Chengdu J-20 5th Generation Aircraft News & Discussions

[serenity]

Alright guys. Let's say J-20 has more easy to observe by radar and missile than F-22 and F-35. Everybody can convinced one way or another but that's all good reasons why canards make J-20 less stealthy. Now we can move to another subject.

 

[Su33KUB]

As you wished...

There are three rules in designing a low radar observable body...

- Control of QUANTITY of radiators
- Control of ARRAY of radiators
- Control of MODES of radiation

They are not so much rules that you can break but more like guidelines that you can have varying degrees of obedience to them.

For example...Of all the basic shapes, the sphere is the most obedient to the three rules.

The sphere is the radar calibration shape and is effective enough that the sphere is in orbit to serve as a calibration object for ground based radars.

https://en.wikipedia.org/wiki/Lincoln_Calibration_Sphere_1

The J-20 have two main wings, two vertical stabilizers, two canards, and two ventral fins. Total of 8 major structures. That falls under rule one: Control of QUANTITY of radiators.

The J-20's flight control structures are not in alignment with each other compares to the F-22. That falls under rule two: Control of ARRAY of radiators.

Rules one and two affects rule three: Control of MODES of radiation.

The J-20 most likely have a higher RCS than the F-35 and F-22.


You can call it a 'bad light' if you want. For those of us who have relevant experience in the subject, we call it balance.

i agree with you but i think the J-20 was designed if it has a similar wing loading to F-35 to be more agile, the Japanese video basically says they sacrificed stealth in exchange for agility, in a head to head encounter the F-35 vs J-20 their RCS maybe are very similar, i think and agree with you F-35 very likely has a lower RCS than J-20, i think the Chinese used canards for high AoA lift requirements, canards do not offer higher lift at low AoA than horizontal tails, they only offer more lift beyond 16 degrees of AoA.


Armed with more missiles the J-20 will be a hard bone to chew in a dogfight against F-35, and more dangerous due to a longer range, in my opinion it was designed like a heavy weight F-35 but the use of canards is to better the F-35 in dogfights, at least once the missiles are depleted, and its wings and radome hint an aircraft designed for higher speeds than the F-35, the canards might even try to offset a higher wing loading than F-35 at high AoA.

 

[Ultima Thule]

i agree with you but i think the J-20 was designed if it has a similar wing loading to F-35 to be more agile, the Japanese video basically says they sacrificed stealth in exchange for agility, in a head to head encounter the F-35 vs J-20 their RCS maybe are very similar, i think and agree with you F-35 very likely has a lower RCS than J-20, i think the Chinese used canards for high AoA lift requirements, canards do not offer higher lift at low AoA than horizontal tails, they only offer more lift beyond 16 degrees of AoA.


Armed with more missiles the J-20 will be a hard bone to chew in a dogfight against F-35, and more dangerous due to a longer range, in my opinion it was designed like a heavy weight F-35 but the use of canards is to better the F-35 in dogfights, at least once the missiles are depleted, and its wings and radome hint an aircraft designed for higher speeds the F-35, the canards might even try to offset a higher wing loading than F-35 at high AoA.

NASA already states that their experimental X-36 with canards was extremely low RCS at all angles, and don't troll if you know nothing about stealth @Su33KUB

 

[Fsjal]

i agree with you but i think the J-20 was designed if it has a similar wing loading to F-35 to be more agile, the Japanese video basically says they sacrificed stealth in exchange for agility, in a head to head encounter the F-35 vs J-20 their RCS maybe are very similar, i think and agree with you F-35 very likely has a lower RCS than J-20, i think the Chinese used canards for high AoA lift requirements, canards do not offer higher lift at low AoA than horizontal tails, they only offer more lift beyond 16 degrees of AoA.


Armed with more missiles the J-20 will be a hard bone to chew in a dogfight against F-35, and more dangerous due to a longer range, in my opinion it was designed like a heavy weight F-35 but the use of canards is to better the F-35 in dogfights, at least once the missiles are depleted, and its wings and radome hint an aircraft designed for higher speeds the F-35, the canards might even try to offset a higher wing loading than F-35 at high AoA.

