J-20 5th Gen Fighter Thread VI

[manqiangrexue]

Jobjed's translated a few posts from an insider whose statements I think sound reasonable.
https://www.sinodefenceforum.com/chinese-engine-development.t252/page-418#post-440450

WS-10IPE should be a 14 ton engine






Tbh I think it would be better to have nothing in that case.





I believe it would be fair to compare both aircraft at an equal internal fuel percentage, because that would most accurately reflect the mission orientation and the balance of range vs kinematic capability that the designers intended for each respective aircraft to achieve in their respective mission profiles.


The problem IMO is that you are thinking of it as a competition of only "maneuverability" rather than the combination of maneuverabiltiy, speed, endurance/range, that I think can be summed up as "kinematic persistence".
The aircraft's kinematic persistence in turn then interacts with things like sensors and weapons systems and datalinking to derive a final "combat effectiveness" score.

So for J-20 and F-22, at an equal % of internal fuel, hypothetically let's say J-20's "maneuverability" is only 85% that of F-22's, but that J-20's range is 150% that of F-22.

Well in such a scenario, the J-20's kinematic persistence would be somewhere between equal or perhaps even superior to that of J-20.

140kN? Haha I must have mixed up WS-10IPE with WS-10G, something rumored a couple years back to be a saw-toothed 155kN engine. That's the one I think would be great with J-20 and that's the one that likely doesn't exist LOL

Far too complicated for me. I had not even heard of the term "kinematic persistence" up till now. I wasn't even trying to prove which aircraft is more maneuverable since there is not a chance in hell I can tell by looking. Factor in how their systems would try to kill each other and defend themselves, and it's far beyond the abilities of anyone here and possibly in the world to decipher. My point was so simple as this:

If our only figure for J-20's empty weight was correct, that means that J-20 has a highly competitive TWR even with its current engines and thus no one can rule out a supermaneuverable J-20 based on low TWR/ inadequate engines.

That's all

 

[manqiangrexue]

I'm no expert, but after reading manqiangrexu's explanation, I'd tend to agree with it. If, and only if, the J-20 is indeed having an empty weight of 15-plus metric tons, then we should deduce that armaments being equal with the F-22, then the J-20 should naturally have an "engagement" weight that is less than the F-22.

An analogy would be a Formula-1 race car. They always calibrate their fuel to last no more than a couple laps after the finishing line. Anything more than that would be extremely bad fuel management on their part.

Not only a lighter engagement weight, but greater engagement TWR than F-22, overcoming J-20's weakness of "under-powered" engines just as Dr. Song set out to do.

 

[Blitzo]

140kN? Haha I must have mixed up WS-10IPE with WS-10G, something rumored a couple years back to be a saw-toothed 155kN engine. That's the one I think would be great with J-20 and that's the one that likely doesn't exist LOL

Far too complicated for me. I had not even heard of the term "kinematic persistence" up till now. I wasn't even trying to prove which aircraft is more maneuverable since there is not a chance in hell I can tell by looking. Factor in how their systems would try to kill each other and defend themselves, and it's far beyond the abilities of anyone here and possibly in the world to decipher. My point was so simple as this:

Well the phrase is one I literally just came up with, so it makes sense that you haven't heard it before lol.

The point I'm trying to make is that if we are trying to compare something like maneuverability of two aircraft, it should not be done in a vacuum where we do not consider other aspects of their design that may sacrifice certain aspects to accentuate other areas of performance. Considering the maneuverability of two aircraft without considering how much fuel each has to maneuver in the first place is IMO a futile exercise.

If our only figure for J-20's empty weight was correct, that means that J-20 has a highly competitive TWR even with its current engines and thus no one can rule out a supermaneuverable J-20 based on low TWR/ inadequate engines.

That's all

But that is the problem -- there is a lot of reason to believe that our only figure for J-20's empty weight may not be correct, meaning any T/W ratio derived from it should not be seriously considered in the first place.

So as I wrote in my previous post -- it is better for us to pretend that the 15 ton empty weight number doesn't exist, until we get indications that such a number is true.

 

[manqiangrexue]

Well the phrase is one I literally just came up with, so it makes sense that you haven't heard it before lol.

The point I'm trying to make is that if we are trying to compare something like maneuverability of two aircraft, it should not be done in a vacuum where we do not consider other aspects of their design that may sacrifice certain aspects to accentuate other areas of performance. Considering the maneuverability of two aircraft without considering how much fuel each has to maneuver in the first place is IMO a futile exercise.





But that is the problem -- there is a lot of reason to believe that our only figure for J-20's empty weight may not be correct, meaning any T/W ratio derived from it should not be seriously considered in the first place.

