J-20 5th Gen Fighter Thread VI

[Brumby]

@Brumby :

If I recall, the traditional claim was that stealth was "shaping, shaping, shaping, and materials", i.e, implying that 75% of stealth effect was the result of shaping. But this quote came roughly from the Nineties and Noughts, when the best unclassified stealth RCS figure was around negative 20-30 dBsm. Hypothetically, say a material can provide an RCS reduction of negative 60 dBsm. This completely upturns the existing formula, i.e, RAM becomes highly dominant in the composition of stealth and you could theoretically make a MiG-21 extremely stealthy by slapping RAM onto it.

AFAIK, the dBsm associated with the F-35/F-22 is in the region of negative 30-40 and often are described as Golf ball/Marble size. At negative 60 dBsm you are talking basically invisibility. I don't see how you can get there even with metamaterials because a plane is not just an empty shell as underneath the skin are a bunch of stuff like engine, cockpit, sensors and avionics.

Currently shaping accounts for 90 % of the RCS profile. There is a big difference between a lab induced result from just using a slab of metamaterial as opposed to the complexities associated with a modern fighter.

 

[Inst]

@Bltizo

The problem is, the mainstream media narrative is substantially correct. It makes sense for the J-20 to be utilized as an interceptor or striker (once the suitable missiles are developed) vs enemy support aircraft. It doesn't make sense for the J-20 to engage force-on-force F-35s because it's likely to go attritional once the merge begins, and the J-20 is never going to outnumber the F-35 unless the F-35 program somehow gets cancelled or the numbers of F-35 are substantially attrited by combat.

The definition of air superiority aircraft is BVR + dogfights. This combo does not make sense for the J-20 because of how stealth changes the game; i.e, you can't exploit your BVR advantage conventionally because you can't detect first due to radar stealth + IR stealth, and you can't exploit any WVR advantage because WVR missiles turn it into an attritional game, one that you don't start with an advantage because stealth means you can't pre-attrition the enemy before you merge.

Interceptors, on the other hand, are more characterized by find, shoot, scoot, run. This is the essential role the J-20 is going to exhibit vs potential foes in the next decade. If a conventional air superiority aircraft or a strike aircraft is akin to a tank, which takes terrain and holds it, the J-20 is more akin to an SPH, wherein the ability to shoot and scoot is crucial to its function. That's why it's wrong to characterize the J-20 as primarily an air superiority fighter, at least in Western jargon.

===

Another way to think of it is if the MiG-31 were upgraded further to exhibit 7-9G (the F-18 iirc is 7G limited) airframe stability. Would the MiG-31 still be an interceptor, given that its primary strength remains its strong radar and its exceptional speed? Or would it all of a sudden become an air superiority fighter?

Or we go back to the Iraqi MiG-25 again. It shot down a F-18, something no other Iraqi Air Force aircraft was able to do. Does that all of a sudden make it an air superiority aircraft?

===

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.

 

[Inst]

AFAIK, the dBsm associated with the F-35/F-22 is in the region of negative 30-40 and often are described as Golf ball/Marble size. At negative 60 dBsm you are talking basically invisibility. I don't see how you can get there even with metamaterials because a plane is not just an empty shell as underneath the skin are a bunch of stuff like engine, cockpit, sensors and avionics.

Currently shaping accounts for 90 % of the RCS profile. There is a big difference between a lab induced result from just using a slab of metamaterial as opposed to the complexities associated with a modern fighter.

The USAF put out a request for -70 dBsm rivets some time ago. This may suggest that the F-35 can achieve -70 dBsm, or that it's slated for a 6th gen aircraft, but I don't think -70 dBsm is impossible. The end result is more likely that radars end up switching to Terahertz to bypass 5th generation stealth.

 

[Equation]

Which means we go back to the high-speed interceptor debate, no? .

No, not at all. Being fast doesn't mean something is a dedicated interceptor rather than an air superiority fighter. Being faster than Mach 2.4 certainly doesn't mean that. F-15 can go mach 2.5; is it an interceptor? No, it just means that J-20's newer aerodynamic design with these up-rated Al-31X can go faster than a Flanker can. That's technological progress, especially when speed is not the main focus.

 

[Hyperwarp]

***

The YF-22 was selected over the YF-23, despite the latter having better speed, sustained turn rates, payloads, and stealth. Why? Because the YF-22 was more agile than the YF-23; i.e, while its stealth gave it a decisive advantage over 4th generation aircraft, the agility meant that if the YF-22 somehow lost its stealth advantage, it could still dogfight its way out of an engagement.

***

The main reason the YF-23 lost out was the confidence of the USAF in Lockheed-Martin. YF-22 and YF-23 both met the ATF requirements including maneuverability. USAF went with the safe option since they had bad experiences with Northrop-Grumman. USAF faced delays and budget overruns in prior projects with Northrop particularly the B-2. YF-23 was the more complicated bird of the 2 including weapons release mechanisms. Even though it wasn't a requirement, YF-22 safely fired AIM-9 and AIM-120, while the YF-23 only had a complicated design for the weapons release mechanism. This build more confidence with the USAF and they ultimately decided to go with the team that could deliver a 5th generation fighter within an acceptable time frame and budget.

