Chengdu J-20 5th Generation Aircraft News & Discussions

[Figaro]

Perhaps someone can reference Dr. Song's 2000 paper on this subject? If anything, his analysis of the J-20s aerodynamics should be the most authoritative one on here ...

 

[vi-va]

Perhaps someone can reference Dr. Song's 2000 paper on this subject? If anything, his analysis of the J-20s aerodynamics should be the most authoritative one on here ...

一种小展弦比高升力飞机的气动布局研究.pdf

宋文骢 Song Wencong
Song Wencong (Chinese: 宋文骢; 26 March 1930 – 22 March 2016) was a Chinese aircraft designer, who was responsible for the development of the single seat version of the Chengdu J-10.[1] He was a member of the Chinese Academy of Engineering.

A Research on the Aerodynamic Characteristics of a Small Aspect Ratio, High Lift Fighter Configuration
Song Wencong, Xie Pin, Zheng Sui, Li Yupu ( Chengdu A ircr af t Design & Research I nstitute, Chengdu 610041, China)

[ Abstract] Focused on the features of stealth, supermaneuverability and supersonic cruise of the future fight er, the authors identified the main difficulties and gave some practical solutions to liftdrag characteristics at sub/ transonic speed, high A. O. A. aerody namic performances at low speed and supersonic drag characteris tics. T he authors believed that design g oals could only be achieved by study ing flow principles deeply , digging up the potentials of present aerodynamic improving measures, developing new aerodynamic concepts, adopting interrelated integration and flight control measures and compromising on the multiple desig n points. [Key words] aerodynamic configuration; supersonic cruise; stealth; poststall maneuvers

 

[dbc]

J-20 is NOT a close coupled canard.

I stopped reading after after this...

 

[vi-va]

I stopped reading after after this...

What he said is true. Seems you are the one has little experience and knowledge about jet. Rafale is close canard actually.

J-20 is NOT a close coupled canard.

 

[serenity]

I stopped reading after after this...

Canards can offer unstability and increased drag but for J-20 like Typhoon and Gripen and Rafale, their canards are unloaded. Eurofighter Typhoon and J-20 are similar application of long arm canard and generally should be better for cruising speed turns while the close couple canards like Gripen Rafale and J-10 can generally be better for maneuverability.

It all has to do with pressure at front of wings and their size and geometry too. There are so many details involved here but generally long arm canard application for J-20 makes sense. Anyway all canard modern fighters feature better L/D than conventional because they are all unloaded and aim to achieve low front wing gauge pressures relative to any leading edge. It is quite public knowledge that european canards are all better L/D than conventional tail configuration. Saying add drag is obvious and unimportant. The important question is the detail of L/D. Find some sources saying European canards have poor L/D. They have better lift. Why does Su-33 add canards for extra lift off carrier? Even in this application they achieved overall better lift than drag penalty.

 

[zhxy]

Why didn't China think of developing a single-engine version of the J-20? That was amazing

 

[serenity]

Why didn't China think of developing a single-engine version of the J-20? That was amazing

Single engine has much shorter range and capability unless China has F135 it can use. Maybe after WS15 has 10 years of proven service like WS10, they may put WS15 onto a single engine fighter like J-10 now uses WS10.

I think some people have confusion over what a long arm and close couple is referring to. It is the moment arm along the center of gravity or physical centroid models. Couple refers to the combination of forces to create motion. Close vs long is in the moment arm. At least this is how I understand it with English being second language and my engineering understanding of these mechanics. Perhaps the aerodynamic definitions are different to my assumptions but google indicates Eurofighter is long arm as well. So I suspect I am correct.

Chengdu engineers had problem of no engines in class of F135 anytime until mid 2020s. WS10 and AL-31 upgrades approach the thrust of F119 but we don't know many more important details and I suspect F119 is much more advanced engine than at least the modified high thrust versions of AL-31 and WS10. They focused to reduce weight of aircraft, reduce drag where they can, and improve lift to compensate in this deficiency. I don't know or care how successful they were but they have some claims that lift is excellent and weight is 15 tonnes says some and 18 tonnes says others maybe a matter of equipment and how they measure or define. Anyway it will seem this is light and they created great lift with this body, low drag thanks to internal weapons. Against F-22? Well J-20 wish it has WS15. Honestly more interesting is the J-20's metamaterials and skin.

 

[vi-va]

Single engine has much shorter range and capability unless China has F135 it can use. Maybe after WS15 has 10 years of proven service like WS10, they may put WS15 onto a single engine fighter like J-10 now uses WS10.

I think some people have confusion over what a long arm and close couple is referring to. It is the moment arm along the center of gravity or physical centroid models. Couple refers to the combination of forces to create motion. Close vs long is in the moment arm. At least this is how I understand it with English being second language and my engineering understanding of these mechanics. Perhaps the aerodynamic definitions are different to my assumptions but google indicates Eurofighter is long arm as well. So I suspect I am correct.

F-135 paid a price for higher thrust, which is much higher bypass ratio.
F-135 0.57:1
F-119 0.30:1
F135-PW-100 dry trust 128 kN
F119-PW-100 dry trust 116 kN
China can sacrifice bypass ratio to improve dry trust, but is it what we need?

 

[lcloo]

Video from PLAAF itself.

https://twitter.com/x/status/1270353244011651074

 

[Deino]

Anyone want a laugh??

