In the late 1960s, the Soviet Government began the search for a new long-range, extended endurance interceptor to replace its Tupolev Tu-28s and MiG-25 Foxbats. It was intended to counter the threat of low-flying cruise missiles launched from NATO/US B-52s and B-ls, which the MiG-25 was unable to do. MiG-25s functioned well as high-altitude interceptors with the help of ground control data links, as their original mission was to intercept the USAF’s high-altitude Mach 3 B-70 Valkyrie bomber. However, the B-70 never went into production on account of defence cutbacks. The Foxbat’s avionics and performance were largely ineffective against low-flying targets and so a more capable aircraft was needed.
From the late 1960s onwards, NATO bombers and attack aircraft changed tactics and were flying ever-lower attack profiles intended to avoid the growing threat of surface-to-air missiles (SAMs). Newly-introduced cruise missiles were also flying low and fast, proving difficult to intercept. The MiG-25 was unable to fly at supersonic speeds at low level, and this was a serious disadvantage in intercepting enemy aircraft and missiles. The Soviets needed a replacement that was supersonic at all altitudes and able to attack low-flying and multiple small targets. For this, far more efficient engines were required, together with completely new avionics and a dedicated rear crewmember to manage them.
Development of the new aircraft, designated MiG-31, began in 1967 and on May 24, 1968, the Soviet Government ordered production of a prototype, designated Ye-155MP. The MiG-31 was to carry the Zaslon phased array radar capable of detecting all types of aerial targets flying at long ranges and varying altitudes, making the MiG-31 independent from ground control. Under normal circumstances the rear radar operator would guide the pilot to the target, but the MiG-31 could also be guided by ground control using a digital datalink.
The Ye-155MP (serial 831) made its maiden flight on September 16, 1975, with chief test pilot Aleksandr Fedotov at the controls. The second prototype (serial 832) first flew on April 22 the following year, again piloted by Fedotov. This aircraft had the complete avionics suite, including the Zaslon radar and infra:red sensor, as well as reduced wing area and smaller under-fuselage fins. Sadly, Fedotov and his crewmember both died in a MiG-31 crash on April 4, 1984, when the aircraft’s systems failed. Development progressed slowly and by 1977 two pre-production aircraft (serials 011 and 012) had been built by the Sokol Aviation Manufacturing Plant at Nizhny Novgorod: 012 first few on June 30 and 011 on July 13, 1977. Compared to the first two prototypes, these aircraft had increased span flaps, revised wings, taller vertical tails and GSh-6-23 cannons, each cannon with six 23mm barrels. In May 1977 the first round of official testing began, ending in December 1978. Following satisfactory results, which included a MiG-31 tracking no fewer than ten targets simultaneously with its Zaslon radar on February 15, 1978, production at Sokol commenced in 1979. A wide variety of aircraft were used during MiG-31 testing , including two Tu-104s used to test the Zaslon radar, a MiG-21 for R-33 missile development, and three MiG-25s for R-33 missiles, engines and avionics integration. The second stage of official testing began in September 1979 and ended exactly one year later. Production started in 1979 and about 450 Foxhounds were built, the last production Foxhound being delivered in April 1994. Initial MiG-31 deliveries to Air Force units began in 1981 and by 1983 initial operational capability was achieved. By the end of the year, the MiG-31 was serving with eleven regiments, replacing MiG-23s, Sukhoi Su-15s and Tu-28s in the air defence role. By 1987, more than 150 MiG-31 s were deployed across the Soviet Union, notably in the east and west.
Around 315 MiG-31 s are believed to be in service with Russian air defence forces and tactical units, and around 34 in Kazakhstan: the latter aircraft, flying with the 356th IAP (Istrebitel’nyi Aviatsionny Polk or Fighter Aviation Regiment) based at Semipalatinsk, were left in Kazakhstan after the Soviet Union collapsed. The Sokol plant at Nizhny Novgorod has stated its willingness to re-start production of the MiG-31, to meet even small orders. So far none have been received, despite persistent reports of interest from Iran and Syria.
