J-20... The New Generation Fighter III

Originally Posted by jackliu

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?

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 graphshttp://www.patagoniaballistics.com/i...p_image001.jpg
http://www.wfis.uni.lodz.pl/edu/Proposal/image117.jpghttp://adg.stanford.edu/aa241/drag/images/image489.gifhttp://aerorocket.com/HTV-3X/HTV-3X_Classical.gif

Originally Posted by MiG-29

see graphshttp://www.patagoniaballistics.com/i...p_image001.jpg
http://www.wfis.uni.lodz.pl/edu/Proposal/image117.jpghttp://adg.stanford.edu/aa241/drag/images/image489.gifhttp://aerorocket.com/HTV-3X/HTV-3X_Classical.gif

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 Volume Wave DragAeroRocket Development of the HTV-3X Spaceplane

The plots do not prove your claim. Video evidences sch as this, this, and this 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.

Originally Posted by MiG-29

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

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?

Originally Posted by jackliu

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?

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.

Originally Posted by MiG-29

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.

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.

Originally Posted by jackliu

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 is merely repeating a myth.

Stealth design calls for a conic region in front of the plane in which RCS remains low. For example:


For full aspect stealth, the aft region also has reduced RCS:


You can read more about it here. If you want to see what the RCS for an actual plane looks like, Carlo Kopp's website has some plots showing the RCS profile of J-20 based on simulations.

In any case, an aircraft does not need to fly directly at a radar to be stealthy. An aircraft with its nose pointing away from a radar source is still stealthy, as long as the radar remains in the conic region. Similarly, the aircraft is still stealthy when flight control surfaces deflecting a few degrees. The effects on RCS will be negligible as long as deflection remains small. Large deflection such as 10° or 20° only occurs when the aircraft is maneuvering, which would mean the aircraft is already seen and any talk about RCS would be pointless.

Originally Posted by MiG-29

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.

That particular statement from Paul Metz has nothing to do with RCS. Furthermore, his statement refers to supersonic maneuvering, not cruise where RCS is important. Your claim that deflection of control surfaces cause increase in RCS is based upon a myth.

Looks like I'm going to have to step in here again. Let's calm things down and stop this topic. I can see where this is heading from previous arguments. You are not going to convince the other side. Everyone has already stated their case, let's move on. Any more posts on this issue will be deleted.

If correct that 2001 & 2002 are now both at Yanglian ... then this must be an older image or .... ????

(image from: http://www.f y j s.cn/bbs/htm_data/27/1210/814904.html)


Deino

Originally Posted by Deino

If correct that 2001 & 2002 are now both at Yanglian ... then this must be an older image or .... ????

(image from: http://www.f y j s.cn/bbs/htm_data/27/1210/814904.html)
Deino

But first of all, when or where was it confirmed that 2002 had gone to Yanliang? If it was indeed somewhat confirmed, then when was this current picture taken?

Originally Posted by Player99

But first of all, when or where was it confirmed that 2002 had gone to Yanliang? If it was indeed somewhat confirmed, then when was this current picture taken?

Not sure about a confirmation and I need to correctmy post above, it was taken in May / June.

2003 prototype? It's too hard to tell at this point IMHO.

It just looks like a canopy with a cover over it, it could be any aircraft under there. To present that as evidence of another J20 is just trying too hard.

More J20 prototypes will undoubtably appear in due time. No need to force the issue. All we need to do is be patient.

Originally Posted by plawolf

It just looks like a canopy with a cover over it, it could be any aircraft under there. To present that as evidence of another J20 is just trying too hard.

More J20 prototypes will undoubtably appear in due time. No need to force the issue. All we need to do is be patient.

You can see the angular shape of the nose which is consistent of a stealth fighter. I don't think is some cover.