Su-57 Stealth Fighter: News #6

Yeah f-23 really was a fascinating design. Pretty good stuff. I agree if Russians were inspired by Northrop's design that it was a good call. Same with the Chinese and the mig 1.42. In fact I wish I could have seen the documents if Russia did help the Chinese out. Wonder if there were even more advanced iterations of the mig that might still be classified by Russia.

As far as how influenced the su 57 might have been, it would've been the only in the very broadest sense. I guess an analogy would be the supposed A-5/Mig-25 connection which if true was only a very very basic inspiration (lateral intakes, etc). The su-57 is aerodynamically a completely different animal to the f-23 and the only fairly clear influenced might be the radome and nose of the su-57 and the general flat, blended body aspect.

kvs wrote:

miketheterrible wrote:I think the reason was that they never used the YF was because
1) more expensive
2) Lockheed Martin has a stronger influence in US politics.

YF-23 was a rather good design and it wouldnt be a bad idea to grab some influence designs from it.

Most planes are similar to other planes.   There is way too much false attribution of originality and "copying"
inferences.  





Not so similar now.

Sorry but i didn't see anything even vaguely similar in this two.
Wing is completely different, f-23 has no horizontal tail, engine placement is completely different.

Sorry, when I see a Su-57 I see the successor of the Su-27 design, when I see the F-22 a successor of F-15 and when is the case of J-20 i see an evolution of J-10 and J-9.
YF-23 bear IMHO instead just a vague influence from the SR-71.
When I see an F-35 instead, i just feel sick.

marcellogo wrote:

kvs wrote:

miketheterrible wrote:I think the reason was that they never used the YF was because
1) more expensive
2) Lockheed Martin has a stronger influence in US politics.

YF-23 was a rather good design and it wouldnt be a bad idea to grab some influence designs from it.

Most planes are similar to other planes.   There is way too much false attribution of originality and "copying"
inferences.  





Not so similar now.

Sorry but i didn't see anything even vaguely similar in this two.
Wing is completely different, f-23 has no horizontal tail, engine placement is completely different.

Sorry, when I see a Su-57 I see the successor of the Su-27 design, when I see the F-22 a successor of F-15 and when is the case of J-20 i see an evolution of J-10 and J-9.
YF-23 bear IMHO instead just a vague influence from the SR-71.
When I see an F-35 instead, i just feel sick.

Actually the schtick with the YF-23 and Pak-Fa has been that the Russian designers just pulled back the wings closer to the rear in comparaison to the YF-23. This ignores the size differences and engine choices and the wing area.

marcellogo wrote:

kvs wrote:

miketheterrible wrote:I think the reason was that they never used the YF was because
1) more expensive
2) Lockheed Martin has a stronger influence in US politics.

YF-23 was a rather good design and it wouldnt be a bad idea to grab some influence designs from it.

Most planes are similar to other planes.   There is way too much false attribution of originality and "copying"
inferences.  


Not so similar now.

Sorry but i didn't see anything even vaguely similar in this two.
Wing is completely different, f-23 has no horizontal tail, engine placement is completely different.

Sorry, when I see a Su-57 I see the successor of the Su-27 design, when I see the F-22 a successor of F-15 and when is the case of J-20 i see an evolution of J-10 and J-9.
YF-23 bear IMHO instead just a vague influence from the SR-71.
When I see an F-35 instead, i just feel sick.

Fair take.

Everyone sees things a bit differently. Just for kicks, here's that short article from Wingswarworld.

Is Russia’s Latest Fighter Stolen From An American Design? – What Does The Evidence Say?

PAK Widow.

In the early 1990s, several companies were fighting their way to the top of a competition for the next fighter jet. In the end, it came down to two respective jets the Lockheed YF-22 and the Northrop YF-23. The United States Government selected the YF-22 which evolved into the Lockheed Martin F-22 and the YF-23 was forgotten, or so we thought.

