Sukhoi Su-57 flight testing, development & operations [2012-current]

[Evgeniy]

to Su-57 (say 200-250 units) and Su-75 (400-500).

Sorry, but in my opinion, the opposite is more likely.
Su-57, as a front-line fighter, is superior to LTS. And that is why the number of the Su-57 should prevail.
I recently remembered the Su-17. I remembered him for a reason. Russia does not have and does not see a front-line strike aircraft for the future except for the LTS. That is why I made the assumption that LTS will be a kind of JSF. Which will fill an absolutely empty niche of a promising front-line strike aircraft. And at the same time a light fighter to replace the MiG-29, but in the second stage.
The Su-34 is not suitable for such a promising role as the S-70.

 

[LMFS]

Yes, of course. But it would have been so from the very beginning.
I mean what else. Now this news will spread in its not entirely correct interpretation.

Some people are going to badmouth the plane for whatever reason, be it real or imaginary, so it does not really matter what they say. Relax and enjoy seeing the Su-57 gradually evolve into what it is intended to be, while haters eat crow xD

Sorry, but in my opinion, the opposite is more likely.
Su-57, as a front-line fighter, is superior to LTS. And that is why the number of the Su-57 should prevail.
I recently remembered the Su-17. I remembered him for a reason. Russia does not have and does not see a front-line strike aircraft for the future except for the LTS. That is why I made the assumption that LTS will be a kind of JSF. Which will fill an absolutely empty niche of a promising front-line strike aircraft. And at the same time a light fighter to replace the MiG-29, but in the second stage.
The Su-34 is not suitable for such a promising role as the S-70.

Light fighters are naturally more abundant in any air force than high end air superiority airframes, it is only logical. In the case of LTS, it is not only a light fighter, but an UCAV. So, my estimation for the LTS numbers is actually quite conservative IMHO.

The force composition proposed by Strelets is Su-57, Okhotnik and LTS. The other fighter, reconnaissance and tactical bomber types should be progressively phased out. As to VMF-MA, it is difficult to predict how its different branches will evolve, but it needs to grow even more than the VKS and a PAK-KA is also a topic there that needs addressing, hopefully with the Su-57.

 

[Josh_TN]

I've never heard of PAK-KA; is this a prospective embarked fighter program? A quick google search was cluttered with Pakistani programs.

 

[LMFS]

I've never heard of PAK-KA; is this a prospective embarked fighter program? A quick google search was cluttered with Pakistani programs.

Yes, this was mentioned by officials a few years ago, but has not seen a lot of media coverage or follow up statements. Given the intrinsic characteristics of the airframe, it does not seem far fetched to think that the Su-57 in a naval version could be that plane, that would be additional production numbers to take into account.

This link may help as a reference, though I have not checked if all the info is reliable:

ÐвиаÑионнÑе комплекÑÑ Ð°Ð²Ð¸Ð°Ñии Ðа Ñем ÑоÑÑийÑкие ÐÐС ÑоÑÑÑ Ð»ÐµÑаÑÑ Ð² XXI веке

РРоÑÑии Ñже не пеÑвÑй год Ð¸Ð´ÐµÑ ÑабоÑа над пÑоекÑами пÑинÑипиалÑно новÑÑ Ð±Ð¾ÐµÐ²ÑÑ ÑамолеÑов. ÐолÑÑÐ°Ñ ÑаÑÑÑ Ð¸Ð· Ð½Ð¸Ñ ÐºÑоеÑÑÑ Ð¿Ð¾Ð´ неÑклÑжей ÑзÑковой конÑÑÑÑкÑией «ÐеÑÑпекÑивнÑй авиаÑионнÑй...

lenta.ru

 

[Blitzo]

I've never heard of PAK-KA; is this a prospective embarked fighter program? A quick google search was cluttered with Pakistani programs.

Yes, this was mentioned by officials a few years ago, but has not seen a lot of media coverage or follow up statements. Given the intrinsic characteristics of the airframe, it does not seem far fetched to think that the Su-57 in a naval version could be that plane, that would be additional production numbers to take into account.