Considering the size of the J-20, being a heavy fighter it'd probably be assigned by PLAAF mainly in an air-defense interceptor role along with an additional strike-fighter role. Its design including usage of canards means emphasis on maneuverability while its optronics makes it suitable for WVR dogfighting, so no doubt J-20 is a dogfighter but it's more highly likely the J-20 will be assigned for longer-range BVR operations, kinda like how the Su-27 was created as an air-defense fighter in the first place despite its supermaneuverable airframe and addition of IRST.

As for the canards, it's not necessarily a downside for a stealth fighter like the J-20. As mentioned, the X-36 achieved low RCS despite usage of canard (although tbh X-36 lacked vertical stabilizers which increased its stealth while J-20 still uses vertical stabilizers), meanwhile the Typhoon has a flight control software that maintains the angle of the canards where it has the lowest RCS, and then there's the hypothetical navalized F-23 that features canards for high AoA especially for carrier ops.

A shame there's not much information regarding how the J-20 maintains its stealth with its canards. Although tbf J-20 is still a new plane so there's still potential for improvements. A two-seater J-20 would be perfect for both interceptor and strike-fighter role while an improved J-20 with newer avionics and redesigned airframe similar to navalized F-23 would be ideal though it'd be unlikely we'll see a drastically-improved and redesigned J-20 probably until somewhere around ten-to-fifteen years from now..

 

[LKJ86]

Via Weibo

 

[Figaro]

Considering the size of the J-20, being a heavy fighter it'd probably be assigned by PLAAF mainly in an air-defense interceptor role along with an additional strike-fighter role. .

Almost 9 years later and this ignorance still persists. Hopefully you're just trying to troll instead of genuinely believing this what you just stated ...

NASA already states that their experimental X-36 with canards was extremely low RCS at all angles, and don't troll if you know nothing about stealth @Su33KUB

He first trolls the J-10 thread by making repeatedly debunked claims about the Lavi and now he goes on the J-20 thread ... perhaps there is a pattern?

 

[Fsjal]

Almost 9 years later and this ignorance still persists. Hopefully you're just trying to troll instead of genuinely believing this what you just stated ...

Not trolling. The J-20 is a heavy fighter, its weight and size is comparable to the likes of an Su-27. And plus, heavy fighters don't put strong emphasis on dogfighting due to their size. Yes, supermaneuverable heavy fighters exist, the Flanker series and J-20 are those examples, but the reason why even the most supermaneuverable heavy fighters don't place WVR dogfighting as the main emphasis compared to light fighters such as JF-17 or SAAB Gripen is due to their size.

In a hypothetical WVR dogfight between an Su-27 and F-16, the F-16 still has a chance of winning over the Flanker despite the Su-27's IRST and off-boresight R-73 missiles, and this depends all on the skills of an F-16 pilot. If we compare the latest Su-35S to F-16V in WVR dogfight, the Viper can still hold on its own against the Su-35S as thrust vectoring results in low energy state and loss of energy, to which the F-16V can take advantage of due to be an energy fighter.

With the J-20 going up against the F-35 in a hypothetical WVR dogfight, the F-35's small size and optronics means it can keep up with the J-20 in a dogfight scenario. Which is why it's logical for a heavy fighter, especially a heavy stealth fighter like the J-20, to be used more in a long-range BVR aerial combat role. The J-20 has a 45% higher loaded weight than the F-35 along with longer-range and higher AAM payload. Plus the PL-15 has a longer range than the AIM-120C currently used by F-35. In terms of avionics, the F-35 has an advantage especially because of its APG-81, however the J-20's Type 1475 radar, regardless if it's less sophisticated than APG-81 or not, is larger therefore by that virtue would be more powerful. This type of advantage is seen among radars of heavy fighters against smaller radars of lighter-weight fighters, such as N011M Bars of Su-30MKI over N019 Sapfir-29 of MiG-29A, or APG-63(v)1 of F-15C/D over APG-66 of F-16A/B. So really, it's logical for the J-20 being an air-defense missile truck because of its size, range, and ordnance payload.

