Future PLA combat aircraft composition

Inst said:

1/3. Cost of Su-35 is inflated for China because it comes with parts and support, i.e, as long as the Sino-Russian border is open the logistics just depends on trained PLAAF personnel.
2. The Su-57 is not intrinsically a problematic type to produce, given that it's, designwise, more or less a modified Su-35. The problem is money; the Russians can't finance the full-scale replacement of their Flankers and MiGs because of the damage done to the Russian economy.
4. Do we need to source the TV show again? It's around 800 million RMB. If you look at publicized costs of J-10As, the Chinese don't seem to enjoy a cost advantage in aerospace.
6. Except the counterpoint is that it's already compatible with Russian systems. The R-37M, for instance, is a very promising Russian missile. The Su-57 fundamentally lacks the same bay length issues that plague the J-20. Adding a second inventory of Russian munitions to PLAAF equipment reduces the chances of China simply having weapons EW-countered or lacking key capabilities. Missiles are currently a key weakness of the PLAAF, while the PL-15 is excellent, it's likely outranged by the AIM-260. Comparable Russian air-to-air missiles can reach 290 km range.
7. This is assuming again that the Su-57 sucks. You're looking at yet another long-ranged heavy air superiority fighter, but for a mediumweight price.
8. You're strawmanning. I'm not implying the J-20 is a failed system, I'm saying purchasing the Su-57 has nothing to do with it failing.
9. There are rumors extant that the Chinese will get a "6th" gen up by 2025. If such rumors are credible, the easiest way to do so is simply to upgrade the J-20.
10. Which doesn't preclude purchasing Su-57s, given that China will require time to get its production up to speed. Russia provides a second production source that alleviates pressure on the Chinese MIC. Russian Su-57 fixed costs (factory, suppliers etc) can be allayed by the usual Russian export market; i.e, Russian production doesn't have to cover China alone and "neutral" countries aiming to buy Russian to avoid purchasing American for 5th gen cover the rest of fixed costs on Chinese purchases.

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1/3. Now you're suggesting China make a large scale purchase of Su-57s without having the infrastructure, personnel and maintenance capabilities in the country to operate a fleet of Su-57s? You're digging a deeper hole for yourself for why such a purchase doesn't make sense.
2. I never said that the Su-57 is problematic to produce, I'm saying that between now and into the foreseeable future, by the time Russia's Su-57 orders have been fulfilled and are able to fulfill any hypothetical PLA Su-57 orders, whatever the costs are of J-20 and/or J-XY/J-35 would have also further reduced, making it dubious as to whether Su-57 will even be cost competitive to J-20s and/or J-XY/J-35 (assuming it even was in the first place, even looking at procurement alone).
4. Without clear cut cost breakdowns of equivalent aircraft and everything that goes with them, the numbers mean little to nothing, especially if it is for an aircraft that is only at the beginning of a potentially long production run.. So I definitively reject your notion that we know what the true equivalent costs of the aforementioned aircraft are next to each other.
6. This is a deflection. Regardless of whether Su-57 is compatible with Russian systems or not -- and this is assuming the PLAAF is even interested in Russian systems to begin with -- the Su-57 most definitely is not compatible with PLA systems and other aircraft and platforms and would require significant additional investment and work and time to enable that. By the way, the R-37M most definitely is not the equivalent of PL-15; the equivalent of PL-15 is K-77M, whose range most definitely is not 290km. Considering PL-15 is now a decade old from when it first began test fires and going on half a decade old in service, the PLA are obviously working
7. Whoever said the Su-57 sucks? The Su-57 is probably a perfectly good aircraft, but introducing it into the PLA in relation to other opportunity cost platforms that they could potentially acquire, in context of fleet wide requirements for maintenance, support, and operations, and system of systems warfare, means procuring Su-57 doesn't make sense.
8. I'm not strawmanning anything -- you're the one who first said in post #220 "It'd get around "J-20" failure claims"". I'm asking you what "failure claims" you're referencing and why you think it is reasonable to speak about those claims as if they are widely held.
9. I'm not sure what rumours those are, please provide a credible source. The most reliable indicators I've found in regards to PLA 6th gen efforts suggest that they will enter service before 2035. I've not seen anything credible regarding 2025 for a 6th generation fighter to emerge.
10. What you're describing here is purchasing a limited number of Su-57s as a supplement for 5th generation fighters as the PLA spins up production rates of J-20 and J-XY/J-35. That is very different to suggesting that the PLA should buy Su-57s en masse as "low end" 5th gen complement to J-20. If the procurement rate of J-20s and J-XY/J-35 was deemed strategically unacceptable, it might be possible that a purchase of Su-35s to make up the shortfall might be necessary, but would hardly be desirable or ideal.


