Future PLA combat aircraft composition

Bltizo said:

And yes, what you described -- a "worse" J-20, with commonality with the navy, and a larger production run, more maintainable stealth, more advanced production method -- sounds like a hell of an aircraft to me, especially as such an aircraft would not need the additional development time needed for a clean sheet design.

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There is no ~10 year technology gap like in-between F-22 and 35, however: FC-31(if it is the base aircraft for J-XY) and J-20 come from the very same technological level.

So, if there is space for "larger production run, more maintainable stealth, more advanced production method", the same is true and applicable to a larger J-20 run(minus unwarranted commonality problems and huge development cost). If there is no such difference - well, then no difference indeed.

As of now, I can't see any advantages for FC-31 / J-20 mixture over a WS-10/15-centric fleet, unless something is seriously wrong with J-20 itself, Tejas-level wrong. There is no indication of this being the case.

If idea is to complement J-20 numbers with a more numerous stealth type - you may very well wait for WS-15 and make a single-engined counterpart to the J-20. Same dev costs, same or better commonality level(within 1 fleet, not two), more savings.

Bltizo said:

And of course all of this talk of a single engine medium weight 5th gen aircraft operates on the understanding that it would need an uprated WS-15 variant to power it.

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If you design a new aircraft from scratch, and don't want more stealth strike - basic WS-15 will be fine.
P. S. and as of now, from our current information, separate J-XY engine isn't ahead of WS-15 in readiness. Quite probably it's the other way around.

Well the thing is a twin engine aircraft will have a lot more parts. This means it will be a lot more expensive than a single engine aircraft. In the case of carrier based aviation the twin engine makes sense because it increases aircraft reliability with engine out. Given that the naval aircraft will be operating far from land bases and repair facilities it is critical to reduce the chance of crashes.

I think it would be relatively simple to design a stealth aircraft based on the WS-10 engine with future upgrade to WS-15 engine similar to what is being done with the J-20. Nearly all the other components like radar, weapons systems, already exist. With regards to engine production output of the WS-15, having to produce two smaller engines does not seem to make things easier to me. The man hours required per engine will likely be similar but you will need to produce two engines and the production of the smaller engines in enough numbers currently is non existent. Only once the J-XY goes into production will the smaller engine go into mass production too, assuming China doesn't have problems and resorts to import of Russian made engines based on the RD-93 like they did with the JF-17/FC-1.

China does not need to make their lightweight land based fighter be a large aircraft optimized for ground attacks like the US did with the F-35.

Bltizo said:

Just because an aircraft is "twin engined" doesn't mean it is necessarily larger than a single engined aircraft.
The J-XY/J-35 may even end up being a little bit lighter than their respective F-35 variants in terms of weight.

In which case the costs basically come down to the engine procurement and engine operating costs as the main difference.

In which case IMO that depends on the engine and the availability of the industry.

An aircraft equipped with two WS-13E and going forwards WS-19 will ultimately still reduce demands for WS-15, and for a proper single engine 5th generation aircraft you will likely need the WS-15 to be further uprated, in turn consuming more turbofan industry resources.


All things considered, given how tight the timeline is for needing a medium weight 5th gen fighter, and considering the likely proliferation and rising profile of UCAVs and loyal wingman aircraft (which are able to be effective using older generation WS-10 and WS-13 variants, reducing demand on WS-15 and WS-19), and in turn considering that WS-15s and variants will likely be prioritized for J-20 production and 6th gen production... Imo whatever limited benefits there are for operating a single engine medium weight 5th gen aircraft over a twin engine medium weight 5th gen aircraft just aren't enough to outweigh the service fleet and industry demands and limitations.


Going into the mid early to mid 2030s onwards (which is when I expect the earliest J-10s will need true retirement), I expect a combination of twin engine J-XY land based variants, and loyal wingman UCAVs to be an appropriate and feasible replacement for them.