So as I wrote in my previous post -- it is better for us to pretend that the 15 ton empty weight number doesn't exist, until we get indications that such a number is true.

LOL Shit, I thought I learned a new phrase, kinematic persistence, today...

We do have indication that J-20 is 15-16 tonnes; we just don't have official confirmation. Thus I've already put the caveat into my statement in bold and I have noted that it is far from guaranteed to be true. Beyond that, if you think this thought experiment is not worth participating in, that's understandable, but within the parameters that I have set forth, it is what it is, for whomever wants to consider it.

 

[latenlazy]

Just to comment on the WS-15 a bit, we know that some preliminary documentation for a design called the ywh-30-27, which is believed to be the WS-15 or at least what it was based on, was theoretically specced at 110 kN dry thrust and 175 kN wet thrust. There’s going to be some questions about whether they were able to achieve these targets during development but, given some of the technical advances that have trickled through the news on China’s overall technological base regarding engines, I think there’s also a question of whether the WS-15 might end up being more advanced than its preliminary specs. Given these factors, a 180 kN engine doesn’t sound outlandish to me.

 

[Blitzo]

LOL Shit, I thought I learned a new phrase, kinematic persistence, today...

We do have indication that J-20 is 15-16 tonnes; we just don't have official confirmation. Thus I've already put the caveat into my statement in bold and I have noted that it is far from guaranteed to be true. Beyond that, if you think this thought experiment is not worth participating in, that's understandable, but within the parameters that I have set forth, it is what it is, for whomever wants to consider it.

IMO I would doubt if the 15 ton class empty weight even constitutes an "indication".

"Indication" in PLA watching would suggest a piece of information that is like a rumour but from a reliable source.
The problem is that the threshold for something to constitute an "indication" depends on the source and the claim itself.

For example, I consider "specification" claims (like weight, thrust, power output etc) with a higher degree of vigilance than other claims like whether a new ship has begun construction or not. Claims are put into greater suspicion if they come out with numbers or claims that sound difficult to believe -- for example if there was a rumour that Bohai had begun to build three 09V SSNs due for launch by next year, I would consider that very skeptically.

In this case, the 15 ton empty weight claim is not only rather difficult to believe, but it is also coming from a source whose reliability is at best dubious.


That is why I do not consider it to be even an "indication" but rather just another rumour without a solid backing yet, and why I think it should best be ignored at this stage.

 

[Air Force Brat]

I see you say 20-21 tons, now 19 tons, so what exactly are you speculating? Seems you don't really know. Sources say F-22 is 19.7 tonnes and J-20 is 15-16 tonnes. Seems now that you don't wanna believe either and want to make up your own with constantly fluctuating guesses??

If J-20 is 20% titanium while F-22 is 40%, that means J-20 uses much greater amount of composites, which are even greater at saving weight. In other words, it's even more drastic than if both were 40% titanium and J-20's titanium structures were 40% lighter. 40% of 40% of 19.7 tonnes is already over 3 tonnes. But as you said, J-20 is more composite so the savings right there are greater than just over 3 tonnes. What about J-20's composite vs. F-22's composite weight? Are we to believe that China had only improved titanium construction but not composite construction at all? I dunno; can't really say without sources but is that normal to improve so much in 1 area of construction (making 20% of your jet) while ignoring another (80% of your jet)? Now consider that F-22's engines are heavier AND its thrust vectoring nozzles don't exist on J-20 so it's purely weight added. Does J-20 have a gun? Don't know.

F-22 is shorter; if there is data showing that it is less voluminous than J-20 then we should certainly note that. However, less voluminous does not necessarily mean less massive since J-20's fuel tanks are known to be larger than F-22's. With larger fuel tanks, if the fight is near, they don't have to be filled fully but that's talking about operation weight rather than empty weight.

There are some other things that more knowledgeable members pointed out as weight-saving measures that I can't dig up right now but after hearing all that reasoning, and considering that this is only what us laymen could come up with, I see no reason that a true master engineering team could not achieve this or greater.

Ships and Aircraft are "always" classified by their maximum gross weight, not by empty weight or half empty weight... Siege's logic and reason are extremely sound and grounded in the actual known gross weight of the F-22..the J-20 being an additional meter or three longer that the F-22, and only 20% Titanium by admission leads to the far more logical conclusion, that the J-20 is at least as heavy as the F-22..

In addition, given that both the dry thrust and wet thrust of the F-22 are likely 20% or so greater than the AL-31FNs of the J-20, we can very safely conclude that the F-22's performance is substantially higher than the performance of the J-20. In actuality the Raptor has a higher rate of climb than the F-15, which actually has a higher thrust to weight ratio than the F-22.

