Chengdu J-20 news and analysis Part III

Deino said:
TomcatViP said:
Well, if you ask me, the plane we can see at the last airshow look clearly to be light weight.

You can also notice a roll instability in some manoeuvre. Something that would limit airframe max mass (mass = alpha, alpha aggravates roll departure).
Click to expand...


This one? ... but I'm not sure if it is an instability.

在见到J20之前我没想过一架飞机还能这样飞_哔哩哔哩_bilibili

在见到J20之前我没想过一架飞机还能这样飞共计2条视频，包括：在见到J20之前我没想过一架飞机还能这样飞、当天拍的其它一些J20视频（渣拍摄，见谅）等，UP主更多精彩视频，请关注UP账号。
www.bilibili.com www.bilibili.com


By the way ... an impressive image that shows the J-20 is NOT that huge as some still claim.

View attachment 687205
Click to expand...
I don't know, but the picture seems to me to be an optical illusion.
The J-20 is supposed to be 21.2 meters long.
The Su-30/J-16 21.935 meter.
 
Deino said:
Finally officially confirmed!!

A J-20 fitted with WS-15 has already taken its maiden flight. Apparently the speaker in that video is a famous academician from the Chinese Academy of Engineering. He is allegedly specialized in turbofan engines.

Video by @星辰大海SLC on Bilibili.

https://twitter.com/x/status/1602687065749131271
View: https://twitter.com/Nickatgreat1220/status/1602687065749131271
Click to expand...

What’s funny is that the news leaked in late November but no one even talked about it.
 
It appears to state that the thrust-to-weight ratio of Chinese 3rd generation (analogous 4th generation by Western definition) turbofans is 8, while for the 4th generation (analogous to 5th generation by Western definition) is 10, and for the next generation is 15.
 
Geo said:
Deino said:
Finally officially confirmed!!

A J-20 fitted with WS-15 has already taken its maiden flight. Apparently the speaker in that video is a famous academician from the Chinese Academy of Engineering. He is allegedly specialized in turbofan engines.

Video by @星辰大海SLC on Bilibili.

https://twitter.com/x/status/1602687065749131271
View: https://twitter.com/Nickatgreat1220/status/1602687065749131271
Click to expand...

So the WS-15 is the 4th gen with T/W = 10? Or?
Click to expand...

That appears to be the case, yes.
 
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
No, the thrust-weight ratio is only one of the characteristics, not decisive.

The T/W of the engine is linked to the supersonic cruise capability, and it also shows the differences in aviation technology of different generations of fighters, so T/W of engine is regarded as one of the main differences between different generations. However, although it is one of the characteristics, it does not mean that it is the decisive condition.

Just like today, although J-20 using FWS-10 engines with T/W of 8, we still think it is a standard fifth-generation fighter.
 
New prototype no. 2051 spotted with some major changes to the area behind the canopy or canopy itself.

Allegedly the rear section behind the cockpit received some refinements similar to the J-35's different spine to reduce drag and improve transonic performance.

Also, some say this might be the variant powered by the WS-15, even if according to eyewitnesses it still uses WS-10C engines.

9E737310-9148-4E56-8360-1E00909E2C7F.jpeg AAF3DBED-D6BC-4AEA-80FA-D501C8F21D50.jpeg
 
Deino said:
New prototype no. 2051 spotted with some major changes to the area behind the canopy or canopy itself.

Allegedly the rear section behind the cockpit received some refinements similar to the J-35's different spine to reduce drag and improve transonic performance.

Also, some say this might be the variant powered by the WS-15, even if according to eyewitnesses it still uses WS-10C engines.

View attachment 689980View attachment 689981
Click to expand...

First J-20 with WS-15 engines if true? That will boost the performance by quite a lot I would imagine Deino, I would also tend to think that any further J-20s fitted out with the WS-15 will be able to supercruise as well something that they were lacking on previous models.
 
Here's already a first side profile available for comparison: On top prototype no. 2051 aka eventually J-20B and on the bottom the regular J-20A.
J-20A vs J-20B maybe aka 2051.jpg

321495068_685697296546480_6262719345246594800_n.jpg
 
Last edited:
FighterJock said:
Deino said:
New prototype no. 2051 spotted with some major changes to the area behind the canopy or canopy itself.

Allegedly the rear section behind the cockpit received some refinements similar to the J-35's different spine to reduce drag and improve transonic performance.

Also, some say this might be the variant powered by the WS-15, even if according to eyewitnesses it still uses WS-10C engines.

View attachment 689980View attachment 689981
Click to expand...

First J-20 with WS-15 engines if true? That will boost the performance by quite a lot I would imagine Deino, I would also tend to think that any further J-20s fitted out with the WS-15 will be able to supercruise as well something that they were lacking on previous models.
Click to expand...

What engine does the bulk of the existing J20 fleet use? I've seen different versions of the WS-10 and AL-31 mentioned in stuff online but it isn't clear which replaced what when or what the bulk of the production models fly with.
 
