LFMS quote about the J-20 from another thread

Canards can work just fine in a VLO design. The principle that you have to be careful about not violating is leading edge treatment. You cannot violate this because they are by nature both strongly reflective by themselves and they are the prime launch points for “creeping waves” travelling through the skin of your aircraft. If you go look for an illustration of the surface composition of the Eurocanards, you will see that their canards have titanium leading edges. This creates a very strong impedance mismatch and so they are unsuitable for VLO. (Free space having an impedance of 377 ohms). But what you can do is build your canard out of a composite material with a sheet impedance close to that of free space (limiting the mismatch) or you can heavily treat the edges with a material with an impedance gradient which slowly bridges your canard material with free space. From photos of the J-20, it looks like the Chinese are doing this. They may even combine both methods. It is impossible to say for sure though because the Chinese are being very secretive. You can only find pictures of it in flyaway (primer coat) condition, whereas you can find pics of the F-22, F-35, and Su-57 while they are still in pieces.

Most information on the J-20 is pure speculation. However, Chinese literature hints that their engine technology will fail to allow for all aspect VLO with regards to radar. (They are certainly aware of this and will at some point fix it.) The J-20 also has horrible IR exhaust plume reduction measures. US designs use (relatively) large bypass ratios for extra cooling, we mount engines far forward so that the aircraft structure will partially obscure exhaust plume IR emissions from many aspects, and the F-35 ducts in extra cooling air under its wings. The Russian Su-57 seems to duct in a ‘third section’ of air too underneath its vertical tail and they space their engines (so that the exhaust plumes can lose heat through convection all around its exterior whereas the center region with tightly spaced exhausts can’t and so hold in heat) and they also cant their engines outward to force the hot exhaust air to merge with cold air travelling across the tail. Both the exhaust plume and the airfoil stream are highly turbulent and so will mix readily, shortening the length of the plume.

The J-20 has no such IR reduction measures. It may cool internal electronic components appropriately, but exhaust plume reduction is critical.

@Spudman

You would have to be above looking down on the F-35 for that to ever be an issue.

Next.

Spud. You don’t seem to think that Lockheed built stealth compromising features into the design of the F-35. Do you think Sukhoi would build stealth compromising features into the su 57 ?

2 – surface discontinuity at a normal to the aircraft’s axis causes diffraction return to the source radar

@Sintra and @Spudman

Is this just a prototype ? Maybe it will be fixed on the production models.

The windshield comes down and then there are 2 spherical bumps protruding out. Very questionable setup. RCS compromising.

Actionjackson is still hanging onto his story. He thinks that the su 57 got lit up by an F-22 in Syria And the US had nothing to say about it.

If this happened, it would be the other way around. The US would be saying it, and Russia would be denying it.

There is no operational US F-35’s deployed to Syria.

There’s not much else to say about this. The story sufficiently destroys it’s own credibility.

It looks like the canopy has resurfaced as their go-to red herring. Remember. In his lingo and pics, he is trying to convince you that the su 57 is one of these imaginary details away from being a 4th gen aircraft. Just like Tyler Rogoway said.

And its funny that he brought up the levcon. Which unlike the J-20, serves as a canard except it is neatly flush with the wings, at the ideal angle. The levcon also allows the virticle stabilizers to be markedly smaller. Which lowers the RCS, especially compared to the F-22 Raptor. Which has these rigid billboard sized virticle stabilizers. Yet the levcon gets trotted out as some proof that Sukhoi was more interested in manuverability. Umm no.

And no su 57 hit piece would be complete without “the pic”. The one famous pic showing some engine face. The pic also gives the illusion that you are looking straight at the aircraft. When you are not. Strange how there is just one. Let’s just pretend that the YF-23 and X-32 didn’t have engine face showing.

@LFMS

Russians do not believe in stealth the way it is discussed in the West.

If Russia didn’t believe in stealth, it would not have built the su 57. Russia did not need a new jet. The Pak Fa program was 1st and foremost , designed to neutralize the stealth advantage of the west. It is basic military doctrine. The most distinctive feature of 5th gen is stealth. The most distinctive feature of the su 57 is stealth.

Maybe their plane looks less “stealth”

I understand that you weren’t trying to be flippant but that is just a nonsensical statement. But I understand why you wrote it. The western defense media has been chipping away at the rep of Pak Fa program for so long, and blowing things so out of proportion, that is has caused people to see things that aren’t there. The Pak Fa was originally called the Raptorski. For a reason. The wests first comment about the su 57 upon seeing it was that plasma stealth had failed. Why ? Because of the carful shape of the su 57. Their words.

There is really nothing that doesn’t look stealth about it. Once you get to the bottom of all the alleged issues about the stealth, you’ll notice that there’s nothing there. This was all just a game of cheap shots. The back doesn’t have the hide-away nozzles like the F-22 does. That’s all fine an dendy until you notice that the F-35 doesn’t have those nozzles either. The su 57 will get the same serrated nozzle setup as the F-35. Then there’s the one famous internet picture that shows some of the engine face showing. That’s great until you realize that the YF-23 has the same offset intake, non true S duct setup either, and has a little engine showing. Same deal with the Boeing X-32. There was some real doozies like the unpainted engine coweling. That was a serious critique until they got painted.