J-20 5th Gen Fighter Thread VI

taxiya said:

It is not an issue for me which got the fancy name, but it is important to give a name to differentiate them (F-35 type of composite vs. PCB like later material) when having a discussion without confusion.

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Trouble is, you can't rely on the label "metamaterial" to make that distinction, because of the recent nature of this term. Concurred, it's reasonable to assume that everything now called a metamaterial is probably a PCB structure, but (simply because some pre-date the word) not all PCB-based RF materials are flagged as metamaterial in literature even though the term would be perfectly appropriate. The Typhoon radome FSS is most definitely a PCB (again, what does that photo look like to you?) and while the F-22 IFB microstructure has never to my knowledge been revealed, it is known to be manufactured as a PCB - I posted a source in our previous debate.

So we have two examples dating to the 1990s which combine conductive and dielectric materials in deliberate geometrical micro-patterns via a PCB manufacturing process to achieve RF properties (bandpass) that none of the constituents exhibits either on its own or in an irregular structural arrangement. Doesn't this scream "metamaterial" to you? Your argument is founded on a rigour in the usage of this word that apparently does not exist, so we have no way of knowing whether the source mentioning metamaterials on the J-20 merely identifies a version of established FSS technology by a more modern name or if it's a genuinely new application. Without specifics, it's nothing more than speculative inference.

taxiya said:

The publications that I read which used metamaterial were all about the PCB like. The first link is the metamaterial that I was talking about which was in experiment in 2001 some time after F-35 program started. Can you say this type was used by F-35?

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No, but as mentioned I certainly can for the F-22 and Typhoon, which needless to say considerably pre-date the F-35. Again, I agree that (at least for the purposes of this discussion about engineered RF materials on aircraft) PCB technology is probably a decent differentiator, but that does nothing to remedy the fact that at least these two examples are confirmed to have existed for a long time. So long in fact that the term metamaterial was not even around yet when they were developed and is therefore not normally associated with them in literature.

taxiya said:

It is a retro-application of the name metamaterial like today's renaming everything trend.

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Well, it's not just sophistry but a very sensible argument. If it does fit the description perfectly, why decline to adopt the designation metamaterial for something merely because it was first published prior to some arbitrary cut-off date? Take the term supercruise, can what Concorde did be considered supercruise? The only reason not to is basically that the Lockheed-Martin PR department came up with it well after Concorde had entered service.

Inst said:

The word "dedicated" is somewhat bolted on. You're using that to go blast mainstream media when we know that mainstream media often gets technical details wrong. The problem I have with you and latenlazy is the power game and the search for authority, i.e, the desire to say "based on our sources and our analysis so and so shouldn't be trusted". The downplaying of particular sources and particular agents is somewhat arrogant and is a "power move", in the same way certain politicians or organs going on about "fake news" is likewise a power move.

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The word "dedicated" is entirely appropriate when the mainstream defence media's theory of J-20's role is that it is limited to the high speed interceptor or high speed strike role due to its design.

And no, there are certain sources where even cursory interrogation of their claims is enough to be greatly skeptical as to new claims that are made.
There is a reason why people like Minnie Chan are not taken seriously, not to mention others like Axe or Majumdar.

I see something STRONGLY nationalistic and problematic in the desire to call the J-20 an air superiority aircraft. You can't simply go to the Song Wencong design documents to claim that the J-20 is intended to dogfight (because that's how you get out of the interceptor arguments most strongly) because the MiG-31, likewise, was designed for higher maneuverability than the MiG-25 it was based off. You have to acknowledge the basic airframe characteristics and shown performance (if we've seen the J-20 run on afterburners, the afterburner excuse is no longer valid for merely average or 4th gen maneuverability).

I'd also argue that this approach is foolish. The issue with the "J-20 is an interceptor" narrative isn't that the interceptor appellation is wrong, but that the notion that interceptors can't successfully challenge air air superiority and strike aircraft is a mistaken one. The label of interceptor or fighter-interceptor more rightly describes the airframe's role and characteristics at this point in the development cycle, and trying to change the designation instead of pointing out that interceptors (especially if you note trends in interceptor design toward more subsonic maneuverability) can beat strike and air superiority fighters is asking the reader to suspend logic. The conclusion the outside reader is more likely to come to is "the J-20 might have been designed to be an air superiority aircraft, but the designers failed". They can point to, for instance, the fact that the J-20 lacks a gun as evidence, or that the J-20 has not shown the show-stopping acrobatics of the F-22 or Su-57 equipped with TVC.