For yourself, and for the others reading, I'll put my points clearly.
The below points are all ones which you are either unable to refute with current information, and the below which are all the current null hypotheses which require significant burden of proof for you to change otherwise:

A - We have no evidence as to what the true equivalent procurement cost of Su-57 vs J-20 vs F-35 are. Therefore you do not have the evidence to suggest Su-57 is cheaper than J-20 to procure.
B - We have no evidence as to what the true operating cost of Su-57 vs J-20 vs F-35 is. Therefore you do not have any evidence to suggest Su-57 is cheaper to operate than J-20. If anything, common sense and other recent trends in force structure and O+M costs tells us that introducing a new aircraft requires substantial costs in relation to its O+M infrastructure.
C - We have no evidence to suggest that the PLA is interested in Russian subsystems (weapons or sensors) that Su-57 may be compatible with. If anything, current and prior evidence in recent history overwhelmingly tells us the PLA is interested in integrating its own subsystems into any imported aircraft if possible.
D - Current Russian production of Su-57s will be tied up until the late 2020s for Su-57s for their domestic use, and Chinese production of J-20s and likely soon J-XY/J-35s will only further steam ahead in this time, likely outstripping Su-57s in scale and affordability.
E - PLA procurement of 4+ gen fighters are likely to continue in the next few years at least, in the form of SAC Flankers and continued J-10Cs.


In context of the above, it is absolutely reasonable if not inevitable to say that yes, Su-57 is a capable fighter and offers a unique set of capabilities for a 5th generation fighter, but does not offer significantly more capable systems or characteristics given the above industry and system points, to reasonably argue that the PLA Su-57s should be procured as a "low end 5th generation fighter".

===

As for your "long" response, the point is, if the Russians can deliver Su-57s at functional costs similar to Su-35s (i.e, would be higher, but with spares and logistics included), it's worth buying in bulk because it's worth it. RMB-RUB exchange rate is almost at its post-sanction high, given Russia's poor response to COVID-19. Once again, the main argument for purchasing Su-57s is the price.

===

To put it another way, if the Russians offer to sell China Su-57s at 50 million USD a piece (which is still lower than that of the F-35), with parts and support coming in as part of a different package, would it be worthwhile to buy it? How about 20 million USD, just as a hypothetical? How low does the cost of the Su-57 have to be before it'd appear reasonable to you for China to make a bulk purchase of Su-57s?

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I'm sure there are some hypothetical situations that may exist.

But in context of the current understanding of the above aforementioned null hypotheses, I don't see any reason why the PLA would be interested in purchasing Su-57s as a "low end 5th gen" force en masse.
Maybe the PLA will one day buy a dozen or two dozen Su-57s as DACT, and/or to throw Russia a geopolitical favour, and/or to see what the Russian MIC is cooking up at its leading edge.
Or, as I wrote above, if the procurement rate of J-20s and J-XY/J-35 was deemed strategically unacceptable, it might be possible that a purchase of Su-35s to make up the shortfall might be necessary, but would hardly be desirable or ideal. But we don't know what the PLA's aim for procuring 5th gen fighters is, nor do we know what the analysis of alternatives are if they are unable to procure J-20s and J-XY/J-35 to the rate they want -- i.e.: for all we know additional 4+ gens, and/or EW platforms +/- unmanned solutions might be more cost effective than procuring Su-57s.


So sure, there are hypothetical situations where it might be necessary or where it might make sense, but we don't have anything to suggest that is on the horizon or anything that suggests we can reasonable argue it is likely to happen at this stage.

Ultimately I'm not sure why you are so obsessed with the idea of the PLA purchasing Su-57s.
It's a fine fighter.
But it doesn't make sense for the PLA in the way you describe, with the information we have at present.

Bltizo said:

LRIP equivalent of J-XY/J-35 may begin 2025, or 2024 if they're fast. That would be a 9-10 year gap between LRIP of J-20.
By the time J-XY/J-35 begins production, there most definitely will be a 10 year gap.

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Basic model - FC-31v1 - flew in 2012. I.e. its design cycle went through the mid-late 2000s.
Fighter design may be updated, but until and unless they're more than superficially connected(low-cost program rumors strongly hint they are), connection will be here.

