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The wing of an airplane is a complex work of art that combines aerodynamics, material science and structural mechanics. In order to meet different flight tasks (such as long-distance cruise, short-distance take-off and landing or high-speed interception), the design of wings is also very different. We can get a deeper understanding from the following four dimensions:

Plane shape of wing: brand of speed

This is the most intuitive feature to distinguish the "personality" of an airplane. According to China's data, it can be divided into three categories: straight wing, swept wing and delta wing.

Swept wing: the current mainstream. The leading and trailing edges of the wing extend backward, which is mainly used to delay the generation of shock waves and reduce the resistance during high-speed flight. Most civil airliners (such as Boeing 787[citation:6]) and high-performance fighters (such as F-14 Tomcat with variable swept wings [citation:5]) adopt this form.
Straight wing: the front and rear edges of the wing are basically parallel and perpendicular to the fuselage. It is characterized by good low-speed performance and high lift, but the resistance increases sharply at high speed. Mainly used in low-speed small aircraft, light sports machines or special-purpose aircraft with low speed requirements (such as the British "Defender" early warning aircraft).
Delta wing: the plane of the wing is triangular, and the root-tip ratio is large. It is characterized by high structural strength and low flight resistance at high speed, but poor performance at low speed. Common in supersonic fighters (such as China's J -20) and Concorde supersonic passenger aircraft.

In addition to the plane shape, there is also a key parameter called aspect ratio (the ratio of wingspan to chord length). A transport plane like Yun -20, which needs long voyage and heavy load, has a long and narrow wing (large aspect ratio), just like a weightlifter's arm, which can generate lift efficiently. Fighters like the J -20, which pursue extreme speed, have short and wide wings (small aspect ratio), like the legs of sprinters, which can minimize resistance.

Structural form of wing: internal skeleton

From the internal structure, the structural form of the wing has also undergone many evolutions, which is directly related to the strength and weight of the wing.

Frame wing: Early aircraft (such as Wright brothers' aircraft) used wooden skeleton gabriel skin, which was only responsible for maintaining the shape and did not participate in the stress.
Beam and monolithic wings: metal structures used by most modern aircraft. With powerful wing beam and metal skin, it can not only bear huge bending moment, but also provide sufficient torsional stiffness.
Integral panel wing: this is the symbol of advanced aircraft at present. The wing panel is made of a whole piece of material (usually composite material), which greatly reduces the number of parts and connecting holes, has lighter weight, higher strength and smoother surface, and greatly improves the flight performance.

Material technology of wings: the revolution from metal to composite materials

Material is the cornerstone of wing performance.

Composite wing: represented by Boeing 787, it is the world's first passenger plane with a large number of composite materials in its main structure, with the amount of composite materials as high as 50%, and the wing is mainly made of carbon fiber/epoxy resin. This brings excellent weight loss effect, fatigue resistance and corrosion resistance.

Hybrid material scheme: The latest Boeing 777X adopts the route of "aluminum-lithium alloy fuselage+composite wing". The reason for this choice is that the 777X continues the metal fuselage section of the old model, and can follow the mature production line, greatly reducing the cost. The 71.8-meter-long wing can only be made longer and thinner by carbon fiber composite materials, so as to achieve the best aerodynamic efficiency. Therefore, a 3.5-meter-long foldable wing tip is innovatively designed to solve the airport adaptation problem of the ultra-long wing.

Movable surface of wing: multifunctional "little wings"

There are also many moving parts on the wing surface, which are like the "muscles" of an airplane and control every detail of flight.
Aileron: located outside the trailing edge of the wing, it deflects left and right differentially to control the rolling of the aircraft (that is, the rotation around the longitudinal axis of the fuselage).
Flap: located at the inner side of the trailing edge of the wing (trailing edge flap) or the leading edge (leading edge flap), it is released during take-off/landing, which increases the camber and area of the wing, thus greatly increasing the lift and helping the aircraft take off and land.
Leading-edge slat: When it is opened, it forms a gap with the leading edge of the wing, guiding the airflow from the lower wing surface to the upper wing surface, delaying the airflow separation and preventing the aircraft from stalling at high angle of attack.
Spoiler: located on the upper surface of the wing, it can destroy the lift and increase the resistance when opened. In the air, aileron can be assisted for rolling control; When landing, they are all open, acting as speed brake to stop the plane as soon as possible.