Chengdu J-20 5th Generation Aircraft News & Discussions

[gambit]

Yes Since It would be Forced to use His radar in Active mode and all the Stealth goes in Drain... Passive Sensors like IRST is a way to go... against Stealth planes and to keep ones plane Stealth.... May be It doesn't applies to Chinese design.. which is offcourse Unique and laws of Physics for the outside world does not apply... according to the self esteemed stealth/VLO expert we have here.

It is a combination of both and at appropriate time to be backed up with sufficiently sophisticated data processing. In a high EM environment, being able to sense or pick up as many EM transmission sources as possible is worthless without the requisite data processing prowess to sort out what is useful from what is not, from one moment to the next. Part of that data processing is ranging information of a target and IR data does not provide that information.

The solution is the extremely judicious use of the active sensor -- radar -- backed up intense data processing of raw passively collected data of any EM environment. The most easily processed data is direction, as in where is that signal coming from, the active sensor -- radar -- is then redirected towards that potential threat direction and use sparingly to gather basic target information. From that point on, if the target produce matches of certain criteria, such as range, intrusion into a threat 'bubble', or heading because if the target is inside said threat 'bubble' but is heading outward then said target can be considered irrelevant, then the active sensor use can be adjusted according to needs.

This is where the F-22 shines and the F-35 is even better.

 

[gambit]

I have no idea. I was answering Firemaster's question on a solution to a non-stealthy and protruding IRST on the T-50/Pak-Fa.

If a stealth aircraft has a nose designed to house a recessed IRST then a retracting door can be used to unveil the IRST only when needed. With this design, the fighter aircraft remains stealthy until the IRST is needed. This minimizes the possibility of detection.

Another route is to redesign the IRST to minimize its footprint. Huge advances have been made in electronics and optics in the past decades. However, you would have to ask electronics and optics experts.

This is where you are mistaken.

A passive sensor is useful only when it is in use and because it is passive, it should, if not must, be used all the time. Your eyes and ears are passive sensors. Your hands are active sensor and they are directional. You use your passive sensors to direct where your active sensors must go. A recessed compartment render your passive sensor highly directional, must like looking through a tube or up from the bottom of a well.

 

[gambit]

You have just proved my point. QED

Next to his obsession with accompanying 'J-20' with 'Mighty Dragon', he is very nearly obsessed with those worthless 'Thanks' by fellow Chinese who pushed that button whether each of them had anything 'useful' to say or not. Childishly obsessive.

 

[Martian2]

This is where you are mistaken.

A passive sensor is useful only when it is in use and because it is passive, it should, if not must, be used all the time. Your eyes and ears are passive sensors. Your hands are active sensor and they are directional. You use your passive sensors to direct where your active sensors must go. A recessed compartment render your passive sensor highly directional, must like looking through a tube or up from the bottom of a well.

You're not making any sense.

No stealth designer would compromise a plane's stealthiness for the sake of a passive sensor. The only reason Sukhoi didn't bother to address the stealthiness issue for the IRST probe is that it is minor compared to the other much larger problems on the T-50/Pak-Fa third prototype.

Sukhoi hasn't fixed a single stealth design problem in two years.

 

[gambit]

You're not making any sense.

No stealth designer would compromise a plane's stealthiness for the sake of a passive sensor. The only reason Sukhoi didn't bother to address the stealthiness issue for the IRST probe is that it is minor compared to the other much larger problems on the T-50/Pak-Fa third prototype.

Much more sense than you, and backed up with related experience to boot. Your argument is based upon the presumption that all structures are detrimental to 'stealth', as if there is a standard for 'stealth' in the first place. You clearly are over your head in this subject.

 

[ptldM3]

Threshold -- Get it?

-- the man you often quote -- an 'idiot'. Congratulations, you are the first debater I know who calls his supporting source stupid.

Why is this surprising? While he uses sources that acknowledge the obvious such as 90 degree angles or reflectors are bad for stealth he than shamelessly claims that Chinese aircraft such as the J-10 and WZ-10 are ‘stealthy’ even though they violate the principles of stealth. And the entire threshold argument is valid considering most people (and I have cited sources) acknowledge that there is an unofficial threshold for aircraft to qualify as stealth aircraft, Rebecca grant has a scale in which she or a source of hers list the stealth threshold at below 1m2. And I’m sorry but I really do doubt that a monstrosity such as the WZ-10 will get anywhere close to 1m2.

