J-20 5th Gen Fighter Thread VI

plawolf said:

From a purely theoretical standpoint, canards can add to RCS for two main rreason reason.

1) they are on a different plain to the wings. The tails of the F35 and F22 are on the same plain as the main wings, which can shield them from incoming radar from the front.

2) when the canards move to steer the plane, that movement can cause small RCS spikes

Now, the key question is weather those RCS increases are large enough to matter.

For the J20, it has much smaller vertical stabilisers compared to the F22, so if you are like at looking at the sum total of surface area exposed to incoming radar, it’s hard to say that the J20 has a net significantly bigger area.

Point 2 could also be significantly mitigated with advanced FBW and/or TVC, whereby you have a stealth mode, under which the canards are locked in place, with a combination of other control surfaces, differential engine thrust and TVC to steer the plane without them.

You would only activate the canards in WVR combat, at which point stealth is meaningless in any case.

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RCS on canards can be mitigated by RAM along the leading edge and the internal spar. Second, by using a radar pass through material for the main canard itself, like composite. Third, the structural spar itself it sharp edged, there cannot be rounded, as in rounded pipe or cylindrical structures.

Boeing's sixth gen fighter proposal uses canards.

MastanKhan said:

Hi,

Really---. Canards just don't happen to pop out of thin air---there is a substance and technology behind it.

An aircraft manufacturer who has no experience of canards in their aircraft---just suddenly does not put canards on its aircraft--. There is solid science and engineering behind it---. There is function and utility behind it---

And until and unless you don't have the engineering behind it---you won't put canards on your aircraft---.

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Its not like they have been testing this for a long time, along with a digital fly by wire control system.

MastanKhan said:

Hi,

Really---. Canards just don't happen to pop out of thin air---there is a substance and technology behind it.

An aircraft manufacturer who has no experience of canards in their aircraft---just suddenly does not put canards on its aircraft--. There is solid science and engineering behind it---. There is function and utility behind it---

And until and unless you don't have the engineering behind it---you won't put canards on your aircraft---.

Click to expand...

Don't understand your response to Phead at all. Eurofighter consortium never built a fighter with canards before Typhoon. So what? There's always a first step. Just because you didn't see all the work behind the scenes on J-9 (obsolete project) and the work on J-10, does not mean the canards must have arrived by some form of magic or copying. Although this does not negate the possibility that the entire thing was copied directly or otherwise. That is another conversation entirely.

Just can't understand your point here. Try to say what you mean directly. Are you saying that because CAC did not seem to have prior experience with canards, the fact they came out with one product using canards means it must be copied? or are you saying something else. My comprehension is usually quite good but i'm lost here.

Tam said:

RCS on canards can be mitigated by RAM along the leading edge and the internal spar. Second, by using a radar pass through material for the main canard itself, like composite. Third, the structural spar itself it sharp edged, there cannot be rounded, as in rounded pipe or cylindrical structures.

Boeing's sixth gen fighter proposal uses canards.


View attachment 47413

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Without knowing very detailed internal structural and materials information, it would be hard to get into specifics, which is why I was keen to keep this largely theoretical.

In terms of pure theory, it is hard to see how they could totally eliminate all possible RCS for a few key reasons.

1) all aspect stealth and internal moving parts.

With a moving surface, you need motors/actuators to drive them.

If you make the whole canard out of radar transparent materials, you have the problem of radar hitting those motors/actuators when coming from anything other than directly ahead.

That is why while radar transparent materials have been around for a long time, it’s only with supercomputers allowing the application of continuous curve shaping that allowed the likes of the F22 and J20 to be designed and built.

It’s all about compromises. You take a very small frontal RCS hit to achieve a massive side on RCS gain.

The use of radar transparent materials would be more easily applied to the J20’s vertical rails. Since all the motors and acutators that drive them are in the root structure; since that is a single piece structure with no internal moving parts, and since you need to be pretty much directly above the plane to get a return on the root motors (at which point you will be getting a huge return from the whole plane in any case), you can make the whole thing out of radar transparent materials without needing to worry about internal structures becoming reflectors, as would be the case of the F22 V tails were made entirely out of radar transparent materials.

With the new stealth nozzles, the J20’s ventricular streaks could also now be made out of radar transparent material, since the ones without stealth nozzles would likely have been RAM, as one of their main design goals would be to shield the round nozzles from radars emitting from the sides.

2) Material sciences.

All radar ‘transparent’ materials are only transparent up to a point afaik. There is perfectly radar transparent materials.

