J-15 Carrier Multirole Fighter thread


Max Demian

Junior Member
Registered Member
The difference between an F-18, Rafale to a J-15D is not likely to be that significant in the context of a powerful AESA.
Easy to say, but can you back that up? Radar detection range is proportional to the fourth root of RCS. So on a first glance, a small relative decrease in RCS will not significantly impact radar detection range. I will come back to this.

However, when we consider jamming, as we should in any realistic scenario, the jammer power required to achieve the same effectiveness drops linearly with the reduction in RCS.

According to some debatable numbers (best that I have), the Superhornet has just 35% the RCS of J-15 (no data on J-15D). However, the Rafale-M has merely 5% the RCS of J-15 vulgaris in S-band and higher bands!

Therefore, if we assume equally effective jammers and radars on both sides, the Rafale-M will be detected at 20 times lower range than the J-15 would. I would call this significant.

Finally, in absence of jamming, again assuming equal radar performance, the Rafale-M would be detected at about 0.47 the range that the J-15 would.
 
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Air Force Brat

Brigadier
Super Moderator
Couldn't stop myself.
(from huskit.com)
I don't know your source, but that is highly inaccurate, it very well may benefit from size, materials, marginally from shaping, but you strip all that junk off, and you're still gonna get a strong radar return..

If no one was seeing Rafale on radar, that would be all anybody could talk about, and that's just NOT the case sir.
 

Tam

Major
Registered Member
Easy to say, but can you back that up? Radar detection range is proportional to the fourth root of RCS. So on a first glance, a small relative decrease in RCS will not significantly impact radar detection range. I will come back to this.

However, when we consider jamming, as we should in any realistic scenario, the jammer power required to achieve the same effectiveness drops linearly with the reduction in RCS.

According to some debatable numbers (best that I have), the Superhornet has just 35% the RCS of J-15 (no data on J-15D). However, the Rafale-M has merely 5% the RCS of J-15 vulgaris in S-band and higher bands!

Therefore, if we assume equally effective jammers and radars on both sides, the Rafale-M will be detected at 20 times lower range than the J-15 would. I would call this significant.

Finally, in absence of jamming, again assuming equal radar performance, the Rafale-M would be detected at about 0.47 the range that the J-15 would.
I kind of like shake my head on this, considering that RCS changes from all angles and wavelengths. You also have to account for transmission power, transmission wavelength, antenna gain and aperture, pattern propagation.

Spoofing doesn't require a lowering of RCS to work. Spoofing which is how really how modern ECM works, isn't trying to jam the target with overwhelming interference, but is creating a fake return with altered information that the threat radar is "fooled" to accept as valid. ECM aircraft are going to be carrying pods, and all that, are going to produce a high RCS thanks to a high amount of scattering. See Curved Surfaces. What ECM aircraft does, is emit these fake returns so the threat aircraft will accept those fake returns instead of the valid ones which the threat aircraft also receives.

From what I see with the F-18 and the Rafale, there are plenty of rounded and curved surfaces like the Su-33, and all that is going to produce a lot of scattering. On a front aspect, the F-18 and the Rafale does hide their engine intakes compared to Flanker designs, unless the Flanker's front engine blades are radar absorbent. But when it comes to other angles, all those curved lines and surfaces are going to produce all sorts of reflective highlights.

There is absolutely no way that a plane with curved surfaces and varied geometries along its body is "reduced" RCS.
 

Brumby

Major
He is referring to the J-15D which is already on testing, and there are photographs to that effect. The J-15D is the J-15 with the J-16 avionics, so yes that will have AESA and ECM. That's the J-15 Growler.
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This is precisely why I said about being pointless. A plane that is still in development and with no details is hardly a starting point to be making comparison.
The difference between an F-18, Rafale to a J-15D is not likely to be that significant in the context of a powerful AESA.
On what basis are you making such assumptions?