Deino said:
Here's already a first side profile available for comparison: On top prototype no. 2051 aka eventually J-20B and on the bottom the regular J-20A.
View attachment 689989

321495068_685697296546480_6262719345246594800_n.jpg
Click to expand...

Smart images, I notice that the J-20B has a much bigger area behind the cockpit than the regular J-20A, any ideas as to the purpose of the space?
 
Josh_TN said:
FighterJock said:
Deino said:
New prototype no. 2051 spotted with some major changes to the area behind the canopy or canopy itself.

Allegedly the rear section behind the cockpit received some refinements similar to the J-35's different spine to reduce drag and improve transonic performance.

Also, some say this might be the variant powered by the WS-15, even if according to eyewitnesses it still uses WS-10C engines.

View attachment 689980View attachment 689981
Click to expand...

First J-20 with WS-15 engines if true? That will boost the performance by quite a lot I would imagine Deino, I would also tend to think that any further J-20s fitted out with the WS-15 will be able to supercruise as well something that they were lacking on previous models.
Click to expand...

What engine does the bulk of the existing J20 fleet use? I've seen different versions of the WS-10 and AL-31 mentioned in stuff online but it isn't clear which replaced what when or what the bulk of the production models fly with.
Click to expand...

WS-10s

J-20 production fully switched to WS-10 in mid 2019.
 
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
 
F119Doctor said:
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
Click to expand...
What makes you think that the WS-15 will have poor dry thrust in the supercruise envelope.
 
F119Doctor said:
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
Click to expand...

T/W ratio just happens to be one of the convenient and simple ways for that paper to describe the next generation engine for 5th generation fighters, I am sure that you've read the paper and that among the other attributes it describes is that the engine is meant to be capable of attaining supercruise without afterburner on an intended aircraft.

I'm not sure how that would lead you to believe that the goal of the engine was to attain a T/W ratio of 10 at the expense of everything else.
 
latenlazy said:
F119Doctor said:
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
Click to expand...
What makes you think that the WS-15 will have poor dry thrust in the supercruise envelope.
Click to expand...
I’m not saying that it will have poor supercruise performance with a 0.25 bypass ratio, although there is more to supercruise performance than just low bypass ratio.

I’m saying that the compromises needed to achieve a 10:1+ T/W with supercruise performance are likely to result in a very unreliable short lived engine, taking many more years of development and invention before it is suitable for fleet use.
 
F119Doctor said:
latenlazy said:
F119Doctor said:
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
Click to expand...
What makes you think that the WS-15 will have poor dry thrust in the supercruise envelope.
Click to expand...
I’m not saying that it will have poor supercruise performance with a 0.25 bypass ratio, although there is more to supercruise performance than just low bypass ratio.

I’m saying that the compromises needed to achieve a 10:1+ T/W with supercruise performance are likely to result in a very unreliable short lived engine, taking many more years of development and invention before it is suitable for fleet use.
Click to expand...
We’ve seen 4th gen single crystal turbine blades displayed at air shows as far back as 2018 so I’m not sure you’re quite up to date with the technologies there ;)
 
latenlazy said:
F119Doctor said:
latenlazy said:
F119Doctor said:
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
Click to expand...
What makes you think that the WS-15 will have poor dry thrust in the supercruise envelope.
Click to expand...
I’m not saying that it will have poor supercruise performance with a 0.25 bypass ratio, although there is more to supercruise performance than just low bypass ratio.

I’m saying that the compromises needed to achieve a 10:1+ T/W with supercruise performance are likely to result in a very unreliable short lived engine, taking many more years of development and invention before it is suitable for fleet use.
Click to expand...
We’ve seen 4th gen single crystal turbine blades displayed at air shows as far back as 2018 so I’m not sure you’re quite up to date with the technologies there ;)
Click to expand...
Pratt & Whitney introduced single crystal turbine airfoils in the early 1980s with the F100-220 engine. Yet supercruise wasn’t a reality until the F119, and I know exactly how much it weighs (I could tell you but the. I would have to kill you )
 
F119Doctor said:
latenlazy said:
F119Doctor said:
latenlazy said:
F119Doctor said:
Sevrent said:
interesting. This old Chinese paper from 2003 that discusses the development of what led to the J-20. These same numbers show up as well. They describe 4th gen fighters as having engines with a T/W of 8. and Fifth gen fighters as having a T/W of 10. Seems like it's a goal/benchmark by which they differentiate generations?

(Page 4)
Click to expand...
Focusing on T/W of 10+ is probably the downfall of both the Russian IZD30 and the Chinese WS15. Non AB performance in the supercruise envelope is more important than raw T/W. Big cores for low bypass ratio / supercruise thrust are not lightweight. Trying to push high T/W and supercruise may be well beyond the state of the art, at least for them.
Click to expand...
What makes you think that the WS-15 will have poor dry thrust in the supercruise envelope.
Click to expand...
I’m not saying that it will have poor supercruise performance with a 0.25 bypass ratio, although there is more to supercruise performance than just low bypass ratio.

