J-20... The New Generation Fighter II

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s7s7s7

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Chinese have not powerful jet engine. Concentrating more resources in aerodynamic research is a natural choice. The article mentioned chinese built asia's largest scale wind tunnels near CAC.
 
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MiG-29

MiG-29

Banned Idiot
pugachev_diver said:
QUoting from expert again, "canard and conventional don;t make much difference in terms of stealth performance, doesn;t matter if its conventional or canard, all their stealtiness are calculated assuming they are in cruising state, and almost completely neglected when maneouvering or only do minimals, but this doesn't influence its figure (I guess he meant the overall RCS value). Canard layout and conventionals' only difference is that canard has an extra surface in the front compared to conventionals. But the front view of the plane wouldn't change. (like a sword, doesn;t matter how long it is, you can only see a small point when its pointed at you). the canard itself can be made to be stealthy. canard and conventional layouts' difference in stealth performance can only be substantial when the RCS is lowered down to 0.001 and it has to be scanned by very powerful radars with specific wavelengths."

The American engineers' original intention was that: canards are too complicated, it takes up too much space internally, especially that it creates too much drag that it kills F22's emphasis on supersonic cruise. When you have unhuman level engine and really good materials and especially highly mature avoinics, why create further troubles for ourself. F22 emphasizes on supersonic speed, utilizing its swept butterfly wings and F119 makes it reach perfect harmony. In the late 90s, the Americans concluded this would dominate the world theatre for 20-30 years.

Doesn't matter if its close coupling or distant coupling, both are detrimental to thenext generation fighter, why so?

To be Continuted.....
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All aircraft need trimming even at straight flight, first no aircraft flies with laminar air without any type of drag or turbulance, if you have flown you know even a 747 has wind gusts that force it to trim, canards always will trim the jet, and unstable aircraft like the J-10 or Eurofighter also has a strong pitch up tendency, this also increases trimming.
The reason the americans do not use canards in the F-22 are two, first is thrust vectoring, by using thrust vectoring as pitch control, the F-22 only uses its horizontal tail as roll devices reducing drag and increasing roll rates and pitch rates.
The other is the F-22 is unstable, so the aircraft has a strong pitch up tendency so its horizontal tail uses lift to trim the F-22 increasing the total lift, how is it? well by increasing lift aft of the wing by means of the horizontal tail, the pitch up nose tendency is balanced therefore trim is reduced and total lift increased.
 
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MiG-29

MiG-29

Banned Idiot
Engineer said:
J-20 design approaches as reflected in researches on canard configurations of 1990's

Quoting from expert again, "canard and conventional layouts don't make much difference in terms of stealth design; stealtiness is calculated assuming the aircraft is in cruising state, with flight control surfaces assumed to be fixed. When maneouvering, stealth is ignored or only minimals migitations are taken, but this doesn't influence its figure (I guess he meant the overall RCS value). The only difference in canard and conventional layout is that canard has an extra surface in the front (of the wings) compared to conventional layout. However, the theory of controlling direction of radar reflection is the same: leading edge of the canards being paralleled to the trailing edge, and internal structure of the canards can be optimized to enhance stealth characteristics. The main difficulty in management of radar reflection lies in the wingroot of the canards, and is as difficult as managing radar reflection of the root of leading edge slats in a conventional layout. The difficulties are the same, and the migitiation techniques are basically identical. Canard and conventional layouts' difference in stealth performance is only noticable when the RCS is lowered down to 0.001 m2. Radar reflection from canards is more difficult to manage because of their small size, thus have poorer performance when shined by radars with middle to long wavelength. Migitation techniques involve combination notch-band absorption and special coating. Such problems can also be found in conventional layout, but the wings can hide the horizontal stabilizers to a certain degree." In conclusion, wings in a canard layout is large, with long wingroot leading to better stealth charcteristics; Vertical stabilizers are far from the canards with little interference; All aspect stealth (of the wings) is slightly better than conventional layout. However, the present of canards require more effort and complicate techniques to migitate, but there are little difference between canard and conventional layout. The difficulties in combining stealth with aerodynamics are about the same.
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up to a degree you are right but at some level you are using 1980s aerodynamics, canards were a fashion in the late 1970s and early 1980s to increase lift on wings, the Su-27K used them to increase lift and vortex control thus reducing landing and take off speeds, the Europeans used them for increasing the AoA handling of delta wings, the IAI Lavi to increase instantaneous turn rates with respect the F-16 conventional platform without increasing the TWR or wing area.
The Su-35,Su-33KUB and Su-34 used canards to increase longitudinal unstability on aircraft that increased nose weight due to heavier radars or cockpits.
However the F-22 uses thrust vectoring for pitch control thus making canards redundant.
The Russians went a step ahead by adding LEVCONs or leading edge vortex control devices and thrust vectoring.
Are canards less stealthy? the answer is yes, first is because they are not shielded by the wing and second because they require shapes and positions that not always go along with stealth requirements.
ask your self why the J-20 has canards and LERX at the same time? and why the J-10, Eurofighter and Rafale have canards at a different horizontal position with respect the canards on the J-20?.
The ideal stealth fighter is the YF-23 but the YF-23 was less agile than the YF-22.
 
