After becoming only the second country to field two fifth-generation fighter jets and flight-testing two sixth-generation fighter jets, China has reportedly crossed another threshold, flying a new, upgraded version of its J-20 stealth fighter with long-awaited high-thrust WS-15 engines and improved avionics.
With this, China has joined a group of elite countries that are capable of producing powerful engines for modern combat jets.
So far, only five countries have been able to produce engines for combat jets: the US (General Electric and Pratt & Whitney), the UK (Rolls-Royce), France (Safran), Russia (NPO Saturn and Klimov), and China (Aero Engine Corporation of China).
However, China’s new high-thrust WS-15 engine is in a league of its own and perhaps can only be compared to GE’s F135 engine, which powers the F-35 Lightning II stealth aircraft.
These high-thrust engines are capable of delivering sustained supersonic cruise without afterburner use, a key requirement for fifth-generation fighter jets.
The state-run media in China has released footage of flight tests of an upgraded J-20A stealth fighter, which is reportedly equipped with WS-15 engines.
The new footage was released by the Aviation Industry Corporation of China, the manufacturer of the J-20 stealth fighter.
According to a social media post by state news agency Xinhua, these aircraft are new prototypes of the J-20A, an upgraded version of the original J-20 stealth fighter.
The footage shows at least three J-20As in a yellow zinc-chromate primer. This is significant as in the Chinese aerospace industry, the coating means the aircraft is in the pre-delivery testing phase, with the primer applied to protect the airframe before the final application of stealth coatings.
Notably, this is not the first time that a J-20A equipped with the WS-15 engine has been spotted. Earlier in September last year, the J-20As were seen flight testing with the WS-15 engine.
Subsequently, in December, it was reported that the upgraded J-20A has entered serial production.
However, the latest footage suggests that the flight-testing is almost complete, and the aircraft is now in the pre-delivery testing phase.
Apart from the new, improved avionics, the more powerful WS-15 engine will provide the J-20A with more power and sustained supersonic cruise.
Commenting on the new engine, leading expert on the J-20 program Abraham Abrams observed in his recent book J-20 Mighty Dragon that the WS-15 boasts a “much higher thrust/weight ratio estimated at 10:1 or 11:1, requires less maintenance, improves thermal management properties, and has a significantly longer service life.
“Its cutting-edge single-crystal turbine blades, although proving particularly difficult to mass produce, were expected to almost double the engine’s lifespan compared to the WS-10B while significantly lowering maintenance needs.”
According to state broadcaster CCTV, the WS-15 can generate up to 18.5 tonnes of thrust – comparable to the F135 engine in the American F-35 fighter jet.
This high thrust allows it to sustain supersonic cruise flight without an afterburner.
Reportedly, the J-20A, equipped with the WS-15 engine, can reach 1.8 Mach, with a theoretical maximum speed between 2.5 and 2.8 Mach.
Incidentally, in its eight-year lifespan, the J-20 has flown with three different engine types.
The Three Engines For the J-20 Mighty Dragon
The J-20 is a twin-engine, stealthy heavy fighter jet that entered service in 2017.
Initially, the J-20 fighter jets used the Russian-made AL-31F engine. However, the engine did not generate enough power for true supersonic cruise, a primary requirement for fifth-generation fighter jets.
The Saturn AL-31F is a Russian afterburning turbofan engine primarily developed for the Sukhoi Su-27 “Flanker” family. It powers several fighter jets, with some using the exact AL-31F, while others use closely related derivatives such as AL-31FP (with thrust vectoring) or AL-31FN (adapted for single-engine use).
Russian fighter jets, such as the Su-30, Su-34, and Su-27, and Chinese fighter jets, such as the J-10 and J-11, use the AL-31 family of engines.
In 2019, the J-20 switched to the domestically produced WS-10C engine, but its thrust is thought to only allow for limited supersonic cruise.
In 2024, the J-20 was seen for the first time fitted with the WS-15 engine. The WS-15 can produce sustained supersonic cruise and is comparable to the most advanced fighter jet engines worldwide.
This is remarkable progress, given that China’s first combat jet engine, the WS-10, achieved design certification only two decades ago, in 2005.
From producing its first combat jet engine to producing a true fifth-generation jet engine within a span of two decades is a remarkable journey.
Notably, despite developing various fighter jets, many Chinese aircraft relied on Russian engines for decades.
This started to change with the introduction of the WS-10 engine in the early 2000s. Now that the WS-15 engine has matured, China can boast of one of the world’s most advanced fighter jet engines.
Fu Qianshao, a retired People’s Liberation Army Air Force colonel, said that if the engine were a WS-15, its thrust would “increase significantly”.
“Although fuel consumption will increase, it will be very beneficial for the J-20A to achieve supersonic cruise,” Fu told the Hong Kong-based South China Morning Post.
In addition to the new engine, the J-20A also features advanced avionics.
The J-20A shown in the footage also features a substantially raised dorsal spine behind the cockpit, dubbed the “fat-neck” J-20 by the observers.
Fu said the new design might have been meant to make room for improvements and adjustments to the avionics and electronic warfare systems. But he added that the wider fuselage would increase the aircraft’s air resistance.
“If the airframe design modifications are done well, the changes in air resistance won’t be too significant,” Fu said. “And if the new engines are replaced, this drag won’t have a major impact.
“Such modifications may also have allowed for the expansion of the dorsal fin behind the cockpit, enabling the aircraft to accommodate more avionics and fuel.”
According to a new research paper by the UK-based think tank Royal United Services Institute (RUSI), China could deploy as many as 1,000 J-20 heavy stealth fighter jets by 2030.
A significant number of these could be the upgraded J-20A fighters equipped with the WS-15 engines.
Separately, China could also use some upgraded version of this engine in its under-development sixth-generation fighter jets.
- Sumit Ahlawat has over a decade of experience in news media. He has worked with Press Trust of India, Times Now, Zee News, Economic Times, and Microsoft News. He holds a Master’s Degree in International Media and Modern History from the University of Sheffield, UK.
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