Although it is an indisputable fact that the J-20 surpasses the F22 in super patrol and super maneuver by relying on the unique "lifting body side duck layout" in the world, such a complicated aerodynamic shape will inevitably bring greater challenges to stealth design.
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For example, take the principle of parallelism that the fourth-generation aircraft must abide by: all edges of the aircraft surface should be parallel to the main wing as much as possible, so as to optimize the reflection angle and combine the incident radar waves into several specific safety directions, which deviates from the main threat direction.
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Comparing the aerodynamic shapes of J-20 and F22: Because the front canard is not completely parallel to the main wing surface, the radar reflection of J-20 is 12 wave system, that is, the incident radar wave is reflected to the main direction of 12, while F22 is 8 wave system. From the most basic principle of stealth design, the fewer reflected wave systems, the lower the probability of being discovered. The B2 stealth bomber with flying wing layout is the best in this respect: the front and rear edges of the fuselage are parallel, and all kinds of joints are parallel after serrated. There are only two directions on the edge of the whole fuselage, and even there is no need to hang the tail at all. The whole fuselage is made into a flat body to obtain the ultimate stealth effect.
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The canard of the J-20 will definitely increase the radar launch area during the deflection process. Even if this influence can be reduced by controlling the deflection angle or using absorbing materials, from the basic principle that the smoother the stealth design, the better: canards will definitely destroy stealth, which can't be run away anyway. According to American estimation, the frontal RCS of J-20 is one order of magnitude higher than that of F22. The published RCS data of F22 RCS 0.000 1 m2, and J-20 may be 0.00 1.
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But this gap is not a problem of 0 and 1 for stealth fighters, but a problem of 1 and 1.3, or even a problem of 1 and 1.2. The simplest truth: With the RCS level of J-20, the radar of F22 can't lock effectively beyond the over-the-horizon air combat distance of 100 kilometers. Only by using radar for a long time and searching accurately can we find it in a short distance, but this is equivalent to turning on a flashlight at night and blowing itself up. Because stealth fighters have an electromagnetic stealth besides radar stealth and infrared stealth: try to avoid turning on the radar for a long time and being discovered by the other side's electronic reconnaissance means. After all, the only defeat of F22 was that it was cheated by EA- 18G in a martial way.
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For stealth fighter: you can find it by radar. What does this mean? The former Chief of Staff of the Indian Air Force once famously said: Su 30MKI's radar can detect the J-20 several kilometers away. Of course, I can also detect this distance. Therefore, the fight between the J-20 and the F22 is not a one-on-one game that many military fans take for granted, but more depends on the combat system behind it.
After all, J-20 was originally designed for national air defense, relying more on ground-based long-range early warning radar and airborne early warning aircraft to offset the stealth advantage of F22, and then taking advantage of its super patrol and super maneuverability in long-range interception.
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The design orientation of F22 is frontline offensive operations, that is, using stealth advantage to attack a big country with a vast territory and lacking advanced air defense means, so stealth ranks first in performance indicators. Therefore, it is of no practical significance to compare the performance of two fourth-generation aircraft with different positioning in an attempt to distinguish their combat power. Talking about the performance of weapons without fighting is hooliganism.
Although the technical and tactical indicators of the two fighters are different because of their different operational positioning, this does not prevent us from giving full play to our late-comer advantage and surpassing our old comrades in single-point technology. The most noteworthy thing in this respect is the DSI inlet of the J-20, which is "supersonic inlet without boundary layer partition" in Chinese.
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First of all, what is the boundary layer? When the fighter plane flies at high speed, the air near the body surface rubs against the skin, and the flow speed decreases due to the viscosity of the air. This air layer with variable shunt field is called boundary layer. If these low-speed airflow with unstable velocity and direction are mixed with high-speed airflow and sucked into the intake port, the intake efficiency will be affected, and even the engine will stall. Therefore, in order to eliminate the influence of boundary layer, the traditional solution is to leave a gap between the fuselage with a partition. In addition, the inlet is not a straight and simple channel, and there are various complicated baffles and exhaust ports to remove the low-speed airflow in different flight conditions. However, this design is obviously very unfavorable to the fourth generation aircraft pursuing high maneuverability and high stealth: the cavity formed by F22 boundary layer partition will not only greatly increase the resistance during supersonic flight, but also be very unfavorable to frontal stealth.
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The DSI inlet of the J-20 is a three-dimensional bulge, which will be cut along the turbulent layer of the fuselage when flying at high speed. It not only saves the complicated suction and exhaust system, greatly reduces the structural weight, but also improves the maneuverability of the fighter in transonic flight, which is more conducive to stealth.
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The principle of DSI inlet looks simple, but the size, shape and position of the protrusion should consider the inlet efficiency under all speed ranges and elevation changes, which embodies the highest level of computational fluid dynamics and requires a large number of high-speed wind tunnels and extremely high machining accuracy. Traditional metal materials can't meet the requirements of such high precision machining, so composite materials can only be used. At this point, we can see that the color of the yellow skin J-20 inlet bulge is obviously different from other parts.
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It is precisely because of the extremely high design and processing difficulty of DSI inlet that only the F-35 fighter is in use in western countries. Although Loma Company first started to study related technologies on F- 16, we immediately developed our own corner overtaking after using Krypton eye skills. Xiaolong became the first fighter in service in the world, using DSI inlet. Since then, it has been out of control, not only the mid-range 歼 10B and 歼10C; ; The high-end J-20, FC-3 1, and even the mountain eagle trainer modified by J-7 all use DSI inlet. There are those with abdominal air intake, those with air intake on both sides, such as Cheng Fei, Guifei and Shenfei. This top technology is almost being cabbaged.
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However, if we still cross the river by touching the eagle sauce at the DSI air inlet, the design of the J-20 magazine is the result of completely independent innovation. In order to achieve complete stealth, all weapons and ammunition need to be built-in. Like F22, the J-20 adopts the arrangement of main magazine and side magazine on the belly. The main magazine is used to mount medium-range air-to-air bombs, and one short-range combat bomb is mounted on each side magazine.
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F22' s side magazine adopts up-and-down door. Before launching, the front section of the slide rail is opened and lifted to expose the guide head of the rattlesnake missile. The hatch opened at this time not only affects the flying quality like a giant parachute, but also seriously damages the stealth of the body surface.
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The side magazine of the J-20 solved the F22 problem perfectly with a more creative rotating guide frame. Only one side of the magazine opens up. As long as the pilot enters the combat state, he can open the side magazine, and the rotating mechanism will turn out the guide rail hook and push it out, and then close the hatch.
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This can not only ensure that stealth and maneuverability are not affected, but also the missile guidance head has a broader search field of vision. Launch immediately after finding the target, and then open the hatch again to recover the pylon.
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Lifting body duck layout, DSI air intake, rotary guiding launcher and J-20 all show the unique innovative wisdom of China aviation people. From the unreachable of that year, to the hope of the future, and then to the present hand in hand. From the beginning of the J-20, it indicates that China has gradually acquired the ability to design and develop fighter planes that challenge the United States, the world's first aviation power.
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However, the current level of the J-20 is far from the final form: two-seat version, thrust vector version, sniper bombing version. What room for improvement and development is there for the future J-20? Let's wait and see.