J-20 5th Gen Fighter Thread V

[tidalwave]

WS-10 is similar to AL-31 in performance but it is not AL-31 so it is not plug-and-fly. The jet needs to re-undergo flight-testing for weight distribution/inlet/flight control optimization to switch to the Taihang and it won't come with any performance increase (possibly even a decrease?), so is it worth the effort? I don't know the answer to that but if I were in AVIC and wanted to reduce use of AL-31 in favor of Taihang, I'd first start using WS-10X on whole batches of J-10B/C before opting to go to J-20 since work has already been done in that direction.

a good case is J15. How much time they spend on undergo testing with WS10?

 

[latenlazy]

a good case is J15. How much time they spend on undergo testing with WS10?

Quite a while, it seems.

 

[manqiangrexue]

a good case is J15. How much time they spend on undergo testing with WS10?

I don't know. There seems to be J-15 flying with both but they already had experience changing flankers over from AL-31 to WS-10. With J-10, first WS-10 powered prototype was 1035. A few years later, 2 J-10B/C use WS-10. They're probably still taking data from them. It doesn't seem like a fast process. Probably because there's no rush.

 

[tidalwave]

I don't know. There seems to be J-15 flying with both but they already had experience changing flankers over from AL-31 to WS-10. With J-10, first WS-10 powered prototype was 1035. A few years later, 2 J-10B/C use WS-10. They're probably still taking data from them. It doesn't seem like a fast process. Probably because there's no rush.

it's worth it. Let's give most permisstic case, WS15 has issues at 2019.
Using WS10x means controlling your production at your own hand.
Still purchasing AL31F at 2019 for J20 is Not.

 

[manqiangrexue]

it's worth it. Let's give most permisstic case, WS15 has issues at 2019.
Using WS10x means controlling your production at your own hand.
Still purchasing AL31F at 2019 for J20 is Not.

Yeah, if you factor in WS-15 having problems, then the more problems it has, the more delays it runs into, the more worth it it becomes to shift over, especially if WS-10G is real and works out (155kN with TVC??). But if WS-15 is coming along really smoothly and you can shift over to WS-15 in 2018/19, then is it still worth it? Do you want the trouble your J-20 techs into learning how to maintain 3 types of engines/layouts?

 

[gambit]

The remark about the serrations around the F-35 jet pipe reminded me that the Boeing 787 too has such serrations. These are to reduce noise and as there is fear in the Netherlands that the noise from F-35 will prove to be more obnoctious than that of F-16 are we sure that F-35 is not trying to reduce noise and not radar returns?

You have unknowingly sort of explained how the serrations reduced both noise and EM signatures.

In designing a low radar observable body, there must control of...

- Quantity of radiators
- Array of radiators
- Modes of radiation

In learning the basics of radar detection, the classroom often uses infinite bodies and edges in order to isolate a particular behavior. But in real life, any body is a finite body and eventually the EM signals must leave that body, which mean that on said body, any structure that will allow the EM signals to enter free space is effectively a radiator. That means the wing, that small comm antenna, or that tiny gouge on the surface of a panel, each is a radiator. This is rule 1.

Rule 1 says you must minimize the quantity of instances where the EM signals can enter free space.

In designing a low radar observable body, the corner reflector structure where two flat plates are perpendicular to each other is a huge no-no. This is rule 2.

Rule 2 says you must be careful on how structures are in relation to each other. Since each structure is an exit point for those EM signals, you must minimize their interactions with each other wherever they leave those structures.

When EM signals are on a body, that body would have different types of surfaces, from flat planes to curvatures. The types of surface geographical features produces different ways on how those EM signals exit the body. Edges produces diffractions. Depending on approach angle, surfaces can produces traveling waves which produces leaky waves which are not as significant as specular waves. This is rule 3.

Rule 3 says you must control how these modes of radiation leave the structures.

Those serrations came from the application of those three rules, whether it is sound waves or EM waves.

 

[delft]

I heard there will 3 production lines for J20.
One with AL31F, another one with WS10 series, and the final one will be with WS15.

The numbers produced per year will be lower than that of Flankers. So production will be in batches. If there is to be a version with WS-10 there will be one or more prototypes produced in a separate prototype shop just as there will be for the WS-15 version after which the batch production facility will be adapted.

