Powerful New Engines Take Flight on the Sukhoi Su-57

 - December 11, 2017, 1:39 PM
A prototype of the Sukhoi Su-57 fifth-generation fighter made its first flight with new, more powerful engines.

New and more powerful engines have been installed on the second prototype Sukhoi Su-57 fifth-generation fighter, which is also known by its Russian acronym PAKFA. The stealthy jet made its first flight with the new "Item 30" powerplants on December 5. The flight lasted for 17 minutes and was uneventful, according to Sukhoi chief test pilot Sergei Bogdan.

The Item 30 engine is described as a generation ahead of the AL-41FM1 that powers the other Su-57s. It provides about two tonnes more thrust at takeoff, at 17,000 kg (37,500 pounds) and therefore gives a notable boost to the Su-57’s thrust-to-weight ratio. Unlike the older practice of one design bureau heading the development process, the new engine is a joint effort of several specialized design houses and engineering teams at manufacturing plants, each taking work packages from the central office of the United Engine Corporation (Russian acronym ODK). Key companies taking part in the development effort for the Item 30 are UMPO in Ufa, Saturn in Rybinsk, and Salut in Moscow.

The Russian defense ministry previously agreed to launch development and limited production of the Su-57 with AL-41FM1 engines, because of the lack of a bona-fide next-generation engine more suitable to the airframe and its systems. Ten development prototypes of the Su-57 made their first flights between 2010 and 2014. The defense ministry has additionally ordered 12 production fighters. Deliveries will commence next year, and under current plans, the Russian air force expects two or three Su-57s by the end of 2018 and the rest in 2019.

But the AL-41FM1 has itself been described as a next-generation engine by the Rybinsk-based Saturn manufacturing company. Saturn (which took over the Moscow-based design house named after Arkhip Lyulka) developed the AL-41FM1 from the AL-31F that powers the Sukhoi Su-27/30/34 family of fighters, via the AL-41F, which never entered service. That larger engine, also known as "Item 20," was intended to power the Mikoyan Article 1.42/1.44 and Sukhoi Su-37. But it did not go into quantity production because both fighter types were shelved after short flight trials. The Russian air force opted instead for a lighter fighter, falling between the MiG-29 and Su-27 in size, for which the original AL-41F developing about 20,000 kg (44,000 pounds) was too big.

Compared with the AL-31F, the AL-41FM1 (also known as "Item 117") has an increased-diameter fan of 934 mm versus 905 mm (36.8 inches versus 35.6 inches) and runs at higher gas temperatures through the use of modern construction materials. It develops 14,500 kg (32,000 pounds) of thrust and weighs about 1,450 kg (3,200 pounds), whereas the AL-31F develops between 12,300 and 12,800 kg (27,000-28,000 pounds) of thrust and weighs about 1,500 kg (3,300 pounds)

Another version of the Item 117 engine, designated AL-41F1S, was selected for the Sukhoi Su-35S multirole fighter that entered service in 2014. The latter was accepted by the Russian air and space force as a transition type between the fourth and fifth generation of fighters. More than half of the nearly 100 Su-35s on order have now been delivered to the Russian air force.

How many Su-57s will be delivered with AL-41FM1 engines before production switches to the new Item 30 powerplants is not yet clear. ODK and UAC officials say that testing of the latter will take a couple of years.