On August 2, 1966, a combat aircraft with variable-sweep wings, the Su-17 fighter-bomber, took to the skies for the first time in the USSR. The machine became the first domestic serial project of this class and opened a new direction for the development of front-line aviation.
The first flight of the experimental aircraft was performed by test pilot Vladimir Ilyushin. The development was carried out at the Sukhoi Design Bureau based on the Su-7 fighter-bomber, which by the mid-1960s no longer fully met the new military requirements.
The main problems of the Su-7 were high landing speed, limited electronics capabilities, and insufficient flexibility of application. The military wanted a more versatile aircraft capable of performing tasks at low altitudes, developing supersonic speeds, and using short field strips.
The wing that solved the problem of speed and landing
The main change in the new aircraft was the variable-sweep wing. The designers sought to combine two opposing characteristics: the ability to safely take off and land on short runways and the ability to effectively fly at supersonic speeds.
With a small sweep angle, the wing increased lift, reduced landing speed, and improved characteristics at low speeds. After rotating the wing consoles to a large angle, the aircraft experienced less drag and could overcome the sound barrier faster.
The concept of the wing's power scheme was personally proposed by Pavel Sukhoi. The fixed part of the wing was attached to the fuselage, and the rotating consoles occupied a significant part of the span. The maximum sweep angle reached 63 degrees.
TsAGI helped create a functional design
Creating an aircraft with variable-sweep wings was a complex engineering task. TsAGI specialists studied foreign projects and searched for a solution that would allow maintaining the stability and controllability of the machine.
Institute scientists found that a special shape of the wing root with a developed leading-edge extension allows maintaining the position of the aerodynamic center when the sweep angle changes. This reduced the negative impact of the wing rotation mechanism on the aircraft's characteristics.
Tests showed that the new scheme gave the Su-17 advantages in various flight modes. With a small sweep angle, take-off and landing distances were reduced, medium values provided better characteristics at transonic speeds, and maximum sweep allowed achieving high speeds with less air resistance.
From experimental S-22I to serial Su-17
After successful tests of the experimental aircraft, it was decided to launch the new fighter-bomber into series production. Production was deployed at the Far Eastern Machine-Building Plant in Komsomolsk-on-Amur.
The first production version was designated Su-17. Later, modernized versions Su-17M, Su-17M2, Su-17M3, and Su-17M4 appeared with improved electronics, engines, and expanded weapon application capabilities.
Until 1972, the aircraft was equipped with an AL-7F1-250 engine with a thrust of up to 9600 kgf in afterburner. Later versions received a more powerful AL-21F3 engine.
Speed over 2000 km/h and a wide arsenal of weapons
The Su-17 developed a speed of up to Mach 2.1 at altitude and could carry up to 4 tons of weapons on later modifications. The aircraft received two 30-mm NR-30 cannons, as well as the ability to use guided air-to-air and air-to-ground missiles, including Kh-23, Kh-25, Kh-29, and Kh-58.
The combat vehicle could use free-fall and cluster bombs, unguided rockets, and suspended gun pods.
In the mid-1970s, TsAGI specialists eliminated the Su-17's spin problem after research in a vertical wind tunnel. After confirming the results in flight, the aircraft received the necessary modifications.
Legacy of the Su-17
The Su-17 became the first Soviet combat aircraft with variable-sweep wings and one of the most notable projects of the Sukhoi Design Bureau of its time. Its design allowed combining characteristics that were previously considered difficult to reconcile: high speed, range, maneuverability, and the ability to operate from short airfields.
The experience gained in creating the Su-17 was used in the development of subsequent Soviet aircraft with variable-sweep wings.