I don't get why the idea of the J-20 being a heavy air-defense fighter and strike fighter seems so controversial when that's actually the logical conclusion. The F-22A itself basically started off as the former but was later given the additional strike role by carrying precision munitions, though not on the same caliber as F-35. The J-20 is larger than the F-22A, which is fine to rationalize that the J-20 features strike capability as standard like F-35 rather than as an upgraded addition like F-22A. Plus, different unorthodox ideas aren't forms of trolling.

 

[Figaro]

Not trolling. The J-20 is a heavy fighter, its weight and size is comparable to the likes of an Su-27. And plus, heavy fighters don't put strong emphasis on dogfighting due to their size. Yes, supermaneuverable heavy fighters exist, the Flanker series and J-20 are those examples, but the reason why even the most supermaneuverable heavy fighters don't place WVR dogfighting as the main emphasis compared to light fighters such as JF-17 or SAAB Gripen is due to their size.

In a hypothetical WVR dogfight between an Su-27 and F-16, the F-16 still has a chance of winning over the Flanker despite the Su-27's IRST and off-boresight R-73 missiles, and this depends all on the skills of an F-16 pilot. If we compare the latest Su-35S to F-16V in WVR dogfight, the Viper can still hold on its own against the Su-35S as thrust vectoring results in low energy state and loss of energy, to which the F-16V can take advantage of due to be an energy fighter.

With the J-20 going up against the F-35 in a hypothetical WVR dogfight, the F-35's small size and optronics means it can keep up with the J-20 in a dogfight scenario. Which is why it's logical for a heavy fighter, especially a heavy stealth fighter like the J-20, to be used more in a long-range BVR aerial combat role. The J-20 has a 45% higher loaded weight than the F-35 along with longer-range and higher AAM payload. Plus the PL-15 has a longer range than the AIM-120C currently used by F-35. In terms of avionics, the F-35 has an advantage especially because of its APG-81, however the J-20's Type 1475 radar, regardless if it's less sophisticated than APG-81 or not, is larger therefore by that virtue would be more powerful. This type of advantage is seen among radars of heavy fighters against smaller radars of lighter-weight fighters, such as N011M Bars of Su-30MKI over N019 Sapfir-29 of MiG-29A, or APG-63(v)1 of F-15C/D over APG-66 of F-16A/B. So really, it's logical for the J-20 being an air-defense missile truck because of its size, range, and ordnance payload.

I don't get why the idea of the J-20 being a heavy air-defense fighter and strike fighter seems so controversial when that's actually the logical conclusion. The F-22A itself basically started off as the former but was later given the additional strike role by carrying precision munitions, though not on the same caliber as F-35. The J-20 is larger than the F-22A, which is fine to rationalize that the J-20 features strike capability as standard like F-35 rather than as an upgraded addition like F-22A. Plus, different unorthodox ideas aren't forms of trolling.

If AVIC (the owner of Chengdu Aircraft Company) refers to the J-20 an "air superiority fighter", why then are you calling it an interceptor/heavy striker? If you analyze the J-20 closely, you can easily tell that it is not optimized for a heavy strike role at all. Sure the J-20's secondary role could be interception but its foremost role by far is air to air combat. If you have time, I recommend you read Dr. Song's (the J-10's designer) paper which laid out the J-20's aerodynamic base back in 2001.

Alright guys. Let's say J-20 has more easy to observe by radar and missile than F-22 and F-35. Everybody can convinced one way or another but that's all good reasons why canards make J-20 less stealthy. Now we can move to another subject.

I was not aware canards by themselves make aircraft less stealthy. I am aware that there are American stealth aircraft designs incorporating canards (e.g. X-36) which ended up not being selected not due to their lack of stealth. The biggest problem with the J-20's stealth right now is probably its non serrated nozzles ... not its canards.