What is more effective in asserting the J-20's credibility is instead pointing out that interceptors are effective against American strike aircraft as shown by the MiG-25 record in Desert Storm and that there exist tactics wherein the MiG-31 can defeat older F-15s.

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I've never suggested that the J-20 was intended to excel at dogfighting.
I've never said that interceptors are incapable challenging air superiority fighters or strike aircraft. Obviously interceptors can do challenge air superiority fighters or strike aircraft.

However everything we've heard from official Chinese industry or PLAAF individuals (including Dr Song's paper, including J-20 pilots, J-20 test pilots, including even official AVIC brochures) -- should be enough for us to dispel the notion that J-20's design was oriented it to being a dedicated interceptor or high speed striker.

If you dislike the word "dedicated" that is fine.
Feel free to replace it with any variety of description so long as you understand that the aircraft's design does not limit it to only having the roles of an interceptor or high speed striker.

The "desire" to call J-20 an air superiority fighter is a reflection of what the performance that the aircraft is likely to have based on:
A: what we've been able to glean from various industry or air force individuals,
B: based on what we can see from the aircraft's design and what we know of the aircraft's intended aerodynamic performance from Dr Song's paper
and C: based on an assessment of the rationale for what kind of aircraft the PLAAF would have required for their first and primary next generation heavy fighter aircraft.



Continuing to say that interceptor aircraft can be effective in the air to air role is unnecessary because nowhere in my previous arguments have I ever suggested that interceptor aircraft cannot be used to kill air superiority fighters or strike fighters.
Yes, Mig-25s have shot down aircraft in Desert Storm, and yes Mig-31s can be effective against opposing air superiority aircraft.
But it is irrelevant to the premises for my argument.

Inst said:

Tyler Rogoway's characterization of the J-20 as a fighter-interceptor is the best possible description of the aircraft. The Chinese can say its mission is to claim air superiority, but in practice, it's going to do so using the tactics of an interceptor. The Fighter-Interceptor term, for the casual observer, is the best way to describe it and think of it. It can hold its own WVR, but it excels more as an interceptor.

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You'll probably consider this another "power play", but if you find yourself agreeing with Tyler Rogoway then it's a good indicator that you need to re-examine your position. Rogoway isn't as bad as Kyle Mizokami or Minnie Chan, but that's a very low bar to clear.

Substantively, the premise that the J-20 was designed to "shoot-and-scoot" is contradicted most strongly by the J-20's characteristics themselves. Why would it include control surfaces like the canards and ventral strakes for improved aerodynamics if all it needs to do is fly fast in a straight line and shoot? Especially since such surfaces negatively impact RCS to at least some degree, and a plane defenseless in WVR needs all the stealth it can get.

This was touched off by the claim that the J-20 can fly really fast. Great! It's an air-superiority fighter that can fly really fast because of its wing sweep and manoeuvre really well because of its use of canards, LERX, strakes, and an advanced lifting body. That speaks to the brilliance of Dr. Song - he was able to find a region of the design space where a highly stealthy fighter with outstanding speed and manoeuvrability could be conceived.

Inst said:

or that the J-20 has not shown the show-stopping acrobatics of the F-22 or Su-57 equipped with TVC.

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I would argue that the climb at 4:25 is pretty show-stopping, not because the angle or speed are particularly aggressive, but because of the remarkable coupling between the canards and main wing through the LERX that the condensation demonstrates:
Even more impressive is that this was done with a mediocre engine without TVC. When the WS-15 is ready, the J-20 will be the closest thing there is to a perfect 5th generation fighter.

Even taking the basic Eurofighter design, that does not make a good dash and scoot interceptor design. You should be able to tell a dash only interceptor right off from a general air superiority fighter or dogfighter.

Being optimized for high speed all the time means you need high efficiency in high speed cruise.

The longer the plane, the better it is for this regime. Shorter planes favor maneuverability.

The center of gravity of the plane is towards the front and not the rear. A high northern center of gravity means the aircraft is very stable at the expense of maneuverability, as a vehicle that is front heavy is is less responsive to turning forces. That's what you need for a high speed dasher. A plane with a low or southern center of gravity to the rear means its unstable and thus also highly maneuverable, due to the front being light and highly responsive to pitch and turning forces. Often these type of aircraft need FBW.

