MiG-31 Foxhound.

Introduction
Mig 31, currently the only operating dedicated interceptor Fighter aircraft in the world, is a technological marvel even at today’s standard and an example of Soviet/Russian engineering about how they can squeeze the last bit of existing technologies to produce an aircraft which is unique and best for what it was intended for. When unveiled in 1981, it was the 1st for a lot of things in Fighter Aircraft Category. It is still the heaviest fighter aircraft ever produced, yet one of the fastest operational aircrafts in the world and normally those two don’t go together. It can’t supercruise, yet, it’s sustained supersonic flight at Mach 2.35 is higher than most 4th and 4.5th gen Fighter aircrafts’ maximum speed. It’s range at Mach 2.35 is over 750 km, higher than some of the medium class Fighters’ maximum combat range in Subsonic Speed. Even with the older hardware and avionics, it is still one of the best Russian operational Fighter with the best Network Sharing capabilities with all the other platforms, including other Fighter Aircrafts, SAM sites and other Russian / Soviet Air defense systems, a feature which was missing in most of Russian Fighters developed after it, until very recently. In this article, we will be drilling down to all the aspects of this marvelous Machine, not on the technical aspects but the geopolitical scenarios, Requirements, interesting facts, Espionages and the many more.

Why Soviet Union Needed a dedicated Mach 3 Interceptor
Normally Europe and USA, after 1950’s, especially after the introduction of guided missiles, never focused on a single purpose dedicated Interceptor Program. Instead, they forced on either air superiority fighters with a secondary role for Interception and Fighter-Bomber or Strike Fighters, dedicated for ground attack as short-range Bombers. However, for Soviet Union, the scenario was different, due to its vast Terran, multiple borders with enemy countries and not all of them could be brought under Ground Based Air Defense Systems. During 40’s and early 50’s, the only way to perform a tactical nuclear attack on enemy soil was the long range, Bombers. ICBMs were there but their roles were mostly strategic than tactical. All the bombers on that era, was slow Propellor or Turbo-Prop based high altitude but slow bombers like B-52 Stratofortress, B-57 Canberra etc. The Standard Soviet Fighter-Interceptors like Mig 21, Su-9, Su-15, were able to intercept those bombers.

However, things changed with the development of Mach 2+ nuclear weapon capable bombers by United States, notably Convair B-58 Hustler and Mach 3 capable XB-70 Valkyrie, potential to outclass any existing Soviet interceptors in Service. XB-70 Valkyrie project was cancelled eventually, but B-58 Hustler entered production in 1960, was capable of Mach 2 sustained speed at high altitude and carrying a single Nuclear Bomb (Later models added 4 under-wing hardpoints). Those above developments prompted Soviet Union to the Development of a close to Mach 3 capable Interceptor Aircraft which can accelerate at extreme rate, reach high altitude in very short time and can work with the Ground Controls to go straight and intercept those high-flying supersonic Bombers, resulting the Mig-25 FOXBAT, capable of flying over Mach 2.8, reaching altitude of 27 km or 68,000 ft, capable of intercept any Bombers in Service. It’s Smerch-A2 Radar with 600KW Peak Power could burn through any ECM systems in service that time

Left to Right: Vacuum Tube Valve used in Mig-25’s Radar. Smerch-A Radar based on Vacuum Tube Technology

Convair B-58 Hustler, Mach 2 Capable Bomber which contributed to Mig 25 development

Fun Fact: It was a military court-martial offence to turn on Mig 25’s Smerch-A2 Radar until full take off due to the immense power output. The emission from that radar was actually able to literally kill rabbits and pigeons in the airfields. There are lot of posts by the old soviet pilots that some actually used the radar to kill rabbits and birds in the airfield to avoid any accidents before takeoff.

Mig 25 to Mig 31 the Transition
In this section we will discuss the different aspects contributed to the development of a more modern Interceptor. Due to wrong western Intelligence and carefully crafted leaked information by Soviet Union, Western analysts completely misjudged the role of Mig-25 as a high performance, highly maneuverable, long range air superiority fighter, capable of Mach 3 with very advanced long-range Search & Track Radar and carrying very advanced long-range Missiles. The incidents over Israeli airspace where Egyptian air force branded Mig-25s, (flew by Soviet Pilots), flew multiple time and any interception by US fighters like F-4 Phantoms, were fruitless due to Mig-25’s extreme altitude and high speed, one time flying at Mach 3.2 (Which created permanent damage to the engine and airframe, rendering the aircraft unflyable permanently), did not help that. It went to a mythical status to Western air forces and forced US Airforce to add very high and stringent requirements to their FX program which ultimately resulted the creation of F-15 Eagle, still considered the best Air superiority Fighter by its record. It is funny and surprising that how incorrect intelligence information ultimately led to the birth of the best air superiority fighter. However, By the time the MiG-25 entered service in 1969, this was a serious shortcoming, as strategic bombing doctrine was shifting towards low-level penetration of enemy territory. Below are some of the main shortcomings of Mig-25 which led to the development of Mig-31.

