Due to the development of air defense and guided weapons, the survival of light and medium bombers on the battlefield has become more and more difficult since the 1960s, and it is difficult to complete the mission alone. With the development of jet engines, fighter jets at this time already possessed capabilities comparable to those of early bombers. Whether in range or carrying capacity, they were already "comfortable" for low-intensity tactical bombing missions, so many countries believed that at that time Instead of letting fighters escort slow-flying bombers with huge targets, it is more cost-effective to develop fighter-bombers directly. From then on, the position of fighter-bombers on the battlefield began to rise, and gradually became an indispensable role in modern warfare.
The U.S. Army went to South Asia in the 1960s. In this war that lasted for nearly 10 years, fighter-bombers and ground attack aircraft began to be widely used. The ground forces can be supported with strong air support. Carrying out large-scale operations more calmly, fighter-bombers have also become the vanguard of ground forces.
Soviet short take-off and landing road
In view of this, the Soviet Union also began to pay attention to the development of fighter-bombers during this period, especially the aircraft with short takeoff and landing. Because the Soviets realized that once a war breaks out, a large airport is likely to become the enemy’s first priority target. In this case, it is very important to equip a fighter that can take off within a short distance. Have enough counterattack ability instead of lying on the ground and "waiting for death." However, at this time, the main fighter-bomber Su-7 equipped by the Soviet Union was least good at short takeoff. Not only that, this aircraft has particularly high requirements on the runway. This is obviously not the fighter-bomber that the Soviets wanted, and with the passage of time, the Su-7 that entered service in the 1950s has begun to lag behind in performance. For this reason, the military began to request the upgrade of this "old" fighter to cope with the current situation, and the only requirement was to modify it on the basis of the Su-7, with low cost and fast time.
At first, the designers wanted to shorten the take-off and landing distance by adding rocket propellers and retarders to the Su-7. Although this method is feasible, the carrying and maintenance of rocket thrusters is still a big burden for ground crews, and it is difficult to ensure that there is time for all fighters to install this kind of booster in a field environment. So this plan was abandoned after only a few trials.
external force cannot interfere, so we can only start from the aerodynamic layout and engine of the aircraft. At that time, the Western military had two common methods to shorten the take-off and landing distance of fighters. One was to use vertical take-off and landing, and the other was to introduce a variable swept wing design. This also attracted the attention of Soviet designers, but as far as the vertical take-off and landing aircraft is concerned, the engine requirements are too high, and once this method of take-off and landing is adopted, all the designs of the Su-7 fighter must be overturned and rebuilt. This is undoubtedly To develop a new type of fighter. Moreover, most of the design work of this type of aircraft was done by the Yakovlev Design Bureau, and the Sukhoi Design Bureau, which took over the modification task, had no similar experience at all. Therefore, the vertical take-off and landing scheme, which was not suitable in terms of time, cost and design experience, was also rejected.
Su-7
equipped with variable swept wings. Then, the variable swept wings became the only and best choice for the Soviets at that time. The Sukhoi designer’s idea is to add the simplest variable wing to the Su-7 fighter. When the sweep angle is the smallest, the fighter can get the maximum
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force and equip it with The AL-21F-3 turbofan engine, which was successfully "imitation" at the time, can not only solve the problem of takeoff and landing distance, but also greatly improve the performance of the aircraft. It saves money, and the modified part is within the acceptable range. The key is to greatly improve the combat performance of the aircraft. This plan was finally approved.
The birth of Su-17 "Assembler-B"
In 1965, the plan was launched, and the internal model of the new fighter was set as S-22I, by Ivanov, the chief designer of the Sukhoi Design Bureau. In the modification, the wing of the Su-7 fighter was strengthened, the leading edge was mechanized, the wing rotating mechanism driven by a hydraulic motor was installed, and the engine was replaced. However, in order to simplify the design and quickly put into mass production, the swept wing used by the Su-17 can only adjust the end of the rotating wing, and the wing root and inner wing are fixed. Variable wing design can be said to be "simple and crude". Because the purpose of the Soviets was to shorten the take-off distance, as for the good or bad air performance, they did not count on this wing. In addition, the designers also expanded the cockpit, replaced avionics, installed automatic control systems, and added weapon racks during the transformation. After a series of operations, the weight of the modified fighter aircraft has increased by nearly 400 kilograms compared to the original Su-7. This is also due to the data obtained from the substantial reduction in the weight of the engine.