Many considered the Northrop YF-23 to the superior fighter and that the YF-22 was only selected because it operated better at lower speeds. Then in 2009, the Russians unveiled the Sukhoi PAK FA, their most advanced fifth-generation fighter and it bore a striking resemblance to the YF-23. At first sight, everyone thought this design was stolen because its features are so incredibly similar.

While there are some similarities between the two aircraft, there has been no direct link to stolen plans or leaked information. The PAK FA seems to be a merger of the Sukhoi Su-27 and the Northrop YF-23. Of course, this hasn’t stopped the theories of theft and leaks of F-22 tech falling into the hands of the Chinese which gave way to the Chengdu J-20.

The PAK FA is proceeding ahead into development with a new designation the Sukhoi Su-57. What do you think, is there evidence to support Russia stealing the design or was it mere coincidence?

marcellogo wrote:

kvs wrote:

miketheterrible wrote:I think the reason was that they never used the YF was because
1) more expensive
2) Lockheed Martin has a stronger influence in US politics.

YF-23 was a rather good design and it wouldnt be a bad idea to grab some influence designs from it.

Most planes are similar to other planes.   There is way too much false attribution of originality and "copying"
inferences.  

[img]

[img]

Not so similar now.

Sorry but i didn't see anything even vaguely similar in this two.
Wing is completely different, f-23 has no horizontal tail, engine placement is completely different.

Sorry, when I see a Su-57 I see the successor of the Su-27 design, when I see the F-22 a successor of F-15 and when is the case of J-20 i see an evolution of J-10 and J-9.
YF-23 bear IMHO instead just a vague influence from the SR-71.
When I see an F-35 instead, i just feel sick.

About to say the same thing. The Su-57 is a lot more reassemble the flanker than the black widow.
If anything look similar to YF-23 its may be the all moving vertical tail, but YF-23 has no horizontal tail anyway.

kvs wrote:
The F-22 is really a gen 5- design hyped to the level of a 5+.  

So if the F-22 is a 5+ generation fighter, what tier is the Su-57 at? The 6th generation Su-57 surpasses the F-22 in every respect.

I dunno if its full retard. Copy accusations are just fun.  If you had to pick an aircraft that shared the most similarities with the su 57, it would have to be the YF-23. They are both true blend wings.

Yeah, people in the west like to show pictures of German rifles and Soviet rifles and claim the Soviet rifles are copies of German rifles despite German semi auto rifles being shit... and only fixed after they got a good look at some Tokarevs which they openly admit they copied... they ignore previous Russian rifle designs which contain features of that German rifle and predate it from which the Soviet rifle could be using as a basis...


You can show images of the failed YF-23 together with the PAK FA, but you also need to show images of all the other design models they worked on and of course the Su-27, which the YF-23 looks like it is based on... which originally derives its shape from the MiG-25 which spawned the F-15 and F-22.... even the F-35 is a single engined F-22 really...

I think the reason was that they never used the YF was because
1) more expensive
2) Lockheed Martin has a stronger influence in US politics.

YF-23 was a rather good design and it wouldnt be a bad idea to grab some influence designs from it.

Actually the F-22 was chosen because it was more conservative and also slightly less stealthy. It is essentially a stealthy F-15. Ironically if the F-35 was just a stealthy F-16 it would actually be much much better....

In fact I wish I could have seen the documents if Russia did help the Chinese out.

This is not charity. China would have paid MiG for the designs, so they are theirs to do as they please... for China, if you have the ability to buy the expertise of one of the few companies on the planet able to design and build 5th gen stealth aircraft why wouldn't you get them to design something for you?

Wonder if there were even more advanced iterations of the mig that might still be classified by Russia.

We will likely see soon enough with the MiG LMFS...

The PAK FA is proceeding ahead into development with a new designation the Sukhoi Su-57. What do you think, is there evidence to support Russia stealing the design or was it mere coincidence?

Yeah, like S-300 is based on stolen Patriot technology and of course Zircon is actually a subsonic low flying Tomahawk replica...