I’m saying that the compromises needed to achieve a 10:1+ T/W with supercruise performance are likely to result in a very unreliable short lived engine, taking many more years of development and invention before it is suitable for fleet use.
Click to expand...
We’ve seen 4th gen single crystal turbine blades displayed at air shows as far back as 2018 so I’m not sure you’re quite up to date with the technologies there ;)
Click to expand...
Pratt & Whitney introduced single crystal turbine airfoils in the early 1980s with the F100-220 engine. Yet supercruise wasn’t a reality until the F119, and I know exactly how much it weighs (I could tell you but the. I would have to kill you )
Click to expand...
4th gen single crystals are not 1st gen single crystals.
 
It’s not simply a matter of single-crystal airfoils for turbines. An engine designed for supercruise like the F119 has a large core as a result of low bypass ratio and high specific thrust. Even given comparable states of metallurgy technology, such a design isn’t lightweight for its size, and if the Chinese goal is a thrust/weight of 10+, that may be at the cost of the engine’s lifespan.

The F135 achieving a higher thrust/weight ratio is likely because of the larger fan increasing its bypass ratio, while the core size remains about the same as the F119 that it was derived from. It’s also not optimized for supercruise like the F119 is.
 
icyplanetnhc (Steve) said:
It’s not simply a matter of single-crystal airfoils for turbines. An engine designed for supercruise like the F119 has a large core as a result of low bypass ratio and high specific thrust. Even given comparable states of metallurgy technology, such a design isn’t lightweight for its size, and if the Chinese goal is a thrust/weight of 10+, that may be at the cost of the engine’s lifespan.

The F135 achieving a higher thrust/weight ratio is likely because of the larger fan increasing its bypass ratio, while the core size remains about the same as the F119 that it was derived from. It’s also not optimized for supercruise like the F119 is.
Click to expand...

I'm not sure why people are talking about the TWR of the engine as "10+"

It's described in the paper as just 10 (I would know, because I'm the one who bloody translated the thing and wrote the English language pdf for the diplomat and the associated commentary article for it), and while that is technically higher than that of F119 it is also lower than that of F135.


We don't know what the final requirements for WS-15 are in terms of things like TWR, thrust, lifespan etc, but if the argument against the possibility of a WS-15 having a TWR 10, being supercruise capable, without compromising lifespan (relative to if its TWR was say, 9 like that of F119), then that just strikes me as suggesting because F119 and F135 happen to not tick those same boxes in the relative manner that it is inherently technologically more advanced or difficult and thus compromises would be made elsewhere.

And for the record, over the years we've heard TWR goals of 9-10 for WS-15 anyway.
 
icyplanetnhc (Steve) said:
It’s not simply a matter of single-crystal airfoils for turbines. An engine designed for supercruise like the F119 has a large core as a result of low bypass ratio and high specific thrust. Even given comparable states of metallurgy technology, such a design isn’t lightweight for its size, and if the Chinese goal is a thrust/weight of 10+, that may be at the cost of the engine’s lifespan.

The F135 achieving a higher thrust/weight ratio is likely because of the larger fan increasing its bypass ratio, while the core size remains about the same as the F119 that it was derived from. It’s also not optimized for supercruise like the F119 is.
Click to expand...
I’m well aware that it’s not just about fan blade materials. The main point is that China’s materials for jet engines are much further along than people here seem to believe. What you think is the “comparable state” may actually not be the case.
 
Deino said:
Here's already a first side profile available for comparison: On top prototype no. 2051 aka eventually J-20B and on the bottom the regular J-20A.
View attachment 689989

321495068_685697296546480_6262719345246594800_n.jpg
Click to expand...

So it was finally realised that the J-20 is not good at dog fighting, and thus the pilot need not have good backward visibility. And it may have additional advantage of reducing drag with the newer canopy design .....
 
zjz said:
Deino said:
Here's already a first side profile available for comparison: On top prototype no. 2051 aka eventually J-20B and on the bottom the regular J-20A.
View attachment 689989

321495068_685697296546480_6262719345246594800_n.jpg
Click to expand...

So it was finally realised that the J-20 is not good at dog fighting, and thus the pilot need not have good backward visibility. And it may have additional advantage of reducing drag with the newer canopy design .....
Click to expand...
…the J-20 has a 360 distributed sensor system.
 
zjz said:
Deino said:
Here's already a first side profile available for comparison: On top prototype no. 2051 aka eventually J-20B and on the bottom the regular J-20A.
View attachment 689989

321495068_685697296546480_6262719345246594800_n.jpg
Click to expand...

So it was finally realised that the J-20 is not good at dog fighting, and thus the pilot need not have good backward visibility. And it may have additional advantage of reducing drag with the newer canopy design .....
Click to expand...
Sorry, what a strange conclusion.., but if you want to find a reason for anything you always find one!
 

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