Chengdu J-20 5th Generation Aircraft News & Discussions

[SQ8]

Prototype vs Operational AC.
A better look would be comparing the J-20 with the YF-22.
its hard to find a similar shot for the YF-22..
but I do see some irregularities in this image as well as pointed out in the image above.

 

[Martian2]

Regarding DrSomnath's J-20 and F-22 comparison, it is true that the J-20 Mighty Dragon has a few minor faults. China has six more years to fix the minor faults before the 2018 IOC. Also, the key question is what is the increase in detectability from the J-20's minor faults?

Let's say the collective increase from minor design faults is 10% greater detection than the F-22. This means the F-22 can detect the J-20 from 22 miles away and the J-20 cannot detect the F-22 until it is 20 miles away.

Let's say the J-20 and F-22 are supercruising towards each other at Mach 1.5. Their collective speed is Mach 3 in closing the distance between them. At sea level, Mach one is 761 mph. Mach 3 means a speed of 2,283 mph in closing the distance between them.

The F-22 advantage is a greater detection distance of 2 miles.

Math:

2 miles / 2,283 mph = 0.000876 hours

0.000876 hours * 60 minutes per hour = 0.05265 minutes

0.05265 minutes * 60 seconds per minute = 3.15 seconds

Conclusion:

Due to the minor flaws on the J-20 Mighty Dragon, we can expect the F-22 pilot to have a tiny edge of approximately 3.15 seconds in earlier detection against a J-20. The F-22 will have the opportunity to fire its air-to-air missile against the J-20 about 3 seconds earlier than the J-20's launch of air-to-air missiles against the F-22.

In my judgment, a 3 second advantage when both planes are roughly twenty miles away is operationally worthless. You can change the assumptions within reason, but I doubt the F-22 pilot will have more than a 5 second or so advantage. I don't think it makes any difference in combat, but you would have to decide for yourself.

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Here are some new high-resolution pictures of J-20 Mighty Dragon from angles that you may not have yet seen:

[Note: Thank you to Greyboy2 for the pictures.]

 

[DrSomnath999]

Prototype vs Operational AC.
A better look would be comparing the J-20 with the YF-22.
its hard to find a similar shot for the YF-22..
but I do see some irregularities in this image as well as pointed out in the image above.

well why should we compare a test protype with j20 ,it has no relevance .as Yf22 had many design changes which evolved into
F22 Am i right ???

 

[gambit]

Let's say the collective increase from minor design faults is 10% greater detection than the F-22. This means the F-22 can detect the J-20 from 22 miles away and the J-20 cannot detect the F-22 until it is 20 miles away.

From what foundation do you based this '10%' ?

 

[Peaceful Civilian]

Please...Stop...The F-35 is not any type of 'degradation' of the F-22. The F-35 is a totally different aircraft for a different mission type. Why not say the F-35 is a 'degraded' version of the B-2 since both aircrafts drop bombs?

Dude about F35, 1.6 Mach speed is nothing for modern aircraft.
Conventional takeoff , short take off and vertical-landing is understandable. But 1.6 Mach speed is nothing for this Role.
This aircraft is Mix of 5th generation and 4th generation technology.
Again i say, 1.6 Mach speed.

 

[Martian2]

From what foundation do you based this '10%' ?

Not major flaws, only minor flaws.

Major flaws are 10%+. Minor flaws are 2 to 3% each. 10% is my best ballpark guess to illustrate a point.

A little gap between the canard and fuselage will not yield a 10%+ penalty. It's only a LITTLE gap.

 

[gambit]

Not major flaws, only minor flaws.

Major flaws are 10%+. Minor flaws are 2 to 3% each. 10% is my best ballpark guess to illustrate a point.

In other words, what you did would IMMEDIATELY disqualify you from any peer review process -- a baseless guess.

 

[DrSomnath999]

Regarding DrSomnath's J-20 and F-22 comparison, it is true that the J-20 Mighty Dragon has a few minor faults. China has six more years to fix the minor faults before the 2018 IOC. Also, the key question is what is the increase in detectability from the J-20's minor faults.