Why would Russia copy the F-22... they want something to defend Russia, not to invade North America with... they are fundamentally different aircraft... the Russian aircraft is designed to destroy stealth fighters, F-22 and F-35 are designed to operate in 1980 and shoot down 4th gen fighters in large numbers... by flying high and fast and firing from outside WVR combat distance...

China can send rover to the Mars and sample collector back from the moon. Russia can't.

Russia has, and is preparing to launch to Venus... a much more difficult environment...

As far as warships, only 2 Russian warships, the Gorshkov frigates, can compete with Type 052D and Type 055 in terms of technology, not to mention Chinese carriers which are equipped with AESA make the Russian carrier look vintage.

Except Russian corvettes can carry missiles no Chinese or any other ship could stop, whereas generally their air defence performance on Russian ships is pretty good... even on their older ships.

So if the F-22 is a 5+ generation fighter, what tier is the Su-57 at? The 6th generation Su-57 surpasses the F-22 in every respect.

It is a 5th gen fighter that deserves its place.

Arrow wrote:

kvs wrote:
The F-22 is really a gen 5- design hyped to the level of a 5+.  

So if the F-22 is a 5+ generation fighter, what tier is the Su-57 at? The 6th generation Su-57 surpasses the F-22 in every respect.

Plerase, leave that gen thing away.
Either in 4 gen there was a great difference between earlier ones (the USAF teen fighter) and the immediately successive ones (F/a-18, MiG-29 and Su-27) in terms of handling High AoA.
Also there a consistent difference is made by athe same legacy thing I mentioned in my earlier post: F-22 being the successor of F-15 was designed as a dedicated A2A fighter and thus as a consequence shifted heavily the "multirole" F-35 toward A2G ones, same happened with J-20 while the previous experience with the block buster Su-30 made the design of Su-57 with its well designed bomb bay a true all around plane.

GarryB wrote:

.[/quote]

What is that thing now ? It almost looks like a smoothed over F-117 . It's a bottom wing but the intakes are underneath.

Backman wrote:

GarryB wrote:

.

What is that thing now ?    It almost looks like a smoothed over F-117 . It's a bottom wing but the intakes are underneath. [/quote]

That's the Nth iteration of the LMFS which should have been given Priority instead of the SU-57. Alas the PAK FA got first place and Russia is forced to overextend a great 80's plane lifespan. Mig29.

KoTeMoRe wrote:

Backman wrote:

GarryB wrote:

.

What is that thing now ?    It almost looks like a smoothed over F-117 . It's a bottom wing but the intakes are underneath.

That's the Nth iteration of the LMFS which should have been given Priority instead of the SU-57. Alas the PAK FA got first place and Russia is forced to overextend a great 80's plane lifespan. Mig29.[/quote]

You mean high/low mix wise ? Russia's forced to overextend the low mix with the Mig 29 ?

Backman wrote:

KoTeMoRe wrote:

Backman wrote:

GarryB wrote:

.

What is that thing now ?    It almost looks like a smoothed over F-117 . It's a bottom wing but the intakes are underneath.

That's the Nth iteration of the LMFS which should have been given Priority instead of the SU-57. Alas the PAK FA got first place and Russia is forced to overextend a great 80's plane lifespan. Mig29.

You mean high/low mix wise ? Russia's forced to overextend the low mix with the Mig 29 ?


[/quote]

Russia's defense doesn't need PAK FA in absolute terms. It needs point defense fighters like the Mig which are cheaper and can be produced faster. Instead they're embarked into double trouble with two expensive fighters (Su-27/57 family) which don't allow for a release of the venerable SU-24.

[quote="KoTeMoRe"][quote="Backman"][quote="KoTeMoRe"]

Backman wrote:

GarryB wrote:

.

Russia's defense doesn't need PAK FA in absolute terms. It needs point defense fighters like the Mig which are cheaper and can be produced faster. Instead they're embarked into double trouble with two expensive fighters (Su-27/57 family) which don't allow for a release of the venerable SU-24.