Here's quite a strange link published by the USAF university:

https://media.defense.gov/2020/Jun/...PCDntgAmy0pwq6ppw5yZCoHGq6gDr12nMoZSPtxAPpJNM

... with a most "interesting"

analogy and strange conclusion:

China has demonstrated an apparent capability to develop stealth fighters. While Chinese aviation technology should not be underestimated, this essay strikes a cautionary note. Using historical examples from Argentina, Egypt, and India, the author contends that Chinese stealth fighters are being unveiled in part to highlight China’s arrival as a global power; however, future Chinese jet fighter development will be hindered by technical challenges such as the development of indigenous engines—not to mention advanced weapons and sensors.

Well ... what relevance do have some historical examples from Argentina, Egypt, and India with China's ability to build stealth fighters??And I'm indeed shocked

since this is really written by someone working for the USAF University!?

It reminds me to a tweet I saw some weeks ago from the US Naval institute.

https://twitter.com/navalinstitute/status/1252246949627125760

Pure pity that they fell to such a low level.

 

[PeacefulWar]

Anyone want a laugh??

Here's quite a strange link published by the USAF university:

https://media.defense.gov/2020/Jun/...PCDntgAmy0pwq6ppw5yZCoHGq6gDr12nMoZSPtxAPpJNM

... with a most "interesting" View attachment 640749 analogy and strange conclusion:



Well ... what relevance do have some historical examples from Argentina, Egypt, and India with China's ability to build stealth fighters??And I'm indeed shocked View attachment 640748 since this is really written by someone working for the USAF University!?

It reminds me to a tweet I saw some weeks ago from the US Naval institute.

https://twitter.com/navalinstitute/status/1252246949627125760

Pure pity that they fell to such a low level.

Argentina, Egypt, and India
The author try hard to avoid historical examples from China itself

 

[samsara]

Anyone want a laugh??

Here's quite a strange link published by the USAF university:

https://media.defense.gov/2020/Jun/...PCDntgAmy0pwq6ppw5yZCoHGq6gDr12nMoZSPtxAPpJNM

... with a most "interesting" View attachment 640749 analogy and strange conclusion:



Well ... what relevance do have some historical examples from Argentina, Egypt, and India with China's ability to build stealth fighters??And I'm indeed shocked View attachment 640748 since this is really written by someone working for the USAF University!?

It reminds me to a tweet I saw some weeks ago from the US Naval institute.

https://twitter.com/navalinstitute/status/1252246949627125760

Pure pity that they fell to such a low level.

When one sees more messages like these, then one knows they are facing difficulties to lead… and the confidence is diminishing.

 

[Figaro]

Anyone want a laugh??

Here's quite a strange link published by the USAF university:

https://media.defense.gov/2020/Jun/...PCDntgAmy0pwq6ppw5yZCoHGq6gDr12nMoZSPtxAPpJNM

... with a most "interesting" View attachment 640749 analogy and strange conclusion:



Well ... what relevance do have some historical examples from Argentina, Egypt, and India with China's ability to build stealth fighters??And I'm indeed shocked View attachment 640748 since this is really written by someone working for the USAF University!?

It reminds me to a tweet I saw some weeks ago from the US Naval institute.

https://twitter.com/navalinstitute/status/1252246949627125760

Pure pity that they fell to such a low level.

Hopefully the top brass of the Pentagon does not share this mindset in the slightest ... otherwise I worry for the US military. Underestimating the Japanese in the early stages of WW2 and the Vietnamese air force proved extremely costly ...

 

[riscol]

How can US call itself an industrious super power when it cannot compete with Siemens, Alstom, Toshiba, ZTE, Huawei, TSMC and need to use unfair practices to punish them, throwing executives in jail, forcing them to admit crimes they did not commit and forcing Alstom to sell to US. Since this is about stealth fighters the only way to belittle China is to call the J-31 a copy of F-35 and China lacking the capability to develop a true 6th gen fighters and advanced weapons, sensors and indigenous engine . The nonsense gets more intensified as China is an opponent the US cannot militarily defeat or contain.

 

[obj 705A]

So I actually took the time to read this report (obviously not all of it but the main parts) & here is a summary:-
He says the Argentian & Egyptian projects (called Pulqui-II & Ha-300 respectively) failed because they had poor management, there were constant disagreements between the foreign designers that they hired & their own local engineers , they did not have clear mission requirements, they were mainly status symbols to give legitimacy to the government & they did not have enough funding & also they failed to export those fighters which exacerbated the cost overruns even more.

For the Indian project the HF-24, it failed because of poor management, over dependence of foreign made parts to the point were the aircraft can barely be said to be indigenous, cost overruns & delays, constant redesign of the aircraft, and finally the aircraft couldn't fulfill it's mission requirements.

Finnaly he talks about China's own fighters & draws parallels between China's own program & those of the aforementioned three countries, he says China is developing those fighters to serve as a status symbol, & he says all of China's operational frontline fighters exclusively use Russian engines, he says both the J-31 & J-20 use only Russian engines which means China is still not self-sufficient and thus the aircraft's capability will be limited & it's export potential will be reduced (I presume he means not exporting it will lead to cost overruns), then he says the design & technologies of China's stealth fighters are not integrated with each other well enough for them to be compared to the F-22, F-35.
And finally he says by the time the J-20 , J-31 are produced in large enough numbers after 8-10 years from now, the technologies they are using may become obsolete because aircraft technology is a time sensitive matter.

At the very end he says something that is somewhat contradictory just so that his argument sounds less stupid, he says China will eventually join the elite club of countries that can design & produce their own aircrafts (I assume by "elite club" he means the US ,Russia, France, UK) due to it's financial technological technical expertise, but there will be a lot of obstacles, in other words I assume he means China will only enter the elite club of the US, Russia, France, UK in the far future (not any where near say 15 years from now).