Planes with movable canards tend to be more maneuverable for that reason. The canards make it easier to apply pitching forces to the nose of the aircraft simply by lift. A tailed elevator needs to push down (lift decrease) against the rear, which maybe the center of gravity, which can be more resisting to turning forces, requiring greater deflection of the control surfaces and thus increased drag. The canards also enjoy a fresh stream of air while tailed elevators have to take the air stream downstream from the main wings, which may already be partly turbulent.

Comparison of wing aspect. Interceptors tend to have low wing aspect, dogfighters tend to have high wing aspect. Planes with squared ratios (equal length chord, equal length span) of wing aspects are meant to fill both roles (Jack of all trades, masters of none).

Comparison of wing loading. Interceptors tend to have high wing loading, which improves stability and ride, while dogfighters tend to have low wing loading, which increases lift and pitch. However, note that aircraft can also use their bottoms as a lifting surface and canards also constitute lifting surfaces.

Modern fighters, past the F-18 that is, which is a classic dogfighter, tend to be generalists because both interceptor and dogfighter are both valid. The Interceptor design also tends to favor strikers. My impression of the J-20 is that its a generalist.

Tyler ironically is a Blitzo acolyte, who followed the line that the J-20's bays were too shallow to do real strike (it's not, it's roughly in the F-35 class for volume).

As for the canards and LERX, the canards aren't actually a viable line. The canards are long-coupled, as in the Eurofighter (which also has LERX now with AMK) and differing from the close-coupled canards. The LERX and strakes are a better argument, but we go back to the MiG-31.

The MiG-31, for instance, is capable of decent sustained turn rates that likely put it on par or better than 3rd gen fighters. Moreover, it has sacrificed the max speed of the MiG-25. Is it all of a sudden an air superiority fighter?

The other claim is that the J-20 is a 'perfect' air superiority fighter. This is why I strongly dislike these types of attempts to defend the J-20's 'honor'. The J-20 is not. Period. It's running canards that no one puts on a stealth aircraft if they can help it. The radical claims that canards make the aircraft categorically LO are unfounded, of course, but they add a second plane to the J-20, even if you have planar alignment. The stealthiest canard attempt, ironically, is not the NATF canards where the canards were above the main plane, but the X-36 and IIRC the Korean stealth fighter concept where the canards are coplanar to the main wing.

And that's my entire problem with attempts to categorize the J-20 as air superiority when attrition will be a problem with any heavy weight design. You end up emphasizing that the J-20 is superior in every metric, when it's not and that's the entire point.

The best fifth gen comparison is rather the YF-23, wherein the YF-23 outsped and outflew the YF-22, alongside outstealthing it, something the J-20 with its 8 planes cannot, not without better RAM. But the J-20, being long-coupled with plans for TVC, is clearly designed for superior supersonic manueverability and performance and that's what matters most about the J-20.

An old image from Zhuhai...

@Tam

The Eurofighter, like the J-20, is described as having exceptional supersonic manueverability. It has a higher thrust-weight ratio than the Rafale, and also sports long-coupled canards which are better for supersonic than subsonic performance.

I'll post a riposte to Blitzo next, but the big problem is that people both in the mainstream media and here see 'interceptor' as bad when it's one of the few remaining ways to make heavyweight stealth aircraft work in an air-to-air engagement. The majority of Third Generation fighters, for instance, were fighter interceptors. The fact that the J-20 is a fighter-interceptor does not make it worse against the F-22 and F-35, it makes it better. The only real alternative with heavyweights is to throw in Su-57s, hope they don't get slaughtered before the merge, and hope they can sufficiently attrit F-22s and F-35s in the merge while taking heavy casualties themselves.

As mentioned before, an air superiority fighter wants to kill you in BVR, then either close in to finish you off or run away with better max speed. This no longer works in Fifth gen land because stealth makes BVR an incredible headache.

An interceptor also wants to kill you in BVR, but it just wants to run away afterwards. The ability to hit and run makes interceptors much more capable than air superiority fighters in Fifth Gen Land. The high manueverability (supersonic) of the J-20 makes it that much more agile as a shoot-and-scooter.

Put it another way, if we thought of the J-20 as a 9G capable MiG-31 with stealth and TVC, how insulting would it be to the J-20? I'd say not at all, and it'd be a term of praise. Note that the MiG-41 hypersonic interceptor is way more promising than the Su-57.

