Su-57’s 101KS-O Directional Infrared Counter Measures: how to make a virtue of necessity.

Su-57’s 101KS-O Directional Infrared Counter Measures how to make a virtue of necessity.

During the tests of the first prototypes of the American F-22, some of the characteristics that the international community of military analysts found more striking were without a doubt related to the Pratt & Whitney F119 engines. These engines were featuring some new, astonishing solutions to reduce the infrared trace of the aeroplane.


As a consequence, they made the F-22 more difficult to engage with short and medium-range IR anti-aircraft missiles and allowed this air superiority fighter not only to be considered stealth against radio emission systems (radars) but even against infra-red search and track turrets, devices that at the time (and now) were integrating the sensor suite of the principal Russian made modern fighter jets like the MiG-29 and Su-27/30. (stealth doesn’t mean that radars and IR sensors cannot track an F-22, but it means that its visibility is sensibly reduced, at least against the aeroplanes/SAM of early 2000) 

On the other hand, when the Su-57 made its first flight in 2010, many analysts remained surprised to notice that the engines that the aeroplane was used in its first flights were the same installed on the 4+ generation Su-35. They were not stealth against radars, not stealth against infrared missiles/tracking devices and they were not able to sustain a supercruise flight regime (when an aeroplane flights at supersonic speed without the need of using afterburners).

Russian MoD made clear that these engines were only intended to power the fighter during the state and industrial trials and that the new Idelyze 30 would have been the final engines of the plane. 

We recently had the opportunity to observe the first prototypes of Idelyze 30 and again, despite these engines are probably capable of archiving supercruise, they don’t seem to add any particular capability to the stealthiness of the fighter jet

Why the Su-57 is not mounting some F-22 like engines? The answer is very simple. Because Russia cannot field enough money to develop them. The research and testing of the Pratt & Whitney F119 engines was one of the most expensive chapters of the F-22 program and the Russian Federation simply cannot afford to spend that amount of resources to field similar engines. 

Nevertheless, has someone in mind the iconic legend of the “Soviet pencil in space?”. Well, as in this foctional anecdote, the Russians made a virtue out of necessity and compensated in a very particular way the inferior financial resources of the PAK-FA project. First of all, we have to say that the Sukhoi design bureau perfectly knew that the Russian financial capability is just a fraction of the one of the US (and even the US Air Force only purchased limited numbers of the F22). They decided to create a plane with a totally different technical philosophy and to compensate for the lack of know-how in certain fields (stealth engines) with the application of technologies they mastered since the soviet period. 

The IR trace of the Su-57 is not very different from the one of the Su-35, and in order to compensate this fact, the Russians decided to install, in turrets mounted on the dorsal spine and forward fuselage under the cockpit, a directional infrared countermeasure that is an evolution of the one used on some Russian military helicopters. 


Since the Afghan war, the Russians experienced the threat posed by MANPADs (portable anti-air missile), like the Stingers that the CIA was supplying to the Mujahedin in order to target the Russian attack and transport copters. Having suffered high casualties because of these systems, some Russian industries started to develop countermeasures and ended up creating the first laser-based solutions to “blind” the incoming infrared missiles. They developed this technology for more than 30 years (the new Kamov Ka-52 attack helicopter mounts one of the last version of this countermeasures) and when the Sukhoi design bureau had to outline the characteristics of the Su-57, they decided to compensate the lack of stealth engines with the application of new directional infrared countermeasure, capable of disturbing both surfaces to air and air to air infrared missiles. 

Unlike the Russians, most of the US-made fighters don’t have IR trackers to scout enemy planes using their infrared signature, and the only IR threat virtually posed to Russian aeroplanes concerns short-range missiles. Planes like the F-15, F-22, and F-35 will lock on the Su-57 with radar systems and then, fire an infrared missile if the enemy plane is engaged in a dogfight. 


Having acknowledged this fact, the designers of the PAK-FA decided that the plane could have been not stealth against infra-red seekers and relied on the already developed, helicopter-based, countermeasures against heat-seeking missiles. The capability to blind incoming IR missiles is unique to the Su-57 and complicates the tactics that western pilots will adapt to counter it. If the laser beam can effectively blind incoming short-range missile the Su-57 will have an enormous advantage in dogfights, even superior to the partial IR stealthiness of the F-22. 

The F-22 almost certainly is a superior aeroplane if compared to the Su-57, but the Russians know what they do (they had the possibility to study the F-22 capabilities before flying the first prototype of PAK-FA) and some technical characteristics of the new Sukhoi fighter jet (IR countermeasures, the combined sensor suite based on X and L band radars and heat-seeking sensors, EW systems) should not be underestimated. The SU-57 is dangerous because it is not a copy of the western fighters, but the Russian indigenous and original answer to modern air warfare.

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