China’s mystery aircraft
As it ended, 2024 left a curious yet fascinating parting gift for those who follow As 2024 came to a close, it left behind a curious yet fascinating development for those following military aviation. Images and videos of two previously unseen stealth aircraft, reportedly captured in the Chinese city of Chengdu, began circulating online, sparking a frenzy of debate. Were these new fighters or bombers?
At least one of the aircraft bore little resemblance to any current fighter in service. More importantly, could China have finally surpassed the United States in the race for next-generation air dominance?
To unravel the debate and the images, The Express Tribune reached out to Rick Joe, an expert on China’s military advancements, particularly in air and naval platforms. Using cross-examination of open-source information, Joe recently wrote his analysis of one of the two prototypes for The Diplomat, an online news publication based in Washington DC that covers politics in the Indo-Pacific region.
ET: Based off the photos we’ve seen, what can we assess about the two aircraft prototypes?
RJ: Since we don’t have a formal name for them, I’ll refer to the Chengdu (CAC) prototype as the J-36 and the Shenyang prototype as the ‘SAC jet’.
The J-36, as I wrote in my article for The Diplomat, is relatively large, has three engines, three air intakes – one dorsal air intake and two caret design side air intakes – and likely a large [internal] weapons bay with two smaller sized side weapons bays.
The SAC jet is a little more mysterious because we don't yet quite have a fully clear picture of it. It seems to have a lambda wing and two engines, likely with thrust vectoring which the J-36 is thought to have as well.
But ultimately we can't really say anything about the two airplanes with much confidence as what we can really see is all at very preliminary stage, especially for the SAC jet.
ET: Was there any chatter among Chinese military aviation observers before photographs of these prototypes came to light? How much did we know and what assumptions have been confirmed or debunked?
RJ: For the J-36, we have known in the PLA (People’s Liberation Army) watching space for the last year and a half prior to its emergence that something was coming and that it would likely be a large aircraft. And that perhaps it would not have a conventional plane-form or configuration consistent with what you usually consider to be a fighter.
We knew it would be large and we knew it would have greater signature reduction/stealth measures than previous fifth-generation aircraft. There were also some hints that it might have two seats in a side-by-side configuration. In the last two months prior to its actual emergence, there were rumours that it would have three engines as well, which was quite a surprise for many of us.
So for the, for the J-36, I would say our predictions were largely on point. If anything, it vindicated the PLA watching methodology for us.
For the SAC jet, it's somewhat less clear. There were some indications that SAC might be working on its own next generation or sixth generation aircraft or airframe. However, we didn’t expect it to seemingly make its first flight a week before the J-36 did. We thought it would maybe take a year or so for something to come out so that was more of a surprise.
ET: When it comes to China’s fifth generation fighters, we know the J-20 had a more former development driven by PLA as opposed to the J-35, which began as private venture aimed at the export market until the PLA showed interest. Do we feel it’s a similar case with these new prototypes, where one might be developed with more explicit PLA support or interest than the other?
RJ: It's generally believed that the J-36 is something that the PLA has actively committed to. But for the SAC jet, I would say the jury’s still out and we can’t say either way at this stage. For all we know, it is also a programme of record, but it might also be a more of a private venture.
On the other hand, for the FC-31 [which developed into the J-35], it was a bit clearer when it originally emerged that it was more of a private venture/technology demonstrator possibly for the export market.
ET: There’s some debate over whether at least one of the two aircraft is a tactical bomber/attack aircraft rather than a pure fighter aircraft. What is your take? Has any of the chatter that predated the photos revealed what the intended role for them is?
RJ: Of the two, the J-36 is the one some people online have been calling a strike aircraft or fighter-bomber, even referring to it as the ‘JH-XX’, a designation we've used in the past for a regional bomber the PLA might have been looking into for a while. However, rumours from the same sources that predicted the J-36’s emergence and characteristics are nearly unanimous in identifying it primarily as an air-to-air combat aircraft.
That said, everyone also agrees that it's obviously larger than a standard fighter aircraft, and that leads us to the evolving concept of what future air combat may look like and how the J-36 is designed to potentially optimise for that role.
Of course, the J-36 likely does have a secondary strike role as well. However, my assessment is that this thing is primarily an air-to-air combat aircraft. Yes, it's probably a little less manoeuvrable in certain regimes than existing fifth or fourth generation aircraft. However, it offers a lot more in other domains that, that make it optimised for what the PLA envisions to be the future of air-to-air combat.
