The recent Twitter videos posted by various Chinese Twitter accounts showing J-35 taking off from a deck with its WS-19 engine may attract military enthusiasts without aerospace knowledge.
Here are the facts about the Chinese J-35 and J-20, and their technology.
Chinese engineers thought that if an aircraft looks like an American aircraft, it will magically become a fifth-generation aircraft without the actual technology, engine, sensors, or manufacturing techniques.
China’s J-35 and J-20s may appear stealthy outside, but if you look closely at the airframe, it’s not the radar-absorbent material, but automobile spray paint all over the airframe to cover up industrial screws used to fasten the airframe.
Technicians are walking all over the airframe and removing parts with automotive power tools, indicating China didn’t use baked-mesh carbon fibre technology to reduce radar cross-section.
Lockheed Martin developed specialised manufacturing tools and techniques before manufacturing any stealth aircraft, whereas China imports machining tools and commercial manufacturing equipment from Europe to produce military products identical to those of Chinese-made counterfeit products you see on Chinese e-commerce websites.
Reverse-engineering efforts by China
China has engaged in long-term efforts to reverse-engineer Russian AL-31F engines to power its indigenous fighter fleet, including the J-10, J-11B, J-16, and initially the J-20. These efforts led to the development of the WS-10 Taihang engine, which, after overcoming early reliability issues, now powers many Chinese aircraft, reducing reliance on Russian imports.
Initial attempts to copy Pratt & Whitney PW1120 engine through Israeli Lavi fighter jet technology acquisition from Israel completely failed as Pratt & Whitney PW1120 engine was too compact and China didn’t have the industrial capability to produce any combat engine, so China abandoned the project.
China’s reverse-engineering of Russian Al-31 engines in the 1990s and 2000s resulted in unreliable performance, a short lifespan, and engine oil leaks, which led to an explosion during testing of the WS-10A in the J-10B fighter jet.
The Shenyang WS-10 is widely considered to be a reverse-engineered engine from the Saturn AL-31, and it has gradually replaced the Russian engines in J-11B and J-16 fighters, but the time between overhauls has become a critical issue as the engine lasts only 400 hours, and some of the WS-10A and WS-10B engine blades were damaged due to heat and oil leaks.
Russian AL-31 vs. AL-41
While the WS-10 was designed to replace the AL-31, China also sought the more advanced AL-41F engines from Su-35 aircraft to enhance its reverse-engineering efforts, with questions about the success of copying the newer technology.
The successful, albeit slow, development of the WS-10 has allowed China to move toward self-sufficiency in engines, reducing the need for foreign, particularly Russian, technology in its domestic fighter aircraft.
China continues to develop its engine technology, aiming to replace older engines with indigenous alternatives like the WS-15 for the J-20 and WS-19 for J-35, but engine performance remains questionable and thrust-to-weight limits fighter jets’ capability to carry payloads for combat.
WS-19 “Huangshan” engines
The Shenyang J-35, equipped with WS-19 “Huangshan” engines, has been noted for having a lower thrust-to-weight ratio than some of its competitors (such as the F-35 or even the fourth-generation F-16), which can lead to slower acceleration and reduced climb performance.
After spending more than $20 billion on engine development, the Chinese turbofan development and manufacturing so far can only be compared with the old Soviet-era RD-33MK standard still used in MiG-29 and its derivatives. Let me elaborate to you.
Recent performance statistics of the Chinese WS-19 turbofan engine, leaked to the media, show that the WS-19 can sustain less than 3 minutes with afterburner and a maximum of 7 minutes of air combat after taking off from the deck. This performance data demonstrates that, due to its sluggish WS-19 engine, a low thrust-to-weight ratio, and heavy onboard fuel consumption.
The WS-19 is a medium-thrust engine, with newer versions (sometimes referred to as WS-21) estimated to produce less than 80 kN of thrust with afterburner.
The J-35’s thrust-to-weight ratio at maximum take-off weight (MTOW) is estimated at approximately 0.54, which is significantly lower than the F-35’s 1.07.
The WS-13 and WS-19 are the Chinese versions of the Saturn AL-31 China, reverse-engineered from the early Su-27 or Su-30MKK acquired from Russia. Still, their performance parameters are similar to those of the Russian RD-33 engine.
With structural changes and external casing changes, China modified the WS-13 variant and called it WS-19 or WS-21 for use in J-35 deck-based fighter jets. China started another project ten years ago to copy an older version of the F404 engine, the WS-12, and later tried to sell it to Pakistan as the WS-13E for the JF-17 fighter jet.
While China did not fully master the manufacturing techniques for superalloy or heat-resistant turbofan blades and nozzles, it, as usual, Chinese propaganda mouthpiece Global Times claimed the WS-21’s performance as Comparable to that of the EJ-200. I am sure Pakistan will get caught with this engine problem, as they did with the J-10C fighter jet’s WS-10A engine.
According to current information, the J-35A that participated in the military parade on September 3rd is equipped with the new WS-19. As for why the navy variant of J-35 is not yet equipped with the WS-19, it may be due to limited initial production output or because the naval version is still undergoing testing.
Due to these engine limitations, the J-35 may experience slower acceleration and a limited sustained supersonic dash. The top speed is reported to be around Mach 1.6, but based on engine performance, the actual speed could be less than Mach 1.2 due to the heavier steel airframe.
Despite these potential performance bottlenecks, the J-35 is designed as a carrier-based fighter, focusing on the immediate needs of the Chinese Navy rather than a mature product optimised for structural strength, stealth, and payload capacity.
While early versions of the J-31, J-35 and J-20 used older engines (such as the WS-13), the current WS-19 or WS-21 is restructured and redesigned, with a new casing that retains the engine core.
China is also working on a reverse-engineering project of the second-stage product 30 or AL-51F1 engine, with a flat nozzle and deflectable thrust vector, sourced from a Russian manufacturer.
Most notably, the Chinese propaganda army is copying Wikipedia datasheet from European and American military products and advertising as China’s own product performance datasheet to sell their second-grade arms to Pakistan, Myanmar, Venezuela, Thailand, Cambodia, Bangladesh or Nigeria; their actual performance is getting exposed in actual combat, either the Thai-Cambodia border skirmish or the Indo-Pakistan border skirmish, in Nigeria or in Venezuela.
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