J-20 5th Gen Fighter Thread VI

Until they release the exact specs of the KLJ-10(?), we cannot do so much more than speculate based on size.

@Brumby, what you are saying does not make sense.

We are told the radar is in the same generation as the APG-81 by one of the designers, but there is no indication whether he means it is better, worse or exactly equal.
Basically, this is a non statement.

Biscuits said:

Until they release the exact specs of the KLJ-10(?), we cannot do so much more than speculate based on size.

@Brumby, what you are saying does not make sense.

We are told the radar is in the same generation as the APG-81 by one of the designers, but there is no indication whether he means it is better, worse or exactly equal.
Basically, this is a non statement.

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I thought that they did release the official specs. How are they going to hide it if they export it?

How many J-20s have been produced? My knowledge is that there are 2 squadrons of them, they never have got certified for FOC and all of them are acting as testbeds for datalinking , radar integration, EW, IRST systems etc. So radars are never going to be finalized and the only permissible product worthy enough would be j-20s radar is the one that can outperform the Japanese or American AESA radars + AAMs system. The radars gifted to 4+ gen fighters would therefore be stepping stones.
I don't know if it is actively discouraged to divert to a different topic ( from the radars being discussed ) but is there any reliable information regarding fighter jet engines modified for naval decks ( as an engine needs to be protected from the much known corrosive environment of saline ocean water).

The KLJ-7A is most likely NOT the radar on the J-20, nor would a direct derivative be put on the J-20. The KLJ-7A is an air-cooled radar, meaning that in comparison to a water-cooled radar, which can emit more heat, it would be underpowered.

The reason it's air-cooled is to reduce the weight of the radar unit, allowing the JF-17 operators to preserve the balance of the aircraft without needing to modify it, as with the Su-30, to sustain the greater weight.

Inst said:

The KLJ-7A is most likely NOT the radar on the J-20, nor would a direct derivative be put on the J-20. The KLJ-7A is an air-cooled radar, meaning that in comparison to a water-cooled radar, which can emit more heat, it would be underpowered.

The reason it's air-cooled is to reduce the weight of the radar unit, allowing the JF-17 operators to preserve the balance of the aircraft without needing to modify it, as with the Su-30, to sustain the greater weight.

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Since KLJ-7 is being exported to another country, why would china risk having the same or even an upgraded variety of that in this premier stealth fighter?

latenlazy said:

So...basically you’re filling gaps in information with your own select choice of speculations? Granted the technical complexities of AESAs that you mentioned are real, but why is the default assumption that they’re struggling with those technical challenges when they’ve been fielding AESAs in other forms for well past a decade now, and have been fielding production AESAs in two other fighters for the last 3-5 years? Sure, the technology can always be iterated on, but you don’t put out 200+ J-10C and J-16 combined in production if their radars aren’t also in serial production.

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PLA watching as explained to me is about making guesses - some are grounded through other corroboration and some are simply speculations because of the lack of reliable information. In connecting the dots I am attempting to reconcile to Butowski's statement by offering a plausible explanation given the nature of AESA development and the complexity that comes with the nature of the technology. I did not used the word "struggling" as your choice of words. I am simply stating that the pathway can be lengthy especially if the design choice is complex.
When the APG-63(v)2 was introduced in 2000, 18 F-15C were initially installed with it as they went through operational testing. There is precedent in terms of limited rollout of AESA adoption especially when one is dealing with something new. It is therefore plausible that some sets are installed in J-10C and J-16 for operational evaluation prior to series production.

latenlazy said:

...wrt to what the director of the 14th institute might know about the APG-81 and APG-77, you do know what all that espionage on US miltech companies is for right? If they’ve taken so much data on the F-35 and F-22 and don’t have a rough idea of how their systems perform then either Chinese cyberespionage really isn’t that big a deal or they really have no clue what they’re doing. Neither seem to be particularly sensible assumptions..

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I would rather not go into espionage type of reasoning to justify a position as that would be highly speculative. This forum pride itself in being professional and so let's stick to grounded facts. The statement made by the 14th institute is simply not useful because that statement can be interpreted in so many ways. For example, I believe both APG-81 and APG-79 use liquid cooling and by comparable it could suggest that the one planned for the J-20 is also liquid cooled. Without specifics, that statement is practically useless. However if something more specific like what the Indians disclosed with their planned AESA development, we can make a better judgement on the issue. This is taken from the Indian military thread (post 4385) shared by Hyperwarp.


We can see that the Indians are aiming for a TR power output of 10w. This is probably still behind the technology adoption in the APG-81 which we estimate to be likely around 15w or more (we just don't know for sure), but it does give us a sense of relativity. In contrast, the Russians with the Zhuk ME was only getting 5w. .

latenlazy said:

It’s not hard imagining the APG-77 and APG-81 being roughly comparable. Packing on the APG-81 is probably more efficient, but it’s also using a smaller array than the APG-77. As you say, SW is a critical part of performance for AESAs. A lot of the improvements of the APG-81 from APG-77 that’s software related is also probably backwards compatible.

