That's not a fair or even accurate criteria, American stealth planes like B-2 was also secret for a long time, the F-22 is still one of the most guarded secrets. While J-20 is by no means a finished product, it is worked on by teams of Chinese scientists who graduated in China, and received training or further education abroad.
The fact it is not shown is by no means a reason for it not to work, as you have shown below it is possible to test it, so it's not like we have to throw it in to an American carrier group to know whether the stealth works or not.
The issue is how credible is any guess about any of these 'stealth' fighter from any country. So far we have US, Russia, China, and possibly India.
Outside of having fun at some of your friends' ignorance, I have always advised more serious minded people to be cautious about making claims, especially when said claims demands/expects numbers, and those numbers will not likely be released to the public any time soon. So while there is nothing wrong Chinese enthusiasts calling the J-20 'stealth', it certainly does give that visual impression, they should stop at making proclamations that the J-20 is 'stealthier' than...so and so. They have no relevant technical experience to start. Not even in the related civilian fields.
As far as Chinese scientists and engineers received training abroad goes, there is not a single 'stealth' curriculum in any university. You learn basic radar education, gain some practical experience, and if you are smart and lucky enough -- boom -- you are now a 'stealth' designer. Now go and design a 'stealth' fighter. Whether the J-20 is as 'stealthy' as the F-117, we will probably never know, or at best wait for a very long time to get any hard data. But when you say 'to work', it is meaningless because there is no accepted standard for what constitutes a 'stealthy' body, especially when the first 'stealth' body have its own data still secret. So what are you going to compare what you have against?
So if you are going to cry about 'fair', do it to your fellow Chinese. They are the ones being unfair in the first place when they make claims they cannot support.
I have heard stealth is not the same from different angles, so I'm assuming this is testing the stealth if radar from above.
A complex body like an aircraft will have uneven radar reflections from all aspects. The only body that have a constant RCS is the sphere. For the SR-71/A-12 example I gave, one possible test is that the aircraft was tested for radar reflections from a ground perspective.
It is counter-intuitive, but bear with me...
Most aircrafts will be detected from below -- the ground. The beam will impact the aircraft's underside. So if you want to test the aircraft's underside, the best way to do it is to mount the aircraft upside down and mount the radar beam from a higher elevation. If you mount the aircraft right side up, you radar will be very close to the ground and you will have limited radar test angles because you can only elevate your model only so high before it becomes dangerous. Plus, the ground will produce its own reflections back up to the aircraft's underside, producing contaminated data.
Something like this...
Substitute the missile for your test radar and you will see the example.
Now turn the aircraft upside down, elevate your test radar to any height you wish, then point it at the aircraft's (up turned) belly. Now you have highly concentrated radar info just for the belly. Any ground reflections will not contaminate the reflections from the (up turned) belly.
How about this for the F-35...
Do you understand now?
My point is that the J-20 should have isolated anechoic chamber
AND field testings. China can bypass as many tests as she wants. The more tests are bypassed, the less Chinese engineers will know if the J-20 is any good or hopefully comparable to the American 'stealth' fighters. You guys can make all sorts of claims for the J-20 as you want, but think -- have you learned how extensive such a testing regime must be from your other Chinese forums? Nada, amigo.
First as most knows China almost never if ever uses tech that we are uncomfortable with, so the fact it is there means it must have been extensively tested. Also, type 52C didn't use this radar, which means we didn't just slap something that didn't work on it, but instead waited.
Whether or not it is as good, I have no way to prove it, but just as well, you have no way of proving that it isn't as good.
Either way that's not the point of this discussion, as I was merely saying we have radar to test stealth.
The truth is that for 'stealth' bodies testing, you do not need an AESA array. The AESA technology was developed for combat or field operations capabilities. For testing purposes, the plain old planar or even the classical concave dish will do just fine.
