Degraded Su-27 aerodynamic lift

Not a bad idea - I would go a little further and I would ask, wouldn't you want to compare the typical expected combat setup?

You can run these comparisons in any way you want obviously. I could compare a 10% fuel eagle to a 100% fuel flanker. Or equal range, or equal time, both of which are highly subjective because they depend on how a pilot maneuvers and uses the AB (flying at higher speed uses more fuel for example, obviously using AB uses more fuel than not, and which AB stage are you using?)

All this testing is both subjective and quite vanilla, and still meaningless - what I mean by that is - the purpose of this thread was not an F-15 to Su-27 comparison, it was 'Su-27 bug because F-15 out-turns it'. There's only one way to show bugs, and that's to show that the specific aircrafts don't behave as they ought to, NOT that one out-turns the other. That's just proof that one fares better than the other under x/y circumstances.

I know what you are talking about with the G limitation, but this is not the problem...

 

24deg/s at 550km/h with 30% fuel [for the Su-27] is impressive?...

No, it's not. Had you pulled thru the AoA limiter (modeled as the "Y" key) you would have been in the 30°/sec range just before that.

Speaking of 30°/sec, that video you linked has me puzzled. It seems to suggest that the Flanker in question turned 360° in 12 seconds. If that's actually the case, then it somehow held its max instantaneous turn rate for the entire turn which seems to be a contradiction.

It's quite impressive for an STR, IH.

So not arguing one way or the other, but is this as intended? Or will it be changed again?

Should the eagle and flanker perform such as they do now?

Unless you can prove that they perform incorrectly with respect to their own data, yes, it's intended.

Unless you can prove that they perform incorrectly with respect to their own data…

So in the end, is it possible for us mere mortals ? if no, topic closed… :(

It is for a bunch of things, the data is available in public. Not everything, but enough for most uses. It is a LOT of work so personally I don't care to re-do a full test just because someone got themselves out-turned.

So in the end, is it possible for us mere mortals ? if no, topic closed… :(

Then, from my perspective, ED is giving up best argument against any doubt. Its generally matter of geometry only and geometry can be receated from outside and tested independently. Systems are mostly classified as it shoul be but geometry is visible to all. Not giving cfd validation of flight modeling is big step in direction away from calling DCS a 'simulator'. Just that simple, no certified validation, no pro market. Just game, no more no less.

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i read every post in this thread. the only way to truly get good data is by having a bit of an aerial battle. developer states always put out propaganda with words like "allegedly" or "dynamic".

It's a simulator, so it tries to be accurate- but the data is all biased and incomplete. unlike a spitfire or a bf109 or a fw190- conjecture and bias cannot be trumped with reality.

I think sukhoi will always pump the flanker, and douglas will always pump the eagle. and then you've got a video game with multiplayer mechanics somewhere in the middle. forget about it.

a skilled pilot is going to win, despite his machine. the problem in this area of conjecture is that it greatly influences the perception of skill. whats skill in games? high fps and reg?

who judges who is better, if the guy is playing in a 4th gen aircraft with a bunch of manual systems and very little help, or if its a FC3 eagle pumping and dumping salvos of aim120s?

Is it the skill of not crashing or ripping your wings off in the merge with the russian jets? so now its not even about who shoots who its about the meta of AOA and systems work. or the hijinx and hiccups of the sim.

yeah, this is called the weeds.

Then, from my perspective, ED is giving up best argument against any doubt. Its generally matter of geometry only and geometry can be receated from outside and tested independently. Systems are mostly classified as it shoul be but geometry is visible to all. Not giving cfd validation of flight modeling is big step in direction away from calling DCS a 'simulator'. Just that simple, no certified validation, no pro market. Just game, no more no less.

 

 

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and some point they need to grey area the limits of machines and balance based on a "gamesmanship" style, or at least, think about it.

To say "its a zero to one simulation" is inaccurate. they may take time to make things appear accurate but there is balancing fudging and nerfing. its not a study sim.

From my point of view, no CFD validation is required when you already have the aircraft performance data.

Then, from my perspective, ED is giving up best argument against any doubt. Its generally matter of geometry only and geometry can be receated from outside and tested independently. Systems are mostly classified as it shoul be but geometry is visible to all. Not giving cfd validation of flight modeling is big step in direction away from calling DCS a 'simulator'. Just that simple, no certified validation, no pro market. Just game, no more no less.

 

 

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If they have data, i really hope they do, then why fligh model changes from time to time? I can understand structural modelling or damage model being hidden or hard to evaluate but flight performance margins should be clearly known and clearly immitated if ed guys have them. I again hope that they have aerodynamic data available. From my perspective they are close to real but again, independent certification is quantum leap.