The first time the Western world got wind of the MiG-31 was when the Soviet pilot Viktor Ivonovich Belenko defected to Japan. Originally based at the 513th Fighter Regiment of Soviet Air Defence Command in Siberia, he flew his MiG-25 to Hakodate in September 1976. When questioned by the US (he went to America and was allowed to live there), he described the MiG-31 as a «super Foxbat» with two seats, a strengthened fuselage and powerful look-down/shoot-down radar. However, it was not until 1978 that the aircraft was first observed. A US spy satellite viewed one of the prototype or pre-production machines flying at 19,690ft (6,000m) intercepting a cruise missile-sized target drone flying at 200ft (60m) altitude and 12 miles (20km) from the MiG-31. In mid-1982 NATO designated the aircraft Foxhound’. The West finally got a good look at the MiG-31 in 1985 when a Norwegian pilot intercepted a Foxhound over the Barents Sea and took some pictures of it. It was suspected that this might have been a staged photo opportunity designed to unveil the aircraft.
‘Like A Rocket’
Although the MiG-31 looks roughly like the MiG-25, it is a completely new and vastly more capable machine. The basic Foxbat configuration has been retained, with high-mounted sweptback wings, a rectangular and diagonally cut air intake on each side of the fuselage, twin ventral fins under the tail and backward-tapered twin tail fins canted slightly outward. The MiG-31 has a new airframe strengthened to 5g, as opposed to the MiG-25’s 4.5g, making it capable of supersonic speeds at low altitude — it can fly at an impressive Mach 1.23 (932mph or 1,500km/h) at sea level. While the MiG-25’s airframe was constructed from 80% nickel steel, 11% aluminium and 8% titanium, the MiG-31 has a new airframe consisting of 49% arc-welded nickel steel, 33% light metal alloy, 16% titanium and 2% composites. This should have made the Foxhound a much lighter aircraft than its predecessor, but the addition of new systems ultimately resulted in the MiG-31 being considerably heavier than the MiG-25.
Pilots have said that the MiG-31 was sophisticated, fast, had a long range and could climb «like a rocket». And its lack of agility was more than adequately compensated for by its ability to engage virtually any possible target from an extremely long stand-off range.
The MiG-31’s wing is very different from that of its predecessor and has a new third main wing spar, which gives it significantly greater strength. The most notable difference is the new LERX (Leading Edge Root Extension), which have a sweep angle of 70°. Both wings are swept back at 41 °, have a small anhedral of 4° from the roots, and a fence mounted above each underwing stores pylon. Each wing has four-section titanium leading-edge slats that occupy the whole leading edge, two-section trailing-edge flaps and large span flaperons near the wingtips. The leading-edge slats deploy automatically at low speeds and are used for manoeuvring. The horizontal tailplanes are all-moving, and the vertical tails have inset rudders and shallow fairings forward of the base of the leading edge. The landing gear on the MiG-31 is also completely new and is a retractable tricycle type. The rearward retracting twin nosewheel unit moves into the fuselage, unlike the MiG-25, in which the nosewheels were further down the fuselage and retracted forwards. The main gear features two wheels on each main unit, retracting forward into an air intake trunk. Although the twin wheels are in tandem, they are slightly staggered, so that the rear wheel does not follow in the track of the front one, making operation easier from snow, gravel or unprepared ground. There is a small forward-hinged airbrake under the front of each engine intake trunk forward of the main gear doors. Other landing gear equipment consists of twin cruciform braking parachutes stowed in a fairing between and above the engine exhausts.
One of the most important requirements for the MiG-31 was not increased speed, but longer range, and in order to achieve this, new and more efficient engines were needed. The Aviadvigatel D-30F6 turbofan was chosen, though, surprisingly, it was not a new engine, being developed from a commercial turbofan and adapted to use high-density T6 fuel. In order to accommodate this massive engine (277.2in [7,040mm] long and with a diameter of 40.2in or 1,020mm), the air intakes were enlarged and, together with the fuselage, designed to contribute lift. Even though the fuselage was redesigned to accommodate the engines, the jet nozzles extend rearwards from the tail, unlike those of the MiG-25. Apart from being more efficient, the new air intakes also feature a moving inlet ramp and a lower moving inlet lip, and have auxiliary inlet doors in their roofs. Each engine produces 20,945lb (93.16kN) of thrust dry and 34,1701b (151.99kN) with afterburning.
