J-20 5th Generation Fighter VII


by78

Lieutenant General
Five more... The first image gives a nice peek into the cockpit.

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zyun8288

Junior Member
The small number of members I'm referring to are verified by DT to be ex military, according to DT, at least.
While I agree with DT’s overall opinion about Dr Carlo Kopp, the problem is after 10 years, all of these DT experts still have not come up with a single analysis paper about J20’s RCS even 20% as comprehensive and scientific as Carlo’s paper.
It’s more than a decade now, keep on chanting the same “Carlo is bad, I am a defense professional“ is boring.
 

KampfAlwin

Junior Member
Registered Member
Now I'm wondering, could future variants of the J-20 be expected to remove the HUD in favour of the HMDS?
 

plawolf

Brigadier
While I agree with DT’s overall opinion about Dr Carlo Kopp, the problem is after 10 years, all of these DT experts still have not come up with a single analysis paper about J20’s RCS even 20% as comprehensive and scientific as Carlo’s paper.
It’s more than a decade now, keep on chanting the same “Carlo is bad, I am a defense professional“ is boring.

No one else has tried to do better because it’s an irrelevant exercise.

All his original analysis did was look at the external shape of the J20. But as anyone with even rudimentary understanding of stealth will tell you, everything from internal structures to the use of RAM and radar transparent composites all work together to give you the final outcome.

As such, while his work could provide a basement level worst possible case baseline for how stealthy the J20 was if China just made it out of standard untreated metal and only applied external shaping, so from a practical point of view is almost useless.

There is no need to repeat this exercise, nor is there much value in going beyond it since your input assumptions about the state of Chinese materials sciences and understanding of structural stealth principles are going to ultimately determine how stealthy the output model is. As such the analysis is essentially useless.

If you assume China has a poor mastery of core RAM and composite materials, and don’t know jack about internal structural design needs, then you will get poor RCS from the model. Conversely, if you assume China had state of the art RAM and composites and is well skilled in applying that to the design and knows the fundamentals of how to marry that with internal structural design, you are going to get a very good RCS design. It’s entirely based on your underlying assumptions so has very little value without credible additional information about just how good Chinese material sciences and internal structural design work is.

You can of course do a best possible RCS design, and I fully expect the US military to have completed such a study long ago. But the results from any such model would need to be kept top secret since the input assumptions are going to be hugely revealing about the current state of American stealth materials and structural design capabilities.
 

by78

Lieutenant General
Any insights as to what these pictures depict, in regards to the cockpit technology? Thank you.

As far as I can see, nothing new is revealed. We already knew the cockpit features a large single MFD and a smaller lower MFD (between pilot's legs). The pilot is also equipped with what appears to be a portable tablet (strapped to his right thigh?). This image is nice in that almost everything is seen with clarify, whereas most older images of the cockpit were either blurry, obstructed, or reflections off pilots' visors.
 

zyun8288

Junior Member
No one else has tried to do better because it’s an irrelevant exercise.

All his original analysis did was look at the external shape of the J20. But as anyone with even rudimentary understanding of stealth will tell you, everything from internal structures to the use of RAM and radar transparent composites all work together to give you the final outcome.
Agree. And the result is my point, all of those DT professionals can not do anything better than Dr Carlo did 10 years ago.

So can they still claim they know better about J20’s RCS?
 

Tirdent

Junior Member
Registered Member
All his original analysis did was look at the external shape of the J20. But as anyone with even rudimentary understanding of stealth will tell you, everything from internal structures to the use of RAM and radar transparent composites all work together to give you the final outcome.

As such, while his work could provide a basement level worst possible case baseline for how stealthy the J20 was if China just made it out of standard untreated metal and only applied external shaping, so from a practical point of view is almost useless.

Anyone with a rudimentary understanding of stealth? Somebody like, for instance, one Denys Overholser?

Stealth: The Secret Race to Invent an Invisible Airplane said:
But for most of the airplane, especially the exterior, the key advance was not materials but rather geometry. As Overholser put it, the [four] most important factors for shedding radar were "shape, shape, shape and materials"

So who is this guy? None other than Ben Rich's right-hand man for RCS reduction at the Lockheed Skunk Works during development of the F-117. The famous discovery of Pyotr Ufimtsev's work which enabled the shaping of that aircraft to achieve hitherto unheard-of stealth characteristics was his.

About the same time, Overholser's opposite number at XST programme competitor Northrop, John Cashen, came to a similar conclusion, from a slightly different perspective:

Stealth: The Secret Race to Invent an Invisible Airplane said:
As a result of all his work on missile defense, Cashen had received a thorough grounding in radar scattering and radar cross sections. And he knew what many aircraft designers did not know because of classification: that radar scattering theory had already been applied to actual airborne craft, including the Mark 12 reentry vehicle and the SRAM missile - and, further, that those vehicles had achieved remarkable reduction in radar cross section not through radar absorbing material but from the shape of the vehicle itself.

And if you think about it logically, circumstantial evidence for this principle of shaping over materials abounds in the configuration and testing of modern LO aircraft. Tests for optimization of shaping are done with all-metal (no RAM, or even any effort to match the construction of the real airframe) models like this one:

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(MDD/BAe JAST/pre-JSF layout, if memory serves)

More to the point, if composite materials were so important, how come the majority-CFRP Typhoon does not achieve a lower RCS than the mostly metal F-117?

Typhoon_materials.jpg

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While we're at it, why would you accept serious restrictions on major aerodynamic parameters such as wing/tail sweep angles (planform alignment) and structural design (internal bays, with all their weight penalties) if you could simply smother a conventional aircraft in RAM?

The fact of the matter is, shaping is the primary determinant of an aircraft's RCS, the objective being to concentrate reflection of incident RF energy into sectors too narrow for enemy radars to exploit. These spikes/hotspots (intakes, leading edges) are then treated with RAM to further improve survivability, but by analyzing the mere shape you can definitely deduce very valuable information about a LO aircraft! You can criticize the 3D model Kopp used as guesstimated and obsolete (IIRC it is based on the J-20 demonstrator configuration with different intakes, curved LERX and uncropped trailing edges), but the method is perfectly valid.

Last but not least, while he undeniably has biases and questionable opinions on certain subjects outside his area of expertise, Kopp is an RF engineer by education... Although I'd take his views on other aspects of fighter design with a large dose of salt, on the particular topic of stealth he is probably better qualified to comment than the vast majority of indeterminate "ex-military" people.
 
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