Let's say the collective increase from minor design faults is 10% greater detection than the F-22. This means the F-22 can detect the J-20 from 22 miles away and the J-20 cannot detect the F-22 until it is 20 miles away.

Let's say the J-20 and F-22 are supercruising towards each other at Mach 1.5. Their collective speed is Mach 3 in closing the distance between them. At sea level, Mach one is 761 mph. Mach 3 means a speed of 2,283 mph in closing the distance between them.

The F-22 advantage is a greater detection distance of 2 miles.

Math:

2 miles / 2,283 mph = 0.000876 hours

0.000876 hours * 60 minutes per hour = 0.05265 minutes

0.05265 minutes * 60 seconds per minute = 3.15 seconds

Conclusion:

Due to the minor flaws on the J-20 Mighty Dragon, we can expect the F-22 pilot to have a tiny edge of approximately 3.15 seconds in earlier detection against a J-20. The F-22 will have the opportunity to fire its air-to-air missile against the J-20 about 3 seconds earlier than the J-20's launch of air-to-air missiles against the F-22.

In my judgment, a 3 second advantage when both planes are roughly twenty miles away is operationally worthless. You can change the assumptions within reason, but I doubt the F-22 pilot will have more than a 5 second or so advantage. I don't think it makes any difference in combat, but you would have to decide for yourself.

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here F22 rules baby because of this
ALR 94 passive detection capabilty

The AN/ALR-94 is a passive receiver system capable of detecting the radar signals in the environment. Composed of more than 30 antennae smoothly blended into the wings and fuselage, it is described by the former head of the F-22 program at Lockheed Martin Tom Burbage as "the most technically complex piece of equipment on the aircraft." With greater range (250+ nmi) than the radar, it enables the F-22 to limit its own radar emission which might otherwise compromise its stealth. As the target approaches, AN/ALR-94 can cue the AN/APG-77 radar to keep track of its motion with a narrow beam, which can be as focused as 2° by 2° in azimuth and elevation.The AN/APG-77 AESA radar, designed for air-superiority and strike operations, features a low-observable, active-aperture, electronically-scanned array that can track multiple targets in all kinds of weather. The AN/APG-77 changes frequencies more than 1,000 times per second to reduce the chance of being intercepted. The radar can also focus its emissions to overload enemy sensors, giving the aircraft an electronic-attack capability.A pair on patrol.The radar’s information is processed by two Raytheon Common Integrated Processor (CIP)s. Each CIP operates at 10.5 billion instructions per second and has 300 megabytes of memory. Information can be gathered from the radar and other onboard and offboard systems, filtered by the CIP, and offered in easy-to-digest ways on several cockpit displays, enabling the pilot to remain on top of complicated situations. The Raptor’s software is composed of over 1.7 million lines of code, most of which concerns processing data from the radar. The radar has an estimated range of 125-150 miles, though planned upgrades will allow a range of 250 miles or more in narrow beams
airlines: The AN/ALR-94 is a passive receiver system capable of detecting the radar signals in the environment.

so even if both are stealthy if one on one combat happens between the two F22 can detect J20 passively 220 miles away becoz
f22 passive detection capabilty(ESM) provided J20 turns on it aesa radar for detection of F22


remember everyone apart from ALR 94 ,only rafale's spectra has this capabilty (CHEERS)

 

[Martian2]

In other words, what you did would IMMEDIATELY disqualify from any peer review process -- a baseless guess.

You can talk trash all you want. You still believe that cylinders are stealthy.

I let the readers decide. My best estimate is that a F-22 pilot will have a 3 to 5 second advantage over a J-20 pilot in launching its missile first.

You can go ahead and claim the J-20's little canard gap yields a 100% stealth penalty if you want. I don't really care about your anti-China views.

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Dr. Somnath, I've already posted a ground-based EADS 3D radar and made the calculation that a F-22 is detectable only 20 miles away. If you want to claim a J-20 stealth fighter (widely acknowledged as a close peer of the F-22) is detectable over 200 miles away, I couldn't care less. You can make all the silly claims you want. My goal is to make the most reasonable estimates and let the readers decide.