A more powerful AESA would easily pick off an F-18 or Rafale. Don't assume that the Chinese are noobs in ECM, anything to do with RF and spectrum techs plays very well into their technological strengths.
Unfortunately you are making plenty of assumptions - not me. A good starting point is to be more specific. What exactky does a more powerful AESA mean? According to Jane sources, ab APG-79 can detect a 1 m2 target up to 180 kms. Even with composites a J-15 in my view would be between 5 to 10 m2 RCS. Translated this mean an APG-79 can detect a J-15 from between 269 to 320 kms. Cionversely the F-18 has the lowest VLO feature of any US 4th gen fighters and rated with a 0.5 to 1 m2 RCS.
 

Tam

Major
Registered Member
This is precisely why I said about being pointless. A plane that is still in development and with no details is hardly a starting point to be making comparison.
Its a plane that's already been testing some time ago.
On what basis are you making such assumptions?
Because that is all what it takes, a received signal is a signal no matter how faint. A signal can be amplified further during digital processing.

Unfortunately you are making plenty of assumptions - not me. A good starting point is to be more specific. What exactky does a more powerful AESA mean? According to Jane sources, ab APG-79 can detect a 1 m2 target up to 180 kms. Even with composites a J-15 in my view would be between 5 to 10 m2 RCS. Translated this mean an APG-79 can detect a J-15 from between 269 to 320 kms. Cionversely the F-18 has the lowest VLO feature of any US 4th gen fighters and rated with a 0.5 to 1 m2 RCS.
Its as simple as having a higher transmit and peak power, better transmit gain and receive gain, a more focused beam and propagation pattern, as well as the radar being able to continuously track and dwell on the target.

That's also true with slotted array. A Flanker's nose has a huge antenna and can carry a large and powerful transmitter. The analogy would be the F-14's radar which is a large slotted array. Unlike the Su-33 which uses the N001 inverse cassegrain, a J-15 would be using a slotted array, a version of the Type 1474 modified for sea clutter. This is the base radar from the J-11B and this radar also has a modern digital, microprocessor controlled back end with digital signal processors, at least circa 2010 electronics technology. But this is just for the initial batch of J-15s, and the next batch of J-15s may discard this set for something more up to date.

On the figures you throw about the RCS of the J-15, I don't think its anywhere stealthy but I don't see the mathematical basis for these figures other than "hunch".

On what basis is the RCS of the F-18 is that? Is this just a frontal head on aspect on an all clean aircraft? Marketing stuff always love to talk about the optimal. Do you assume that this is what the direction of the plane will be always relative to the threat fighter? RCS will begin to differ the moment the plane will turn on its axis. Its three dimensional. You are taking an extremely simplistic approach to RCS to assume frontal aspect applies to all aspects. Here's more, an F-18 or a Rafale is like to be shorter ranged without tanks, and would likely need external tanks. That would also increase the RCS. What about weapons load? What about the rim of the radome and the rim of the cockpit? Composite doesn't reduce RCS because RF that passes through will just bounce on the plane's innards. You need metamaterials that polarize the reflection to another direction.

A better way to reduce the Flanker's frontal RCS would be the intake diverter absorb the threat radar that goes into the engine tunnel. However, that won't work when the plane is on full power, when the diverter is fully lifted.

Large vertical tailplanes like on the Rafale doesn't help at all. At least the F-18's is canted. The Su-33 also has large tailplanes.
 
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Lethe

Senior Member
Going forward, Super Hornet and J-15 will be supporting their respective VLO counterparts according to their respective strengths. They'll be playing the same roles: CAP, buddy tanking, electronic warfare, and hauling of large external payloads … but one platform has significantly greater potential than the other across all of those roles, while Super Hornet's marginally lower RCS counts for very little in any of them.
 

