SU-57: On hold for a decade

[mixelflick]

At what point do they have to stop adding stuff to it though?

Every time I turn around, the SU-57 is getting new A2A, A2G weapons, new radars, lasers, avionics and missions. I have a hard time believing all of this has been tested and the bugs worked out. If it was me, I'd be simplifying - not perpetually adding things.

In any case, how likely do you think production birds will be deployed to Syria? The first time was obviously a publicity stunt, but I'd think a more meaningful/longer deployment would be the fastest way to get all the bugs out?

[southerncross]

Good read about the first Russian SU-57's..

https://theaviationist.com/2019/08/01/s ... ealth-jet/

Thanks for the link. I would just warn against sources that make claims about technical characteristics which are strictly classified. Most of them come from people that are respected like Piotr Butowsky but have no way of knowing or disclosing certain info. Cruising speed with the 2nd. stage engine drew my attention in particular. Izd. 30 is meant as a supercruising engine, that means, an engine of high specific thrust like F119. AL-41F1 is not that far from F119 in wet settings but what it clearly lacks is dry thrust, hence why it cannot fulfil the requirements and will be substituted. It would not make much sense that the F-22 can cruise at close to Mach 1.8 while Su-57 stays at 1.3, it is not technically justified or reasonable as design goal IMHO, much less when an engine is going to be designed specifically for supercruising.

Re. the further development of the Su-57, Sukhoi has their roadmap for continuous improvement, not unlike F-35. We just don't know at what time what will go into the series and when retrofits will happen, but their MO is to work steadily to create what they call technical reserve. The plane is stated as going to be the backbone of VKS for 40 or 50 years so this effort will continue unabated for decades to come, as it happened with the Flankers. We recently got wind of the new MRAAM with claimed range of 200 km and new aero layout for improved maneuverability which had been on the works for years without anybody saying a peep about it, this is business as usual for Russian MIC. Very active in design but not so much in procurement unless needed, probably to save as much money as possible.

[milosh]

At what point do they have to stop adding stuff to it though?

Every time I turn around, the SU-57 is getting new A2A, A2G weapons, new radars, lasers, avionics and missions. I have a hard time believing all of this has been tested and the bugs worked out. If it was me, I'd be simplifying - not perpetually adding things.

Adding stuff?!?

Look man, sensor package is same as it was in 2010 when bird was presented. In fact some sensors aren't still developed, like target pod, even though it was showed on MAKS years ago.

New weapons? We really don't know what Su-57 can carry right now, it could be what you say and that is A-A package. I wouldn't be surprise if it can carry R-37M, R-73 or R-74, R-77M, KH-38, KH-58 and KH-59MK2.

Of all of those only KH-59MK2 and R-74 are new. Everything else are already developed weapons.

Good read about the first Russian SU-57's..

https://theaviationist.com/2019/08/01/s ... ealth-jet/

Text is wrong in part about engine, 117 isn't uprated 117S in Su-35. 117 is different engine with new turbine with better cooling, as here is nicely explained:
https://youtu.be/JVJny6UL6V8?t=272

[mixelflick]

southern cross

"It would not make much sense that the F-22 can cruise at close to Mach 1.8 while Su-57 stays at 1.3, it is not technically justified or reasonable as design goal IMHO, much less when an engine is going to be designed specifically for supercruising."

OK... what are you trying to say here exactly?

Do you mean it's unacceptable the SU-57 can only make mach 1.3 vs. the Raptor's 1.8? And if so, can it do 1.3 with the current engines? Or can it not super-cruise at all with the current engines?

Or, do you mean to say it isn't reasonable the SU-57 can only get to mach 1.3 with the new, 2nd stage engine? That engine should be able to propel it to at least Mach 1.8??

Confused...

[southerncross]

OK... what are you trying to say here exactly?

Sorry, I was not clear.

IMHO it is possible that the Su-57 can marginally supercruise with the current engines, but the whole point of the second stage ones is at least to get in the same ballpark as the F-22. This high performance in supersonic flight is crucial in every analysis of 5th gen fighters I have seen from Russian sources, stated in the patent and present in the obvious aero traits of the plane.

In terms of thrust, izd. 117 should be around 9 tf dry, which falls clearly short of the stated 11-11.5 tf of the the F119 (could be more IMO). This is due to inherent design characteristics (bypass ratio more than pure technological differences), so this thrust gap cannot be bridged unless Russia changes the relatively high bypass ratio of the AL-31F family in the izd. 30 design. The later is quoted as having highest specific thrust of any comparable engine, which supports this assumption and, given a similar size to F119 and if intakes are an indication of airflow consumption, it should have at least same dry thrust. Such levels are very close to the 12-12.5 tf wet thrust of engines like AL-31F or F110 that propel Flankers and F-15 above 2 M. So it is consistent that F-22 and Su-57 can cruise reasonably close to such speeds, even when I am admittedly no engine expert and may be differences at high speed and high altitude between operating in AB and military settings I am not aware of.

