Chengdu J-20 5th Generation Aircraft News & Discussions

[hk299792458]

New photos, we can see J-7BGI and J-20, 3 generations of difference...

 

[hk299792458]

New video of J-20 #2002...

 

[gambit]

From the Chinese playground...

1. We know for a fact that an AESA radar has transmit and receive modules. Therefore, the paint on the J-20 radome must be transparent to X-band radar waves for both emission and reception.

Utter garbage. The T/R modules as an array is no different in operation than the classical dish or the newer planar: Transmit and Receive. That mean the word 'Therefore' is misleading. The radome must be a 'pass through' device to some degree. It is not the paint that must be transparent, although the ingredients that made up the paint can contain some trace metallic elements and this could interfere with transmission. Rather, these are the items that determine the color of the radome that so often different from the aircraft:

- The radome material itself must have a high degree of 'pass through',

- It is the construction of the material,

- It is the construction of the radome itself,

- Avoidance of trace metallic elements in any surface applique, aka 'paint'.

And these items give us why a radome is often different in color than the rest of the aircraft. It is the material, not the paint.

This is a case of someone who does not know what he is talking about but pretending he does.

2. If the radome paint is transparent in X-band then how does the J-20 stay stealthy in light of enemy X-band radar? Wouldn't enemy X-band radar pass through the transparent radome paint and composite nose to strike and reflect off of the interior AESA radar? The obvious solution is to have interior retractable panels coated with RAM.

Think of it this way. Divide the J-20 nose into four sections. Place four equal-sized RAM-coated panels underneath the radome. When the J-20 is in stealth mode, the interior RAM-coated panels are flush against the inside of the radome walls.

Incoming radar will penetrate the radome paint and composite walls. The enemy X-band radar will strike the RAM-coated interior panel and be absorbed. Hence, the J-20 remains stealthy.

When the J-20 is in search or attack mode, the four interior RAM-coated radome panels are hydraulically moved backwards. This allows the J-20 AESA radar to emit and receive X-band radar waves. If the J-20 pilot wants to shift back into stealth mode, the RAM-coated panels are hydraulically moved back into place against the composite radome walls and the fighter is stealthy once again.

This is hilarious and I got people, from Nellis to Hill, yucking themselves silly.

What this pretender is saying that the J-20 should have at least one thousand lbs of hydraulic pressure and complex high speed hydraulic actuators inside the radome to operate RAM panels. Weight? Reduce volume for the radar itself?

3. However, the most elegant solution is to have a radome paint composed of "phase change material" (PCM). I just don't know if the material currently exists to permit switching back-and-forth between transparency and opaqueness to X-band radar waves. Basically, I'm looking for a material where I can run an electric current through it to change its optical property with respect to X-band radar.

There is a near equal solution and one that REAL engineers, including the Chinese ones for the J-20, know: Frequency Selective Surfaces.

Readers: Keyword search 'ansoft frequency selective surfaces'.

Definition of 'inhomogeneous': Not uniform in character or content; diverse.

If the reader perform a search on the above keywords, he would come up on the name 'Ally Ying Liu' who is an 'Application Engineer' for ANSOFT China.

Frequency Selective Surfaces (FSS) are materials that are essentially absorber in operation. Some are more absorbent than others. The most basic FSS is the ferrite particle embedded liquid or thin film...

To the more complex designs such as 'analog circuits'...

8.5: CIRCUIT ANALOG RAM AND FREQUENCY-SELECTIVE SURFACES On GlobalSpec

The term circuit analog (CA) for such absorbers is derived from the fact that the geometrical patterns are often defined in terms of their effective resistance, capacitance, and inductance; and then equivalent circuit techniques are used in the subsequent analysis and design of the resulting absorber.

The above source have illustrations for those geometric patterns and yes, those are PHYSICAL structures in a thin film designed to alter the travel path of a radar signal INSIDE the material. Each structure, from a length of simple wire to the more complex Jerusalem Cross produces an effect, electrical and/or magnetic, upon the radar signal. We can LAYER these sheets into much more complex FSS to allow near complete 'pass through' in one direction and near complete blockage in the opposite direction. Some of the more complex designs are active, meaning electrically excited at will, that can be %100 'pass through' in one direction and %100 blockage in the opposite direction.

Of course, I have no knowledge of where these designs may be. I swear as God is my witness. None at all.

Anyway...This is what is meant when it is said a radome is an inhomogeneous device. The layers are not uniform in contents and configurations.

Further...When examining a radome, it is clear, at least to me, that an outgoing signal or 'transmission' have only one direction whereas an incoming signal, like that of an enemy radar signal, can come from any direction: top, bottom, either side, straight on, or oblique. So armed with this fact, it is obvious that we should design our inhomogeneous layers in such a manner to reduce non-frontal entrant signals to minimize our radar antenna's RCS contributorship. This is why frontal entrant signals -- from the enemy -- is highest because our layers have to allow outgoing signals. It is a trade off we are willing to live with: If we want the maximum and highest quality of signals out, then we must be willing to pay the price for letting the same in. We can see hints of this in Mr. Liu's paper 'Radome design for airborne radar' starting with slide 29 titled "Let's take an example of a curvature conformal FSS radome'. Slide 35 have examples of those geometric designs important in any FSS.

