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Chinese air power thread 18

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    Originally posted by Inst
    Also, another point of interest might be the J-20 radar. Now that we have precise measurements, the radome is about 1.3 meters, implying about 1 meter aperture diameter, or a 30% superiority in size over the F-35.
    There's this article I've been meaning to find of late that reports the J-20 jamming and spoofing older Chinese AESAs. With the large diameter, what this implies is that the J-20, with same generation radars, can suppress the F-35's radar system, nullifying its inferiority in stealth and forcing the latter to rely on EODAS
    In real combat environments with surface clutter, jamming and decoys, all stealth fighters will detect and track each others by IRST and ESM long before they can see each others on radar.


    Originally posted by Inst
    If the J-20 is flying higher than the F-35, the latter can't utilize its EOTS while the J-20 can, meaning that the latter is now out-sensored by the J-20 and has to rely on its defense systems
    There isn't enough altitude difference between J-20 and F-35 for J-20 to stay out of EOTS field of regard and aircraft cruising near their service ceiling will fly pitch up slightly anyway to generate more lift.

    Comment


      length - 21.1 m
      scope of a wing - 13.0 m

      Click image for larger version

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        The J-20's fuselage length in front of the cockpit is much shorter because the radome is less pointy, it's almost a copy of the F-35 but with a larger radome. The DSI intakes are not designed for very high speed so why design a radome optimized for very high speed?

        Comment


          Originally posted by Blitzo View Post
          ... the length of J-20 should be from nose to end of tail booms...
          Originally posted by QuantumFX View Post
          ... The production J-20 is slightly longer than the demonstrators 2001/2002. Longest point is the tail-boom...
          The fact is that during its development Chengdu Aircraft Industry Group J-20 aircraft was undergoing through some redesigning and as such was getting some modifications ...





          ... so it is quite possible that the total length of the first produced aircraft, including the prototypes, measures the distance from the nose to the tips of the tail fins, and on those lately produced aircraft, the one from the nose to the tips of the redesigned tail booms ...

          Please take a look the tail fins' tips and the booms' differences on the following images:

          The first produced aircraft ...



          ... and those lately produced


          From the next two images, it is, I think, visible that on the J-20 prototype, the most protruded points at the rear are the tail fins' tips...


          ... and on those later produced units, its tail booms. Besides, the tail finstips were redesigned ...




          Originally posted by QuantumFX View Post
          new one,
          You made me, QuantumFX, to messure J-20 aircraft, once more, with this nice image ...

          The first thing I have noticed was that neither J-16 nor J-20, those in the middle of the image, are entirely aligned with the runway's centerline ...

          Please click on the image below for the larger view


          that's why I have, in the case of Shenyang Aircraft Corporation J-16 aircraft, rotated the image 1,4 CCW to get auxiliary measuring lines parallel to the aircraft ...

          Please click on the image below for the larger view


          ... but also and the required variables: kL and kWs.



          After that I have rotated the image with the Chengdu Aircraft Industry Group J-20 aircraft 0,7 CCW...

          Please click on the image below for the larger view


          and got the next measures: length of 20,88 m / 68 ft 6,0 in and the wingspan of 13,09 m / 42 ft 11,4 in.



          Because of the perspective from which the image was taken it is quite possible that the aircraft are a little bit distorted so I can't be sure at all the measures I got are quite accurate. That in what I am sure is that I am not going to measure J-20 anymore :-) Some Chinese sources quote J-20's length of 20,3 m and wingspanof of 12,88 m. "Well, of course I trust you, but please show me where have you put those auxiliary measuring lines then we can talk" :-)

          Since I like J-20 aircraft, maybe I would measure it once more, but only if someone could guarantee me it will get. AL-31F(N) M3 (изд. 99M3), twin-shaft, TVC, afterburning, turbofan engines (fan diameter: 924,0 mm / 36,4 in; BPR: 0,61:1; engine architecture: 3F–6HPC1HPT–1LPT), OPR: 27,72:1, rated at 150,04 kN / 15.300 kgf / 33.731 lbf on the afterburner or AL-41F-1 (изд. 117), twin-shaft, TVC, afterburning, turbofans (fan diameter: 932,0 mm / 36,7 in; BPR: 0,65:1; engine architecture: 4F–9HPC1HPT–1LPT), rated at 147,10 kN / 15.000 kgf / 33.069 lbf on the afterburner, already tomorrow. That's unlikely, but very likely that Su-57 will get its Saturn "изделие 30" (Type 30) engines sooner than CAC J-20 its SAC WS-15 engines manufactured by Xi'an Aero-Engine Company