ET: Speaking about the future of air power, the United States is pursuing the ‘loyal wingman’ or collaborative combat aircraft (CCA) concept, which are unmanned combat air vehicles (UCAVs) designed to leverage artificial intelligence and advanced networked technologies to operate alongside crewed combat aircraft. Is China working on its own version of CCAs to work along side its next-generation fighters, which as we’ve seen in the case of the J-36, may deviate from traditional fighter designs?
RJ: The PLA is very much looking into integrating its own CCAs and other UCAVs. We've seen a few, but not many of them, partly because it's much easier to hide unmanned aerial vehicles (UAVs) because they tend to have a smaller profile. The rumours surround the J-36 very much suggest that it may operate in a ‘system of systems’ with substantial off-board UCAV/CCA/loyal wingman support.
ET: Continuing on the topic of the future of air power, the United States is also exploring air-launched missiles that integrate both air-to-air and air-to-ground capabilities. Also, when we consider how many older-generation aircraft, such as the F-16 and Mirage, were initially designed as pure fighters or interceptors but later optimised for ground attack or multirole combat, does the traditional fighter/bomber distinction not become more a matter of semantics than a functional reality?
RJ: That has been a trend that's been going on for a long time now. I would say for the J-36, one term that might be appropriate for it instead of fighter, striker or bomber, is just combat aircraft.
It may be in the future that all combat aircraft will just exist on a spectrum of being a little bit faster versus being a little bit more manoeuvrable versus being a little bit more longer-ranged and so on. They might all have overlapping roles and capabilities, but just be slightly more specialised than another in one direction versus another.
ET: Coming back to the J-36, the photographs show that it has a rather unique three-engine layout. The J-36, and perhaps the SAC jet well, also feature a tailless airframe. What are the implications of such a design choice?
RJ: There have been a few thoughts around the J-36 having three engines. One of the narratives that have sprung up on the Internet is that Chinese engines are not powerful enough to allow two engines to power the airframe. Some have thought that the central engine might be of a different type – some people have floated the rather silly idea that it could be a ramjet.
I don't believe in either of those ideas, but I think that the first one might be a little bit closer to reality, although not quite on target. My view is that all three engines are the same.
Current rumours suggest that the J-36 might be powered by either a variant of the WS-10 — China’s domestic jet engine in the same thrust class as the American F100 and F110, as well as the Russian AL-31. The WS-10 is currently used in China’s J-10, J-20, and Flanker aircraft. Alternatively, the J-36 could be equipped with three WS-15 engines, which are higher-thrust engines being utilised in newer models of the stealth J-20 fighters.
We don't know what exactly they're using right now, but whatever they're using is likely to be an interim engine that China may replace with three variable cycle engines in the coming years, or maybe sometime in the next decade, once they are developed. The PLA is comfortable to proceed with an aircraft programme even if it's not using its final engine. They don't let the power plant hold the project hostage.
I think the benefits of three-engine layout likely stem from the weight of the J-36. I think this aircraft is just very heavy and it’s possible that even with future technology, achieving the desired kinematic performance with just two engines might not be viable. This may be because of the limits of the technology or because the future engines would be too large in diameter to work with the airframe in an acceptable way.
In general, there's a reason, for example, why stealth aircraft do not use, say high bypass engines like those on an airliner. For instance, the engines that power a Boeing 787, you won’t see them being use on a B-2 or B-21 [stealth] bomber.
As you probably know, all aircraft are the result of compromises. However, having three engines with separate air intakes for each could allow each engine to power its own genset, leading to significantly higher power generation. Much greater power generation has been rumoured as one of the key features of the J-36, along with its potential future capabilities. Alternatively, the three-engine design might also provide greater cooling capacity, along with more room for future cooling system expansion, compared to a two-engine setup.
Coming on to the tailless aspect, it is quite widely accepted to be just a benefit for further signature reduction. Less control services on an airframe leads to greater signature reduction or ‘better stealth’. Of course, without tails, it means that your manoeuvrability may suffer a little bit more compared to an aircraft with tails, holding all else equal.
ET: Observers have been quick to the J-36 and SAC jet prototypes as sixth-generation aircraft. Can you elaborate on aircraft generations? What would sixth-generation imply over fifth-generation, for instance?
