Chinese stealth fighter jet may use US technology

[Akasa]

You must be dreaming IF the J-20 is not as low radar observable as the F-117. The F-117 and F-22 usually fly with radar enhancers whenever either are for public display. Would we see the same for the J-20 later? There is a way to estimate a body's unenhanced RCS based upon the enhanced value and some pictures. If the J-20 fly for public display and if we can detect its enhanced RCS value and if the estimated unenhanced RCS is not within a certain statistical range, its radar observability will be anything but low.

Let's get this straight.

The frontal RCS of the J-20 (where its weak point is) is under 0.05 m squared. So there is slim chance that the RCS is higher than the F-117.

Multiple stealth reduction technologies such as DSI intakes, plasma stealth, a new type of alloy, and extensive stealth shaping all contribute to lowering RCS.

The F-35 and especially the F-117 rely mostly on their stealth coating. We saw what happened to the F-117 in Serbia as soon as their stealth coating got wet. The F-35 may have better coating, but it's still high stakes to play.

 

[dbc]

Let's get this straight.

The frontal RCS of the J-20 (where its weak point is) is under 0.05 m squared. So there is slim chance that the RCS is higher than the F-117.

You appear to be stating a fact when you posted "...the RCS is under 0.05m2"- if so, do you have any supporting evidence? I'll settle for a compelling argument based on sound scientific reasoning.

Multiple stealth reduction technologies such as DSI intakes, plasma stealth, a new type of alloy, and extensive stealth shaping all contribute to lowering RCS.

The F-35 and especially the F-117 rely mostly on their stealth coating. We saw what happened to the F-117 in Serbia as soon as their stealth coating got wet. The F-35 may have better coating, but it's still high stakes to play.

The role of the divertless intake in RCS reduction is overstated its effectiveness is at best marginal particularly for an aircraft with large intakes like the J-20. Serpentine or 'S' shaped intake ducts are much more effective but only if movable elements of the duct such as bypass and bleed vanes are positioned to minimize backscatter. Further, intake ducts receive a generous application of RAM coating to bring its RCS contribution to acceptable levels by minimizing reflection from frontal illumination of the air cavity.

Next, I bring your attention to the aircrafts radome(nose) - the largest contributor to frontal RCS. Do you know if the J-20's radome is radar transparent? Or, if the radar is shielded by a precision engineered bandpass/bandstop radome? You claim the J-20 is made from a new radar absorbing 'alloy' - how effective is it? Is the canopy radar transparent? Surely, you have an answer to all these questions how else were you able to arrive at a figure of 0.05m2 for frontal RCS? I've just scratched the surface for what it takes to make a low observable fighter. We'll get to it once you've provided satisfactory answers to the questions I posed.

 

[AerospaceEngineer]

NICE "evidence" though,dont you know that is a korean?

Due no need talking to him.

He is banned.

 

[Akasa]

You appear to be stating a fact when you posted "...the RCS is under 0.05m2"- if so, do you have any supporting evidence? I'll settle for a compelling argument based on sound scientific reasoning.

With the F-117's RCS estimated at 0.1 m, my point is that the chance of the overall J-20 RCS being higher than that of the F-117 is slim.

The role of the divertless intake in RCS reduction is overstated its effectiveness is at best marginal particularly for an aircraft with large intakes like the J-20. Serpentine or 'S' shaped intake ducts are much more effective but only if movable elements of the duct such as bypass and bleed vanes are positioned to minimize backscatter. Further, intake ducts receive a generous application of RAM coating to bring its RCS contribution to acceptable levels by minimizing reflection from frontal illumination of the air cavity.

Next, I bring your attention to the aircrafts radome(nose) - the largest contributor to frontal RCS. Do you know if the J-20's radome is radar transparent? Or, if the radar is shielded by a precision engineered bandpass/bandstop radome? You claim the J-20 is made from a new radar absorbing 'alloy' - how effective is it? Is the canopy radar transparent? Surely, you have an answer to all these questions how else were you able to arrive at a figure of 0.05m2 for frontal RCS? I've just scratched the surface for what it takes to make a low observable fighter. We'll get to it once you've provided satisfactory answers to the questions I posed.

DSI and serpentine intakes are still a better option for lower RCS than not having them. It's better to have many technologies working in your favor rather than just relying on one. Pure RAM coating (like the one applied on the F-35 and F-117) fails to deliver as soon as large amounts of moisture is present or a scratch is made. This requires maintenance.