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Ok, pretty good question, I can only offer my opinion - look at FM changes to F-15 and Su-27, historically:

F-15 FM was completed a couple of years ago and generally has remained stable. A couple of fixes were made to the throttle (not thrust).

Remaining issues:

1. Control lock-up issues in certain scenarios (not realistic)

2. Fuel consumption is too high in AB

3. IMHO, all AB stages that aren't stage 5 are too weak and mostly useless

4. Lack of over-g DM (not just for the airframe, but for flaps and gear at lower g's)

5. Lack of over-speed DM

6. Wing tanks have too much supersonic drag IMHO.

Su-27 FM has had a little more development, and latest additions are:

1. Over-g DM

2. Engine thrust variation based on OAT

3. I don't know if there are outstanding FM/control issues

Notice that none of this stuff is for performance at standard day - that performance is now fixed and verified multiple times by multiple people. A lot of the eagle data is available publicly and you can check it out yourself.

A lot of good flanker data we aren't going to see unfortunately, but YoYo has it and he knows what to do with it. The FM matches the little amount of data that we do have.

So in my mind there's no question about the turning/acceleration performance as far as a clean aircraft is concerned. Yes, it's not 100% accurate, there are small deviations but they're within acceptable error margin for both aircraft.

You can verify the FMs against all available data ... you don't need a CFD.

If they have data, i really hope they do, then why fligh model changes from time to time? I can understand structural modelling or damage model being hidden or hard to evaluate but flight performance margins should be clearly known and clearly immitated if ed guys have them. I again hope that they have aerodynamic data available. From my perspective they are close to real but again, independent certification is quantum leap.

 

 

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I just feel very frustrated that ED messed up the FM of Su-27/33 after those two "Hot fixes". The pitch responses after trimming now become way too sensitive to make AOA stable,

so I have to constantly trim just to get a level and straight flight. Also, the aircraft now always has a tendency to bend the right on its own, especially after a missile /missiles loaded on the left of the aircraft is/are fired away. These two major bugs were not in 1.5 and 2.2, why do they have to fix what were perfect ?!

I just feel very frustrated that ED messed up the FM of Su-27/33 after those two "Hot fixes". The pitch responses after trimming now become way too sensitive to make AOA stable,

so I have to constantly trim just to get a level and straight flight. Also, the aircraft now always has a tendency to bend the right on its own, especially after a missile /missiles loaded on the left of the aircraft is/are fired away. These two major bugs were not in 1.5 and 2.2, why do they have to fix what were perfect ?!

I think you're mistaken about changes to pitch response. I have 1.5 Flanker tracks that play back perfectly with 2.5 plus the hot fixes. So none of that's been touched. If it had, those tracks would be broken.

Also, the aircraft now always has a tendency to bend the right on its own, especially after a missile /missiles loaded on the left of the aircraft is/are fired away.

It's not a bug, it's realism.

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.

Yes, that's what I'm saying. The turn performance of the Flanker is very degraded (became unrealistic) from earlier updates. What makes you think I've said the other way around?

I know it doesn't affect G-load, but only AoA. The AoA is not limited to 26, but to 22 at the moment. With that override you can hold around 30 (but varies with trim). I don't know what am I doing wrong cause it seems that you understood me the other way!

Regards!

The Flanker's lift slope and supercritical AoA (where the highest post stall CL is obtained) should be very similar to that of an F-16, and here's the F-16's real aerodynamic performance data:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19800005879.pdf

As you can determine from the tables (page 60 of pdf), the F-16 has a CZ of 1.65 at 25 AoA at zero elevator deflection and no flaps, at Mach 0.05. As Mach increases towards around 0.3, all known airplanes find an increase in lift slope and maximum CL. I remember (years behind) from some tables versus Mach, that at Mach 0.3, the F-16's max CL rises to around 1.78 (from 1.6 at very low Mach). Only above Mach 0.3, the critical AoA and maximum CL start to decrease. The peak critical/supercritical AoA and CL max are usually found around Mach 0.3. In DCS, at Mach 0.3, the Su-27 has 1.9 with full flaps at 25 AoA. The flaps always increase the local CL, so as a comparison to he F-16's data (with no flaps), the Flanker's CL at 25 AoA with full flaps should be higher than 1.78, I'd say roughly around over 2. 1.9 as it is right now doesn't seem too low, yet for some reason during actual simulation in DCS even the Eagle out turns the Su-27 at any speed regime at similar G-load and AoA and the Flanker isn't proving real life comparable turn rates. The turn radius is inversely proportional to the turning capability of an aircraft (CL times wing area divided by weight force). Right now the Flanker not only has a very poor constant turn rate, but also the instantaneous turn rate is lower than that of the F-15C and the turn radius is almost identical to that of the F-15 now when it should be quite lower.

