China’s J-20 Gets Another Upgrade

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China’s J-20 Gets Another Upgrade

Updates on the 5th-gen fighter’s WS-15 engine, new variants, and fleet size, and what it all means for the future of China’s fighter fleet.

China’s J-20 Gets Another Upgrade

A J-20 fighter appears at the 2022 Changchun Air Show. Recent images have shown a new variant of the fighter.

Credit: Wikimedia Commons/N509FZ

On June 29, a new J-20 prototype with the serial number 2052 made its first flight at Chengdu Aircraft Corporation in China, newly powered by two WS-15 turbofan engines. This event was a major milestone for the WS-15 engine, a carefully guarded project whose rumors and hints of development had been carefully followed for the last decade and a half – ever since rumors of the J-20 (then known only as J-XX) began in the mid to late 2000s. 

The maiden flight of a J-20 airframe with two WS-15 engines marks a major developmental step toward entry into service, and occurred after progressing through a preceding development, testing, and testbed flight campaign. Furthermore, the specific J-20 airframe in this case is a major new variant of the J-20 with its own external changes, as well as upgrades and new capabilities. 

Recent indicators, images, and rumors over the past year have also caused a significant upwards revision for in-service J-20 fleet size as well as an acceleration of J-20 production rate, which has significantly changed projections of how the People’s Liberation Army Air Force (PLAAF) combat aircraft procurement may occur over the coming decade and beyond. The WS-15 progressing to maturity, a new upgraded J-20 variant, and increased J-20 production rates also have influence for the upcoming PLA sixth-generation fighter project. This article will summarize the background and recent developments on these fronts, and explore the implications for the J-20 and beyond.

The WS-15: Background and Significance

The WS-15, also known as Emei, is the primary powerplant that the J-20 was always intended to field. However, as the state of the Chinese aeroengine industry was significantly behind the rest of its aerospace industry, it was decided that the J-20 would initially enter testing and service with an interim engine until the WS-15 was ready. The interim engine for the J-20 was initially the Russian Al-31, but it was replaced with the domestic WS-10C in production in 2019. 

The WS-15 provides higher thrust than the interim engines, and among other features will enable the J-20 to achieve even more impressive kinematic performance than it presently has. It will also enable consistent and true supercruise (supersonic speed without afterburners), further augmenting the aircraft’s capability in its general air superiority role

The exact development trajectory of the WS-15 is not currently known because of careful PLA operational security. However, it is known that the WS-15 as a project only commenced in 2006, rather than in the 1990s as a number of English language outlets have claimed. In fact, the WS-15 commenced pre-development and demonstrator work prior to 2006, from the 1990s to the 2000s, and confusion of pre-development work and project commencement may have resulted in repeated signal boosting of inaccurate information. 

However, it has been rumored that the WS-15’s development from 2006 underwent a period of delay, partly associated with revised and enhanced requirements because of technological and industry advancements in the 2010s. Despite the claims of some outlets, there is no evidence that the WS-15 was intended for high-profile public appearances at the Zhuhai airshow in past years, nor is it indicated that supposed explosions during its development occurred in the 2010s.

Reliable parameters of the WS-15’s performance and technical details are not known, but one notable specification known with some confidence is that the engine will feature a thrust to weight ratio of between 10 to 11. Its thrust range, bypass ratio, stages, and temperatures cannot yet be stated with any confidence. Other performance goals such as mean time between overhaul and failure or specific fuel consumption are also unknown; however, it is likely that overhaul and failure times are anticipated to be at least as capable as the most recent WS-10 variants, if not better, resulting from China’s significantly more mature aeroengine industry. That is likely to produce a much smoother development timeline as well.

As of this writing, there are no clear definitive pictures of the WS-15 engines flown on the J-20 prototype 2052. However, blurry videos have displayed both a notable shortened takeoff run than previous J-20s powered by the Al-31 or the WS-10, as well as a distinctly lower sound. Most importantly however, is the unanimous consensus by various Chinese language PLA watching individuals with reliable track records that the prototype aircraft had flown with two WS-15s. 

