J-20 5th Gen Fighter Thread V

[Air Force Brat]

Especially if that eye happens to emit X-band radiation.

Well then you might get actual numbers, but that's the MkIII eyeball of some of you really smart guys, the AFB has done quite well for over a 1/2 century on two MKI eyeballs. Of course my landing gear question is somewhat absurd, but I'm rather certain that each of our posters get the point. Additional surfaces hanging in the breeze will in fact increase RCS despite all protestations to the contrary!

As I stated previously, It is my firm belief that the J-20 is a very sound design, and I fully expect that the Chinese will continue to "tweak" the RCS numbers on this bird as it begins to get serious.

Hey, could I get one of those eyeballs, I could use it when I'm driving the school bus! would that freak the little buggers out?? even if all you did was hang it from the mirror like fuzzy dice?? LOL

 

[FORBIN]

All of us would likely agree that the RCS of the frontal aspect of the aircraft is the most important aspect, as the aircraft is pointed in that direction. If you look at the FC-31, F-22, F-35 you see the forward fuselage, and the junction of the main wing leading edge.

On the F-22 and J-20 the leading edge of the wing has a very slight curving anhedral, just counting the Fuselage and Main wing juncture, and the verts and ventral fins, the total RCS is probably fairly similar on both aircraft??

So its not that the large canards forward of the main wing "destroy Low Observability"?? but that they are an additional forward facing surface, not masked in any way by the main wing, and they are on a completely different plane, with very significant dihedral, so they are a significant added surface area exposed to the oncoming radar beams.

In addition, if you maneuver the aircraft, those two surfaces deflect and increase the RCS even further, if you have to maneuver aggressively you could increase the forward reflective surfaces by 1/4 to possibly 3/4 in total area???

an aft mounted stabilator or elevator is masked by the main wing, even through fairly aggressive maneuvering, and even if aft edges are exposed, they are at an oblique angle, so they will never be able to contribute a significant amount to the static forward facing RCS.

So Yes, it is possible to a great degree, for an "educated eye" to look at any aircraft design, and give you a ball park figure on total RCS, from each of the significant aspect angles, in specific conditions of flight??

So, would an aircraft have a greater RCS with the landing gear UP, or with the landing gear DOWN???

For Chinese... ? but F-35 build essentialy for A2G missions have a frontal RCS more privileged but the serie F-35 ihave a less good RCS than the 1st demonstrator especialy on the sides in more initialy F-35 should get a RCS closer to F-22 remains very good.

 

[Quickie]

All of us would likely agree that the RCS of the frontal aspect of the aircraft is the most important aspect, as the aircraft is pointed in that direction. If you look at the FC-31, F-22, F-35 you see the forward fuselage, and the junction of the main wing leading edge.

On the F-22 and J-20 the leading edge of the wing has a very slight curving anhedral, just counting the Fuselage and Main wing juncture, and the verts and ventral fins, the total RCS is probably fairly similar on both aircraft??

I think, if I'm not mistaken, twix was referring to the canard surface being perpendicular to the fuselage surface which if it was really so would then be a significant RCS contributor from the side (not from the front). But we know it isn't the case because of the dihedral canards and the "V" shape of the fuselage bottom.

So its not that the large canards forward of the main wing "destroy Low Observability"?? but that they are an additional forward facing surface, not masked in any way by the main wing, and they are on a completely different plane, with very significant dihedral, so they are a significant added surface area exposed to the oncoming radar beams.

In addition, if you maneuver the aircraft, those two surfaces deflect and increase the RCS even further, if you have to maneuver aggressively you could increase the forward reflective surfaces by 1/4 to possibly 3/4 in total area???

an aft mounted stabilator or elevator is masked by the main wing, even through fairly aggressive maneuvering, and even if aft edges are exposed, they are at an oblique angle, so they will never be able to contribute a significant amount to the static forward facing RCS.

So Yes, it is possible to a great degree, for an "educated eye" to look at any aircraft design, and give you a ball park figure on total RCS, from each of the significant aspect angles, in specific conditions of flight??

So, would an aircraft have a greater RCS with the landing gear UP, or with the landing gear DOWN???

I won't be so sure of that explanation. 2 surfaces that are in the same plane would have the areas fully exposed from a viewing angle of a few degrees lower or higher.

Similarly 2 surfaces in slightly different planes may end up having one surface blocking the other against radar signals just by a change of viewing angle of a few degrees, which would lead to a smaller amount of reflective area.

 

[plawolf]

The argument canard moving affecting stealth also is at best highly exaggerated or worst totally nonsensical.

Yes, if the canards move, it will chance the cross section exposed to radar, but if the canard moves, so does the plane.

If the canards are moving so much as to start presenting a meaningful reflective surface (assuming they are not made out of radar transparent composites in the first place), the plane itself is doing some heavy manouvering, in which case the tiny increase in RCS from the canards is going to be meaningless compared to the spike from the plane showing its belly or back to the radar, as would happen if the canards did deflect so heavily.

In most realistic scenarios, a stealth fighter will only be making the bare minimum course changes necessary to optimise stealth, especially from the head-on engagement scenario.

Canard movement may bring a tiny spike in RCS, but that will be momentary, and likely immediately followed by a reduced overall RCS footprint from the plane as a whole after it better aligned its facing to optimise its stealth.

 

[Hyperwarp]

From Hui Tong: 2012 with 4x drop-tanks:

 

[jobjed]

From Hui Tong: 2012 with 4x drop-tanks:

More pictures and video link:

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The J-20 in question is prototype no. 2012.

 

[plawolf]

That will give it some legs! I wonder if the pylons are also ejected with the drop tanks on stealth aircraft to help preserve stealth. Otherwise 4 empty pylons will ruin the RCS of the bird...

 

[Totoro]

F22 was jettisoning pylons since early 2000s so i dont see why j20 shouldnt.

 

[Blitzo]

That will give it some legs! I wonder if the pylons are also ejected with the drop tanks on stealth aircraft to help preserve stealth. Otherwise 4 empty pylons will ruin the RCS of the bird...

I imagine during combat the aircraft would rarely fly with drop tanks at all, and that they are instead intended primarily for ferry purposes.

That said I'm sure they can eject the pylons along with the drop tanks if necessary.

 

[Totoro]

if anyone is interested, tanks are roughly 6.5 meters long and 0.75 m in diameter, which is quite similar to US 600 gallon tanks that F15 or F22 use, for example.

If so, four such tanks combined would haul roughly 7,3 tons of fuel.