Su-24 Fencer

Su-24 Fencer

The Sukhoi Su-24 (NATO reporting name: Fencer) is a supersonic, all-weather attack aircraft developed in the Soviet Union. The aircraft has a variable-sweep wing, twin-engines and a side-by-side seating arrangement for its crew of two. It was the first of the USSR’s aircraft to carry an integrated digital navigation/attack system. It remains in service with the Russian Air Force, Syrian Air Force, Ukrainian Air Force, Azerbaijan Air Force and various air forces to which it was exported.

Development

Background

One of the conditions for accepting the 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. OKB-794 (later known as Leninets) was tasked with developing an advanced nav/attack system, codenamed Puma, which would be at the core of the new aircraft. 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. It designed and built a mockup of S-6, a delta wing aircraft powered by two Tumansky R-21 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.

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. To achieve this, the design included two Tumansky R-27 afterburning turbojets for cruise and four Rybinsk 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. To test the six-engine scheme, the first Su-15 prototype was converted into S-58VD flying laboratory which operated in 1966–1969.

Design phase

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. The initial flights were performed without the four lift jets, 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. 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. The day or night and all-weather capability was achieved – for the first time 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 an Orbita-10-58 onboard computer. The crew was equipped with Zvezda K-36D ejection seats, allowing them to bail out at any altitude and flight speed, including during takeoff and landing. The resulting design with a range of 3,000 kilometers (1,900 mi) and payload of 8,000 kilograms (18,000 lb) was slightly smaller and shorter ranged than the F-111.

Ten fatal accidents occurred during Su-24 development, killing thirteen Sukhoi and Soviet Air Force test pilots.

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. About 1,400 Su-24s were produced.

Upgrades

Surviving Su-24M models have gone through a life-extension and updating program, with GLONASS, upgraded cockpit with multi-function displays (MFDs), HUD, digital moving-map generator, Shchel helmet-mounted sights, and provision for the latest guided weapons, including R-73 (AA-11 ‘Archer’) air-to-air missiles. The upgraded aircraft are designated Su-24M2.

Design

The Su-24 has a shoulder-mounted variable geometry wing outboard of a relatively small fixed wing glove, swept at 69°. The wing has four sweep settings: 16° for take-off and landing, 35° and 45° for cruise at different altitudes, and 69° for minimum aspect ratio and wing area in low-level dashes. The variable geometry wing provides excellent STOL performance, allowing a landing speed of 230 kilometers per hour (140 mph), even lower than the Sukhoi Su-17 despite substantially greater take-off weight. Its high wing loading provides a stable low-level ride and minimal gust response.

The Su-24 has two Saturn/Lyulka AL-21F-3A after-burning turbojet engines with 109.8 kN (24,700 lbf) thrust each, fed with air from two rectangular side-mounted intakes with splitter plates/boundary-layer diverters.

In early Su-24 (“Fencer A” according to NATO) aircraft these intakes had variable ramps, allowing a maximum speed of 2,320 kilometers per hour (1,440 mph), Mach 2.18, at altitude and a ceiling of 17,500 meters (57,400 ft). Because the Su-24 is used almost exclusively for low-level missions, the actuators for the variable intakes were deleted to reduce weight and maintenance. This has no effect on low-level performance, but absolute maximum speed and altitude are cut to Mach 1.35 and 11,000 meters (36,000 ft). The earliest Su-24 had a box-like rear fuselage, which was soon changed in production to a rear exhaust shroud more closely shaped around the engines in order to reduce drag. The revised aircraft also gained three side-by-side antenna fairings in the nose, a repositioned braking chute, and a new ram-air inlet at the base of the tail fin. The revised aircraft were dubbed “Fencer-B” by NATO, but did not merit a new Soviet designation.

Weapons

The Su-24’s fixed armament is a single fast-firing GSh-6-23 cannon with 500 rounds of ammunition, mounted in the fuselage underside. The gun is covered with an eyelid shutter when not in use. The armament includes various nuclear weapons. Two or four R-60 (NATO AA-8 ‘Aphid’) infrared missiles are usually carried for self-defence by the Su-24M/24MK.