This link may help as a reference, though I have not checked if all the info is reliable:

ÐвиаÑионнÑе комплекÑÑ Ð°Ð²Ð¸Ð°Ñии Ðа Ñем ÑоÑÑийÑкие ÐÐС ÑоÑÑÑ Ð»ÐµÑаÑÑ Ð² XXI веке

РРоÑÑии Ñже не пеÑвÑй год Ð¸Ð´ÐµÑ ÑабоÑа над пÑоекÑами пÑинÑипиалÑно новÑÑ Ð±Ð¾ÐµÐ²ÑÑ ÑамолеÑов. ÐолÑÑÐ°Ñ ÑаÑÑÑ Ð¸Ð· Ð½Ð¸Ñ ÐºÑоеÑÑÑ Ð¿Ð¾Ð´ неÑклÑжей ÑзÑковой конÑÑÑÑкÑией «ÐеÑÑпекÑивнÑй авиаÑионнÑй...

lenta.ru

Has there been any consideration for how the tailhook of a navalized Su-57 would be configured?

The arrangement of Su-57's engine nacelles and weapons bay, means that the rear weapons bay is right about where you'd put the tailhook at.
I can't imagine a navalized Su-57 would see the aircraft replace its rear weapons bay solely for a tailhook, but I also am not sure what kind of tailhook solution they could devise in a manner that fits with the current aft/ventral fuselage geometry.

 

[helmutkohl]

^ I guess it would depend on what kind of tailhook system its using.
I havent measured anything but a quick glance at the Su-33's tail hook seems like it could fit on the remaining space of the Su-57.
but if its something like the F-35C's tailhook which is enclosed, then yes, it doesn't seem like there's sufficient spacing in the existing space.

 

[LMFS]

Has there been any consideration for how the tailhook of a navalized Su-57 would be configured?

The arrangement of Su-57's engine nacelles and weapons bay, means that the rear weapons bay is right about where you'd put the tailhook at.
I can't imagine a navalized Su-57 would see the aircraft replace its rear weapons bay solely for a tailhook, but I also am not sure what kind of tailhook solution they could devise in a manner that fits with the current aft/ventral fuselage geometry.

I think paralay did some drawing about that, but probably it is perfectly possible to place the hook at the sting after the rear bay, maybe it would be necessary to make it longer, but I don't think losing the rear bay would be really necessary. The rest of the plane looks very easily compatible with the naval role, with its oversized landing gear and outstanding lift generation, low speed flight and high alpha capabilities. Newer engines on top of that would allow STOBAR operations with none or very little payload restrictions.

 

[Acatomic]

"Tests of the aircraft with the new engine should be completed by 2024. In general, tests with the completion of the second stage engine will last until 2026, and the delivery of aircraft in a new look is planned as part of the new state armament program from 2027. This will be about 25 cars out of 76 under the already concluded long-term contract, " Yelchaninov said.

What new look? Redesign?

 

[Ainen]

"Tests of the aircraft with the new engine should be completed by 2024. In general, tests with the completion of the second stage engine will last until 2026, and the delivery of aircraft in a new look is planned as part of the new state armament program from 2027. This will be about 25 cars out of 76 under the already concluded long-term contract, " Yelchaninov said.

What new look? Redesign?

Translation bug (language difference)
Means new block/tranche/whatever basically.

 

[Evgeniy]

What new look? Redesign?

With a second stage engine.

 

[Acatomic]

"Tests of the aircraft with the new engine should be completed by 2024. In general, tests with the completion of the second stage engine will last until 2026, and the delivery of aircraft in a new look is planned as part of the new state armament program from 2027. This will be about 25 cars out of 76 under the already concluded long-term contract, " Yelchaninov said.

What new look? Redesign?

Translation bug (language difference)
Means new block/tranche/whatever basically.

Ok this is the original: "поставка самолетов в новом облике запланирована в рамках новой госпрограммы вооружения с 2027 года."

My understanding would be -> new shape/form.

 

[LMFS]

What new look? Redesign?

Apart from the new engine as pointed out by Evgeniy, the hydraulic actuators will be replaced with electric ones, new cockpit and avionics will be included and new weapons integrated. I don't know if someone has heard about further elements of the modernization?