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The F110 weighs about 1,800 kg. The F414, on the other hand, weighs about 1,111 kg, or two of them would be about 25% heavier. And that's not including the fairings and other accommodation for twin engines, including fuel routers. When this is considered, the F-35 is a 15.4x10.7 fighter. The FC-31 we've seen is estimated at 17.3x11.5, or about 12% larger in one dimension and 7% larger in the other. So a FC-31 will be heavier, larger, but enjoying a greater engine power than a F-35.

Gotta remember, the fighter weight ranking goes like this:

1 medium weight engine (LCA Tejas, Saab Gripen)
1 heavy weight engine (F-16, J-10)
2 medium weight engines (F-18A / F-18E, Rafale, MiG-29, Eurofighter)
2 heavy weight engines (F-15, Su-27, F-22, Su-57, J-20)

That said, the J-XY could be lighter based on 3D-printed Titanium.

Come on guys ... stick to the topic and if you want to discuss general engine configurations, the idea to develop a single engine stealth fighter or comparisons to US types, do this in another thread!

This is for the J-35

gelgoog said:

Well the thing is a twin engine aircraft will have a lot more parts. This means it will be a lot more expensive than a single engine aircraft. In the case of carrier based aviation the twin engine makes sense because it increases aircraft reliability with engine out. Given that the naval aircraft will be operating far from land bases and repair facilities it is critical to reduce the chance of crashes.

I think it would be relatively simple to design a stealth aircraft based on the WS-10 engine with future upgrade to WS-15 engine similar to what is being done with the J-20. Nearly all the other components like radar, weapons systems, already exist. With regards to engine production output of the WS-15, having to produce two smaller engines does not seem to make things easier to me. The man hours required per engine will likely be similar but you will need to produce two engines and the production of the smaller engines in enough numbers currently is non existent. Only once the J-XY goes into production will the smaller engine go into mass production too, assuming China doesn't have problems and resorts to import of Russian made engines based on the RD-93 like they did with the JF-17/FC-1.

China does not need to make their lightweight land based fighter be a large aircraft optimized for ground attacks like the US did with the F-35.

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Gloire_bb said:

There is no ~10 year technology gap like in-between F-22 and 35, however: FC-31(if it is the base aircraft for J-XY) and J-20 come from the very same technological level.

So, if there is space for "larger production run, more maintainable stealth, more advanced production method", the same is true and applicable to a larger J-20 run(minus unwarranted commonality problems and huge development cost). If there is no such difference - well, then no difference indeed.

As of now, I can't see any advantages for FC-31 / J-20 mixture over a WS-10/15-centric fleet, unless something is seriously wrong with J-20 itself, Tejas-level wrong. There is no indication of this being the case.

If idea is to complement J-20 numbers with a more numerous stealth type - you may very well wait for WS-15 and make a single-engined counterpart to the J-20. Same dev costs, same or better commonality level(within 1 fleet, not two), more savings.

If you design a new aircraft from scratch, and don't want more stealth strike - basic WS-15 will be fine.
P. S. and as of now, from our current information, separate J-XY engine isn't ahead of WS-15 in readiness. Quite probably it's the other way around.

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If the PLAN is getting the J-XY anyways regardless of what the PLAAF wants, and the J-XY is designed to be cheaper and easier to manufacture than the J-20, and there’s no compromise in capability for the PLAAF’s needs, why do the developmental work of three designs when you only need two? The supply chain for the J-XY will be there with or without a new single engined fighter. It seems a lot less efficient from a budget and cost standpoint to created the production line for another new design rather than just recuperate more of the investments in R&D and production you made for the second design.

Edit: Sorry Deino, last I’ll say on this topic, feel free to move the comment.

It seems a lot less efficient from a budget and cost standpoint to created the production line for another new design rather than just recuperate more of the investments in R&D and production you made for the second design.