Hope the point is clearer now

[milosh]

Is Russians anywhere mentioned what super cruise speed they are wanting? I understand fanboys would love it match F-22 but to me it is more less pointless. What is wrong with Mach 1.3-1.5 but being able to fly most of mission on that speed.

[southerncross]

Is Russians anywhere mentioned what super cruise speed they are wanting? I understand fanboys would love it match F-22 but to me it is more less pointless. What is wrong with Mach 1.3-1.5 but being able to fly most of mission on that speed.

Not that I know, and the only half-serious reference I know about the plane's speed is a claimed limitation to 2 M, which finds itself in serious conflict with objective design features like the adjustable intakes that only make real sense for planes travelling faster than such speed. Having said that:

1. It is rather obvious that the F-22 set the bar and everyone coming afterwards needs to meet that speed, in order not to start an uphill battle when confronting it, at least from a kinematic point of view. Reason are the smallish chances to defeat the adversary when they get free shots at you from outside of your engagement range, due to longer range of their missiles and weak starting position of the own ones when pursuing such a fast, high flying maneuvering target. You can see in the thread about Spurs' fighter analysis what a disproportionate effect the launch conditions have on the performance of the AAMs. To put it in short, it would make little sense to make such a huge effort developing a tool to kinematically confront the F-22 and then give it a cruising speed that puts it at a marked disadvantage in the fight.

2. As said above, if the engine has broadly the same size and higher specific thrust, it will have very close to or higher thrust in dry settings. Since frontal area is almost the same and drag coefficient should not be apart by big amounts in fighters designed both for supercruising, speed should be similar. This is rather a technical consideration and has little to do with fanboyism IMO, but I stand to be corrected by the people in the know here. In other words, I would struggle to see how Su-57 could be so much slower than F-22 when the circumstances above are considered.

3. Two "leaky" turbojets as F119 and izd. 30 will have, as far as I see it, not too different fuel consumptions when cruising in supersonic flight, so the difference in range would come mostly from internal fuel reserves. We assume the Su-57 will carry more fuel than F-22, but we have no hard data on that regard, apart from claims in the patent that the long range supersonic flight is indeed one of the design goals. Anything else is speculation, as far as I see it.

[mixelflick]

It's a pretty safe bet that the SU-57 will carry more internal fuel IMO.

This is largely a consequence of Russia being an enormous country, but even moreso Russia's rather small and rudimentary tanker fleet. It's also due to the fact most Russian engines are a lot more thirsty than their American counterparts. This is also the reason China deploys many a Flanker variant, never once even considering the Mig-29. They have an even smaller tanker fleet than Russia, and the SCS demands long legs.

I'd guess somewhere around 24-25,000lbs of fuel internal for the SU-57. And we've also seen big external tanks, although I doubt outside of some Chinese examples we'll see that configuration often..

[sprstdlyscottsmn]

I'd guess somewhere around 24-25,000lbs of fuel internal for the SU-57.

I have a lot of doubts about that. When I look at the layout, compared to the F-22, I just don't see where they are going to put all that fuel. I could be wrong though, it doesn't look like the F-16 could possibly have 7k but it does.

[milosh]

I'd guess somewhere around 24-25,000lbs of fuel internal for the SU-57.

I have a lot of doubts about that. When I look at the layout, compared to the F-22, I just don't see where they are going to put all that fuel. I could be wrong though, it doesn't look like the F-16 could possibly have 7k but it does.

You are probable right, it I remember good they mentioned 10tons of fuel, which is ~22k lbs if my math is right.

[southerncross]

It's a pretty safe bet that the SU-57 will carry more internal fuel IMO.

I would personally agree with you, but we don't have hard data as far as I know, only hints.

This is largely a consequence of Russia being an enormous country, but even moreso Russia's rather small and rudimentary tanker fleet.

Relying on tankers is a source of complexity and vulnerability and will IMO never be such a high priority for Russia as it is for US. They focus mainly in fighting against peer rivals that they know could down their tankers.

It's also due to the fact most Russian engines are a lot more thirsty than their American counterparts.

Can you name an American fighter engine with lower TSFC than that of the AL-31F?

I'd guess somewhere around 24-25,000lbs of fuel internal for the SU-57. And we've also seen big external tanks, although I doubt outside of some Chinese examples we'll see that configuration often..

I would tend to agree on that figure, based on what the Su-35 can carry it would be only logical that VKS demands from their newer plane to have legs at least as long as those of their current fighters. The patent explains the integral aerodynamic design (blended wing-body) as a way to get maximum internal fuel with minimum downsides, and they really took this design principle to great lengths in the PAK-FA.

About the tanks, they are in general only used in Russian Flankers, already today, for ferry flights. This saves them the cost of dropping them.

I have a lot of doubts about that. When I look at the layout, compared to the F-22, I just don't see where they are going to put all that fuel. I could be wrong though, it doesn't look like the F-16 could possibly have 7k but it does.