• Short Range: Mig-25’s range was very limited compared to its size and it was never designed for air patrol or cruise. The sole intension was that it would fly at very high speed and high altitude towards the enemy Bombers, already identified by Ground Controls, shoot it down and come back to Base. It was never intended for air-space patrolling or searching of enemy by its own.

• Obsolete Avionics: Although immensely powerful, Mig-25’s radar was based on then obsolete Vacuum-Tube technology, not Semiconductor. That, while providing huge power output and immunity against Electromagnetic pulses coming from a nuclear explosion (very common thought process during Cold War era), did not have any long-range search capability, the beam was very narrow, resulting unable to perform volume search and lacked Look-Down Shoot-Down capability, making it unable to engage low flying Cruise Missiles and Fighter Bombers which can fly supersonic even at lower altitude.

• Old Engine Technology: Tumansky R-15B-300 Turbojets engine used in Mig-25, while being very powerful at high altitude and for sustained supersonic speed, was very crude and basic in nature. In lower altitude and subsonic speed, the fuel consumption was sky-high and it could not maintain supersonic speed at lower altitude, reducing its effectiveness against high-speed low flying Bombers like B1-Lancer or Fighter-Bombers like Panavia Tornado or SEPECAT Jaguar, which can not only fly over Mach 1 at lower altitude but also carried advanced AAM for self-defense, putting Mig-25 in serious danger

• Change in Enemy Airspace Penetration Tactics: This reason is one of the main contributors to the demise of Mig-25 as an effective Interceptor. With the advancement made in Surface to Air Missile systems, especially by Soviet Union, , capable of reaching extremely high altitude at very high speed, adversely effected the concept of high altitude supersonic strategic bombers, resulting Western countries cancelling those projects like retiring the B-58 or cancelling the XB-70 Valkyrie project altogether. Instead, the focus shifted on low altitude penetration, using cruise missiles, advanced low RCS Bombers like B1-Lancer and tactical Strike Fighters or Fighter/Bombers, capable of flying at very low altitude at supersonic speed and carrying advanced avionics and munitions. Mig-25 was completely outclassed and useless against these new threats.

Development of Mig-31 almost started at the time when Mig-25 entered service and Soviet Scientists and engineers were tasked to address all the above-mentioned shortcomings. The Ye-155MP (Russian: Е-155МП) prototype first flew on 16 September 1975. Although it bore a superficial resemblance to the MiG-25, it was a completely new aircraft. However, it was kept very secret like the Mig-25 project.
West came to know about the Mig 31 Project from the defected Soviet Pilot Viktor Belenko in his Mig-25, in September 1976 who informed that a far more powerful Interceptor was being worked on. He termed the aircraft as “Super Foxbat” with 2 crews, very powerful radar and capable of hunting Cruise Missiles. However, some of his information did not match the production Mig-31. After the above Event, all the technical capabilities and short comings of Foxbat got known to West and Soviet Union gradually shifted the role of Mig-25 as a Reconnaissance aircraft by adding high resolution camera, various sniffing pods for detecting nuclear radiation to identify nuclear sites.
Now this concludes the 1st part of the article, analyzing the Soviet need for dedicated Interceptor aircrafts and how different contributing factors had led to the development of the Mig-31. In the next part, we will discuss the Mig-31 technologies and impact in detail.

