J-20... The New Generation Fighter III

A minor point Engineer, but that video you showed with the J10 refueling is not a good example of typical cruise flight since the act of areo refueling requires significantly more course corrections and minor adjustments than cruise.

Yet, if the J10's canard deflections are barely noticeable during refueling, they would be smaller still if the plane was merely cruising.

It is pointless trying to reason with Mig29, all you are doing is wasting your time on a closed mind and deaf ears. Leave him to his fantasies, they do no harm to anyone.

I have no intention to reason with MiG. I'm just pointing out the errors in his post so that other members won't be misled.

Engineer said:

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:
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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.

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It`s incredible your ability to say the speed of those aircraft just at naked eye wow, you simple can not tell me at any moment the speed of any of those jets however Paul Metz knows at supercruise yes the aft tail will increase deflection

Since i have to be brief and not argue over the topic excesivly, i will say this i will take Paul Metz statement over your incredible speedometer eye calculation, because you can not even tell me at what speeds the jets were flying but Paul Metz can say to me F-22 at supercruise will increase deflection simple by increased drag as the first supersonic jets did and called the sound barrier and since i know basic aerodynamics and the history of the jet design i know transonic speeds will generate a very high drag on any aircraft particularly on the control surfaces reducing their ability to direct the aircraft.
see graphs


And if J-20 supercruises at Mach 1,3 the drag will be considerably high, at Mach 1,7 it might be slightly lower, but stealth will obviously reduce the aerodynamic efficiency of J-20, your theory the canards won`t increase deflection or RCS simply is based upon a forum myth, not real physics. read these papers

Regards argue with the links i am not going to argue anymore with your eye calculations.

MiG-29 said:

It`s incredible your ability to say the speed of those aircraft just at naked eye wow, you simple can not tell me at any moment the speed of any of those jets however Paul Metz knows at supercruise yes the aft tail will increase deflection

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Since i have to be brief and not argue over the topic excesivly, i will say this i will take Paul Metz statement over your incredible speedometer eye calculation, because you can not even tell me at what speeds the jets were flying but Paul Metz can say to me F-22 at supercruise will increase deflection simple by increase drag as the first supersonic jets did and called the sound barrier and since i know basic aerodynamics and the history of the jet design i know i know trsnsonic speeds will generate a very high drag on any aircraft particularly on the control surfaces.

Regards argue with the link i am not going to argue anymore with your eye calculations.

Click to expand...

Ok, it seems you are stuck on drag = RCS. So how does this work?

Let's say at Mach 1.5, the canard stay flat, but it will generate drag from the air circulation.... so how will this effect stealth? Will the radar beam detect the excessive air around the canard?

MiG-29 said:

It`s incredible your ability to say the speed of those aircraft just at naked eye wow, you simple can not tell me at any moment the speed of any of those jets however Paul Metz knows at supercruise yes the aft tail will increase deflection

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Click to expand...

Aft-tail is not canard.

MiG-29 said:

Since i have to be brief and not argue over the topic excesivly, i will say this i will take Paul Metz statement over your incredible speedometer eye calculation, because you can not even tell me at what speeds the jets were flying but Paul Metz can say to me F-22 at supercruise will increase deflection simple by increase drag as the first supersonic jets did and called the sound barrier and since i know basic aerodynamics and the history of the jet design i know i know trsnsonic speeds will generate a very high drag on any aircraft particularly on the control surfaces.

Regards argue with the link i am not going to argue anymore with your eye calculations.

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This is a fallacy called , as you are now trying to divert attention away with F-22. Paul Metz never flew the J-20, so while what he says regarding the F-22 may be true, his statements are also meaningless on the J-20. The simple matter is that you claimed canard needs large deflection for trim, and that claim turned out to be wrong based on the video evidences that we have seen; evidences such as , , and .

As far as the J-20 is concerned, Dr. Song was able to achieve high lift and low drag with the current configuration through the clever combination of aerodynamic devices, while achieving excellent stealth characteristics. His own statement is as follow:

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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jackliu said:

Ok, it seems you are stuck on drag = RCS. So how does this work?

