J-20 5th Gen Fighter Thread VI

[Blitzo]

I regret using the word 'dishonest' in my post. In the second part of that sentence I was referring to the fact that your post came across (to me at least) as "This is how this works. This is what most people think. This is what we should conclude," on an issue that I was actively discussing with latenlazy. Maybe I overreacted. No need to talk about this further.

Okay, no problem.

If you want to talk about issues, feel free to take a look at my two last points addressed at latenlazy; they're about the J-20's weight and some claims that I find unlikely (at least), but have relatively widespread acceptance on this forum. In a way, this is also directly about how sources etc. should work.

Sure, I assume the two points you refer to are included in this passage:

Is it actually 0.5 square meters smaller? Trident found that it's 0.6 square meters larger. Why should we assume that everyone's measurements were biased in one direction and your counterpoints are somehow better? Why didn't any of your warnings about measurement make the point that the error could be in the other direction?

Anyway, my position isn't that the J-20 weighs 25 tonnes. My view is that it most likely has a similar density to the F-22 and is thus proportionally heavier (maybe 21 to 23 tonnes). Some weight reduction might be plausible, but 6+ tonnes isn't (to me). I think the 15 tonne number is an extreme outlier (if you had queried the members here, how many would have volunteered something like it before the article was posted?). In your first reply to me you said that

although jobjed described it as

To conclude, I think Chinese technical claims can be wrong and the 15 tonnes number probably is wrong.

Tbh my original comment #1306 was made mostly in reply to that particular exchange between Latenlazy and yourself.

The 15 ton number might be wrong, might even probably be wrong as well, but at this stage are we confident enough in its potential invalidity to remove it from discussions about J-20 where issues of weight might be relevant, considering the potential validity of the source and indications in past years of supposed advances in weight savings?

For example, is the 15 ton number sufficiently unbelievable that it should be in the same category, as say, claims that J-20 is currently using WS-15, or that J-20 can supercruise at mach 3 or something like that?
Or, should the 15 ton number be kept in circulation, but with the caveat that meaningful skepticism is maintained about its validity, until we get further evidence of what its actual weight may be?

My opinion is it is more in the latter category than the former, though you can disagree.
Putting it another way, my original comment to you was made from the perspective of whether the 15 ton number should be considered worthwhile keeping as a part of discussions or not.

 

[delft]

I find these claims between quite and extremely implausible, but cannot prove that they aren't true. However, consider the reverse: would you be willing to believe an American claim saying that America's least important AESA, smaller and for export only, has equivalent range to J-20's radar?
If China's EMALS program started first, reached every milestone first and was much more open about its progress, would you believe an American claim that theirs was more advanced?
Similarly for the weight issue, if China was on the cutting edge of fighter development for the last 70 years, had four fourth generation designs in service and two stealth planes in service before it's first stealth fighter, would you be willing to believe that the first American stealth fighter, while larger than the first Chinese one, is nearly five tonnes lighter?

I heard years ago and probably from BBC Radio 4 that when Germany industrialized in the nineteenth century the British parliament enacted that German products had to carry the text "Made in Germany" to warn the public that the product they were considering to buy was probably of inferior quality. Not many years later that text signalled to the public that the product was probably of superior quality. We now see US trying to keep their aerospace industry top notch while neglecting to maintain many other parts of their industrial infrastructure and China trying to modernize all of its industries. The Chinese aerospace industry therefore lives in a healthier climate.

 

[delft]

A technical remark:
Assuming a density of the fuselage as a basis for estimating its weight is quite reasonable. However a wing is mostly subject to bending so a thinner wing is likely to be heavier. Also delta wing is lighter than a trapezium wing of the same span and area.

 

[Yodello]

I love the J-20 and being a PLA Fan and Lover, I want the J-20 to be the greatest, strongest, most-feared Fighter in the known Universe. But anyone who wants to discuss the F-35 and JF-17 in the same breath, or even suggest that the JF-17 might be equal or greater to the F-35 in any aspect of Fighter-Jet Metrics, Avionics etc. should get their heads examined...! I can't even believe some people on this Forum have dragged thess two Fighter planes onto the same level. Please lay off the Marijuana or whatever you're high on...! The F-22 and F-35 "SQUADRONS" are at the top of the Food-Chain in Fighter Planes right now...PERIOD.....!!!!! REALITY CHECK...!!! And untill the J-20 gets a dozen squadrons ready and flying, it won't matter if it is 15 tons or 1500 tons...!!!!

 

[manqiangrexue]

I love the J-20 and being a PLA Fan and Lover, I want the J-20 to be the greatest, strongest, most-feared Fighter in the known Universe. But anyone who wants to discuss the F-35 and JF-17 in the same breath, or even suggest that the JF-17 might be equal or greater to the F-35 in any aspect of Fighter-Jet Metrics, Avionics etc. should get their heads examined...! I can't even believe some people on this Forum have dragged thess two Fighter planes onto the same level. Please lay off the Marijuana or whatever you're high on...! The F-22 and F-35 "SQUADRONS" are at the top of the Food-Chain in Fighter Planes right now...PERIOD.....!!!!! REALITY CHECK...!!! And untill the J-20 gets a dozen squadrons ready and flying, it won't matter if it is 15 tons or 1500 tons...!!!!

Why do you always write in outbursts? LOL I'm curious, really, but what is your profession/background and how long have you been a military enthusiast that you're so sure when you state something? Cus I know of senior members who are especially respected for their knowledge on military matters here but aren't sure of the statement so either you know a lot more than them or you're really confident about something that you don't actually understand. The latter is not a good place to be, in life, in general.

