J-20... The New Generation Fighter II

Re: Revised final estimate for J-20 canards' radar return energy is 1.035 x 10^-17

I have another point. With the length of the canard, i.e. the distance from the fuselage to the tip 2 meters, the chord at the fuselage will be only about a meter or a meter and a half. With a thickness chord ratio of 7 %, which is pretty large, we get a thickness of less than 10 cm.

Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

challenge said:

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assessment by the Russian aviation writer,good read.

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His assessment that the J-20 will be used for anti ship purposes are dashed by the simple fact that there are no AShMs at the moment which can fit internally and still have good range and manouverability.

And if it were an uncompromising supercruiser/missile carrier then why not go for a clean delta rather than canard delta?

Then there was He Weirong's statement of 4S, with supermanouverability one of the key aspects of the 4th generation fighter -- and I'm sure the PLAAF recognize the value of agility, with years of J-10 and flanker experience, I can't imagine they would let go of that for their new premier fighter craft and modify it instead for a role usually relegated to naval aviation.

The article has a good deal of technical and professional sounding words, but I question if the writer knows what he is talking about. Can anyone familiar with aerodynamics give a rundown on the article?

Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Bltizo said:

His assessment that the J-20 will be used for anti ship purposes are dashed by the simple fact that there are no AShMs at the moment which can fit internally and still have good range and manouverability.

And if it were an uncompromising supercruiser/missile carrier then why not go for a clean delta rather than canard delta?

Then there was He Weirong's statement of 4S, with supermanouverability one of the key aspects of the 4th generation fighter -- and I'm sure the PLAAF recognize the value of agility, with years of J-10 and flanker experience, I can't imagine they would let go of that for their new premier fighter craft and modify it instead for a role usually relegated to naval aviation.

The article has a good deal of technical and professional sounding words, but I question if the writer knows what he is talking about. Can anyone familiar with aerodynamics give a rundown on the article?

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There is also the case of large canard deflection and differential canards and the proliferation of flight surfaces on the plane. All those things may adversely affect stealth. Why would the Chinese add them unless they provide insane maneuverability?

Re: Revised final estimate for J-20 canards' radar return energy is 1.035 x 10^-17

delft said:

I have another point. With the length of the canard, i.e. the distance from the fuselage to the tip 2 meters, the chord at the fuselage will be only about a meter or a meter and a half. With a thickness chord ratio of 7 %, which is pretty large, we get a thickness of less than 10 cm.

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Thank you for pointing out the "thickness chord ratio of 7%." From my calculations, the radar energy return from the J-20's canard requires multiplying by a factor that has 17 decimal places. This is virtually undetectable.

If new insights warrant a significant recalculation then I will incorporate your observations into the next update. As it currently stands, the J-20's canards have an insignificant effect on the aircraft's stealthiness.

no_name said:

I think TVC is only turned on for high maneuvering demands. Turning them on all the time will wear parts out much faster. A fighter plane should be able to fly normally with TVC switched off, also it will affect with giving the plane a sustained, stable thrust. Rudders changes the pointing orientation of the plane more, TVC changes the orientation of the velocity vector more. They complement each other.

Tail-less designs I think right now is still more suitable for platforms not demanding in maneuverability, like the B-2, UAV strike aircraft and the F-22 fighter-bomber version.

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Practice has shown that Su-30MKI's TVC does not improve maneuverability much, but it does involve fuel economy because it reduced the use of traditional control surfaces (which creates drag). However, that does create a maintenance problem.

So I think 3D TVC is wrong direction. the F-22 3D TVC is the right approach.

And I'm not expert but if your aircraft have a fast enough roll rate then 2D TVC can do what 3D TVC can.

I think TVC is all avout instantaneous rather than sustained turn rates. It moves the thrust force into the desired orientation before the planeform itself is aligned in that direction.

I also wonder if there is advantage in having thrust vectoring in which the two engine can TVC in different directions. So if one up and one down then maybe the aircraft will roll?

Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Bltizo said:

His assessment that the J-20 will be used for anti ship purposes are dashed by the simple fact that there are no AShMs at the moment which can fit internally and still have good range and manouverability.

And if it were an uncompromising supercruiser/missile carrier then why not go for a clean delta rather than canard delta?

Then there was He Weirong's statement of 4S, with supermanouverability one of the key aspects of the 4th generation fighter -- and I'm sure the PLAAF recognize the value of agility, with years of J-10 and flanker experience, I can't imagine they would let go of that for their new premier fighter craft and modify it instead for a role usually relegated to naval aviation.

The article has a good deal of technical and professional sounding words, but I question if the writer knows what he is talking about. Can anyone familiar with aerodynamics give a rundown on the article?

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He didn't mention the LERX. Maybe it was not obvious to him.

J-20 design combine canards, LERX and delta wing together to generate alot of extra lift. What this may imply is that you do not need to raise the aircraft into an as high AoA compared to other aircrafts for the same lift force. This I think means less drag and energy bleeding for maneuvering.

edit: however if you have a longer aircraft the cross sectional area will be present to the airflow for less AoA.

Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Eh, what we found out when Victor Belenko defected is that the MiG-25's engines wouldn't last twenty minutes at Mach 3, and the airframe was steel. Yes, steel. It was almost a disappointment when we finally had one to examine. The airplane was, in fact, greatly over rated in the press.

Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Ambivalent said:

Eh, what we found out when Victor Belenko defected is that the MiG-25's engines wouldn't last twenty minutes at Mach 3, and the airframe was steel. Yes, steel. It was almost a disappointment when we finally had one to examine. The airplane was, in fact, greatly over rated in the press.

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Not really sure where you're going with that. My initial reaction was, "Uh, yeah, we know that already." But you might be trying to make some point that I'm not catching. Would you mind clarifying?

Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

kyanges said:

Not really sure where you're going with that. My initial reaction was, "Uh, yeah, we know that already." But you might be trying to make some point that I'm not catching. Would you mind clarifying?

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I don't get his point either. The J-20 has been demoted to anything from a experimental plane to a non-manueverable interceptor to a dedicated ground attack aircraft by most Western sources. I don't see how Western sources are exaggerating the threat at all.