Fighter wing

The main function of fighter wings is to generate lift to support aircraft flying in the air. It also plays a certain role in stability and maneuverability. According to the plane shape of wings, there are rectangular wings, trapezoidal wings, delta wings, double delta wings, arrow wings, strake wings and so on.

According to the front and rear position and function of the wing in the fuselage, it can be divided into main wing, tail wing (horizontal tail wing and vertical tail wing or oblique tail wing) and front wing (also called canard wing). According to the angle between the main wing and the fuselage, there are forward swept wing, backward swept wing and variable backward swept wing.

Modern aircraft are generally monoplane, but biplane (wings overlap up and down), triplane and multi-wing aircraft have also been popular in history. According to the connection position between the wing and fuselage of monoplane, it can be divided into lower monoplane, middle monoplane, upper monoplane and umbrella-type upper monoplane (that is, the wing is above the fuselage, and the wing and fuselage are connected by a set of struts).

Let's learn about several kinds of wings commonly used in fighter planes from different angles.

tail

The tail wing is a device installed at the rear of the aircraft for stability and control. Tail is generally divided into vertical tail and horizontal tail. The vertical tail consists of a fixed vertical stabilizer and a movable rudder, which mainly plays the role of direction stability and direction control in the aircraft. Vertical tail is short for vertical tail or vertical tail. According to the number of vertical tails, aircraft can be divided into single vertical tail, double vertical tail, three vertical tail and four vertical tail aircraft.

At present, some fighters with double vertical tails adopt V-shaped layout, such as the fourth-generation fighter F-22 in the United States. The horizontal tail consists of a fixed horizontal stabilizer and a movable elevator, which plays the role of longitudinal stability and pitch control in the aircraft. The horizontal tail can be called flat tail for short. In order to improve the efficiency of pitch control, some aircraft adopt full-motion horizontal tail, that is, the horizontal tail has no horizontal stabilizer and the whole wing surface can deflect.

There is a special V-shaped tail, which can not only play the role of vertical tail, but also play the role of horizontal tail. The horizontal tail is generally located behind the main wing. But some planes put the "flat tail" in front of the wing. This kind of plane is called canard. At this time, the front "horizontal tail" is called "front wing" or "duck wing", and the plane without horizontal tail (or even vertical tail) is called tailless plane. The pitch control, direction control and roll control of this aircraft are all controlled by the movable wing surface at the trailing edge of the wing or the thrust vector nozzle of the engine.

rumour

Duck layout: There are two smaller triangular wings (swept back) on both sides of the cockpit, followed by a larger triangular wing. For example, China's J- 10, J-20 and Europe's EF2000 all adopt duck layout, which is very suitable for supersonic air combat.

As early as before World War II, the former Soviet Union had found that if the horizontal tail was moved to both sides of the nose in front of the main wing, the same control efficiency could be achieved with a smaller wing surface, and the front wing and the wing could generate lift at the same time, unlike the horizontal tail, which would generate negative lift in most cases.

The early duck layout flew like a duck, hence the name "duck layout". The front wing of a canard plane is called "canard". There are two kinds of canards for fighter planes, one is uncontrollable, and its function is to strengthen the leading edge vortex of the wing at high angle of attack, improve the performance of the aircraft at high angle of attack, and is also conducive to the short-moment take-off and landing of the aircraft.

At present, there are J- 10 in China, EF-2000 in Europe, Gust in France and JAS-39 in Sweden. The canards of these aircraft are not only used to generate eddy currents, but also to improve the problem of sudden drop of stability in transonic process, and at the same time to reduce the trim resistance, which is beneficial to supersonic air combat. When landing, the canard can also deflect a larger negative angle, playing the role of speed brake.

swept-back wing

A wing whose section moves backward along the span is called a rear wing. The shape of this wing is characterized by leading edge and trailing edge swept back. The wing sweep angle is expressed by the sweep angle.

Compared with the straight wing, the aerodynamic characteristics of the swept wing can increase the critical Mach number of the wing and reduce the drag when flying at supersonic speed. In flight, when the velocity of the airflow perpendicular to the leading edge of the wing approaches the speed of sound, the airflow in some areas on the upper surface of the wing will be affected by the convex wing surface, and its velocity will exceed the speed of sound, resulting in local shock waves, which will greatly increase the flight resistance.