PART 2: Mig-31 Development, Technical analysis & Impact

Development:
The study of variants of fighters to replace the MiG-25P has been carried out since 1965. The project of the E-155PA heavy interceptor with R-15BF-300 engines and the Smerch-100 radar armed with K-100 missiles was studied . Since 1966, the development of a project for a two-seat multi-purpose aircraft E-155M, the prototype of the MiG-31, has begun. Below is the timeline for the design phase, various prototypes and final production Unit
.
• In 1968, Central Aerohydrodynamic Institute (Tsentral'nyy Aerogidrodinamicheskiy Institut, TsAGI) issued recommendations for the new aircraft.
• In 1972, tactical and technical requirements were formulated with an emphasis on increasing the flight range and duration of the interceptor loitering. One of the variants of the aircraft was supposed to be equipped with a variable geometry wing with two RD-36-41M engines developed by OKB-36 MAP (chief designer - PA Kolesov). However, it got cancelled in the later stage.
• After setting requirements for the possibility of conducting semi-autonomous actions to intercept targets in the absence of a continuous radar field, in 1972 a draft design of the E-155MP interceptor was developed led by General designer RA Belyakov.
• By 1976, GE Lozino-Lozinsky was the chief designer of the E-155M, besides him, the group of main developers included VA Arkhipov, KK Vasilchenko and AA Belosvet.From 1978 to 1985, the chief designer was KK Vasilchenko, later - AA Belosvet and EK Kostrubsky.
• An experimental prototype of the E-155MP / MiG-25MP (board No. 831, product 83/1) was manufactured by the MiG Design Bureau (MMZ plant named after AI Mikoyan, Moscow) in the spring of 1975. The first flight was made at the LII airfield in Ramenskoye on September 16, 1975 (pilots - AV Fedotov and VS Zaitsev). The second copy of the E-155MP-831 with the "Zaslon" radar complex was tested in 1976. Two copies of the E-155MP aircraft took part in the first stage ("stage "A") of joint state tests. • Two aircraft of the first installation series (MiG-31, product "01", tail numbers 011 and 012) were built by the Gorky Sokol aircraft plant in the summer of 1977. Structurally, the aircraft differ from the prototypes of the E-155MP.
• In 1977-1978. the second and third installation series of the MiG-31 were also released. Pilot series aircraft took part in joint state tests of the interception system, which began in May 1977.
• On February 15, 1978, the MiG-31 flew for the first time with simultaneous detection and tracking of 10 air targets. In 1978, according to Western data, at the Vladimirovka training ground, a MiG-31 intercepted a low-flying target flying along the profile of a cruise missile. Stage "A" of joint state tests was completed in December 1978. The Commission issued a preliminary conclusion on the launch of the MiG-31 into serial production from 1979.

Design and Airframe
Mig-31 is designed according to the normal aerodynamic configuration with trapezoidal wing, two-keel vertical and all-moving differential horizontal tail, two engines in the rear fuselage and a tricycle retractable landing gear. The design has some superficial similarities with Mig-25 from outside. However, special emphasis was placed to make the airframe and the wings much stronger to withstand high surface temperatures and vibration during high supersonic flight at higher altitude and supersonic flight at lower altitude. Below are some of the details of the component used.

• Some portion of the airframe is made of aluminum Alloy (up to 33%) which can withstand operating temperature of up to 150 degrees C. • Zones with high Kinetic Heating during speed approaching Mach 3, were made of Titanium (16%) and arc-welded nickel steel (50%).
• Composite material was only 2%. But the reason is during that time, there was no such composite material available to withstand the extreme heats, vibration and pressure Mig-31 needed to operate on.

What is Kinetic Heat: Aerodynamic heating is common phenomenon in every aircraft where the heat generates due to the friction between the airframe and the air. For aircrafts, flying at high supersonic speed, the effect of aerodynamic heating needs to be considered as the high amount of heat generated in the airframe, gradually transfers to the internal structure, Cabin, equipment bays, electrical and hydraulic systems. For supersonic aircrafts which need to cruise at that speed, special design needs to be made to the Wing design as well.

• Mig 31 Wing Design: An idealized wing structure is made up of spars, stringers, and skin segments. Stringers, also known as Longeron, is the load-bearing component in the Wing and it is used for the connection of the wing to the fuselage of the aircraft. During long supersonic flights, increase in temperature caused by energy flowing from the air (heated by skin friction at these high speeds) adds another load factor, called a thermal load, to the spars. During flight tests, changes were made to the aircraft design:
• 4-section deflectable socks were installed on the leading edge of the wing along the entire span.
• The wing structure was reinforced with a third spar (to increase strength when flying at high speeds).
• The location of the aerodynamic brakes was changed. The brake flaps simultaneously perform the function of the wings of the main landing gear.
• An aerodynamic ridge is installed on the upper surface of each wing console. Wing mechanization - slotted flaps, ailerons and four-section deflected wing socks. Side air intakes, adjustable by movable horizontal panels.

• Landing Gear: The landing gears of the Mig-31 were developed to not only support this heavy aircraft, but also take-off or landing in relatively simple and crude airfield, termed as Class II Airfields, marching then Soviet philosophy of enabling their military aircrafts to operate from unprepared and crude airbases, to enable maximum operability during a full-scale war.
• Main Landing Gear: It has two model KT-175 wheels but the tires used in those two are different to handle different working air-pressures, namely model 5A and 2A. The rear wheel has a shift outward relative to the front.
• Front Landing Gear: The front landing gear is equipped with two KT-176 wheels with model 11A tires.
• Component Used: All the wheels of the Mig-31 are equipped with metal-ceramic break discs.
• Airframe Performance: Despite having very strong airframe, MiG-31 is limited to only 5 g at supersonic speeds. At combat weight, its wing loading is marginal and its thrust to weight ratio is favorable. However, it is not designed for close combat or rapid turning.

