Next mass-produced Su-57 Felons will be with second-stage engines

A report from TASS, a state news agency in Russia, quotes an insider saying that in 2023, the Russian Aerospace Forces, also known as VKS or RuAF, received a fleet of ten Su-57 fighters. These aircraft are powered by stage one engines. 

Russia will unveil the export Sukhoi Su-57E fighter in India
Photo credit: Rosoboronexport

The insider further mentions that beginning in 2024, all Su-57s rolling off the production line will boast stage two engines, often referred to by their code name “Izdelie 30”. This engine has been under development and rigorous testing for the past three years. Initially, the engine was dubbed AL-51 and subsequently had an updated version, the AL-51-F1. 

The same source suggests that the Su-57 fighter jets already in the Air Force’s possession won’t be subject to engine upgrades. Instead, they will continue using the current, in-service engine version. Justifying this, the source states, “The second stage engine has undergone extensive testing and is operation-ready. There are no plans to replace the first stage engines of the Su-57s currently utilized by VKS with this new engine,” as quoted in TASS.

Second stage engine known as Izdeliye 30 is fitted to the Su-57
Photo credit: Facebook

Engine already tested

Rostec, the state corporation, officially confirmed that testing has been completed on the second stage engine as the year came to a close. 

The AL-51-F1 is an intricate mechanism – a two-shaft, low-bypass afterburning turbofan engine, to be precise. This engine is built on a detailed architecture that includes a three-stage fan propelled by a solitary-stage low-pressure turbine. In addition, a five-stage high-pressure compressor that’s driven by a singular high-pressure turbine forms a crucial part of its design. 

Second stage engine known as Izdeliye 30 is fitted to the Su-57
Photo credit: Twitter

The AL-51-F1 makes remarkable improvements on its predecessor, the AL-41F1. This innovative engine incorporates glass-fiber plastic IGVs and nozzles that seamlessly converge and diverge. These nozzles employ serrated flaps that effectively minimize their radar signature. The engine boasts impressive efficiency, with a 19% boost in thrust-to-weight ratio, a 6.4% increase in specific thrust, and a 9% reduction in specific fuel consumption. When it comes to estimated thrust, we’re talking about 107.9 kN [24,300 lbf] dry and a whopping 166.8 kN [37,500 lbf] in afterburner. Furthermore, the AL-51-F1 employs full authority digital engine control [FADEC] to ensure top-notch reliability under a variety of operating conditions.

Flat nozzles

In 2023, intriguing updates surfaced regarding modifications to the structural design of a “newly tested engine” installed in the Su-57. These unexpected alterations are likely the final touches to the Al-51 engine, involving the introduction of flat nozzles – a feature not widely embraced in Russia. This novel design has, however, grown in global popularity following its implementation in the F-22. 

Russian Su-57 Felon has begun tests of new engine flat nozzles
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As for the flat-nozzle engine, numerous news outlets refer to a slide from the United Engine Corporation [UEC] presentation. This slide indicates that the “6th generation NTRP engine” development includes not only the progress on flat-nozzle technology, but also the invention of high-performance bearings, “ceramic turbine” components, and sophisticated electrical systems. 

Beyond that, the development of a three-circuit engine power plant is also in the works, which promises a substantial improvement of up to 12.5% in subsonic fuel efficiency.

Stealth advantage

The use of flat nozzles in cutting-edge fifth-generation stealth fighter jets provides a whole host of advantages above and beyond conventional nozzles. The most notable of these advantages is their ability to seemingly ‘disappear’ from infrared sensors. This is due to the flat nozzle’s unique structure. With it, hot exhaust gases are spread more evenly in comparison with cooler air, reducing the temperature of said exhaust gases and, in turn, their visibility to infrared sensors. It’s a key feature that enhances the stealth characteristics of these aircraft, increasing their ability to slip undetected past enemy lines. 

Furthermore, it’s not just stealth that flat nozzles majorly benefit; they also greatly improve how the pilot can control the directionality of the exhaust gas flow. This precision in airflow control effectively magnifies aircraft maneuverability while shrinking its radar cross-section. Beyond this, there’s also a bonus in fuel efficiency. Thanks to the nozzle’s structure, the exhaust gases can expand more efficiently, producing an increased amount of thrust and leading to fewer stops for refueling. 

But let’s not forget about durability and reliability—two areas where flat nozzles excel. Keeping the nozzle walls stress-free is a priority and the design of these flat nozzles does just that, curbing the risk of damage such as cracking or deformation. This means increased lifespan and reduced maintenance. In all, flat nozzles simply prove themselves superior time and time again.

Photo credit: Wikipedia

Sukhoi Su-57 Felon

Developed by Sukhoi, the Sukhoi Su-57 is a standout twin-engine stealth multirole fighter aircraft. It represents the pinnacle of the PAK FA program, which started in 1999 with the explicit purpose of providing a contemporary and more cost-effective counterpart to the MFI [Mikoyan Project 1.44/1.42]. 

The aircraft is internally classified as T-50 by Sukhoi. As the prime example of a stealth technology aircraft in Russian military service, the Su-57 is set to lay the groundwork for a new generation of stealth combat aircraft. 

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Photo credit: Wikipedia

As a 5th-generation multirole fighter, the Su-57 exhibits versatility in its capability to undertake aerial combat, ground attacks, and maritime strikes. Key features include its stealth structure, extraordinary maneuverability, ability to supercruise, integrated avionics system, and extensive internal payload capacity. 

The Su-57 is seen as the future, predicted to supersede the MiG-29 and Su-27 in Russian military service. Simultaneously, it continues to be a hot prospect globally, marketed for export. The maiden flight of the first prototype aircraft was in 2010. However, the program’s progress was slower than anticipated due to several structural and technical challenges that emerged during trials. Additionally, the initial production aircraft suffered a crash before its delivery, adding further delay to the program.


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