Because the swept wing can make the velocity component perpendicular to the leading edge of the wing lower than the flight speed, the shock wave will only appear at a higher flight speed than the straight wing (that is, the critical Mach number will increase), thus delaying the generation of the shock wave on the wing surface. Even if there is a shock wave, it will help to weaken the intensity of the shock wave and reduce the flight resistance. The disadvantages of sweep angle are poor torsional stiffness, low slope of lift line, easy separation of airflow from wing tip, and large induced drag during subsonic flight.

delta wing

Delta wing of Phantom 2000

A triangular wing is called a delta wing. Similarly, there are double delta wings and tangent delta wings. At present, delta wings with slightly cut corners are commonly used. Delta-wing aircraft appeared in the 1950s, and the representative models are American F- 102, former Soviet MIG -2 1, French Mirage III, etc.

Delta wing with large sweep angle has the advantages of small supersonic drag, small change of focus with m number and good structural stiffness, which is suitable for supersonic flight and maneuvering flight. The disadvantage of delta wing is that in subsonic flight, the lift line slope of the wing is low, the induced resistance is large, and the lift resistance is small, which affects the range and take-off and landing performance of the aircraft.

Variable swept wing

Wings whose sweep angle can be changed in flight are called variable sweep angle wings. In aircraft design, there is an insurmountable contradiction: in order to improve the flight M number, we must choose wings with large sweep angle and small aspect ratio to reduce the impact resistance of the aircraft, but such wings have small lift, large induced drag and low subsonic efficiency. From the aerodynamic point of view, in order to meet the requirements of supersonic flight, subsonic cruise and short takeoff and landing at the same time, it is best to make the wing sweepback angle adapt to different flight conditions with different sweepback angles.

The research of variable swept wing began in 1940s, but it was not until 1960s that a practical variable swept wing aircraft was designed. Generally speaking, the inner wing section of the variable swept wing is fixed, and the outer wing is connected with the inner wing through a hinge shaft. The back and forth rotation of the outer wing is controlled by the hydraulic booster, and the sweep angle of the outer wing section and the aspect ratio of the whole wing are changed. The disadvantage of variable swept wing is that its structure and control system are complex and its weight is heavy, so it is not suitable for light aircraft. American F- 14 fighter is a representative model of variable swept wing.

flank

Ribbon wing is a new type of wing that appeared in the mid-1950s. Some third-generation high-mobility fighters use this wing, such as the American F- 18 and the China-Pakistan Joint Research Institute Xiaolong.

A slender wing with a large sweep angle (sweep angle 65-85 degrees) is installed at the leading edge of the wing root of an aircraft with a medium sweep angle (sweep angle about 25-45 degrees), which is called a strake wing. Among the strake wings, the original swept wing is called the basic wing, and the additional slender front wing part is called the strake.

The aerodynamic characteristics of strake wing are that in subsonic and transonic range, when the angle of attack is not large, the airflow separates from the leading edge of strake, forming a stable leading edge separation vortex. Under the guidance of leading edge separation vortex, not only the lift of the inner wing section of the basic wing can be greatly improved, but also the airflow of the outer wing section can be controlled, and irregular separation does not occur within a certain angle of attack, thus improving the critical angle of attack and buffeting boundary of the wing and ensuring that the aircraft has. At supersonic speed, due to the addition of strakes, the relative thickness of the inner wing section decreases and the equivalent sweep angle of the wing increases, which can obviously reduce the impact resistance.

In addition, the existence of strakes can also reduce the backward movement of the whole center of gravity when the aircraft is flying transonic and supersonic, thus reducing the trim resistance of the aircraft. Therefore, this wing also has good supersonic aerodynamic characteristics. The disadvantage of strake wing is that its lift-drag characteristics are not as good as that of the basic wing without strake in a small angle of attack; Its torque characteristics are not ideal, and the torque curve is nonlinear with the angle of attack.

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