The Engine
Mig-31 is powered by two D-30F-6 low-Bypass Turbofan engines, capable of generating 93 KN or 9,500 kgf Dry Thrust and 152 KN or 15,500 kgf Afterburning Thrust, enabling it to fly at max speed over 3000 km/h. The Thrust theoretically allows Mig-31 to cross Mach 3 barrier but that would cause severer damage to the Engine due to excess pressure and heat. Hence, Mig-31 has a hard speed limiter of Mach 2.83 which cannot be overloaded manually. It is also the 1st Soviet Fighter Aircraft to use a Turbofan engine. Just for comparison, even the Dry thrust of this engine is higher than maximum afterburning thrust of Snecma M88 (75 KN) in Rafale, Eurojet EJ2000 (90 KN) in Typhoon and almost same as the F414 (97 KN) in F/A-18 Super Hornet.

• Origin: Unlike other Soviet Fighter Aircraft engines, D-30F-6 Engine was not actually developed from a military engine. The base engine is Soloviev D-30, a Soviet two-shaft low-bypass turbofan engine, officially referred to as a "bypass turbojet" and was originally developed for Tupolev-134 Short-to-medium range jet airliner and went into production at 1966. This was developed in a very short period of less than 6 years and yet was one of the best reliable engines in the Soviet Union history.
In Mid 1970’s when the search for new Interceptor begun, Perm Engine Design Bureau under the direction of P.A.Soloviev, came up with this D-30F-6 variant based on the original design. The development of this engine was carried out in an experimental version of Mig-25. • The Engines were 1st installed on Mig-31, starting from the E-155MP prototype.
• Technical Details: The engine consists of 7 main modules as mentioned below:
o Low pressure compressor - 5 stages, air compression ratio - 5, bypass ratio - 0.57
o High pressure compressor - 10 steps, air compression ratio - 7.05, total pressure increase ratio - 21.15.
o Tubular-annular combustion chamber with 12 flame tubes. o High-pressure turbine - 2 stages, air is taken for cooling the blades from the 5th and 10th stages of the compressor. o Low pressure turbine - 2 stages.
o Afterburner - 4 annular flame stabilizers, ignition by the "fire path" method;
o Multi-leaf all-mode cooled nozzle with a variable area of the output section, the control system includes 18 cylinders;

• The engine is started using an auxiliary gas turbine engine located above the turbofan engine. • Various safety measures were taken to ensure the safety and reliability of the engine as it was very crucial for Mig-31’s sustained Mach 2+ speed at extremely higher altitude. Below are some of the details:
o low pressure rotor maximum speed limitation system and maximum turbine exit temperature limitation system.
o safety system against turbine overspeed (drive of constant revolutions).
o anti-icing system for the cowl and blades of inlet guide vanes.
o anti-surge system.
o Electronic-hydraulic system of automatic engine control is duplicated by hydraulic system ensuring safety of flight and back-up function in case of electronic system malfunction.

• Below is the chart showing the parameters of the Engine:

Fuel
Normally you don’t see a dedicated section for Fuel in a Fighter aircraft but for Mig-31, it is special. As a Mach 2+ Interceptor, the fuel consumption is very high compared to other Fighter Aircrafts which can only be supersonic for very short duration. For that, Mig-31 can carry 16300 kg of fuel in 13 fuel tanks distributed as 7 in fuselage, 4 in Wings and 2 in Keel Tanks. However, that is not the end of story. Mig-31 carries T-6 High Density Fuel with a freezing point of -62.2 deg C, a flash point of 54.4 deg C and a density of 0.83, which is slightly heavier than the US Navy JP-5 and USAF JP-6 high density fuels. This allows Mig 31’s Engine to produce more
energy by burning same volume of fuel and fly at extreme altitudes without the fear of fuel getting frozen due to the extremely low temps in higher altitudes. Similar concept was used in Mach 3 Cruising Capable SR-71 Blackbird. The outer wing pylons are also plumbed for drop tanks, allowing an extra 5,000 liters (1,320 gallons) of external fuel. Late-production aircraft have aerial refueling probes

