Shenyang FC-31 / J-31 Fighter Demonstrator

latenlazy

Brigadier
So low end fighters will probably be replaced by UCAV, it's the end of medium and small fighters more or less. Export still exist for a while.

FC-31 is probably near the cost of a J-20 with his twin engines... don't know if the decision do go for it or not would be to maintain level of different aerospace corporations. Cooperation look way higher in China between corporations so i'm not sure it could be the case. UCAV with AI will probably do the most of the work in a couple of decades.
FC-31 is designed to be fast and cheap from a production standpoint.
 

stannislas

Junior Member
Registered Member
FC-31 is designed to be fast and cheap from a production standpoint.
??? i thought FC-31 was designed as a comeback of SAC after lost the J-20 program to CAC ...
if in any case, J-20 was mentioned in many times by pilots and designers and ground crews as regard as moduler, and easy to produce and maintaine...
not saying FC-31 isn't, but in any case, there is no prove it has some kind of production or cost advantages ...
 

latenlazy

Brigadier
??? i thought FC-31 was designed as a comeback of SAC after lost the J-20 program to CAC ...
if in any case, J-20 was mentioned in many times by pilots and designers and ground crews as regard as moduler, and easy to produce and maintaine...
not saying FC-31 isn't, but in any case, there is no prove it has some kind of production or cost advantages ...

Supposedly FC-31 builds in that direction even more. But either way the point is engine count isn’t the only cost factor.
 

Blitzo

Lieutenant General
Staff member
Super Moderator
Registered Member
of course, but given how much engine maintaince is costing, it would be much more persuasive saying FC-31 is a low cost replacement of J-20 if it's a single engine aircraft.

Every year this same discussion is repeated along the same lines.

And everytime I will say that there are ways in which a PLA FC-31 (or rather, land based J-XY variant) can still be meaningfully lower cost to procure and operate than J-20, even if it isn't a single engine aircraft.

There is no single engine 5th gen fighter in development or even rumoured, so any such discussion as an "alternative" is entirely moot to the discussion.
 

stannislas

Junior Member
Registered Member
There is no single engine 5th gen fighter in development or even rumoured, so any such discussion as an "alternative" is entirely moot to the discussion.
no one says there will be a single engine "alternative", where you get from this?
And everytime I will say that there are ways in which a PLA FC-31 (or rather, land based J-XY variant) can still be meaningfully lower cost to procure and operate than J-20, even if it isn't a single engine aircraft.
how? beside of raw matiral and medium size engine may cost slightly less than large size engine in maintaines, where is the meaningful cost saving places?
the electronics equipments are taking higher and higher percetage of the total cost these days, if FC-31 doesn't equip any second class craps, the cost of J-20 and FC-31 would be close
 

Blitzo

Lieutenant General
Staff member
Super Moderator
Registered Member
no one says there will be a single engine "alternative", where you get from this?

My point is that there will be no single engine 5th gen fighter, so such a class of fighter shouldn't even be part of the discussion when considering a lower cost PLA 5th gen fighter in relation to J-20.

Thus, whether a "single engine" PLA FC-31 is "more persuasive" shouldn't even be part of the conversation.
Instead, it should be whether a PLA FC-31/LB J-35 can be persuasive enough relative to J-20 to be a lower cost option.


how? beside of raw matiral and medium size engine may cost slight less than large size engine in maintaines, where is the meaningful cost saving places?
the electronics equipments are taking higher and higher percetage of the total cost these days, if FC-31 doesn't equip any second class craps, the cost of J-20 and FC-31 would be close

Because a PLA FC-31/land based J-35 will be manufactured and designed using technologies that are nearly a decade ahead (and that's nearly a decade of time in China's MIC context) of what J-20 had, all of which is built in with them from the outset, that can facilitate better maintainability (and lower operational costs) even easier than what J-20 should have.

Additionally, other factors that are less significant but still present, include the PLA FC-31/LB J-35 being a physically smaller aircraft overall to J-20, being able to share development costs of certain subsystems between navalized J-35 (and J-20 to an extent).
 

stannislas

Junior Member
Registered Member
My point is that there will be no single engine 5th gen fighter, so such a class of fighter shouldn't even be part of the discussion when considering a lower cost PLA 5th gen fighter in relation to J-20.

