J-20 5th Gen Fighter Thread VI

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Totoro

Major
VIP Professional
I don't mean to dismiss the work you put into the conclusions you drew of course. If possible though, and if you have time, I'd like to see it, or at least hear you run through some of the particulars of what you did.

I can't redo the whole process anytime soon, but it's really something anyone can try on their own. Most of the work is hunting down images of both planes from the same angle. F22's dimensions are known, and J20's are pretty well guesstimated by now. Then one draws fairly precise 3 side drawings for each (or one can use existing ones for f22 as they're pretty precise) Then one needs to think of each plane as a collection of geometric shapes and break down the drawings into pieces. It's several hours of work all in all, but there really is enough images out there covering all sides, so one has a pretty good idea of an overall shape.

Another way to do it, which i haven't used, (if one believes the model makers' planes are made precisely enough) is to simply build the two models of same scale, paint/cover them with something that'd close even the tiniest holes and dip them in a jug of water with very precise measurement marks. Then compare the displaced water volume.
 

latenlazy

Brigadier
I can't redo the whole process anytime soon, but it's really something anyone can try on their own. Most of the work is hunting down images of both planes from the same angle. F22's dimensions are known, and J20's are pretty well guesstimated by now. Then one draws fairly precise 3 side drawings for each (or one can use existing ones for f22 as they're pretty precise) Then one needs to think of each plane as a collection of geometric shapes and break down the drawings into pieces. It's several hours of work all in all, but there really is enough images out there covering all sides, so one has a pretty good idea of an overall shape.

Another way to do it, which i haven't used, (if one believes the model makers' planes are made precisely enough) is to simply build the two models of same scale, paint/cover them with something that'd close even the tiniest holes and dip them in a jug of water with very precise measurement marks. Then compare the displaced water volume.
Well, I figured that's what you ended up doing. By particulars I meant stuff like how did you segment the plane, which geometric shapes did you approximate which sections with, how did you deal with the wings and control surfaces, did you assume a standard thickness for flat parts of the plane or did you attempt to figure out their thickness independently for your measurements, how did you deal with the different tapers of the body along the length of the plane Etc.

With the second method, you can probably use CAD models and feed them into a 3D printer, assuming the material you use is dense enough to sink. Still, the results you get will be contingent on model accuracy.
 
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Air Force Brat

Brigadier
Super Moderator
To assume J-20 is 4 tons lighter than Raptor without reason would be a stretch, but now, there is word from AVIC, the makers of the J-20, that that is the case. I'm not saying the reliability is indisputable, but that coupled with the many posts here that discuss how weight could have been saved (possible 3 ton loss on improved titanium alone, weight loss through DSI, omission of thrust vectoring, etc...) certainly makes the case for the possibility. Don't forget, the J-20 was designed specifically to be able to cope with inferior engines if needed. At this point, from what I can see, the only argument for why the J-20 could not possibly be that light goes along the lines of, "But USA couldn't make it that light 20 years ago! How could anybody do better than a 20-year old American design?" Well, that's called denial, not reasoning LOL Times are changing, and they change faster in China than anywhere else. Call it "extraterrestrial" if you want, but to many, the entirety of China's meteoric rise has seemed quite out-of-this-world.


I'm very glad you brought up the case of the F-15 having a superior TWR than the F-22 but under-performing when compared with the F-22. It shows that you realize that new, superior design can overcome TWR deficit. So how is it that you suddenly believe that there must be a "defiance of the laws of physics" for a 2016 J-20 with less thrust (though not necessarily lower TWR due to massive weight savings from cutting edge Chinese manufacturing techniques) to outperform a 2005 F-22 with more thrust? Seems entirely possible to me given your F-15 vs F-22 example, especially seeing as how the supercomputers used to calculate aerodynamics have had their capabilities evolve exponentially with time.

Now don't get me wrong. F-22's a lovely silver pony, still among the best in the world surely, but to assume that it's superior to a modern 5th gen delta canard made with cutting-edge manufacturing techniques and materials designed with the fastest supercomputers in the world all 20 years later in advancement... well, no need to finish that sentence, to be "kind" back to you.