This stuff doesn't look normal. The Flanker (clean loadout and around 25-30% fuel) should be able to complete a 360 horizontal turn in merely 12 seconds starting from corner velocity (a bit above 700km/h IAS), not 16 seconds. Reality speaks, no me...! In real life, as provided in those videos, the averge turn rate of the Su-27 is around 30 deg/second (360 degrees in 12 seconds). That is average, not maximum which may be 50% higher at corner velocity and 9G.

Regards!

Have you tried disabling the AoA limiter?

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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.

Regarding the inverted flat spin, it's simply exaggerated. When I'll get the time I'll put my view (as an aerodynamicist and flight dynamics man) into perspective. Indeed due to the relative position between the elevators and wings (in vertical plane), the elevators become shadowed by the wing at AoA's below -20, -25.., but the effect of lift loss on the elevators due to wing shadowing should be much lower than it is right now simulated and this is mainly due to the fact that the LERX still generate enough high energy vortex under the wing now (at negative AoA) which is more than enough to keep a good airflow reaching the elevators, so the unstable pitch down moment should be much more reduced than it is. When Flanker pilots develop the tailslide at airshows their nose doesn't even drop below 80.85 degrees of pitch down attitude, while in DCS you enter negative deep stall rapidly, so this thing can be easily spotted as abnormal. If real pilots would perform the tailslide they should all die as DCS suggests, lol! Again, this is another discussion for which an important separate thread should be started

The blackout simulation in DCS is probably still a WIP right now. I have talked about this myself for years and it seems people like to play deaf about it.

Real pilots (not starving monkeys) can stand at 12G for as long as 15 seconds minimum or at 9G for 30 seconds with no light loss (no tunnel vision yet), while in DCS your pilot blacks out at 9G in 5 seconds (chronometered from G onset). Incredible isn't it? And about the redout in DCS, it's even worse. Only of you do a fast roll you enter redout=))). Fu#@ing hilarious, but I don't know if they're going to fix this if people are not pressing them to change their view on blackout.

Regards!

Have you tried disabling the AoA limiter?

I have my friend, but that won't change the turning limitations of this aircraft right now. With or without AoA limiter set, the instantaneous and sustained turn rates are quite poor to be comparable to the real plane, it's all that is.

Given up on that fight right now - a warm-up will buy you a bit more g-tolerance.

As for the -g, the representation is fair. The reason is that severe -g is not something combat pilots train for, and it absolutely ruins their ability to continue fighting (mental faculties), as well as their +g tolerance for the rest of the fight. IIRC from studies.

Just.don't.do.-g. :)

For the roll, that's a symptom of something else ... use +g and/or turn off the black-out simulation, do a severe loaded roll and watch the g on the external g-meter.

Real pilots (not starving monkeys) can stand at 12G for as long as 15 seconds minimum or at 9G for 30 seconds with no light loss (no tunnel vision yet), while in DCS your pilot blacks out at 9G in 5 seconds (chronometered from G onset). Incredible isn't it? And about the redout in DCS, it's even worse. Only of you do a fast roll you enter redout=))). Fu#@ing hilarious, but I don't know if they're going to fix this if people are not pressing them to change their view on blackout.

 

Regards!

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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.

You're right, yet I personally couldn't get access to a Su-27's Cy (CL) vs AoA at any flight regime, so I had to improvise right now by rather comparing the Su-27 to the F-16, which I'm pretty sure is a good comparison, aerodynamically speaking. The F-16 beats the F-15 in constant turn rates, yet not ITR. Lack of documentation data won't necessarily discourage me to seek for alternatives in order to estimate what I'm looking for, although I am aware of errors, but how great the errors are depend on how I approach the problem. Simply by looking at those videos with the turning time of the real Su-27 we can directly figure out an average turn rate without the need of any scientific data (which I must admit that I prefer over beliefs). What can be more real than what the airplane tells directly in the air? So now, even if the real data (from flight manual and other documentations) confirms that the Flanker turns as it is also being proven by the videos, why doesn't the DCS Flanker prove the same? This is the problem, nothing else! In reality, this aircraft (the Su-27) completes a horizontal 360 turn in slightly over 12 seconds (Roughly 30 deg/s average turn rate. I don't know the ITR nor the sustained). in DCS, for some reason if other then inaccurate aero data, the Flanker can't manage to get an average turn rate higher than 24 deg/s or complete the turn in less than 15 seconds even if it has 1kg of fuel left, no matter what tricks one might try with the AoA limiter without breaking the wings. This is what it is!

Regards!

Not to derail this conversation... but F-15>Flanker.

But it doesn't matter, once the Hornet comes out we'll be toasting you with that. :joystick: haha