J-20 5th Gen Fighter Thread VI

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

  1. Inst
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    Inst Senior Member

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    The problem with supersonic agility for dogfights is that you can't actually use supersonic agility. The faster the aircraft, the greater the g-loads imposed on the aircraft. This means that a Mach 1.5 aircraft pulling 9 Gs is reduced to about 11.5 degrees per second (this is ignoring ITR vs STR) and your opponent is now much more agile than you because of their low speed. You have to remember that a traditional dogfight is an attempt to get a firing solution on your enemy without your enemy getting a firing solution on you. To do the 180 needed to catch the opponent's six, you'd need around 10-15 seconds.
     
  2. latenlazy
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    latenlazy Colonel

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    There’s a trade off. To get that higher turn rate you are also sacrificing airspeed. This means bleeding energy. It’s a contradiction to argue that this is bad when you want to say TVC won’t make much of a difference, but good when you want to argue supersonic maneuverability isn’t useful.
     
  3. jobjed
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    jobjed Captain

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    On the eighth anniversary of the J-20's first flight, let's take a look at the first ever image of the J-20 released on the public domain.

    [​IMG]


    On the 23rd of December 2010, a mysterious aircraft not recognised by even a veteran military enthusiast of fifteen years appeared on the airfield of 132 Factory. It had canards, all-moving tails, ventral fins, and a chiselled nose.
     
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  4. Dfangsaur
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    Dfangsaur Junior Member
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    Feels like a whole life ago. But I was on that forum to witness this post
     
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  5. jobjed
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    jobjed Captain

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    I was visiting China at the time and hadn't visited SDF in a few weeks. When I finally went on SDF again, I must've spent a few hours straight reading through hundreds of posts. I don't think I've ever felt as excited witnessing a PLA development since. The 002, J-15 and 055 were nice and all, but a 5th-generation stealth fighter was and remains in a tier of its own. The whole country was talking about it too, in every dinner I went to, people were talking about the new 隐形战斗机.
     
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  6. latenlazy
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    latenlazy Colonel

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    I was on a family vacation in San Diego when the news broke. Spent the rest of my trip glancing constantly at a screen for updates. Almost impossible to keep up with the flood of information and commentary, and frankly there were some pretty insightful observations made at the time about the design that I didn’t yet have the expertise to really comprehend.
     
  7. Inst
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    Inst Senior Member

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    Once again, learn to read. I didn't say TVC won't make much of a difference, I said specifically that it's a one-off thing. It reinforces WVR as a death zone engagement where aircraft want to avoid because it's too difficult to have enough superiority to avoid attritional combat.

    As far as higher turn rate, you do sacrifice airspeed, but you're assuming it's difficult to reinsert energy via sacrificing altitude or just adding thrust.

    One big mistake I think you're making when you consider supersonic maneuverability as dogfight maneuverability is that you're treating supersonic energy as linear or quadratic. In reality, there's a highly non-linear factor added when you get supersonic energy. The Mach barrier means that there's a spike in energy needed to go supersonic, so when you bleed off the potential energy you bleed it at a greater rate than you would were you to stay supersonic or stay subsonic. The additional energy at Mach 1-Mach 1.5 is less than it may otherwise appear for this reason.

    Lastly, I want to go back to the Song Wencong paper. In the design paper, he talks about supermaneuverability. But strictly speaking, supermaneuverability refers to post-stall maneuvering, which is an instantaneous maneuvering factor, not a sustained maneuvering factor, meaning that it's more useful in terms of BVR or suicide WVR (point, bleed energy, shoot) than it is in strict dogfighting, where sustained maneuverability matters more
     
  8. PiSigma
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    PiSigma "the engineer"

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    15 years is a lifetime in weapons development now it seems. I think it was this that really blew up SDF in membership. Before the j20 SDF was dying a bit with falling posts.
     
  9. kurutoga
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    kurutoga Junior Member
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    It's strange they spotted the all moving tail fin immediately.
     
  10. weig2000
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    weig2000 Junior Member

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    I was traveling to Beijing around the time of 1/11/2011 and was staying in a hotel. I stayed up all night that day and kept refreshing the various defense forums for updates and comments on the first flight of J-20. I had never done anything similar before nor since.

    The first take-off and landing on Liaoning had also cause a great stir in China, probably on a much larger scale. It was broadcast on national TV after all; the mood was more jubilant, the event more symbolic. But the unveiling and the first flight of J-20 was something quite different, and was much more profound. For a while, it was captured only in blurry pictures by wall-climbers.

    Today, and in the intermediate future, China may disclose or unveil any high-tech or advanced weapon platforms, but it's difficult to imagine that I would have the similar excitement and anticipation as I had on that day. I suspect I'm not alone in that feeling.
     
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