Thank you for extending that kindness, I really don't need to make apologies for the Raptor, and as for "long lead" projects, the time and money spent on the Raptor were very well spent. There really is only one "Alien Bird!" and it continues to be the most powerful fighter aircraft on the planet, with the lowest RCS, the highest operating altitude, with 8 AAMs, and the highest supercruise of at least 1.6 to possibly 1.8 Mach....

So yes, it did in fact first flight in 1995, and achieved IOC in 2005, and yes there are "only" 183 operational aircraft extant in the world....but each one is very, very capable, as of tonight there are a dozen or so J-20's and not quite that many SU-57s...to that I would add that there are 200 F-35s flying and they are "rolling" off of a very efficient production line!

Taking the lead is always very expensive hard work,,, catching up is,, well its a goal to strive for!

We need not make nebulous claims,,, and the Raptor is a "Heavy Fighter",, the F-35 is a "slightly less Heavy Fighter", with a much great weapons bay volume than aspiring fifth gens,,,, so if those aircraft happen to be a little lighter, with less available thrust dry or in afterburner..

So yes, there is a great deal we do not know here on SDF,,, I did have an enjoyable afternoon conversation with an F-22 pilot this summer,,,, he got a real chuckle out of my "Alien Bird!" analogy! Heh! Heh! Hey!

I can promise you that USAF takes the J-20 very seriously indeed,,,, I can also promise you that PLAAF take the F-22 seriously as well! R-E-S-P-E-C-T is earned Bro, I do respect the J-20
 

manqiangrexue

Brigadier
Thank you for extending that kindness, I really don't need to make apologies for the Raptor, and as for "long lead" projects, the time and money spent on the Raptor were very well spent. There really is only one "Alien Bird!" and it continues to be the most powerful fighter aircraft on the planet, with the lowest RCS, the highest operating altitude, with 8 AAMs, and the highest supercruise of at least 1.6 to possibly 1.8 Mach....
In training, and in American simulations against US/NATO legacy aircraft, maybe. In the real world, compared to newer 5th generation fighters, that remains to be seen. And perhaps we'll never see, nor do we need to.

But I noticed your post no longer has any mention of the topic of J-20's weight. Did you change your mind or did you want to provide some reasoning for why you think that J-20 could not possibly be 15 tonnes despite hearing it from AVIC?
 
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Air Force Brat

Brigadier
Super Moderator
That's done with aerodynamics, as can be inferred from Dr. Song's paper. Even though the J-20 managed to save weight through reduced vertical stabilizers, DSI, material, fabrication, etc, it still has internal weaponsbays and the accompanied mechanisms which are significant contributors to weight. I don't think that an aircraft of J-20's size has the proper structural integrity to maneuver like a fighter if its weight is around 15 metric tons!

You are exactly right, and while it "MIGHT" be possible for the J-20's high zoot construction methods to achieve a 2 to 3% weight reduction over older construction methods,,,, 25 to 40% is absolute and unmitigated nonsense. To suggest that Chinese engineers have been able to achieve that? is suggesting that they have rewritten the laws of physics?? now the F-18 is limited to around 7+ Pos G, while the F-22 is capable of pulling 9+ Pos G's, anyone is able to reduce the weight of any structure by decreasing its "load bearing" limits,,,, but I do doubt the Chinese would do that on their premier 4 Gen fighter...

so its not so much "weight" and see?? pun intended, but more "believe whatever you want to believe", but don't try to sell that here?? really, as Siege has suggested, that's really not going to "fly"...

and I would add that those "ventral fins" add the same amount of weight that a larger vertical stab would give you on each side,,, they really do!
 

Air Force Brat

Brigadier
Super Moderator
In training, and in American simulations against US/NATO legacy aircraft, maybe. In the real world, compared to newer 5th generation fighters, that remains to be seen. And perhaps we'll never see, nor do we need to.