 

[Acatomic]

Let's first see if it's what @Ainen wrote - language difference.

 

[Blitzo]

Has there been any consideration for how the tailhook of a navalized Su-57 would be configured?

The arrangement of Su-57's engine nacelles and weapons bay, means that the rear weapons bay is right about where you'd put the tailhook at.
I can't imagine a navalized Su-57 would see the aircraft replace its rear weapons bay solely for a tailhook, but I also am not sure what kind of tailhook solution they could devise in a manner that fits with the current aft/ventral fuselage geometry.

I think paralay did some drawing about that, but probably it is perfectly possible to place the hook at the sting after the rear bay, maybe it would be necessary to make it longer, but I don't think losing the rear bay would be really necessary. The rest of the plane looks very easily compatible with the naval role, with its oversized landing gear and outstanding lift generation, low speed flight and high alpha capabilities. Newer engines on top of that would allow STOBAR operations with none or very little payload restrictions.

The rest of the aircraft looks reasonable for carrier use, the issue when I've thought about it every now and then, is always about the tailhook.
Extending the tailsting to accommodate a tailhook could be plausible, but given the geometry of the ventral fuselage/tailsting, you'd have to extend it quite a bit to accommodate the full size of a tailhook in a stealthy manner.
Then there is also the issue of whether a longer tailsting would degrade carrier landing angles (Su-33 famously of course has a shortened tailsting relative to land based Flankers for this reason)

 

[Manuducati]

The standard dropping low mounted hook is not the only option. Vought was quite imaginative there, as with the XF5-U and F7U.

 

[LMFS]

I think this is from paralay:

 

[kaiserd]

Is there any indication that the Su-57 was actually designed with a carrier based version or is this all purely speculative?

You can’t just turn a design into a carrier fighter by bolting on an improvised arrester hook.

 

[QuadroFX]

Canopy chicken-test:

View: https://youtu.be/OicQuluXLTk

 

[stealthflanker]

Now I saw them, sorry. I think you can safely assume they are treated, even those in the newer RD33MK are. Probably you can change the geometry (make the vanes deeper for instance) so they are more selective in the beam entry angle, or even include an S shaped duct on them, but that may have influence in the engine's performance...

Now onto a subject of Guide vane treatment. This is the result from it. X-band (8 GHz) and Frontal.

I just replacing my graphics card and basically update Windows to win10 which was very unpleasant experience. But it's here. This is the contour plot for the frontal aspect. basically the same as my previous estimates. although the size of the image differs they are comparable.

Without Blocker	With Blocker but No guide vanes treatment	With guide vanes treatment + radar blocker
Strong lobe from the engine	Engine reflection, greatly reduced by blocker	Inlet guidevane treatment appears to further weakening the remaining reflection from the engine.

As seen there are still "residual"reflection but the guide vane treatment appears to be successfully weaken the previously seen "hotspot" remains after blocker application.

 

[LMFS]

As seen there are still "residual"reflection but the guide vane treatment appears to be successfully weaken the previously seen "hotspot" remains after blocker application.

Cool. Surely there is a lot of room for optimization when playing with the materials, geometry and simulation parameters, but that is already an interesting result.

I am curious, have you actually simulated an AESA radar antenna in X band? Diffraction over all those thousands of single antenna elements must be both a nightmare to simulate and a hell of a backscatter source, maybe orders of magnitude above geometrical elements of the fuselage as entertained by most RCS simulations

 

[overscan (PaulMM)]

As seen there are still "residual"reflection but the guide vane treatment appears to be successfully weaken the previously seen "hotspot" remains after blocker application.

Cool. Surely there is a lot of room for optimization when playing with the materials, geometry and simulation parameters, but that is already an interesting result.

I am curious, have you actually simulated an AESA radar antenna in X band? Diffraction over all those thousands of single antenna elements must be both a nightmare to simulate and a hell of a backscatter source, maybe orders of magnitude above geometrical elements of the fuselage as entertained by most RCS simulations

That's why frequency selective surface radomes exist.

 

[LMFS]

That's why frequency selective surface radomes exist.