          I just wonder how advanced and modern this long-awaited WS-15 engine could be if it's really based on once (20 years ago) unique R79V-300 twin-shaft TVC afterburning turbofan (fan diameter: 1.100 mm / 43,3 in; BPR: 0,81:1; engine architecture: 5F–6HPC1HPT–1LPT), OPR: 22,0:1, rated at 152,00 kN / 15.500 kgf / 34.172 lbf on the afterburner, aimed for Yak-141 VTOL aircraft, as and those later models of the engine, R79M-300, rated at 181,42 kN / 18.500 kgf / 40.786 lb and R179-300, rated at 200,06 kN / 20.400 kgf / 44.974 lb. Just perfect numbers for J-20's engines. The only problem is that Soyuz R179-300 engine was way too large and too heavy for J-20 fighter, the same way as Saturn AL-41F ("изделие 20") was for Sukhoi Su-57

          By nothing more but my humble opinion and those engines of something lower performances, Saturn AL-41F-1S (изд. 117C), twin-shaft, TVC, afterburning, turbofan engines (fan diameter: 36,7 in / 932,0 mm; BPR: 0,65:1; engine architecture: 4F–9HPC1HPT–1LPT), OPR: 23,10:1, each rated at 86,30 kN / 8.800 kgf / 19.401 lbf dry and 142,20 kN / 14.500 kgf / 31.967 lbf with the afterburner and Salyut AL-31F M2 (изд. 99M2/99СМ), twin-shaft, TVC, afterburning turbofan (fan diameter: 924,0 mm / 36,4 in; BPR: 0,61:1; engine architecture: 4F–9HPC1HPT–1LPT), OPR: 26,09:1, rated at 142,20 kN / 14.500 kgf / 31.967 lbf on the afterburner, are still far better and more reliable powerplants than the Shenyang Aircraft Corporation WS-10B or WS-10G/IPE engines which design was based on the CFM56-7 and Saturn AL-31F engines' cores.

          ... yet until about a quarter of a century ago, the trains in China were towed by the steam and a couple of diesel-electric locomotives ... By the end of 2016, China had 22.000 km / 13.670 mi of railtrucks, just those for a high-speed railways (Just amazing infrustructure! I'm not sure anybody but China is capable of doing something like that. U.S. are just at the beginning of the construction of their HSR), but their trains were designed and constructed by the technologies developed by ABB, Alstom, Siemens, Bombardier, Toshiba, Hitachi, Kawasaki and Mitsubishi Electronic. Nowadays, all series of Chinese HSTs, including those latest (CR400AF and CR400BF) are produced in the Chinese factories: CRRC Qingdao Sifang Co., Ltd., CRRC Tangshan RV Co., Ltd., CRRC Changchun RV Co., Ltd. and CRRC Nanjing Puzhen Co., Ltd, by the adopted European and Japanese technology. However, when it comes to the permanent magnet synchronous motors, Chinese are trying to produce such a motors of their own design because no one is willing to sell them such an advanced technology.

          Why have I mentioned all this? Just to show there are a couple of things you just can't get for the money. One of them is modern turbofan engines' technology, and China itself has been struggling a lot for a long time in the designing and producing them, no matter if they were aimed for the propulsion of their latest civil airliners, Comac C919, powered by two CFM LEAP-1C30, twin-shaft, high-bypass, turbofans (fan diameter: 78,0 in / 1.981,2 mm; BPR: 11,0:1; engine architecture: 1F+3LPC–10HPC2HPT–7LPT), OPR: 50,0:1, each rated at 137,14 kN / 13.984 kgf / 30.830 lbf dry and Comac ARJ21-700, powered by two General Electric CF34-10A, twin-shaft, high-bypass turbofans (fan diameter: 53,0 in / 1.346,2 mm; BPR: 5,0:1; engine architecture: 1F+3LPC–9HPC1HPT–4LPT), OPR: 29,0:1, each rated at 78,50 kN / 8.005 kgf / 17.648 lbf dry, or for all those military aircraft.

