On the other hand, when turning off FCS and if not trimmed up (trim limit is not sufficient for high transonic stabilization so manual work is only solution which is hard to believe to be RL feature) plane goes in instant flat spin and pilots blackouts. Next, pilot is unconscious all the way to the ground even plane is stable inverted in free fall. That is hard to believe to be truth.

 

As far as I’m aware no changes were made to the F-15 or Su-27 flight models for 2.5.

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I normally don't like being mean to you, but since you attempted to do science and did it (wrong) on the internet, I will ;)

 

-10 worthless comparison.

You are attempting to talk about comparative performance as a way of judging a specific aircraft's performance.

Bzzzzt wrong. Compare it to it's own documents, period. 'The other plane out turns it now' isn't even going to be looked at. Compare flanker to flanker data, eagle to eagle data, and if something's wrong there, it will be looked at.

 

There's nothing absurd about an eagle turning insanely well at slow speed. You don't have to like it ... it's just that at such incredibly low fuel levels, you get such great turn-around time that it might be hard to beat it with a heavier airframe.

 

Also, you're comparing ITR which is very dynamic - again, -10.

 

Using articles instead of data to prove your point. -10.

 

I get where you're coming from but you're doing this very wrong and -ve points are adding up, man ;)

 

To be clear, I'll make the point again:

Compare the aircraft to their own data or no one will even bother looking at this with respect to FM inaccuracy.

 

PS: If you believe that the eagle can't out-turn a flanker in a dynamic situation, I have bridges to sell you.

 

Now, (a bit absurd one will find it), the F-15 turns better than the Flanker at both low (full aft stick full AB) and high speeds (around the best turn corner). For short, with both planes fueled the same (30% fuel), the F-15 completes the fastest (full aft stick from around corner speed) 360 turn in about 14.4 seconds, while the Flanker in no less than 15.8. How did this happen?

Edited by GGTharos

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With all the respect to everybody here.. I haven't seen any simulated professional grade CFD studies committed by either ED or FC that will give even rough level comparison between all high performance fighters in aspects of AoA vs Drag or Mach vs Drag SA charts from clean to fully loaded up to landing configurations. None. That data charts must fit into pilot's manual charts available with certain error margin that has to be same for all models tested. Why? Because that data would give ED or everyone included in module development credibility for all the work done here. It would also stop talks about who's favorite plane is better in this or that aspect of combat turns and everybody would go play instead of complaining here about mostly personal observation confronting their understanding of flight dynamics.

 

I can do that evaluation but someone from ED or FD needs to PM me, set price, sign NDA, send 3d models, get charts and verification and enjoy the silence of sheep here on forum and get credibility for work done even beyond gaming industry. It doesn't have to be me but any professional in field. That's the missing link here.

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My (educated) guess is that they have access to aircraft data documentation and resources that we don't have, they're not permitted to share it, and they don't need any CFD study.

 

I can do that evaluation but someone from ED or FD needs to PM me, set price, sign NDA, send 3d models, get charts and verification and enjoy the silence of sheep here on forum and get credibility for work done even beyond gaming industry. It doesn't have to be me but any professional in field. That's the missing link here.

[sIGPIC][/sIGPIC]

Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

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PS: If you believe that the Flanker can't out-turn an Eagle in a dynamic situation, I have bridges to sell you.

 

There, fixed. :D

 

GGTharos, I do consider your educated and knowledged posts in several matters.

 

However, not few times one can't fail to notice the usual trend against the Russian Aircraft technical capabilities by many members ; for example, in the past it was the F-16 vs MiG-29 turning capabilities, etc.

 

Practically in every air warfare site in the web, the dogfighting capabilities of the Flanker are highly praised, when the ones of the Eagle are not so much... so I really doubt the Eagle (with all its other superior aspects) could "out-turn" a Flanker with that ease.

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Fair.

 

I'm not saying the Flanker is inferior to the Eagle in BFM, what I am saying is that the way we discuss BFM is inferior to ... actual BFM.

