Shenyang FC-31 / J-31 Fighter Demonstrator

Yeah, and the J-31 also couldn't support the Flanker engines, as the flanker engines are designed for a larger aircraft. The J-31's engine size is more attuned to the ones on the F-18s and the Mig-29s. Same with the radar, it has a smaller nose cone than the J-11s and thus would have to use a less powerful radar.

That said, the J-31 does have a pretty large wing area for its size; when I measured it, I got roughly 50 m^2 meaning that with 17500 kg take-off weight, which is AVIC's figure, and honestly a bit questionable, it has 350kg/m^2 wing loading, comparable to the F-22's, and with 21000 kg it sports 420kg/m^2, which is pretty decent for a carrier fighter.

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One thing I suspect is that for the J-31, it was designed for a higher level of technological capability than the J-20. That's because the J-20 as a fifth-gen needs to be out as soon as possible, while the J-31 is intended as a carrier fighter. As a carrier fighter, the bottleneck is less the aircraft itself and more the Chinese carrier program, which is still in its infancy and is not expected to turn out CATOBARs until 2020, at least. That means the J-31 can depend on riskier technologies than the J-20, because even if the J-31 program works as smooth sailing, it won't be deployed in bulk until China's carrier fleet is ready.

Deino said:

To admit I'm honored by Your question but I think there are several other, who could explain or answer much better than me ... most of all I think of 'Bltizo', 'tphuang' and 'siegecrossbow' ... and I'm sure I missed many more.

But let my try: I think overall airframe wise and in regard to its configuration and general layout it is a promising design, which - like Bill Sweetman already mocked - would be what the US JSF could have been without the penalty of the VSTOL-version. As such I'm confident that even with current 'standard' items derived from the current Flanker-series a very potent fighter could be build.

The weak point however is the powerplant since the current RD-33 is simply too much out of date, has a too low thrust and most like to high fuel consumption ... and esp. is too smoky ! Again as such if a new powerplant could be used, the all said above could be done.

Deino

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Thanks Deino and I think you have no need to be over modest.
I also appreciate Inst's point and could rephrase to mean using systems already developed or available to Shenyang, to proven standards, but not necessarily dedicated to the Flanker varients.

I think though Deino, the heart of my question is that, if the airframe is itself a major improvement, why not make an initial in service model that utilises it, albeit with versions of proven other systems. The only reason why not that I can think off, is that the difference in cost between the new and existing air frames is so considerable, relative to the increase in performance, that it makes poor financial sense to commit.

I have no idea if this is the case and only know that the research budgets for full 5th gen planes surpasses the gross GDP of whole regions of many developing nations!

What is not clear is where exactly the cost of these programmes falls and what proportion of it relates to the Airframe. Is it the case, that the Airframe cost itself is so great that it really needs to be matched by much higher performance internal systems to warrant the expenditure?

These are questions that have lurked in the darkest recesses of my skull for many years, but, as not being a techie, have never dared to ask.

Deino said:

Seems as if our friend '31001' is back ! ... cant wait for the seond prototype !

Deino

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I'm wondering if they will copy the J-20's putting the bracing bar inside the canopy for their second prototype.

Deino said:

Seems as if our friend '31001' is back ! ... cant wait for the seond prototype !

Deino

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What is that on the inner surface of starboard vertical fin?

SampanViking said:

Thanks Deino and I think you have no need to be over modest.
I also appreciate Inst's point and could rephrase to mean using systems already developed or available to Shenyang, to proven standards, but not necessarily dedicated to the Flanker varients.

I think though Deino, the heart of my question is that, if the airframe is itself a major improvement, why not make an initial in service model that utilises it, albeit with versions of proven other systems. The only reason why not that I can think off, is that the difference in cost between the new and existing air frames is so considerable, relative to the increase in performance, that it makes poor financial sense to commit.

I have no idea if this is the case and only know that the research budgets for full 5th gen planes surpasses the gross GDP of whole regions of many developing nations!

What is not clear is where exactly the cost of these programmes falls and what proportion of it relates to the Airframe. Is it the case, that the Airframe cost itself is so great that it really needs to be matched by much higher performance internal systems to warrant the expenditure?

These are questions that have lurked in the darkest recesses of my skull for many years, but, as not being a techie, have never dared to ask.

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Interesting idea, and it think it certainly has merit, especially for the PLAN.

I think the main reason why the PLAAF, and maybe even the PLANAF, is not giving the J31 that much interest is because they have their eye on the J20. Why settle for a 5th gen-like fighter when you can have a full spec 5th gen thoroughbred instead? The weight category issue also comes into play, and would be a lot like the choice the PLAAF originally faced when choosing between the medium weight Mig29 and the heavyweight Su27.