          Its arrear in the development of the turbofan engines, China has been trying to compensate by skipping some initial steps in the engine development and designing, just turning around and losing time, mostly unsuccessfully, by imitating obtained foreign technologies. Since the 1990s, China has invested heavily in the development of jet engine manufacturing capacity. They encountered the same problems that Russia encountered early in the development of their engines. It is just very difficult to develop the necessary engine design, construction and manufacturing technology, but China had some advantages. First, they know where Russia went wrong so many of these mistakes could have been avoided. Second, China has better access to the Western manufacturing technology. Finally, unlike in the former Soviet Union, China was able to develop its own engine manufacturing capabilities in a market economy, much more efficient than the 70-year-old planned economy of the former Soviet Union...

          Sooner or later China will get rid of Russia's dependence on military and partly of U.S. and European (GE Aviation, P&W, SAFRAN and RR) dependence on civil jet engines, but in the meantime their engines' manufacturers will need further efforts. I do not doubt that in the end they will succeed. They have a vision, they have a goal, they have a resources and they are incredible persistent. A very specific and unique mentality.

          Cooperation with the Ukrainian military industry and supreme factories like SC "Antonov" (ДП "АНТОНОВ"), Ivchenko-Progress ZMKB (ЗМКБ Прогрес ім. О.Г.Івченка), PJSC "Motor Sich" (ВАТ "Мотор Січ") and SE GTRPC "Zorya"-"Mashproekt" (ГП НПКГ "Зоря"-"Машпроект") could certainly be of a great help to China, and how much would this cooperation mean for the stumbled Ukrainian factories, after their breakup with Russia, it is not necessary to mention it either…

          Mario
          Last edited by mfranjic; 12th March 2018, 09:00.
          'Only a life lived for others is a life worthwhile' - Albert Einstein

          Comment


            @Mario !

            Thanks a lot.
            ...

            He was my North, my South, my East and West,
            My working week and my Sunday rest,
            My noon, my midnight, my talk, my song;
            I thought that love would last forever; I was wrong.

            The stars are not wanted now; put out every one:
            Pack up the moon and dismantle the sun;
            Pour away the ocean and sweep up the woods:
            For nothing now can ever come to any good.
            -------------------------------------------------
            W.H.Auden (1945)

            Comment


              is there a downward shot of Mig 1.44...

              Comment


                You don't actually need to align the lines; just use the Pythagorean to adjust the lines before you do the calculation. In honesty, the +10 -20 errors I see with the J-16 are remedied when the J-16 is adjusted, so the figures on the J-16 actually match the listed ratio for the Su-27, almost precisely. That implies the J-20 is about 20.85 meters long with a 12.9 wingspan.

                @mfranjic:

                The problem with engines isn't so much the copied design; basic and workable schematics are quite common and easy to steal with espionage. The problem with engines is the metallurgy: designs are built specifically for metallurgical compounds, whose manufacture is extremely difficult to duplicate. That's the Chinese problem, and they claim they recently made breakthroughs in Rhenium alloys. As to whether those are real breakthroughs or pseudo-breakthroughs is another thing.

                Comment


                  Originally posted by mfranjic View Post
                  ***
                  That is some insane attention to details sir.

                  All I can say is,



                  Comment


                    Yeah that is one high effort post.

                    +500 to mfranjic
                    sigpic

                    Comment


                      So now that we're more or less done with the length, how about another round of measuring for the weapon bays? I'm getting 4,6 meters by 1,05 meters, with maximum depth of some 0,55 meters (though of course with carriage pylons and the forward third of the bay getting more and more shallow that doesn't mean all of it can really be used for weapons)

                      Comment


                        How do you get 55cm depth? I measure the bay as about 2-2.5 meters wide, with the bay being about 30-40cm deep, assuming that maximum depth is one-eight of the bay width.

                        If you use a cubic method, i.e, finding the distance from the arches of the bay to the joint, then moving it down to a line parallel with the length axis of the J-20, then moving it to the wingspan axis, you can get roughly 5% of wingspan, which gives you over 60 cm. That's incidentally enough for the JSM. The big problem is the length of the weapons bay: if it's roughly 4.5 to 4.6 meters, it won't be able to fit a 7-meter long YJ-12. But if there are AShMs designed for the J-20, it should be able to carry a tolerably capable anti-ship missile.

                        For reference purposes, JSM is roughly 40 cm in diameter, including fins but not the wing.

                        This sort of sets Blitzo's argument that the J-20's bays are too shallow for it to be a striker on fire, and we're back to a striker (small wing area), as opposed to a fighter-interceptor.
                        Last edited by Inst; 15th November 2017, 15:37.

