Shenyang FC-31 / J-31 Fighter Demonstrator

Hadoren · Mar 3, 2021

From my lurking, here's my understanding of the situation.

The J-20 is costly and hard to produce; production cannot catch up to the F-35. Therefore China needs a less expensive fifth-generation jet.

Land J-XY
A land-version J-XY would be best? It would be a double-engine medium-weight fifth-generation jet.

Double-Engine > Single-Engine
Double-engine would be better than single-engine because creating a new single-engine fighter would consume too much time and resources?

Medium-Weight > Light-Weight
A medium-weight jet would be created because it's not possible to create a light-weight fifth-generation jet?

Sometimes the big words and intelligence of our experts go over my head, haha. Is my understanding correct?

ougoah · Mar 3, 2021

Hadoren said:
From my lurking, here's my understanding of the situation.

The J-20 is costly and hard to produce; production cannot catch up to the F-35. Therefore China needs a less expensive fifth-generation jet.

Land J-XY
A land-version J-XY would be best? It would be a double-engine medium-weight fifth-generation jet.

Double-Engine > Single-Engine
Double-engine would be better than single-engine because creating a new single-engine fighter would consume too much time and resources?

Medium-Weight > Light-Weight
A medium-weight jet would be created because it's not possible to create a light-weight fifth-generation jet?

Sometimes the big words and intelligence of our experts go over my head, haha. Is my understanding correct?

I don't think that's actually the case. J-20 assumed production rate (just from released pictures of newer J-20s and which bases are receiving them) is pretty good. It only seems much slower than F-35 production because the F-35 production is pretty intense with what could only be many times more investment into production and many more partners investing into it.

But the relative gap and difference in production rates do indicate that J-20 numbers is simply never going to meet F-35 numbers. This doesn't mean a cheaper and easier to produce variant is the solution to this isolated problem. A cheaper and easier to build fighter is definitely less capable but it could be worthwhile if what it offers is enough justification and fills the capability and numbers gaps where needed. Not to mention also positioning gaps. Sort of like J-10 being positioned all over China in a greater spread than J-11 and J-16 not simply because it has shorter range.

Deino · Mar 3, 2021

Crang said:
26:06 in the video. Wonder if the serial number means anything that you plane watchers know things about.

Unfortunately it is not a serial number but a demonstrator number most likely meaning "Project 310" & "aircraft no. 01"

gelgoog · Mar 3, 2021

Hadoren said:
From my lurking, here's my understanding of the situation.

The J-20 is costly and hard to produce; production cannot catch up to the F-35. Therefore China needs a less expensive fifth-generation jet.
...

The F-35 isn't particularly cheap either. It still has a low availability rate and high maintenance costs. The USAF leadership recently announced they are investigating the idea of a 4++ or 5- generation complement to the F-35 which would make up the bulk of USA fighter aircraft in the future.

I think there is a high possibility the FC-31 engines might be used in a single engine UCAV which could then be used in both naval and land based configurations. But the use of the FC-31 proper on land based configurations seems more limited to me. While a twin engine aircraft might make sense in remote or coastal defense applications where increased engine out reliability would be helpful it wouldn't make sense for a general purpose low cost combat aircraft I think. There is a high possibility the Chinese might simply opt for a cheaper aircraft similar to something like the KFX which has some stealthy characteristics but still carries weapons externally. Or they could opt for a different configuration.

I don't know why people assume a weapons bay below the engine like on the F-35 is the only option. They might as well go for two weapons bays one on each side of a center engine. Or have a short width long length center bay or two in between a twin engine with the rest of the weapons being carried on external hard points much like the Su-57.

In short I think if we do see the FC-31 in a land based configuration the most likely first customer would be the PLANAF coastal air arm for the reasons I stated previously. Namely that the extra engine would allow more reliability while doing patrols over the sea.

silentlurker · Mar 3, 2021

gelgoog said:
I don't know why people assume a weapons bay below the engine like on the F-35 is the only option. They might as well go for two weapons bays one on each side of a center engine. Or have a short width long length center bay or two in between a twin engine with the rest of the weapons being carried on external hard points much like the Su-57.

