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MiG-31: Intercepting the SR-71

Intro

The Cold War inspired a battle for supremacy in the skies which spawned countless iconic American and Soviet aircraft. We’ve already discussed a few of them on this channel, but today we are here to talk about the Mikoyan MiG-31 Foxhound.

Though less well-known than the MiG-29, the -31 was similarly important to the battle for dominance of the skies during the Cold War. While the -29 was defined by its rivalry with the F16, the -31 was a response to the American SR-71 Blackbird. Today we’ll dive into what made this plane so special.

Origins and Development

While the MiG-31 was officially introduced into the Soviet Air Forces in 1981, the origins of the plane began well over a decade earlier. The Cold War was, of course, a war without direct conflict between the Soviets and the Americans, but this didn’t mean that their aircrafts didn’t compete directly with one another. The American SR-71 Blackbird was introduced to the world in January of 1966, and it took the abilities of aircrafts to a higher level, literally. The Blackbird was a strategic reconnaissance aircraft with the ability to fly at speeds over Mach 3 and at an altitude of 88,000 feet (26,822 meters). Together with the rest of the American fleet, these aircrafts posed a major threat to the Soviet Union, as they had no interceptors capable of protecting their airspace from infiltration at such a high altitude, and surface-to-air missiles were not fast enough to pose a real threat.

This led to the introduction of the MiG-25 Foxbat, which first flew in 1964, but wasn’t introduced into the Soviet Air Force until 1970. The -25 had a maximum speed of Mach 3.2, though this speed was impossible to reach without sustaining long-term damage to the engine or airframe, but it could safely reach speeds of Mach 2.83, making it the fastest-ever manned Soviet aircraft. When the Americans saw photos of the Foxbat, they were concerned with its large wings, believing that they signified high maneuverability. However, the -25 struggled with maneuverability at high speeds, as the large wings were primarily included to support the excessive weight of the aircraft, which came in at over 38,101 kgs (84,000 lbs) when fully fueled and equipped. It was also difficult to fly at low altitudes, and lacked much of the technological refinement required to pose a real threat to the SR-71, especially in regards to its air-to-air missile capabilities. None of this is to say that the -25 wasn’t a capable aircraft, of course. After all, it has the fastest maximum speed of any in-service manned aircraft in the skies today, but clearly it needed to be improved upon.

The Soviets got back to work on a new long-range interceptor that combined the speed and altitude of the -25 with a high-tech cockpit capable of controlling Soviet airspace. This meant that, though it was inspired by the -25, the -31 was designed to replace the Tu-128, a massive 30-meter long interceptor whose only successful combat mission was against a reconnaissance balloon. As such, the aircraft was designed to achieve four key responsibilities. First, intercept cruise missiles and their launch aircraft by reaching combat range in the lowest possible time after take off. Second, detect and destroy low flying cruise missiles, UAVs and helicopters. Third, the long range escort of strategic bombers. And fourth, provide strategic air defense in areas not covered by ground-based, air defense systems. These goals required extreme improvements in the radar and weapon systems, as well as the ability to communicate effectively within units, all while maintaining a comparable speed to the -25.

The United States learned of the Soviet’s development of a new interceptor in 1976, when a Soviet Air Defence Forces pilot, Lt. Viktor Belenko, defected to Japan in his MiG-25P. He landed at Hakodate Airport in Hokkaido, Japan, and, though he damaged his landing gear by overshooting the runway, his plane represented the state-of-the-art technology in Russian aircrafts at the time. The Japanese invited the U.S. Air Force to dismantled and analyze the -25, and, after 67 days, it was returned to the Soviets in pieces. While meeting with the US Air Force, Belenko informed them of the development of the upcoming “Super Foxbat”.

Just weeks after Belenko’s defection, a prototype of the -31, called the Ye-155MP, took flight for the first time on September 16th, 1976. In 1979 the -31 was approved for serial production, and on May 6th, 1981 it was officially introduced into the Soviet Air Forces.

Design and Capabilities

From the outside, the new plane bore a striking resemblance to its predecessor, and their dimensions tell a similar tale. While the MiG-31 Foxhound stood 6.45 m (21 ft) tall and 22.6 m (274 ft) long, the -25 was 6.1 m (20 ft) tall and 23.8 m (78 ft) long. Their wings were almost identical, with their total wing area separated by just .2 square meters (2 sq ft) at 61.6 square m (663 sq ft) for the -31 and 61.4 square m (661 sq ft) for the -25, and with wingspans of 13.456 m (44 ft 2 in) for the -31 and 14.01 m (46 ft 0 in) for the -25. While the -25 was considered a heavy aircraft when it was introduced, the -31 was even heavier, coming in at a gross weight of 41,000 kg (90,390 lb), which is over 4,000 kg more than its predecessor.