 

[DrSomnath999]

Dr. Somnath, I've already posted a ground-based EADS 3D radar and made the calculation that a F-22 is detectable only 20 miles away. If you want to claim a J-20 stealth fighter (widely acknowledged as a close peer of the F-22) is detectable over 200 miles away, I couldn't care less. You can make all the silly claims you want. My goal is to make the most reasonable estimates and let the readers decide.

plz read the bold part for that condition
so even if both are stealthy if one on one combat happens between the two F22 can detect J20 passively 220 miles away becoz
f22 passive detection capabilty(ESM) provided J20 turns on it aesa radar for detection of F22

 

[gambit]

You can talk trash all you want. You still believe that cylinders are stealthy.

Nowhere did I say so. You have a reading comprehension problem.

I let the readers decide.

You mean at this point ALL the Chinese boys will start 'thanking' you for those 'useful' posts? Even though they have been found to be dubious at best? Yup, to you, that is about the extent of the word 'readers'.

 

[Martian2]

From my February 5, 2011 post:

Ground-based radar can detect F-22/J-20 at 13.5 km, Rafale at 135 km, T-50 at 178 km

The EADS mobile ground-based "3D Radar System DR 174" can detect a F-22/J-20 at approximately 13.5 km, French Rafale at 135 km, and a Russian T-50 at 178 km.

The DR 174 only has 24 kilowatts of peak power and it operates in the L-band. Obviously, a permanent ground-based radar or AWACS will have more peak power, more radar bands (e.g. X-band, S-band, L-band, etc.), more powerful computers, better discriminating software, better-trained personnel, etc.

My calculations:

According to GlobalSecurity (see one of my earlier posts), the French Rafale has a RCS of 1 m2. We know that "the detection range [of the DR 174] against tactical aircrafts ("Swerling 1”- targets) with a radar cross section (RCS) of 1 m² is 135 km at a probability of detection of 90%."

We know that the "reflected power density at the radar receiver" is proportional to the fourth-root of the distance from the emitting radar or RCS (see Radar cross-section - Wikipedia, the free encyclopedia).

According to GlobalSecurity, the F-22 (and my estimate of J-20's front-profile) has a RCS of 0.0001. The F-22's/J-20's RCS is 10,000 times smaller than the French Rafale. The fourth-root of 10,000 is 10. Therefore, the detection range of the F-22/J-20 in comparison to the French Rafale is 13.5 km (e.g. 135 km/factor of 10 from much smaller RCS = 13.5 km).

Since the Russian T-50, with exposed engine compressor blades, has a RCS greater than the French Rafale's 1 m2, I have estimated the Russian T-50 RCS to be about 3 m2. The fourth-root of 3 is 1.316. Therefore, the detection range of the Russian T-50 in comparison to the French Rafale is 178 km (e.g. 135 km * factor of 1.316 from larger RCS = 178 km).

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Radar Basics

3D Radar System DR 174

Bild 1: © EADS

The 3D radar system DR 174 is a highly mobile short/mid range surveillance radar operating in the L-Band. The radar system can be used as coastal radar for sea and air surveillance or as „gap fillers” for areas longer radars do not cover. The system can be integrated into existing defence networks, anti-aircraft (AA) weapon systems and other networks. It can also serve as a „stand alone” control center due the fully integrated state of the art working positions. A wide range of ECCM features and excellent clutter suppression ensure the detection of small targets even in a very hostile environment.

This 3D radar system operates in L-Band using a stacked beam active planar antenna. It features up to 8 elevation beams on receive. The system is designed in fully solid state technology.

The DR 174 Doppler radar features

* High unambiguous radial velocity due to appropriate pulse repetition frequency (PRF) stagger
* Frequency diversity
* High doppler resolution
* Detecting of tangential flying targets due to self learning ground clutter map

The detection range against tactical aircrafts („Swerling 1”- targets) with a radar cross section (RCS) of 1 m² is 135 km at a probability of detection of 90%. The detection range against tactical ballistic missiles with a radar cross section (RCS) of 0.1 m² is 75 km at the same conditions.