First of all, nobody said JF-17 was an equivalent of the F-35. Secondly, a 4th gen fighter like JF-17 or F-16 may be more than F-35 can handle in a dogfight, so that's at least one aspect. Thirdly, someone from NRIET, an institution that actually designs radars, made a statement that their new radar in 2017, could perform like the F-35 radar, which was at this phase roughly 10 years ago. That's a source making a claim that roughly translates to saying that China at least less than 10 years behind the US in radar tech. What information do you have that makes you think you're smarter than this guy or that what he says is impossible? Would NRIET hire you and fire him? LOL What data makes you so confident that you come here telling people what they can and cannot even discuss the possibility of this on a discussion forum? (aside from the fact that JF-17 vs F-35 radar is off topic on J-20 thread)

 

[Tirdent]

Also, let me point out something rather weird:

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This is a Western estimate of the J-20's weight, so we can assume it does not include or consider radical new technologies. It works off 21.5m length with 12.98m wingspan, but seems to include the probe, so actual ratios are approximately 20*13. The estimated empty weight is 34572.2 pounds, or 15800 kg, putting it squarely around the 16000 kg of lower-end estimations.

In the X-35 / F-35 case, the airframe grew about 32% in weight as it moved from prototype to production model. In the YF-22 / F-22 case, the airframe grew about the same percentage. From the YF-17 to the F-18, there was only a 10% weight increase, and what's more, the wingspan increased by about 25%.

So we can make a rough guess that it's the RAM that results in the weight gain, and that without novel manufacturing technologies, the J-20 will weigh around 21.5 tons.

===

At this point, I think it's plausible to believe that the fanboy claim is at least partially correct: the aircraft weighs around 15 tons either with or without RAM. If it is without RAM, the aircraft will likely weigh around 20 tons once RAM is added.

Take that (undergrad) analysis with *liberal* amounts of salt.

It's been around for a while, and was discussed over at Keypublishing at the time. As I pointed out back then, I suspect the weight estimation method used (i.e. the weighting multipliers) is being applied outside its accurate envelope, in that it is not really applicable to 5th generation fighters. Due to internal bays, much increased fuel capacity and (other) RCS reduction measures, 5th generation aircraft are a breed apart in terms of density - I'd wager you'd get a lot less than 19.7t if you were to run the F-22 through it. Using another 5th generation fighter as the benchmark is probably considerably more accurate than a method which is calibrated based exclusively on historical trends in 3rd and 4th generation aircraft.

Do you honestly believe the J-20 will match the C919 in terms of range @ Mach 0.8 & 35000feet (slide #16)? That's precisely what an implausibly low empty weight with a reasonably accurate fuel capacity (= far too favourable fuel fraction, a key influence in the Breguet range equation) will do. And no, they're not assuming 4 external tanks - the paper predates the revelation of that load out by years!

Also, you keep repeating 4t of RAM on the F-22 and a 800kg penalty for a pair of TVC nozzles - how do you arrive at those figures? YF-22 to F-22 weight delta? That number comprises *a lot* more than just RAM (radar, EW, MAWS, data link, almost certainly beefed up structure for increased airframe life and external hardpoints, F119 was heavier & more powerful than YF119...)! While the YF-22 was not quite as much of a bare bones proof of concept as the X-35, this should give you an impression:

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[siegecrossbow]

Take that (undergrad) analysis with *liberal* amounts of salt.

It's been around for a while, and was discussed over at Keypublishing at the time. As I pointed out back then, I suspect the weight estimation method used (i.e. the weighting multipliers) is being applied outside its accurate envelope, in that it is not really applicable to 5th generation fighters. Due to internal bays, much increased fuel capacity and (other) RCS reduction measures, 5th generation aircraft are a breed apart in terms of density - I'd wager you'd get a lot less than 19.7t if you were to run the F-22 through it. Using another 5th generation fighter as the benchmark is probably considerably more accurate than a method which is calibrated based exclusively on historical trends in 3rd and 4th generation aircraft.

Do you honestly believe the J-20 will match the C919 in terms of range @ Mach 0.8 & 35000feet (slide #16)? That's precisely what an implausibly low empty weight with a reasonably accurate fuel capacity (= far too favourable fuel fraction, a key influence in the Breguet range equation) will do. And no, they're not assuming 4 external tanks - the paper predates the revelation of that load out by years!

Also, you keep repeating 4t of RAM on the F-22 and a 800kg penalty for a pair of TVC nozzles - how do you arrive at those figures? YF-22 to F-22 weight delta? That number comprises *a lot* more than just RAM (radar, EW, MAWS, data link, almost certainly beefed up structure for increased airframe life and external hardpoints, F119 was heavier & more powerful than YF119...)! While the YF-22 was not quite as much of a bare bones proof of concept as the X-35, this should give you an impression:

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Congrats on finally getting your account here! Do you want me to fix your username by any chance?

 

[Tirdent]

Thanks! Only if you're sure the previous member with the "correct" username doesn't frequent the forum anymore. It's not a big deal to me

 

[Blitzo]

Congrats on finally getting your account here! Do you want me to fix your username by any chance?

You can do that??!!

Can you fix mine please?

 

[siegecrossbow]

You can do that??!!

Can you fix mine please?

Thanks! Only if you're sure the previous member with the "correct" username doesn't frequent the forum anymore. It's not a big deal to me

Looks like I've overestimated my capabilities... I actually don't have the power to do that. Thought that the new extended moderation feature would let me do it.