The Chinese People's Liberation Army (PLA) Air Force displayed J-20s equipped with domestically developed engines at Airshow China 2021 in September 2021. This is the first time the J-20 has performed in public after it was fitted with domestically built engines. The switch to domestically made WS-10 engines from imported ones has made mass production possible, as other systems on the J-20, including the avionics system, radar system and weapons systems, were already domestically developed. Now that there is no limitation caused by the import of engines, and the homemade WS-10 engine has been tested on other aircraft like the J-10, J-11 and J-16, the J-20 is in a position to start mass production.
The domestically built engines can likely provide more powerful thrust to the J-20, which will help it in continued maneuvering in combat and also in supersonic cruise. With serrated nozzles, the new engines will improve the J-20's stealth capability, since such a design can reflect radar waves to some tight angles, and this will reduce the detection range of hostile radars on the J-20.
China has always been determined to improve the performance of domestic engines, and the performance of Chinese engines has always been far behind Western technology. At the Zhuhai Air Show, China exhibited its "J-20" fighter jets using domestically-made engines for the first time. The previous "J-20" fighter jets all used Russian engines. The chief designer of the "J-20" told the Chinese Communist Party's official media " Global Times " on 29 September 2021 that two other domestically-produced switches of the "J-20" are also being tested.
Initially the J-20 flew with two Russian AL-31F jet engines it borrowed from the Russian Su-27 fighter jet that entered Chinese service in the mid-1980s. China also tried to put engines of their own on a second test J-20 vehicle, but the copycat of the Soviet AL-31F enginemade by China is not in the same league as the Russian analog for reliability and durability. And both AL-31F and Chinese version are engines of the previous generation.
The AL-41F1 / 117S [117C in Cyrilic] engine is used on the Russian T-50 PAK-FA 5th Generation fighter jet. These engines enable it to achieve supersonic speed without afterburner. Rob Hewson at Jane's reported that Russia supplied 32,000-pound thrust 117S engines for the J-20, which would be adequate for an aircraft in the 80,000 pound class. But Russian sources reported in March 2012 that in 2010, when Russia’s Defense Minister Anatoly Serdyukov was on visit to China, Beijing proposed to buy 117S [117C in Cyrilic] engines, but the offer was turned down.
In March 2012 there were reports that Moscow and Beijing were close to striking a deal on China buying 48 Su-35 multifunctional fighter jets for $4 billion. The main reason for this remarkable purchase could be Russia’s jet engines. The Su-35 flies with two next generation AL-41F1C engines that enable it to achieve hypersonic speed without afterburner, a feature attributed to 5G jets. And AL-41F1C actually is a de-rated version of the AL-41F1 (117C) engine used on the T-50 PAK-FA, Russian 5G fighter jet.
The Russians agreed to sell only assembled planes and in addition insist on signing a special anti-copycat agreement, designed to prevent the Chinese from copying the vehicle and its parts, as has happened before. This demand became a stumbling block in the negotiations. Russia has great doubts concerning the practicability of selling AL-41F1C engines to Beijing without the special replication clause. This does not suit China because in the end they need technology to organize a production line for such engines of their own.
Before President Xi Jinping’s March 2013 visit to Russia and Africa, China and Russia signed two major contracts on the sale of arms. According to the contract, the two countries will jointly produce four Lada Class air-independent propulsion submarines which will then be sold to China. China will also buy 24 Su-35 jet fighters from Russia. Experts said that the Su-35 will reduce the pressure on China’s air-defense before China’s stealth fighter is put into use. This was the first time China had bought important military equipment from Russia in ten years.
Vasily Kashin from the Center for Analysis of Strategies and Technologies predicted in March 2012 that after long negotiations Moscow and Beijing would finally strike a separate jet engine deal and Russia would supply engines for the J-20 program, the way it already supplied engines to all four major types of Chinese fighter jets which are actually copycats of Soviet-made planes.
Most of the tactical and technical characteristics of the J-20 are still kept secret, but it was known that it had Russian AL-31FM2 engines installed. Beijing as a whole has achieved a significant breakthrough in the development of thrust vectoring engines, but was not yet ready to equip them with its newest J-20 fighters. "The WS-15 engine is still very unstable at work, and the engineers have not yet been able to identify the cause of the problem, although it has ample power," said one military expert in late 2018.
The development of turbojet engines of this type was carried out for several years, but they were far from perfect. Among the main drawbacks was the problem associated with overheating of turbine blades at high speeds. In September 2018, the Hong Kong edition of the South China Morning Post reported that these flaws of the WS-15 as a whole were eliminated, and thanks to this, China at the end of the year will be able to launch the mass production of J-20 fighter jets. "At present, China has about 12 J-20 units, which is far from meeting current needs," one source told the newspaper.