That is why it is laughable for you to declare definitively that a certain structure is 'not stealthy'. Based upon what measurements have you PERFORMED? Your crayola based ray tracing or full range and anechoic chamber testing? This is why it is laughable for you to say that those saw-toothed geometric absorber devices are 2D while the IRST device is 3D. May be it should be YOU who should have his eyes checked. Just like the other Chinese boys here who have no relevant experience, you do not understand words in their proper technical contexts and proceed to make absurd pronouncements based upon your flawed understanding and nationalistic zeal.

The guy has a gift. He is able to seamlessly predict RCS’s off the internet. He is in high demand, I bet aerospace companies around the world would save millions if they hired him. Why spend millions on anechoic chambers and conduct countless hours of testing? Why develop software and supercomputers to model rcs, or higher engineers when good ol’ Martian can use the eye ball test .

I bet he would cringe or go in denial mode if he read what one F-117 engineer said about rcs.

Go back to CDF and sinodefence where other gullible Chinese will mindlessly swallow what you peddle.

He received thanks in a post where he bragged about receiving thanks, it just shows how useful his posts are.

News for you, kid, your source -- howstuffworks -- give only the most general information of anything. Not wrong. Just not enough.

In RCS control, a concave structure is far far deadlier to RCS contributorship than a convex structure.

I brought up the convex argument before. Although he passionately agrees that spherical or convex objects omit large rcs returns he can not see all the curvature and convex shaping in the J-20, which includes but is not limited to the DSI, the pods underneath the wings, the aft part of the fuselage, the engine nozzles, the upper portion of the cockpit, the lower chin, the upper nose and the upper fuselage. Some of this is very subtle yet some areas such as lower chin and DSI are extreme example of convex shaping. Likewise, as I mentioned numerous times he adamantly defended the WZ-10 even though it violated the same principles he preaches. I’m guessing he has multiple personality disorder.

You're not making any sense.

No stealth designer would compromise a plane's stealthiness for the sake of a passive sensor. The only reason Sukhoi didn't bother to address the stealthiness issue for the IRST probe is that it is minor compared to the other much larger problems on the T-50/Pak-Fa third prototype.

Sukhoi hasn't fixed a single stealth design problem in two years.

Stop posting the same garbage, especially when it is not applicable to the conversation. You seem to have some sort of sexual fetish with that picture that overrides all impulses to the point that you are uncontrollably posting the same crap repeatedly no matter what the subject matter is.

And the only one that is not making any sense is you. The real reason they don’t bother with the IRST is because these prototypes are aerodynamic test beds with the number 3 being the avionics test bed.

It’s still unbelievable that you still point out that the gaps between the pak-fa intakes and fuselage are a problem when they are basically identical to the gaps on the F-22, the same gaps that you conceded are not a problem on the F-22. I also am quite aware that you were unaware of the vents in the YF-23 and that the YF-23 test pilot acknowledged that the YF-23 had a smaller rocs than the YF-22. As usual you are a hypocrite and a shameless one at that.

Most of the rcs violators that you listed in that picture are present on the WZ-10 and to a much larger degree. Yet you have no problem calling the WZ-10 stealthy. Chinese aircraft are excluded from the rules right? In fact a Chinese aircraft can have 90 degree reflectors and still be stealthy.

 

[Martian2]

Illustration of the need for a flat underside to achieve stealth

For example, let me illustrate why the T-50's uneven underside is not stealthy.

The uneven underside on the T-50/Pak-Fa third prototype creates a natural 90-degree angle. This allows enemy radar to reflect off the fuselage, bounce off the inside-face of the air-inlet, and return to the transmitter/detector for detection.

The enemy radar can see the T-50/Pak-Fa, because of the uneven underside. This result should not surprise you. The Su-30 (which is not stealthy) also has an uneven underside like the T-50/Pak-Fa.

When the same enemy radar (either airborne or ground-based) tries to detect a Chinese J-20 Mighty Dragon, it fails.

Both the J-20 Mighty Dragon and F-22 Raptor have smooth and flat undersides to deflect radar away from the transmitter/detector. On this criterion, it is obvious the J-20 and F-22 are stealthy. It is also equally obvious the uneven underside of the T-50/Pak-Fa third prototype is not stealthy.

If Sukhoi ever fixes this problem then I would credit Sukhoi with another stealth characteristic. However, right now, the T-50/Pak-Fa third prototype is deficient in comparison to the J-20 and F-22 across at least 10 stealth design requirements.

