Chengdu J-20 5th Generation Aircraft News & Discussions

[gambit]

I want to quickly point out that the two hexagonal 'fine grill meshes' on the J-20 are most likely similar in principle to the F-117's inlets.

As long as the holes on the 'fine grill mesh' are smaller than the wavelength of the enemy radar, it should appear as a flat surface on radar and thus remain stealthy.

Most likely, that came from Kopp and his crowd over at APA.

Let us take a look at the microwave oven and why it cook things inside but not outside...

Microwave Ovens

Considering the frequency of 2,450 MHz, the wavelength of microwave oven radiation is about 12 cm...

...the microwaves are effectively blocked from getting out into the room because the holes in the metal screen on the microwave oven door are about 1 mm in diameter compared to a 120 mm wavelength for the microwaves. The wavelength of the microwaves is about 120 times the size of the holes, and can't "see" the holes to get out.

Note the highlighted: That the operating frequency of the microwave oven is 120 times the size of the screen mesh, or grill, on the oven's door. It is technically incorrect to say that no microwaves got out of the oven by passing through the door's mesh.

By federal regulation, microwave ovens are limited to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface. This limit is far below the level known to harm people. The microwave radiation would be expected to drop off according to the inverse square law, so at 20 inches it would be down by about a factor of 100.

Microwaves do escape from the oven by going through the door's mesh. This is real physics.

When long wavelengths impact raindrops some of the signal's energy travels on the raindrop's surface and wraps around the body. Some of this energy radiate off into free space and some is reabsorbed by the main part of the signal. The energy that is radiated into free space is so small that it is attenuated in its travels. So for the microwave oven, when some microwaves do get through the door's wire mesh, whatever energy that is left after the federally mandated level of 5 milliwatts will be so weak that it will be attenuated through that short distance of 20 in that they will be harmless.

Now we go to the F-117's intake mesh or grill.

Most targeting radars operate in the famous X-band, which is...

Radio Bands and Radar Bands Frequency Chart

2-4 GHz 15-7.5 cm ................S Band

8-12 GHz 3.75-2.50 cm......... X Band

Remember, the microwave oven's operating freq is effectively in the S-band: 2.45ghz.

If...

- In the interest of preventing the majority of an X-band radar signal from entering the F-117's intake tunnel...

- We are to keep the same ratio of 120 to 1 like how the microwave oven is designed...

- And if the X-band is the targeted wavelength of 3 cm.

Then: What is 120 times smaller than 3 cm? Will this mesh allows sufficient air for engines to survive? Remember, for the microwave oven, the operating freq is 120 times larger than the openings on the door's mesh/grill.

Three centimeters = about 1.2 inch.

What is 120 times smaller than 1.2 inch?

The fact is this...

The F-117's intake mesh/grill is precisely designed to allow enough air to support the engine and to diffuse any entrant signals by multiple reflections so that each reflection will be attenuated by absorber linings.

 

[siegecrossbow]

Canards are definitely different. More squary now.

All they did was trim the sharp corner on the rear-facing tip, presumably for RCS reduction purposes. They also did the same thing on the vertical stabilizer. However, some also speculate that trimming the tails helped reduce vibrations due to interactions of the tail with the vortices generated by the canards and LERX.

 

[Esc8781]

Now THIS is proper panel edge alignment.

Notice that virtually all edges and gaps within the airframe are swept at an angle and not perpendicular to the direction of flight. This is very important. The PAK FA does not have this kind of fit and finish.

The picture isn't available anymore.

 

[j20blackdragon]

 

[nomi007]

 

[j20blackdragon]

 

[Kompromat]

I am amazed by the quality of this awesome machine.

 

[Informant]

Why is the glass canopy not like the F-22, without any structural support? Wouldnt it bounce of radar signals/waves. Pardon my lackof knowledge.

 

[Kompromat]

Why is the glass canopy not like the F-22, without any structural support? Wouldnt it bounce of radar signals/waves. Pardon my lackof knowledge.

Structural support helps in bird strikes.

 

[j20blackdragon]

EOTS and DAS locations.

 

[siegecrossbow]

Why is the glass canopy not like the F-22, without any structural support? Wouldnt it bounce of radar signals/waves. Pardon my lackof knowledge.

Weight saving/easier ejection. If I recall correctly, the F-35 uses a similar setup so they don't need to lift the whole one-piece canopy during ejection process. I actually liked the older one-piece canopy better, but there are trade-offs.

 

[trident2010]

You're looking at undisputed air superiority over Asia.

You meant to say after 8-10 years when hopefully it is fully operational and upto the western standards, that too if US leaves the Asia and other major countries didn't field new airplanes. Looks good as a strike bomber though

 

[nomi007]

Any news on HMD development?

 

[j20blackdragon]

You meant to say after 8-10 years when hopefully it is fully operational and upto the western standards, that too if US leaves the Asia and other major countries didn't field new airplanes. Looks good as a strike bomber though

You're already looking at the pre-production J-20. It won't be very long now.

At the rate China is advancing, you should probably be expecting something like this in 8-10 years.

The J-20 could be the least of your concerns at that point.

 

[Superboy]

You meant to say after 8-10 years when hopefully it is fully operational and upto the western standards, that too if US leaves the Asia and other major countries didn't field new airplanes. Looks good as a strike bomber though

J-20 operational by 2017, 3 years from now, not 8 to 10 years.