So you will always get a tiny return, and the more area you have, the bigger the return.

Now please note that all of this is theoretical. Depending on the material and design. The extra RCS from having the canards come be the equivalent of a few grains of sand. In which case it’s purely a theoretical increase that has zero real world impact.

That is the key to remember here.

A lot of the detractors of canards bring out theoretical arguments that are hard to argue with, since they are true. But whether the impact of those tiny RCS increases raises the overal RCS of the plane in any meaningful way is the real question we should be focusing on instead of trying to argue that there is zero impact.

plawolf said:

Without knowing very detailed internal structural and materials information, it would be hard to get into specifics, which is why I was keen to keep this largely theoretical.

In terms of pure theory, it is hard to see how they could totally eliminate all possible RCS for a few key reasons.

1) all aspect stealth and internal moving parts.

With a moving surface, you need motors/actuators to drive them.

If you make the whole canard out of radar transparent materials, you have the problem of radar hitting those motors/actuators when coming from anything other than directly ahead.

That is why while radar transparent materials have been around for a long time, it’s only with supercomputers allowing the application of continuous curve shaping that allowed the likes of the F22 and J20 to be designed and built.

It’s all about compromises. You take a very small frontal RCS hit to achieve a massive side on RCS gain.

The use of radar transparent materials would be more easily applied to the J20’s vertical rails. Since all the motors and acutators that drive them are in the root structure; since that is a single piece structure with no internal moving parts, and since you need to be pretty much directly above the plane to get a return on the root motors (at which point you will be getting a huge return from the whole plane in any case), you can make the whole thing out of radar transparent materials without needing to worry about internal structures becoming reflectors, as would be the case of the F22 V tails were made entirely out of radar transparent materials.

With the new stealth nozzles, the J20’s ventricular streaks could also now be made out of radar transparent material, since the ones without stealth nozzles would likely have been RAM, as one of their main design goals would be to shield the round nozzles from radars emitting from the sides.

2) Material sciences.

All radar ‘transparent’ materials are only transparent up to a point afaik. There is perfectly radar transparent materials.

So you will always get a tiny return, and the more area you have, the bigger the return.

Now please note that all of this is theoretical. Depending on the material and design. The extra RCS from having the canards come be the equivalent of a few grains of sand. In which case it’s purely a theoretical increase that has zero real world impact.

That is the key to remember here.

A lot of the detractors of canards bring out theoretical arguments that are hard to argue with, since they are true. But whether the impact of those tiny RCS increases raises the overal RCS of the plane in any meaningful way is the real question we should be focusing on instead of trying to argue that there is zero impact.

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Those motors and actuators are embedded in the fuselage itself. As said, the canard is an all moving surface, which means it is moved entirely, by an external force. Its not like a wing where there are internal moving parts to move flaps, edges, and ailerons.

Another thing is, that the canard as a surface, even if its made of radar reflective material, the reflections are always directed away from the frontal source since there is no angle where it can reflect radio waves forward. The biggest cause of reflection is likely on the leading edge of the canard, and even this, its not angled straight back to the forward source.

The canard has on its leading edge, a strong reinforcing spar that runs the entire length of the forward edge of canard. This spar is potentially reflective, but it also reflects away from the front.

The main wing poses the bigger threat of radar return due to its much thicker leading edge, which can be formed with curved surfaces. Any rounded and curved surface are prone to radar highlighting.

CGI missile?

And maybe fuel tank ...

Hyperwarp said:

CGI missile?

View attachment 47439

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The doesn't seem right. Also, on the fine print on the bottom right corner, it says the missile is photoshoped on.

ougoah said:

Don't understand your response to Phead at all. Eurofighter consortium never built a fighter with canards before Typhoon. So what? There's always a first step. Just because you didn't see all the work behind the scenes on J-9 (obsolete project) and the work on J-10, does not mean the canards must have arrived by some form of magic or copying. Although this does not negate the possibility that the entire thing was copied directly or otherwise. That is another conversation entirely.

Just can't understand your point here. Try to say what you mean directly. Are you saying that because CAC did not seem to have prior experience with canards, the fact they came out with one product using canards means it must be copied? or are you saying something else. My comprehension is usually quite good but i'm lost here.

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Hi,

Off course they did---. They had the israeli engineering helping them in all fields.

CAC had no experience with canard type frontline aircraft---. Suddenly from our of nowhere they manufacture two aircraft---the J10 and the J20---both very successful ventures---.

Miracles simply don't happen in the world of mechanical engineering if you do not have a history of manufacturing tier 1 product behind you.