[Note: In both pictures, I performed a ray trace of the incoming radar and its reflection off of the underside of the Russian T-50/Pak-Fa third prototype and China's J-20 Mighty Dragon. You are familiar with a ray trace, because you see visible light bouncing off mirrors all the time.

Radar is an electromagnetic wave like visible light. The only critical differences are that radar has a much longer wavelength and it's invisible to the naked eye. Otherwise, a ray trace of radar resembles visible light.]

 

[ptldM3]

Illustration of the need for a flat underside to achieve stealth

For example, let me illustrate why the T-50's uneven underside is not stealthy.

The uneven underside on the T-50/Pak-Fa third prototype creates a natural 90-degree angle.

Too bad the fuselage is canted. By your logic the same thing would happen if the EM energy hit the side of the J-20's fuselage. And since you like pointing out potential and imaginary flaws in the pak-fa, let me point out some for the J-20 as well.

I also forgot to highligh the curvature in the nose sinse you keep claiming rounded surfaces are a big no, no.

And you have to be kidding me when you say the pak-fa has the same round and tall fuselage as the SU-30, they are geometrically very different and the result of an extremely flat fuselage. If the J-20's aft fuselage would be flattened you would get the same thing.

 

[amalakas]

Next to his obsession with accompanying 'J-20' with 'Mighty Dragon', he is very nearly obsessed with those worthless 'Thanks' by fellow Chinese who pushed that button whether each of them had anything 'useful' to say or not. Childishly obsessive.

That doesn't take away the fact that in engineering terms, his comments and arguments are found wanting and at least I as an engineer cannot let him do that. It is unethical.

The amount of work it takes for a plane from paper design to the point where it can get off the ground is mind boggling, I cannot allow him to taint that with his mighty dragon fascination.

 

[Martian2]

Too bad the fuselage is canted. By your logic the same thing would happen if the EM energy hit the side of the J-20's fuselage. And since you like pointing out potential and imaginary flaws in the pak-fa, let me point out some for the J-20 as well.

I also forgot to highligh the curvature in the nose sinse you keep claiming rounded surfaces are a big no, no.

And you have to be kidding me when you say the pak-fa has the same round and tall fuselage as the SU-30, they are geometrically very different and the result of an extremely flat fuselage. If the J-20's aft fuselage would be flattened you would get the same thing.

The canards are unimportant, because the main wing and side fuselage (at exactly the right angle) would have reflected that particular incoming radar wave. Except for takeoffs, landings, and dogfights, the J-20 canards will be locked into place at the same level as the main wings. The presence of the canards has a marginal effect.

Your perfect-angle problem also applies to the main wings of the F-22 Raptor and T-50/Pak-Fa. You are making the error of comparing apples to oranges.

You missed the point of my analysis. The T-50/Pak-Fa's uneven underside (e.g. fuselage and airducts) will create many radar reflections at different angles. This makes the T-50/Pak-Fa very unstealthy.

Also, your point on the small radar reflection from RAM-covered aileron controls applies to all fighters (including the F-22 and T-50/Pak-Fa). Therefore, all planes would have the same deduction. That is why I omit aileron controls from my list. It's tiny and all planes have it. Not worth discussing.

The point remains. The undersides of the J-20 and F-22 are stealthy. The T-50/Pak-Fa underside is far from stealthy.

 

[Wet Shirt Contest]

Illustration of the need for a flat underside to achieve stealth

For example, let me illustrate why the T-50's uneven underside is not stealthy.

The uneven underside on the T-50/Pak-Fa third prototype creates a natural 90-degree angle. This allows enemy radar to reflect off the fuselage, bounce off the inside-face of the air-inlet, and return to the transmitter/detector for detection.

The enemy radar can see the T-50/Pak-Fa, because of the uneven underside. This result should not surprise you. The Su-30 (which is not stealthy) also has an uneven underside like the T-50/Pak-Fa.

When the same enemy radar (either airborne or ground-based) tries to detect a Chinese J-20 Mighty Dragon, it fails.

Both the J-20 Mighty Dragon and F-22 Raptor have smooth and flat undersides to deflect radar away from the transmitter/detector. On this criterion, it is obvious the J-20 and F-22 are stealthy. It is also equally obvious the uneven underside of the T-50/Pak-Fa third prototype is not stealthy

If Sukhoi ever fixes this problem then I would credit Sukhoi with another stealth characteristic. However, right now, the T-50/Pak-Fa third prototype is deficient in comparison to the J-20 and F-22 across at least 10 stealth design requirements.

