J-20... The New Generation Fighter III

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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This is the truth. The mistake someone is making is that he assumes the canard to be flapping wildly at ridiculous angle to maintain trim. In reality, during cruise when RCS is most important, the canard barely makes any movement. Here is a video proof:
[video=youtube;icQeBc9jHaA]http://www.youtube.com/watch?v=icQeBc9jHaA[/video]

When large movement of control surfaces is needed or even TVC is involved, that means the plane is fighting for its life. Stealth is completely meaningless when the aircraft is already seen.

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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The plots on are good illustrations of proper stealth design. Such design calls for low RCS as long as the observer lies within a cone projected from the nose. What this means is low RCS even when the aircraft is not viewed head-on, as is the case when a ground radar is looking at the plane. For an aircraft such as the F-22, such scenario means the wing cannot shield the tailplane from the radar, yet the aircraft must maintains low RCS. This is where edge alignment comes in.

Edge alignment means the canard will reflect much of the radar energy away from the source, just like a wing does. So, the statement about canard being not hidden thus bad for RCS is a bad claim, on the account that such a statement is made from photographs and not the view of the radar.

Engineer said:

This is the truth. The mistake someone is making is that he assumes the canard to be flapping wildly at ridiculous angle to maintain trim. In reality, during cruise when RCS is most important, the canard barely makes any movement. Here is a video proof:



When large movement of control surfaces is needed or even TVC is involved, that means the plane is fighting for its life. Stealth is completely meaningless when the aircraft is already seen.

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haha what a bad example, the J-10 is not even flying supersonic, first the tanker is obviously a Tu-16/H-6 which by the way can not even fly supersonic, the trimming at supersonic speeds is Mach 1.4-1.7 where the fifth generation will fly as regular speeds.


Obviously, the re-fueling is at much much lower speeds, and obviously it won`t be at speeds near transonic since the max drag is given at transonic speeds, drag increases so much that you need a fully moveable aft-tail in fighters or foreplane in most cases

Engineer said:

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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2. Main design contradictions:

The design requirement for stealth brings new difficulties to the aerodynamic design. Frontal stealth capability imposes new restrictions on both the sweep angle of the leading edge and air intake configuration. Lateral stealth requires the proper alignment of the aircraft's cross sectional shaping and the vertical stabilisor configuration. These restrictions and requirements must be considered during the earliest phase of designing the aerodynamic configuration


quote well Lateral stealth requires the proper alignment of the aircraft's cross sectional shaping and the vertical stabilisor configuration


have you hear of corner reflectors?

MiG-29 said:

haha what a bad example, the J-10 is not even flying supersonic, first the tanker is obviously a Tu-16/H-6 which by the way can not even fly supersonic, the trimming at supersonic speeds is Mach 1.4-1.7 where the fifth generation will fly as regular speeds.


Obviously, the re-fueling is at much much lower speeds, and obviously it won`t be at speeds near transonic since the max drag is given at transonic speeds, drag increases so much that you need a fully moveable aft-tail in fighters or foreplane in most cases

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Excuses. From the J-10 video, it is obvious that canard does not flap wildly to trim, contrary to what you have imagined. Rather, the canard maintains a stable position. showing the exact same thing. The simple fact is that an aircraft at cruise requires little to no deflection of control surfaces. In other words, edge alignment is preserved thus maintaining the stealth of the aircraft.

MiG-29 said:

2. Main design contradictions:

The design requirement for stealth brings new difficulties to the aerodynamic design. Frontal stealth capability imposes new restrictions on both the sweep angle of the leading edge and air intake configuration. Lateral stealth requires the proper alignment of the aircraft's cross sectional shaping and the vertical stabilisor configuration. These restrictions and requirements must be considered during the earliest phase of designing the aerodynamic configuration


quote well Lateral stealth requires the proper alignment of the aircraft's cross sectional shaping and the vertical stabilisor configuration


have you hear of corner reflectors?

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The quote "lateral stealth requires the proper alignment of the aircraft's cross sectional shaping and the vertical stabilator configuration" does not contain the word "coplanar". What does this mean? It means you got caught lying red-handed, and Dr. Song never mentioned lift surfaces being placed in coplanar configuration as one of the stealth requirements.

