J-20... The New Generation Fighter II

HKSDU said:

I see a flaw in your thinking. You think that more area equals more radar signature. So your saying that a smaller Mig-21 has a smaller RCS than an B-2, cause the B-2 is larger? Then what definition is stealth to you then?

Another thing, you have no idea how much the J-20 weighs, how big it actually is, its capabilities and performance, nor do you know how much thrust the engine outputs.

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Man do not go just to statement just to win an argument, both aircraft the F-35 and J-20 have the same continous curvature and diamond shaped cross section to reduce radar signature is that okay? well the area exposed by the J-20 is larger, it reflects more electromagnetic waves than the F-35 therefore its radar signature will be larger on equal RAM coating, if the F-35 has inferior coating might be equal.

Now to answer your question yes the B-2 does reflect more radar waves than the MiG-21, the difference is the MiG-21 sends them back straight to the radar while the B-2 sends the radar waves away from the radar, so what a radar operator sees is 90% of the original radar pulse on a MiG-21 and just 0.1% of the B-2

MiG-29 said:

the conclusion is the J-20 is more a striker than a fighter and only with advanced avionics and missiles will be able to fight, this is not to minimize or belittle it, it is a tornado adv type fighter with modern stealth

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Your conclusion is completely disconnected with your premesis... if we can call them premesis. All you did was posting a bunch of pictures of fighters with canards, which does not allow you to draw any conclusion with regards to the role of J-20.

However, we know that J-20 is a fighter because of the "J" in its designation. If the plane were a strike aircraft, it would have been started with "Q". If the plane were a fighter-bomber, it would have started with "JH". If the plane were a bomber, it would have started with "H". Attempts at arguing that it is a bomber/striker simply shows one has completely disconnected with reality.

^ People can also argue it's an interceptor like the J-8II

MiG-29 said:

The drag equation states that drag (D)is equal to a drag coefficient (Cd) times the density of the air (r) times half of the square of the velocity (V) times the wing area (A).
D = .5 * Cd * r * V^2 * A

pay attention Drag is equal to times the wing area (A).

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Pay attention that the equation contains the drag coefficient, so drag is not soley determined by wing area. We also do not know how the J-20 and F-22's wings compare to one another.

MiG-29 said:

...area is importat since it is multiplying a bigger area makes for a bigger result, thus the J-20 having a longer fuselage will have higher drag, of course shape matters but since both designs have similar cross sections they won`t have a big difference in shape you can not expect the J-20 to have lesser drag just a relatively higher but not by much in the best case

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What a poor attempt at trying to deceive people. Fuselage area is not the same as wing area, is it? So in the end, you still have no proof that J-20 will have higher drag whatsoever.

Bltizo said:

^ People can also argue it's an interceptor like the J-8II

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Not if it can't go above Mach 2 .

Engineer said:

Pay attention that the equation contains the drag coefficient, so drag is not soley determined by wing area. We also do not know how the J-20 and F-22's wings compare to one another.



What a poor attempt at trying to deceive people. Fuselage area is not the same as wing area, is it? So in the end, you still have no proof that J-20 will have higher drag whatsoever.

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Drag means air friction or opposition when they say area times means is because it is a direct factor in the equation, it is not dividing, any surface (area) while moving through the air experiments friction, or in other words air drag, independently if it is a wing or nacelle the equation applies to any surface

MiG-29 said:

Canards do control the vortices they generate however they also generate a downwash...
On a canard cases its down wash is turbulent flow, not laminar, this will kill some lift at the wing and also its Vortices are bursting first thus canards have a drag disadvanatge, the Su-35 has eliminated the canard in favour of TVC but T-50 has not, however it does not use a canard but a LEVCON.

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As I have pointed out earlier, on an aircraft with traditional configuration, the wings generate downwash which pushes on the tail and kills some of the lift. All designs have some advantages and disadvantages, but cherry picking difficulties of canards configuration and ignoring similar problems in traditional configuration doesn't give your "J-20 sucks" thesis any support.

It also still doesn't lend any support for your idea that J-20 is positively stable in the longitudinal axis. I thought I'd mention this incase you conviently forgot about it.

MiG-29 said:

Drag means air friction or opposition when they say area times means is because it is a direct factor in the equation, it is not dividing, any surface (area) while moving through the air experiments friction, or in other words air drag, independently if it is a wing or nacelle the equation applies to any surface

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No. Giving the dictionary definition of drag does not remove the influence of drag coefficient. You are cherry picking the wing area parameter out of the equation and try to portrait it as the sole determinator of drag. You are also trying to portrait fuselage area as wing area when the equation specifies that area is the referenced wing area. Your argument is invalid as a result.

Engineer said:

This still does not support your conclusion that J-20's aerodynamic center is behind the center-of-gravity in anyway. Nice try.

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Now compare the J-20 to the Rafale

The first think it will strike you is the wing of the Rafale is positioned further forward from the engine nozzles and the main landing gear is farther back from the wing root and leading edge.
This shows easily tha all Eurocanards are unstable longitudinaly and the J-20 is closer to the Viggen in configuration

the Rafale also has LERXes but its canards are closer to the wing and above it, this means their vortices re-energize better the wing (if you disagree you can read technical documentation about canards and see all fighters J-10, Gripen Eurofighter, Rafale, MiG1.44 have the same configuration)


the conclusion is the J-20 is more a striker than a fighter and only with advanced avionics and missiles will be able to fight, this is not to minimize or belittle it, it is a tornado adv type fighter with modern stealth

in this picture you can see the vortex formation on the Rafale and you can see its LERXes and inlet forebody do create Vortices increasing AoA handling


however this proves the Rafale has higher levels of relaxed stability and has a better canard position

question for you where is better to put a canard see these three aircraft and tell me where is the canard better positioned?
On the MiG-8 the Canard is bellow wing level

On the Su-33 is at almost at the same level of the wing with a little dihedral though


On the J-10 is above wing level


Now answer and tell me which design has a delta wing and canard more of a fighter the J-10 or the J-20, the Rafale or the J-20?

MiG-29 said:

LEVCONs are not control surfaces as canards are, a canard can pitch the aircraft as a tailplane does, a LEVCON can only stall or increase the wing lift moving the center of lift of the main wing as canards do this by it self is pitch control but they are not pitch or roll control surfaces like tailplanes or elevons, the T-50 uses its tailplanes as roll and pitch control and wing trailing edge flaps and the LCA it uses its wing elevons (trailing edege flaps) as pitch and roll control.

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On aircraft such as the Eurofighter where canards move in sync, you would be correct. However, you are incorrect when you generalize this to argue that canards only provide pitch control. Canards can move independently and provide roll control just as tail planes can. Canards that move independently can also provided limited yaw control, due the ability to control strength of vortices generated by the canards.