Max Demian

Junior Member
Registered Member
According to Jane sources, ab APG-79 can detect a 1 m2 target up to 180 kms. Even with composites a J-15 in my view would be between 5 to 10 m2 RCS. Translated this mean an APG-79 can detect a J-15 from between 269 to 320 kms. Cionversely the F-18 has the lowest VLO feature of any US 4th gen fighters and rated with a 0.5 to 1 m2 RCS.
Take these with a grain of salt (CMANO db). Frontal aspect rcs:
J-15: 7.8m2
F/A-18E: 1.4m2
Rafale-M: 0.42m2

It's well known that the Rafale has extensive LO measures implemented and it should be no surprise that it is the "stealthiest" of the three. Having said that, as Tam pointed out, aircraft RCS is highly dependent on the illuminated CS and loadout. A proper comparison (with access to classified data) would take space and effort of a master thesis.
 

Brumby

Major
Its a plane that's already been testing some time ago.
The question wasn't about how long it had been in testing. The issue is there are no known technical capabilities of it to begin making comparison and drawing conclusions based on nothing.​

Because that is all what it takes, a received signal is a signal no matter how faint. A signal can be amplified further during digital processing.
This is what you said earlier "The difference between an F-18, Rafale to a J-15D is not likely to be that significant in the context of a powerful AESA." . How is your reply above support your earlier comment?

Its as simple as having a higher transmit and peak power, better transmit gain and receive gain, a more focused beam and propagation pattern, as well as the radar being able to continuously track and dwell on the target.
I can basically apply your statement unto any AESA radar and it would be generally applicable. It doesn't explain or support your assertion that the radar associated with the J-15 would necessarily be more powerful than the one on the F-18 or Rafael.

That's also true with slotted array. A Flanker's nose has a huge antenna and can carry a large and powerful transmitter. The analogy would be the F-14's radar which is a large slotted array. Unlike the Su-33 which uses the N001 inverse cassegrain, a J-15 would be using a slotted array, a version of the Type 1474 modified for sea clutter. This is the base radar from the J-11B and this radar also has a modern digital, microprocessor controlled back end with digital signal processors, at least circa 2010 electronics technology. But this is just for the initial batch of J-15s, and the next batch of J-15s may discard this set for something more up to date.
Frankly you are saying a bunch of things that may sound relevant to you but in my opinion has no connection concerning the AESA conversation. You are positing a position that the radar on the J-15 is more powerful. Please explain how do you arrive at such a view.

On the figures you throw about the RCS of the J-15, I don't think its anywhere stealthy but I don't see the mathematical basis for these figures other than "hunch".
It is generally common knowledge that the SU-27 has a big RCS profile. The J-15 is a reverse engineered SU-33 and a navalised variant of the SU-27 and so it basically inherits the high RCS profile. What may be debated is its more precise RCS but that doesn't change the fact that it has a higher relative RCS profile than the F-18 of between 5 to 10 X by my estimate. .

On what basis is the RCS of the F-18 is that? Is this just a frontal head on aspect on an all clean aircraft? Marketing stuff always love to talk about the optimal. Do you assume that this is what the direction of the plane will be always relative to the threat fighter? RCS will begin to differ the moment the plane will turn on its axis. Its three dimensional. You are taking an extremely simplistic approach to RCS to assume frontal aspect applies to all aspects. Here's more, an F-18 or a Rafale is like to be shorter ranged without tanks, and would likely need external tanks. That would also increase the RCS. What about weapons load? What about the rim of the radome and the rim of the cockpit? Composite doesn't reduce RCS because RF that passes through will just bounce on the plane's innards. You need metamaterials that polarize the reflection to another direction.
You are just throwing a bunch of red herrings in the pathway. If you wish to take a pedantic approach on details that you think are relevant than how on earth did you arrive at your earlier conclusion when details doesn't seem to matter but just assumptions that are so elastic that one can take it to wrap around the moon. You simply wish to have the cake and eat it depending on when it suits your argument.

My point is simple. The F-18 has a relative RCS advantage and that gives it a detection advantage and a first kill.
 

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