In addition to enhancing kinematic performance and enabling consistent supercruise, the WS-15 will also significantly enhance electrical power generation, enhance thermal management properties, and provide much greater long-term growth potential and redundancy. These features are important, as J-20 prototype 2052 is an example of a significantly enhanced J-20 variant that will feature major upgrades to subsystems and materials as well as displaying external changes. The prototype is anticipated to be the new mass-produced single-seat J-20 variant in the near future, powered by the WS-15. 

One notable feature not observed on the WS-15s seen on serial 2052, is thrust vectoring nozzles; however, they are expected to be installed on a future prototype powered by WS-15s. One explanation for its present omission is that the subsystem upgrades and new WS-15s already amount to significant enhancements, and thrust vector control would be an additional factor to test and verify on an already heavily upgraded airframe. Into the more distant future, it is likely that the WS-15 will see further upgrades and iterations, potentially including variants that will power the PLA’s sixth-generation fighter program.

An image of J-20 prototype 2052, as shared by PLA watchers on Weibo.

New J-20 Variants

J-20 prototype serial 2052 was preceded by prototype serial 2051, which was first seen in December 2022. These two airframes are both prototypes for a new upgraded single seat variant. However, serial 2051 was powered by two WS-10C engines rather than two WS-15s, likely reflecting the PLA’s preference for iterative development. 

This new variant of J-20 was initially dubbed the “J-20B,” with the assumption that the existing single-seat variant powered by the Al-31 and WS-10C was the “J-20A.” However, recent images taken of a ceremonial banner at the event suggest that serials 2051 and 2052 are actually the “J-20A” instead. The “J-20A” has been described as the “complete” version, whereas the existing single-seat variant powered by Al-31s and WS-10Cs was merely the “J-20.”

Revisions of publicly applied designations are not new for PLA watchers (such as the 001A to 002, and 002 to 003 change for the PLA Navy’s aircraft carriers). This article will abide by the new revised designation system, with an understanding that the naming system may yet still fluctuate.

The J-20A can be differentiated from the J-20 by the presence of a distinctive raised dorsal hump behind the cockpit, as well as a slightly revised nose radome geometry. Minor changes to the air intake may also be present but are yet to be confirmed due to a lack of high-quality imagery. The purpose of the dorsal hump is unknown, but it is similar in geometry to the J-XY/35 carrier-based fifth-generation fighter, which has been stated to have aerodynamic benefits, though it may also provide additional space for avionics, fuel, or both. 

The bulk of the J-20A’s enhancements from the J-20 are not visible externally, as they are upgrades to the aircraft’s sensors, avionics, materials, and enhanced growth potential, in addition to the WS-15 engines that will power it. The extent of enhancements of the J-20A are so significant that at least one notable Chinese language insider suggested it may in the future contend as a “5.5th” generation aircraft or at least serve as an intermediary aircraft between the fifth generation and sixth generation. Existing in-service J-20s, however, have also seen meaningful upgrades to subsystems and signature reduction, such that newer batches of J-20s are notably more capable when facing earlier batches of J-20 in aerial confrontation exercises, despite software upgrades across the fleet.

This characterization of the J-20A also dovetailed with new information for the twin-seat J-20, which first flew in late 2021. There is no current confirmed designation for the twin-seat J-20, but the “J-20S” and “J-20AS” have been used in the past, including by this author. With recent updated information the name “J-20B” has been used, which could be appropriate as the twin-seat variant is not merely a J-20 with a tandem cockpit, but rather features significant next-generation technologies and demonstration purposes, including for enhanced command of unmanned aerial vehicles (UAVs). In fact, the development and testing of the J-20B is stated to have helped expedite the development of the J-20A, such that one comparison portrayed the new J-20A almost a single seat derivative of the J-20B. 

However, at present it is unclear if the PLA will procure a version of the J-20B for service, as it has also been suggested it is a largely self-funded technology demonstration project by Chengdu Aircraft Corporation itself without an explicit PLA tender. There may be potential benefits of a production version of the twin seat J-20B, but procurement will ultimately depend on PLA priorities. 