That's an interesting point. They could have just used to su 35 has the heavy fighter and produced a punchy Mig 29 with a stealth skin.

I just wonder how much cheaper it could have been to develop or manufacture.  

What is that thing now ? Wink It almost looks like a smoothed over F-117 . It's a bottom wing but the intakes are underneath.

The wobblin goblin was a subsonic cruise missile with two bombs inside as warheads... this model is clearly a fighter design to turn and manouver and shoot things down.

The bottom mounted air intakes alone suggests high AOA is expected...

That's the Nth iteration of the LMFS which should have been given Priority instead of the SU-57. Alas the PAK FA got first place and Russia is forced to overextend a great 80's plane lifespan. Mig29.

I disagree, a big 5th gen fighter is more useful than a smaller one... and unless the new LMFS is exceptional they might find a simpler high low mix will be big 5th gen fighter and medium size 4+++ gen fighter because an all 5th gen fighter fleet is neither affordable because of maintenance issues, nor desirable because most issues don't require stealth as such.

The MiG-29 deserved a proper upgrade and will remain a useful aircraft for as long as any of the upgraded western 4th gen fighters... simply fitting Su-35s and MiG-35s with 5th gen equipment will keep them relevant... but eventually taking the cockpits out and making them drones could be their ultimate future as weapon trucks.

You mean high/low mix wise ? Russia's forced to overextend the low mix with the Mig 29 ?

I think the Su-35 and Su-30 and MiG-35 will occupy the low mix and the new 5th gen fighters will be the high mix... but in any case all their fighters need a decent operational radius of action so they really wont have a high and low mix.... more a high and medium.

Their operational costs is what actually matters and they seem to be a fraction of the cost of most western aircraft.

Russia's defense doesn't need PAK FA in absolute terms. It needs point defense fighters like the Mig which are cheaper and can be produced faster. Instead they're embarked into double trouble with two expensive fighters (Su-27/57 family) which don't allow for a release of the venerable SU-24.

I don't agree... bigger planes have more growth and performance potential... and they don't need 10,000 fighters... and if they did they could be making MiG-29M2s, but they seem to be ordering MiG-35s instead.

That's an interesting point. They could have just used to su 35 has the heavy fighter and produced a punchy Mig 29 with a stealth skin.

I just wonder how much cheaper it could have been to develop or manufacture.

The price depends on who is buying but the Su-35 and Su-57 both look to be rather cheaper than Rafales for export and F-35s for domestic and export use too...

Which is just as well because Russia just can't afford to piss money away like the west does.

They never stated any goals for an all stealth fleet and I don't think they ever planned for an all Flanker or all Fulcrum fleet, and all stealth fleet either.

The Su-35 and MiG-35 are not backups, they are the numbers aircraft I suspect, while the Su-57s and LMFS will be the point of the spear that rips the guts out of the attacking enemy while the nonstealthy aircraft will be the bomb trucks for later when their stealth aircraft start carrying external weapons too.

LMFS wrote:It can be both, depending on the position of the plane re. the CoG. If the first is higher than the second, the anhedral will be actually stabilising. But probably your theory below is better.

I'm not sure what you exactly mean by "first" and "second", but this video provides very nice explanation of the problem:

LMFS wrote:It does not have the vortexes of close coupled canards but they probably compensated for that with the small LERX right besides the LEVCONs, in general I think the layout of the PAK-FA is very smart and a very good compromise.

Yes, but I don't think that the PAK FA's LERX is actually small.
I had this debate few years back at the F-16.net forum where they have claimed that the PAK FA's LERX is about the same in size as F-35 chines and that it is inferior in producing the effects of the "real size " LERX, which is actually not correct.



Here we have the PAK FA and the Su-35S for comparison.
The framed part represents the LERX in both planes, where the LEVCON [in the case of PAK FA] itself is an integral part of the big [cranked-arrow] LERX, but as it happens it represents the movable part of the whole unit.

They also argued that the LEVCON's don't produce the vortices and can't be considered as LERX, which is also not true!



