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主题:【原创】再谈四代 -- 晨枫

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    • 家园 Posting on behalf of

      my suite mate.

      To 晨枫:

      First off, I'd like to thank you for taking the time to answer my questions. I think the Chengdu J-20 is an interesting study both in its capabilities and its potential competitiveness on the defense systems market.

      My friend has told me that you are a Chinese engineer living in Canada but that's all I know, so I was wondering if you could also tell me a little bit about yourself and your education.

      What interests me most about the J-20 is how it compares with the Lockheed F-22 considering the shape of the plane itself is so similar. I'm sure that since the F-22 is older that the software is fairly different from the J-20 but do you happen to know how the J-20's flight length and weapon systems compare with the F-22 or even the F-35?

      Also, I've seen head-on pictures of the J-20 with one of the vertical stabilizers on the tail turned almost 90 degrees, which my friend claims contributes to maneuverability.

      However, if the J-20 were to get in a dogfight and turn the stabilizer that far over, wouldn't the speed of the fighter rip the stabilizer off? Do you know what purpose a fully movable stabilizer would serve besides compactness on the ground?

      Thanks again for your time!

      • 家园 你的室友对我们的回答怎么说?
      • 家园 对不起,昨天回来晚了,只好今天回复

        You are welcome. Chengdu J-20 is more than interesting. It is a game changer. That is a big topic and let's save it for later.

        How J-20 compares to F-22 is a question that is on many people's mind. Unfortunately, at this point, other than a few pictures, there has been no technical data released, including geometry (wing span, length, height, wing area, etc.), performance (range, speed, turning rate, etc.), weight/load (empty weight, loaded take off weight, max take off weight, internal weapons load, underwing carrying capability, internal fuel capacity, etc.) and electronics (AESA, IRST, sensor fusion, EW, etc.). All guesses will be just that, guesses. Popularly it is believed that its performance is comparable to F-22 overall but I have no way of confirming or disputing that. However, I am reasonably confident that it should outperform F-35, which is actually inferior to the teen series in terms of speed, agility, etc. because of its dismal thrust to weight ratio and wing load. Believe it or not, it is not that hard to outfly an F-35.

        J-20 uses outward canted and all moving twin tails. The purpose of that large amount of deflection is not to enhance maneuverability. However, with that high degree of deflection, it doubles as air brake, together with coordinated moves of flaps and canards, to make sure it slows down level and straight.

        Besides that, all moving tails can be more compact, using active control instead of passive stabilization like wind cock. If you look at F-22't tails, you can easily tell the fixed part from the moving rudder at the back edge. The fixed part is that wind cock, resulting from the classic laterally stable design. J-20's smaller V tail is laterally "reduced stability" design, saving on weight and RCS, but more demanding on flight control.

        You mentioned that J-20 is similar to F-22. I imagine you refer to the side profile. However, aerodynamics is more determined by "birds eye view" than side profile. J-20 and F-22 are decidedly different from that angle. Aerodynamically, these two are as different as Corvette and Porsche 911, or F-16 and Eurofighter Typhoon.

        Hope I answered your questions and nice talking to you.

      • 家园 这哥们真一根筋

        However, if the J-20 were to get in a dogfight and turn the stabilizer that far over, wouldn't the speed of the fighter rip the stabilizer off? Do you know what purpose a fully movable stabilizer would serve besides compactness on the ground?

        J20的垂尾能转那么大的角度,我估计是,J20在空速极慢的情况下依然可以进行各种姿态调整。

        J20是数控线传,垂尾什么情况下转多大角度都是软件控制的,高速飞行时自然转不到那么大的角度。所以我说这家伙一根筋,还以为现代飞机的操纵面跟莱特兄弟时代那样,都是铁丝拽的,空中一不小心拽过头,结果垂尾给掰掉了。

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