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AssassinsMace

AssassinsMace

Lieutenant General
Well I've being seeing this image but wasn't sure if it's just an old pic not released. CDF blog seems to suggest it's a new recent pic and is #2002.


271308491592e3fa837bd71.jpg
 
Semi-Lobster

Semi-Lobster

Junior Member
AssassinsMace said:
Well I've being seeing this image but wasn't sure if it's just an old pic not released. CDF blog seems to suggest it's a new recent pic and is #2002.
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I saw those images to. We finally might get some more flight time eventually! I'm surprised they made out #2002 on it though, I can barely see the plane at all in the first place.
 
Blitzo

Blitzo

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AssassinsMace said:
Well I've being seeing this image but wasn't sure if it's just an old pic not released. CDF blog seems to suggest it's a new recent pic and is #2002.


271308491592e3fa837bd71.jpg
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Looks like it was taken in a similar position to where the first J-20 blurry pics were taken... at Chengdu. Are we sure this isn't just the same set of photos? :O
 
C

Centrist

Junior Member
Well, if indeed the "first" flight wasn't really the first. The plane that flew could have been 2002, it was just repainted temporarily to give the illusion of being the first prototype.
 
Blitzo

Blitzo

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Centrist said:
Well, if indeed the "first" flight wasn't really the first. The plane that flew could have been 2002, it was just repainted temporarily to give the illusion of being the first prototype.
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... Or the plane that flew was 2001 and afterwards it was flown out west, while we're seeing first pictures of 2002 right now?
I don't see what would make the repaint 2002 to look like 2001, or vice versa.
 
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s7s7s7

New Member
MiG-29 said:
All aircraft need trimming even at straight flight, first no aircraft flies with laminar air without any type of drag or turbulance, if you have flown you know even a 747 has wind gusts that force it to trim, canards always will trim the jet, and unstable aircraft like the J-10 or Eurofighter also has a strong pitch up tendency, this also increases trimming.
The reason the americans do not use canards in the F-22 are two, first is thrust vectoring, by using thrust vectoring as pitch control, the F-22 only uses its horizontal tail as roll devices reducing drag and increasing roll rates and pitch rates.
The other is the F-22 is unstable, so the aircraft has a strong pitch up tendency so its horizontal tail uses lift to trim the F-22 increasing the total lift, how is it? well by increasing lift aft of the wing by means of the horizontal tail, the pitch up nose tendency is balanced therefore trim is reduced and total lift increased.
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That's incredible if it's ture. For conventional layout aircraft with relaxed stability as F-22 usaully, the lift center still lies behind the center of gravity. And at supersonic cruise, lift center moves backward which makes pitch down tendency stronger.
 
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