J-15 carrier-borne fighter thread

[Max Demian]

Your ESM can triangulate location. There maybe like three points in the aircraft (or land units; ships use two) when the threat radar is received.

By comparing the angle and time of arrival of the signals on two of the receivers, you get the location. On the third receiver, which is set on a different height, you get altitude, to complete a three dimensional location.

Sounds good, except does such a system exist on a fighter aircraft?

Think about it. A target at 150km. On a fighter aircraft, you might separate the sensors 10m apart. Basic math shows that the angle difference the two ESMs would see is 6.666 micro rads. Can you really build an ESM with that accurate signal AOA? If yes, might as well start building F-117 style bombers again. Because who needs a radar when you have this capability.

My initial google search found a system with 2 degree accuracy, which is several orders of magnitude above what would be needed.

 

[Max Demian]

Correction for my post #2911

The angle difference is 66.666 micro rads. This is roughly equal to 14 seconds in degree units.

Since some people have started comparing against the Su-35, the RCS data I have for the Su-35S as being currently built, is 2m2 for the frontal aspect. For comparison, the F-15SA is rated at 5.8m2.

 

[Tam]

Sounds good, except does such a system exist on a fighter aircraft?

Think about it. A target at 150km. On a fighter aircraft, you might separate the sensors 10m apart. Basic math shows that the angle difference the two ESMs would see is 6.666 micro rads. Can you really build an ESM with that accurate signal AOA? If yes, might as well start building F-117 style bombers again. Because who needs a radar when you have this capability.

My initial google search found a system with 2 degree accuracy, which is several orders of magnitude above what would be needed.

What's important is that you are aware you are detected, what the threat is doing, the nature of the threat and the general direction or bearing of the threat is.

Here's an example.

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They exist with modern aircraft with varying degrees of complexity, but the most complex and capable systems are the ones in SEAD, EW and ELINT aircraft. These systems have been around for a while. Multi role fighters that are capable of using ARM missiles, like J-10s or J-11s that can use the YJ-91, or Kh-31P, for example, likely have more sophisticated ESM/RWR systems to support the use of such missiles and perform SEAD missions.

 

[Tirdent]

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.

Those figures sound superficially plausible, but only for a clean configuration. All these fighters carry their payloads externally and needless to say will be militarily useless in unarmed state, so comparing their clean RCS is futile if we want a "realistic scenario". Fully kitted out with weapons and tanks the differences will diminish considerably, and you have to account for the fact that the much larger Flanker engines can also supply far more power for jamming than its competitors. The assumption of equal radar *performance* is similarly flawed, the larger radome and higher power supply & cooling capacity give an edge to the Flanker radar if executed with equal *technology* (higher power-aperture product). You could say that SH and Rafale M attempt to use lower RCS to compensate for smaller size in favour of reduced cost for a given task.

Now, equal electronics technology (radar & ECM) is likewise an assumption only and certainly open to debate, but the take-away is that purely as an airframe platform the Flanker has at least the *potential* to more than hold its own against the SH and Rafale M. Whether the J-15(D) actually does or not (equal radar performance scenario or worse) is a question of relative avionics sophistication which - as mentioned - we can only guess.

 

[Brumby]

Wrong. Its not packaging technology that determines that. Its sheer physics.

If elements are too close to each other, something called mutual coupling happens. This means radio waves from one element interferes and transfers to the next element, affecting the next element, causing a loss of efficiency and gain. To counter the effects of mutual coupling, the elements need to be separate each other.

How far can you separate the elements? If you go too far, it will result in grating lobes. To prevent grating lobes, the accepted rule is 1/2 (or just slightly over) of the frequency band used by the radar. The shorter the frequency, the shorter the spaces, the longer the frequency, the longer the space. A radar that works on a meter wavelength means the elements must be separated by half a meter from each other. Radar working on a 10 cm wavelength, means about 5 cm element separation, just for example.

Frequency used determines the distance and separation of the elements, and also of the density of the array.



Duty cycle is determined by range of the target. Why?

Because the radar has to wait for the echo. The farther the target, the longer the radar has to wait for the echo. Only after it has received the echo can the radar transmit again. PRT is determined by range, the closer the target, the faster the pulses, the farther the object, the longer the pulses.

Mechanical fire control radars are capable of extremely fast pulse, for example, the radars used by CIWS that are used to track very close targets.



5G is the state of the art when it comes to DSP use. Guess who is ahead.



The bigger the array, the more receiving elements, the greater the measurable difference between elements from one side to the other, up and down, left and right.



The same can be said of telecom and communication technology when the AT&T monopoly was the "Huawei" of the US.



A larger plane allows for a larger radome. That's not hard to understand. Its also the same advantage the F-15 has over the F-16.



And what is an Su-35? Its still a Flanker, and a Flanker that is getting 1m2. At 2004, meaning this is older tech than an Su-35 today and the Su-35 at that time even had canards. It may even get lower if they decided to angle the radome, or do serration on the radome rim, or add grids on the cockpit glass. Further RCS reduction is possible if you attack the RCS on the AAMs and payloads.

Mate,

When you have to invoke straw man of 5G into an AESA radar discussion and to rely on questionable source that posit that the F-18 or SU-35 is more stealthy than the J-20 you are IMO entering into silly territory. Your actions basically conforms my point right from the beginning that it is pointless. I have no intention to join you in silliness.

 

[Tam]

Mate,

When you have to invoke straw man of 5G into an AESA radar discussion and to rely on questionable source that posit that the F-18 or SU-35 is more stealthy than the J-20 you are IMO entering into silly territory. Your actions basically conforms my point right from the beginning that it is pointless. I have no intention to join you in silliness.

Of course saying the J-20 is at 1m2 is pretty dubious, but other than that, the rest seemed well... The Su-35 = 1m2 figure which is clean by the way, is based on the Russians claiming they were able to achieve it. That depends whether or not you believe them, but I take it as truthful or as dubious as the French claiming the Rafale is at 1m2. In other words, they have vested interests.

 

[Deino]

Guys ... are we still J-15 related?

 

[by78]

Silhouettes...

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[Inst]

As for J-15D vs Super Hornet, you have to remember that in 4th-gen land, without internal bays, weapons tend to spike RCS and radar detection reduction is more useful toward escape. In the J-15's case, it's also supposed to have 87% more detection range on its AESA than a Super Hornet's, owing to radar aperture and technological sophistication (The J-15D / J-16 AESA is newer). Even if a J-15 loaded composite radar return was higher than the Super Hornet's under the same conditions, the J-15 could compensate by having a more powerful radar.

 

[by78]

Showing off that arm patch...

(1920 x 1080)