Mig-31 Avionics Complex
Mig-31 has one of the most revolutionary Avionics systems for its time and it had the 1st Phased Array Radar in a Fighter and one of the most advanced and powerful system till 2000, before the Japanese Mitsubishi F-2 entered service with J/APG-1 AESA radar. However, there are more to it than just the radar. It was the 1st Soviet fighter to fly with a fully digital Computer ARGON15, 1st system to have two-way data link with Ground system and secure Data link for automatic Data sharing with other Mig-31s and guiding less advanced Fighters. The main emphasis of the Avionics complex design was to remove dependencies from Ground Control Systems as much as possible and network sharing to form a bigger virtual area defense system, sharing information to each other. We will go through and try to decode each of the components of the Avionics suite now
The main components of the Avionics Complex are listed below. We will drill down to the main components later in this article.
• Zaslon Fire Control System: this is heart of the avionics complex, consisting of the below components.
o Zaslon Radar, also known as RP-31 / N007 / SBI-16 / radar-8B, NATO Designated name FLASH DANCE. This is a Passive Phased Array Radar, one of the 1st to be fitted in a Military Aircraft and 1st for a fighter aircraft.
o 8TK IRST Sensor: The Development started in 1970 by NPO and since 1972, it had been equipped to the Mig-31 Prototypes, the E-155MP standard. This display of the IRST sensor was tied with the Gun targeting system and it was able to launch then Soviet Heat seeking AAMs like R-60 (AA-8 Aphid) and later it was made compatible with newer missiles like R-73 Archers. The total system weight was 124 kg. It can directly show the target information in one of the displays in WSO station.

• The detection range of a fighter-type target in the rear hemisphere when the target engine is running in the maximum mode is 40 km
• . Viewing sector:
o Horizontally: sector 120 degrees
o Vertically: from -13 to +6 degrees

o PPI-70V aiming and flight indicator is responsible for showing the target information and flight characteristics in the Big CRT display situated in the WSO Station. It also provides the fire control solution for the selected targets.
o 035M-7 (623-2) IFF (Identification of Friend and Foe): The antennas of this system were directly integrated in the Zaslon Radar and uses 64 L-Band TR Modules.
• RK-RLDN / 5U15K11 Secure Datalink for Ground Control Center: Also known as the Raduga-Bort-MB" complex, this provides receiving and decoding of signals from request signals Ground Stations, reception of information about target from automated ground-based control systems, using radio links "Lazur-M" and "Raduka-SPK". Then the information was sent to the Mission Computer ARGON-15 and to the PPI-70V targeting system. This allows Mig-31 to launch missiles to a target identified by Ground Station, without actually locking it.
• Even on today, there are hardly any Fighters which can do that. There are concepts going on to use 4.5 Gen fighters to be used as Missile truck along with a 5th Gen Fighter but nothing is yet in production.
• APD-518 Secure Datalink for Aircraft-to-Aircraft Data Sharing: This is used my Mig-31 to share data automatically to less capable aircrafts like Mig-23, Mig-29, Su-15, Su-27 and Mig-25 and in that mode, it works in Mini-AWACS mode. On top of that, 4 Mig-31s, speeded across 200 km, can exchange the air and terrestrial data automatically among them. While flying in a group of 4, standard for Mig-31 patrols, team lead is considered as Master and responsible for target allocation and the others are called Slaves. The different modes are:
o From Master (Team Leader) to Slaves o From Slaves to Master (Team Leader)
o From Team Leader of one group to team Leader of another group. Up to 4 Team leaders can exchange data in that way, which can then be transferred to each of the 3 slaves in their respective groups. In that way, up to 16 Mig-31s, scattered across 200 km of each other, can have all the data, shared by all the other aircrafts and if within range, can engage the enemy aircrafts or Cruise Missiles, spotted by any one of them. This Network capabilities allowed relatively limited number of Mig-31s to cover vast’ area.
o This also allows multiple Mig-31s working in a group to launch missiles on target identified by another Mig-31 and even directing a missile launched from other Mig-31 to a target. This allows Mig-31s to engage targets even longer range without being engaged by enemy Fighters. Zaslon Radar can detect Bomber sized targets (15- 20 m^2) at a distance of 200 + km but R-33 during that time, had effective range of 130-140 km at best. However, one of the Mig-31 can close the gap to the enemy flight group, normally consisting of Bombers / AWACS aircraft, surrounded by Escort fighters, say 90-100 km, launch salvo of R-33 Missiles and then turn around and flew back at Mach 2+ speed, allowing other Mig-31 sitting over 150km+ distance to guide the missiles. Due to the extreme speed, even today’s modern AAMs like AAMRAM are practically useless against a Mig-31 on tail-on Chase, running away at Mach 2+ speed.