That's why I said X band

 

[stealthflanker]

I am curious, have you actually simulated an AESA radar antenna in X band? Diffraction over all those thousands of single antenna elements must be both a nightmare to simulate and a hell of a backscatter source, maybe orders of magnitude above geometrical elements of the fuselage as entertained by most RCS simulations

No. But i could try maybe with more support.

Nonetheless. Radar antenna is essentially behave like a flat plate. and for a good reason, as it would be a nightmare to generate beams in curved surfaces thus why we havent really see "proper" conformal array radar. Unless one can accept sacrifice in larger beamwidth and potentially more sidelobes plus.. the array will be more difficult to build and cool.

Canting the array upward and treat the edges seems to be the currently available means to reduce the structural mode RCS and the specular one.

 

[Ronny]

That's why frequency selective surface radomes exist.

That's why I said X band

X-band is pretty wide range, about 4 GHz wide. Radar bandwidth is narrower than that.
There is also polarization, the FSS random will likely reflect wave with different (perpendicular) polarization compared to the polarization of the operating radar

 

[LMFS]

No. But i could try maybe with more support.

Nonetheless. Radar antenna is essentially behave like a flat plate. and for a good reason, as it would be a nightmare to generate beams in curved surfaces thus why we havent really see "proper" conformal array radar. Unless one can accept sacrifice in larger beamwidth and potentially more sidelobes plus.. the array will be more difficult to build and cool.

Canting the array upward and treat the edges seems to be the currently available means to reduce the structural mode RCS and the specular one.

I guess that is a really complex topic, and in fact I don't know if available tools are good enough to simulate the hellish complexity of the diffracted fields generated by say 2000 individual TRM antennas in the radar... but it is clear to me this is maybe the biggest "elephant in the room" (there are several other ones) in terms of RCS calculations, selective radomes notwithstanding

 

[stealthflanker]

I guess that is a really complex topic, and in fact I don't know if available tools are good enough to simulate the hellish complexity of the diffracted fields generated by say 2000 individual TRM antennas in the radar... but it is clear to me this is maybe the biggest "elephant in the room" (there are several other ones) in terms of RCS calculations, selective radomes notwithstanding

Well one actually can do that. It is not some sort of black arts. If you read Chapter 6 of "Introduction to RF Stealth" It contains the methods for modeling Stealthy antenna scattering along with radome integration.

The modeling result will still be speculative however as nobody really know how Su-57 Radome or how the antenna is treated.

I am however not planning to go that deep yet unless very necessary or there is external push to do so. It is complicated but i found that what should be presented and how to be the rest of the 50% (the other 50% of course being the modeling process). As i said previously there actually no real standard on how RCS data should be presented i.e everyone is basically doing whatever they want.

 

[sanjeev.k]

Looks like our member Paralay's statement that Su-57 will get flat nozzles in the future (it was in the LTS checkmate thread, page 36) seems to have gotten validated by this media report from TASS (quoting major general Vladimir Popov)

Su-57 fifth-generation fighter may get flat nozzle for stealth purposes — pilot

The flat nozzle technology is a breakthrough in modern aircraft-building, Major-General Vladimir Popov noted

tass.com

Few points to ponder
1) Just wondering if Su-57 will sport a f-22 style 2-D paddle nozzle (since that would incur weight and maintenance complexity)
2) Was wondering if Sukhoi/NPO Saturn are exploring possibility of fluidic vectoring flat nozzles instead of the 2-D paddle style
a) Since in an interview with the Sukhoi R&D chief (sometime back), he mentioned that they were researching 'gas dynamic control schemes' (that was of course the English translation of the Russian article). I am guessing the phrase 'gas dynamic scheme' means fluidic vectoring, but I could be wrong
b) NPO Saturn have anyway stated they are researching 3 stream ADVENT engines (presumably for future iterations of Su-57), so
was wondering if the 3rd stream can be also leveraged for fluidic control.

Of course - I am not aware how effective fluidic controls are at high altitude (20,000+ metres) regime of the Su-57. Maybe some of the aerospace engineers on this forum can answer this?

