The reason is very simple, because? As long as the thrust is large, bricks can fly into the sky? In the field of aero-engines, Americans have the world's most advanced and powerful aero-engines, and with conventional layout, they can achieve everything Designing performance indicators, there is no need to waste this energy to choose a more complicated canard layout design. With the advantages of advanced aero engines, the take-off weight of US military fighter aircraft can be guaranteed to a minimum, and there is no need to rely on a canard layout to make up for the lack of aircraft performance. The J-20 lacks an excellent engine, so some people believe that the reason why the J-20 has a very excellent aerodynamic design is to make up for the lack of engine thrust.

What is the function of the canard layout? That is, when the aircraft is limited by engine performance and the thrust-to-weight ratio is not high, but the take-off distance at a large elevation angle is only 250-300 meters, the canard layout design plays an indispensable role. Under the same engine conditions, the lift-to-drag ratio of an aircraft using a canard layout will be greater, which can not only shorten the take-off distance of the fighter aircraft, but also increase the maximum take-off weight of the fighter aircraft. Another advantage of the canard layout is that it can generate vortices. It can create vortices on the upper surface of the fighter's main wing and form a low-pressure area on the upper surface of the main wing. This can increase the lift of the main wing and increase the lift-to-drag ratio, lift coefficient, etc. of the fighter. Improving the flight performance of fighter aircraft is the so-called canard layout coupling phenomenon.

However, the shortcomings of the canard wing are also very obvious. The canard wing will produce special vortices, and it is this vortex that affects the stability of the canard layout. For an aircraft with a canard layout, there will be extremely complex interfering airflows between the canards, wings and tail. Therefore, a lot of experiments and calculations are required to arrive at a relatively excellent fuselage design. And even if perfect data is obtained that can ensure perfect wing-to-wing performance, canard aircraft still have problems such as complex flight control systems and poor landing performance. At the beginning, the United States also conducted relatively in-depth research on the canard layout design. In terms of aircraft types, the United States still has the largest number of canard layout aircraft among all countries. However, after verification, various aviation design companies in the United States believe that There is no need to use duck layout.

Due to the canard layout, the aerodynamic center is in front of the center of gravity, which cannot be controlled by traditional mechanical control methods, because this requires a large number of fine adjustments to the rudder surface at all times. This is impossible for humans. Therefore, to design an aircraft with relaxed static stability, it is necessary to use computers to assist driving. The pilot inputs control instructions, and the computer converts them into corresponding signals, which drive the control devices on each rudder surface of the fuselage to achieve smooth and accurate control of the aircraft and achieve active control. To design an aircraft that relaxes the static stability, you must first develop fly-by-wire flight control technology, and the role of the canard is to relax the static stability of the fighter aircraft.

The J-20 is a good solution to fly-by-wire flight control technology, so it adopts a canard aerodynamic layout. The canards of the J-20 are further forward than the main wings of the J-10, which increases the moment arm and enhances the effectiveness, so a smaller canard can achieve a great effect. This layout enables the aircraft to have excellent supersonic speed control rate, good lift characteristics at large elevation angles, and large instantaneous angle of attack and roll rate. Moreover, the J-20 this time uses a fully moving canard, a fully moving tail and movable side strips. The side strips can control droop, and the movable side strips can enhance the vortex lift and control the direction of the vortex. Therefore, when the J-20's engine is not good enough, and you want it to have stronger flight performance, but do not want to reduce the design performance indicators of the fighter, the canard layout is the optimal solution.