As of now, both airframes follow a surprisingly similar development schedule. J-20 program simply had consistently more money to play with. This doesn't hint at any ground-breaking tech for J-XY, which won't be available to the 20, available earlier at that.

Bltizo said:

in terms of aerospace industry the ability to mass produce WS-15s will likely prove more challenging than WS-19s in both of their initial/medium term phases given the larger blades of WS-15 compared to WS-19.

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The assumption that expansion of production of an engine (which, at least, is known to be much further into development) is more difficult than creation of a second, completely different 5th gen engine on top of the first one, and gaining >>2 output of two engine models vs <<2 for one model, is ... a bold one, in my opinion.

And, per specs&equipment, J-XY currently has no visible advantages over J-20 to justify it otherwise. This is the main problem for this a/c outside of PLANAF: sense. As per what we know, it simply lacks it.

Bltizo said:

- More sensible distribution of aerospace resources in context of SAC and CAC's other respective ongoing projects

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Let's get at least one operational and practical 5th gen engine first.

Furthermore - unlike many other countries, China has a relatively recent experience of producing single-engined fighter aircraft, there is no added difficulty here.

Inst said:

2. The Su-57 is not intrinsically a problematic type to produce, given that it's, designwise, more or less a modified Su-35.

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wat?

Gloire_bb said:

The assumption that expansion of production of an engine (which, at least, is known to be much further into development) is more difficult than creation of a second, completely different 5th gen engine on top of the first one, and gaining >>2 output of two engine models vs <<2 for one model, is ... a bold one, in my opinion.

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The design portion of the WS-15’s development is more or less complete at this point, assuming that the rumors about flight testing are true, and given that we have some pretty clear indications that they’re already doing batch production testing. Furthermore, the WS-19 will almost certainly use many design elements and components shared with the WS-15. They’re not pushing the envelope of their turbofan tech capabilities with the WS-19 like with the WS-15 so it really shouldn’t be treated as a project that brings any extraneous development risk or burdens.

Gloire_bb said:

Basic model - FC-31v1 - flew in 2012. I.e. its design cycle went through the mid-late 2000s.
Fighter design may be updated, but until and unless they're more than superficially connected(low-cost program rumors strongly hint they are), connection will be here.

As of now, both airframes follow a surprisingly similar development schedule. J-20 program simply had consistently more money to play with. This doesn't hint at any ground-breaking tech for J-XY, which won't be available to the 20, available earlier at that.

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My understanding from reading some of the insiders and looking at some articles from SAC suggests that the two FC-31 demonstrators have a significant role in demonstrating new production technologies.

The technology either inside an aircraft or production or maintainability technologies needed to build an aircraft IMO are best assessed when the aircraft enters LRIP rather than when the literal first flying test bed or tech demonstrator article flies.

After all, an aircraft is more than just an airframe -- it's also about the avionics, the production methods and scaling, the maintainability, the weapons systems, the cost etc, and the way those all combine together, and that complete picture only really begins to emerge when the aircraft finishes its development and starts LRIP or LRIP equivalent.

Gloire_bb said:

The assumption that expansion of production of an engine (which, at least, is known to be much further into development) is more difficult than creation of a second, completely different 5th gen engine on top of the first one, and gaining >>2 output of two engine models vs <<2 for one model, is ... a bold one, in my opinion.

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So, my impression for WS-19 is:
- at present it is behind WS-15 in development
- however, I expect its development to significantly catch up with WS-15 by the mid 2020s by virtue of relying on technology that WS-15 had already demonstrated but on a smaller scale
- when it comes to production, yes I am explicitly saying that by the mid to late 2020s, I think that expanding production of WS-15 to meet the demands of J-20s + potential early 6th gen + clean sheet medium weight fighter, may be more difficult than having production of WS-19 as parallel. This is because WS-19 is a lower thrust engine, with smaller blades (being arguably one of the most if not the most significant bottleneck) and thus likely to achieve higher yields than WS-15 which requires larger blades.

So IMO it isn't that bold to suggest that having dual production of WS-15 + WS-19 to meet demands of J-20 and 6th gen + J-XY/J-35 land based derivative, is more feasible than massively expanding production of WS-15 to meet demands of J-20 and 6th gen and clean sheet single engine design.

Gloire_bb said:

And, per specs&equipment, J-XY currently has no visible advantages over J-20 to justify it otherwise. This is the main problem for this a/c outside of PLANAF: sense. As per what we know, it simply lacks it.

