Russian media:J20's stealth capability is far better than F-35 and pakfa

[Skull and Bones]

I believe that is not for detection and firing solution but for IFF.

What, L-Band or IRST? I don't think IRST can identify friend or foe.

And L-Band is for low RCS platform in the airspace. And it's true L-Band can't provide enough resolution for identification and target acquisition.

 

[A1Kaid]

Your assumption of me believing the things you have mentioned can't be found in my replies as i have never compared the F22 with J20 nor have i ever made any comparison between US and Chinese space technology. I don't think you have that much to attribute on both forums other than calling people goons whenever it suits you.

It's not specifically you but others whose lunacy you came here to defend. Why don't you stay out of it? Are you their boyfriend or lawyer you need to defend them? You probably know very well the extraordinary claims made about Chinese space capability and Chinese technological capability relative to US, its claimed China is equal or superior in x,y,z. But if you are going to defend them then I can presume you ideologically agree with them, or your just trying to help your fellow countrymen out of sake of shared nationality irrespective whether they be right or wrong.

 

[Agnostic_Indian]

What, L-Band or IRST? I don't think IRST can identify friend or foe.

And L-Band is for low RCS platform in the airspace. And it's true L-Band can't provide enough resolution for identification and target acquisition.

L band, I heard it's L Land transponders for IFF.

 

[Skull and Bones]

L band, I heard it's L Land transponders for IFF.

Possible, seems like i'll have to dig a bit more into it.

 

[Skull and Bones]

L band, I heard it's L Land transponders for IFF.

Here's few things i found:

The PAK-FA therefore has true 360 degree coverage. The PAK-FA has L-Band radars mounted in the wing leading edges. These have both passive and active emitting roles and are key to ‘seeing’ stealth aircraft such as the F-22.

The F-22’s stealth is generally optimized against X-band radars as that is what fighters generally use – L-Band is a much longer wavelength and can more easily detect stealth aircraft but is also less accurate -hence X-band radars are still used for routine intercept and virtually all fighters use X-Band.

Sukhoi PAK-FA T-50

According the anti-F-35 Karlo Kopp's site

Search, track and missile midcourse guidance against low signature aircraft.
Identification Friend Foe / Secondary Surveillance Radar.
Passive angle tracking and geolocation of JTIDS/MIDS/Link-16 emitters at long ranges.
Passive angle tracking and geolocation of L-band AEW&C/AWACS and surface based search radars at long ranges.
Passive angle tracking and geolocation of hostile (i.e. Western) IFF and SSR transponders at long ranges.
High power active jamming of JTIDS/MIDS/Link-16 emitters.
High power active jamming of satellite navigation receivers over large areas.
High power active jamming of L-band AEW&C/AWACS and surface based search radars at long ranges.
High power active jamming of guided munition command datalinks over large areas.

Assessing the Tikhomirov NIIP L-Band Active Electronically Steered Array

 

[gambit]

With the advent of L-Band radar, all shaped stealth like F-22, F-35, PAK-FA or J-20 is rendered ineffective, though L-Band doesn't provide high resolution to guide a BVR missile, but hen it can detect a stealth fighter at a distance of more than 200 km, it can have better situational awareness.

Sorry, but no.

L band - Wikipedia, the free encyclopedia

The X and L bands are ghz and they are actually not that far apart from each other on the scale. Remember that one factor of RCS creation is freq employed, so since no one really know how 'deep' are the F-22's and F-35's RCS into the clutter rejection threshold, there is no credible argument, let alone technical evidence, to say that the small L-band arrays mounted on wing leading edges, will do any good.

Bottom line is this: If you want to raise that body completely out of the clutter rejection threshold, either you lower that threshold, or use high metric freq.

 

[A1Kaid]

Sorry, but no.

L band - Wikipedia, the free encyclopedia

The X and L bands are ghz and they are actually not that far apart from each other on the scale. Remember that one factor of RCS creation is freq employed, so since no one really know how 'deep' are the F-22's and F-35's RCS into the clutter rejection threshold, there is no credible argument, let alone technical evidence, to say that the small L-band arrays mounted on wing leading edges, will do any good.

Bottom line is this: If you want to raise that body completely out of the clutter rejection threshold, either you lower that threshold, or use high metric freq.

What do you think about the J-20's cockpit and canopy design? Do you think it's similar to the F-22's if so in what way?

What do you think led the Chinese aeronautical engineers to choose this cockpit and canopy design for J-20?

 

[Agnostic_Indian]

Here's few things i found:



Sukhoi PAK-FA T-50

According the anti-F-35 Karlo Kopp's site



Assessing the Tikhomirov NIIP L-Band Active Electronically Steered Array

http://www.scribd.com/mobile/doc/78980598?width=320

check this out (p.28)and tell me what you think it is, I am not sure whether it's only iff or multi function aesa.

I can see @gambit there, what do you think sir ?

 

[gambit]

Do you think the J-20 is a genuine fifth generation aircraft or is it more like a pseudo-fifth generation? Considering what has been said about its avionics and other aspects.

