J-20 5th Gen Fighter Thread VI

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siegecrossbow

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I mean the J-20 is closer to what you'd get if you crossed a MiG-31 and an F-22. The idea that it's supermaneuverable is doubtful from the videos we've seen, at least with present engines and non-TVC nozzles, but it has more than the MiG-31's level of agility.

The mistake Chinese partisans make is that they suggest the J-20 is a helicopter when it comes to maneuverability. The mistake Western observers tend to make is that it's specced for the interceptor role and the interceptor role alone.

I don't think most of the guys at this forum claim that the J-20 is a "helicopter" in the same vein as the Su-35. Most of us are just against the notion that it is worse than conventional 4th generation fighters like the J-10 or Su-27 because of its length, size, weight, etc. Our viewpoint has been vindicated by the Xinhua interview with Li Gang (J-20's first test pilot) quoted in Blitzo's article that stated the J-20 has similar agility as the J-10.

Gonna plug my translation of the entire Xinhua interview here.

https://www.sinodefenceforum.com/chinese-military-articles-translation-thread.t5679/page-12
 

ougoah

Brigadier
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Sweep angle and assumed mission profiles would indicate that J-20 is indeed more optimised for high speeds, giving greater credence to the interceptor role accusations. At least performing better at high speed and high altitudes. J-20 aims to replicate similar capabilities as F-22 does for USAF. PLAAF wants something to scoot in and out of contested airspaces with quick 180s, all while being able to handle any WVR using HOBS PL-10s and the situational awareness advantages offered by DAS like systems and far superior data management compared to J-11 and J-10, and almost certainly also Su-35. The possible absence of a gun (for the moment) indicates that WVR is not how J-20 will ideally be used.

The interceptor accusation has had quite an unfair emotional reaction from most of us here because it implies the J-20 is incapable of handling air superiority and merge fights, only focusing on knocking out key targets at ranges well beyond Chinese airspaces. This fighter was not designed in the 70s. It is possible to combine roles these days as long as fuel capacity allows for them. From what we've been allowed to see of J-20's performance so far, it seems like it is at least as agile as any 4th gen of this weight and size class. Maneuverability will depend on FCS and engines, with TVC opening up additional layers of performance. All pilot testimonies suggest the J-20 is as good as any 4th gen in subsonic performance, but it dominates in super-sonic speeds. Its sweep angle from those aerial shots is far more dramatic than Flankers and J-10s. Like the Mirage series, this sharp sweep delta wing design optimised for high altitudes and speeds, may be more prone to bleed energy. Overcoming this potential issue would require more thrust and more fuel. Both of which it either already has in AL-31/WS-10 or will get upgrades in. Honestly I don't think it is underpowered at all. It's claimed to be lighter than flankers and even if that weren't true, it should still get at least a what would effectively be over 1 T:W given the inherent lower drag and higher lift. Also J-20s are currently operating with the highest thrust variants of modernised AL-31s/WS-10s. This is unless its empty weight is far more excessive than "official" claims. AL-31 and WS-10 are still VERY powerful engines despite the existence of F119 and F135.
 
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Blitzo

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Sweep angle and assumed mission profiles would indicate that J-20 is indeed more optimised for high speeds, giving greater credence to the interceptor role accusations. At least performing better at high speed and high altitudes. J-20 aims to replicate similar capabilities as F-22 does for USAF. PLAAF wants something to scoot in and out of contested airspaces with quick 180s, all while being able to handle any WVR using HOBS PL-10s and the situational awareness advantages offered by DAS like systems and far superior data management compared to J-11 and J-10, and almost certainly also Su-35. The possible absence of a gun (for the moment) indicates that WVR is not how J-20 will ideally be used.

The interceptor accusation has had quite an unfair emotional reaction from most of us here because it implies the J-20 is incapable of handling air superiority and merge fights, only focusing on knocking out key targets at ranges well beyond Chinese airspaces. This fighter was not designed in the 70s. It is possible to combine roles these days as long as fuel capacity allows for them. From what we've been allowed to see of J-20's performance so far, it seems like it is at least as agile as any 4th gen of this weight and size class. Maneuverability will depend on FCS and engines, with TVC opening up additional layers of performance. All pilot testimonies suggest the J-20 is as good as any 4th gen in subsonic performance, but it dominates in super-sonic speeds. Its sweep angle from those aerial shots is far more dramatic than Flankers and J-10s.

There are two problems of the interceptor argument which are two sides of the same coin, which I didn't really have the word count to go into depth in, but which you touch on.

