J-20... The New Generation Fighter III

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Martian

Martian

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J-20 Mighty Dragon from a rare angle

srhm6.jpg

The J-20 DSI intake is prominent from a rear port-side view of the stealth fighter.

I just noticed the J-20 ventral fins shield the jet engines' radar and infrared signature from a lateral scan.

[Note: Thank you to HouShanghai and "HK299792458" for the picture.]
 
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Blitzo

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That's actually one of the best shots of the J-20 I've ever seen.
We're sure it's not psed?
 
Martian

Martian

Senior Member
Bltizo said:
That's actually one of the best shots of the J-20 I've ever seen.
We're sure it's not psed?
Click to expand...

I don't think it is PSed.

I tried to enhance the image by increasing the contrast and the colors started to distort. That usually happens only with real images. A person making a PSed image would use a consistent and smooth texture throughout the picture. It is unnecessary work to add sections of imperfect textures and shadows to a picture. This picture has imperfect textures and shadows in the middle-rear where the depth of the shadow varies.

However, I probably need another year of experience to make definitive judgments on whether a picture is PSed or not. I am also reluctant to discuss the reasons why I think a picture is legitimate or PSed. I'm worried that a PSer will read my comments and adjust accordingly. There is only a limited set of factors that influence my judgment.
 
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Blitzo

Blitzo

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Martian said:
I don't think it is PSed. I tried to enhance the image by increasing the contrast and the colors started to distort. That usually happens only with real images. However, I probably need another year of experience to make definitive judgments on whether a picture is PSed or not.
Click to expand...

Yes, I think this photo must have been real, but was maybe tampered with in some way (self censoring?). We can't see indications of the side weapon bays at all and there seems to be something inconsistent at the area of the fuselage between the LERXs.

Also, the sky seems suspiciously clear >_>
 
Martian

Martian

Senior Member
Bltizo said:
Yes, I think this photo must have been real, but was maybe tampered with in some way (self censoring?). We can't see indications of the side weapon bays at all and there seems to be something inconsistent at the area of the fuselage between the LERXs.

Also, the sky seems suspiciously clear >_>
Click to expand...

In any case, I am beginning to think the ventral fins were intentionally added to shield the engines and increase the J-20's lateral radar and infrared stealth.
 
Blitzo

Blitzo

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Martian said:
In any case, I am beginning to think the ventral fins were intentionally added to shield the engines and increase the J-20's lateral radar and infrared stealth.
Click to expand...

I can't imagine how the ventral fins would aid radar VLO -- the less surfaces you have, the better (even if they are aligned, shaped and covered with RAM). They might shield some of the engine's moving exhaust, but the stream of hot air behind it will still be very visible.

Aerodynamics is the most logical reason for the inclusion of ventral fins.
 
Martian

Martian

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J-20 ventral fins contribute to lateral radar and infrared stealth

Bltizo said:
I can't imagine how the ventral fins would aid radar VLO -- the less surfaces you have, the better (even if they are aligned, shaped and covered with RAM). They might shield some of the engine's moving exhaust, but the stream of hot air behind it will still be very visible.

Aerodynamics is the most logical reason for the inclusion of ventral fins.
Click to expand...

The RAM-coated ventral fins will either absorb or reflect the incoming radar wave. Looking at the picture, an incoming radar wave will be reflected into the sky. The hottest part of a plane is the jet engine. The jet exhaust is noticeably cooler. Hence, the ventral fins shield the jet engines from lateral view and contribute to lateral infrared stealth.

5ikw6.jpg

Infrared signature of aircraft showing jet exhaust fumes
(Credit: BAE Systems. Link:
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)
 
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Blitzo

Blitzo

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I understand that the ventral fins, if applied with RAM, aligned and shaped correctly will have a lower RCS than one having ventral fins that is not.
But clearly a J-20 with ventral wings will have a larger or at least equal RCS than J-20 without, from all aspects. Again, an aircraft with more exposed surfaces (like wings, for example) will have a larger RCS than an aircraft with fewer exposed surfaces.

As for IR... here's an excellent video of last years faranborough air show, taken by both a normal and IR camera. You can see that almost all aircraft have pretty large exhausts trailing behind them (including F-22, typhoon, A400m, and a variety of other commercial airliners). The F-22 minimizes its own a little likely due to its special nozzles, but even that can be quite detectable.
Of course I'm not sure how applicable that would be for a 5th gen SRAAM (AIM-9X, ASRAAM, IRIS-T, PL-10 etc) but I think we can safely say the ventral fins are there primarily for aerodynamics and the slight benefit for IR hiding is more incidental.

[video=youtube;gxWWUiblCjg]http://www.youtube.com/watch?v=gxWWUiblCjg[/video]
 
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latenlazy

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Bltizo said:
I understand that the ventral fins, if applied with RAM, aligned and shaped correctly will have a lower RCS than one having ventral fins that is not.
But clearly a J-20 with ventral wings will have a larger or at least equal RCS than J-20 without, from all aspects. Again, an aircraft with more exposed surfaces (like wings, for example) will have a larger RCS than an aircraft with fewer exposed surfaces.

As for IR... here's an excellent video of last years faranborough air show, taken by both a normal and IR camera. You can see that almost all aircraft have pretty large exhausts trailing behind them (including F-22, typhoon, A400m, and a variety of other commercial airliners). The F-22 minimizes its own a little likely due to its special nozzles, but even that can be quite detectable.
Of course I'm not sure how applicable that would be for a 5th gen SRAAM (AIM-9X, ASRAAM, IRIS-T, PL-10 etc) but I think we can safely say the ventral fins are there primarily for aerodynamics and the slight benefit for IR hiding is more incidental.

[video=youtube;gxWWUiblCjg]http://www.youtube.com/watch?v=gxWWUiblCjg[/video]
Click to expand...

I noticed that in one scene the F-22's exhaust wasn't that bad. I'm going to assume that's without its afterburners on.

On another note, the more I look at the J-20's engine fairings, the more it just doesn't look right. It feels like the nozzle and fairings create a strange geometry that seems to indicate a less than ideal fit.
 
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kroko

Senior Member
latenlazy said:
On another note, the more I look at the J-20's engine fairings, the more it just doesn't look right. It feels like the nozzle and fairings create a strange geometry that seems to indicate a less than ideal fit.
Click to expand...

Perhabs because it was designed for a different engine than the one it has now
 
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