Waveform selection

The following statements highlight the capabilities of the DR 174 waveform selection:

* Different waveforms for various radar modes
* Non-linear frequency modulation
* Burst-to-Burst frequency change
* Burst-to-Burst pulse repetition frequency change
* Dual pulse for near range covering
* High range resolution waveforms

ECCM features

The electronic counter counter measures used by the DR 174 are:

* Frequency change from Burst-to-Burst
* Moving target detection processing with Doppler selective constant false alarm rate
* Low antenna sidelobes in azimuth and elevation
* Sidelobe blanking (SLB) (optional)
* Large receive dynamic range
* Selectable beam-processing
* Automatic jamming avoidance circuit (AJAC)

Clutter rejection

Excellent clutter suppression and detection of small targets in any type of clutter (ground- and rainclutter, seaclutter, chaff and angles) by:

* Very stable solid state transmitter
* Frequency agile synthesizer
* Moving target detection Doppler processing in frequency domain (sub clutter visibility)
* Ordered statistic constant false alarm rate in time domain
* High resolution clutter map
* Decreasing the size of resolution cell of radar (pulse compression with time sidelobes <45 dB)
* Matched detection threshold for each Doppler channel
* Tilting the antenna to higher elevation angles

ARM protection

Protecting against Anti Radar Missiles is supported by:

* LPT due to low transmitter peak power
* Transmitter silent sectors
* Very low antenna sidelobes
* Inherent system protection due to radar operating frequency band (L-Band)

The system consists of four major components the sensor (antenna group consisting of primary ans secondary radar), the Signal Processing (SiP) shelter, the Operations and Missions Control (OMC) shelter and the generator for reliable power supply in mobile deployment.

Also available is the DR 184, the long range version (400 km) of DR 174.

Figure 2: The concept of the DR 174 sensor

 

[gambit]

From my February 5, 2011 post:

Ground-based radar can detect F-22/J-20 at 13.5 km, Rafale at 135 km, T-50 at 178 km

The EADS mobile ground-based "3D Radar System DR 174" can detect a F-22/J-20 at approximately 13.5 km, French Rafale at 135 km, and a Russian T-50 at 178 km.

The DR 174 only has 24 kilowatts of peak power and it operates in the L-band. Obviously, a permanent ground-based radar or AWACS will have more peak power, more radar bands (e.g. X-band, S-band, L-band, etc.), more powerful computers, better discriminating software, better-trained personnel, etc.

My calculations:

I doubt that you understand even 1/10th was what said in these sources. If anyone who is truly guilty of copy/paste things in trying to put on a facade of knowledge, it is YOU.

 

[DrSomnath999]

hey martian u didnt understand the meaning & advantage of passive detection .PLZ read this article u would learn something
about passive detection

THE NEXT GENERATION
The fourth Lockheed Martin F-22 Raptor, aircraft 4004. Is due to make its first flight from Marietta. GA, in late July. As the first F-22 to carry offensive avionics. Its task is to demonstrate that a stealthy aircraft can be a fighter. Under a deal struck with Congress last year, the F-22 has to prove this key technology by the end of this year if the next ten aircraft are to be authorized.

The F-22 represents a radical departure from the traditional approach to EW. Passive systems, once considered to be defensive in nature, are now critical to detecting, tracking and even attacking the target. The active radar, while still a primary sensor, is used sparingly for specific tasks. Active jamming in the traditional sense has disappeared. The F-22 approach is echoed to some extent in most of today's advanced fighter programs, including the Dassault Rafale, Eurofighter typhoon and Saab JAS Gripen. It is also fundamental to the future of the Joint Strike Fighter (JSF).

The F-22's EW philosophy is rooted in some of the earliest work on stealth. As the US Air Force (USAF) defined requirements and operational doctrine for the F-117 stealth strike aircraft and B-2 bomber, in 1980-81, A "Red Team" headed by Dr. Paul Kaminski was charged with looking for weaknesses and vulnerabilities in stealth technology. One of the Red Team's Most important conclusions was that a stealth aircraft could not survive by low radar cross-section (RCS) alone, but by stealth and tactics.

