In recent weeks both Russia and the People’s Republic of China (PRC) announced that their fifth-generation fighter programs had advanced in their steps to enter service. The two aircraft—the Sukhoi Su-57 and the Chengdu J-20—have been flying for several years and have completed programs of test and validation schedules. However, both platforms are still lacking series production, next-generation engines and other on-board sub-systems that would make them complete fifth-generation aircraft.
At present all Su-57 aircraft are powered by the Saturn/Lyulka 117/AL-41F-1-series engine that is also installed in the previous-generation Su-35. The aircraft’s new-generation Izdeliye-30 engine was test flown only in December 2017. The J-20 is supposed to receive a new Chinese-made WS-15 engine, but for now the engines in different versions of the aircraft seen to date are variants of the Shenyang Liming Aero-Engine Group WS-10A that is installed in the Shenyang J-11B, or a Russian-made Salyut AL-31FM2/3 variant.
Russia’s Deputy Minister for Defence, Yuri Borisov, announced on February 8 that the Su-57 has “completed the first stage of flight test operations.” This step signifies that the aircraft has entered the final testing phase before being introduced into service. Development aircraft made a brief operational evaluation deployment to Syria in late February. Borisov also stated that the Russian Aerospace Force (VKS) would sign a contract this year to “commit to the first squadron of 12 aircraft,” and that two initial aircraft from this contract will enter service in 2019.
One day later, on February 9, the People’s Liberation Army Air Force (PLAAF) declared that its J-20 had completed all testing and had been commissioned into combat service. “It marks an important step for the J-20 to have comprehensive combat capabilities,” announced Shen Jinke, a spokesman for the PLAAF. “The stealth jets will improve the air force’s comprehensive fighting ability and enable it to better safeguard China's sovereignty, security, and territorial integrity.”
The induction of a true fifth-generation Su-57 into service with the VKS is still some time off in the future. During a visit by Borisov to the Komsomolsk-na-Amur plant (KNAAPO) that produces the aircraft, he was asked what the December 2017 test flight of the Izdeliye-30 fifth-generation engine that was installed in one of the two nacelles of Su-57 prototype number T-50-2 means for the program’s schedule. “For now it is difficult to judge, because all we have had is this one flight,” he said. “Thus far everything is normal, but you all understand that to complete a testing regime it is necessary to fly for a lengthy period of time. The general rule is for testing such as this to take place over two to three years.”
This would seem to put the Russian aircraft months, if not years, behind the J-20 in officially entering service, but the Chengdu aircraft seems to be operational in name only at this point. There are only eight of the J-20 prototypes flying, along with 20 or more “operational” aircraft. Analysts of the PRC’s defense industry also point out that there is a previous history of fighter aircraft being declared operational, but in reality they remain tethered to the production plant, as was the case with the Chengdu J-10.
Sources that spoke to AIN in Singapore also confirmed previous news reports that the J-20 has a substantial logistics tail in the form of specialized, climate-controlled hangars that maintain the aircraft at constant temperature and humidity levels. Extended exposure to the elements reportedly degrades the RCS reduction properties of the aircraft. “The number of these hangars and the process of constructing them is a limiting factor in the deployment of these aircraft,” reported one PRC aircraft analyst.
The WS-15 engine that is designed for the J-20 is not projected to be available before 2019. Until this time, the aircraft does not have an engine with the thrust levels required for it to achieve its specified performance, including the ability to supercruise. If the J-20 follows a similar path to that of the J-10, the introduction of a new, non-Russian engine will require a significant redesign of the inlet and the rear fuselage.