 

[Blitzo]

@Bltizo

The problem is, the mainstream media narrative is substantially correct. It makes sense for the J-20 to be utilized as an interceptor or striker (once the suitable missiles are developed) vs enemy support aircraft. It doesn't make sense for the J-20 to engage force-on-force F-35s because it's likely to go attritional once the merge begins, and the J-20 is never going to outnumber the F-35 unless the F-35 program somehow gets cancelled or the numbers of F-35 are substantially attrited by combat.

The definition of air superiority aircraft is BVR + dogfights. This combo does not make sense for the J-20 because of how stealth changes the game; i.e, you can't exploit your BVR advantage conventionally because you can't detect first due to radar stealth + IR stealth, and you can't exploit any WVR advantage because WVR missiles turn it into an attritional game, one that you don't start with an advantage because stealth means you can't pre-attrition the enemy before you merge.

Interceptors, on the other hand, are more characterized by find, shoot, scoot, run. This is the essential role the J-20 is going to exhibit vs potential foes in the next decade. If a conventional air superiority aircraft or a strike aircraft is akin to a tank, which takes terrain and holds it, the J-20 is more akin to an SPH, wherein the ability to shoot and scoot is crucial to its function. That's why it's wrong to characterize the J-20 as primarily an air superiority fighter, at least in Western jargon.

No, the mainstream media narrative is incorrect, because their concepts of J-20's role was derived from initial incorrect perceptions of the aircraft's design.

J-20's design does not limit it to be a dedicated high speed interceptor.

Of course, J-20 can certainly do the high speed interceptor role as one of its many roles if required, and it will be capable of doing strike as well if the requisite weapons are developed to accommodate its weapons bay.
And, of course, the J-20 can also fulfill the role of a general air superiority fighter.


Depending on when a conflict is fought, how many J-20s are available, who a conflict is fought against, the available J-20s could take up any of those different roles or any combination of them

However, J-20 is not a dedicated high speed interceptor or a dedicated high speed striker.

Another way to think of it is if the MiG-31 were upgraded further to exhibit 7-9G (the F-18 iirc is 7G limited) airframe stability. Would the MiG-31 still be an interceptor, given that its primary strength remains its strong radar and its exceptional speed? Or would it all of a sudden become an air superiority fighter?

Or we go back to the Iraqi MiG-25 again. It shot down a F-18, something no other Iraqi Air Force aircraft was able to do. Does that all of a sudden make it an air superiority aircraft?

===

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.

None of what you wrote here contradicts my two points from before:
1: J-20 is not a dedicated high speed interceptor or a dedicated high speed striker, as it was suggested for the early years after it first emerged.
2: J-20's role is best conceived as a general air superiority fighter as its primary role.


Yes, J-20 can absolutely be used as an interceptor.
Yes, of course J-20 would obviously prefer to first engage an enemy in BVR rather than close to WVR.
Yes, of course J-20 would seek to use its superior supersonic agility and stealth to achieve advantageous energy and situational awareness conditions to achieve a kill.

But none of that detracts from my points 1 and 2, because J-20's design is not one which is consistent with that of a dedicated high speed interceptor or a dedicated high speed striker.
J-20's design is most consistent with a general air superiority fighter, and it can of course also be employed as an interceptor and striker.

 

[AndrewS]

@Bltizo

The problem is, the mainstream media narrative is substantially correct. It makes sense for the J-20 to be utilized as an interceptor or striker (once the suitable missiles are developed) vs enemy support aircraft. It doesn't make sense for the J-20 to engage force-on-force F-35s because it's likely to go attritional once the merge begins, and the J-20 is never going to outnumber the F-35 unless the F-35 program somehow gets cancelled or the numbers of F-35 are substantially attrited by combat.

The definition of air superiority aircraft is BVR + dogfights. This combo does not make sense for the J-20 because of how stealth changes the game; i.e, you can't exploit your BVR advantage conventionally because you can't detect first due to radar stealth + IR stealth, and you can't exploit any WVR advantage because WVR missiles turn it into an attritional game, one that you don't start with an advantage because stealth means you can't pre-attrition the enemy before you merge.

Interceptors, on the other hand, are more characterized by find, shoot, scoot, run. This is the essential role the J-20 is going to exhibit vs potential foes in the next decade. If a conventional air superiority aircraft or a strike aircraft is akin to a tank, which takes terrain and holds it, the J-20 is more akin to an SPH, wherein the ability to shoot and scoot is crucial to its function. That's why it's wrong to characterize the J-20 as primarily an air superiority fighter, at least in Western jargon.

===

Another way to think of it is if the MiG-31 were upgraded further to exhibit 7-9G (the F-18 iirc is 7G limited) airframe stability. Would the MiG-31 still be an interceptor, given that its primary strength remains its strong radar and its exceptional speed? Or would it all of a sudden become an air superiority fighter?

Or we go back to the Iraqi MiG-25 again. It shot down a F-18, something no other Iraqi Air Force aircraft was able to do. Does that all of a sudden make it an air superiority aircraft?

