J-20 5th Gen Fighter Thread IV (Closed to posting)

[kwaigonegin]

At lower frequencies, the shaping we rely on to cut RCS in the microwave region becomes more and more indistinct as the wavelength starts to approach the dimensions of the target. (For reference, the length of an F/A-18C is about 17 meters.) It’s like the case of light and dust particles—the complexities of the particle’s shape make no difference because its size is close to a wavelength of light. Like
dust particles dancing in a shaft of sunlight, when viewed at low frequencies targets tend to scatter radar energy in all directions regardless of shape.
Low frequencies are a problem also for RAM and RAS. The effect of radar absorbers is affected by their thickness relative to the wavelength—one quarter of the wavelength is best. As the wavelength reaches a foot or more, radar absorbers become impractical for
most targets.
The net effect is that at very low frequencies, the RCS of normal stealthy targets tends to approach that of non-stealthy targets of similar physical size—close to the physical area of the target. This is called resonant scattering because the wave is in resonance
with the target, leading to scattering of radiation in a broad fan

Again you are looking at it from the standpoint of the search radar however in your initial post I believed you were implying on the radar emissions of the targeted object and it's effect on it's own RCS.

 

[tphuang]

The radar cross section is not fixed, it depends in a few physical aspects, first the power density, which means how much electromagnetic energy is emitted by the radar measured in voltage.
The other is distance, since radiation dissipates and is absorbed by the environment, basic laws of quantum mechanics will explain it for you.

Shape also will be another factor, but shape is useless in the low energy spectrum, and stealth aircraft have no fixed RCS, their RCS is variable depending in the type of radar, frequency and medium.

More powerful radar=bigger RCS

F-15, you are a new member, so I will keep it short.

Deino asked people to get back on topic. It's not appropriate to start the same argument after moderator has already instructed to move on. Please be advised on such going forward.

 

[Jeff Head]

More powerful radar=bigger RCS

No, the RCS is what it is.

A more powerful radar may allow the reflection to be received further away, but in and of itself it will not increase the RCS itself.

And, as has already been stated,

STOP the discussion about the F-22 vs PAKFA RCS or other qualities on this J-20 thread

 

[Jeff Head]

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- USNI News

​

China’s stealth fighter program hit a milestone when a sophisticated prototype of its J-20 aircraft made its first flight earlier this month. J-20’s builder, Chengdu Aircraft Corporation (CAC), appears to have spent significant effort in giving the new prototype—No. 2011—stealth from different angles, a more maneuverable airframe, and fitting it with a complete set of avionics.

CAC spent a lot of time testing two previous prototypes—Nos. 2001 and 2002—before making the changes to the new version.

The first two prototypes basically were the technology demonstrators for this project, whereas No. 2011 should be looked at as the first pre-production prototype.

Studying the following photos from Chinese online forums, there are numerous subtle changes from Nos. 2001/2002 to No. 2011

The comparison pictures show improved workmanship, moving from a demonstrator to prototype.

The most obvious change is the F-22-style light grey color scheme that makes it easier to identify changes.

Comparing the side views, it appears the intakes have been redesigned to be a little more slender with a more protruding (and possibly larger) bump.

The leading part of the intake is also slanted inward a little bit to conform better with the body. The back corners of the canard have been clipped and inner edge has been cut in a way so as to not leave any gap with the intake.

The back corners of vertical tail fins have also been clipped. According to a Chinese research paper, that seems to reduce the radar signature from side angles.

The front and rear landing gear doors also have been modified and the wing actuators are flatter.

Comparing the bottom views, the main weapon bay seems larger, allowing it to hold more than just air-to-air missiles and precision guided munitions. The leading edge is now straight rather than curved.

The tail booms are longer and wider, while more parallel to the exhaust. The ventral fins look a little larger and now completely shield the exhaust from most of the side views.

It looks like unless an aircraft is directly trailing the J-20, the radar signature from the exhaust should be much lower than before.

There also appears to be a fairly comprehensive set of avionics on board. No. 2002 is believed to have been installed with and testing AESA radar.

Based on frontal view comparisons, the nose of No. 2011 may be slanted at a slightly smaller angle to better fit the intended radar.

A new electro-optical tracker similar to the F-35′s Electro-Optical Targeting System has been installed on the chin of the J-20.

Also included are defensive avionics systems with panes and bumps installed on both sides of the nose, the intake, and tail.

While the interior of the cockpit cannot be seen, it’s apparent that a new type of holographic heads-up display (HUD) has been installed and that the canopy has been modified with an inner-canopy frame.

A new generation of integrated electronic systems already has been tested out in the J-10B project, which should be very helpful to the J-20 project.

Focusing on radar, J-10B will be installed with a first-generation AESA radar and the Shenyang J-16 will be installed with an 1.5 generation AESA radar. By the time J-20 comes into service, it will be installed with a second-generation AESA radar.

China’s improvement in radar technology, the appearance of various external avionics installation and work done in the Chengdu J-10B project point to a modern integrated electronics system.

The new prototype represents a vast improvement over Nos. 2001/2002 in stealth, maneuverability and avionics. Based on the timeline of other People’s Liberation Army Air Force projects, one expects the serial production of J-20 to start around 2019, with the first operational unit forming around that time.

The one big question mark for the J-20 is the WS-15 engine, which currently is still in development. It’s unclear whether or not that engine will be available once serial production starts.

I had not seen this posted here...but may have just missed it.

If not, it should have been...and if so, then it never hurts to reiterate it. Also, some great photos and comparisons in the article.

This article was written by one of our own Super Moderator's here on SD. It is a great acheivement and honor to be recognized by the US Naval Institute News site, and I am glad to see it posted accordingly.

Congrats Tphuang!

 

[Air Force Brat]

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- USNI News

I had not seen this posted here...but may have just missed it.

If not, it should have been...and if so, then it never hurts to reiterate it. Also, some great photos and comparisons in the article.

This article was written by one of our own Super Moderator's here on SD. It is a great acheivement and honor to be recognized by the US Naval Institute News site, and I am glad to see it posted accordingly.

Congrats Tphuang!

Thanks for posting Jeff, and congratulations TP, and as Jeff has stated it is a high honor to be recognized by the US Naval Institute News, we're all very proud of you TP, and I am thankful for your respectful and authoritative posts. No nonsense, no bull, just a fair and honest assessment, two thumbs up brother. the brat

 

[by78]

Two new models of large touch screen MFD. Don't know if they are J-20 related, but I thought this thread is the most appropriate place to post them.

 

[T-U-P]

Two new models of large touch screen MFD. Don't know if they are J-20 related, but I thought this thread is the most appropriate place to post them.

It says "infrared touch function", what is that?

 

[Equation]

It says "infrared touch function", what is that?

I'm thinking a touch screen sensitive to heat because the pilots are wearing gloves.

 

[no_name]

It says "infrared touch function", what is that?

It recognise body heat from finger touch?

 

[Pmichael]

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