Thus, whether a "single engine" PLA FC-31 is "more persuasive" shouldn't even be part of the conversation.
Instead, it should be whether a PLA FC-31/LB J-35 can be persuasive enough relative to J-20 to be a lower cost option.
Again, no one said there will be a single engine FC-31, that was just a figure of speach on how much an engine would cost in terms of whole aircraft, i don't know why you keep insist on impression of a single engine FC-31

Because a PLA FC-31/land based J-35 will be manufactured and designed using technologies that are nearly a decade ahead (and that's nearly a decade of time in China's MIC context) of what J-20 had, all of which is built in with them from the outset, that can facilitate better maintainability (and lower operational costs) even easier than what J-20 should have.
First of all, J-20 is debut in 2011 and FC-31 is in 2012, so there is no a decade ahead, if anything FC-31 did have some luxery to test some new technologies, but given how J-20 is continuously improving, i will say a lot of the new techs that was tested on FC-31 have already been adapted on J-20, like the 3D printing, there were many reports suggested that J-20 has a lot of 3D printed metal parts, although not that big structure components on FC-31 V2.0 though

Second of all, i think the general level of J-20 maintaince and FC-31 are in the same level, as I mentioned before, there are many interviews with pilots, designer and ground crews said that J-20 is a moduler designed aircraft and very easy to maintain. and being an moduler aircraft, if there is any part that is broken or outdated or need to be imporved, just replace that with the new one. I expact the FC-31 to be at the same level of maintance as to J-20.

Additionally, other factors that are less significant but still present, include the PLA FC-31/LB J-35 being a physically smaller aircraft overall to J-20, being able to share development costs of certain subsystems between navalized J-35 (and J-20 to an extent).
In terms of the physical size and share development, bare in mind what I mentioned before, that the general cost of electronics compnents of modern day fighter is getting higher and higher. I remember I read somewhere, that in early version of F-16, the engine was taking 40% of total building cost, all electronics combines contributed only 15-20%. When it came to later F-16 like block 50 or something else, the engine is still taken rouhgly the same percentage, just slightly lower, but the overall electronics increase to nearly nearly as much as the rest of the cost which is 30%. Now when it come to F-35%, the F-135 only takes 30% of the total cost, the electronics take more than 40% of the cost, and rest is less than 30%.

This trend would not be different on J-20 and FC-31, that electronics take the highest percetage of the total construction cost, so the size of the aircraft would matter less even if less materials was used on a medium size aircraft.

In terms of share development, let me put his way, as long as we are still expecting the land based FC-31 would be somewhat different to the carrier based J-35, then there will be parts that are not able to be shared between each other, like the wing folding mechanics, and this will generate extra cost. J-20 on the other hand doesn't have this issue at all, so the total development budget of course will be lower on J-20 program in compare with FC-31 +J-35.

Last but not least. regardless on how much your estimation of the number of total landbase FC-31 and carrier based J-35 are, based on current production rate of J-20 we valued recently, the total production number could easily reach 1000 in all projections around 2030, by then how many FC-31 + J-35 can PLA would have in total? I bet the number will be much less anyway. in that case, the cost per unit of J-20 would in advantage, and we haven't calculate the inflation when FC-31 hypothetically start to mass production in late 2020 or early 2030 yet.
 

Blitzo

Lieutenant General
Staff member
Super Moderator
Registered Member
Again, no one said there will be a single engine FC-31, that was just a figure of speach on how much an engine would cost in terms of whole aircraft, i don't know why you keep insist on impression of a single engine FC-31


First of all, J-20 is debut in 2011 and FC-31 is in 2012, so there is no a decade ahead, if anything FC-31 did have some luxery to test some new technologies, but given how J-20 is continuously improving, i will say a lot of the new techs that was tested on FC-31 have already been adapted on J-20, like the 3D printing, there were many reports suggested that J-20 has a lot of 3D printed metal parts, although not that big structure components on FC-31 V2.0 though

Okay, first of all we need to get our nomenclature right.
FC-31 is the FC-31v1 and FC-31v2 which first flew in 2012 and 2016 respectively. These were both iterative airframe technology demonstrators, similar to the J-20 200X TD airframes, which in turn are all similar to the YF-22/23 and X-35/32 airframes.
For FC-31v1 and FC-31v2, we have never had any indication that they've intended to develop those airframes as operational fighters in their existing state nor had they pursued the sort of developmental prototyping that we would expect.

Over the last few years, the discussion around a "FC-31 for PLA" has been oriented around an actual proper developmental program of a FC-31 derived airframe. A program that actually takes some of the tech demo work done on the FC-31v1 and FC-31v2 but applies it to a proper program of record with associated establishment of prototyping, testing and production facilities being raised.

J-XY/35 is the first major PLA FC-31 variant, for carrierborne duties.
We've also had rumours for the last few years that a land based variant is expected in the imminent future -- and it has variously been referred to as a "PLA FC-31" or as "land based J-XY/35". Either way, such an aircraft would not be merely a tech demonstrator like FC-31v1/v2, but rather a proper program of record itself, and based on the carrierborne J-XY/35, it is likely to share significant commonality with it (which is why "land based J-XY/35" has been one of its more used names).