The problem here is that when it comes to 'stealth', people still based their opinions upon appearances, and unfortunately, it is a reasonable, even if incomplete, assumption.

The J-20 is a highly refined MIG 1.44. Or what the 1.44 would have been if the Soviets continued that program. The Chinese took that basic planform and incorporated known RCS control methods onto it. Not an easy task because outer re-shaping of any existing planform inevitably affect the original aerodynamics. What they did was very much an engineering leap worthy of any high caliber aviation power aspirant.

Look at it this way: The B-2 is a highly refined Northrop YB-49 (1947). Or what the -49 would have been had Northrop continued that program.

My opinion -- STRICTLY from a sensor specialist perspective -- is that the J-20 approaches the so called '5th gen' category. May be even a little bit better than the F-15 Silent Eagle variant.

But there are many unknown regarding avionics, for example...

Flying the F/A-18F Super Hornet

2.2 The Virtual Speedbrake
The next handling demonstration involved involved the speedbrake and some high alpha low speed handling, an area in which many fighters experience problems in maintaining direction and avoiding a departure into uncontrolled flight.

The first demonstration involved the virtual speedbrake effectiveness and handling in this configuration. The F/A-18A-D, like the F-15 series, employs an upper fuselage hydraulically deployed speedbrake. The Super Hornet has no such device, yet achieves the same effect through what can only be described as digital magic. The speedbrake function is produced by a balanced deployment of opposing flight control surfaces, generating drag without loss of flight control authority or change in aircraft pitch attitude.

Dave demonstrated the speedbrake function, and I was asked to observe over the shoulder and in the mirrors the raised ailerons, lowered trailing flaps, raised spoilers and splayed out rudders. Deceleration is smooth and there is no observable pitch change.

At Mach 0.63 Dave invited me to fly another 360 aileron roll, to observe that the aircraft retains considerable control authority despite the fact that the rudders are splayed out, and the ailerons, spoilers and flaps are generating balanced opposing pitching moments. I applied roughly 1/2 stick input and the aircraft very cleanly rolled through 360 degrees at about 90 degrees/sec roll rate. I commented on the lower roll rate and Dave observed that we were significantly slower, he then proceeded to demonstrate the roll again with a full stick input, producing around 180 degrees/sec with a slight overshoot on recovery. The aircraft feels very stable throughout the manoeuvre and there is no observable change in control forces or control input response by the FCS.

The -18SH removed the speedbrake completely and introduced much more complex flight control laws to create the same effect via tightly coordinated deflections and movements of ALL flight control surfaces. And if the pilot want to maneuver while in speedbrake mode, those laws will allow additional maneuvers without affecting controllability and stability throughout the maneuvers.

This is very much '5th gen' flight control laws and we saw samples of that in F-22 airshow demos. These laws have push/pull relationships with planform and engines. Sometimes the aerodynamicists will create a planform that will allow greater latitude (push) on what the flight control engineers can do. Sometimes it is from Aerodynamics and Propulsion. Sometimes Avionics will demand (pull) that Aerodynamics and Propulsion change and/or create something new.

We do not know anything else about the J-20 regarding these other expected '5th gen' functions. Nothing about sensor integration. And the engine is still below par. So for now, I cannot categorize the J-20 as a 'legit 5th gen' fighter.

 

[PITA]

Gambit,

Any idea on how far you think China is from what you would consider a straight up 5th gen fighter? Is there anyway you gauge where China is from the technological advances of today compared to years past? Where does China stand in technological capability compared to other countries?

Thx

If my questions don't make sense it's because, I'll be the first to admit, that my knowledge in this area is limited but if there is any insight you can provide, it'd be much appreciated.

 

[gambit]

What do you think about the J-20's cockpit and canopy design? Do you think it's similar to the F-22's if so in what way?

What do you think led the Chinese aeronautical engineers to choose this cockpit and canopy design for J-20?

The Chinese did not clone, but pretty much copied all the major functions, and incorporated into the J-20 as part of the overall RCS control methods. We do not have precise measurements of canopy rise, arcs, density, materials, transparency (clarity) measurements, etc. But let us be real here...

Technically speaking, the F-16 have a true 'bubble canopy', while all others, including the F-15 and F-22, have hybrids of being 'frameless' and 'bubble'. I got that straight from a General Dynamics tech rep back in 1987. A true bubble canopy is more difficult to manufacture than hybrids.

A major copy from the F-22 is the forward fuselage shape...

The F-22's forward fuselage is shaped that way for precise combination of aerodynamics and RCS control demands.

A cone under radar bombardment exhibit unique RCS signatures that rises in intensity from the broad quarter towards the tip. Here is where the 10-lambda (wavelength) rule applies.

If the diameter is larger than 10 wavelengths, then there will be no creeping wave effect. The creeping wave behavior is when the surface wave travels completely around the diameter (sphere or cylinder) and return to source direction on the other side. If the diameter is less than 10 wavelengths, then the creeping wave behavior will occur.