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It doesn't work like what you described. Frequency choice dictates wavelength which then dictates TR sizing which then affects packaging density which then affects cooling management. If you don't know their respective design frequency choice you can't make those assumptions you are making. The other thing is because the F-22 is air superiority and the F-35 is multi role, the demand on radar towards clutter management is different which then affects frequency choice and radar mode design.

Inst said:

The KLJ-7A is most likely NOT the radar on the J-20, nor would a direct derivative be put on the J-20. The KLJ-7A is an air-cooled radar, meaning that in comparison to a water-cooled radar, which can emit more heat, it would be underpowered.

The reason it's air-cooled is to reduce the weight of the radar unit, allowing the JF-17 operators to preserve the balance of the aircraft without needing to modify it, as with the Su-30, to sustain the greater weight.

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I agree that what will end up in the J-20 is very likely to be a totally different design than the one for JF-17. Leading edge technology is liquid cooling especially if you are going for higher TR power output. The other consideration is that the J-20 will have a suite of LPI mode features with its radar and probably none for the JF-17 because it is not stealthy by comparison.

Inst said:

The KLJ-7A is most likely NOT the radar on the J-20, nor would a direct derivative be put on the J-20. The KLJ-7A is an air-cooled radar, meaning that in comparison to a water-cooled radar, which can emit more heat, it would be underpowered.

The reason it's air-cooled is to reduce the weight of the radar unit, allowing the JF-17 operators to preserve the balance of the aircraft without needing to modify it, as with the Su-30, to sustain the greater weight.

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I do not recall reading KLJ-7A is air cooled.

Are you sure you are not confusing KLJ-7A with LKF601E? LKF601E is an air cooled AESA that has been trialled on a prototype JF-17 and looks like it is designed to be able to easily upgrade fighters like JF-17.

I haven't read anything about KLJ-7A being air cooled, and at Zhuhai last year it was confirmed that three variants of it exist; one baseline single array version, one version mounted mechanically rotating platform, and one version with two additional side looking arrays.


However it is certainly true that KLJ-7A isn't the AESA that is equipping J-20 (and nor is LKF601E)

Brumby said:

PLA watching as explained to me is about making guesses - some are grounded through other corroboration and some are simply speculations because of the lack of reliable information. In connecting the dots I am attempting to reconcile to Butowski's statement by offering a plausible explanation given the nature of AESA development and the complexity that comes with the nature of the technology. I did not used the word "struggling" as your choice of words. I am simply stating that the pathway can be lengthy especially if the design choice is complex.

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If you are interested in reconciling Butowski's claim, it is fairly simple.

As Deino explained a month or so back when the article was released, Butowski is an aerospace journalist whose focus is on Russian aviation, with many sources in the Russian industry, and his claim that China having no production fighter AESA was from Russian sources.

https://www.sinodefenceforum.com/j-20-5th-gen-fighter-thread-vi.t8169/page-472#post-542092


PLA watching is indeed about guesses, but it's also about making educated guesses, with "educated" being the operative word. Specifically, it means evaluating sources and journalists and commentators and trying to judge how accurate they are likely to be. This can be done by considering where they likely get their information from, as well as the kind of track record they have in predicting past relevant events.



There is a rather simple two step smell test when considering a new claim:
1: how credible does the claim sound in respect to the known body of knowledge.
2: how credible is the source (i.e.: how likely is it for the source to be able to be able to accurately make the claim they are making based on where they get their information from, and/or what kind of relevant track record they have).

Totoro said:

So, if we are to aggregate all the indications so far, we have these:

1. Interview with a 14th institute spokesperson at Zhuhai 2018 saying "J-20 and J-16 use some kind of a phased array radar"
2. Interview with director of 14th institute saying "our airborne radar is completely comparable to the F-35's APG-81 radar and the F-22's APG-77 radar" though he doesn't go into details, whether he's talking about radars on actual PLAAF planes or whether he's talking about 14th institute's radars in some stage of development. Also, "completely comparable" is a rather vague statement, but it does give credence he's talking about active phased array.
3. Export geared model of AESA radar is marketed for JF17 at Zhuhai 2018.
4. Two different phased array designs seen on J10B and J10C, via imagery. While the first one does resemble what Russians tried with their PESA technology, the latter one looks different, and is somewhat closer looking to the US AESA radars. Though of course, superficial visual similarities don't have to be conclusive.
5. I also remember there were some research papers on use of AESA radars for J10 radar, though I don't remember the details nor can I find those papers.
6. Myriad of larger AESA radars in use on other platforms for some years now might also be somewhat indicative of the fighter based AESA radar presence in J-20 and J-16.

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1-6 are all useful.

However the foundations for "indications" is the summative grapevine of the PLA watching community. Since before J-20 emerged, it was stated that it would have an AESA. If we had all of those points 1-6 without the continuity of information from when J-XX was first said to have an AESA and that claim not changing for the last decade and a bit, then I myself would doubt whether J-20 may have an AESA as well.

Even the national fighter development study from 2003 done by Gu Songfen specified a requirement for the "next generation fighter" would include an AESA. Of course, not everything from that study eventuated in the exact way that they described but the vast majority seems pretty damn close.




You are interested in the "best" sources available, which is fair -- but I think for certain aspects of PLA watching the "best source" is the community.