In August 1966, the first test flight of S-22I was successful, and it was commissioned in 1970. The final model was Su-17. Western countries also called it "Assembler-B" (Su- 7 Known as the "Assembler"), this aircraft is also the first variable swept-wing fighter developed and equipped by the Soviet Union.
Su-17 performance parameters
The fuselage of Su-17 is made of all aluminum alloy, and the variable swept wing has three available angles: 30°, 45° and 63°. 30° is suitable for take-off and landing, 45° is used for cruising, and 63° is used for high-speed flight. Controlled by two GM-40 hydraulic motors.
Layout and avionics
The air intake method of the aircraft follows the traditional nasal air inlet of the Soviet fighter. The cabin is equipped with an electric heating system and KS-4S-32 ejection seat, the front three-point landing gear, and a deceleration parachute.
Avionics system is equipped with KN-23 navigation radar, KLEN-PS laser rangefinder, ASP-17BTS-8 sight, RV-5 altimeter, etc. A target positioning system is also installed in the nose position, which mainly provides positioning information for anti-radiation missiles.
Power configuration
In terms of power, the aircraft is equipped with an AL-21F-3 turbofan engine, which has a thrust of 109.8 kN after the afterburner. The origin of this type of engine is also legendary. It is reported that in the Vietnam War that year, the Soviets dismantled and transported the engine of the downed F-4 "Phantom" fighter jet back to China, and reversely imitated the general J79 turbojet engine equipped with it. . The successful development of the AL-21F-3 greatly improved the Soviet aero engine manufacturing capabilities at that time. It not only had a large thrust and low fuel consumption, but also had a much smaller volume than most of the same-level engines equipped in the Soviet Union.
In view of the advantages of the engine size, certain modifications have been made to the design of the tail. The extra space in the fuselage is used to equip the fuel tank, so the Su-17 can carry up to 4430 liters of fuel. The maximum flight speed is 1,400 kilometers per hour, and the combat radius is 1,150 kilometers.
Weapon External
The fixed weapon of Su-17 is two 30mm NR-30 cannons with 160 rounds of ammunition. In terms of plug-in, Su-17 has more than doubled its mounting capacity compared to Su-7. The aircraft can carry a total of more than 4000 kilograms of external ammunition and is equipped with 6 external weapon pylons, including two on the fuselage and four on the wings. On the Su-17M3, the number of weapon racks was increased to 8, and on the Su-17M4, there were 10. The ammunition that can be carried includes various types of unguided bombs of 100, 250, and 500 kilograms, R-3R/60/73 and other types of air-to-air missiles, Kh-23/25/29 air-to-surface missiles and rocket pods.
withCompared with the Su-7 fighter, the Su-17's range and combat power have been doubled, and its weapon mounting capability can also be described as "brutal" at the time. It perfectly solved the short range. The take-off and landing problem also continued the characteristics of the Su-7 fighter jets. Moreover, the problem of insufficient power was solved after the replacement of the American-like engine.
In the subsequent production process, the aircraft has undergone many modernizations and upgrades, and multiple versions of models have also been derived, including Su-17M, Su-17MKG, Su-17R, Su-17M2, Su- 17UM, Su-17M3, Su-17M4 and export models Su-20/22, etc.
Battlefield performance
Su-17 performed very well in the Soviet invasion of Afghanistan. It was the backbone of the Soviet Air Force's tactical strikes and aerial reconnaissance at that time, and was also responsible for aerial mine-laying tasks. The most commonly used ammunition for the Su-17M3/4 fighters participating in the war is FAB-250/500 bombs and 57/80mm rocket pods. However, due to the local high temperature and hot climate, the Su-17 on missions generally will not fly with full load. .
Through this actual combat, the Su-17 proved to be a relatively good fighter-bomber, with strong firepower and sturdy and reliable design so that it can calmly face any emergencies. Although 29 were lost in the war, half of them crashed due to accidents, and only a dozen were shot down in the battle (the loss in the 10-year war is pretty good). The export version of
Su-17 is the Su-20/22. Countries including Germany, Czechoslovakia, Hungary, Poland, Cuba, India, and Iraq have introduced this fighter.
