J-20 5th Gen Fighter Thread VI

[Brumby]

Apologetics describe a positive argument in favor of something,

I was surprised of your usage of "apologetics" as it is not a commonly known word even among English speakers .

And what kind of data is that supposed to be?? Didn't they already take the whole 3D model of the delta wing planes into simulation? Again, all the RCS calculation are obtained through computer, which should have automatically take into account all geometric changes of the wings during the simulation, giving you the final RCS result presented in that final graphs that you see on page 5. It's illogical to think there's more 'missing data' that you're still looking for; it's already aggregated in there.

I guess you tells us whether there is exclusion because the abstract of the document and the research seems to suggest a narrow focus of the study and analysis.

The abstract emphasized canard rotation and research component size stealth testing. This suggest to me a focus on the RCS of canards rather than the complete airframe


The following picture from the document supports such an idea. For sake of simplicity I am even discounting farfield requirements.



This is further supported from the document (translated) on the research premise that other stealth elements remain unchanged with focus being on component stealth testing i.e. canards.



In reality significant changes were made between pre and post canard incorporation to the wings (location) and on the tail surfaces.



These are the cascading effects that I was referring to especially when such changes would have an effect on its overall RCS beyond the readings on the canards. I have nor seen any 360 degrees all aspect RCS reading being presented such as the following.



The all aspect reading is not trivial as it is the primary requirement in RCS study as viewing angle is important..



source Radar Cross Section 2nd edition by Eugene Knott

 

[Brumby]

Note that this is for metallic RCS (no-coating), and minimal RCS is roughly -50 dBsm.

The other source is roughly

Please, Log in or Register to view URLs content!

.

Further discussion of the F-35's RCS belongs in the F-35 / USAF thread, but I want to point out that the F-35 is a physically smaller airframe than the F-22, and that it uses more advanced and modern RAM than the F-22. It is very plausible that the F-35, in certain bands and angles, is stealthier than the F-22.

@Air Force Brat

Basically, when the J-20's canards are discussed, it comes up that the space between the canards and the main body is basically a corner reflector that's exposed to the front. This corner reflector is addressed by highly aggressive use of RAM. Incidentally, the F-22 ALSO has frontal corner reflectors, but this is created by its intake system with a gap between the intakes and the main body to act as a diverter. In the F-22's case, the F-22 slathers ram aggressively in this gap to mitigate the effects of the corner reflection.

Out of the 4 charts that you presented, only one even remotely support your position of a -50dBms reading. With that chart I think i have a better argument that even the F-16 and F-18 is more stealthy than the F-35 given that there are more spike readings above 0 dBms than at -50 dBms. LOL.

 

[Inst]

/And? I can make an argument that the F-16 is stealthier than the F-22 by choosing the best azimuth/angle/frequency combo of the F-16 and comparing it to the worst of the F-22.

You yourself already stated the bowtie issue in common LO / VLO aircraft, and we know quite well the F-35 isn't designed as an all-aspect stealth aircraft unlike the F-22.

The statement in dispute is whether the F-35, in its ideal operating condition, is stealthier than the F-22, and by about -10 dBsm.

Hostage caused a stir in late spring when, in press interviews, he said the F-35 would be stealthier than the F-22, its larger USAF stablemate. Conventional wisdom had pegged the F-22, with its angled, vectored-thrust engines, as a stealthier machine than the F-35. Hostage also said the F-35 would be unbeatable when employed in numbers, which is why the full buy of aircraft is “so critical.”

“I would say that General Hostage … is accurate in his statement about the simple stealthiness of the F-35 [with regard] to other airplanes,” Bogdan said in the interview. The statement was accurate for radar cross section, as measured in decibels, and range of detectability, he said, and he scoffed at the notion that anyone can tell how stealthy an aircraft is just by looking at it.

Bogdan, likewise, is Lt. Gen USAF and chief executive of the F-35 project.

But as mentioned before, if you want to continue the discussion of the F-35's stealth, we can do so elsewhere.

 

[Air Force Brat]

I was surprised of your usage of "apologetics" as it is not a commonly known word even among English speakers .



I guess you tells us whether there is exclusion because the abstract of the document and the research seems to suggest a narrow focus of the study and analysis.

The abstract emphasized canard rotation and research component size stealth testing. This suggest to me a focus on the RCS of canards rather than the complete airframe
View attachment 56035

The following picture from the document supports such an idea. For sake of simplicity I am even discounting farfield requirements.

View attachment 56036

This is further supported from the document (translated) on the research premise that other stealth elements remain unchanged with focus being on component stealth testing i.e. canards.

View attachment 56037

In reality significant changes were made between pre and post canard incorporation to the wings (location) and on the tail surfaces.

View attachment 56038

These are the cascading effects that I was referring to especially when such changes would have an effect on its overall RCS beyond the readings on the canards. I have nor seen any 360 degrees all aspect RCS reading being presented such as the following.

View attachment 56039

The all aspect reading is not trivial as it is the primary requirement in RCS study as viewing angle is important..

View attachment 56040

source Radar Cross Section 2nd edition by Eugene Knott

That's right, I used apologetics because its the most precise word to shed light on the purpose of this paper, (the paper is explaining and offering justification for Chengdu choosing the canard configuration over the more traditional lay out)....

Many observers have criticized Chengdu for using the overtly less L/O canard for pitch control, this paper attempts to nullify those arguments, and rationalize why the J-20 is configured as it is by using the F-35 fuselage as a NULL value and measuring only the canard and traditional stabilator for pitch, and their respective effect on the RCS of the platform.

The F-35 was chosen for two reasons, it is an excellent L/O configuration, and it closely resembles the J-20...

with this I will attempt to back out of this discussion, and return to the J-20 with this question... were there 4 additional new aircraft in the latest batch of "primer birds?"

 

[by78]

A few more high-resolution images.

 

[Air Force Brat]

A few more high-resolution images.

Amazing to see those "long throw" canards at their full downward deflection, useful and in fact necessary to recover from the extremely high alpha flight without OVT. If you saw the recent picture of the F-18 doing a "cobra", the aircraft is in an extremely low energy condition, and that extra long throw of the canard facilitates recovery, with out the aircraft have to "fall through" the maneuver long enough for the nose to point down and pick up flying speed.

Here in the last picture, we have the aircraft still retaining much of its energy in forward flight, as noted by the normal deflection of the canards, which are aligned with the "relative wind".... we have yet to see a J-20 perform a "cobra" and the subsequent recovery, that would theoretically be facilitated by these long throw canards?

 

[by78]

Merry Christmas. All images are high-resolution.

 

[by78]

The latest image from a wall-climber.

 

[Untoldpain]

The latest image from a wall-climber.

Is it just me or does the engine look like a thrust vector variant with non-circular nozzle? WS-15?

 

[by78]

Is it just me or does the engine look like a thrust vector variant with non-circular nozzle? WS-15?

They are Taihangs.

(2000 × 1250)

(2000 × 1125)