This aircraft was not initially complete. There were two major hidden dangers in the aircraft. The stealth of the rear is not good, and the infrared stealth is not enough. In fact, both originate from an important component: the engine. Due to the weak foundation of China's aero engine, the fourth-generation military engine turbofan-15 with a 16-17 ton thrust-to-weight ratio of 10 had been difficult to produce, so the Air Force had to use imported engines. In 2019, the J-20 fighter has a huge breakthrough: the engine uses a zigzag design nozzle, which will be the beginning of the J-20 to solve these problems.
This sawtooth engine is an improved version of China's Taihang engine, with an afterburning thrust of 14 tons, which is comparable to the thrust of the Russian-made engine used during the J-20 test flight, and most importantly, this is China's first engine with stealth function. Although the thrust is not enough, it has begun to prove that the Chinese J-20 is gradually perfecting, and the two shortcomings of insufficient engine thrust and hidden defects have gradually grown stronger.
The biggest feature of this engine is that it uses a sawtooth tail nozzle. This design has two advantages. On the one hand, it can increase the contact perimeter of the high-temperature jet and quickly reduce the jet temperature. The American F-35 fighter also uses this. This design, with an increased bypass ratio design, can reduce 80% -90% of infrared radiation, extremely weaken the detection of enemy infrared detectors, and greatly improve the survivability of enemy infrared missiles.
In addition, this serrated nozzle also eliminates the specular reflection of the nozzle blades of the early engines. This is the largest stealth shortboard of the J-20 fighter. It has not been treated, and the effect is similar to that of the third-generation aircraft. The tail of the current J-20 fighter It is completely invisible. This weakness brings a lot of trouble to pilots in combat, and special tactics are required to avoid exposure.
Now there is still a problem. In addition to the specular reflection of the fish scales in the stealth of the engine, the afterburner and turbine blades at the rear of the engine also form multilayer angular reflections with the engine casing. Similar to the Long Wave lens principle, the tail is incident on the original electromagnetic wave. The road returns, so it must also be specially modified. The F-35 fighter aircraft is completely covered by a stealth grille.
J-20s in service with the People's Liberation Army (PLA) Air Force initially all used circular nozzles with no thrust vector control capability. Thrust vector control provides extra maneuverability and 2D nozzles can enhance stealth capabilities of the J-20. It has been long expected that the J-20 will eventually receive thrust vectoring-capable engines. The 2D nozzles are rectangular and 3D nozzles are circular, meaning that 2D nozzles have better radar and infrared stealth capabilities than the 3D nozzles. The F-22 stealth fighter jet of the US Air Force uses 2D thrust vectoring. The 3D nozzles are often believed to be capable of providing more thrust angles than 2D nozzles, as F-22's 2D nozzles can only move vertically, but this is a common misunderstanding, as 2D nozzles can also move horizontally to provide horizontal thrust when so designed, but this design could add development costs.
With the flight performance of the J-10B thrust vector control demonstrator at the Airshow China 2018 in Zhuhai, South China's Guangdong Province, China displayed its capability to develop and apply 3D thrust vectoring technology on fighter jets. When asked about when the J-20 can get thrust vectoring-capable engines at a press conference of Airshow China 2018, shortly after the J-10B thrust vector control demonstrator made its flight performance, Yang Wei, chief designer of the J-20, replied, "You asked about when, but how do you know it hasn't?" This statement is widely interpreted by military observers that the J-20's developers have been testing thrust vector control on the aircraft for a long time.
The pilot who first flew the J-20 believes that China's most advanced stealth fighter jet will be upgraded with 2D thrust vectoring nozzles for its engines, according to a news report 19 April 2021. This means the warplane will receive enhanced maneuverability and stealth capability and surpass its US counterpart, the F-22, a Chinese military expert said. The J-20 is expected to be equipped with engines with 2D thrust vectoring nozzles, said Li Gang, the pilot of the J-20's first flight, when asked about his expectations on the future development of the J-20's thrust vector control capability in an interview with Hong Kong-based Phoenix TV. Li also said that he expects the J-20's thrust vectoring nozzles to move only vertically like the F-22, but Fu Qianshao, a Chinese military aviation expert, said that he hopes the J-20's future nozzles will be able to move horizontally, which will make the PLA fighter jet surpass its US counterpart in this aspect.
The Chinese People's Liberation Army (PLA) Air Force has equipped a second ace force with the country's most advanced fighter jet, the J-20, as the unit made its debut with the new warplanes in Northeast China on 18 June 2021. Report footage shows that these J-20s are equipped with domestically developed engines. Observers pointed out that the J-20s featured in the report footages are seemingly equipped with domestically developed WS-10 engines.
This is not the first time the PLA Air Force has confirmed that a J-20 equipped with a domestically made engine has entered service. Back in January 2021, the PLA Air Force released a video for its pilot recruitment program, and media outlets identified a J-20 that is equipped with domestically developed WS-10C engines instead of imported Russian engines.
More J-20s entering service with the PLA Air Force and their equipment of domestically developed engines indicate that the J-20 is becoming more and more technically mature and has started mass production.
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