As referenced in the KeyPubs Stealth book at the start of the J-20 section. There was an earlier attempt which failed, so they started with a clean slate.
It's impressive and beautiful.
I wondered at first why a C-17 was refuelling Chinese aircraft.
I'm not 100% sure, but the aircraft might spend fuel in the forward fuselage, seems quite big, first. Then, the aircraft might have negative stability during combat mission. Anyhow, the main landing gear position seems not conventional for relaxed static stability fighter jets.. Or, they might focus more on long range capability rather than agility.
Why is canard area only counted on some but not others?
Your analysis is very high level resulting in data that is not necessarily very accurate. Using only MAC of the wing will yield results that won't even get you close. All surfaces have to be included as well as up wash effect on the forebody and canard, as well as down wash effects of the canard, etc. The truth of the matter, the approach you are using simply relating the 15deg landing gear to establish cg and 25% MAC on the wing for center of pressure will yield results that extremely inaccurate.
Which canard, of any of them, will make the nose go DOWN on takeoff if it's leading edge is up?
I am not going to be your professor to teach you performance, stability, and control. I would highly recommend you purchase a book by Perkins and Hage titled "Airplane Performance, Stability, and Control." It is considered one of the original authorities on the subject matter. You will soon find out how far you are off base with your assumptions.
It's a pity you think that these things can be calculated accurately without CFD analysis.
What makes this display notable for me is that the vertical roll seems to have been initiated when the nose pitched past 90 degrees. Vertical rolls I've seen before, but I don't think I've ever seen it executed at such a severe pitch angle.
I didn't see the nose come anywhere near 90 degrees.
You need to first understand the fact, that if you are the one arguing something, you should also be the one to prove it.
Dude, you need a powerful PC and CFD software to run the Navier-Stokes equations, and they can usually only be solved iteratively, not analytically, and even then you need a precise input model, so asking for such is simply ridiculous.
Deino is right, this discussion makes no sense. If you choose to ignore fact, so be it. As in the past, I refuse to be baited into this type of debate.
I believe Su-35 done that in combat approved video. But i can't find standalone video. Still, that J-20 maneuver still look good, but maneuverability is not their main purpose afaik. Launching barrage of PL-15 is seems more important than that.
Actually, they do.
Look more closely
Yes but the Su-35 has TVC. Launching a barrage of MRAAMs is also the main purpose of any fighter that’s supposed to be good at BVR (F-22 included). The whole point of Gen 5 aerodynamics is expanded flight envelope so you don’t have to make as many tradeoffs with flight regimes and corresponding tactical options.
If your primary interest is in modeling a hobby RC plane that’s only flying at 100 mph sure. But don’t let me stop you from insisting that aerospace engineers are wasting their time doing CFD analysis with expensive equipment for their jobs
The point is without knowing the pressure distribution of the flow field you have no way of identifying the relationship between center of gravity and aerodynamic center. The former already sits in a line between the front and back landing gears so that can only be guessed at with rules of thumb and the latter isn’t only unknowable from eyeballing when your plane’s shape is more than just all simple wing geometry or a tube and simple wing geometry, but actually shifts around in different flight envelopes. Now if you have access to wind tunnels and physical models you’re welcome to discard CFDs entirely, but I’m going to assume that none of us here have access to those tools so the only way anyone here could claim to know what the aerodynamic center is (specified in different flight conditions no less!) is if they bothered to do the legwork of building a 3D model that they then put through a CFD. The main takeaway is these rules of thumb are bullshit and not really defensible for anyone who’s actually serious about the subject matter. (And also Paralay’s J-20 diagram isn’t even accurate. Do an overlay with one of the many top view photos we now have of the plane if you don’t believe me).
Your pics actually support my statement. Look at the angle of the vortex coming off the wingtips. They're almost parallel to the fuselage.