RJ: I personally am not a big fan of the generation system, although I understand why it exists and I do think that it can be useful. In the context of the forthcoming J-36, I prefer to call it just a ‘next-generation’ aircraft rather than ‘sixth-generation’. The rumours around its role clearly indicate that the PLA view it as different and more advanced than current fifth-generation aircraft that they have like the J-20, J-35, etc.
If you're asking what I think the division between fifth and sixth-generation aircraft might be, honestly, I don't feel I'm in a position to provide a definitive answer. I'm just as much in the dark as anyone else.
That said, I do have some personal suspicions. Sixth-generation aircraft may feature enhanced signature reduction, potentially greater power generation, and much more advanced on-board processing and networking capabilities. They could also offer improved command and control over unmanned aerial vehicles, among other things. Additionally, we might see a greater weapons base, possibly including directed energy weapons at some point. These could all be potential features of sixth-generation designs. However, at the same time, a lot of those features might be retrofitted onto fifth-generation or even fourth-generation aircraft to an extent.
ET: We know the United States has its own sixth-generation combat aircraft in development under its Next Generation Air Dominance (NGAD) programme, although no details or images have come out about it so far. Some have seen the Chinese prototypes as PLA’s answer to that programme. Do you agree with that assessment or do you see them as an independent development driven by China’s evolving air combat planning?
RJ: I don't think that either of these aircraft was meant to be an answer to the NGAD or anything like that. I think that these are aircraft that the PLA have been developing on their own schedule, in line with their own requirements as part of their assessments of where US air power is evolving. So no, I don't think there's any relationship between their emergence and the timeline of the US NGAD programme or what state of development the latter is in.
ET: Regardless of the sixth-generation label and comparisons to NGAD, how far has China’s aviation industry come based on these prototypes and in-service fourth and fifth-generation aircraft? What do you feel enabled this transformative advancement?
RJ: China’s aviation industry has made a lot of significant advances, particularly in items that have a lots of optics, but also especially in terms of things that are less obvious like avionics, materials, aerodynamics, weapons, subsystems, and yes, even engines. Over the last five years or so, they've made quite a significant progress in engine development and technology.
All of this progress is the result of decades of effort, dating back to the early and middle phases of the Cold War. It's the outcome of consistent investment and the struggles faced by China's aviation industry. They wouldn’t have the J-36 or J-20 if they didn’t originally try to reverse engineer and master aircraft like the MiG-17, MiG-19, and MiG-21 as the J-5, J-6, and J-7. They also owe part of their success to efforts during the Cold War to develop domestic aircraft designs like the J-8 and others that were often too ambitious and costly for them the time. That experience in programme management, combined with having the infrastructure and human resources consistently in place, is what ultimately allowed them to reach this point.
People think reverse engineering is just about copying and pasting without knowing what’s going on, but really, to do it properly you need to master fundamental technologies and have the capability to produce, iterate and redevelop them. That is what allowed China to develop more domestic designs like the JH-7 and J-10, and to produce their own advanced Flanker variants, like the J-11 and J-16, which are now arguably the best Flanker types in the world. All that in turn fit in back into their fifth-generation fighters, like the J-20 and J-35.
Some people argue and rightly so that cyber-espionage or whatnot has enabled China’s more recent developments, but that's mostly being based on external similarities between aircraft like the J-35 and the US F-35. The problem with that is that while I'm sure that cyber-espionage has occurred and in both directions, there's enough differences say between the J-35 and the F-35 to know that they're rather unique and independent designs with very similar external configurations. That’s not dissimilar to how in World War Two, you had so many monoplane fighters that look almost identical but were their own unique designs or how today, we have the Boeing 737 and Airbus A320 – two unique designs that aim for similar roles and so, look quite similar.
ET: A decade or so ago, reports suggested Chinese industry had teething issues with jet engines. Is there reason to believe those issues have been overcome or do they still persist?
RJ: High performance aero engines are the Achilles’ heel of most military industries, outside of a very small handful of nations. Whether China has overcome those issues, I would say for military purposes, they've come a long way. The WS-10 jet engine is now in wide use among basically almost all active production PLA tactical combat aircraft. The older J-10C fighters in the PLA, which are single-engine aircraft, are being refitted with the WS-10, which attests to the PLA’s confidence in the engine and its performance.