• ARGON-15 Mission Computer: The brain of the Weapon System was the ARGON-K/ARGON-15 Mission Computer, the 1st fully digital computer system fitted in an aircraft. This was required to handle the powerful Phased Array Radar, Network Sharing and data gathering required by the complex avionics suite. The system weight was around 50 kg. In later version like Mig-31BM, it was relaced by more modern Baget 55-06 series computer

Mig-31 Cockpit Design: Mig 31 is a twin seat fighter with front cockpit occupied by the Pilot and the rear is for the Weapon System Officer (WSO). The pilot flies the plane via Center Stick and Left HOTAS (Hands on Throttle on Stick). Original version and initial upgrades likeMig-31BS, Mig-31 01DZ, don’t have glass cockpit and legacy dials, indicators, lights were used. The flying controls were duplicated to the WSO station as well, allowing the WSO to the fly the plane if necessary. Zaslon Fire control system was completely operated by the WSO. The Pilot has PPI-70V Heads-up Display, Small Indicator ITO-1 CRT display (with backlight Amplifier) to show tactical information relevant to the Pilot. This shows the health of the aircraft, Fuel level, altitude and other flight information. The WSO Station the large circular ITO-2 (CRT screen) showing the tactical situations, including the targets, tracking, data received from other aircrafts and Ground Controls and dual indicator of radar and IR channels

Mig-31M, Mig-31BM and Mig-31BSM Cockpit: The major upgrades, starting from Mig-31M (Started in 1984), Mig-31BM and Mig-31BSM versions, started to have partial or full Glass Cockpit Design, especially for the WSO Station. All the versions have 3 rectangular color AMLCD Panels, replacing the CRT Display. Those are capable of showing detailed tactical information, Satellite Navigation controls and Precision guided weapon controls, enabling the capabilities significantly. Mig-31M has a single LCD panel for the Pilot with rest remaining legacy controls. However, Mig-31BM and BSM version has almost full Glass Cockpit for the Pilot as well, consisting of two same sized rectangular LCD displays. These are similar to the Mig-29SMT Glass Cockpit.

• Navigation System: Mig-31 was built before the Satellite based Navigation system was introduced. Hence, it carried a complex Navigation system, consisting of automatic Flight Control, short range navigation and log range navigation equipment. Below are the details: -
o Navigation Complex Polyot-1: This is the automatic Flight Control System SAU-155МP, sighting-navigation complex KN-25, consisting of two internal subsystems I P-1-72A with a digital Computer called Maneuver.
o Navigation Complex 2: Consisting of the below components:
• system of short-range navigation, landing and determination of coordinates "Radikal-NP" / A-312
• radio-technical system of long-range navigation "Kvitok-2" / A-72
• long-range navigation system "Tropic" (an analogue of the LORAN system, provides CVO 130-1300 m on a route up to 2000 km)
• long-range navigation system "Route" (analogous to the OMEGA system, KVO 1800-3600 m on the route 2000-10000 km) ensure following the selected route and returning to the airfield in automatic mode.
• radio altimeter A-031; automatic radio compass ARK-19; marker radio A-611
• RWR: Mig-31 uses SPO-15LM "Bereza" Radar Warning System.
• Radio stations: VHF R-800LG, R-862; KV R-864 / R-844

Zaslon Radar in detail

In this section, we’ll discuss about the Zaslon Radar, the design philosophy behind it, the upgrades in later variants and also try to answer one question, why the later and more modern aircrafts like Su-27 or Mig-29, did not come up with a Phased Array Radar. Before jumping to Radar details, lets just go through some technical terms about what define the performance of any Radar, irrespective of its Type (MSA or ESA). Power Aperture Product (PA or PxA) [Wm2, dBWm2, dBW] in its most commonly used form is calculated by multiplying Peak (or Average) Power x Antenna Area (or Power [dBW] + Antenna Gain [dB] in [dBW]). It is a parameter used by designers to gauge the relative performance of different radar designs. To the first order, the radar with the higher Power Aperture Product or PA will achieve better range, detection and jammer burn through performance.
• Design requirement: As discussed earlier, the requirement for the new Interceptor was to not only perform long range engagement of enemy Strategic and tactical aircrafts but engaging low flying supersonic Strike Fighters and low RCS Cruise Missiles. Also, it was needed to have very high ECCM capability against advanced Jammers used by Western Bombers and Fighters and perform wide area search without the help of Ground Control. Multiple radars were considered, including an upgraded version of Mig-25’ radar, called Smerch-100. However, since 1968, the Research Institute of Instrument Engineering (later renamed NPO Fazotron) has been developing the Zaslon radar station, under the scientific and technical work supervisor V.K. Grishin (later - the general designer of NPO Fazotron). Some of the main components of the Radar are: -
o antenna with electronic beam deflection system.
o transmitting device.
o receiving device.
o master block with synchronization system.
o system for interfacing with on-board equipment.
o digital computing system.
o objective control system.