It is not yet known when the J-20A will enter service, and is likely to await the conclusion of WS-15 flight testing as well as readiness for large-scale production of the new engine. Presently, I tentatively believe that  J-20As with WS-15s are unlikely to enter service before 2025, though the possibility of the J-20A entering service with WS-10 family engines cannot be ruled out if the WS-15 experiences delays during its flight testing.

J-20 Fleet Size and Future

New engines and upgraded variants with new technology only hold as much potential as the number of aircraft that are produced. In that respect, indicators and imagery evidence over the last year have resulted in a significant reassessment of both contemporary J-20 fleet size and production rates and potential. During Zhuhai Air Show 2022, serial number cross examination suggested that total fleet size had already exceeded 208 airframes by November 2022. However, later imagery in the year demonstrated that production serials utilized a different counting method, causing a minor revision of total fleet size to an estimate of 170-180 airframes produced by the end of 2022. Recent credible rumors in late June of this year stated more explicitly that J-20 production had already exceeded that of the United States’ F-22 (187 airframes), which was once predicted in past years as something that would not occur before the year 2027. The PLA apparently met that mark with four years to spare. 

A rise in J-20 production capacity and production rate has also been rumored over the last year, with expectations that annual J-20 production rate may approach 100 aircraft per year by the end of 2023, and comfortably meet 100 per year in 2024. Retrospective estimates for 2022 based on examining service serials and production serials, cross examined with credible rumors, suggest that around 70 J-20s may have been delivered that year. Thus, as of early July, the number of J-20s that have been produced is estimated to be anywhere between 200 to 250 aircraft, with more airframes to be delivered in the second half of 2023. 

It is not known if annual J-20 production rates will further grow, as the Chengdu factory appears to have ongoing expansion work that may support additional production capacity. Nevertheless, even if the J-20 production rate “only” sustains itself at 100 aircraft per year, it is likely the total J-20 production run across all variants will run through to the high hundreds, and perhaps approach 1,000 airframes if production continues into the early 2030s. 

A large production run of J-20 family aircraft has also altered past expectations of a land-based variant of the J-XY/35 medium weight fifth-generation fighter. Presently, it is unclear if such a variant is still being pursued; indeed news on this front has been remarkably silent since late 2021. Emerging air-to-air unmanned combat aerial vehicle (UCAV) platforms and advancements in UCAV control may well make a land-based J-XY/35 a suboptimal procurement choice for the PLAAF of this era.

By contrast, the PLAAF’s commitment to a sixth-generation fighter capability has been reinforced by recent credible rumors, suggesting a goal to accelerate development and entry into service in a competitive manner with the U.S. Air Force’s NGAD project. Rare public statements from the USAF on the matter seem to convey a belief that they are competing against the PLAAF for the sixth-generation timeline. 

Based on past experience and balancing active project workshare at major Chinese aerospace corporations, at present, Chengdu is most likely to be the prime contractor for the PLAAF sixth-generation fighter. It is plausible that sustaining a high rate of J-20 production of 100 aircraft a year (or more) from the mid-2020s may allow a staged conversion of the J-20 line for the sixth-generation fighter to enable more effective early delivery capacity, though this is highly notional at this stage.


Twelve years after its first flight, the J-20 has attained a relatively mature operational capability. However, it continues to gain new capabilities and technological advancements through the form of upgrades between successive batches. The aircraft will be further augmented by the development of new variants and most recently with the further milestone achieved by the WS-15 engine. The J-20 family is likely to see further growth in procurement and continued active production for several years, all of which are likely to result in a virtuous cycle enabling a well-supported logistics and upkeep network, as well as providing greater economies of scale and incentivizing more comprehensive future upgrade packages for existing aircraft. 

However, the J-20 itself will also eventually be succeeded. Much like how the J-10 family and domestic Flanker families (J-11B, J-16) were developed into new, more capable variants and actively produced while the J-20 was flight tested and seeing initial production in the early to mid-2010s, the J-20 itself will also be upgraded and new variants (such as the aforementioned J-20A) will be developed and produced. This is likely to coincide with early stages of testing and production of the PLA sixth-generation fighter which is likely to emerge later this decade, while some projected sixth-generation adjacent capabilities (such as enhanced UCAV control) are likely to be integrated and upgraded into existing J-20 variants.