China Flanker Thread II

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latenlazy

Brigadier
Tirdent said:
Changing over primary load-bearing structure from metal to composite is not the kind of thing you undertake as a learning exercise though, that works only if you are already highly competent in this field. Again, a look at the wider Chinese aerospace industry doesn't suggest composites would've come into that category at the time in question (or even today, compared to Russia). Integrating parts into larger forgings sounds decidedly more plausible (but is beside the point), as discussed above.
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That depends on the load bearing structure. It’s not like you’re going into a material swap blind. Just from your own structural testing you should have a good idea of what kinds and magnitudes of loads you should expect for each fitting and part and how reasonable it would be to swap materials, and which materials are appropriate to pair for the swap. This also btw applies to actual changes in shape. Most shape changes are not dramatic new geometries but additions or subtractions with well known and predictable effects on load distribution. It’s not just a dichotomy of skin vs structure. Real analysis goes into this stuff, and that can be done pretty straightforwardly. And that real analysis cannot be avoided because you *are* reverse engineering a whole production process so you need to do frame testing from scratch anyways just to make sure you’re reproducing comparable results from your reference copy. The shorthand you’re using undersells, imo, how much material swapping is possible.
 
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Schwerter_

Schwerter_

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Tirdent said:
I invite you to examine relevant real-world examples, one of which I actually mentioned.



I can completely believe the single-piece titanium bulkheads, integrating formerly separate parts into larger machined parts is the kind of improvement you commonly see between successive aircraft variants. Gripen C vs. A, or Su-30MK & -35 vs. Su-27 are great examples. That's a lot less of a change than going to composite though, which due to its vastly different mechanical properties requires the shape of highly loaded parts to be completely redesigned.

Kind of irrelevant too, because 1) titanium is not composite and 2) the argument was about structural improvements in Chinese Flankers that are not found in their Russian counterparts. As mentioned, increased use of integral machining features extensively on the Su-30MK and Su-35, however.



I only found a table of contents in Chinese for this one, Google Translate suggests the only aircraft mentioned is the J-8?



Changing over primary load-bearing structure from metal to composite is not the kind of thing you undertake as a learning exercise though, that works only if you are already highly competent in this field. Again, a look at the wider Chinese aerospace industry doesn't suggest composites would've come into that category at the time in question (or even today, compared to Russia). Integrating parts into larger forgings sounds decidedly more plausible (but is beside the point), as discussed above.

And whether you consider it likely or not, the structural details of the J-11/16 are in many respects closer to the Su-27 than the Su-35 that Justin Bronk considers to be less advanced. It also bears repeating that I'm not necessarily saying the Chinese airframes have no changes or no composites at all, only that there is little evidence that the scale is sufficient to support Bronk's argument.



If I don't speak the language and (despite the fact that I mentioned this before) explanations are not forthcoming, 'fraid not.

The first link is one that was discussed before and light on specifics (parts concerned, scale), while the screenshot may or may not be J-11 parts (I certainly can't place them anywhere on the aircraft). I've now gone and made screenshots of the segment leading up to and including the shot of the J-11 tails in the second link to capture the subtitles and run them through an image translator. That did confirm beyond all doubt that the tail fins are composite, but the process has taken me the better part of 40 minutes to extract the contents of less than 40 seconds worth of video. I frankly don't think that's a reasonable effort to expect, and remain *very* skeptical about composite application beyond this.
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Well, AV-8B's dimensions changes have multiple reasons and should not be simply put down to "changing materials MUST lead to major changes in exterior dimensions".

The paper I quoted also stated that the russians took a similar approach with titanium bulkheads when designing the su-35, but this in no way indicates that the Chinese flankers made very little structural changes, unless your definition of "structural changes" exclude changing designs and materials of individual componants. As to the book, there are paragraphs with accompanying pictures that clearly showcase the flanker's intake. In case you aren't aware, official Chinese publications seldom outright state what paticular model is discussed unless it is considered suffciently "Un-advanced", such as the J-8 in this case.

Changing over primary load-bearing structure from metal to composite is not the kind of thing you undertake as a learning exercise though
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According to the article on Yining Zhang, that is EXACTLY what they ended up doing due to necessity, because at the time of the project to indigenize the SU-27, many of the materials used on the flanker was not made in China, and the team decided that it would be less effort to change the design and materials than try to make a few dozen new materials from scratch.

Mind you, it didn't all end in success, J-11B initially had some issues with composites that had to be solved with using titaniam reinforcements to beef up the composites. One such instance concerning the intake was discussed in the book I mentioned as a case of problematic design process that should be studied and avoided in the future.


I'll state my point for clearing any possible confusions: There are concrete proof that at least in the development process of J-11B, there have been significant efforts made to change (or improve, whichever one you prefer) the materials used with varying success, and various sources both formal and informal, including but not limited to what I referred to above, have suggested that the Chinese flankers have altered structural componant design and an quite significantly altered material usage compared to the russian flanker initially imported. Not to say that what the Chinese did is more or less advanced that what the Russian did with the SU-35, but it would be unwise to dispose of their efforts and the changes made based solely on one's personal knowledge and not what's publically stated by reliable sources.
 