We can see that at very high AoA LEVCON-LERX combo is producing extremely powerful vortices, and the tip of the vortices is generated by the LEVCON's. As the AoA is decreasing, the tip of the vortices is transwering to the LERX, and since the LEVCON is at lower AoA, it is not generating the vortices at that flight condition.





LEVCON can "feed" the LERX with additional air stream at extremely high angles of attack not possible without it [and at the same time producing the vortices]. That way the stall boundary is expanded and the plane is not losing the lift even at very high AoA compared to classical approach.
Also, lift to drag ratio is better compared to fixed LERX because the LEVCON deflection is delaying the flow separation [reducing the pressure drag] and the intensity of the vortices [that create huge amount of drag] is less pronounced because of that.

For the same reasons [and the fact that it doesn't have negative effects associated with the downwash] I also think that this solution is more aerodynamically efficient than the use of the canards, but can't claim that with 100% certainty.

GarryB wrote:

What is that thing now ? Wink It almost looks like a smoothed over F-117 . It's a bottom wing but the intakes are underneath.

The wobblin goblin was a subsonic cruise missile with two bombs inside as warheads... this model is clearly a fighter design to turn and manouver and shoot things down.

The bottom mounted air intakes alone suggests high AOA is expected...

That's the Nth iteration of the LMFS which should have been given Priority instead of the SU-57. Alas the PAK FA got first place and Russia is forced to overextend a great 80's plane lifespan. Mig29.

I disagree, a big 5th gen fighter is more useful than a smaller one... and unless the new LMFS is exceptional they might find a simpler high low mix will be big 5th gen fighter and medium size 4+++ gen fighter because an all 5th gen fighter fleet is neither affordable because of maintenance issues, nor desirable because most issues don't require stealth as such.

The MiG-29 deserved a proper upgrade and will remain a useful aircraft for as long as any of the upgraded western 4th gen fighters... simply fitting Su-35s and MiG-35s with 5th gen equipment will keep them relevant... but eventually taking the cockpits out and making them drones could be their ultimate future as weapon trucks.

You mean high/low mix wise ? Russia's forced to overextend the low mix with the Mig 29 ?

I think the Su-35 and Su-30 and MiG-35 will occupy the low mix and the new 5th gen fighters will be the high mix... but in any case all their fighters need a decent operational radius of action so they really wont have a high and low mix.... more a high and medium.

Their operational costs is what actually matters and they seem to be a fraction of the cost of most western aircraft.

Russia's defense doesn't need PAK FA in absolute terms. It needs point defense fighters like the Mig which are cheaper and can be produced faster. Instead they're embarked into double trouble with two expensive fighters (Su-27/57 family) which don't allow for a release of the venerable SU-24.

I don't agree... bigger planes have more growth and performance potential... and they don't need 10,000 fighters... and if they did they could be making MiG-29M2s, but they seem to be ordering MiG-35s instead.

That's an interesting point. They could have just used to su 35 has the heavy fighter and produced a punchy Mig 29 with a stealth skin.

I just wonder how much cheaper it could have been to develop or manufacture.

The price depends on who is buying but the Su-35 and Su-57 both look to be rather cheaper than Rafales for export and F-35s for domestic and export use too...

Which is just as well because Russia just can't afford to piss money away like the west does.

They never stated any goals for an all stealth fleet and I don't think they ever planned for an all Flanker or all Fulcrum fleet, and all stealth fleet either.

The Su-35 and MiG-35 are not backups, they are the numbers aircraft I suspect, while the Su-57s and LMFS will be the point of the spear that rips the guts out of the attacking enemy while the nonstealthy aircraft will be the bomb trucks for later when their stealth aircraft start carrying external weapons too.

2 things.

Look at the recent procurement of the VVS and VKS.

There are 4 yes 4 light fighters. Most SMT's were purchased almost 8 years ago. In total Russia has less light fighters than Turkey FFS (about 120). It more than compensates with the SU-27 family (over 300) but the need for a point fighter is clear. Local troublions like Turkey don't need to get taken head on by the PAK FA or SU-30/35.