• The Radar is a multichannel system, comprising of two separate electronically controlled arrays, an X band radar with 1700 emitters and a L band transponder with 64 emitters brought together into a single antenna. The Diameter of the antenna is 1.2m, which is huge even in today’s standard. Su-35’s Iris-E has a diameter of 900mm, in comparison. The Peak Power output information is exactly available for Zaslon Radar but it is speculated to be 6W-8W category, resulting a very high-Power Aperture Product (PA), hence providing the extra range and burn through performance. The antenna is a semi-circular fixed planner array, with a ferrite core behind the antenna, consisting of hundreds of Phase Shifters, connected to the TWT Transistor power source electronically. The Ferrite core are affected by generated Electromagnetic filed, to generate the Phase Shifts of the signals to the antenna transmitting modules. This is one of the main factors for Zaslon’s long range and ability to detect low RCS targets. Because of the Electronic Beam Steering and use of a fast digital computer, it is able to position beams in 1.2ms, which is nearly instantaneous and enables high resistance against Jamming. This allows Mig-31 to guide 4 R-33 missiles in Semi-Active Mode to 4 separate targets. Even some of the 4.5th Gen Fighters can only guide 2 Semi-Active missiles. The Radar can track 10 targets and engage 4 of them simultaneously using R-33 Missiles. The choice of those 4 targets for attack is done by the onboard Computer.
• The limitation of only 10 targets was not due to the Radar’s performance but due to the lower computational power available then.

• Below are the technical details for this radar
o Wavelength range - S (NATO classification, approx. 3 cm), X (according to domestic data), 9 to 9.5 GHz Band.
o Antenna diameter - 1.1 m.
o Power: Peak: 6W-8W (Approx), Average: 2.5KW
o Low Level Target Detection: As low as 25m above the ground.
o Weight - 1495 kg
o Air target DETECTION range:
▪ in the front hemisphere (Head-On): maximum 320 km
• 150-200 km (RCS 19 sq.m) • aircraft with RCS 5 sq.m - 180 km
▪ in the rear hemisphere (Tail-On) - 90-150 km
• 90 km (RCS 19 sq.m)
• Fighter Type targets -16 - 120 km
▪ B-1B type targets - 200 km
o Air Target TRACKING range
▪ in the forward hemisphere:
• bombers – 120-150 km
• fighters (RCS approx. 5 sq.m) - 90 km
▪ Rear hemisphere:
• bombers – 90-120 km
• fighters - 70 km
o Radar surveillance sector (detection and tracking):
▪ detection in azimuth sector 160 degrees. (+-45 degrees with movement of +-35 degrees)
▪ tracking in azimuth sector 140 degrees
▪ vertically - from -60 to +70 degrees
o All the above modes work in the entire field of view of the Radar, unlike the AN/AWG-9 Radar in F-14 Tomcat, the most advanced US Fighter Radar during that.
o Detection against low RCS targets like Cruise Missiles: As per the published Test results, which were also observed by a US recce satellite, Mig-31, flying at a height of 6000 meter / 20,000 ft, was able to detect a test target of 1 sq.m RCS, flying at 60-meter height, at a distance of 20km and destroyed it.

• • Later Development, ZASLON-A and Zaslon M:
  o Zaslon-A: It was discovered in 1985 that, Adolf Tolkachev, the chief engineer of the Zaslon Project, was working as a CIA Spy during 1975-1980 and passed information about R-23, R-24, R-33, R-27, and R-60 missiles, S-300 air defense system and detailed avionics about Mig-25, Mig-31, Su-27 and Mig-29. He did that not for money but due to Stalin’s Oppression for which his wife’s parents suffered deeply. He was arrested by KGB in 1985 (And executed as a Spy) but KGB kept that a secret and fed wrong information to CIA for next 10 months in his name. Because of that, a new version of the compromised radar was hostility developed as Zaslon-A with different programming and slight alteration of the parameters. It was not really a new radar but slightly altered version of the original Zaslon. It entered service in 1990 and the aircrafts with this Radar was designated as Mig-31B. This Radar was compatible with the upgraded R-33S missiles with longer range.