You're ready embrace of a rumour that the J-20 is 15 tonnes, stands contrary to reason, and contrary to known construction methods and practices? then you have the temerity to question Siege,, who is known for honesty and integrity! (why he was choosen as a moderator) he is in fact the "more knowledgeable member,,, Heh! HEH!

 

[Air Force Brat]

The weight you give for both is their empty weight, more relevant would be combat weight or even MTOW. I suspect J-20 to have a similar if not higher MTOW than F-22.

Exactly!, Mr. Blitzo!

 

[latenlazy]

IMO I would doubt if the 15 ton class empty weight even constitutes an "indication".

"Indication" in PLA watching would suggest a piece of information that is like a rumour but from a reliable source.
The problem is that the threshold for something to constitute an "indication" depends on the source and the claim itself.

For example, I consider "specification" claims (like weight, thrust, power output etc) with a higher degree of vigilance than other claims like whether a new ship has begun construction or not. Claims are put into greater suspicion if they come out with numbers or claims that sound difficult to believe -- for example if there was a rumour that Bohai had begun to build three 09V SSNs due for launch by next year, I would consider that very skeptically.

In this case, the 15 ton empty weight claim is not only rather difficult to believe, but it is also coming from a source whose reliability is at best dubious.


That is why I do not consider it to be even an "indication" but rather just another rumour without a solid backing yet, and why I think it should best be ignored at this stage.

Skepticism is in order, but it wouldn’t be the first time we were given indication that significant effort was put into weight reduction for the J-20. As I mentioned earlier, I’m not sure we should dismiss a figure out of hand simply because it sounds incredulous. While we don’t know about the reliability of the original source to the 15 tonne claim, that source was also not typical of what we’d usually find in a transparently bad source.

 

[manqiangrexue]

Ships and Aircraft are "always" classified by their maximum gross weight, not by empty weight or half empty weight... Siege's logic and reason are extremely sound and grounded in the actual known gross weight of the F-22..the J-20 being an additional meter or three longer that the F-22, and only 20% Titanium by admission leads to the far more logical conclusion, that the J-20 is at least as heavy as the F-22..

In addition, given that both the dry thrust and wet thrust of the F-22 are likely 20% or so greater than the AL-31FNs of the J-20, we can very safely conclude that the F-22's performance is substantially higher than the performance of the J-20. In actuality the Raptor has a higher rate of climb than the F-15, which actually has a higher thrust to weight ratio than the F-22.

You're ready embrace of a rumour that the J-20 is 15 tonnes, stands contrary to reason, and contrary to known construction methods and practices? then you have the temerity to question Siege,, who is known for honesty and integrity! (why he was choosen as a moderator) he is in fact the "more knowledgeable member,,, Heh! HEH!

What was the "extremely sound" logic and reasoning? It looks bigger so it has to be heavier? LOL If you know bicycles like you say, then which is heavier? A 54cm Trek Emonda SLR9 or a 51cm Litespeed T1?

20% titanium is a plus, not a minus. What do you think the other parts are? Lead? LOL The other parts are composite, which are even lighter than titanium. The goal is to minimize alloy use, not maximize it. Otherwise, you could build the whole thing out of titanium and not have any issues. J-20's 20% titanium is far more advanced than F-22's 40%. That you didn't know this really says a lot about how far removed you have become to modern fighter jets since your retirement.

Al-31FN3 is not 20% this or that of F-119. It's about 66% comparing dry thrust, 88% comparing wet thrust, which is why F-22 excels at supercruise. You can't even be bothered with those numbers and I'm supposed to think you can calculate jet performance? Don't be funny...

I don't know if you're old so you forgot or what is it but we had this F-15 vs F-22 conversation before and it's not to your favor. It proves that aircraft design can overcome engine deficiencies, not something you want to argue if you wanted to pretend that F-22 was superior to J-20.

The known construction methods were laid out for you to see many times but you're clearly selectively blind. Chinese 3D printing reduces titanium structure weight by 40%. You've seen this many times with the source too, right? Last time, it shocked you so badly, you fell apart, asking how come F-35 WELDS did not carry the weight savings of 3D PRINTING. You might as well ask if supercomputers can get to 100pf then how come your 2014 Dell can't LOL. But I bet you'll pretend you didn't see it next time too. "Ohhh how could this be? No one in the world could have made any progress since 20 years ago. How could a jet be lighter than Raptor? They couldn't make it in my day so they can't now." That's you forever LOL.

Seige might be honest, but it don't mean he's right. I'm not accusing him of lying; I'm saying his logic is off. Happens to the most honest person in the world. HEEE HEE HO HA