The first, is the assertion that the interceptor argument is often described in a manner that suggests it is only meant to be targeting opposing high value, vulnerable force multipliers like tankers and AEW&C. In almost every instance of this argument, it is either directly stated or indirectly implied that J-20 lacks the capability or the intent to directly engage opposing fighters.

The second, is the question of when does an "interceptor" become an "air superiority fighter" and when an "air superiority fighter" become an "interceptor. Is it a continuum or is it a box. Was the YF-23 better suited as an interceptor but less well suited than the YF-22 as an air superiority fighter, or is that only dependent on the doctrine and the sensors and the numbers of each respective airframe's potential future operating environment.



The most fundamental reason why the interceptor argument has rubbed people the wrong way since the beginning, is because it was almost always described by proponents to suggest J-20 was not intended to combat opposing fighter aircraft as a primary -- if not the primary -- mission. Instead, it was asserted that when met with opposing fighter aircraft, the J-20 would always be forced to retreat as a particular nature of its inherent design.

The agility debate comes into play once we start to consider what present day and short to medium term requirements for the air superiority mission are, and once we start looking at the backlog of relevant semi-official documents, official testimonies, J-20 aerial displays, and use of common sense.




I would also add that I do not think the statements about J-20 having exceptional supersonic agility adds credit to the idea that it is meant to be a dedicated interceptor. Rather, I would say that having exceptional supersonic agility suggests the aircraft was intended to be highly maneuverable in the supersonic regime (or at least far more so than previous generations of PLA fighters) that would be indicative of an intended supercruise capability.
Of course, I'm sure I don't need to explain the benefits of supercruise, energy management and agility for all manner of engagements whether it is WVR or BVR.
 

TerraN_EmpirE

Tyrant King
The absence of a gun indicates that WVR is not how J-20 will ideally be used.
Although I agree with most of that assessment. I feel this part here may have more to due with technical issues. A gun system in a stealthy fighter is more complicated then a conventional fourth gen.

Already on fourth gens. The system must be light enough not to interfere with the fighters balance. And cannot eject casings into the air stream.
For the former restrictions of size of shell and ammo magazine are strict.
For the latter link less is the rule and the gun cycles spent casings back into the magazine.
The gun must be downwind of the intakes. The "gun smoke" of a gun is a mix of various materials but in that mix is unspent propellent propeller and carbon which can damage the blades of a turbine or "choke" the engine by interrupting the flow of oxygen.

Now on to this we add that the muzzle of the gun must be covered with a door that is reliable in opening even in high G turn.
If the door fails to open and the gun goes bang the pilots bad day has just begun.
Spent propellant becomes more of a issue as even if clear of the intakes the spent propellent is going to soot from firing can effect the stealth coatings and RCS reduction.
If firing the gun paints the jet in a radar reflexive soot its not stealthy.

The gun should also weigh less as the entire system has uploaded weight compared to a fourth gen.

Basically I figure the designers are working on a autocannon for J20 but probably specifically tailored for it and there Fifth gens. Will probably be added to production J20.
 

latenlazy

Brigadier
Like the Mirage series, this sharp sweep delta wing design optimised for high altitudes and speeds, may be more prone to bleed energy. Overcoming this potential issue would require more thrust and more fuel.
For pure deltas yes, but *not* for canard deltas, or deltas with other advanced vortex generation/body lift designs. The whole point of employing vortex generators is to overcome the energy bleed issue by maintaining stronger attached flows to the wing during maneuvers. This is why the Eurofighter, despite having a very sharp wing sweep, is not known to be a fighter that bleeds a lot of energy during maneuvers, and why a lot 5.5 and 6th gen design proposals have been delta wings.
 
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Blitzo

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I trust you mean 4.5, because no one has a 5.5 yet. Would have to have an idea of what a 6th actually is solidified to Gage what is half way there.

I think he means 5.5 -- some proposals like the european FCAS/NGF, the UK Tempest, and to an extent the Japanese F-3 feature some meaningful advances beyond what the first wave of 5th gen fighters introduced. Those advances mostly revolve around manned/unmanned integration and further networking advances beyond what 5th gen fighters currently field.

They are slated to enter service in the mid 2030s.


Of course, whether they will earn the "5.5 generation" moniker will depend on what they actually end up offering and what eventual 6th gen looks like.
 

latenlazy

Brigadier
I trust you mean 4.5, because no one has a 5.5 yet. Would have to have an idea of what a 6th actually is solidified to Gage what is half way there.
Eh, debates abound whether the recent French-German and British fighter projects announced qualify as 6th gen or 5.5 gen, but the point I’m making is the same.

Edit: I see that I have typoed in the first comment you were replying to. It should have been 5.5 and 6th gen designs, not 5.5 and 5th.
 
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