A cone is slightly different in that the diameter decreases in a gradual manner, which increases RCS intensity.

The F-15's forward fuselage section, which includes the radome, is quite cylindrical. While the fuselage itself is greater than 10-lambda and is immune from the creeping wave behavior, the radome itself is not. The F-15's and F-16's radomes will exhibit those unique RCS signatures common to the cone. The SR-71's forward fuselage section is quite angular, which results in direct reflections more than surface waves.

Put them together and we have the F-22's forward fuselage shape the way it is. The ridges on both sides are surface discontinuities or radiators designed to 'leap' off any surface wave behaviors into free space, and this will be on the opposite or 'shadow' side of the seeking radar's position.

Basically, any radar angle approach on the forward fuselage section will deny the seeking radar that unique conical RCS signature common to previous generations. There is NOTHING on the F-22 and F-35 that is omitted from precise analyses regarding RCS contributorship and the Chinese know this.

 

[gambit]

PAK T-50 5G Russian Plane

check this out (p.28)and tell me what you think it is, I am not sure whether it's only iff or multi function aesa.

I can see @gambit there, what do you think sir ?

Not much to tell here. But let me put it this way...If you have an AESA array, you are halfway towards a true real time multi-function radar system. Your only limitations are software and how large is that array. You must have an active, as in AESA, and not passive, as in PESA.

In the above simple example, which one is a physical antenna that is divided into 9 logical arrays for nine different tasks -- SIMULTANEOUSLY ?

That division is called 'sub-array partitioning' and choreography...

Digital Array Radar Panel Development | EEWeb

...simultaneous transmit and receive operation through subarray partitioning...

Your software flexibility is restrained by the physical quantity and layout of the individual transmit/receive (T/R) elements.

So if we take a look at how a beam is formed by the antenna's physical layout...

Which is that for a highly linear physical layout, the beam will be fan shaped and 90 deg from antenna orientation. So for a wing leading edge config, you will have a vertically oriented fan beam that sweeps horizontally (side-side).

There is no advantage in having an AESA array in this highly restrained configuration. PESA will do just fine. An AESA system can perform tactical queries (IFF) as well as volume search -- SIMULTANEOUSLY. But if you have only a linear physical layout that is dictated by location on the aircraft, a PESA system can switched between IFF and volume search rapidly enough.

 

[gambit]

Gambit,

Any idea on how far you think China is from what you would consider a straight up 5th gen fighter? Is there anyway you gauge where China is from the technological advances of today compared to years past? Where does China stand in technological capability compared to other countries?

Thx

If my questions don't make sense it's because, I'll be the first to admit, that my knowledge in this area is limited but if there is any insight you can provide, it'd be much appreciated.

Not very far, to me.

However, China is still at least one generation behind US. The Russkies will not like it, but I will say that Chinese aviation, for all practical purposes, is statistically little different from Russia. The Russians have been largely evolutionary in their designs and the PAK is no different. In making the J-20, the Chinese effectively said to the Russians 'S T F U, we do not need U any more.'

I would say that the next Chinese 'stealth' fighter must have technological parity to US in terms of avionics and aerodynamics, like how the the F-16 was the leap and became the foundation for inherent instability and fly-by-wire for later fighters, else the Russians will get ahead.

 

[Hyperion]

I feel as if they would catch up with the US within 15 - 20 years.

Not very far, to me.

However, China is still at least one generation behind US. The Russkies will not like it, but I will say that Chinese aviation, for all practical purposes, is statistically little different from Russia. The Russians have been largely evolutionary in their designs and the PAK is no different. In making the J-20, the Chinese effectively said to the Russians 'S T F U, we do not need U any more.'

I would say that the next Chinese 'stealth' fighter must have technological parity to US in terms of avionics and aerodynamics, like how the the F-16 was the leap and became the foundation for inherent instability and fly-by-wire for later fighters, else the Russians will get ahead.

 

[antonius123]

The problem here is that when it comes to 'stealth', people still based their opinions upon appearances, and unfortunately, it is a reasonable, even if incomplete, assumption.

The J-20 is a highly refined MIG 1.44. Or what the 1.44 would have been if the Soviets continued that program. The Chinese took that basic planform and incorporated known RCS control methods onto it. Not an easy task because outer re-shaping of any existing planform inevitably affect the original aerodynamics. What they did was very much an engineering leap worthy of any high caliber aviation power aspirant.

Look at it this way: The B-2 is a highly refined Northrop YB-49 (1947). Or what the -49 would have been had Northrop continued that program.

This is also assumption? or any evidence?

Why didn't the chinese took the basic planform from Eurofighter or Rafale or J-10?

Am I wrong if I assume that they took the basic planform from J-10 or the predecessor?

My opinion -- STRICTLY from a sensor specialist perspective -- is that the J-20 approaches the so called '5th gen' category. May be even a little bit better than the F-15 Silent Eagle variant.

According to your opinion, how is the PAKFA compared with the F-15 SE in term of stealth?

Thanks.