Then you check the Quack of Doom (Su-34) numbers and you see that the replacement of the Su-24 is not possible (they're at the same level). Russia needs a ~300 strike fleet to spread through military regions.

The Su-34 is a lot more capable than the Su-24. To a degree where it does not need to be replaced in a 1:1 ratio.
Avionics aside the Su-34 has more range, higher ceiling, higher speed, etc. Also slightly more payload.
With precision munitions the terminal effects are increased, you have better range, so you don't need as many aircraft.

I think it was a much better idea to get the Su-57 vs the LMFS. It has higher export potential for one. The US won't export the F-22 and the line was closed.
The F-35 does not compete with the Su-57 in terms of performance.
Also, since you need to have internal bays for stealth a larger fighter gets you more usable payload.

Russia needs an aircraft with long legs which can be easily deployed from one theater of operations to another. Not a short legged point defense fighter.
Those will, I think, end up getting replaced with drones which don't require as much pilot training since a lot of the functions will be automated.

If it was a single engine aircraft like the MiG-21 then it might make sense. But if it is another twin engine aircraft it will be nearly as expensive as Su-57 without the same performance.

1st (2nd) serial production unit  

Edit: already posted... oh well, such is life

First serial-produced Su-57 fighter to be delivered by year’s end

The Su-57 is a fifth-generation multirole fighter designed to destroy all types of air, ground and naval targets

MOSCOW, December 7. /TASS/. The first serial-produced Su-57 fighter with the operational first-stage engine will be delivered to the Defense Ministry of the Russian Federation before the end of the year, chief executive of the state-run Rostec corporation Sergei Chemezov told journalists.

"In the near future, literally before the end of the year, we should deliver a serial-produced aircraft with the first-stage engine. It complies with all of the characteristics required of the fifth-generation aircraft," he said.

He also specified that all works on the Su-57 are conducted according to the schedule. "We have already delivered 10 aircraft as a trial batch, they functioned successfully. Now the implementation of a state contract on the delivery of 76 aircraft is underway," the Rostec CEO said.

The Su-57 is a fifth-generation multirole fighter designed to destroy all types of air, ground and naval targets. The Su-57 fighter jet features stealth technology with the broad use of composite materials, is capable of developing supersonic cruising speed and is furnished with the most advanced onboard radio-electronic equipment, including a powerful onboard computer (the so-called electronic second pilot), the radar system spread across its body and some other innovations, in particular, armament placed inside its fuselage.

https://tass.com/defense/1231999

PeregrineFalcon wrote:I'm not sure what you exactly mean by "first" and "second", but this video provides very nice explanation of the problem

The first is the plane, the second the CoG. If the plane with anhedral is higher than the CoG it contributes to stability.

Yes, but I don't think that the PAK FA's LERX is actually small.

Good find again. An initial analysis would say you have two elements there, the LEVCON which acts most of the time as a LE flap, and the chine which would be a reduced size LERX. But the video proves the type of optimization that could be expected of Sukhoi-TsAGI but needed proof, that is, that there is a synergy between both and the vortexes can be transferred from one to the other, it appears to be a highly dynamical process. Agree on the rest of your comments and that was the bottom line of my argument too, that the use of the LEVCONS allows to keep the flow over the lifting body attached with a much smaller use of high-drag causing LERX. Probably this is going to help big time in supersonic flight and maybe also with excess power and acceleration in general. Remember we did not find that video you referred about Bodgan explaining the superior performance of Su-57 vs -27, but I do remember him saying how much attention the pilot needs to have to avoid going supersonic without even noticing. Him being used to pilot the -35, the difference needs to be more than marginal, and the thrust difference between those engines (izd. 117 vs 117S) is not really big.

For the same reasons [and the fact that it doesn't have negative effects associated with the downwash] I also think that this solution is more aerodynamically efficient than the use of the canards, but can't claim that with 100% certainty.