This is real engineering with credible sources.

Ansoft Announces HFSS Version 8.0

PITTSBURGH, PA- January 10, 2001-Ansoft (NASDAQ: ANST) today announced version 8.0 of the Ansoft High Frequency Structure Simulator (Ansoft HFSS). Ansoft HFSS is a full-wave finite element electromagnetic (EM) simulator that enables engineers to design three-dimensional (3D) high-frequency structures such as connectors, IC packages, and antennas found in cellular telephones, broadband communications systems, and microwave circuits.

Technology leaders like Nortel, Lucent, and Cisco already use Ansoft HFSS to design broadband communications circuits and components. Now those companies can include models generated by HFSS for their physical layer transient simulations of Gigabit Ethernet IC packages, boards and connectors; optoelectronic devices for broadband fiber modulators, receivers, and routers; and electronic devices for signal conversion in hybrid fiber-coax systems.

Absent relevant experience and we will see absurd ideas like hydraulic actuators inside the radome and everyone rushes to 'Thank' for such a 'useful' post.

 

[skyknight]

 

[j20blackdragon]

Gambit,

Tell us what you think about the J-31. We're all waiting for your expert opinion.

 

[hk299792458]

"Maiden" flight of J-20 #2002 after having installed it's radar... Someone knows more about it? Is it from 14th Institut or 607th Institut? GaAs or GaN? MMIC pic power rate?..etc.

 

[Esc8781]

Bumbit is back!

The J-20 is better than the F-22.
The J-31 is better than the F-35.

How?

Unlike the F-22, our fighters don't starve the pilot of oxygen.

Got proof that the J-20 isn't too?

And the F-35, Carlo Kopp has shredded that fighter to bits.

Carlo Kopp contradicts himself in his conclusions.

The F-35 is not even stealth, it's basically an upgraded F-16.

No $h!t.

 

[scholseys]

New photos, we can see J-7BGI and J-20, 3 generations of difference...

this is the closest Bangladesh will get to a 5th generation craft for a loooooooooooong time.

 

[Kiss_of_the_Dragon]

this is the closest Bangladesh will get to a 5th generation craft for a loooooooooooong time.

Don't worry dude, we still use J-7 too, all 5th gen fighters are still at testing stages...we won't get these untill 2017 or 2020...at that time...who know? Bangladesh will get one or two squadrons

 

[gambit]

Gambit,

Tell us what you think about the J-31. We're all waiting for your expert opinion.

Sure. The J-31 is a copy of the F-22. Now please do not insult the intelligence of the readers by pointing out differences in details.

 

[WS-10 Engine]

Sure. The J-31 is a copy of the F-22. Now please do not insult the intelligence of the readers by pointing out differences in details.

Sorry but we don't copy failed fighters like the F-22. Unlike the F-22 we want our pilot to get oxygen. Very important thing you know, didn't they teach you those things when you make your so called 'stealth' fighters.

Don't insult 5th generation fighters like the J-31 and J-20 by comparing it to 4.5 generation fighters like F-35 and the pilot killer F-22.

We all know how American 'stealth' fighters turn out.....getting shot down over Serbia (F-117) by soviet anti-aircraft.
Oh yes I'm sure American propaganda departments have brainwashed the gullible American public into believing the pilot lost control right? Oh sure it did Anything to coverup the humiliation to the American airforce.

 

[xuxu1457]

J-20 fly with new radar

 

[gambit]

Sorry but we don't copy failed fighters like the F-22. Unlike the F-22 we want our pilot to get oxygen. Very important thing you know, didn't they teach you those things when you make your so called 'stealth' fighters.

Don't insult 5th generation fighters like the J-31 and J-20 by comparing it to 4.5 generation fighters like F-35 and the pilot killer F-22.

We all know how American 'stealth' fighters turn out.....getting shot down over Serbia (F-117) by soviet anti-aircraft.
Oh yes I'm sure American propaganda departments have brainwashed the gullible American public into believing the pilot lost control right? Oh sure it did Anything to coverup the humiliation to the American airforce.

Yeah...One loss out of 850 sorties. How about the fact that the PLA predicted Desert Storm would result in tens of thousands of US casualties and had to withdraw that report/prediction with eggs on the generals' faces?

 

[Nestea]

 

[hk299792458]

Sure. The J-31 is a copy of the F-22. Now please do not insult the intelligence of the readers by pointing out differences in details.

Let me be disagreed with you - from the PoV of some of my friends from Dassault, Project 310 only "got inspiration" from YF-22 and also F-35.

They told me that when 2 aircrafts have 2 different roles, the similarity in physical appearance is only a "Trompe-l’œil".