Initial Su-24s had basic electronic countermeasures (ECM) equipment, with many Su-24s limited to the old Sirena radar-warning receiver with no integral jamming system. Later-production Su-24s had more comprehensive radar warning, missile-launch warning, and active ECM equipment, with triangular antennas on the sides of the intakes and the tip of the vertical fin. This earned the NATO designation “Fencer-C”, although again it did not have a separate Soviet designation. Some “Fencer-C” and later Su-24M (NATO “Fencer-D”) have large wing fence/pylons on the wing glove portion with integral chaff/flare dispensers; others have such launchers scabbed onto either side of the tail fin.

Variants

  • S6: An early project in the gestation of the Su-24, like a meld of the Su-7 and Su-15.
  • T6-1: The initial prototype with cropped delta wings and 4 RD-36-35 lift engines in the fuselage.
  • T6-2I / T6-3I / T6-4I: Prototypes for the variable geometry Su-24 production aircraft.
  • Su-24:  The first production version, the armaments include Kh-23 and Kh-28 type air-to-ground guided missiles, together with R-55 type air-to-air guided missiles. Manufactured 1971–1983.
  • Su-24M (‘Fencer-D’): Work on upgrading the Su-24 was started in 1971, and included the addition of inflight refueling and expansion of attack capabilities with even more payload options. T-6M-8 prototype first flew on 29 June 1977, and the first production Su-24M flew on 20 June 1979. The aircraft was accepted into service in 1983. Su-24M has a 0.76 m (30 in) longer fuselage section forward of the cockpit, adding a retractable refueling probe, and a reshaped, shorter radome for the attack radar. It can be identified by the single nose probe in place of the three-part probe of earlier aircraft. A new PNS-24M inertial navigation system and digital computer were also added. A Kaira-24 laser designator/TV-optical quantum system (similar to the American Pave Tack) was fitted in a bulge in the port side of the lower fuselage, as well as Tekon track and search system (in pod), for compatibility with guided weapons, including 500 and 1,500kg laser-guided bombs and TV-guided bombs, and laser/TV-guided missiles Kh-25 and Kh-29L/T, anti-radar missiles Kh-58 and Kh-14 (AS-12 ‘Kegler’) and Kh-59 (AS-13 ‘Kingbolt’)/Kh-59M TV-target seeker guided missiles. The new systems led to a reduction in internal fuel amounting to 85 l (22.4 US gal). Su-24M was manufactured in 1981–1993.
  • Su-24M2 (‘Fencer-D’): Next modernization of Su-24M introduced in 2000 with the “Sukhoi” program and in 1999 with the “Gefest” program. The modernized planes are equipped with new equipment and systems. As a result, they get new capabilities and improved combat efficiency, including new navigation system (SVP-24), new weapons control system, new HUD (ILS-31, like in Su-27SM or KAI-24) and expanding list of usable munitions (Kh-31A/P, Kh-59MK, KAB-500S). The last batch of the Sukhoi was delivered to the Russian VVS in 2009. Modernization continues with the program “Gefest”. All frontline bombers Su-24 in the Central Military District received new sighting and navigation systems SVP-24 in 2013.
  • Su-24MK (‘Fencer-D’): Export version of the Su-24M with downgraded avionics and weapons capabilities. First flight 30 May 1987 as T-6MK, 17 May 1988 as Su-24MK. Manufactured 1988–1992, sold to Algeria, Iraq, Libya, and Syria. Many Iraqi examples were evacuated to Iran.
  • Su-24MR (‘Fencer-E’): Dedicated tactical reconnaissance variant. First flight 25 July 1980 as T-6MR-26, 13 April 1983 as Su-24MR. Entered service in 1983. Su-24MR retains much of the Su-24M’s navigation suite, including the terrain-following radar, but deletes the Orion-A attack radar, the laser/TV system, and the cannon in favor of two panoramic camera installations, ‘Aist-M’ (‘Stork’) TV camera, RDS-BO ‘Shtik’ (‘Bayonet’) side-looking airborne radar (SLAR), and ‘Zima’ (‘Winter’) infrared reconnaissance system. Other sensors are carried in pod form. Manufactured 1983–1993. It is also being modernized.
  • Su-24MP (‘Fencer-F’): Dedicated electronic signals intelligence (ELINT) variant, intended to replace the Yak-28PP ‘Brewer-E’. First flight 14 March 1980 as T-6MP-25, 7 April 1983 as Su-24MP. The Su-24MP has additional antennas for intelligence-gathering sensors and radar jamming, omitting the laser/TV fairing, but retaining the cannon and provision for up to four R-60 (AA-8) missiles for self-defense. Only 10 were built.