Also their lifespan has improved considerably compared to a decade ago. China’s land-based Flankers may soon enter production with the WS-10 and the J-20 fifth-generation fighters have been in production with the WS-10 since the beginning of this decade.
The WS-15 engine, which is going to success the WS-10 on new J-20 variants is, of course, even more capable and will likely have its own iterations as well. And then there are various other designs like the WS-21 – which is based off the WS-13, developed by reverse-engineering Russia’s RD-33/93 engine – and the WS-19, which is a jet engine in the class of the American F414 and is going to be used on the J-35.
ET: China’s military aviation development and procurement appear to work quite differently from the U.S. and other industries, where projects often have lengthy development periods. In contrast, China’s aviation industry seems to be progressing rapidly, introducing and bringing multiple new aircraft types into service over the past two decades. Why do you think that is?
RJ: I can't really comment about the US procurement system because this isn't quite as simple as what their procurement model is, but it's also about their respective political systems, their approach, what their military wants, respectively. I will say that it is true that the PLA are more probably more willing, on the surface at least, to iterate and to not have certain subsystems take the entire aircraft hostage. For example, engines are the most notable one.
But at the same time, that doesn't mean that they're accepting an inherently useless product. The reason for accepting new products that may have an interim subsystem is that everything else about it is still useful and will help drive and accelerate development of the military as a whole.
ET: Last year, China also made progress with a two-seat version of the J-20 fighter and the J-35 fighter aimed at being launched from aircraft carriers. What do you make of those programmes?
RJ: There are two variants of the J-35 that we know of. There’s the one designated just ‘J-35’, which is the variant capable of taking off from China’s new catapult equipped Fujian aircraft carrier and the ski-jump of the older Liaoning and Shandong carriers. To our knowledge, it is not yet in service, but it might enter service this year or maybe next year in a very initial stage.
The ‘J-35A’ is the land-based variant with a smaller wingspan, no reinforced landing gear, no nose-gear for catapult launch and no tail-hook [for landing on aircraft carriers], etc. This aircraft is likely not in service either, but it will be sometime in the new future.
To my knowledge, the two-seat J-20, which might be called J-20S, we're not sure if it's actually intended for active service. It might be, but it seems that right now that it's being used mostly as a technology demonstrator to help assist the development of both the J-20A variant, which is the new one equipped with WS-15 engine, as well as other major avionics and power generation improvements. It may possibly be a partial technology demonstrator for certain subsystems on the J-36 as well.
ET: In terms of optics at least, China seems to have beaten the US to the punch in flying its own next-generation aircraft. How do you think the US is likely to respond to Chinese military aviation developments?
RJ: This has been something that has popped up on social media as well. A lot of people argue that the US will use the next-generation Chinese prototypes as an opportunity. They repeat a myth from the Cold War that when the US discovered the Soviets were developing the MiG-25, it supposedly overreacted by developing the highly successful and capable F-15 fighter in response, even though the former ultimately turned out to be an interceptor rather than an air-superiority fighter. That myth is not entirely true and the development of the F-15 was largely unrelated to the initial information about the MiG-25.
That said, the narrative that the US might take this as an opportunity to get its programmes in order and develop something even more capable does have some merit. Whether that will actually happen and how the US will respond —politically, financially and in terms of what the industry can deliver — is something I can't predict. With Donald Trump about to enter office again, it’s hard to say what decisions he might make, and who knows if Elon Musk could influence him in any way.
It’s not just a matter of having the technology. Just because a country has the industry on paper doesn’t mean it can immediately produce an amazing aircraft. There are other constraints — socio-political, financial and industrial — all of which have some crossover with each other.
At this stage, there are many other questions that could be asked, but we’re still so early in these programmes that the best approach for both the media and people online is to take a step back. One narrative that has circulated is how the demonstrators the US flew around 2018 compare to the J-36 and the SAC jet. The validity of that comparison really depends on how representative those demonstrators are of final production aircraft. We also know the PLA has flown their own demonstrators to inform their sixth-generation or next-generation developments, including the J-36, but they haven't shown those either.
So, it's not a matter of the PLA wanting to show off these aircraft. It’s more about the fact that they’re in a development and testing stage where they can't practically hide them, even if they wanted to, given the locations where these aircraft are being produced i.e. mainly in urban areas.