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If that was true then why not just use the J-20 everywhere? This is the same kind of thinking which led to the abortion that is the JSF.
I think there are more reasons than just cost to manufacture the J-XY. In fact expense was the minor concern with it. The major reason was to design a stealth fighter which was well suited to the carriers. Otherwise they might as well just have made a navalized J-20.
Sure it might be cheaper to manufacture the J-XY airframe because it uses more modern and automated techniques. But that isn't the main point in it. Plus if they ever make a land based version of the J-XY they will have to make changes to the design. It won't need foldable wings and it won't need as robust a landing gear for example. Those features add weight and make maintenance harder.

Experience Russia had with the MiG-29 and Su-27 series shows that the MiG-29 wasn't cheap enough to justify its existence. The cost reduction is slim and is outweighed by the reduction in capabilities. It might cost 20% less and you get 30% less payload or something like that. In contrast the F-16 was a highly successful design from a cost standpoint vs the F-15.

gelgoog said:

If that was true then why not just use the J-20 everywhere? This is the same kind of thinking which led to the abortion that is the JSF.
I think there are more reasons than just cost to manufacture the J-XY. In fact expense was the minor concern with it. The major reason was to design a stealth fighter which was well suited to the carriers. Otherwise they might as well just have made a navalized J-20.
Sure it might be cheaper to manufacture the J-XY airframe because it uses more modern and automated techniques. But that isn't the main point in it. Plus if they ever make a land based version of the J-XY they will have to make changes to the design. It won't need foldable wings and it won't need as robust a landing gear for example. Those features add weight and make maintenance harder.

Experience Russia had with the MiG-29 and Su-27 series shows that the MiG-29 wasn't cheap enough to justify its existence. The cost reduction is slim and is outweighed by the reduction in capabilities. It might cost 20% less and you get 30% less payload or something like that. In contrast the F-16 was a highly successful design from a cost standpoint vs the F-15.

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If the PLAN decided to go with a J-20 derivative maybe it would make more sense for the PLAAF to go with more J-20s or a single engine stealth fighter? Just because a J-XY design would be better suited for carriers doesn’t mean it would not also be suited for a “lo” mainstay fighter for the Air Force. They don’t need to do much that work to convert a J-XY into a land based fighter given that it’s already derived from a land base fighter. Doing the conversion in that direction involves simplification rather than complication. It’s a whole lot less work than designing, developing, and testing a completely new fighter. Just the difference in turnaround time alone probably makes it more worthwhile.

Just because the J-XY is a dual engine midsized fighter like the Mig-29 does not mean that their cost to capability ratios would be comparable. The extra engine is not the only variable involved in maintaining the unit economics of a fighter fleet, and stealth plus differences in doctrine can completely change the value calculus of capabilities. If the PLA is smart and not scattershot about such a procurement it will be baked into their requirements. So far in my decade plus of PLA watching I’ve seen no reason to doubt the PLA’s competence in those regards.

Gloire_bb said:

There is no ~10 year technology gap like in-between F-22 and 35, however: FC-31(if it is the base aircraft for J-XY) and J-20 come from the very same technological level. -snipped for post length-

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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.
Fortunately J-20 will be continuing production for quite a long time into the 2030s so it will be able to benefit to a degree from various advancements that J-XY/J-35 will enjoy wrt more maintainable stealth and more advanced production methods, but those will likely end up being a new variant of J-20 altogether that will make up only a fraction of the total production run of all J-20s ever produced.
So no, I wouldn't say that "larger production run, more maintainable stealth, more advanced production method" applies to J-20 in the same way.

Regarding WS-19, I'm not saying it is currently ahead of WS-15 in terms of readiness.
But what I am saying is that by the time we reach the mid to late 2020s, WS-19 will likely be very close to WS-15 in terms of readiness and more importantly expansion in production of both WS-19 and WS-15 can occur independent of each other and going into the 2030s the production of WS-15s alone I doubt will be able to satisfy requirements for J-20s, 6th gens, and a clean sheet single engine 5th gen.

