New images have surfaced featuring Russia’s Sukhoi Su-57 Felon advanced fighter equipped with a new type of thrust-vectoring engine nozzle. The unique exhaust design aims to enhance the stealth capabilities of the Felon, though the future of this nozzle remains uncertain. The visuals showcase the rear view of the second flying prototype for the Su-57 program, T-50-2, which took its maiden flight in March 2011. This prototype was subsequently utilized to test the improved AL-51F-1 (also known as izdeliye 30) turbofan, which had its first flight in December 2017 with just one engine installed alongside the original AL-41F-1. The new flattened version of the nozzle seen on the left engine nacelle of the T-50-2 is intended to be incorporated into the AL-51F1 engine for the upgraded Su-57M variant. As of now, no orders have been placed for this aircraft model. The AL-51F-1 was developed as a completely new design to offer higher thrust, reduced weight, and lower operating costs compared to its predecessor, the AL-41F-1. Unlike the previous engine, the AL-51F-1 aims to provide the Su-57 with supercruise capabilities, allowing sustained flight above Mach 1.0 without using afterburners. The AL-41F-1, the original engine for the Su-57, along with its nozzle configuration, is also examined. Additionally, the nozzle design of the AL-41F-1 is compared with the Su-35 Flanker multirole fighter, which uses a simplified form of this turbofan. The AL-41F-1, also known as izdeliye 117, was created by upgrading the existing AL-31F engine found in earlier Su-27 and Su-30 Flanker series aircraft. The Su-57 and the Su-35 are equipped with the AL-41F-1 featuring a thrust-vectoring nozzle of axisymmetric type, providing pitch, yaw, and roll control. In contrast, the new AL-51F-1 retains a similar three-dimensional thrust vectoring nozzle, but the recent images reveal an alternative two-dimensional nozzle, offering pitch control and limited roll control if used asymmetrically. This type of stealthy ‘flat’ engine nozzle, found on aircraft like the F-22 Raptor, is chosen for its reduced radar signature compared to an axisymmetric design, as well as providing infrared signature advantages. The CEO of the Arkhip Lyulka Design Bureau, Yevgeny Marchukov, mentioned that Sukhoi initially did not consider a flat nozzle for the Su-57 program but later introduced the two-dimensional nozzle.
In a significant development for the aviation world, the Su-57 and AL-51F-1 aircrafts have been witness to a groundbreaking innovation with the introduction of a sophisticated flat nozzle. Explaining the rationale behind this pioneering design, Marchukov, a key figure in the project, emphasized the resistance to altering the airframe itself, prompting the need for a complex solution in the form of the flat nozzle.
The newly introduced nozzle boasts four independently controlled flaps, strategically designed to modify the air outlet cross-section and thrust vector. Notably, two of these flaps are tailored for optimal performance in subsonic conditions, while the remaining two are fine-tuned for supersonic flight. The innovative design also incorporates vectoring flaps that appear to be vented, a feature aimed at enhancing cooling of the exhaust and reducing the aircraft’s infrared signature by facilitating the flow of air through these areas.
Fast-forward to the summer of 2023 and Marchukov’s confirmation of successful ground testing of the new nozzle, including trials with afterburning, marks a significant milestone in the project. Anticipation is high for the impending maiden flight slated for before the year’s end, underscoring the industry’s eagerness to witness the practical application of this cutting-edge technology.
The implications of the flat nozzle for the Su-57 are nothing short of transformative, particularly in terms of enhancing the aircraft’s low observability from the rear aspect. While the original design of the Felon prioritized low observability from the frontal angle, the latest iteration aims to address shortcomings in side and rear-facing visibility, a critical aspect for stealth operations. Despite the anticipated reduction in thrust output associated with the revised nozzles, the consensus is clear – the benefits in terms of improved low-observable characteristics vastly outweigh any performance trade-offs.
Delving further into the realm of innovation, a parallel development in the form of a flat nozzle design for the AL-41F-1 engine, utilized in the Sukhoi S-70 Okhotnik uncrewed combat air vehicle, underscores the industry’s commitment to advancing stealth capabilities. Unlike its more sophisticated counterpart, this two-dimensional nozzle focuses on minimizing infrared and radar signatures without the added complexity of vectoring controls, catering to the distinct operational requirements of the Okhotnik.
The transition from a standard round nozzle to the revised flat design on the second aircraft of the Okhotnik fleet, unveiled in December 2021, signifies a pivotal moment in the evolution of stealth technology within the aviation sector. The narrative of progress continues with the prospective integration of the flat nozzle version of the AL-51F-1 into the proposed Su-57M, signaling a promising future for enhanced capabilities in the next generation of the Felon.
As the aviation landscape evolves with these cutting-edge advancements, the industry stands on the cusp of a new era marked by heightened stealth capabilities and improved operational efficiency. The pioneering spirit of innovation driving these developments underscores a commitment to pushing boundaries and
