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siegecrossbow

General
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There are some gaps and discontinuities in the rear aspect, and in general there’s more round rather than faceted or angled shapes, that we don’t see in the frontal aspect. Maybe materials advancements help on those too. But from a shaping standpoint the rear is not as optimal as the front.

That's the case with most fifth generation aircraft though.

Anyhow I think we've gone off topic. Maybe these posts are better in the J-20 thread.
 

latenlazy

Brigadier
That's the case with most fifth generation aircraft though.

Anyhow I think we've gone off topic. Maybe these posts are better in the J-20 thread.
F-35 benefits from having just one stovepipe shape as opposed to two and seems to have put a bit more work into finer details in the wing to fuselage fairings. F-22 obviously traded some weight penalties to get optimal read aspect shaping. But yeah off topic at this point, sorry.
 

tphuang

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Ah, I see. When people say there's a problem with the J-20's rear, I assume they mean the planform. Hopefully there'll be blockers in the WS-15.

Overall, we're nitpicking here somewhat. Even in its current configuration, a plane would have to be directly behind a J-20 to get returns from the engine interior. Either this is happening WVR and stealth is already out of the window or it's a hell of a stroke of luck in BVR. Forget about SAM radar ever exploiting this.
you can just take a look at the rear of F-35 vs F-22 vs J-20. You will see how much F-22 hides its nozzles. F-35 would be worse than F-22 from the rear. Between F-35 and J-20, you can see a lot of gaps at the back which could also cause greater radar deflection.
F-35
GMKINSZ2X5IKBHSHG47VBVAAU4.jpg

now J-20

cia-j20.jpg

just more gaps possible deflection issues for J-20 at the back. And that's even assuming the canards trailing sawtooth patterns are scattering the radar coming off the delta wings rather than deflecting them back. I think there could potentially be issues there too.

Keep in mind the change from AL-31FN to WS-10C is a big deal. The new nozzle they have in there should be reducing both the radar and IR signature by quite a bit.
 

latenlazy

Brigadier
you can just take a look at the rear of F-35 vs F-22 vs J-20. You will see how much F-22 hides its nozzles. F-35 would be worse than F-22 from the rear. Between F-35 and J-20, you can see a lot of gaps at the back which could also cause greater radar deflection.
F-35
GMKINSZ2X5IKBHSHG47VBVAAU4.jpg

now J-20

cia-j20.jpg

just more gaps possible deflection issues for J-20 at the back. And that's even assuming the canards trailing sawtooth patterns are scattering the radar coming off the delta wings rather than deflecting them back. I think there could potentially be issues there too.
I think at this point any contribution from the canards and ventral fins should be pretty trivial with the right RCS mitigation treatments. Edge reflector effects are not where the challenges are.
 

tphuang

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I think at this point any contribution from the canards and ventral fins should be pretty trivial with the right RCS mitigation treatments. Edge reflector effects are not where the challenges are.
given how much effort is put into eliminating the tiniest imperfections in stealth aircraft, I would have to disagree with that. Also, I don't think ventral fins are that bad. To me, it's just a smaller vertical tail fin. and it also blocks the nozzle pretty well from the side.
 

Kejora

Junior Member
Registered Member
do you remember the podcast on this one? I can see the frontal RCS be quite low.
I remember that some western institute made a scale model of J-20 and tested it to gauge its RCS. Their finding is while not as stealthy as F-22 and F-35 its RCS is low enough to be considered stealth despite its big canards. This test had some flaws though, their model is based on the J-20 prototype rather than the production model, they also used commercially avalaible RAM coating while China obviously has better one especially for the latest version, also they might not apply the coating correctly since it was later revealed that J-20 has serrated coating on it canards.
 

Jason_

Junior Member
Registered Member
I remember that some western institute made a scale model of J-20 and tested it to gauge its RCS. Their finding is while not as stealthy as F-22 and F-35 its RCS is low enough to be considered stealth despite its big canards. This test had some flaws though, their model is based on the J-20 prototype rather than the production model, they also used commercially avalaible RAM coating while China obviously has better one especially for the latest version, also they might not apply the coating correctly since it was later revealed that J-20 has serrated coating on it canards.
If you are referring to
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analysis, the main conclusion would be that the J-20 is stealthy to the same order of magnitude as the F-22 (-40dBsm) in the optimal angle. Kopp is a famous F-35 critic and considers the F-35 to be less stealthy than the J-20, at least shaping-wise.
 
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