[Note: In both pictures, I performed a ray trace of the incoming radar and its reflection off of the underside of the Russian T-50/Pak-Fa third prototype and China's J-20 Mighty Dragon. You are familiar with a ray trace, because you see visible light bouncing off mirrors all the time.

Radar is an electromagnetic wave like visible light. The only critical differences are that radar has a much longer wavelength and it's invisible to the naked eye. Otherwise, a ray trace of radar resembles visible light.]

Troll There Is No Rule Saying You Have To Have A Flat Fuselage To Achieve >Stealth< Although The Flat Fuselage Is the Simplest way that assures the least chance of any signals coming back. You can have an underside that is anything but flat, what is important is controlling and redirecting EM energy.

LOOK At F-117 It has Many Faceted Surfaces, Some In Close Proximity For today's Standards All that Faceting Is NOT Necessary but the point is the complex faceting on the F-117 caused EM energy to behave in a complex manner. The same philosophy holds true for the Ruskies PAK-FA. YOU Clearly Don't Know a JACK!!!

 

[Martian2]

New recent photographs of J-20 Mighty Dragon.

J-20 is parked among other fighter planes.

On the left, one J-10 single-seat Vigorous Dragon. Four J-10S twin-seat fighter-trainers in the middle. J-20 on the right.

A closer look at J-20 cockpit area.

[Note: Thank you to SiegeCrossbow for the pictures.]

 

[Tracy]

Canards are MOVING parts. so they DO increase RCS (j20 canards are BIG one) Right ?

 

[j20blackdragon]

Another small update.

J-21

A scale-down model of J-21 was unveiled by the 601 Institute at the first International UAV Innovation Grand Prix held in Beijing in September 2011. It was first rumored in April 2011 that 601/SAC are developing a 4th generation medium multi-role stealth fighter as J-21 which would complement the heavier J-20 (see above). The aircraft has a conventional design featuring twin engines and DSIs similar to both American F-22 and F-35. The prototype could initially be powered by the 8.5t class WS-13A turbofan but later by the new 9.5t class "medium thrust" engine (WS-13B/Tianshan?). A full-scale metal model was probably built in early 2011. The first prototype has been under construction since late 2011. First flight was projected to be in September 2012. J-21 (dubbed AMF/Advanced Multi-role Fighter?) is expected to be promoted at the international market as a low-cost alternative to American F-35.

- Last Updated 2/25/12

Chinese Military Aviation | China Air Force

Huitong confirms the authenticity of the J-21 on his own forum.

the authenticity of that J-21 model was confirmed by the admin at cjdby.net, J-21 also aims at the international market so it is expected to be declassified later this year

Chinese Military Aviation - j2x

 

[amalakas]

The canards are unimportant, because the main wing and side fuselage (at exactly the right angle) would have reflected that particular incoming radar wave. Except for takeoffs, landings, and dogfights, the J-20 canards will be locked into place at the same level as the main wings. The presence of the canards has a marginal effect.

Your perfect-angle problem also applies to the main wings of the F-22 Raptor and T-50/Pak-Fa. You are making the error of comparing apples to oranges.


You missed the point of my analysis. The T-50/Pak-Fa's uneven underside (e.g. fuselage and airducts) will create many radar reflections at different angles. This makes the T-50/Pak-Fa very unstealthy.

Also, your point on the small radar reflection from RAM-covered aileron controls applies to all fighters (including the F-22 and T-50/Pak-Fa). Therefore, all planes would have the same deduction. That is why I omit aileron controls from my list. It's tiny and all planes have it. Not worth discussing.

The point remains. The undersides of the J-20 and F-22 are stealthy. The T-50/Pak-Fa underside is far from stealthy.

Canards locked in place?? i don't think so...

Since you are so nice pointing out the deficiencies of other designs, perhaps we should point out some of the things that don't
add up with your magnificent theories.

first of all assuming the canards are ok for stealth we need to move to the shape and position of the canards.

the trailing edge of the J-20 MIGHTY DRAGON (whoo hoo) canard does NOT align with any other on the craft.
I am pretty sure the leading edge of the canard does not align either but I will wait for someone to use a good top view of the plane to do this.

The canards are on a dihedral which means the edge of the trailing edge (!) is over the entire upper wing area.. I call this a huge source and a huge reflector, I don't know how you call it..

The canards are followed by a lerx ..

the trailing edge of the J-20 MIGHTY DRAGON !!! appears not aligned with the main control surfaces of the plane, i.e. the canards.

the angles of the fuselage and the nozzles do not align with others on the plane.

seriously ..look it up ...