 

[FighterJock]

Looks like our member Paralay's statement that Su-57 will get flat nozzles in the future (it was in the LTS checkmate thread, page 36) seems to have gotten validated by this media report from TASS (quoting major general Vladimir Popov)

Su-57 fifth-generation fighter may get flat nozzle for stealth purposes — pilot

The flat nozzle technology is a breakthrough in modern aircraft-building, Major-General Vladimir Popov noted

tass.com

Few points to ponder
1) Just wondering if Su-57 will sport a f-22 style 2-D paddle nozzle (since that would incur weight and maintenance complexity)
2) Was wondering if Sukhoi/NPO Saturn are exploring possibility of fluidic vectoring flat nozzles instead of the 2-D paddle style
a) Since in an interview with the Sukhoi R&D chief (sometime back), he mentioned that they were researching 'gas dynamic control schemes' (that was of course the English translation of the Russian article). I am guessing the phrase 'gas dynamic scheme' means fluidic vectoring, but I could be wrong
b) NPO Saturn have anyway stated they are researching 3 stream ADVENT engines (presumably for future iterations of Su-57), so
was wondering if the 3rd stream can be also leveraged for fluidic control.

Of course - I am not aware how effective fluidic controls are at high altitude (20,000+ metres) regime of the Su-57. Maybe some of the aerospace engineers on this forum can answer this?

If the Su-57 gets flat vectoring nozzles I wonder what will happen to the three dimensional system that the Russians have now? and those crazy manoeuvres that they do with the round nozzles.

 

[Dr.Snufflebug]

Looks like our member Paralay's statement that Su-57 will get flat nozzles in the future (it was in the LTS checkmate thread, page 36) seems to have gotten validated by this media report from TASS (quoting major general Vladimir Popov)

Su-57 fifth-generation fighter may get flat nozzle for stealth purposes — pilot

The flat nozzle technology is a breakthrough in modern aircraft-building, Major-General Vladimir Popov noted

tass.com

Few points to ponder
1) Just wondering if Su-57 will sport a f-22 style 2-D paddle nozzle (since that would incur weight and maintenance complexity)
2) Was wondering if Sukhoi/NPO Saturn are exploring possibility of fluidic vectoring flat nozzles instead of the 2-D paddle style
a) Since in an interview with the Sukhoi R&D chief (sometime back), he mentioned that they were researching 'gas dynamic control schemes' (that was of course the English translation of the Russian article). I am guessing the phrase 'gas dynamic scheme' means fluidic vectoring, but I could be wrong
b) NPO Saturn have anyway stated they are researching 3 stream ADVENT engines (presumably for future iterations of Su-57), so
was wondering if the 3rd stream can be also leveraged for fluidic control.

Of course - I am not aware how effective fluidic controls are at high altitude (20,000+ metres) regime of the Su-57. Maybe some of the aerospace engineers on this forum can answer this?

If the Su-57 gets flat vectoring nozzles I wonder what will happen to the three dimensional system that the Russians have now? and those crazy manoeuvres that they do with the round nozzles.

Isn't it more like 2.5D? They only swivel in one axis, but it's offset. I might have outdated information but to my knowledge the only full 3D TVC the Russians have flown was in the MiG-29OVT.

There was a number of concept drawings/photoshops and one 3D model showing F-22-esque nozzles on the Su-57, and they were slanted, to keep the 2.5D TVC functionality. Looked very cool, at any rate.

But the statement in TASS above seems to be speculative, not a confirmation of any sort. After all, they developed the serrated izd. 30 nozzles already, and the talk was for the longest time that flat ditto were decided against because of efficiency loss.

 

[Scar]

Isn't it more like 2.5D?

Yes, it is.

 

[FighterJock]

Looks like our member Paralay's statement that Su-57 will get flat nozzles in the future (it was in the LTS checkmate thread, page 36) seems to have gotten validated by this media report from TASS (quoting major general Vladimir Popov)

Su-57 fifth-generation fighter may get flat nozzle for stealth purposes — pilot

The flat nozzle technology is a breakthrough in modern aircraft-building, Major-General Vladimir Popov noted

tass.com

Few points to ponder
1) Just wondering if Su-57 will sport a f-22 style 2-D paddle nozzle (since that would incur weight and maintenance complexity)
2) Was wondering if Sukhoi/NPO Saturn are exploring possibility of fluidic vectoring flat nozzles instead of the 2-D paddle style
a) Since in an interview with the Sukhoi R&D chief (sometime back), he mentioned that they were researching 'gas dynamic control schemes' (that was of course the English translation of the Russian article). I am guessing the phrase 'gas dynamic scheme' means fluidic vectoring, but I could be wrong
b) NPO Saturn have anyway stated they are researching 3 stream ADVENT engines (presumably for future iterations of Su-57), so
was wondering if the 3rd stream can be also leveraged for fluidic control.