The frontal RCS of the J-20 is reduced by the chined nose, DSI, etc. This stealth shaping already contributes to reducing the RCS, even if RAM isn't as effective. Now, speaking on the avionics part, the Type 1475 AESA radar on the J-20 will have low observability functions. Whether or not the nose creates points of destructive interference for certain wavelengths is up to debate, but the radar is the most important aspect when it comes to RCS emissions, since it's in constant use.

If the new alloy isn't as effective as the conventional composites, then why incorporate it?

Same with the canopy. They made a new type of alloy for the plane as well as plasma stealth technology. Even though there is few information on the actual materials used, I'm pretty sure they can build a canopy that lets wavelengths pass.

 

[Obambam]

No...You said something about 'sensitive' airspace. Commercial civilian airspace, even territorial, are not 'sensitive'.

If you are bothered to read my post properly, I mentioned both "sensitive" airspace and the local "ATC" which is the Air Traffic Control.

I do not recall ME referencing any Chinese official. But do correct me as I have made many comments about this subject.

Yes you are correct, you didn't mention about the Chiniese military officials, I did. However you did mention about people calling J-20 stealthy based on appearance alone. I counter argued that it was the public and military analysts from around the world who said that it has a stealthy design. Which means that the airframe itself can in fact be stealthy, regardless if it is or isn't a finished product.

Wrong...My cautions regarding jumping to conclusions are very relevant.

Your cautions regarding jumping to conclusions is as relevant as my conclusion that the RCS of the F-22 can also be estimated with your methodology of prediction.

Those were the essence of my caution.

The essence of your caution is also the essence of my explanation as to why you cannot predict the true RCS of the unfinished product or sum up how stealthy it really is. There is a lot of work to be done and modifications to be made to further enhance it's stealth capabilities.

You might want to tell that to your fellow Chinese members here. But good luck with that...

They do not need me to tell them, they already know. The only ones taking the J-20 all out of contexts are the west and calling this a F-22 killer or a rival to the F-22 etc.
We Chinese are simply happy and proud that we finally have a indigenous Gen 5 fighter on the conveyor belt. Perhaps you can tell your fellow Americans to ease up, take the chill pill and just enjoy the show? There's no need to jump into conclusions at all

 

[gambit]

With the F-117's RCS estimated at 0.1 m, my point is that the chance of the overall J-20 RCS being higher than that of the F-117 is slim.

No...It is not that high. And you still do not have anything other than hope that the J-20's RCS is the equal.

DSI and serpentine intakes are still a better option for lower RCS than not having them. It's better to have many technologies working in your favor rather than just relying on one.

That still does not mean DSI was developed FOR low radar observability. Yours is the typical technology for technology's sake mentality. The F-22 does not have DSI simply because the aircraft does not need it.

Pure RAM coating (like the one applied on the F-35 and F-117) fails to deliver as soon as large amounts of moisture is present or a scratch is made. This requires maintenance.

Are you speaking from experience? I highly doubt that. A gouge on the J-20's surface will have the same effects no different than that of the F-117 or the F-22. As for rain, can you even tell the difference between the alleged effects on RAM versus the true effects of rain on low radar observability? I highly doubt that as well. You got suckered.

The frontal RCS of the J-20 is reduced by the chined nose, DSI, etc. This stealth shaping already contributes to reducing the RCS, even if RAM isn't as effective. Now, speaking on the avionics part, the Type 1475 AESA radar on the J-20 will have low observability functions. Whether or not the nose creates points of destructive interference for certain wavelengths is up to debate, but the radar is the most important aspect when it comes to RCS emissions, since it's in constant use.

Well then...If the J-20's radar must be in constant use, then it will die without knowing who killed it from where.

If the new alloy isn't as effective as the conventional composites, then why incorporate it?

That is not the question, which is about the bandpass/bandstop capability of the radome. A 'stealth' radome is supposed to block radar signals from entering a cavity but is supposed to pass outgoing radar signals. That is bandpass/bandstop. But the J-20's radome may sacrifice radar transparency, meaning decrease radar effectiveness, for RCS control. If that is the case, and if the J-20's RCS is still nowhere near the F-117's class, then the J-20 will be dead meat for the AESA equipped F-15s.

Same with the canopy. They made a new type of alloy for the plane as well as plasma stealth technology. Even though there is few information on the actual materials used, I'm pretty sure they can build a canopy that lets wavelengths pass.

Please spare us with this 'plasma stealth' nonsense......You are out of your league here.