Their maximum speeds are essentially identical at high altitude, that is, as long as we’re considering the maximum speed at which the plane’s engine and airframe aren’t at risk, with each one clocking in at 3,000 km/h (1900 mph) or Mach 2.83 at a height of 70,000 ft. However, at low altitude, the -31 vastly outperforms the -25, with the former coming in at 1,500 km/h (930 mph) or Mach 1.21 and the latter at 1,100 km/h (680 mph), placing it safely in subsonic territory. While these figures place both of these aircrafts among the fastest ever manufactured, they’re well below the SR-71, which could reach speeds of 2,200 mph (3,540 km/h) or Mach 3.32 at 80,000 ft.

One area where the -31 outperforms both the -25 and the SR-71 is in rate of climb, as the -31 can ascend at 288 m/s (56,700 ft/min), with the -25 reaching 208 m/s (40,900 ft/min), and the SR-71 at a relatively slow 60.0 m/s (11,820 ft/min). The -31 also has the highest G limit, maxing out at 5 Gs, while the -25 maxes out at 4.5, and the SR-71 at 3. This is to be expected, though, as fighter planes need to perform high G force maneuvers compared to spy planes.

Another key improvement for the -31 over the -25 was in flight range. Ranges can vary immensely depending on speed and elevation, but at optimally fuel efficient speeds the -31 has a ferry range of 3,000 km (1,900 miles), compared to 2,575 km (1,600 miles) for the -25. The Foxhound also has the ability to refuel mid-flight via Russian air tankers, extending the range by over 2,000 km. As for its powerplant, the -31 uses two Soloviev D-30F6 afterburning turbofan engines, each one generating 93 kN (21,000 lbf) of thrust when dry, and 152 kN (34,000 lbf) with afterburners.

Those numbers may not seem too overwhelming compared to the SR-71 and -25, but the areas where the -31 really excels are in the avionics, radar, and weapon systems. The weapons control system is built around a phased array radar, making the -31 the first fighter plane to include such a system. The radar, tracking, and weapons systems extend 70 degrees to the right and left of the plane, 70 degrees upwards, and 60 degrees downwards, allowing it to fire at enemy aircrafts well above or below it. The radar extended 200 kilometres (120 mi) forward, and, along the front of this range, it extended to a width of 225 kilometres (140 mi).

Upon its introduction in 1981, the -31 could simultaneously track up to ten targets and attack four, while the modern system allows tracking of twenty-four targets and attacking six. Not only could a single -31 track all these targets, but they automatically exchanged radar-generated data with other -31s within 200 km, and could even direct fighter jets with less sophisticated avionics to targets acquired by its radar. This meant four MiG-31s could control an area of airspace up to 1,000 km (621 miles) wide.

The weapons system includes three classes of air-to-air missiles: four R-33E long-range missiles for large targets like the SR-71, four R-60MK short-range light missiles, and two R-40RD, which are the largest long-range air-to-air missiles ever produced. As of 2013, the -31 was one of two aircrafts in the world capable of firing long-range air-to-air missiles. It also included a six-barrel, twenty-three mm rotary cannon, carrying 260 rounds. While these are the standard armaments, -31s are also capable of carrying air-to-surface missiles or bombs. This advanced and complex system required a second pilot, which is why, unlike the -25, the -31 includes two cockpits.

Operational History

The MiG-31 entered serial production in 1979 and stayed in production until 1994, with a total 519 -31s produced in that span. 349 of those were baseline models, while the other 170 of them were made in fifteen different variations. The overwhelming majority were flown by the Soviet Air Forces, then the Russian Air Force, though the Kazakhstan Air Force inherited 50 of them when the Soviet Union dissolved. In 2007 the Syrian Air Force ordered eight -31s from Russia, and, though the Russian government has denied ever fulfilling this order, the Turkish government claims that six were delivered in 2015.