Of course - I am not aware how effective fluidic controls are at high altitude (20,000+ metres) regime of the Su-57. Maybe some of the aerospace engineers on this forum can answer this?

If the Su-57 gets flat vectoring nozzles I wonder what will happen to the three dimensional system that the Russians have now? and those crazy manoeuvres that they do with the round nozzles.

Isn't it more like 2.5D? They only swivel in one axis, but it's offset. I might have outdated information but to my knowledge the only full 3D TVC the Russians have flown was in the MiG-29OVT.

There was a number of concept drawings/photoshops and one 3D model showing F-22-esque nozzles on the Su-57, and they were slanted, to keep the 2.5D TVC functionality. Looked very cool, at any rate.

But the statement in TASS above seems to be speculative, not a confirmation of any sort. After all, they developed the serrated izd. 30 nozzles already, and the talk was for the longest time that flat ditto were decided against because of efficiency loss.

Perhaps it was the MiG-29OVT that I was getting mixed up with Dr.Snufflebug.

 

[TMA1]

Looks like our member Paralay's statement that Su-57 will get flat nozzles in the future (it was in the LTS checkmate thread, page 36) seems to have gotten validated by this media report from TASS (quoting major general Vladimir Popov)

Su-57 fifth-generation fighter may get flat nozzle for stealth purposes — pilot

The flat nozzle technology is a breakthrough in modern aircraft-building, Major-General Vladimir Popov noted

tass.com

Few points to ponder
1) Just wondering if Su-57 will sport a f-22 style 2-D paddle nozzle (since that would incur weight and maintenance complexity)
2) Was wondering if Sukhoi/NPO Saturn are exploring possibility of fluidic vectoring flat nozzles instead of the 2-D paddle style
a) Since in an interview with the Sukhoi R&D chief (sometime back), he mentioned that they were researching 'gas dynamic control schemes' (that was of course the English translation of the Russian article). I am guessing the phrase 'gas dynamic scheme' means fluidic vectoring, but I could be wrong
b) NPO Saturn have anyway stated they are researching 3 stream ADVENT engines (presumably for future iterations of Su-57), so
was wondering if the 3rd stream can be also leveraged for fluidic control.

Of course - I am not aware how effective fluidic controls are at high altitude (20,000+ metres) regime of the Su-57. Maybe some of the aerospace engineers on this forum can answer this?

If the Su-57 gets flat vectoring nozzles I wonder what will happen to the three dimensional system that the Russians have now? and those crazy manoeuvres that they do with the round nozzles.

Isn't it more like 2.5D? They only swivel in one axis, but it's offset. I might have outdated information but to my knowledge the only full 3D TVC the Russians have flown was in the MiG-29OVT.

There was a number of concept drawings/photoshops and one 3D model showing F-22-esque nozzles on the Su-57, and they were slanted, to keep the 2.5D TVC functionality. Looked very cool, at any rate.

But the statement in TASS above seems to be speculative, not a confirmation of any sort. After all, they developed the serrated izd. 30 nozzles already, and the talk was for the longest time that flat ditto were decided against because of efficiency loss.

This was posted on russiadefenseforum it is a really interesting picture showing a potential nozzle layout for the su-57.

 

[overscan (PaulMM)]

Hey, Dad!

(Rockwell ATF nozzle study)

 

[LMFS]

I am however not planning to go that deep yet unless very necessary or there is external push to do so.

The "push" would be to see whether the frontal RCS of the plane's geometry (devoid of actual constructive details) is -30/-40 dBsm while your radar antenna is -10/-20, which would not be surprising to me.

