I'm iffy on the cross sectional area, tbh. The F-22's verts are huge, it has larger and thicker tailplanes compared to the J-20's canards, and its wings seem to be thicker too. These differences will add up.
J-20 5th Gen Fighter Thread VI
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I never can understand those who try to ascertain performance ability from poorly recorded videos. Why bother? You're likely wrong if you try to. Only thing about J-20's performance we do know is that it'll be improved with WS-15 unless the new engine weighs much more than it should otherwise.
I actually think China is better in 2010 than US in 1980 in terms of materials and manufacturing process. The technology has developed so much since 1990s. The article quoted 4 or 5 different specific technologies that did not exist in 1980s
Not to mention, advances in modeling probably help with developing lighter weight structures that grant you the same mechanical properties and requirements.
But if this end up in a fighter at least larger than the F-22 but more than 4t lighter is IMO another question (IMO more unlikely).
As I've mentioned before, I have my doubts that the J-20 is actually that much bigger than the F-22 by volume. Could that, combined with modern manufacturing, equate to a 4 ton difference in weight? Unlikely, but we'll see.
EDIT: That said, I just tried a quick thought exercise that might help us make sense of where this 15 tonne empty weight figure comes from. Let's say the F-22 is about 19.5 tonnes. If it's 40% titanium by weight, then its weight in titanium would be about 7.8 tonnes. Now, let's say what we heard a few years back about 3D printed titanium bulkheads is true and the J-20's weight in titanium is 40% lighter relative to the F-22. That alone would make the J-20 3.12 tonnes lighter than the F-22, all else held equal. Is that compelling? ¯\_(ツ)_/¯
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Based on the pilots interviews, it seems the volume was mainly to produce a shape as a design feature to achieve optimal supersonic performances. Unlike the older jets whose volume is based on the things they carry (for that reason their super sonic performance is not comparable to J20). Even in F-35 it seems the stuff it carries decide the shape and volume, not the other way around. My takeaway from the article is some parts of J-20 could be empty under the skin. You can't do a direct volume comparison with older gen jets to estimate the weight.
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Different structural elements and density of material used can dramatically vary the weight. We've heard from alleged ex-F22 engineers about LM using a lot of RAM on the body of the raptor. Older electronics and multirole mission profiles along with heavier engines may contribute to the weight of F-22. Maybe there's a chance J-20 is at a similar or slightly lower weight. Doubt it's a full 4 tonnes lighter though when looking at their respective sizes. J-20 may be "smaller" than the photos suggest but it's certainly larger than the raptor and Su-57.
The J-20 is *longer* than the F-22 and Su-57. That doesn't necessarily make it more voluminous. I'm not saying volume is everything, but if we're going to compare spatial dimensions, we should be careful not to extrapolate greater size in one dimension to mean greater overall spatial dimensions for incongruent shapes.
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Haters love to argue J-20's being longer means massive extra weight, as if the extra section is filled entirely of concrete or something.
A longer fuselage means longer air inlet ducts and weapon bays; basically empty space. When talking about aircraft's empty weight, even interior of fuel tanks counts as empty space.
Keep in mind that J-20 uses DSI. Unlike F-22's intakes, there is no need for diverter and complicated pressure relieve ducts. That saves weight. There is no moving components in DSI either, so there is no weight from movable ramps and extra hydraulic components. Having no thrust-vectoring capabilities also relieve the J-20 from heavy nozzles found on F-22, and Flanker derivatives.
J-20's empty weight being in between that of F-35 and F-22 is pretty reasonable.
A longer fuselage means longer air inlet ducts and weapon bays; basically empty space. When talking about aircraft's empty weight, even interior of fuel tanks counts as empty space.
Keep in mind that J-20 uses DSI. Unlike F-22's intakes, there is no need for diverter and complicated pressure relieve ducts. That saves weight. There is no moving components in DSI either, so there is no weight from movable ramps and extra hydraulic components. Having no thrust-vectoring capabilities also relieve the J-20 from heavy nozzles found on F-22, and Flanker derivatives.
J-20's empty weight being in between that of F-35 and F-22 is pretty reasonable.
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