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If the goal is to expand 5th generation fleet size and preferably have the expansion in fleet size be more economical, there are essentially three options that I see going forwards;
A) Increase J-20 production and integrate new technologies and production methods into J-20 going forwards. Forgo a land based medium weight 5th generation fighter.
B) Introduce a land based J-XY/J-35 variant, twin engine medium weight 5th gen.
C) Introduce a clean sheet land based single engine medium weight 5th gen.


But as I wrote in my previous post, there are some other considerations to make as well, regarding both timeline and engine availability:

1. Such an aircraft should enter service before the end of the decade, preferably sooner rather than later. Speed and risk from project initiation to service is important, not only in general, but also for the PLA given the proliferation of 5th gens and additional high capability aircraft in the region. If a project can be 2-3 years faster than a competitor with lower risk (say, if the competitor is a clean sheet design), then that is a very desirable trait.
and,
2. Engine availability, where the medium weight land based 5th gen fighter's production in the above timeline and its powerplant should not be limited by the prioritization of WS-15 production for J-20s and 6th gen aircraft in the same period. Either there is enough WS-15 production to satisfy production of J-20, initial 6th gen aircraft AND said medium weight land based 5th gen aircraft --- OR, this aircraft should adopt an alternative powerplant configuration which is not limited by WS-15 production/availability.


IMO, based on the above two factors, which imo are likely prerequisites and limiting factors for PLA planning and procurement, I think that option B) introducing a land based J-XY/J-35 variant is able to meet those two criteria the most.

Option C), pursuing a clean sheet single engine design might be viable, as I wrote before in my last post, IF:
1. Said clean sheet design at least equally low risk and equally short time compared to a land based J-XY/J-35 derivative (to enter service in the late 2020s time period).... (Or alternatively, if the PLA pushes back the timeline for when they want a medium weight 5th gen to enter service)
AND,
2. If AECC was able to ramp up the production rate of WS-15 sufficiently to meet the production demand and timeline for J-20s, initial production 6th generation aircraft, and said single engine medium weight 5th gen aircraft in the late 2020s to early/mid 2030s time period.

Option A), increasing the production rate of J-20s is also certainly possible, and is able to fulfill criteria 1. as being a relatively low risk and time sensitive solution.... however the issue is criteria 2., whether production of WS-15 is able to be scaled appropriately upwards for massive expansion in production of J-20. There is ultimately also the fact that J-20 remains a heavy weight fighter, and compared to the medium weight designs of Option B) and Option C) that will incur additional costs independent of how many engines each aircraft has.



I'd also add that all of this discussion about a medium weight 5th gen fighter IMO is a little bit too laser focused on the cost benefits of single engine vs twin engine -- yes, operating an aircraft with a single high thrust engine can confer meaningful cost savings versus a design with twin medium thrust engines by virtue of having one less engine to maintain and operate.

However procurement of an aircraft is influenced by other factors beyond costs of operation/maintenance relating to engines alone.
Other important factors for both the industry and military side include the below, which I will weigh up for the respective single vs twin engine options:
- Other non-engine related operation/maintenance costs intrinsic to the aircraft's design and/or production methods
------ both a single engine and J-XY derivative/twin engine medium weight 5th gen option can include these in their programs and I do not see either having a leg up over the other, draw
- Commonality, shared costs and shared upgrade paths with other aircraft variants over their lifetimes
------ both a single engine and twin engine design will obviously seek to share as much subsystems with other 5th gens as possible (J-20 and carrier based J-XY), however the twin engine J-XY land based derivative will be much more of a direct variant/sibling to the carrier based J-XY than the clean sheet single engine option. Much greater structural similarities, much greater ease in upgrade paths and shared components, twin engine advantage
- Speed/time sensitivity and risk from starting the program to having an aircraft in service
------ a single engine clean sheet design will almost certainly take longer time and more risk and aerospace resources than a J-XY derivative, twin engine advantage
- Bottlenecks/availability of any key subsystems (e.g.: specific engine types)
------ a single engine clean sheet design will inevitably require WS-15s, while a twin engine J-XY design will be using WS-19s. We know that demand for WS-15s will be high for J-20 production and initial 6th gen production, and 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. WS-19 on the other hand will only be required for powering J-XY aircraft (carrier and land based). Twin engine advantage, for now
- Distributing and maintaining experience and work across different companies in the industry in a reasonable manner and effective distribution of aerospace resources
------ a clean sheet single engine design and production could conceivably be done at SAC rather than CAC, but we already know that the carrier based J-XY is being developed at SAC to begin with. But then in turn you'll be having them develop a clean sheet design already when both SAC and CAC are already busy with J-XY and J-20 variants + 6th gen efforts, respectively. Is it wise to burden SAC or CAC with another new clean sheet design? Twin engine advantage