• Zaslon-M Radar: Zaslon-M Radar was developed as part of the Mig-31 modernization program (Mig-31M and Mig-31BM) started in late 90s and as per the reports, it has twice the range compared to original Zaslon Radar. The Antenna size has been increased to a massive 1.4m Diameter and the Power output to 10KW, resulting even a higher range and better ECCM capability. On top of that, the Signal Processor and the computer system have been upgraded as well and it has three channel receivers compared to two in Zaslon. It has a detection range of 400km against 20 m2 RCS target, nearly 250-300 km range against Fighter sized targets (5 m2 ), and compatibility with the new 300-400 km range R-37 (AA-13 Axehead) Hypersonic Missile as well as other medium range missiles like R-77 and Semi-Active R-24. This can simultaneously track 24 targets and can attack 8 targets using Active Radar guided missiles / 4 with semi-active Missiles. As per the reports, it can detect a 0.3 m2 object flying as low as 50 meters above the ground, at a range of 64 km. This radar is also compatible with modern Russian precision guided weapons, laser / GPS / TV Guided bombs and Air-to-Surface Missiles, giving the new Mig-31BM true multirole capability.
  

• Why No Aircraft with Phased Array Radar by West & Russia after Mig 31 during that time: Mig-31 was the only Fighter Aircraft till 2000 with any kind of Electronically Scanned Array Radar. Now the question may arise that Soviet Union was able to develop a Phased Array Radar in 1980s which was superior in every aspect to all Soviet and Western Fighter Aircraft Radars but why they did not equip their more modern fighters like Sukhoi Su-27 and Mig-29 with one and why West, mainly USA did not include an PESA radar in their fighters despite having superior Electronics, Computer, Semiconductor and fabrication process than Soviet Union. We will try to answer the question in two parts.
  

• Why USA/Western Countries did not included ESA Radar: Mig-31 may be the 1st fighter with ESA Radar but American B-1B lancer Supersonic Bomber is the 1st Military aircraft to have one (It’s a Bomber Aircraft) with its AN/APQ-164 and it 1 st flew on 1977, before Mig-31’s introduction in service. But no Fighter Aircrafts like F-15, F-16, upgraded F-14, had one and all of them were using Planner mechanically Scanned Array Radar. The reason behind that is that Western countries shifted their focus from dedicated aircraft for single roles to Air Superiority Design with multiple secondary roles like Interception, Ground Attack etc. On top of that, American philosophy was always flying in a tactical formation with separate AWACS, ECM aircrafts providing support to the air-superiority fighters unlike Soviet Union, lacking resources on those fronts and needed autonomous operational capabilities. On top of that, although the technology was available to west during late 60s and early 70’s, the weight and size penalties of this design technique outweighed its usefulness in fighter applications because the whole avionics suite for a Phased Array Radar (Including the antenna, Transmitter, Power source, Computer System) could have been very big and heavy, not suitable to place in a nimble and maneuverable Air Superiority Fighter without affecting its flight performance gravely.
  

• Why next Gen Russian Fighter Did not have ESA Radar: Fighters like Su-27 and Mig-29 were developed after Mig-31 but they did not come with PESA Radar. Su-27 came up with N001 Myech and Mig-29 with N019 Rubin Radar and those two were not even based on a Planner Array MSA but using even inferior Twisted Cassegrain MSA Antenna, even inferior to normal Planner Array antenna based Mechanically scanned Radars. In fact, the initial plan was to create a smaller version of Zaslon Radar to be fitted at least in Su-27 as that aircraft has good volume to accommodate a reasonably big radar complex. But Soviet engineers faced the same issue as the western countries, crafting a system with reasonable size and weight which should not hamper the Fighter’s performance, due to technological limitation during that time. On top of that, they found out that Adolf Tolkachev, the chief engineer of the Zaslon Project, was working as a CIA Spy during 1975-1980 and might have passed information regarding all the past, running and future projects, including Zaslon Radar and Mig-29 and Su-27 projects. That had led to hastily developing completely new radars for those two aircrafts at very short time, resulting older Mechanically scanning and inferior Twisted Cassegrain antenna. Su-27 derivative, Su-37 Terminator received its 1st PESA Radar N011M in 1996, more than 15 years after Mig-31.
  

• Fun Fact: The Zaslon radar was publicly unveiled at the 1991 Paris Airshow with its associated MiG-31 interceptor, the Russians even removing the radome of the fighter to allow the Zaslon's revolutionary antenna to be seen. Also at Paris was the US F-117 Nighthawk (revolutionary for its use of stealth technology) which the Russians suggested should take to the air with the MiG-31 to see if the Zaslon could detect the F-117. Unfortunately, no such contest was ever conducted though Russian experts were confident that Zaslon would have been able to detect the F-117 during flight
  

Mig-31 Mission Computer, Argon-K/Argon-15