You have the professional competences to make a better estimation, but comparing with the Flanker design I think they could manage to get to similar fuel capacities:

- The Su-57 is slightly smaller in linear dimensions, but overall has bigger horizontal surface and lots of usable volume, like in the lifting body of greatly extended dimensions, the wings with lower aspect ratio that allow bigger thickness without negative effects on the supersonic drag (per patent's claim) and a big, tall dorsal tank
- Sukhoi managed to get 11.3 t (24.900 lb) fuel from the Su-35S, improving substantially from the previous Flanker models. Su-57 has even more advanced systems and avionics that will leave more free space for fuel.
- Weapons bays do undoubtedly detract from fuel, but Flankers didn't have a body of comparable thickness either. It is apparently possible (not officially stated AFAIK) to use the main WB to carry fuel on special tanks.
- The F-22 has IMHO several features that detract substantially from its internal fuel capacity, even when they are justified design decisions: 1) Big side bays, needed to carry the old Sidewinder models 2) S-shaped air ducts that go along the whole fuselage 3) A very compact design unlike the BWB, podded-engine layout of the Su-57 4) Short fuselage with the engines placed relatively forward, well hidden by the tail.

You are probable right, it I remember good they mentioned 10tons of fuel, which is ~22k lbs if my math is right.

Do you have a source? I have never seen any official statement in this regard.

In the end, the really interesting topic about Su-57 and izd. 30 regarding range and fuel consumption is whether the engine will be a two-stream variable bypass engine like its "predecessor" the izd. 20. This seems supported by the manufacturer's claims that it will keep the TSFC of the AL-31F, which seems incompatible with the low-bypass layout defining of supercruising engines. That would make it capable both of long loitering time / long subsonic range and at the same time high MIL thrust required for highly supersonic cruise, a combination of characteristics which is IMO the crux of the whole matter.

[mixelflick]

AL-31F Specific fuel consumption:
0.790 lb/lbf/h (22.37 g/kN/s) dry
1.819 lb/lbf/h (51.53 g/kN/s) with afterburner

F100-PW-229
(MIL) 17,800lbs @ 0.726 lb/Hr/lb st
(MAX) 29,100lbs @ 2.060 lb/Hr/lb st

F110-GE-129
(MIL) 17,000lbs @ 0.745 lb/Hr/lb st
(MAX) 29,000lbs @ 1.900 lb/Hr/lb st

F414-GE-400
(MIL) 14,700lbs @ 0.840 lb/HR/lb st
(MAX) 22,000lbs @ 1.850 lb/HR/lb st

F119-PW-100
(MIL) 25,000lbs @ (~0.800?) lb/HR/lb st (Speculation varies between 0.600 - 0.860...)
(MAX) 37,000lbs @ (~1.950?) lb/HR/lb st

F135-PW-100
(MIL) 28,000lbs @ 0.886 lb/HR/lb st
(According to J@ne'$, but seems too high? 0.700 is more likely)
(MAX) 43,000lbs @ (~1.950?) lb/HR/lb st

So, 2 known with a lower SFC (F-100-229 and F-110 129) and 2 possible (F-119 and F-135). I'm using the mil power figures given the vast, vast majority of time aircraft will be operating in this realm (vs. supersonic, usually measured in minutes). Frankly, I'd be shocked if the F-119 and F-135 weren't lower than the AL-31F, given they came much later and are more advanced...

But I understand your point, there's at least 1 Russian engine that has a comparable SFC metric. Where things go awry for most Russian engines is the mean time between overhaul. Look at all of the problems the Indians have had with the AL-31 series in their Flankers. But that's another story for another day. I will give you this: Russian engine tech has come a long way...

[sprstdlyscottsmn]

The AL-31 series was a quantum leap in thrust and fuel economy in the same way the F100 was for the US. We are just at a time where another leap has occurred in thrust and TBO in the US and another leap in TSFC is on the horizon.

[milosh]

But I understand your point, there's at least 1 Russian engine that has a comparable SFC metric. Where things go awry for most Russian engines is the mean time between overhaul. Look at all of the problems the Indians have had with the AL-31 series in their Flankers. But that's another story for another day. I will give you this: Russian engine tech has come a long way...

Indians aren't only users of AL-31, others don't have similar problems which say something about Indians. Btw Indians try to maintain engines not fallowing official procedures, for example they replace oil for example which lead to engine damages.

@southerncross

You forget Su-35 have wet fins which Su-57 don't have, also Su-35 don't have weapon bays which take space which would be used for fuel. Su-35 sting is fuel only, while Su-57 sting have not so small radar or jammer.

My source is I think was some official person which said that in interview, Su-57 carry less fuel but that doesn't have impact on range in fact in combat configuration range of Su-57 is noticable better compared to Su-35.

[sprstdlyscottsmn]

Su-57 carry less fuel but that doesn't have impact on range in fact in combat configuration range of Su-57 is noticable better compared to Su-35.

This I have no problem believing. The Su-57 just isn't that deep, and where it is deep compared to the Su-35 is where the weapons bays are. The F-22 is clearly not fuel optimized, it is speed optimized, just like the Su-57 appears to be. It has a longer but flatter fuselage, but it also doesn't have four weapons bays and two intakes going through the body. I guess 18,000lb to 22,000lb wouldn't surprise me, but 24,000 would.