 

[Su33KUB]

Considering the size of the J-20, being a heavy fighter it'd probably be assigned by PLAAF mainly in an air-defense interceptor role along with an additional strike-fighter role. Its design including usage of canards means emphasis on maneuverability while its optronics makes it suitable for WVR dogfighting, so no doubt J-20 is a dogfighter but it's more highly likely the J-20 will be assigned for longer-range BVR operations, kinda like how the Su-27 was created as an air-defense fighter in the first place despite its supermaneuverable airframe and addition of IRST.

As for the canards, it's not necessarily a downside for a stealth fighter like the J-20. As mentioned, the X-36 achieved low RCS despite usage of canard (although tbh X-36 lacked vertical stabilizers which increased its stealth while J-20 still uses vertical stabilizers), meanwhile the Typhoon has a flight control software that maintains the angle of the canards where it has the lowest RCS, and then there's the hypothetical navalized F-23 that features canards for high AoA especially for carrier ops.

A shame there's not much information regarding how the J-20 maintains its stealth with its canards. Although tbf J-20 is still a new plane so there's still potential for improvements. A two-seater J-20 would be perfect for both interceptor and strike-fighter role while an improved J-20 with newer avionics and redesigned airframe similar to navalized F-23 would be ideal though it'd be unlikely we'll see a drastically-improved and redesigned J-20 probably until somewhere around ten-to-fifteen years from now..

try to understand what gambit said

There are three rules in designing a low radar observable body...

- Control of QUANTITY of radiators
- Control of ARRAY of radiators
- Control of MODES of radiation

add the canard can not shield the wing, the wing does shield the canard in example F-22, aircraft follow rules of physics, the flight control system is designed upon calculations based upon the vectors, constraints the aircraft has.

The F-22 was designed with aft tails simply because they are thinner than the wing thus the wing shields the aft tails reducing the quantity of radiators in a head to head engagement and uses the thrust vectoring nozzles to take over the aft tail in trimming flight pitch moment the aircraft has, J-20 simply went that way because well in reality both aft tails and fore tails increase RCS, so they thought they were sacrificing little for higher gains in mobility, something logic, but the tailless aircraft are the most stealthy albeit they requiere complex systems for roll, pitch and yaw control and they might have reduced controlability.

this pictures says all, basically from a front view F-22 only has 4 radiators, two wings and two vertical tails

this is repeated in other stealth aircraft

 

[CIA Mole]

Can someone introduce me to a good reference on stealth design that talks about these things

 

[Ultima Thule]

try to understand what gambit said

There are three rules in designing a low radar observable body...

- Control of QUANTITY of radiators
- Control of ARRAY of radiators
- Control of MODES of radiation

add the canard can not shield the wing, the wing does shield the canard in example F-22, aircraft follow rules of physics, the flight control system is designed upon calculations based upon the vectors, constraints the aircraft has.

The F-22 was designed with aft tails simply because they are thinner than the wing thus the wing shields the aft tails reducing the quantity of radiators in a head to head engagement and uses the thrust vectoring nozzles to take over the aft tail in trimming flight pitch moment the aircraft has, J-20 simply went that way because well in reality both aft tails and fore tails increase RCS, so they thought they were sacrificing little for higher gains in mobility, something logic, but the tailless aircraft are the most stealthy albeit they requiere complex systems for roll, pitch and yaw control and they might have reduced controlability.

this pictures says all, basically from a front view F-22 only has 4 radiators, two wings and two vertical tails

this is repeated in other stealth aircraft

Reported for trolling @Su33KUB

 

[Figaro]

Reported for trolling @Su33KUB

He was kicked out for trolling from another forum and has now found refuge in this forum ... . Some people can never get enough ...

 

[gambit]

If AVIC (the owner of Chengdu Aircraft Company) refers to the J-20 an "air superiority fighter", why then are you calling it an interceptor/heavy striker?

Air superiority is an assignment, not a design. If I want, I can assign the B-52 to an air superiority role.

That said, an interceptor should be a design where speed is paramount, like the F-104 Starfighter, for example. In a similar vein, an air superiority design should emphasize maneuverability and sensors over speed. Most of what we see ranges in the middle.