Throughout its time in operation, a -31 has never fired a missile at an SR-71, but that’s not say that they weren’t an effective deterrent of the Blackbird spy plane. Reports from both American and Soviet pilots tell of at least two intense confrontations of the two planes in 1986. The first comes from a book by aviation expert Paul Crickmore titled “Lockheed Blackbird: Beyond the Secret Missions”. It includes an anecdote told by Foxhound pilot Captain Mikhail Myagkiy, which sheds some light on a confrontation with an SR-71 on January 31st, 1986.

Myagkiy says, “The scheme for intercepting the SR-71 was computed down to the last second, and the MiGs had to launch exactly 16 minutes after the initial alert. (…) They alerted us for an intercept at 11.00. They sounded the alarm with a shrill bell and then confirmed it with a loudspeaker. The appearance of an SR-71 was always accompanied by nervousness. Everyone began to talk in frenzied voices, to scurry about, and react to the situation with excessive emotion.”

Myagkiy’s Foxhound locked onto the Blackbird from a distance of 120 km, at an altitude of 52,000 feet. Myagkiy claims he could see the Blackbird with his naked eye after ascending another 13,000 feet to meet its elevation. He continues, “Had the spy plane violated Soviet airspace, a live missile launch would have been carried out. There was practically no chance the aircraft could avoid an R-33 missile.”

Another confrontation occurred on June 3rd, 1986, as six -31s intercepted a single SR-71 over the Barents Sea, but, again, no missiles were fired. According to all parties involved, this was the final time that an SR-71 flew a reconnaissance mission over the Soviet Union, and a few years later the Blackbird was retired. While many SR-71 pilots have claimed that they never felt threatened by the -31, it seems clear that the Soviet interceptor had at least achieved its goal of deterring the spy planes from Soviet air space. After the Blackbird’s retirement the United States carried out most of its reconnaissance via satelite.

There are about 120 MiG-31s in service within the Russian Air Force today, though the tales of their exploits are not quite as exciting as they were during the Cold War. On April 26th, 2017, one was shot down over the Telembya proving ground in Buryatia in south-east Russia during a training exercise. Leaked documents showed that the Foxhound was shot down by an R-33 missile fired by another Russian -31 due to a radar and fire control malfunction. Thankfully, all pilots involved were able to eject safely, but it means that, throughout its operational history, the -31 was able to shoot down more fellow -31s than SR-71s, the plane it was built to defeat.

Variations and Upgrades

Like any plane that has been around for decades, the Foxhound has been subject to a handful of variations. Some of these variations were applied to new production batches, but the majority have been upgrades to pre-existing aircrafts. The most common variants include the 01DZ, B, BM, and BSM variants. These later variants are considered multi-role variations, as they have anti-radar, anti-ship, and air-to-surface missiles.

A project to upgrade the Russian fleet to the MiG-31BM standard began in 2010, and is expected to be completed sometime this year. The secretive nature of the Russian military makes it unclear just how many upgraded versions will be built, but estimates range from fifty to 130.

The -31BM includes upgraded avionics, new multimode radar, hands-on-throttle-and-stick (HOTAS) controls, LCD multi-function displays, a more powerful computer system, and digital data links. The upgraded radar can detect air targets up to 320 km (199 miles) away, and has the ability to prioritize them in order of potential threat. It also includes the ability to carry the R-77 missile, various Russian air-to-ground missiles, such as the Kh-31 anti-radiation missile, and the R-37, which is reported to travel at hypersonic speeds of Mach 6 and can strike targets over 300 km away.

What Does the Future Hold?

In 2015 the Russian Deputy Defense Minister Yury Borisov reported that the upgraded fleet would stay in service into the 2030s, meaning that the majority of the active fleet will have been flying for fifty years. However, it may not be much longer than that, as the Russian Armed Forces are reportedly working on a new and improved aircraft called the MiG-41. Rumors of the project began in 2014, when Russian test pilot Anatoly Kvochur spoke of the potential 6th generation interceptor. Kvochur stated that the plane in development would have a top speed of at least Mach 4, perhaps even reaching Mach 4.3, or 5,267 kmh (3,273 mph).

Progress on the -31s replacement is, of course, top secret, but most estimates place its first flight somewhere in the mid-2020s, likely after 2025. The design process was finalized in 2019, and the general director of the Mikoyan corporation, Ilya Tarasenko, has stated that the design will be reminiscent of the Foxhound, though it has also been influenced by the Su-57. Tarasenko also hinted at the inclusion of anti-satellite missiles and an anti-missile laser.

In the meantime, we can expect to continue to see the MiG-31 Foxhound as part of the Russian Air Force for at least another decade.

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