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Increasing J-20 production compared to a land based variant of J-XY/J-35 would make sense, if they were able to develop a new variant of J-20 that integrates the new production techniques that J-XY/J-35 will have, as well as if the net operating footprint of the J-20 were able to be reduced down to what a J-XY/J-35 land variant would need, and if the work for increasing J-20 production could be spread out between SAC as well.... and if WS-15 production is able to keep up with the massively increased J-20 production.


In other words, if we're to compare land based J-XY/J-35 with an increased/modernized J-20 variant production, IMO the strengths of the J-XY/J-35 include:
- ultimately still a smaller aircraft, which will give it smaller operating footprint than J-20 and lower costs. It may not be "decisively" low in terms of cost from this aspect alone, but it is still a strength nevertheless
- J-XY/J-35 based on SAC documents should have more modern production techniques and based on rumours should have more maintainable stealth features as well than J-20, even if we are speaking of a new variant of J-20 developed to leverage those more modern production techniques etc, with benefits in costs as well.
- J-XY/J-35 will be powered by WS-19s, not WS-15s -- if you increase J-20 production, a massive increase in WS-15 production will be needed which will basically be a twice as more extreme version of the bottleneck for a hypothetical single engine clean sheet design.
- distribution of aerospace resources more wisely between SAC and CAC.

Strengths of both a land based J-XY/J-35 and increased/modernized J-20 variant production:
- both would be derivatives/continuations of an existing aircraft and would benefit from likely similar risk and time from program start to entry into service
- both would be able to leverage common subsystems and infrastructure

In a sentence, I expect a land based J-XY to be cheaper to produce and operate than J-20, to not be constrained by engine/WS-15 bottlenecks, and to enable greater distribution of resources and work between SAC and CAC.

Gloire_bb said:

Let's get at least one operational and practical 5th gen engine first.

Furthermore - unlike many other countries, China has a relatively recent experience of producing single-engined fighter aircraft, there is no added difficulty here.

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See earlier part of this post regarding my opinions regarding 5th engine prospects re WS-15 and WS-19.


As I've repeatedly said in the last few posts -- if the engine is not a bottleneck and if the PLA are willing to wait for a slightly longer delay for a medium weight 5th gen, then sure, I agree that a clean sheet single engine medium weight 5th gen for PLAAF makes sense.


But I think that the engine most definitely will be a bottleneck if they're relying on WS-15s alone for everything (as opposed to WS-15s and WS-19s), and I also think the PLA want a medium weight 5th gen fighter faster rather than later and with reduced risk.
In context of this, I think the solution for a medium weight 5th gen fighter that makes the most sense in terms of platform capability, in terms of industry capability and bottlenecks, and in terms of time/risk.

Bltizo said:

In context of this, I think the solution for a medium weight 5th gen fighter that makes the most sense in terms of platform capability, in terms of industry capability and bottlenecks, and in terms of time/risk.

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Average weight aircraft:

1. An engine
2. Invisibility
3. Mobility
4. Cheap price

- >> They can develop such an aircraft from the J-10

FangYuan said:

Average weight aircraft:

1. An engine
2. Invisibility
3. Mobility
4. Cheap price

- >> They can develop such an aircraft from the J-10

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Developing the J-10 into a fifth-generation fighter with "invisibility" and a "cheap price"?

Are you trolling or are you serious? I can't tell... and I don't care.

You lower the IQ of the entire forum everytime you post. So please stop.

Just stop.

P.S. Could the mods look into wether FangYuan is a puppet account of Peter2018?

FangYuan said:

Average weight aircraft:

1. An engine
2. Invisibility
3. Mobility
4. Cheap price

- >> They can develop such an aircraft from the J-10

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Simply NO

FangYuan said:

- >> They can develop such an aircraft from the J-10

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1, You can't get 5th gen aircraft from 4th gen, you just can't. I personally dislike this generation bickering, but in case of stealth a/c - it is true. Several incompatible requirements set 5th gen clearly apart.

2, The requirement to make stealthy aircraft (1)supersonic while carrying all necessary avionics(2) and reasonable payload bays(3) make it very difficult if not impossible to get on a single WS-10/Al-31/F110 class engine. Basically, you need F119/izd.30/WS-15 to get an approximate J-10 analog at 5th gen.

3, at least in theory, it isn't completely impossible to make stealth fighter on a weaker engine(there were American studies on F414), but those were pretty radical a/c. Radical designs tend to be risky, expensive, and delay-prone, +you'll have to sacrifice something anyway.

