J-20... The New Generation Fighter III
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Vini_Vidi_Vici
Junior Member
anyone on this site has a makerbot or some sort of 3d printer? since there is so much debate on the canard, why not just print a 3d model of it and test it in a lab. that way we all know whos right. none of us a experts here, we all can find some sort of evidences supporting our beliefs. But at the end of day, no one is right because no one can physically prove it.
Actually my boy, the proof is in the pudding, the Raptor remains the sneakiest bird on the planet, based on the Raptors success, the F-35 which is also pretty L/O has been created in the same planform, as has Shenyangs F-60. My statement was in Regard to the Engineer's assertion that the Swedish radio controled model was proof that canards are superior for stealth. The model is unable to prove anything of the sort, as I have stated before the Radar return doesn't lie. The fact that Chengdu floats this model out there is just promoting their blood line, ie the canard stealth aircraft, until there is a prototype flying, we won't really know. While computer modeling is a fantastic tool for the aircraft designer, some of the F-35s issues remind us that models do not always reflect the full scale aircraft, and I'm referring specifically to the buffeting found on the F-35 prototypes as alpha was increased.
If your assertion that computer modeling would prove the canard one way or the other, is not reflected in the reality of the fighter world, were airplanes continue to be developed with both configurations to reflect the designers "taste" in airplane configuration.
I didn't say that they couldn't make it stealthy, I stated for the record that the Swedish Model is not proof that canards are stealthier than a conventionnal planform. It is simply a matter of "taste", and "branding" of company aircraft to a certain configuration!
Stop here little bro, you've brought up some decent points so just leave it here, I saw Vader Stomping around on the Plan carrier thread. This new design by Chengdu is just keeping up their family tradition.
MiG-29
Banned Idiot
look, canards are trimming devices, at supercruise, which is the ideal speed of a 5th generation aircraft, the aft-tail has no disadvantage over canards in fact the aft-tail reduces drag.
On designs like B-70 ot T-4, you have a long coupled canard, as a trimming device too but remember these are bombers and long couple canards are usually set on bombers, that is the reason some western analysis claim J-20 is a striker included the US air force magazine, compare J-20 to J-31 and you see a big size difference more in line with a striker.
Shenyang J-31 uses aft-tail and here i put you a chinese example to show you, that in China there are different design philosophies.
So you can not say i am bias.
J-31 in the other hand is smaller, has an aft-tail, with no dihedral, hidden frontally by the wing, in line with the F-22.
here you have the myth that the flight control system will lock the canard deflection at supercruise, when in reality at supersonics speeds the deflections will automatically increase to be fair that deflection also increases on aft tail designs, so canard always will requiere more deflection and thus RCS will increase.
J-20 has relatively long couple canard trying to reduce deflection but this reduces lift at high Alpha.
Stealth design requieres the wing and tail to be coplanar, J-31 uses that rule, J-20 breaks it, Shengyang went for a more traditional approach for that reason, why? because chengdu fell into contradictions, the canard should be coplanar for stealth, but above wing level for added lift.
Shenyang on J-31 used a more conventional but more effective way of reducing RCS than Chengdu`s J-20
Song`s paper even says that, the need to be coplanar is a stealth requierement
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Engineer
Major
The model actually says a lot. It says aircraft designers seriously consider the use of canard on a stealth fighter, as opposed to taking the myth about canard being bad for RCS at face value. Sweden's Generic Future Fighter is not the only concept to feature canard configuration, as Lockheed Martin's early proposal for JAST and Korea's stealth aircraft project also have canard. If canard is bad for RCS, no one would even bother to consider it.
MiG-29
Banned Idiot
Shenyang went for a much better way to reduce RCS on J-31, and here the problem is you think J-20 has no contradictions, but it does, at supersonic speeds, canard or aft tails deflect more, not less, you can not lock the canard to reduce RCS, that was said by an F-22 pilot, the only way you reduce the deflection is by using TVC nozzles as F-22 does, and by adding coplanar tails as J-31 you reduce trail signature and reduce the area exposed to the radar frontally those are design rules for stealth.
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Engineer
Major
Shenyang is known for its incompetence, so its design is hardly a good example of performance. The company went for aft-tail because it is a low risk approach, nothing more.
Engineer
Major
This is a load of rubbish. Size has nothing to do with the purpose of an aircraft. As an example, the Su-27 is larger than MiG-29 but the former isn't a striker. The use of long coupled canard does not make an aircraft a bomber, as J-10 uses long couple canard and is an air superiority fighter. Western analysis typically have no idea what they are talking about.
Shenyang is incompetent, so their design philosophy is to base their design on somebody's else design. It is not an example of a superior design.
J-20's relax stability combined with use of long couple canard means minimum deflection can result in large moment. The vortex produced by LERX reinforces the vortex from the canard, which increases lift at high alpha.
Shenyang went for traditional configuration because the company is not competent enough to make a design with sophisticated aerodynamics. This hardly constitutes as a proof that traditional configuration is more superior. Furthermore, 310 is just a private venture and not China's 4th generation air superiority fighter. That title belongs to J-20, as it is that Chengdu won the contract.
Song's paper says nothing of the sort. In fact, the paper contradicts what you've said by saying J-20 configuration has good supersonic drag and excellent stealth characteristics.
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