@Tam
The Mig25 is a high dash interceptor. Until one landed in Japan with a defector pilot the West was convinced that it was an Air superiority fighter. From a glance Mig25 and F15 as well as Mig29 have features that overlap. At a distance most pilots can’t tell one from another.
What decides what one is built for is the engines and how it’s built. Mig25 was only built to take 5 Gs of force and its engines were designed for high speed not low.
Mig31 totally redesigned the aircraft yet is almost identical externally yet it has better G load and Engines more suited to low speed although still not an Air superiority fighter.

In the case of J20 we don’t know how much G load it can take but the engines we know are all around performers. Fitted in 2 other fighters of the Air superiority class The Flanker series and the Pakfa it’s also used in what could be classed as a light Air superiority / medium fighter J10. That I think makes a fairly conjectural for it also being aimed to that role the one thing that holds it back is lack of a close on weapon at the moment. What good is being a knife fighter if you lack a knife.

Inst said:

Tyler ironically is a Blitzo acolyte, who followed the line that the J-20's bays were too shallow to do real strike (it's not, it's roughly in the F-35 class for volume).

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The J-20's weapons bays look almost identical to the F-22's. Even if the total volume is the same or even greater than an F-35's, that doesn't mean it can accommodate strike munitions if the bays aren't deep enough. Both volume and linear dimensions must be sufficient. See, this is the problem with engaging seriously with you: not only are your facts faulty and your logic unsound - which is forgivable if annoying, you are remarkably stubborn. But there's a much more serious problem with you that I didn't get until now...

Inst said:

The other claim is that the J-20 is a 'perfect' air superiority fighter.

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ZeEa5KPul said:

When the WS-15 is ready, the J-20 will be the closest thing there is to a perfect 5th generation fighter.

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Either you're a liar or you're cognitively ill-equipped to be having these conversations, choose one.

Inst said:

The radical claims that canards make the aircraft categorically LO are unfounded, of course, but they add a second plane to the J-20, even if you have planar alignment.

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You have zero credibility to be making any such claim. If I read the statement "planes fly" from you I would want proof.

Inst said:

Tyler ironically is a Blitzo acolyte, who followed the line that the J-20's bays were too shallow to do real strike (it's not, it's roughly in the F-35 class for volume).

As for the canards and LERX, the canards aren't actually a viable line. The canards are long-coupled, as in the Eurofighter (which also has LERX now with AMK) and differing from the close-coupled canards. The LERX and strakes are a better argument, but we go back to the MiG-31.

The MiG-31, for instance, is capable of decent sustained turn rates that likely put it on par or better than 3rd gen fighters. Moreover, it has sacrificed the max speed of the MiG-25. Is it all of a sudden an air superiority fighter?

The other claim is that the J-20 is a 'perfect' air superiority fighter. This is why I strongly dislike these types of attempts to defend the J-20's 'honor'. The J-20 is not. Period. It's running canards that no one puts on a stealth aircraft if they can help it. The radical claims that canards make the aircraft categorically LO are unfounded, of course, but they add a second plane to the J-20, even if you have planar alignment. The stealthiest canard attempt, ironically, is not the NATF canards where the canards were above the main plane, but the X-36 and IIRC the Korean stealth fighter concept where the canards are coplanar to the main wing.

And that's my entire problem with attempts to categorize the J-20 as air superiority when attrition will be a problem with any heavy weight design. You end up emphasizing that the J-20 is superior in every metric, when it's not and that's the entire point.

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Aside from the design documents that are available, stressing an air combat role and structural design choices to specifically deliver maneuverability in certain regime, which being public is already a pretty remarkable win for intelligence on the aircraft, what more do you want?

Its a stealth aircraft, and we have two general categories of those at the moment - Fighter and Bomber. In the role of fighter, obviously it is meant to dominate the aerial component of the battle space. Any stealth fighter will leverage its see-first shoot-first advantage in BVR where possible. This one (J-20) is confirmed equipped with two IR short-range a2a missiles and an EOTS for WVR combat. How well it performs in a specific role now, versus later when certain upgrades become available (WS-15 etc) are irrelevant to the aircraft's intended purpose. It may carry SDB like ordnance for a given mission, that does not change its overall design mission from air dominance to bomber.

Everything else just seems like word play. Who is calling J-20 a 'perfect' air superiority fighter and where does 'honor' enter into it? Call it multirole if it makes you feel better. It doesn't change the design parameters or how the Chinese employ it.