===

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.

It's an interesting point you make about stealth fighter vs stealth fighter combat.

And how this changes the optimal tactical strategy (for a stealth fighter) from "BVR launch + WVR dogfighting" to "shoot and scoot" against high-value targets.

But it's high value targets which have UHF frequency radars which can detect opposing stealth fighters, possibly with a weapons grade track that it can pass to a shooter.

Anyway, it means even more effort should be made on destroying opposing stealth fighters on the ground before they take off.
But when a counter-air mission is required, it argues for a smaller stealth fighter (for attritional WVR combat) which is cheaper and which also has a smaller IR signature.

 

[Inst]

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.

As for the J-20 in general, here's another simple explanation about the definition of an interceptor. This is from a Western magazine covering the Eurofighter:

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The first Eurofighters would begin as interceptors, but over time mature into multi-role combat jets, flown by the air forces of the four partners—and, their principals hoped, of other countries as well.
Read more at

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Essentially, beginning as an interceptor does not mean that an aircraft cannot transform as the airframe and subsystems change over the development life. I've made a big deal about how the AMK with LERX and strakes have substantially improved the Eurofighter's performance. Likewise, the Eurofighter Typhoon, as subsystems developed, became capable and proficient in ground attack as well as a more capable dogfighter.

The F-16 is another strong example. The earliest F-16s were analogues to the MiG-29, intending the F-16 to be a short-range point defense fighter. The F-16 eventually evolved into a lightweight strike fighter that sacrificed its wing loading for better strike performance and range.

In the J-20's case, the range from the WS-15s at a predicted 180 kN and the WS-10 / AL-31FN at 130-140kN roughly maps to a 26% reduction in thrust. Crippling the thrust of such a fighter is going to severely degrade maneuverability; AoA / Drag equations imply something around a 1:1 ratio (not exact, depends on aircraft) in terms of drag increase on alpha. This implies that the J-20 has lost about 26% sustained turn rate. The initial J-20s, provided that they're powered with WS-10 / AL-31FN can rightly be described as interceptors for this reason.

===

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.

@Hyperwarp :

The J-20 is likely to be able to hit at least Mach 2.7 with WS-15s if it can hit Mach 2.5 now. There is literally no way for the J-20 to defeat the F-35 on a strategic level if it does not leverage its speed advantage over the F-35.

 

[Tam]

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.

As for the J-20 in general, here's another simple explanation about the definition of an interceptor. This is from a Western magazine covering the Eurofighter:

Please, Log in or Register to view URLs content!

Essentially, beginning as an interceptor does not mean that an aircraft cannot transform as the airframe and subsystems change over the development life. I've made a big deal about how the AMK with LERX and strakes have substantially improved the Eurofighter's performance. Likewise, the Eurofighter Typhoon, as subsystems developed, became capable and proficient in ground attack as well as a more capable dogfighter.

The F-16 is another strong example. The earliest F-16s were analogues to the MiG-29, intending the F-16 to be a short-range point defense fighter. The F-16 eventually evolved into a lightweight strike fighter that sacrificed its wing loading for better strike performance and range.

In the J-20's case, the range from the WS-15s at a predicted 180 kN and the WS-10 / AL-31FN at 130-140kN roughly maps to a 26% reduction in thrust. Crippling the thrust of such a fighter is going to severely degrade maneuverability; AoA / Drag equations imply something around a 1:1 ratio (not exact, depends on aircraft) in terms of drag increase on alpha. This implies that the J-20 has lost about 26% sustained turn rate. The initial J-20s, provided that they're powered with WS-10 / AL-31FN can rightly be described as interceptors for this reason.

===

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.

@Hyperwarp :

The J-20 is likely to be able to hit at least Mach 2.7 with WS-15s if it can hit Mach 2.5 now. There is literally no way for the J-20 to defeat the F-35 on a strategic level if it does not leverage its speed advantage over the F-35.

I actually see a problem of yours because a fighter intended to be designed primarily as high speed interceptor should not have the LERX and the strakes that the J-20 is built with originally. All those things only serve to add drag. It would have clean non drag features first, and would later have the LERX and strakes added on.

Let's go back to the Eurofighter argument. Except that this time, the Eurofighter came off from the very start, having the LERX and strakes.

As for the engine power, you cannot use the argument of currently reduced engine power --- which was only intended as a short term gap, and not the primary spec for the fighter, not its definitive spec --- as the argument for its primary and definitive purpose of design, that it doesn't intend to be a highly maneuverable one. It may not be as maneuverable currently as the designers intended but that state does not change the original intention. It only means its still steps away from reaching its desired state.

 

[Pmichael]

I think some people are overthinking the main objectives of the J-20.
Despite the delta-canard aerodynamic design which remember on European delta fightes or the cancelled MiG 1.44, the main mission types should be the same as the Su-27 - a fast and highly maneuverable deep penetrator.

Also the TKF-90 concept which later evolved into the Eurofighter was at no point ever an interceptor. It was strictly designed around the E-M theory concept which means the Eurofighter's capabilities to turn while maintaining a high level of evergy in combination with a high thrust to weight ratio is still second to none.