J-20 5th Gen Fighter Thread VI

Discussion in 'Air Force' started by siegecrossbow, Sep 4, 2017.

  1. Zool
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    Zool Junior Member

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    Okay, I see where Inst took 'perfect' from, and re-purposed it for the J-20 role discussion. Well, there is nothing perfect in life. Any Engineer and Dr. Song himself will tell you that. Its all a game of trade-offs and design choices based on the required function.
     
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  2. Bltizo
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    Bltizo Moderator
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    J-20 certainly can do strike if adequate weapons are developed for it. J-20's ventral weapons bay may have similar overall volume to F-35's overall volume, however the depth of F-35's two central weapons bay stations allow for significantly larger diameter weapons than what J-20's rectangular cross section weapons bay allows.


    J-20's aerodynamic design was obviously a reflection of multiple competing requirements and certain industrial limitations such as the reality that Chinese turbofans were not sufficiently powerful to allow the aircraft to achieve competitive kinematics using alternative aerodynamic configurations.


    The entire reason this discussion exists is because of early mainstream defense media articles after J-20 appeared suggested the aircraft's design meant it was limited to performing the high speed interceptor or striker roles.

    The push back has been against that narrative. I have never suggested that J-20 is intended to be a dedicated close in low speed dogfighter, and I myself have never suggested J-20 is meant to be a "perfect" air superiority fighter or a perfect "anything".

    I am stating that J-20 is a general air superiority fighter that is capable of conducting other roles such as of interceptor and strike duties, which is a perfectly reasonable way of summarizing the current body of evidence and statements of what roles it is designed to be capable of conducting.

    My position has been pretty clear on that count over the years, but you keep exaggerating my position to portray as it as if it is unreasonable or grandiose.
    I'm not sure if you are deliberately misinterpreting my words or if you are literally unable to understand the words I've typed out, and the difference is one of arguing in bad faith versus lacking comprehension.
     
    #5392 Bltizo, Jul 27, 2019
    Last edited: Jul 27, 2019
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  3. Bltizo
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    Bltizo Moderator
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    There is no such thing as a "perfect" fighter, let's not exaggerate.

    Also, while the airshow performance last year was impressive, we should not use eyeballing of air show performances as a useful indicator of an aircraft's actual performance given the boundaries that may be placed in terms of flight regime.
    Not to mention what one person considers to be "impressive" another person might not consider to be impressive; it becomes subjective and detracts from the ability to pin down an argument.
     
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  4. TerraN_EmpirE
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    TerraN_EmpirE Tyrant King

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    This is an issue that can be addressed by weapons design. F22 has done strike missions with SDB. It’s weapons load was identical to that of J20 with older Aim 120 series missiles. The main limitation right now is that J20 depends on existing missiles and bombs optimized for external carry.
     
  5. Inst
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    Inst Senior Member

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    • Maximum acceleration (g-load) rating was just 2.2 g (21.6 m/s²) with full fuel tanks, with an absolute limit of 4.5 g (44.1 m/s²). One MiG-25 withstood an inadvertent 11.5 g (112.8 m/s²) pull during low-altitude dogfight training, but the resulting deformation damaged the airframe beyond repair.[37]

    From Wiki.

    The MiG-31 is "limited to 5G when traveling at supersonic speeds". Another recent and amusing look at the MiG-31 revealed that the MiG-31 actually has LERX, smaller than that on the J-20 but comparable to AMX Eurofighter.

    [​IMG]

    And I think you're demonstrating my point when it comes to air superiority vs fighter-interceptor. The J-20's WVR capabilities are highly debatable, we know it's at least "not bad" or "good", but it's not the emphasis on the J-20 airframe. What we do know is that the J-20 seems to have excellent max speeds as well as supersonic maneuverability, making it well-suited for the interception role. Pushing it more as a fighter-interceptor (decent WVR, exceptional BVR) fits the evidence more than mapping it to the 4th gen or early 5th gen air superiority role (F-15, Su-27, F-22).

    It is strongly possible that a J-20B with WS-15 will map better to the air superiority role (improved thrust results in better sustained turn rate, TVC radically improves ITR), but it still makes more sense for the J-20C to drop the increased maneuverability by omitting tailfins and ventrals in favor of greater speed, stealth, and range. That's because the air superiority fantasies that want to see a J-20B outdogfight the Su-57 in a guns-only combat isn't a realistic scenario. What you want with the heavyweight is to get firing solutions sent in by IR sensors, get to speed and altitude, fire missiles at superior kinematics, then get out.
     
    #5395 Inst, Jul 27, 2019
    Last edited: Jul 27, 2019
  6. ZeEa5KPul
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    ZeEa5KPul Junior Member
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    Good thing I didn't say the J-20 is a perfect fighter, or even that the J-20 is going to be a perfect fighter. To repeat:

    I stand by that statement. The J-20's stealth performance is held back by the interim engine's nozzles, but all of the other shaping details, planform alignment, gaps between control surfaces and fuselage, panels flush with the body, etc. are first rate. I can't speak to the RAM treatment, but I have no reason to think that there is or will be any enduring weakness in Chinese material and coating technology.

    No other 5th generation fighter can match the 15'd J-20 on all fronts. The F-35 might have slightly better software and sensors, but its kinematics can't measure up. The F-22 might have slightly better stealth because of the rectangular nozzles, but its avionics, sensors, and software are from the PlayStation 1 days and there's only so much retrofitting can do. With the WS-15, nobody is going to be able to bring the total package like the J-20 can.