I think a singular bay is the best layout for carrying a diverse loadout of ordinance.

crash8pilot · Mar 3, 2021

In any sort of coastal defense mission, I'd imagine a land based J-XY would have a minimum loadout of 2x KD-88 ASMs/YJ-83 AShM (which might I add are really BIG in size) alongside 2x PL-15s so that it won't require a fighter escort to counter enemy air resistance.... I struggle to see how all those missiles will physically fit in two internal weapons bay, regardless if the weapons bays are laid out F-35 style or Su-57 style.

Sure you could hang big bombs/missiles on external pylons, which then throws stealth out of the window. But then in that case the PLA might as well launch them from a J-16, which inherently has a much larger weapons loadout capability. The whole point of the FC-31/J-XY is to deliver a STEALTH fighter.

latenlazy · Mar 3, 2021

gelgoog said:
The F-35 isn't particularly cheap either. It still has a low availability rate and high maintenance costs. The USAF leadership recently announced they are investigating the idea of a 4++ or 5- generation complement to the F-35 which would make up the bulk of USA fighter aircraft in the future.

I think there is a high possibility the FC-31 engines might be used in a single engine UCAV which could then be used in both naval and land based configurations. But the use of the FC-31 proper on land based configurations seems more limited to me. While a twin engine aircraft might make sense in remote or coastal defense applications where increased engine out reliability would be helpful it wouldn't make sense for a general purpose low cost combat aircraft I think. There is a high possibility the Chinese might simply opt for a cheaper aircraft similar to something like the KFX which has some stealthy characteristics but still carries weapons externally. Or they could opt for a different configuration.

I don't know why people assume a weapons bay below the engine like on the F-35 is the only option. They might as well go for two weapons bays one on each side of a center engine. Or have a short width long length center bay or two in between a twin engine with the rest of the weapons being carried on external hard points much like the Su-57.

In short I think if we do see the FC-31 in a land based configuration the most likely first customer would be the PLANAF coastal air arm for the reasons I stated previously. Namely that the extra engine would allow more reliability while doing patrols over the sea.

But is it cheaper to have to develop a *third* stealth fighter design or to simply appropriate one that’s already being used for another program? Literally the only part of the land based PLAAF J-XY idea that seems to be contentious is how many engines are ideal for a “low cost” stealth fighter, and as I’ve mentioned already the difference in cost between one very large engine and two medium sized ones is really not that significant. Whether it makes any sense to develop a *third* fighter design bears even more emphasis in a KFX comparison, since the KFX is, like the J-XY, also a twin engined midweight fighter.

You could go for a dual side bay design instead of a single ventral bay, but it’s not going to change anything about the added structural weight needed to carry payloads internally.

Dishi · Mar 3, 2021

Hadoren said:
From my lurking, here's my understanding of the situation.

The J-20 is costly and hard to produce; production cannot catch up to the F-35. Therefore China needs a less expensive fifth-generation jet.

Land J-XY
A land-version J-XY would be best? It would be a double-engine medium-weight fifth-generation jet.

Double-Engine > Single-Engine
Double-engine would be better than single-engine because creating a new single-engine fighter would consume too much time and resources?

Medium-Weight > Light-Weight
A medium-weight jet would be created because it's not possible to create a light-weight fifth-generation jet?

Sometimes the big words and intelligence of our experts go over my head, haha. Is my understanding correct?

Actually China doesn’t need a less expensive 5th gen jet, the J-20 + J-10C + J-16 is a very robust and cost effective package for the foreseeable future. The backbone of the PLAAF’s tactical fighter fleet will continue to be based on j-10 for a long time because;

1) single engined fighters are cheaper, remember the most expensive component on a fighter is the engine, it’s cheaper to procure, maintain and replace. For a country the size China, you need the numbers on a budget

2) You don’t need stealth for every scenario, stealth is expensive and maintenance heavy which translates to low sortie rates. You need stealth on the opening of the conflict, to take out air defenses and gain air superiority, you want stealth on the tip of your spear, everything after that is all about sustained sortie rate. Stealth is not needed to provide CAS or against countries like Vietnam

3) Upgradability of J-10 and J-16 platforms in terms of weapons, avionics and engine will ensure that they’ll have a long useful life that provide new capabilities at a fraction of the price.