The redesigned and lengthened fuselage was able to accommodate even more fuel than the MiG-25 -total internal fuel capacity is an incredible 4,386 Imp gallons (19,940 litres) in seven fuselage tanks, four wing tanks and two ‘wet’ fin tanks. This weighs a massive 34,1701b (15,500kg) and to keep the centre of gravity within limits is constantly shifted around the various tanks. There is also provision for two underwing fuel tanks, each with a capacity of 550 Imp gallons (2,500 litres), and a semi-retractable flight refuelling probe on the port side of the front fuselage, just ahead of the cockpit.
The MiG-31 design team originally considered placing the two crewmembers side by side, but in the end a tandem seat arrangement was followed. The pilot sits in front, with the weapons systems/radar operator behind. Both crew sit under individual rearward-hinged canopies, although the rear cockpit has only small side windows in its metal frame and is faired into a shallow dorsal spine which extends to forward of the jet nozzles. This gives the rear crewmember a very limited view and to compensate, he is provided with a retractable periscope. The rear cockpit has a simple set of flight controls, allowing the rear crew member to fly the aircraft in an emergency. Both crew sit on Zvezda K-36DM zero/zero ejection seats with built-in massage pads to keep them comfortable on long patrol missions. The pilot’s seat has a heated backrest to allow for extended periods of ground alert
One of the keys to the MiG-31’s success is its formidable array of advanced digital avionics, especially its long-range radar. Its primary sensor is the NIIP Zaslon (in full, this is actually N007 S-800 SBI-16 [RP-31] Zaslon, meaning Shield, though designated Flash Dance by NATO) electronically scanned, phased array, fire control radar. The first such radar to enter service, it offers exceptional performance, with a search range of 124 miles (200km) in a clutter-free forward sector and 56 miles (90km) rearwards, and can track targets at 75 miles (120km). It was also the first Soviet radar with true look-down/shoot-down performance. It can track ten targets and engage four of them simultaneously, the targets being prioritised by the aircraft’s Argon-15 digital mission computer. Also connected to the digital computer is a semi-retractable Type 8 TP infra-red search and track sensor below the cockpit.
Communications fit is fairly comprehensive, consisting of UHF and HF communications radios, identification friend or foe (IFF) transmitter and receiver and transponder. Most, but not all, MiG-31 s appear to have APD-518 digital air-to¬air datalinks — when flying in a four-aircraft group intercept formation, the lead aircraft is linked to the AK-RLDN automatic guidance network on the ground while the other three MiG-31 s have datalinks to the lead aircraft, permitting a line-abreast radar sweep zone 495 to 560 miles (800 to 900km) wide. The air-to-air datalink can be used to communicate with Antonov An-50 Mainstay airborne warning and control system (AWACS) aircraft. The MiG-31 is also fitted with the MB5U15K air-to-ground tactical datalink and BAN-75 command link.
Navigation avionics are comprehensive, as they were originally designed to allow the MiG-31 to patrol deep into Arctic airspace in search of threatening Western aircraft. Trial flights included such Arctic sorties, including one aircraft flying over the North Pole.
Navigation avionics consist of Marshrut long-range and Tropik medium-range radio navigation systems (similar to the US Omega and Loran respectively), as well as Shoran, Loran, radio compass, radar altimeter and marker beacon receiver. Other miscellaneous avionics consist of a voice warning system, intercom and radar homing and warning system (RHAWS). Countermeasures include active electronic warfare equipment and UV-3A flares dispensers.