 

[stealthflanker]

The "push" would be to see whether the frontal RCS of the plane's geometry (devoid of actual constructive details) is -30/-40 dBsm while your radar antenna is -10/-20, which would not be surprising to me.

That's not enough TBH.

 

[LMFS]

That's not enough TBH.

It is your time and your decision, not even suggesting otherwise

 

[TMA1]

Hey, Dad!

(Rockwell ATF nozzle study)

Lovely. The engineers of that period were incredible.

 

[Dr.Snufflebug]

Looked very cool, at any rate.

Managed to find two of them. These go way back and were made by some 3D artist that is probably familiar to some here or at Paralay. So entirely non-official. But yeah, looked cool with them being canted and all, to facilitate the Su-57s TVC scheme. Regarding that Rockwell concept above, did they explain their rationale for doing it that way?

 

[Dr.Snufflebug]

Looks like our member Paralay's statement that Su-57 will get flat nozzles in the future (it was in the LTS checkmate thread, page 36) seems to have gotten validated by this media report from TASS (quoting major general Vladimir Popov)

Su-57 fifth-generation fighter may get flat nozzle for stealth purposes — pilot

The flat nozzle technology is a breakthrough in modern aircraft-building, Major-General Vladimir Popov noted

tass.com

Few points to ponder
1) Just wondering if Su-57 will sport a f-22 style 2-D paddle nozzle (since that would incur weight and maintenance complexity)
2) Was wondering if Sukhoi/NPO Saturn are exploring possibility of fluidic vectoring flat nozzles instead of the 2-D paddle style
a) Since in an interview with the Sukhoi R&D chief (sometime back), he mentioned that they were researching 'gas dynamic control schemes' (that was of course the English translation of the Russian article). I am guessing the phrase 'gas dynamic scheme' means fluidic vectoring, but I could be wrong
b) NPO Saturn have anyway stated they are researching 3 stream ADVENT engines (presumably for future iterations of Su-57), so
was wondering if the 3rd stream can be also leveraged for fluidic control.

Of course - I am not aware how effective fluidic controls are at high altitude (20,000+ metres) regime of the Su-57. Maybe some of the aerospace engineers on this forum can answer this?

If the Su-57 gets flat vectoring nozzles I wonder what will happen to the three dimensional system that the Russians have now? and those crazy manoeuvres that they do with the round nozzles.

Isn't it more like 2.5D? They only swivel in one axis, but it's offset. I might have outdated information but to my knowledge the only full 3D TVC the Russians have flown was in the MiG-29OVT.

There was a number of concept drawings/photoshops and one 3D model showing F-22-esque nozzles on the Su-57, and they were slanted, to keep the 2.5D TVC functionality. Looked very cool, at any rate.

But the statement in TASS above seems to be speculative, not a confirmation of any sort. After all, they developed the serrated izd. 30 nozzles already, and the talk was for the longest time that flat ditto were decided against because of efficiency loss.

Perhaps it was the MiG-29OVT that I was getting mixed up with Dr.Snufflebug.

The MiG-29OVT was a one-off, but it did demonstrate a mature technology.

If you're familiar with the Su-30M (and all its export variants), and the Su-35S, you know how their TVC nozzles work, 2.5D. The T-50 and Su-57 stick to the same scheme, the by now standard Saturn TVC.

The aforementioned MiG had full 3D TVC, and when in action it almost looks kind of unsettling:

Like uncannily organic. Forgive me if I'm ignorant, but AFAIK Klimov developed this TVC technology before they were merged with Saturn (Lyulka) in the UEC, and even presented a serrated "stealth" nozzle for this system (which was confused by a lot of people and publications with Saturns izd. 30 nozzle at the time, in spite of glaring differences).

Yet, it faded into obscurity somehow.

 

[stealthflanker]

The one developed "3D" TVC for Su-27 platform i think was Salyut. The first iteration was LL-UV-KS. Salyut seems to keep on developing the design.

as depicted here (old vid unfortunately)

View: https://www.youtube.com/watch?v=lUl3ED7WUHQ

anoter vid, focusing entirely on the TVC

View: https://www.youtube.com/watch?v=wsJyC5g4IBo