From the Patent Doc. :
МНОГОФУНКЦИОНАЛЬНЫЙ ДВУХМЕСТНЫЙ МАЛОЗАМЕТНЫЙ САМОЛЕТ
MULTI-PURPOSE TWO-SEAT STEALTH AIRCRAFT
The possibility of using a two-seater multifunctional aircraft as an
airborne command post, with the ability to ensure interaction between aviation and military formations in solving combat missions, analyzing information received from its own systems and external information sources with the subsequent issuance of recommendations to the crew and commands to the group's aircraft, as well as a control post for unmanned aerial vehicles, is achieved through a wide range of communication means, including satellite communications, equipment for group transmission of information, equipment for transmitting information over long distances and a high-speed communication channel for receiving and transmitting audio, photo, video, text, voice and telecode information and a specialized command and information field of the rear cockpit (which, in comparison with the front cockpit, has the following differences: an expanded panoramic aviation indicator and an additional indicator for increasing the operator's working field, controls are installed to transfer control priority from one cockpit to another and also excludes control bodies that do not require control by a second crew member), which makes it possible to promptly receive information from various external sources (both aviation and land and sea), analyze it on board the aircraft and issue recommendations or commands to perform a combat mission to the group's aircraft, taking into account their fuel reserves and combat equipment.
The increase in range and flight duration is achieved by increasing the fuel tanks by 10% compared to the prototype with a change in the geometric contours of the airframe, due to the placement of the second crew member as well as when placing fuel tanks in the cargo compartments of an aircraft.
( If I remember well ,there was some news about the additional fuel tanks which can be attached inside of the two FWC's ? )
The aircraft's communications suite enables communication between subscribers using a wide range of communication modes, operating in both open and encrypted modes. The multifunctional two-seat aircraft's communications suite operates in the following bands and modes:
- centimeter wavelengths - for transmitting photos and video images;
- shortwave wavelengths - for transmitting voice information over long distances;
- ultra-shortwave wavelengths - for transmitting voice and telecode information in air-to-air mode;
- using a group action terminal - for group transmission of voice and telecode information between subscribers of a group of aircraft;
- using satellite space communications - for transmitting voice and telecode information via satellites.
The availability of these operating modes for the communications system allows the multifunctional two-seater aircraft to command a group of different types of aircraft (both manned and unmanned) to ensure flexibility in combat use when solving airborne command post tasks in any weather conditions and when jammed by the enemy.
https://fips.ru/cdfi/fips.dll/ru?ty=29&docid=2807624
About the comm complex of the Su-57 ,there is some interesting data from 2018 :
Некоторые характеристики комплекса средств связи (КСС) С-111 самолёта Су-57
Some characteristics of the S-111 communications system (CS) of the Su-57 aircraft
https://ak-12.livejournal.com/91286.html
https://cyberleninka.ru/article/n/p...iya-aviatsiey-putem-adaptatsii-kanalov/viewer
Translation of the complete 'Patent Doc' and this article would require more time but with the help of others,we can have complete material in English.Then we will better understand tactical and technical requirements for the dual-seater by the VKS.