So, circling back to the point you raised the original FC-31v1/v2 technology demonstrator airframes are not relevant to the discussion, it is their production representative airframes that we are interested in.

J-20 201X prototype first flew in early 2014.
J-35/XY prototype first flew in late 2021.
The land based J-35/XY/PLA FC-31 is likely to share many similar technologies to the carrierborrne J-35/XY, so we can use the J-35/XY as the benchmark if you want.
That's a 7 year difference.


Second of all, i think the general level of J-20 maintaince and FC-31 are in the same level, as I mentioned before, there are many interviews with pilots, designer and ground crews said that J-20 is a moduler designed aircraft and very easy to maintain. and being an moduler aircraft, if there is any part that is broken or outdated or need to be imporved, just replace that with the new one. I expact the FC-31 to be at the same level of maintance as to J-20.

It is all relative.
J-20 may be relatively easy to maintain and relatively modular.

But I expect the land based J-35/XY to be even more so, leveraging nearly a decade of additional technology advancement and newer production techniques.




In terms of the physical size and share development, bare in mind what I mentioned before, that the general cost of electronics compnents of modern day fighter is getting higher and higher. I remember I read somewhere, that in early version of F-16, the engine was taking 40% of total building cost, all electronics combines contributed only 15-20%. When it came to later F-16 like block 50 or something else, the engine is still taken rouhgly the same percentage, just slightly lower, but the overall electronics increase to nearly nearly as much as the rest of the cost which is 30%. Now when it come to F-35%, the F-135 only takes 30% of the total cost, the electronics take more than 40% of the cost, and rest is less than 30%.

This trend would not be different on J-20 and FC-31, that electronics take the highest percetage of the total construction cost, so the size of the aircraft would matter less even if less materials was used on a medium size aircraft.

In terms of share development, let me put his way, as long as we are still expecting the land based FC-31 would be somewhat different to the carrier based J-35, then there will be parts that are not able to be shared between each other, like the wing folding mechanics, and this will generate extra cost. J-20 on the other hand doesn't have this issue at all, so the total development budget of course will be lower on J-20 program in compare with FC-31 +J-35.

Last but not least. regardless on how much your estimation of the number of total landbase FC-31 and carrier based J-35 are, based on current production rate of J-20 we valued recently, the total production number could easily reach 1000 in all projections around 2030, by then how many FC-31 + J-35 can PLA would have in total? I bet the number will be much less anyway. in that case, the cost per unit of J-20 would in advantage, and we haven't calculate the inflation when FC-31 hypothetically start to mass production in late 2020 or early 2030 yet.

As you said, the cost of electronics makes up a major part of an aircraft these days.
I expect the carrierborne J-XY/35 and land based J-XY/35 to be virtually identical in those respects, and many other components as well.

More importantly, J-XY/35 will be a newer aircraft designed and produced to be even more easy to maintain than J-20. And it will also be a physically smaller aircraft as well, both of which will also lend a degree of lower procurement and operational costs than J-20 on top of what I wrote in the prior sentence.


As for production rate of J-20 and J-XY/35, I wrote my thoughts a few weeks ago in the J-20 thread, pertinent part as follows:
"
However, I am not sure if 1000 J-20s would be a sufficient number of 5th generation fighters while 6th gen kicks into gear.

By 2030, many of the older Flankers and even J-11Bs would likely need replacement.
Not to mention all of the PLA's 3rd gen fighters and JH-7As, and likely many of the J-10 variants before J-10C may be due for retirement or even not worth sustaining at that point.

All of which is to say, there may well be another good 800-1000 land based fighter aircraft that need replacement from 2025 to mid/late 2030s, on top of the demand for 1000 J-20s.

A land based J-XY/35 (I call it that instead of "J-31" or "FC-31" for now), could begin production around 2025-2027 alongside the standard carrier based J-XY/35, and continue production through to the mid or even late 2030s.

Or putting it a different way, in terms of active in production land based manned fighter aircraft types, between now and the mid/late 2030s:

2022-2025: J-20, J-16, J-10C
2025-2030: J-20, J-XY land based, cessation of J-16 and J-10C shortly after 2025(?)
2030-2035: cessation of J-20 shortly after 2030(?), J-XY land based, 6th gen
2035-2040: 6th gen, cessation of J-XY after mid to late 2030s (?)"

 

stannislas

Junior Member
Registered Member
We've also had rumours for the last few years that a land based variant is expected in the imminent future -- and it has variously been referred to as a "PLA FC-31" or as "land based J-XY/35". Either way, such an aircraft would not be merely a tech demonstrator like FC-31v1/v2, but rather a proper program of record itself, and based on the carrierborne J-XY/35, it is likely to share significant commonality with it (which is why "land based J-XY/35" has been one of its more used names).
No, and stop making what your believe or even imaging as it's a fact.