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Blitzo

Blitzo

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Tirdent said:
If I don't speak the language and (despite the fact that I mentioned this before) explanations are not forthcoming, 'fraid not.

The first link is one that was discussed before and light on specifics (parts concerned, scale), while the screenshot may or may not be J-11 parts (I certainly can't place them anywhere on the aircraft). I've now gone and made screenshots of the segment leading up to and including the shot of the J-11 tails in the second link to capture the subtitles and run them through an image translator. That did confirm beyond all doubt that the tail fins are composite, but the process has taken me the better part of 40 minutes to extract the contents of less than 40 seconds worth of video. I frankly don't think that's a reasonable effort to expect, and remain *very* skeptical about composite application beyond this.
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Wait, what exactly is the matter of debate here?

Is the question whether J-11B (and by extension, other SAC Flankers afterwards) uses composite materials in their construction?
Or is the question about whether J-11B uses composite materials in specific parts of its construction, such as the load bearing elements of the airframe?


Because if it is the first question, well in the
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link provided by Volpler, at 27:48 they directly state J-11B by name, as using composite materials in the wing and fuselage, and in the
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link at 8:38, they directly state that the tails of the J-11B (again, by name) uses composite materials.
(If you don't know the language, you'll just have to take the word of people who can understand the language. Though of course you can ask for clarifications, but simply rubbishing it is frankly non-constructive and borderline insulting)

If it's about specifically whether composite materials are used in the specific load bearing elements of the airframe, that is not something we know, but I don't think anyone else brought it up before you did in #8847.


You requested a translation of the video, while also expressing doubt as to whether it was even for J-11B in the first place, and translations have been provided to you.
That video in turn was linked, because previously you'd suggested that the use of composites in SAC Flankers "hadn't been conclusively proven," and suggesting it was only based on external views of primer colour.
Now that evidence has been provided, and translated as well, which definitively states that composite use is present in the J-11B (with specific elements of the airframe mentioned as including wing, fuselage and tails), what exactly remains to be clarified?
 
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weig2000

Captain
latenlazy said:
Normally I’d agree with this logic but they had to reinvent the entire production line and production process just to make the J-11B, and to further iterate on future variants. The cost that would have gone into structural iteration needed to incorporate new materials was already baked into the cost of needing to reverse engineer the production process from scratch.

If anything, the fact that they had to indigenize the production line on their own, likely using the techniques most compatible with their own available or desired production competences, makes it logically less likely that the J-11’s structural make and assembly details are one for one identical to the Su-27 than more.
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For all intents and purposes, J-11B is a domestic copy of Su-27 based on Chinese materials and components and subsystems. China had an agreement with Russia to build 200 Su-27's, first to import some Su-27's, then assemble the rest of them with imported sub-assembly kits and components from Russia. The Chinese realized in the process that the Russian avionics were very backward and it was extremely difficult to integrate with domestic weapons. The Chinese had also found a lot of inconsistencies between the documentation and the imported parts, due to the chaotic situation in Russia back then. So after just over 100 domestically assembled J-11A's, China stopped importing subassemblies and components from Russia entirely, and switched to production of J-11B completely based on domestic materials, components and subsystems, including engine, avionics and weapons.

The efforts involved were nontrivial; there had been extensive documents and interviews in Chinese to talk about the process and challenges they had encountered. It was quite impressive, to say the least. I would give the top reverse-engineering awards to the domestic production of both Su-27/J-11B and Vayarg/Liaoning/Shandong, if such award exists.
 
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latenlazy

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plawolf

plawolf

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Deino said:
Indeed, but I wonder why a fighter that has got new engines, not also got a new radar especially since this unit also flies some MLU'ed J-11BG with WS-10 and new radar.
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Maybe the schedules don’t align. The AL31s were most likely swapped out when the engines reached the end of their service lives and needed to be replaced anyways. Which may not align with the desired timetable for a radar change.

Or maybe the PLA has decided it doesn’t need every single plane in the fleet to have the newest expensive AESA radars when they have co-operative engagement capabilities and plan to use J11A/B and J10As as PL15 missile rack extensions for J16s and J10Cs instead.

Or maybe they did upgrade the radar and just didn’t bother to change the external paint colour of the radome.
 
Maikeru

Maikeru

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Registered Member
plawolf said:
Maybe the schedules don’t align. The AL31s were most likely swapped out when the engines reached the end of their service lives and needed to be replaced anyways. Which may not align with the desired timetable for a radar change.

Or maybe the PLA has decided it doesn’t need every single plane in the fleet to have the newest expensive AESA radars when they have co-operative engagement capabilities and plan to use J11A/B and J10As as PL15 missile rack extensions for J16s and J10Cs instead.

Or maybe they did upgrade the radar and just didn’t bother to change the external paint colour of the radome.
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Or maybe as its batch 1 the remaining service life did not justify an AESA upgrade.
 
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