I quarrelled with the system trying to limit the cursive to [/i]If.

 

[gambit]

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

No, it is neither exaggerated nor 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.

This is how a radar 'sees' an aircraft...

...As a cluster of voltage spikes, which are produced by various protruding structures into the radar stream.

If you have one spike, why would you want to produce another ?

If you already have 10, why would you want the 11th ?

You can reasonably argue that the 11th is meaningless since there are already 10 significant structures to give the seeking radar a reasonably good target, but you would be missing the point that the target is in 3D space and maneuvering, which mean that the 11th may be statistically significant at one point but not at another during ACM.

In radar detection, or rather trying to avoid detection, the last thing you want is to produce even a hint of target scintillation. That 11th voltage spike can be that attractant for the radar computer to remain focused on you as you maneuver and your canards are appearing and disappearing -- electromagnetically speaking.

 

[manqiangrexue]

No, it is neither exaggerated nor nonsensical.


This is how a radar 'sees' an aircraft...

...As a cluster of voltage spikes, which are produced by various protruding structures into the radar stream.

If you have one spike, why would you want to produce another ?

If you already have 10, why would you want the 11th ?

You can reasonably argue that the 11th is meaningless since there are already 10 significant structures to give the seeking radar a reasonably good target, but you would be missing the point that the target is in 3D space and maneuvering, which mean that the 11th may be statistically significant at one point but not at another during ACM.

In radar detection, or rather trying to avoid detection, the last thing you want is to produce even a hint of target scintillation. That 11th voltage spike can be that attractant for the radar computer to remain focused on you as you maneuver and your canards are appearing and disappearing -- electromagnetically speaking.

So the point basically sums up as "anything can cause an extra small amount of radar spike and that may be the deciding factor between staying stealthy and being detected." That's true, and the best way to remain stealthy is to have nothing, but you need moving control surfaces to control your plane. You either deflect your canard or you deflect your horizontal stabilizer (you may get more maneuvering with less deflection with a canard than with a tail since the canard directly lifts the head). It's just a matter of whether you put that moving surface on the plane's aft (tail-positioned) or fore (canard position). The fore position brings it about 15 meters closer to the radar (in J-20's case), and that's the only reason I can see that might make any tiny difference at all when compared to horizontal tails. You essentially presented a reason for why canards are less stealthy than having nothing, but I think the discussion is whether canards are significantly less stealthy than tail-positioned horizontal stabilizers. In that picture you presented where the aircraft was scanned basically from the belly or top (which, as plawolf pointed out, could be it's relative position to the enemy radar if it were to use either canards or rear-mounted horizontal stabilizers to maneuver vigorously), I see absolutely no difference resulting from whether these control planes were to be placed to the aft or fore of the wings.

 

[Air Force Brat]

YEE HAA! Great Balls of Fire! I hear "Highway to the Danger Zone!" playing in the back-ground?

looks like he has a little "forward stick" in there as he passes through inverted?? can some one find a pic of this event with the canards visible, I would love to see their deflection, I anticipate that they are also deflected downward to hold the nose up as the aircraft passes through the inverted position??

oh, and thank you by78, outstanding pictures showing our sweet little Chinese Chick inverted, very pretty, and as I have stated before, she appears to fly "very well"?

likely a great deal better than the little Mig 1.44, which supposedly had less than an hour of recorded flight time??? as I have repeated Dr. Songs assertion, that this is a very difficult configurations to "harmonize" in the FCS, as the FCS has to be talking to both ends, and that relationship changes as the airspeed and angle of attack change???? woo hoo!

I always appreciate likes on these old posts, so I'm going to remind everyone once again that Dr. Song stressed how complex the J-20's FCS really is. This airframe has been designed for a more powerful engine which really isn't that big of a deal, in fact I would be rather certain that engine mounts, controls, and ducting are already designed for the day when the WS-15 begins testing on the J-20.

But for those fellow posters who think the real reason for the SU-35 deal, is simply to gain access to F-117S which, could then just be "adapted" to the J-20. This just isn't going to happen, to add OVT to this FCS would require basically "starting over" on the FCS, and I just don't see the logic there?