In fact there is no evidence of that the landbased J-XY/35 is concret, SAC state multipl times that FC-31 program is 'one aircraft four varients' and most recently in Zhuhai airshow it becomes 'one aircraft three varients', and people just making up rumors of PLAAF will adapt landbased FC-31 based on this. This is what SAC designer want, but whether if it is PLAAF want, is still an unknown.

But regradless of what, it's a program fundamental on the FC-31 program, and like I stated few days ago with you, it will be greatly cost ineffective to reverse the design from J-35 back to a land based aircraft than develop from FC-31 V2.0 with some J-35 technologies.

t is all relative.
J-20 may be relatively easy to maintain and relatively modular.

But I expect the land based J-35/XY to be even more so, leveraging nearly a decade of additional technology advancement and newer production techniques.
As you said, the cost of electronics makes up a major part of an aircraft these days.
I expect the carrierborne J-XY/35 and land based J-XY/35 to be virtually identical in those respects, and many other components as well.
You do understand the word and concept of 'modular', do you? it means that if future design is money saving or more effective, you can swap your old equipment with this fancy and cheaper one

People has using this on programming for decades, and just one of the most popluar language 'python' as an example, almost all the package are replacable, as long as they are in the same major python version, 2.0 or 3.0, so for example the most Python 3.10 improve the iteration function effectioncy by a lot, that means if I update to 3.10 all my codes in Python 3.0+ can enjoy this update.

Same goes with J-20 and FC-31 in this case, the idea of being the modular is to setup a framework for future updates, it's intend to co-op with 'additional technology advancement and newer production techniques.', so when better and cheaper equipment is coming, J-20 and J-35 could use it straight way.

More importantly, J-XY/35 will be a newer aircraft designed and produced to be even more easy to maintain than J-20. And it will also be a physically smaller aircraft as well, both of which will also lend a degree of lower procurement and operational costs than J-20 on top of what I wrote in the prior sentence.
I will repeat again, physically size is never a cost sensitive issue in modern days aircraft. In fact, even between F-15 and F-16, the biggest cost difference in terms of difference is engine.

As for production rate of J-20 and J-XY/35, I wrote my thoughts a few weeks ago in the J-20 thread, pertinent part as follows:
"
However, I am not sure if 1000 J-20s would be a sufficient number of 5th generation fighters while 6th gen kicks into gear.
I hate to repeat this argument with you again, just curious, why US is ok with USAF with roughly 1000 F-35 and turn into 6th gen fighter, whereas PLAAF has to stick with in your case
All of which is to say, there may well be another good 800-1000 land based fighter aircraft that need replacement from 2025 to mid/late 2030s, on top of the demand for 1000 J-20s.
In fact, a rumor I heard recently was that, there haven't been a single J-10C in PLA paint since CAC started to export J-10CP to Pakistan. Have you ever realize that PLAAF is actually much more prefer long range J-20 rather than medium range fighter, and why can't after J-20 reach 1000, the production just continue on, say another 500? Given the major enermy of China is from the Pacific, long range is a must, so this is highly likely to be the case.

2022-2025: J-20, J-16, J-10C
2025-2030: J-20, J-XY land based, cessation of J-16 and J-10C shortly after 2025(?)
2030-2035: cessation of J-20 shortly after 2030(?), J-XY land based, 6th gen
2035-2040: 6th gen, cessation of J-XY after mid to late 2030s (?)"
or another possible case, with no J-XY at all;
2022-2025: J-20, J-16, J-10C
2025-2030: J-20, cessation of J-16 and J-10C shortly after 2025(?),
2030-2035: J-20, 6th gen
2035-2040: 6th gen

Seriously, we discussed this as well, how many landbased J-XY PLAAF will buy could very much depend on the evaluation results of J-35, which will only make it slower, so 2025-2030 is highly unlikely to start to massively produce landbased J-XY.

In fact, ask yourself, short range of fighter like J-10 even found its difficulties around Taiwan, why you are still expecting PLAAF to fall into this problem on their 5th gen or 6th gen fighter?
Yang Wei on his future airwarfare paper stated 'long range' as 2nd most import factor. This is also the key requirement for NGAD, if both side taken this so seriously, why they are still looking for a short range medium size 5th gen fighter?

I seriously suggest you take a rethink over this mindset that 'PLAAF must have a medium size 5th gen fighter', it has no concreate evidence rather than some wishful thinking on Weibo, it's not as cheap as you imagine, it's not going to give any maintaince advantage beside of open another huge supply chain, and it's contriduct to PLA A2AD idea.
 
Last edited:
Top