But I noticed your post no longer has any mention of the topic of J-20's weight. Did you change your mind or did you want to provide some reasoning for why you think that J-20 could not possibly be 15 tonnes despite hearing it from AVIC?

NO! I did NOT change my mind, and for you to pretend to be more prescient than the US Military/NATO when it comes to actual intelligence is further evidence that you don't know what you are talking about??

The J-20 like the F-22 is indeed a "heavy fighter", and NO, that's not a figure of speech,,
 

manqiangrexue

Brigadier
NO! I did NOT change my mind, and for you to pretend to be more prescient than the US Military/NATO when it comes to actual intelligence is further evidence that you don't know what you are talking about??

The J-20 like the F-22 is indeed a "heavy fighter", and NO, that's not a figure of speech,,

15 tonnes empty then loaded with lots of fuel and armament counts as a heavy fighter; I agree. I didn't pretend to be more prescient than anybody; I simply said that F-22 is the best in simulations against NATO/US legacy aircraft, but it has never flown against the likes of Su-57 nor J-20... or even Chinese 4th gen fighters data-linked with JY-26 anti-stealth radar for that matter. So. Just because I could beat up all the other kids in my school doesn't make me the world UFC champ, does it? Therefore... the Raptor is the "best" (caveat: limits of the test). Anyway...

You are exactly right, and while it "MIGHT" be possible for the J-20's high zoot construction methods to achieve a 2 to 3% weight reduction over older construction methods,,,, 25 to 40% is absolute and unmitigated nonsense. To suggest that Chinese engineers have been able to achieve that? is suggesting that they have rewritten the laws of physics?? now the F-18 is limited to around 7+ Pos G, while the F-22 is capable of pulling 9+ Pos G's, anyone is able to reduce the weight of any structure by decreasing its "load bearing" limits,,,, but I do doubt the Chinese would do that on their premier 4 Gen fighter...

so its not so much "weight" and see?? pun intended, but more "believe whatever you want to believe", but don't try to sell that here?? really, as Siege has suggested, that's really not going to "fly"...

and I would add that those "ventral fins" add the same amount of weight that a larger vertical stab would give you on each side,,, they really do!

2-3% but not 25%? LOL I'd like to see your calculations since you're giving out numbers. I've also noticed that you've declined to refute any of the actual suggestions here for how J-20 could have lost that weight. They include a documented method to drop 40% weight off titanium welds by 3D printing (credit: latenlazy), liquid metal electromagnetic shaping, metal superplastic forming, (credit: kurutoga), omission of thrust vectoring, DSI weight savings, maybe some more by PLAWolf? Those are just some for you to get started on though. I didn't see you refute a single one; so far your "reasons" for why you don't believe J-20 could be 15 tonnes, sounds like, "Noooo, no, nah, nope, uh-uh, can't be true cus I don't (wanna) believe it; that's too good. We have word from AVIC? I don't care; my friend seigecrossbow here is a better source on J-20 than AVIC cus he agrees with me." That sounds like denial to me, Brat. Unless your bit about the G-force was somehow supposed to be reasoning? In which case, you'd need to show calculations for why 15 tonnes with NEW construction and engineering methods couldn't possibly be strong enough to sustain whatever G-limit you think J-20 has (cus I'm pretty sure that's not public yet either LOL). I hope you know that just because someone achieved something beyond what your training in physics would allow you to comprehend, that does not mean that s/he BROKE the laws of physics LOL. If you were born 200 years ago, you'd likely say that the whole concept of a flying machine that moves faster than sound itself violates the laws of physics.
 
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latenlazy

Brigadier
40% is only for parts of the aircraft, not for the whole aircraft.
"And if the forged titanium parts on an American F-22 were made using the Chinese 3D printing technology, around 40 percent of the weight can be reduced."

Yes, but most of the F-22's frame is forged titanium, and of the 40% of the F-22 that uses titanium by weight I imagine the frame takes most of that share.
 
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