    I posted that performance because I want to call attention to what I think is a noteworthy aerodynamic phenomenon, namely the second burst of condensation after the plane begins its climb at 4:25. During the first burst, the canards and wings independently generate regions of low pressure without much interaction between them; pretty but nothing to write home about. But something much more interesting happens as the climb continues: a blade of condensation trails the canards and the condensation along the leading edge of the main wing rises up to meet it. For a few frames (this is much clearer if the video is slowed to 0.25), it's as though there's a virtual wing connecting the canards to the main wing. That's not only visually compelling, it's evidence that the canard is coupling to the main wing - yes at that distance, and yes while the canard root is coplanar with the wing.

    Sadly, subjective is what we must be given the dearth of new information. In my defense, I will say that the subjects I brought up are indeed more interesting, more "impressive" by any fair standard than discussions on whether the J-20 can deploy weapons at supersonic speeds.
     
  7. Inst
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    Inst Senior Member

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    @Bltizo

    The problem is that you can't have a dedicated interceptor / striker because one role precludes the other. This is your own use of straw-man, there's definitely "bad" media that points to the J-20 not having the WVR performance we know is baked in, but putting the dedicated term is absurd.

    As for the air superiority role, here's the thing:

    https://en.wikipedia.org/wiki/Air_superiority_fighter

    The definition points to "seizing and holding" air superiority, which is the opposite of shoot and scoot interception which wants to get out, rearm, do maintenance, and change pilots if needed.

    The closer thing to air superiority would be ironically the multi-role Joint Strike Fighter, because its numbers allow it to take attritional damage.

    And as we've seen in this thread, selling it as an air superiority fighter as opposed to a fighter interceptor that can successfully contest enemy 5th gens leads to crap above like "J-20 is a perfect fighter".

    The better push, as I've stated before, is categorizing it as a fighter-interceptor with better dogfighting capabilities than the MiG-31 and explaining how interceptors can successfully defeat "air superiority" aircraft and strike fighters.

    ===

    As far as strike goes, the weapons bay depth is roughly between 550 to 600mm. The F-22 is around 400-450 mm. I forget the bay depth on the F-35, but it's closer to 600-650mm, i.e, not a large difference.

    Let me put it another way. If you were a J-20 designer, would you like the J-20 to be capable of and proficient at strike? And as I've stated before, the threats to the J-20 come not only in the class of flying AEW&C like the E-2D, but also in surface-based and naval-based radar. It makes sense for the J-20 to be proficient at strike instead of deliberately hobbling it to a "not a pound for air to ground" philosophy as you're trying to do with the air superiority role.
     
  8. Bltizo
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    Bltizo Moderator
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    A J-20 with WS-15 will certainly be very closest to the best J-20 it can be barring any future J-20 variants that may have structural modifications.

    I don't think we have anywhere enough knowledge about J-20's comparative stealth shaping and relevant stealth materials in relation to F-35's. Not to mention the likes of F-22 and F-35 will receive upgrades of their own in time not only in terms of avionics and network centric capability, but also in terms of engines where they are likely to receive adaptive cycle engine upgrades in the mid 2020s that will not only enhance their thrust but also greatly enhance their range.
    This is notwithstanding advancements in weaponry that F-22 and F-35 may also enjoy.


    Sure, a J-20 with WS-15s will be much more capable than it is today.
    However, saying J-20 will be the "closest thing there is to a perfect 5th generation fighter" when equipped WS-15s is not something that can be sensibly claimed given we do not know what advancements the other 5th generation fighters of the time may also enjoy.

    It's a position that is immensely difficult to defend, and saying something is "closest thing there is to a perfect XYZ" is not very far from suggesting that "it is perfect".
    It raises questions of what are the "perfect" attributes that should be desired from a 5th generation fighter, how much of those attributes do J-20 with WS-15 achieve compared to other 5th generation fighters that may exist in the future.
    The statement itself implies that there is such a thing to a perfect 5th generation fighter.


    J-20 when equipped with WS-15 will be a much more capable fighter than it is today, which I think everyone can agree on and is a sensible and defensible position. But making confident comparisons as to how good it may be versus other 5th gen fighters of the future isn't very logical IMO.



    Lol, no disagreement there (re: the bolded part).

    But the performance of the aircraft at the airshow should not be part of the discussion as to what J-20's role is -- opposing sides of the argument will simply interpret how "impressive" the performance is based on their own subjective opinions.
    I've been part of these debates before, it's how they tend to end.
     
  9. Inst
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    Inst Senior Member

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    Last thing goes, we can have some idea of the limitations of the J-20.



    The clouds roughly indicate altitude of between 5000ft and 15000ft (1500m to 5000m). At 21 seconds, the J-20 begins a rapid, instantaneous turn of about 90 degrees. This takes about 3-4 seconds to complete, assigning a 22.5-30 degree instantaneous turn rate at low altitude. Compare the F-16's 25 degree sustained turn rate at about 5000 feet.

    [​IMG]
     
  10. ZeEa5KPul
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    ZeEa5KPul Junior Member
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    ... your problems with the English language are almost as severe as your problems with logic and honesty.

    You can define your own private terms to your heart's content, just don't expect other people to use them. Terms like "multi-role", "air superiority", "interceptor" all had meanings before you came along and mauled them. We're not going to use your special meanings, we're going to use those words to mean what they've always meant. The F-35 is not an air superiority fighter, it was not designed to be an air superiority fighter, you're not going to make it an air superiority fighter. You've assaulted logic enough. You've done enough. Have you no sense of decency, sir, at long last? Have you left no sense of decency?

    More of your "facts". Hey, I'll assume you're actually right about this one - I guess the J-20 needs more space so the missiles can slam into it properly as they're being ejected at supersonic speeds.
     
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