J-20... The New Generation Fighter III

Air Force Brat said:

A flying scale model proves nothing of the sort, and distant coupled active canards for primary pitch control will increase your RCS from the frontal aspect. The only true measure of RCS is the Radar return from your full scale prototype, anything else is conjecture.

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plawolf said:

From a conceptual stand point, there is nothing inherently unstealthy about canards.

Think about it, there is going to be small RCS spikes no matter what control surfaces you use, and it is perfectly possible to have a 'stealth mode' for canard fighters, whereby the FBW computer would limit the movements of the canards to minimise RCS.

You sacrifice some agility for enhanced RCS, which is no trade-off at all really, because if you are moving your canards enough that they give off a meaningful RCS spike, chances are your entire airplane is going to be making some pretty extreme manoeuvres that will increase your RCS by an order of magnitudes larger degree to the point where the small increase in RCS from canard movements is all but meaningless.

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Air Force Brat said:

A flying scale model proves nothing of the sort, and distant coupled active canards for primary pitch control will increase your RCS from the frontal aspect. The only true measure of RCS is the Radar return from your full scale prototype, anything else is conjecture. Its quite doubtfull that any one who doesn't need to know has any idea of the J-20s RCS outside of Chengdu and the PLAAF, and the Swedish model bears a mild resemblance to the planform of the YF-23, with the addition of the canards. I will say that the model flys fairly well, without the usual jerking and jinking of a small scale radio controlled models. This model would however make quicker pitch transitions due to the center of lift being located further forward near the center of gravity, and does demonstrate the principle of mass centralization, which does lend itself to relaxed pitch stability.

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jackliu said:

EXACTLY, J-20 is mainly going to be air superiority fighter, that means when other fighter trying to acquire it on radar, the radar beam will hit and reflect on the front, the side, back etc... since canard is mostly flat horizontal position, nothing is going to reflect back.

And yes, there are FBW software on Eurofighter Typhoon that minimize the movement of the canard when it is not needed for high G movement, no reason to think J-20 or even J-10 won't use the similar software.

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MiG-29 said:

Rafale and Eurofighter are not dedicated stealth fighters, they only have a stealth measure but their designs are not real stealth fighters.


Europes`s stealth designs are UCAV that use the flying wing configuration with no vertical stabilizators or ventral fins, no canard or tailplane.


Canards as trim control increase deflection at supersonic speeds from lower deflections at subsonic speeds however tailplanes also increase deflection, so a solution is TVC nozzles.

However aft tails are usually shielded by the wing on F-22 thus reducing radar exposure frontally, canards are best positioned at position above the wing making a secondary reflecting surface besides the wing frontally

Other stealth designs use tailplanes because tailplanes after mach 1 have better trim control characeristics than canards

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the stealthier shape is the flying wing with the least surfaces exposed to radar

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jobjed said:

Your point being? He said European designs have FBW software that minimises unnecessary canard movement to increase stealthiness. He did NOT say Euro-canards designs are stealth. Who doesn't know the Typhoon and Rafale isn't stealth?

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MiG-29 said:

at high speeds, aft-tail reduce drag, J-31, F-22 and F-35 use aft tails because of drag during supersonic trimming, add more drag you add more deflection.


Aft tails are easier to hide behind the wing thus reducing RCS.

Shenyang went for aft-tail because in RCS and drag, the design reduces RCS and drag.

Shenyang`s J-31 design will hide better the aft-tail from enemy radars than J-20 its canard specially with the dihedral they have and large size.


Pretty much canards by increasing drag and being less effective at supersonic speeds they requiere larger deflections.

Add a long couple canard, you reduce drag, thus deflection, but you also reduce lift at high AoA.

Eurofighter`s canards are radar reflectors that give it away easily on radar

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Quickie said:

Those people who still believe the myth about the canard being the main source of RCS return ought to look at this J-20 analysis - Analysis of Shape Related Specular Radar Cross Section

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One can see that the smallest RCS return is at the aspect when the nose and canards are head on and the greatest RCS return is at the aspect where the canards are at an arbitrary position other than head-on. Looking at the graphs, the horizontal and vertical stabilizers are something more to worry about when it comes to RCS return.

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