 

So, getting to your second paragraph, we (me included) always considered the Flanker to be utterly superior in WVR. There are many reasons for this: On paper (And in reality, since the paper is made by gathering data from said aircraft) the Flanker has excellent ITR/STR capability. The R-73 gives it another tool in the shed which forces peeps to go into a 1C unless they can get into a 2C with a huge advantage.

 

Thus naturally, the Flanker does have a lot of WVR advantages, but it's not utterly superior like we all used to assume. The Eagle has things going for it that you can't ignore, and some of this stuff is due to the silly way that people do these comparisons. You can confidently over-g a 30% fueled Eagle to 10-11g at the assumed speeds at low altitude and get a higher average turn rate than the Flanker because you just can't do it with that huge air-frame.

 

Does that mean that you can 'easily' out-turn a Flanker? No. But it does mean you can easily out-turn every lay-man out there who's either hauling butt at 500-600kts in the merge or doing the stick-to-the-gut maneuver and running themselves so low on airspeed that even a mildly patient and knowledgeable Eagle pilot can out-rate by keeping better maneuvering speed that he can bleed for a shot or just cut up the TC in the vertical. All this means that you need to pure more thought into your BFM than just the belief that a Flanker is utterly superior in WVR. It's not.

 

So once more, if people believe that Eagles can't out-turn Flankers, there are bridges to be sold and I'm charging a fair price :D

 

It's funny how opinions on the web are just repetitions of themselves without any thought or science put behind them, right?

 

PS: The main point here is that 'The Eagle out-turns the Flanker' is not a valid complaint or bug report. If it's suspicious, then you look at both aircraft and prove that they don't behave like they ought to - one or both of them. That is the valid format of showing that a bug exists. Given how many times these aircraft have been tested to match their FM, you might be hard-pressed to find such a problem by now. I actually put in a bug report about the Flanker turning harder than it ought to - and I had to eat my hat so to speak when I actually tested the FM against the Flanker's data and found that yes, it does indeed turn like this! (I was suspicious because the turn rate graph shape looked strange to me).

 

However, not few times one can't fail to notice the usual trend against the Russian Aircraft technical capabilities by many members ; for example, in the past it was the F-16 vs MiG-29 turning capabilities, etc.

 

Practically in every air warfare site in the web, the dogfighting capabilities of the Flanker are highly praised, when the ones of the Eagle are not so much... so I really doubt the Eagle (with all its other superior aspects) could "out-turn" a Flanker with that ease.


Edited by GGTharos

[sIGPIC][/sIGPIC]

Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

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One might want to take a look at this as I'm bothered talking in the name of truth!

 

At page 28 you can read the following:

 

"Alleged results of so called simulated combat between Su-27 and F-15 during the

Su-27’s visit to U.S. were not serious because the Sukhoi even without afterburner, not

exceeding 18 º α, succeeded to outmaneuver F-15." Sometimes, the word "alleged" is used on purpose by some who don't accept the truth.

 

 

Regards!

 

That is fairly difficult to believe. Because while I dream that Su-27 is a highly maneuverable aircraft and better than anything that F- series offers, just by claims like these:

Although that is about Mig-29, but still. https://dunsfoldairfield.org/john-farley-afc-obe/ As I still believe that F/A-18C will outmaneuver Su-27 or Mig-29 in optimal setups for both, but still needs to run for its money.

 

 

One thing that as well interest me, is that isn't it unfair to use a percentage of fuel capacity, instead use the fuel that would give the same range in specific altitude or altitude+time?

 

Like how much fuel it would be required for a fighter to fly 300km, loiter 5min and then fly back? And then perform the flight maneuvering tests at that begin of the loiter?

 

As I find it just wrong that it is used like 30% or 50% of fuel capacity for both, when other can fly 1500km with that and other just 600km? As if one wants to get the best maneuvering, shouldn't it just be then used almost empty regardless that no one would be in real combat situation with such setup?

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