According to the distance between the front wing and the main wing, the aerodynamic layout of canard can be divided into long-distance coupling canard layout and short-distance coupling canard layout. The eddy current interference mechanism of these two layouts is very different, and the use emphasis of the front wing and its influence on the overall performance are also very different. The canard layout makes use of the favorable interference of the front wing vortex on the main wing flow field, greatly enhances the aerodynamic characteristics of the aircraft at high angle of attack, improves the lift-drag ratio characteristics of the aircraft, and makes the aircraft have superior maneuverability, maneuverability and short takeoff and landing capability. Characteristics of long-range coupled canards: positive trim lift. Both canards and wings provide positive lift for the aircraft, so the trim resistance is small, and a larger lift-drag ratio can be obtained than the conventional layout. Stall prevention. The installation angle of the long-distance coupling canard is usually larger than that of the wing, which makes the canard stall first, which is beneficial to prevent the aircraft from entering the stall wake vortex. The characteristics of the tightly coupled canard are: using the favorable interference generated by the separation vortex of the front wing to sweep the wing, delaying the separation of the wing airflow, delaying the stall of the wing, obtaining greater lift at high angle of attack, reducing the resistance at high angle of attack, and providing the stability of the post-stall flight state of the aircraft.
By combining with the swept wing after aeroelastic cutting, the spanwise pressure distribution of the wing is close to ellipse, thus reducing the flight resistance. With a large swept delta wing, the longitudinal area of the tightly coupled layout is well distributed, the shape of the rear part of the fuselage is smooth and streamlined, and the supersonic resistance is small.
The front wing can also be used as a very effective control surface for direct control technology. Adopting active control technology can also reduce canard load, which is beneficial to reduce trim resistance and improve trim lift. At the same time, the canard is located close to the pilot, which is beneficial to the application of low-altitude maneuverability and gust suppression system.
Generally, the duck layout requires a speed above the speed of sound. Model aircraft should not use canards. If you want to improve the maneuverability of the model airplane, don't consider using canards.