Unlike the MiG-25, the MiG-31 has an internal gun, the GSh-6-23M six-barrel Gatling-type 23mm cannon, placed inside a fairing on the starboard side of the lower fuselage just behind the right landing gear door. It has a rate of fire of between 6,000 and 8,000 rounds per minute and is provided with 260 linkless rounds. It appears that early Foxhounds had only two underwing pylons, but aircraft now have four pylons. The MiC-31’s main weapon is the Vympel R-33 or R-33S (designated AA-9 Amos by NATO) long-range air-to-air missile (AAM) with a range of 70 miles (110km). Its guidance is either by semi-active radar homing or inertial with the option of mid-course update from the launch aircraft. Four missiles can be carried in pairs on AKU ejector pylons semi-recessed under the fuselage, similar to the Grumman F-14 Tomcat. Because the underside of the fuselage is flat and not ‘dished’ between the engine ducts as on the MiG-25, it is much easier for the MiG-31 to carry missiles under its fuselage. All four R-33s can be launched in salvo, each seeking out a different target simultaneously.
The MiG-31 can also carry two R-40T (designated AA-6 Acrid by NATO) medium-range infra-red homing or inertially-guided air-to-air missiles on the inner underwing pylons with a range of 48 miles (78km). Four short-range R-60 (NATO-designated AA-8 Aphid) infra-red homing air-to-air missiles with a range of 7 miles (12km) can be carried in pairs on the outer underwing pylons.
A large number of improved Foxhound derivatives were either produced or proposed. The first major modification was the fitting of the semi-retractable in-flight refuelling probe. Although the Foxhound did not originally need it, as range was considered adequate, the aircraft’s impressive performance prompted field commanders to consider it for other long-range missions, such as escorting maritime patrol aircraft. These missions challenged the Foxhound’s range so the refuelling probe was fitted to between 40 and 45 later-production aircraft and retrofitted to other early-production examples. Standard-production aircraft are designated Foxhound-A: those with the refuelling probe are unofficially designated MiG-31 DZ.
MiG-31 B: This was the second production and service variant with improved Zaslon-A radar, electronic countermeasures (ECM), electronic warfare (EW) equipment, improved R-40TD and R-60 AAMs, upgraded R-33S missiles, flight refuelling probe and improved A-723 long-range navigation system compatible with Loran/Omega and Chaika ground stations. It replaced the Foxhound-A in production in late 1990. Many older MiG-31 s were upgraded by the Gorky factory to this standard and were designated MiG-31 BS. In July 2000 an agreement was reached between the MiG company and the Russian Air Force to upgrade half the Air Force’s 280 MiG-31 s. It is not clear to which standard they will be upgraded: either the MiG-31 B standard or the superior MiG-31 BM.
MIG-31E: This designation is given to the export version of the Foxhound-A, the one and only prototype (serial 903) of which was first seen in 1997. It has downgraded systems, no active jammer, downgraded IFF and radar. It was offered to India, China and other countries, and is presumably the version the Chinese almost bought in 1992. The variant was later cancelled.
MiG-31 Eh: Designated Eh for Ehksport (export), this variant was proposed to China in 2000 and announced at the Zhuhai Air Show on November 6, 2000. It appears to have been rejected.
MiG-31 F: This projected multi-role interceptor and fighter-bomber would be able to carry a variety of TV, radar- and laser-guided air-to-surface missiles (ASMs). It would also feature other changes.
MiG 31BM: The MiG-31 BM designation was applied to a proposed defence suppression and ground attack variant based on the MiG-31 F. Work on the aircraft began in 1997 and in August 1998 a demonstrator was shown with R-33S missiles under its fuselage and R-77, Kh-58 and Kh-31P missiles under its wings’. The MiG-31 BM designation is now applied to the single-role interceptor upgrade to be applied to the MiG-31 Bs in service. The MiG-31 BM has replaced the original MiG-31 M upgrade originally offered. The aircraft is able to carry R-37M1 and R-77M2 air-to-air missiles, has upgraded radar, a satellite navigation system and new cockpit displays. MiG-31 Fs, FEs and BMs will all have an upgraded radar incorporating technology developed for the MiG-31’s Zaslon-M. This will give a detection capability against ultra high-speed targets travelling at more than Mach 6, and afford longer range, better resolution and new synthetic aperture and real-beam mapping modes for the air-to-ground role. The new cockpit displays consist of a head-up display (HUD), pilot’s tactical situation display, which is a 6 x 8in (152 x 203mm) colour Liquid Crystal Display (LCD), Multi Function Display (MFD), and three MFDs for the navigator. Weapons fit has been increased: the MiG-31 BM (and presumably the F and FE) can carry R-33S, R-37 and R-77 AAMs, as well as Kh-58E and Kh-31P anti-radiation missiles (ARMs) and possibly Kh-59, Kh-29L/T and Kh-59M ASMs3. Upgraded MiG-31 s may also incorporate structural changes to increase service life, but this cannot be confirmed. Two MiG-31 BMs were built and a prototype was publicly demonstrated in 1999, but lack of funding has hampered further development.