Specifications

Crew 2 (pilot and weapons systems operator)
Length 22.53 m (73 ft 11 in)
Wingspan 17.64 m (57 ft 10 in) wings spread
10.37 m (34 ft) wings swept
Height 6.19 m (20 ft 4 in)
Wing area 55.2 m2 (594 sq ft)
Empty weight 22,300 kg (49,163 lb)
Gross weight 38,040 kg (83,864 lb)
Max take off weight 43,755 kg (96,463 lb)
Power plant (Dry thrust) 2 × Lyulka AL-21F-3A turbojet engines, 75 kN (17,000 lbf) thrust each dry, 109.8 kN (24,700 lbf) with afterburner
Maximum speed (Sea level) 1,315 km/h (817 mph; 710 kn) / M1.06 at sea level
Maximum speed (High altitude) 1,654 km/h (1,028 mph, 893 kn) / M1.6
Combat radius 615 km (382 mi, 332 nmi) lo-lo-lo attack mission with 3,000 kg (6,614 lb) of ordnance and external tanks
Ferry range 2,775 km (1,724 mi, 1,498 nmi)
Service ceiling 11,000 m (36,000 ft)
Rate of climb 150 m/s (30,000 ft/min)
Wing loading 651 kg/m2 (133 lb/sq ft)
Thrust/weight  0.6
Design load factor  +6g
Avionics SVP-24 targeting system
Armament Guns: 1 × internal 23 mm Gryazev-Shipunov GSh-6-23M rotary cannon with 500 rounds
Hardpoints: 9 hardpoints with a capacity of up to 8,000 kg (17,635 lb)

Operators

  • Algerian Air Force – 33 Su-24M/MKs, some upgraded to the M2 standard. 4 Su-24MRs.
  • Azerbaijani Air and Air Defence Force – 2 in service.
  • Islamic Republic of Iran Air Force – 30 Su-24MKs were in service as of January 2013. 24 Iraqi examples were evacuated to Iran during the 1991 Gulf War and were put in service with the IRIAF. Iran possibly purchased other Su-24s from Russia or other former Soviet States. Iran tested domestically produced, anti-radar smart missiles carried by Su-24 aircraft in September 2011, the IRIAF’s Deputy Commander, General Mohammad Alavi said, according to IRIB TV1.
  • Libyan Air Force – Six Su-24MKs were received in 1989. All were withdrawn after the Libyan Civil War, but forces loyal to Khalifa Haftar claim to have refurbished a number of the Su-24s.
  • Russia
    • Russian Air Force – 80 Su-24M2s and 79 Su-24MRs were in service in 2017.
    • Russian Naval Aviation – 18 were in service in 2012.
  • Indonesian Air Force – 11 aircraft on order.
  • Russia
    • Russian Air Force – 92 aircraft in inventory. The third order for 36 aircraft finalised in August 2020 is to increase the number to 128.
    • Russian Naval Aviation – 18 were in service in 2012.
  • Syrian Arab Air Force – 22 received. 20 Su-24MKs from the Soviet Union, 1 Su-24MK and 1 Su-24MR from Libya.[20 were in service in January 2013. All the Su-24MKs have been upgraded to Su-24M2 standard, between 2009 and 2013. The contract for that was signed in 2009 and the upgrade started in 2010.
  • Ukraine Air Force have 120 Su-24s. Only 23 in service.
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