I was not aware canards by themselves make aircraft less stealthy. I am aware that there are American stealth aircraft designs incorporating canards (e.g. X-36) which ended up not being selected not due to their lack of stealth. The biggest problem with the J-20's stealth right now is probably its non serrated nozzles ... not its canards.

See post 11837.

Can someone introduce me to a good reference on stealth design that talks about these things

There are none. You learn on-the-job (OJT).

 

[Fsjal]

If AVIC (the owner of Chengdu Aircraft Company) refers to the J-20 an "air superiority fighter", why then are you calling it an interceptor/heavy striker? If you analyze the J-20 closely, you can easily tell that it is not optimized for a heavy strike role at all. Sure the J-20's secondary role could be interception but its foremost role by far is air to air combat. If you have time, I recommend you read Dr. Song's (the J-10's designer) paper which laid out the J-20's aerodynamic base back in 2001.

An air-superiority fighter can still work efficiently as an air-defense interceptor especially when fitted with a heavy long-range radar and armed with BVRAAMs, a reason why I mentioned the J-20 being used in air-defense roles. I agree that the J-20 was designed as an air-superiority fighter, the same with F-22A, however air-superiority fighters are an evolution of interceptors and still retain air-defense capability with the addition of air-supremacy capability, which is why dedicated interceptors aren't particularly common. F-22As from the 90th Fighter Squadron in Alaska are assigned to air patrols and there's the usual news of F-22As intercepting Russian bombers off the Alaskan coast, so it's not far-fetched for the J-20 to be assigned to air patrols off the coast of China. Air intercept, specifically area-defense intercept, is still an air-to-air role, and while air-superiority is a combination of WVR and BVR offensive combat for control of enemy airpsace, area-defense intercept is simply BVR defensive combat for the defense of national airspace. Until China enters into a major war that requires the usage of its J-20s, for now the J-20s would realistically be assigned to routine air patrols with air-superiority being practiced in mock exercises.

As for the strike role, the J-20 can still be upgraded to carrying precision-guided munitions. The F-22A isn't classed as multirole but maintains secondary strike capabilities after being upgraded to carry JDAMs or SDBs. Plus the J-20 has longer range than F-22A, its internal fuel capacity almost comparable to that of F-22A with drop tanks. It's not far-fetched for the J-20 to be upgraded with strike capability, but that's if PLAAF had such need to use the J-20 in deep strike operations.

try to understand what gambit said

Yes I saw it, I have eyes mate. Stop parroting what someone has already said.

 

[gambit]

As for the canards, it's not necessarily a downside for a stealth fighter like the J-20. As mentioned, the X-36 achieved low RCS despite usage of canard (although tbh X-36 lacked vertical stabilizers which increased its stealth while J-20 still uses vertical stabilizers),...

The issue is less about the canards as flight controls elements as it is about rule one: Control of QUANTITY of radiators.

- Control of QUANTITY of radiators
- Control of ARRAY of radiators
- Control of MODES of radiation

Under radar bombardment, if it reflects, it becomes a 'radiator'.

Because of that, this is how a radar 'sees' any object, in this case, an aircraft...

... A CLUSTER of voltage spikes.

Sophisticated software can recognize patterns of these voltage spikes and tries to categorize the object as a car, a human body, or like above, an aircraft. But for the vast majority of radar systems out there, civilian and military, if there is a discernible cluster against a somewhat stable background, the radar computer will call the cluster a 'target'.

So going back to the canards. If you begins to reduce the QUANTITY of structures that produces those voltage spikes, you will begin to reduce the EM visibility of the cluster, which is the B-2 and the X-36, and finally, the sphere (post 11837) which is the most obedient to the three rules.

Since '09, I have been saying the same thing over and over about the canards -- it is less about the canards than it is about the three rules. A decade passed and it has not taken root in this forum. None of the rules are more or less important than the others. Modify one and you will affect the other two. Like a three legs stool, modify one and you will change how the structure performs under stress. Ten yrs passed and no one proved me wrong considering there are claimed Ph.Ds in this forum.