MiG-31 D: This was a dedicated anti-satellite model with a flat under-surface fuselage without recesses, with underwing Vympel anti-satellite missiles and no gun. It was also fitted with large triangular winglets above and below the wingtips to provide stability for missile launches at high altitudes. Two prototypes with ballast instead of radar in their noses were built in 1986 and flight-tested in 1987, but production was cancelled. A single missile and a special upward-looking radar and fire-control system was to be fitted to production aircraft.
MiG-31 FE/MF: This designation is applied to the proposed export versions of the MiG-31 BM or MiG-31 F.
MiG-31 LL: One early Foxhound was converted as a dedicated test aircraft (hence the LL, standing for the Russian acronym of ‘flying laboratory’) for use at the Zhukovsky flight test centre and was used as an ejection seat test-bed. It is also reported to have had fairings for cameras on its wingtips.
MiG-31 M Foxhound B The most important and capable Foxhound variant yet produced. Under development since 1984 and first flown on December 21, 1985, it was designed as a radically improved interceptor with upgraded engines, accommodation, avionics, weapons and more fuel. It incorporates new engines with modified nozzles, a one-piece rounded windscreen, small side windows only for the rear cockpit, a wider and deeper dorsal spine containing 66 Imp gallons (300 litres) of additional fuel and a fully retractable refuelling probe mounted on the starboard side of the fuselage. As a result of internal changes, fuel weight is increased to a massive 36,0451b (16,350kg). The wings were modified with larger curved root extensions and smaller upper wing fences. The tail was also modified, with taller fins featuring more rounded tips with flush dielectric areas at the front and rear. All systems were upgraded, some of the changes consisting of digital flight controls, multi-function cathode ray tube (CRT) cockpit displays (three are fitted in the rear cockpit) and a non-retractable pod with an infra-red search and track sensor and laser ranger. A new multi-mode Zaslon-M phased-array radar was introduced, with a larger 55in (1.4m) diameter antenna housed in a 3° downward inclined nose. Detection range has been vastly improved and is extended to 225 miles (360km).
Weapons fit was changed, the gun being deleted and the number of fuselage weapon stations increased to six by adding two centreline stations for R-37 air-to-air missiles, which can be fired in salvo and then seek out different targets, in addition to the side-mounted R-37s or R-33s. There are also four new underwing pylons for R-77 AAMs. An R-37 was first successfully launched from a MiG-31 M in October 1993.
The first prototype, produced by the conversion of a MiG-31 B, was lost on August 9, 1991, but was followed by another five prototypes. At least one had cylindrical wingtip ECM/ECCM (electronic countermeasures/electronic counter-countermeasures) jammer pods with upper and lower fins. Maximum take-off weight was raised to 114,6401b (52,000kg), with increased thrust D-30F6M engines to compensate. Development of the advanced MiG-31 M seems to have come to a stop due to funding cuts and it has not been ordered into production.
MiG-31 S: The designation is applied to a projected commercial variant for launching small satellites. It would carry the Fakel OKB Micron missile capable of delivering a 2201b (100kg) payload into a 124-mile (200km) orbit. It could also launch the Aerospace Rally System rocket-powered suborbital glider for astronaut training, atmospheric research or space tourism.
As Russia’s most capable air defence interceptor, the MiG-31 remains a powerful threat deterrent for the Russian (and Kazakhstan) Air Force. It has evolved into a highly-developed, advanced aircraft and, as the Russians want to keep their Foxhounds in service until at least 2010, further improved upgrades can be expected in the near future. Whatever the case, these important machines will still be flying for many more years to come.