The Su-57 isn't based on the Su-35 at all. The control surfaces and the fly by wire system are a lot more complicated. That's one of the reasons why they want to switch the surfaces from hydraulics to electrical systems. The system is frickin complex and expensive.
While I don't discount the possibility the PLA will buy the Su-57 once the 2nd stage version is available I doubt it will be purchased in large numbers. Plus like other people here have said don't think the export price will be the same as the price the Russian government pays. It won't.

With regards to the WS-19 all the information we have points to it being in an advanced stage of development.

Bltizo said:

1/3. Now you're suggesting China make a large scale purchase of Su-57s without having the infrastructure, personnel and maintenance capabilities in the country to operate a fleet of Su-57s? You're digging a deeper hole for yourself for why such a purchase doesn't make sense.
2. I never said that the Su-57 is problematic to produce, I'm saying that between now and into the foreseeable future, by the time Russia's Su-57 orders have been fulfilled and are able to fulfill any hypothetical PLA Su-57 orders, whatever the costs are of J-20 and/or J-XY/J-35 would have also further reduced, making it dubious as to whether Su-57 will even be cost competitive to J-20s and/or J-XY/J-35 (assuming it even was in the first place, even looking at procurement alone).
4. Without clear cut cost breakdowns of equivalent aircraft and everything that goes with them, the numbers mean little to nothing, especially if it is for an aircraft that is only at the beginning of a potentially long production run.. So I definitively reject your notion that we know what the true equivalent costs of the aforementioned aircraft are next to each other.
6. This is a deflection. Regardless of whether Su-57 is compatible with Russian systems or not -- and this is assuming the PLAAF is even interested in Russian systems to begin with -- the Su-57 most definitely is not compatible with PLA systems and other aircraft and platforms and would require significant additional investment and work and time to enable that. By the way, the R-37M most definitely is not the equivalent of PL-15; the equivalent of PL-15 is K-77M, whose range most definitely is not 290km. Considering PL-15 is now a decade old from when it first began test fires and going on half a decade old in service, the PLA are obviously working
7. Whoever said the Su-57 sucks? The Su-57 is probably a perfectly good aircraft, but introducing it into the PLA in relation to other opportunity cost platforms that they could potentially acquire, in context of fleet wide requirements for maintenance, support, and operations, and system of systems warfare, means procuring Su-57 doesn't make sense.
8. I'm not strawmanning anything -- you're the one who first said in post #220 "It'd get around "J-20" failure claims"". I'm asking you what "failure claims" you're referencing and why you think it is reasonable to speak about those claims as if they are widely held.
9. I'm not sure what rumours those are, please provide a credible source. The most reliable indicators I've found in regards to PLA 6th gen efforts suggest that they will enter service before 2035. I've not seen anything credible regarding 2025 for a 6th generation fighter to emerge.
10. What you're describing here is purchasing a limited number of Su-57s as a supplement for 5th generation fighters as the PLA spins up production rates of J-20 and J-XY/J-35. That is very different to suggesting that the PLA should buy Su-57s en masse as "low end" 5th gen complement to J-20. If the procurement rate of J-20s and J-XY/J-35 was deemed strategically unacceptable, it might be possible that a purchase of Su-35s to make up the shortfall might be necessary, but would hardly be desirable or ideal.


For yourself, and for the others reading, I'll put my points clearly.
The below points are all ones which you are either unable to refute with current information, and the below which are all the current null hypotheses which require significant burden of proof for you to change otherwise:

A - We have no evidence as to what the true equivalent procurement cost of Su-57 vs J-20 vs F-35 are. Therefore you do not have the evidence to suggest Su-57 is cheaper than J-20 to procure.
B - We have no evidence as to what the true operating cost of Su-57 vs J-20 vs F-35 is. Therefore you do not have any evidence to suggest Su-57 is cheaper to operate than J-20. If anything, common sense and other recent trends in force structure and O+M costs tells us that introducing a new aircraft requires substantial costs in relation to its O+M infrastructure.
C - We have no evidence to suggest that the PLA is interested in Russian subsystems (weapons or sensors) that Su-57 may be compatible with. If anything, current and prior evidence in recent history overwhelmingly tells us the PLA is interested in integrating its own subsystems into any imported aircraft if possible.
D - Current Russian production of Su-57s will be tied up until the late 2020s for Su-57s for their domestic use, and Chinese production of J-20s and likely soon J-XY/J-35s will only further steam ahead in this time, likely outstripping Su-57s in scale and affordability.
E - PLA procurement of 4+ gen fighters are likely to continue in the next few years at least, in the form of SAC Flankers and continued J-10Cs.