Unlike the Americans, I don't think the Chinese have any intentions or see any need to try and move to a full stealth fighter fleet. So both services will probably only get one stealth type since the acquisition, training and logistics costs would make purchasing a second stealth type prohibitively expensive.

The Chinese would have taken note of what a hash the Americans made of their 5th gen acquisition decision by cutting F22 numbers to chase the fantasy of a much cheaper F35 only to end up getting a far less capable fighter years behind schedule and which costs close to, if not more than the much more capable F22. They would be acutely aware of the similarities and keen to avoid the same pitfall.

The fact that the J31 seems considerably further behind than the J20 to becoming operational would not help the J31 one bit.

I think the J31 is most like the JF17 - a perfectly capable and respectable fighter doomed by bad timing which pitches it in direct competition of a far superior model, even if they two are not exactly in the same weight class. The JF17 parallel does not end there though, as there is a decent chance it will find success on the international export market as a privately funded project, maybe getting development funds from an interested foreign country (potentially Pakistan again), and ultimately securing much greater international export success that the J20 since it won't be subject to the same PLA-imposed restrictions.

From a project management prospective, SAC would be best served to follow your suggestion to get the J31 marketable ASAP and present it as the Mig21/F16 of the 5th gens, get some investment and maybe even orders so they can gradually improve it and ultimately bring it up to full 5th gen specs.

Whether SAC will do that or still try to chase the PLA white whale is the key question.

Deino said:

Seems as if our friend '31001' is back ! ... cant wait for the seond prototype !

Deino

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Yes, and that landing gear seems somewhat light for a carrier bird, maybe not, but it looks on the smallish side to the brat??? and yes I realize it is a much lighter aircraft than the J-15...

I'm not sure, I think the J-31/J-35 could be a capable strike fighter if it was fully developed, but unlike the J-20, in its initial stage of production it is a lot less capable. The only advantage the J-31/J-35 would have would be in having a longer weapons bay, but on the other hand, it would have an inferior radar compared to the J-20, it would be unable to supercruise, and without TVC it would be a lot less maneuverable than the J-20. So, the J-31 would be better and more effective against enemy surface ships, while being outclassed by the J-20 at everything else.

In the Chinese context, it makes more sense to focus on air superiority aircraft first, because if you can't keep air superiority, your strike aircraft and bombers will be expensively shot down. Only once the PLAAF has a reasonable guarantee of maintaining air superiority does it begin to make sense to begin focusing on bomber aircraft and strike aircraft for the purposes of exploiting your air power. Hence why the J-31 / J-35 airframe seems to require 2020s-era technologies to be effective (namely high thrust TVC engines to enable supercruise and supermaneuverability on a relatively draggy airframe).

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By the way, I also redid measurements recently and it appears that both J-20 and J-31s have weapons bays at about the same length. There's something called a SALSCM missile for the Chinese, for Stand-off Air-Launched Supersonic Cruise Missile, which is about 4.1 meters long, but with 56 cm diameter, sporting a 400km range with a supersonic terminal velocity. I'm not sure if it, or variants of it, would fit in the J-20 and J-31, but that's a matter of depth, not length. It's also a matter of heavy external fins, which definitely would not fit in the launch bays of the J-20 and J-31, but who knows, maybe they could be made to fold into the missile body when in flight.

But if both the J-31 and J-20 have the same weapons bay length, then the J-31 has no superiority over the J-20 when it comes to strike capabilities. Consequently, there is no reason to fast-track the J-31 program, since a J-31 equipped with current engines and avionics has no advantage over a J-20 fast-tracked with current engines and avionics.

i noticed the j-31 has 2 engines, unlike the f-35?! but, good work china, really nice fighter jet....
have the j-31 or the j-20 / j-18 external weapon stations, or only internal??

valapak said:

i noticed the j-31 has 2 engines, unlike the f-35?! but, good work china, really nice fighter jet....
have the j-31 or the j-20 / j-18 external weapon stations, or only internal??

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very observant of you sir for noticing the two engines on the J-31 and yes have external WS on J31/20 and as for the J-18 here is what some people think

nkvd said:

very observant of you sir for noticing the two engines on the J-31 and yes have external WS on J31/20 and as for the J-18 here is what some people think

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Hi ... and I try to be polite: I have some problems to understand You correctly.

Anyway, there are no WS - at least no Chinese WS-series engines - on any of these two fighters: The J-20 is powered by a version of the Russian AL-31FN (maybe series III) and the J-31 uses RD-93. (Or maybe You simply meant WS in the maening of "turbofan engine" !??).
Regarding the so called J-18 .... simply forget that type, it's nothing more than a FAKE, a hoax, ...

Deino