World's 5th gen fighters - relative strengths and weaknesses

Bltizo said:

It is likely that J-20 w/ WS-15 will see some structural differences but I would be surprised to see J-20 with that extent of modifications.

There have been studies of such a configuration before with a "not-J-20 aircraft" shown as a representative for what I believe was a damage simulation study. But at this stage I don't think we have any evidence that there will be a J-20 with such a large modification in the future.

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Chengdu's made clear they want the J-20 to evolve into a family of aircraft.

The biggest problem for the J-20 to be further upgraded is the lateness of the WS-15. We've heard nothing out of the rumor mill of late, and we have so-and-so aircraft engine manufacturer declaring they'll build around 5 WS-15 in the 2025 to 2030 timeframe, which is way too slow.

One big issue is the sizing of the J-20's current inlets. The airflow under the present DSI system is adequate for an Al-31 / WS-10X classed engine, but the airflow is insufficient for a F135 / WS-15 class engine.

The easy solution is simply to adjust the DSI; i.e, reduce the size of the bumps (and possibly increase their length) to accommodate the greater airflow needed, but an alternative solution would be to enlarge the inlets, creating greater body space and potential for the engines to be shifted to enlarge the weapons bay.

The measurements of the J-20 inlets are roughly the same, perhaps a bit larger, than on the Su-27 series for the Al-31 engines. It's a bit of a pity, to an extent, since larger inlets would have guaranteed better high-altitude / high-speed airflow, sufficient to allow the J-20 to have at least sustainment (requires afterburners to break Mach barrier, but can supercruise around Mach 1.3 without afterburners) supercruise. But that'd compromise low-altitude maneuverability as you'd end up with spillage drag from overflowing the inlets.

Inst said:

Chengdu's made clear they want the J-20 to evolve into a family of aircraft.

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Evolving into a family of aircraft doesn't mean that it's reasonable for us right now to expect a J-20 with the degree of changes you're suggesting like adopting an entirely different fuselage and engine configuration. It's almost an entirely new aircraft.

I'm not saying it's impossible, but as far as the potential modifications that could result in a family of J-20 variants, it is on the more extreme end.

Bltizo said:

Evolving into a family of aircraft doesn't mean that it's reasonable for us right now to expect a J-20 with the degree of changes you're suggesting like adopting an entirely different fuselage and engine configuration. It's almost an entirely new aircraft.

I'm not saying it's impossible, but as far as the potential modifications that could result in a family of J-20 variants, it is on the more extreme end.

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Consider how much the Su-27 has evolved. The Su-30 modification added canards, necessitating new actuators, and the Su-34 platform converted the Su-27 into a light bomber.

Biggest impediment, of course, is time. The Su-27 emerged and evolved at a time when the Russian armaments industry was wheeling from the collapse of the Soviet Union, meaning that there was limited funding for completely new designs. The Chinese plan to get a sixth-generation fighter up by 2035, and we're already at 2020 with the WS-15 very very late.

Then again, as you've suggested, the J-20B might be significantly different from the J-20A given the 25-37% increase in thrust, allowing the aircraft to carry much more munitions and payload without sacrificing maneuverability. And as I've said before, the TVC expected of the WS-15 could allow the aircraft to conduct a substantial redesign as the tailfins are no longer needed for yaw control.

Inst said:

Consider how much the Su-27 has evolved. The Su-30 modification added canards, necessitating new actuators, and the Su-34 platform converted the Su-27 into a light bomber.

Biggest impediment, of course, is time. The Su-27 emerged and evolved at a time when the Russian armaments industry was wheeling from the collapse of the Soviet Union, meaning that there was limited funding for completely new designs. The Chinese plan to get a sixth-generation fighter up by 2035, and we're already at 2020 with the WS-15 very very late.

Then again, as you've suggested, the J-20B might be significantly different from the J-20A given the 25-37% increase in thrust, allowing the aircraft to carry much more munitions and payload without sacrificing maneuverability. And as I've said before, the TVC expected of the WS-15 could allow the aircraft to conduct a substantial redesign as the tailfins are no longer needed for yaw control.

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I don't think I've suggested before that the J-20B may be significantly different from the J-20A, certainly not to the extent that I personally expect it to have significant alterations of the fuselage, weapons bay or engine configuration.

At present the only future J-20 variants that we are expecting or which are rumoured is the "J-20B" which will feature WS-15s which we do not know the extent of the eventual modifications on, and the second J-20 variant rumoured but not confirmed is the twin seater combat capable dual seater with enhanced command and also with a training role.