                        Comment


                          How about radome ?. I myself tried and got 1.2 x 1.113m (include tilting)-image later if anyone interested- Possible antenna diameter assuming 10 GHz X-band edge treatment is 90 cm in diameter. Possible number of modules that can be fitted is 2827. With half wavelength spacing. and of course im curious about Chinese AESA module capability. 5 watt module would give like 14 Kw of power 10 watt would be 28,2 Kw.

                          Comment


                            Nobody intrigued by the lack of uniformity on the camo pattern?

                            Comment


                              1.275 to 1.285m wide.

                              See, that's the part that makes no sense for me. The PAK-FA has a radome of about 1.31 m^2. The J-20 is supposed to have the largest radar of any fifth gen, so what's actually going on here?

                              Comment


                                Well two possible reason i could think of.

                                1.Counter stealth, maximizing detection range against small target.. China have lots of cruise missile (Russia, India, Japan, Korea, Vietnam and of course US) and stealth user around. small power aperture product for fighter aircraft is not acceptable. By aiming largest possible aperture it allows maximizing detection range without expensive investment for TRM power.

                                2. Stealth. You can have large radome But, the antenna diameter would be constrained by the edge treatment to reduce structural mode RCS. The edge would need to be treated by 4 wavelengths of your lowest threat frequency. S band is not practical in this respect as it need 40 cm width edge treatment. Possible treatment would be C (5GHz) down to X band. If the threat frequency is X-band. That 1.2 m width radome can accommodate 90 cm diameter antenna. larger antenna is possible but edge treatment will suffer as it have to be designed for higher threat frequency.

                                Example for JSF.

                                Click image for larger version

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                                  How do you get 55cm depth?
                                  https://snag.gy/tndaqp.jpg

                                  Comment


                                    Originally posted by Inst View Post
                                    This sort of sets Blitzo's argument that the J-20's bays are too shallow for it to be a striker on fire, and we're back to a striker (small wing area), as opposed to a fighter-interceptor.
                                    74~78 m^2 is a small wing area?
                                    Last edited by latenlazy; 15th November 2017, 17:20.

                                    Comment


                                      Originally posted by stealthflanker View Post
                                      Well two possible reason i could think of.

                                      1.Counter stealth, maximizing detection range against small target.. China have lots of cruise missile (Russia, India, Japan, Korea, Vietnam and of course US) and stealth user around. small power aperture product for fighter aircraft is not acceptable. By aiming largest possible aperture it allows maximizing detection range without expensive investment for TRM power.

                                      2. Stealth. You can have large radome But, the antenna diameter would be constrained by the edge treatment to reduce structural mode RCS. The edge would need to be treated by 4 wavelengths of your lowest threat frequency. S band is not practical in this respect as it need 40 cm width edge treatment. Possible treatment would be C (5GHz) down to X band. If the threat frequency is X-band. That 1.2 m width radome can accommodate 90 cm diameter antenna. larger antenna is possible but edge treatment will suffer as it have to be designed for higher threat frequency.

                                      Example for JSF.

                                      [ATTACH=CONFIG]256999[/ATTACH]
                                      Another possibility is simply measurement error. A variance of one or two pixels can yield dramatic differences at these resolutions and scales, especially if we're haggling over cm^2 worth of differences.

                                      Comment


                                        Thing is, RCS thickness is constant, ignoring scale. A bigger aperture requires more RAM, true, but the thickness lost to RAM is less in terms of percentages.

                                        This is another possibility:



                                        I've been measuring the radome from the satellite image at 30 pixels. The banded area is strange; if it corresponds to the black area on the F-35's radome, then it's the actual beginning of the radome and we get 33 pixels instead, giving us a nice comfortable 1.41 meters width.

                                        As to why the J-20 emphasizes radar, larger radars are supposed to be able to jam smaller radars. The APG-81 has a diameter of about 725mm, while the J-20's radar ranges from 950mm to 1050mm. If the technology level is the same, the J-20's radar should be able to transmit twice the power.

                                        Comment


                                          @latenlazy: doing it from multiple methods (drone pictures, telephoto pictures), you get roughly in the 1.25 to 1.3 meter range. See this picture, for instance. Use the 12.88 figure, measure the radome versus the wingspan, and you get about 1.31 meters of radome length.

                                          Comment


                                           

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