Chengdu J-20 5th Generation Aircraft News & Discussions

[SQ8]

The fact that they do need a Luneberg Lens reflector should tell you how stealthy the aircraft is.

 

[Akasa]

The fact that they do need a Luneberg Lens reflector should tell you how stealthy the aircraft is.

That tells us nothing about the aircraft; any airframe operating in the LO-VLO regime would require this.

 

[SQ8]

That tells us nothing about the aircraft; any airframe operating in the LO-VLO regime would require this.

Actually it settles the issue regarding the canards being considered unstealthy.

 

[gambit]

Actually it settles the issue regarding the canards being considered unstealthy.

No, it does not 'settles' anything.

The J-20 maybe 'too stealthy' for civilian radars, hence the need for enhancers. But for military radars, especially the increasingly sophisticated AESA systems with matching data processing capabilities, the canards maybe just enough to raise the jet up to the detection threshold that is not available for public consumption.

I do not care what APA says. They are a joke among professionals -- retired and active -- in the field. The people that I know -- Old Crows -- do not take APA seriously. And these gents go all the way back to WW II.

I know that people seeks definitive answer. Closure, in a manner of speaking. But they are not going to get it. I was in that business long enough to know better. I may have teased our Chinese friends some, but ultimately, throughout the yrs on this forum, my position have never changed: That unless we have the hard measurement data, we will never know.

Here is marine safety using radar enhancers...

http://www.defender.com/category.jsp?path=-1|135|2290117&id=2290118

Fishing dinghies are indeed 'stealthy' and need enhancers, but no one is threatened by them.

Right now, at best, the J-20's canards are highly suspect. But we should go no further either way.

 

[grey boy 2]

 

[艹艹艹]

壁纸，
wallpaper

 

[Indus Pakistan]

@gambit Where do you place this jet compared to American/Russian 5th gen aircraft?

 

[艹艹艹]

Clearly the IRF-probe is visible ... but where is the gun ??

View attachment 345600

In your pants.

 

[Ultima Thule]

In your pants.

no sir he has a valid question don't laugh at him and respect others

 

[AmirPatriot]

@gambit Where do you place this jet compared to American/Russian 5th gen aircraft?

Oh God... here we go. He's already sparred with Chinese members here on a numerous basis.

 

[gambit]

@gambit Where do you place this jet compared to American/Russian 5th gen aircraft?

To be 'conservative' about this, and speaking as a sensor specialist, I would place the J-20 as not yet comparable to the US 'stealth' fighters. That is NOT to say or even imply any kind of negativity to the jet because it is Chinese. When you have an established standard that came from a leader in a field, any contender should be assessed from that 'conservative' perspective.

Did the F-117 went thru the same 'conservative' assessment ? Of course it did. Ben Rich, in his memoir Skunk Works, told plenty of skepticism and even outright doubts of what he and his team claimed they could do. The doubts continued even after he presented to everyone hard measurement data from the desert tests. Being 'conservative' is a natural human reaction to meeting something new. There is no malice here.

But to answer your question, a brief review is necessary.

In designing a 'low radar observable' body, there are three rules, but more like guidelines, to follow:

- Control of quantity of radiators
- Control of array of radiators
- Control of modes of radiation

Anything can become a radiator, either as a conduit or being able to generate its own EM radiation. So from this perspective, a reflecting surface is a radiator.

A sphere is THE body for calibration of any radar system design. The sphere is the most obedient body to the above rules.

As usual, just in case anyone thinks I make this stuff up...

http://www.centurymetalspinning.com/radar-calibration-spheres/
https://en.wikipedia.org/wiki/Lincoln_Calibration_Sphere_1

It is technically the oldest operational spacecraft, but it has no power supply or fuel; it is merely a metal sphere. It has been used for radar calibration since its launch.

Mission duration
50 yrs, 10 months, 28 days (as of 28 January 2016)

Four other spheres were also manufactured and measured for comparison to the one in orbit.

Everyone, including the Russians and Chinese, uses the LCS.

So under rule 1 ( control of quantity of radiators ), the J-20 is seemingly less obedient with its 8 major flight controls structures, whereas the F-22 have 6.

But then how do we explain the F-117 with its many surface angular structures and yet its RCS is still secret to this day ?

Now we have to look at rule 2: Control of array of radiators.

Array means alignment of structures in relations to other structures, and when you have a medium, electromagnetic radiation, that reflects upon encountering a surface, array of radiators is of equal importance as how many radiators there are. The F-117's RCS is low, despite it being less obedient to rule 1, because of it being more obedient to rule 2.

From all the visual cues we have, the planform alignment of the J-20 is not 'as good' compare to the the F-22 and F-35.

Modes of radiation means how do the EM signals leave the body. Reflection is the most common and is the foundation of radar detection in general. Other less known modes are surface waves and edge radiation. Curvatures offers better control of modes of radiation than the angular faceting techniques on the F-117, so every 'stealth' design uses curvatures. Finally, curvatures are better for aerodynamics considerations.

The three rules are effective at every level of design, from large structures like a wing and down to the small details like the arrangement of screw heads on access panels.

This is why when the J-20 came out, its canards quickly took center stage because of rules 1 and 2. No one doubts the J-20 as an equal to the US fighters because of it being Chinese.

So just from a sensor perspective, the J-20 is already suspect as being comparable to the US 'stealth' fighters. Nevertheless, I have consistently been fair and advised everyone from making definitive statements simply because the measurement data for all these aircrafts are not public information. We have not touched other issues like overall avionics, weapons, maneuverability, and propulsion.

Oh God... here we go. He's already sparred with Chinese members here on a numerous basis.

The problem lies with the PDF Chinese, not with me. As you can read above, what I posted was completely technical in scope and I can and have backed up my arguments with credible sources like from NASA or from IEEE, not from blogs.

The PDF Chinese claque cannot hold any rational discussion over this issue. They do not have the background and emotionally, they are man-childs. Worse, they hold the view that any negative or even reasonable doubts can only come from one source: racism.

You cannot have a rational discussion with such people.

 

[艹艹艹]

no sir he has a valid question don't laugh at him and respect others

Not to laugh at, I'm kidding.

 

[Indus Pakistan]

I would place the J-20 as not yet comparable to the US 'stealth' fighters.

That would make sense. Chinese technology is leaping forward but still not 'mature' like the US which of course has had decades of experiance of being in the vanguard.

This would suggest that decade or so Chinese will be knocking at the apex.

 

[Beast]

That would make sense. Chinese technology is leaping forward but still not 'mature' like the US which of course has had decades of experiance of being in the vanguard.

This would suggest that decade or so Chinese will be knocking at the apex.

You really take his words seriously? This guy is famous for trolling anything on Chinese. He is very bitter on rise of China.

His explanation has too many flaws.

 

[Akasa]

His explanation has too many flaws.

Such as...?