what about in the case of the J-20 or X-36? or is their canards on a different position
@ Vans – It has nothing to do with position. Traditionally, canard designs (such as the current Eurocanards) are not stealthy because of the way they are made. See Rafale…
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The leading edges of these designs are made of titanium – which has a very high electrical permittivity. This is a problem because electric and magnetic fields are concentrated at sharp edges.
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In short, you cannot have stealth with metallic leading edges. If you make a blunt leading edge then you can be assured there is a normal vector pointed straight back at the receiver. And, since reflectivity is very high, such a design will not work for stealth. On the other hand, if you create a sharp edge then you get better directivity, but it will be a superb site for surface creeping waves to relaunch out into the atmosphere – again compromising stealth. There is a lot of electrical engineering that goes into these.
Actual stealth designs treat all of their edges. The front part of the J-20’s canards are made of a low permittivity dielectric (loaded with just enough conductivity – a sheet impedance of 377 ohms – to attenuate the wavefront) and so are suited for stealth.
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Rand revealed the build of US stealth designs a long time ago. See pages 7 and 8 on how the edges are always built of low permittivity dielectrics.
https://www.rand.org/content/dam/rand/pubs/monograph_reports/MR1370/MR1370.ch2.pdf
As for the Yakolev design in particular, there is no way you can judge whether something is stealth or not by looking at a wind tunnel model.
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