In context of the above, it is absolutely reasonable if not inevitable to say that yes, Su-57 is a capable fighter and offers a unique set of capabilities for a 5th generation fighter, but does not offer significantly more capable systems or characteristics given the above industry and system points, to reasonably argue that the PLA Su-57s should be procured as a "low end 5th generation fighter".





*Snip for response length*

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1/3: And you're suggesting that China build the support infrastructure for a new fighter type (the J-XY) from nothing? Face it, China has run Russian arms before. The Su-35s are there, the Su-30MKKs are still in service, and so on. Your argument doesn't pass muster considering that China runs many aircraft (and other systems) imported from Russia in the PLAAF and PLANAF. A better argument for Russian missile superiority might simply be the S-400 export, for that matter.
2: You're assuming the limitation on Russian production is the technical complexity. This is the exact same argument I hear when people claim that "China can't produce the J-20" when it's the exact same question of the Russians it is of the Chinese, where's the money? If the Chinese absolutely wanted to, they could mass produce the J-20 by increasing the number of factories producing J-20s and moving staff / hiring new staff for J-20 production. But it produces it at the rate it does because there's only so much budget available. Sukhoi CAN expand its production rate, which is currently planned for 76 within 10 years, or a pace of roughly 8 per year, provided there's export demand.
4: Let's address it with A.
6: Misremembered. Point is, though, the R-37 is going to be modified for employment in the Su-57. The PL-21, in contrast, simply can't fit in the J-20.
7: As mentioned before, if the cost is sufficiently low, the Su-57 is a reasonable purchase opportunity. But we go back to A.
8: According to Western observers, the J-20 is a failure. We've all seen the claims ever since the J-20 came out. I'm not supporting them, nor am I claiming that a Su-57 purchase substantiates this claim.
9: I am looking for these rumors, I believe I noted them either on this forum or elsewhere.
10: We have to define what limited is, as well as how well the Su-57 platform compares to the J-XY. From reports, the J-XY isn't all it's cracked up to be (if it's 5 times the cost of a J-15, as indicated elsewhere, it's too expensive for what's hoped for if it's for the PLAAF). For limited, I see 300 units as a reasonable PLAAF purchase, but you'd see this as bulk. This is because the Russians are unlikely to want to provide the PLAAF more Su-57s than what they'd want themselves.

A. You're setting an arbitrarily high criteria for "true" information on what the relative costs are. We already have auxiliary information on what AVIC costs look like. The J-10A, for instance, was aiming to be exported at a higher cost than a comparable F-16. The Russians have put out a deal (and you're denying the evidence here). And your underlying argument is that "we don't know", when my these is: "if the Russians sell the Su-57s at sufficient quantity and sufficiently low prices, the PLAAF should buy the Su-57 simply based on price alone".
B. Here, you do have a point, and Russian equipment is notorious for high operating costs. But at the same time, rumors about the J-20's operating costs aren't favorable either.
C. Okay, and? We're back at looking at the Chinese missile lacuna. Remember, we've both been watching the PLAAF for a very long time, including rumors of PL-12D etc with ramjets. Where the hell are they? Meanwhile, there's Russian missiles that have capabilities that the PLAAF lacks (Kinzhal, for instance, is approximated by CJ-100s air-launched by H-6Ns, but a variant is launchable from the Su-57). Moreover, Russian systems also provide redundancy should Chinese systems fall behind schedule. Consider the tortured history of the WS-10 engine. In the J-10, the AL-31s made sure the airframe was workable until WS-10s were ready.
D. As mentioned above, this is based on Russian budgets. The Armata, for instance, was originally intended to replace the T-72 / T-90 fleet, until the Russians realized they were broke, axing production rates to 100 units.
E. Let's wait and see what happens. There's a single report that J-10C procurement has been at least temporarily halted.

===

As to your other long-response, simple answer. The primary factor that determines whether the PLAAF is likely to purchase the Su-57 is the price. If the Su-57 has a significant cost advantage over the J-XY and J-20 types, it's worth buying because as a long-ranged heavyweight stealth/semi-stealth fighter, it fits China's needs sufficiently. It does not mean that the PLAAF will have to abandon its development of its own indigenous fighters, it just means that the PLAAF saw a bargain and leaped at it, while still retaining its normal purchase and development rate of its own fighters.