The Sukhoi Su-24 (NATO reporting name: Fencer) is a supersonic, all-weather attack aircraft/interdictor developed in the Soviet Union. The aircraft features a variable-sweep wing, twin-engines and a side-by-side seating arrangement for its two crew. It was the first of the USSR's aircraft to carry an integrated digital navigation/attack system.[1] It remains in service with former Soviet air forces and various air forces to which it was exported. Development[edit] Background[edit] One of the conditions for accepting Sukhoi Su-7B into service in 1961 was the requirement for Sukhoi to develop an all-weather variant capable of precision air strikes. Preliminary investigations with S-28 and S-32 aircraft revealed that the basic Su-7 design was too small to contain all the avionics required for the mission.[3] OKB-794 was tasked with developing an advanced nav/attack system, codenamed Puma, which would be at the core of the new aircraft.[1] That same year, the United States proposal for their new all-weather strike fighter would be the TFX. The resulting F-111 would introduce a variable-geometry wing for greatly increased payload, range, and low-level penetration capabilities. In 1962–1963, Sukhoi initially set out to build an aircraft without the complexity of moving wings like the F-111.[4] It designed and built a mockup of S-6, a delta wing aircraft powered by two Tumansky R-21F-300 turbojet engines and with a crew of two in a tandem arrangement. The mockup was inspected but no further work was ordered due to lack of progress on the Puma hardware.[3] In 1964, Sukhoi started work on S-58M. The aircraft was supposed to represent a modification of the Sukhoi Su-15 interceptor (factory designation S-58). In the meantime, revised Soviet Air Force requirements called for a low-altitude strike aircraft with STOL capability. A key feature was the ability to cruise at supersonic speeds at low altitude for extended periods of time in order to traverse enemy air defenses.[3] To achieve this, the design included two Tumansky R-27F-300 afterburning turbojets for cruise and four Kolesov RD-36-35 turbojets for STOL performance. Side-by-side seating for the crew was implemented since the large Orion radar antennas required a large frontal cross-section.[3] To test the six-engine scheme, the first Su-15 prototype was converted into S-58VD flying laboratory which operated in 1966–1969.[3] The aircraft was officially sanctioned on 24 August 1965 under the internal codename T-6. The first prototype, T-6-1 was completed in May 1967 and flew on 2 July with Vladimir Ilyushin at the controls.[3] The initial flights were performed without the four lift engines, which were installed in October 1967. At the same time, R-27s were replaced with Lyulka AL-21Fs. STOL tests confirmed the data from S-58VD that short-field performance was achieved at the cost of significant loss of flight distance as the lift engines occupied space normally reserved for fuel, loss of under-fuselage hardpoints, and instability during transition from STOL to conventional flight.[3] So the six-engine approach was abandoned. By 1967, the F-111 had entered service and demonstrated the practical advantages and solutions to the technical problems of a swing-wing design. On 7 August 1968, the OKB was officially tasked with investigating a variable geometry wing for the T-6. The resulting T-6-2I first flew on 17 January 1970 with Ilyushin at the controls. The subsequent government trials lasted until 1974, dictated by the complexity of the on-board systems.[3] The day or night and all-weather capability was achieved – for the first time[3] in Soviet tactical attack aircraft – thanks to the Puma nav/attack system consisting of two Orion-A superimposed radar scanners for nav/attack, a dedicated Relyef terrain clearance radar to provide automatic control of flights at low and extremely low altitudes, and Orbita-10-58 onboard computer.[1] The crew was equipped with zero-zero Zvezda K-36D ejection seats, allowing the crew members to bail out at any altitude and flight speed, including during takeoff and landing.[1][3] The resulting design was slightly smaller and shorter ranged than the F-111 with a range of 3000 km (about 2000 miles) and payload of 8000 kg (about 18,000 lb). File:Pair Sukhoi Su-24M in flight.ogv A pair of Russian Su-24Ms in flight (2009). The first production aircraft flew on 31 December 1971 with V.T. Vylomov at the controls, and on 4 February 1975, T-6 was formally accepted into service as the Su-24.[3] About 1,400 Su-24s were produced.

• published: 25 Oct 2015
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