So, on balance, comparing the strengths of a clean sheet single engine design vs a J-XY derived twin engine design and common benefits

Single engine strengths:
- Operating cost and maintainability benefits of a single engine

Twin engine strengths:
- Operating costs and upgrade costs/paths and certain shared logistics benefits of having a close carrier based variant
- Greater speed from project initiation to service and reduced risk
- Will not have same degree of engine bottleneck (WS-15 production/availability) as a single engine aircraft
- More sensible distribution of aerospace resources in context of SAC and CAC's other respective ongoing projects

Common strengths of both:
- Non engine related operating costs intrinsic to both aircraft's design and production




So, I happily agree that having a single engine versus two engines does confer engine specific operating costs and maintainability benefits.

However, given the overall force structure, naval procurement commonality potential, time sensitivity and risk requirements, and industry setup and limitations for the PLA's case specifically, I do not think the cost and maintainability benefits of a clean sheet single engine design vs a twin engine J-XY derivative are enough to outweigh the cumulative other strengths of the latter.
For the PLA, at this stage, I think if they want to expand their 5th gen fighter fleet by virtue of a medium weight 5th gen fighter, a twin engine J-XY derivative makes the most sense.

Deino said:

Come on guys ... stick to the topic and if you want to discuss general engine configurations, the idea to develop a single engine stealth fighter or comparisons to US types, do this in another thread!

This is for the J-35

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Any idea why the fc-31 doesn't use fully rotatable vertical stabilizers like on the J20 and Su57? My impression is that fully rotatable design is more advanced because you don't need to make them as big. Since vertical stabilizers are one of the biggest contributors to RCS, smaller is better.

Thoughts?

Also is there a technical name for the fully rotatable design?

Weren't there claims that China could be testing a 6th gen by 2025? Interestingly enough, as I've pointed out, you have a 6-gen alike in the J-20 with tailfins and ventrals removed. Need a laser? Just stuff a laser attack pod into the side bays of the J-20, with the full "retractable weapons launch" system attached. For yaw-control, the frontal canards can suffice, just not in high-AoA without the tailfins.

You could probably designate it as a "strike" J-20, give it a new designation (J-26 or whatever), and declare it a Chinese "5th gen" design or Western equivalent to 6th. The West would probably pooh-pooh it as a 5.5th gen fighter, but it's close enough and bridges the gap and the need for a NGAD counter until a "true" (i.e, 6th generation Western, 6th generation Chinese) fighter is ready (and it'd roughly be a 6.5th gen fighter by Western standards given that NGAD came first and provided a yardstick to counter).

As I've said before, that's the true genius of the J-20 design. Its layout is easily modifiable to a 6th-type design (a la Boeing canarded-6th gen) and with pods gets laser attack capability.

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A modified J-20 would also be a good time to start buying Su-57s in bulk, given the cheapness of Russian military gear. It'd get around "J-20" failure claims by claiming that China is doing 6th gens now, and Russian 5th gens are being built to fill the low-capability gap while China devotes its production to Chinese "5/6th" gens.