Building a new platform and completely equipping the whole force with 5th gen fighter is foolish and uneconomical, something not even the deep pockets of the pentagon can sustain in the long run. You can see that the US have implicitly admitted the failure of that strategy with the order of new build F-15EX and proposal for a 4++gen fighter to replace F-16s. That is a validation if not a copy of the Chinese procurement strategy, which kinda proved the Chinese strategists got it right all along and didn’t get blinded by money or the MIC.

kentchang · Mar 3, 2021

Dishi said:
Actually China doesn’t need a less expensive 5th gen jet, the J-20 + J-10C + J-16 is a very robust and cost effective package for the foreseeable future. The backbone of the PLAAF’s tactical fighter fleet will continue to be based on j-10 for a long time because;

1) single engined fighters are cheaper, remember the most expensive component on a fighter is the engine, it’s cheaper to procure, maintain and replace. For a country the size China, you need the numbers on a budget

2) You don’t need stealth for every scenario, stealth is expensive and maintenance heavy which translates to low sortie rates. You need stealth on the opening of the conflict, to take out air defenses and gain air superiority, you want stealth on the tip of your spear, everything after that is all about sustained sortie rate. Stealth is not needed to provide CAS or against countries like Vietnam

3) Upgradability of J-10 and J-16 platforms in terms of weapons, avionics and engine will ensure that they’ll have a long useful life that provide new capabilities at a fraction of the price.

Building a new platform and completely equipping the whole force with 5th gen fighter is foolish and uneconomical, something not even the deep pockets of the pentagon can sustain in the long run. You can see that the US have implicitly admitted the failure of that strategy with the order of new build F-15EX and proposal for a 4++gen fighter to replace F-16s. That is a validation if not a copy of the Chinese procurement strategy, which kinda proved the Chinese strategists got it right all along and didn’t get blinded by money or the MIC.

I agree too. Why add more logistics headache instead of focusing on the next generation.

For the Air Force, until such unlikely time when China has acquired 'permanent' foreign bases, J-10C is short-legged but more than adequate to maintain the current OrBat, ensuring airbases/chain-of-command are well-maintained, and pilots/mechanics have low-maintenance planes to practice in.

For the Navy, a carrier-based J-20 counterpart is essential and I do see a long life ahead for the J-15 as the J-16 equivalent. Giving the FC-31 a significant strike role is not a good trade-off for extended range.

latenlazy · Mar 3, 2021

kentchang said:
I agree too. Why add more logistics headache instead of focusing on the next generation.

For the Air Force, until such unlikely time when China has acquired 'permanent' foreign bases, J-10C is short-legged but more than adequate to maintain the current OrBat, ensuring airbases/chain-of-command are well-maintained, and pilots/mechanics have low-maintenance planes to practice in.

For the Navy, a carrier-based J-20 counterpart is essential and I do see a long life ahead for the J-15 as the J-16 equivalent. Giving the FC-31 a significant strike role is not a good trade-off for extended range.

It seems the idea of developing tactics with 4.5 gen fighters to fight 5 gen fighters received quite the blow when the J-20 annihilated the competition in its initial introduction. If China faces an environment where the main forces potential adversaries field are 5th gen, assuming China’s resources aren’t constrained having a larger mainstay 5th gen fleet will *need* to be a serious consideration for force planning. If the US ends up cutting back on F-35s and ends up going with some kind of 5- or 4.9 gen solution instead, this alleviates the pressure for China to need to procure more 5th gen fighters. That said, it would be very bad, risky, and extremely dangerous planning for China to wait for the US to backtrack on their commitment to a 5th gen mainstay fleet only hoping for the best. At the very least China needs to be able to reach a place in its R&D process to have actionable options. It’s much safer for your force balance to have a 5th gen design that you’re committed to being a mainstay and then dialing back production if your potential adversaries also dial back their numbers than to not have anything at all. Furthermore, nothing dictates that the higher flyaway costs the F-35 ended up with is unavoidable and must be the typical costs China should expect. China *has* had a record of developing equivalent capabilities more cheaply than the US before. A paradigm example of an efficient well run procurement system the Pentagon is not.

Shenyang FC-31 / J-31 Fighter Demonstrator

Hadoren

Junior Member

ougoah

Brigadier

Deino

Lieutenant General

gelgoog

Brigadier

silentlurker

Junior Member

crash8pilot

Junior Member

latenlazy

Brigadier

Dishi

New Member

kentchang

Junior Member

latenlazy

Brigadier