I think the fact that it is not an additional LE to take care of in terms of RCS, as canards normally, is a nice advantage for a VLO plane. In terms of aero I am also not sure because I understand the close coupled, elevated canard provides more energy to the boundary layer similarly to how a LE slot would beat a normal LE flap. But probably the LEVCON is less draggy at reduced deflection angles and most of the vortexes as we see happen actually at the chines, which would be there nevertheless. So in fact this is a very clever design for a supercruising plane, as far as I manage to grasp.

Arrow wrote:

This was posted some time before but the picture had not been processed so heavily, I don't even know if people realized that the blocker was supposed to be there...

1st (2nd) serial production unit thumbsup

Edit: already posted... oh well, such is life

This is the one that crashed...

lancelot wrote:The Su-34 is a lot more capable than the Su-24. To a degree where it does not need to be replaced in a 1:1 ratio.
Avionics aside the Su-34 has more range, higher ceiling, higher speed, etc. Also slightly more payload.
With precision munitions the terminal effects are increased, you have better range, so you don't need as many aircraft.

I think it was a much better idea to get the Su-57 vs the LMFS. It has higher export potential for one. The US won't export the F-22 and the line was closed.
The F-35 does not compete with the Su-57 in terms of performance.
Also, since you need to have internal bays for stealth a larger fighter gets you more usable payload.

Russia needs an aircraft with long legs which can be easily deployed from one theater of operations to another. Not a short legged point defense fighter.
Those will, I think, end up getting replaced with drones which don't require as much pilot training since a lot of the functions will be automated.

If it was a single engine aircraft like the MiG-21 then it might make sense. But if it is another twin engine aircraft it will be nearly as expensive as Su-57 without the same performance.

Agree. At this point I don't sure if the VKS still need lighter tier 5th gen fighter.
It's unlike the TPFI-LPFI time, today's technological enable the tactical requirement of both tier could be met with one plane.

If Su-57 and LMFS will be comparable advancement in avionic and design, I doubt the latter will cheaper (to procure and to operate) enough for VKS to bother operate two different planes for similar role.
Especially with lastest information suggest it will be twin engines, not single.

It's also easier to maintenance planes with similar design, similar subsystems, similar suppliers.
Which will be increased combat readiness of the whole fleet.

Moscow. December 7. Interfax - The "second stage" engine, which ensures the cruising supersonic speed of the Su-57 fighter, will be ready in 2022, the head of Rostec Sergey Chemezov told reporters.

“I hope that sometime in 2022 the engines will be ready,“ put on the wing, ”and within a few years we will launch their serial production,” Chemezov said.

https://www.militarynews.ru/story.asp?rid=1&nid=542823&lang=RU

The SU-57 in 2022 will still have the same engine.

lancelot wrote:The Su-34 is a lot more capable than the Su-24. To a degree where it does not need to be replaced in a 1:1 ratio.
Avionics aside the Su-34 has more range, higher ceiling, higher speed, etc. Also slightly more payload.
With precision munitions the terminal effects are increased, you have better range, so you don't need as many aircraft.

I think it was a much better idea to get the Su-57 vs the LMFS. It has higher export potential for one. The US won't export the F-22 and the line was closed.
The F-35 does not compete with the Su-57 in terms of performance.
Also, since you need to have internal bays for stealth a larger fighter gets you more usable payload.

Russia needs an aircraft with long legs which can be easily deployed from one theater of operations to another. Not a short legged point defense fighter.
Those will, I think, end up getting replaced with drones which don't require as much pilot training since a lot of the functions will be automated.

If it was a single engine aircraft like the MiG-21 then it might make sense. But if it is another twin engine aircraft it will be nearly as expensive as Su-57 without the same performance.

The Duck of Doom is another beast than the SU-24. Including payload.

Precision strikes don't change the problem. With a typical rotation and attrition you need those 300 SU-34 (Current is 250 AC between SU-24 and Su-34). Russia is a large country. You got two issues. Air time and coverage.