Let's say at Mach 1.5, the canard stay flat, but it will generate drag from the air circulation.... so how will this effect stealth? Will the radar beam detect the excessive air around the canard?

Click to expand...

Canards are trim control devices, as speed increases, the deflection increases this drag is particularly high at Mach 0.9 to Mach 1.3, the canards and wing traling edges won`t stay flat, they can not, they are deflecting, if you have ever flown on an airliner you know even a Boeing 747 needs to trim even at 800km, you know it simply by experience, at Mach 1.2 the J-20 or any aircraft is experiencing excessive drag so deflections are higher, Paul Metz explains that in the interview. read the paper. regards

see graphs

MiG-29 said:

see graphs

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And if J-20 supercruises at Mach 1,3 the drag will be considerably high, at Mach 1,7 it might be slightly lower, but stealth will obviously reduce the aerodynamic efficiency of J-20, your theory the canards won`t increase deflection or RCS simply is based upon a forum myth, not real physics. read these papers

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Click to expand...

The plots do not prove your claim. Video evidences sch as , , and already shows your claim about canard requiring wild deflection to maintain trim to be false.

Stealth features does not automatically mean reduced aerodynamic efficiency. The F-22 is an excellent counter-example, being an aircraft with stealth features and also only aircraft in service that is able to supercruise at Mach 1.7. Like the F-22, the J-20 has excellent aerodynamics as well as stealth characteristics, as explained by Dr. Song.

As to the claim that canard increases RCS, it is merely a myth which has been repeated ad nauesum.

MiG-29 said:

Canards are trim control devices, as speed increases, the deflection increases this drag is particularly high at Mach 0.9 to Mach 1.3, the canards and wing traling edges won`t stay flat, they can not, they are deflecting, if you have ever flown on an airliner you know even a Boeing 747 needs to trim even at 800km, you know it simply by experience, at Mach 1.2 the J-20 or any aircraft is experiencing excessive drag so deflections are higher, Paul Metz explains that in the interview. read the paper. regards

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So you are saying, the faster the jet fly the more wildly the canards flap up and down?

And yes, I did read what he wrote, no where did he say that drag will increase RCS or that canard will flap uncontrollably up and down during Mach 1.2.

In fact, use your logic, when the air craft is flying supersonic, any large movement by the canard will result in extreme movement by the air craft, or maybe even break it apart.

Also in fact, you do know any aircraft with canard does have many other surfaces to control pitch and yaw right? So you don't even NEED to use canard at all to make a movement, in fact this is exactly what Eurofighter Typhoon have done. The fly by wire system on Thphoon is designed to minimise the canard RCS in flight, maintaining the elevon trim and canards at an angle to minimise RCS, aka making them as flat as possible during level fight.

So I ask you again, in that article where did Paul Metz says drag = more RCS? Where did Paul Metz say canard will make large movement during high speed?

jackliu said:

So you are saying, the faster the jet fly the more wildly the canards flap up and down?

And yes, I did read what he wrote, no where did he say that drag will increase RCS or that canard will flap uncontrollably
So I ask you again, in that article where did Paul Metz says drag = more RCS? Where did Paul Metz say canard will make large movement during high speed?

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He says this

All aircraft experience a loss of control effectiveness at supersonic speeds. To generate the same maneuver supersonically as subsonically, the controls must be deflected further.

simple like that, if you want to believe up to you, more deflection higher RCS.

MiG-29 said:

He says this

All aircraft experience a loss of control effectiveness at supersonic speeds. To generate the same maneuver supersonically as subsonically, the controls must be deflected further.

simple like that, if you want to believe up to you, more deflection higher RCS.

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1. Show us evidence of aircraft with canard flying at high speed and flapping it is canard constantly wildly up and down. In fact, you love to post videos, find a video on youtube of a canard jet fighter flying at flat at high speed, and show us the canard is constantly being moved up and down.

2. Did you not read canard is NOT THE ONLY control surface on a jet? The Typhoon have written into their FBW software to let other control surface to do more to control the movement of the jet, and minimize the movement of the canard itself. This is done just for RCS, I am pretty sure J-10 and J-20 uses similar FBW software as well.

Find us the DIRECT actual evidence, talk is cheap.