Everything else at this point is significantly more speculative, and while I'm not going to rule out the possibility of potential J-20 variants in the more distant future with significant modifications like you've suggested, I think speaking about these variants so casually as if they're done deals and as if everyone is expecting them to emerge like a forgone conclusion is silly.

Biggest problem for a strike J-20 would actually be the JH-XX Xian is rumored to be developing.

What happened with the Su-34 as a modification was that the Russians needed a replacement for the Su-24, and as Sukhoi already did the Su-27, they found that it would be simpler for them to just modify the Su-27 for the attack role. With the JH-XX, the attack role would be filled and there'd be less need to modify the J-20.

My basic issue is that the J-20 as a design is rather compromised to deal with the PLA's conflicting requirements and the limitations of Chinese engine technology. It's not as pure a stealth design as the F-22. The weapons payload, while better than the F-22, is roughly the same as on the F-35 so is inferior for a heavyweight stealth fighter. It's not designed for extreme maneuverability like the Su-57 is. And while the aspect ratio would imply that the aircraft is designed for and optimized for extreme speed, the J-20 is limited by the need to protect its stealth coating as well as the DSI inlets on the J-20. The only unique aspect the J-20 has going for it would be its lerx long-coupled canard lerx delta wing set-up, and even that has already been presaged by Rafale.

In other words, the J-20 is good against 4th generation fighters and in numbers adequate to 5th generation fighters, but it seems to lack its own advantages against competing 5th generation fighters. Where its advantages do lie are in the respective weaknesses of specific airframes (F-22 is only just getting upgraded with IRST, does not have EODAS, has an anemic weapons bay capacity, the Su-57 does not focus that much on stealth, the F-35 has poor agility), but it doesn't have anything world-beating.

On the other hand, as I've stated repeatedly, the J-20 has strong developmental potential from the basic design of the airframe. The limitation to the J-20 is constantly the engine, and if that limitation were lifted, the design could be modified to make it not simply a par aircraft, but something that could have a decisive advantage in one area or another.

Put another way, the J-10 is arguably better than a Block 50 F-16 or even a Block 60. The J-16 is arguably more capable than the F-15E. But all of these are last generation fighters. When it comes to 5th generation equipment, the Americans can tout their stealth and sensors on the F-35, the Russians can tout their kinematics on the Su-57, but what does China have?

As always, Inst, you demonstrate a remarkable skill to speak of your own opinions with in a manner that assumes your opinions are a widely agreed upon consensus by everyone, and set off to build an argument on it before even considering whether those opinions should serve as a premise for an argument in the first place.

Bltizo said:

As always, Inst, you demonstrate a remarkable skill to speak of your own opinions with in a manner that assumes your opinions are a widely agreed upon consensus by everyone, and set off to build an argument on it before even considering whether those opinions should serve as a premise for an argument in the first place.

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Described his behaviour perfectly and the exact same thing is happening at the Ladakh Flash Point thread. More nonsense talk about strike and interception and how the J-20 can only move this and that way. Even more daring speculation on the capabilities of the J-20's EODAS and airframe design. So tiring and so 2012.

I mean Blitzo, if you want to resort to personal attacks, it's quite clear that you don't have substantial evidence to defend the J-20, when the Song Wencong papers explained why the thinking that went into its design and how it was designed to accommodate Chinese technological limitations.

@nastya1 I'm not sure whether Beijing has climate controlled hangars in place in Tibet, but they can certainly be run from there. A while back the J-20s were used on Tibetan training exercises, presumably with Luneberg lenses, and were picked up by Indian air defenses.

@ougoah: which is one of the reasons Ladakh could go hot or that it would have been worthwhile for it to go hot. The Chinese military hasn't been used since the end of the Sino-Vietnamese border skirmishes, and India's military preparedness is quite questionable, with equipment half or one generation behind that of Western countries.

Inst, had many debates with you over the years about a range of things, but many of them -- especially pertaining to the J-20 for some reason -- tend to begin with some of your own opinions that you establish as if they are a widely accepted consensus that is beyond dispute, and then you build an argument from there.

Whether it is talking about the future potential variants of J-20, to J-20's strike potential, to even the general capability of J-20 whether on an aircraft to aircraft comparison or on a system of systems comparison, surely you must have caught on by now that it is good etiquette to first lay out your premises and see whether others agree with it or not before leaping into an argument and assuming that your premises are already unassailable.




If you want to have a discussion about the comparative strengths and weaknesses of the various 5th generation fighters like J-20 and its peers, that's fine, you can have that discussion (maybe in a different thread to not clutter this main flagship thread for J-20 news and pictures).
But talking about your opinions of J-20s as if they were widely accepted and then extrapolating an entire argument about future J-20 variants as if they're already on the cards? Yeah, no.