We know that contrary to your wild claims, J-20 has excellent stealth and supersonic drag characteristics. From Dr. Song's paper:

The design team made a future fighter proposal based on the points raised by this article. The proposal employs lift-body LERX canard configuration. It is unstable in both the lateral and yaw directions. The proposal employs small aspect ratio wings with medium back sweep angle, relatively large dihedral canards, all moving vertical stabilizers far smaller than those on conventional fighter aircraft, and S-shaped belly intakes. According to our assessment, the proposed aircraft will have excellent supersonic drag characteristics, high AOA lift characteristics, high AOA stability and controllability, and excellent stealth characteristics.

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Engineer said:

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.

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Now your talking turkey, and I will buy this, honestly I think there are advantages and disadvantages to both configurations, and like using drag chutes, some of it is just cultural even within different companies. For example look at twin engine fighter aircraft of WW-II, the Lockheed P-38 and the Gruman F7-7, two different approaches, both very fine aircraft on the US side.

Engineer said:

Excuses. From the J-10 video, it is obvious that canard does not flap wildly to trim, contrary to what you have imagined. Rather, the canard maintains a stable position.

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showing the exact same thing. The simple fact is that an aircraft at cruise requires little to no deflection of control surfaces. In other words, edge alignment is preserved thus maintaining the stealth of the aircraft.

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They say an F-35-b Joint Strike Fighter did so with a KC-130J Hercules at the Eglin Air Force Base in Florida.

MCAS officials say previous aerial refueling operations with the F-35 have been done but only with test planes.

During the mid-air refueling the aircraft took on about 2,000 pounds of fuel at a speed of about 265 miles per hour at an altitude of 15,000 feet


it is obvious you forget the speeds air refuelling takes place, F-35 at merely less than 500km/h.

your example is an absurd since the J-10 is flying at similar speeds way bellow supercruise, since the Tu-16 has a mere max speed of 1000km/h and its air refuelling speed is around 500-600km/h

Mig-29, this is getting into the dangerous territory again. Calm down your need to defend every single points or else this will turn into another never ending discussion on same points.

MiG-29 said:

They say an F-35-b Joint Strike Fighter did so with a KC-130J Hercules at the Eglin Air Force Base in Florida.

MCAS officials say previous aerial refueling operations with the F-35 have been done but only with test planes.

During the mid-air refueling the aircraft took on about 2,000 pounds of fuel at a speed of about 265 miles per hour at an altitude of 15,000 feet

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it is obvious you forget the speeds air refuelling takes place, F-35 at merely less than 500km/h.

your example is an absurd since the J-10 is flying at similar speeds way bellow supercruise, since the Tu-16 has a mere max speed of 1000km/h and its air refuelling speed is around 500-600km/h

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More excuses. It is nothing but a wish of yours that canard needs large deflection for trim, because you desperately needs excuses to claim J-20 to be defective. The simple reality is that the position of canard is relatively fixed while the aircraft is at cruise. This fact is here for all to see in the following video:
[video=youtube;icQeBc9jHaA]http://www.youtube.com/watch?v=icQeBc9jHaA[/video]

This video is such a perfect example because it has long footage of J-10 at cruise with canard in view. Your claim of my example being absurd is nothing other than an act of denial because the video proves you wrong, simple as that.

. What we see is the canard remaining at one position, instead of deflecting wildly for trim as you would like to imagine.

. Again, we see the canard stays at one position while the aircraft is in cruise.

illustrates how the canard remains at one position while the aircraft is in cruise.

In the next video, we see another aircraft with canard instead of the J-10. This aircraft is the Rafale. There are some beautiful shots of the aircraft in cruise where the canard stays fixed, such as , , and . The canard moves only when the aircraft undergoes a maneuver.
[video=youtube;CmAjrIVertU]http://www.youtube.com/watch?v=CmAjrIVertU[/video]

In short, while the aircraft is in cruise and RCS is important, there is no large deflection of the canard to return radar energy. Any movement is within a few degrees, with the radar energy still reflected away from the source due to edge alignment. The claim that canard hurts RCS remains unsubstantiated.