In the case of the F-117 the Red Team's recommendation resulted in the development of one of the first automated mission-planning systems, but this left the aircraft dependent on a pre-programmed flight plan. The B-2 was designed to feature a sophisticated defensive management system (DMS) which would allow the crew to respond to threat radars not anticipated by the mission plan. The initial DMS was abandoned in the late 1980s. Its successor is the APR-50, developed by IBM Federal Systems (later acquired by Loral and now part of Lockheed Martin).
The USAF's Advanced Tactical Fighter project, which led to the F-22, presented greater challenges. In the air-to-air regime, the primary threats are airborne and move rapidly, making identification, location and tracking more complex. The F-22's sustained speed also shortens engagement timelines by as much as 40 percent.
At the same time, the fighter's classic tool for situational awareness -- a powerful search radar -- can render its stealth characteristics moot. Low-probability-of-intercept (LPI) techniques are not very compatible with continuous searches over a large volume. The fighter's stealth is also of little use if it has to close to visual range in order to identify its targets. Passive search and track and non-cooperative target recognition (NCTR) are not luxuries for a stealthy air-superiority fighter.
The solution to this problem on the F-22 is sensor fusion. The principal sensors are the Northrop Grumman APG-77 radar and the Sanders ALR-94 passive receiver system. The fighter also has two datalink systems: one using the standard VHF/UHF radio frequencies and the other, the intraflight datalink (IFDL), a low-power LPI link which connects two or more F-22s at close range. The sensors are apertures connected to the fighter's Common Integrated Processor (CIP) banks in the forward fuselage.

The data from the APG-77, ALR-94 and the datalinks are correlated according to their azimuth, elevation and range. Data is combined into a track file, and the final target picture is obtained by choosing the read-out from the most accurate sensor. For example, the passive system may provide the best azimuth data, while the radar produces the most accurate range.

CIP software controls the APG-77 according to emission-control principles. The radar's signals are managed in intensity, duration and space to maintain the pilot's situational awareness while minimizing the chance that its signals will be intercepted. More distant targets get less radar attention; as they get closer to the F-22, they will be identified and prioritized; and when they are close enough to be engaged or avoided, they are continuously tracked.

Sensor fusion and emission control are closely linked. The more the datalinks and ALR-94 can be used to build and update the tactical picture, the less the system needs to use the radar. The IFDL provides another layer of protection against tracking, because any one F-22 in a flight can provide radar data to the others.
The APG-77 and ALR-94 are unique, high-performance sensors. The APG-77 has an active, electronically scanned array (AESA) comprising some 1,200 transmitter and receiver modules. One vital difference between an AESA and any other radar that has a single transmitter (including a passive electronically steered array) is that the AESA is capable of operating as several separate radars simultaneously. An AESA can change its beamform very readily, and its receiver segments can operate in a passive or receive-only mode. Unlike a mechanical antenna, too, its revisit rates are not constrained by the antenna drive, and it can concurrently revisit different points within its field of regard at different rates. The F-22 has space, weight and cooling provision for auxiliary side arrays on either side of the nose. If installed, these would provide radar coverage over almost 270[degrees]. The ALR-94, meanwhile, is the most effective passive system ever installed on a fighter. Tom Burbage, former head of the F-22 program at Lockheed Martin, has described it as "the most technically complex piece of equipment on the aircraft."

The F-22 has been described as an antenna farm. Indeed, it would resemble a signals-intelligence (SIGINT) platform were it not for the fact that the 30-plus antennas are all smoothly blended into the wings and fuselage. The ALR-94 provides 360[degrees] coverage in all bands, with both azimuth and elevation coverage in the forward sector.

A target which is using radar to search for the F-22 or other friendly aircraft can be detected, tracked and identified by the ALR-94 long before its radar can see anything, at ranges of 250 nm or more. As the range closes, but still above 100 nm, the APG-77 can be cued by the ALR-94 to search for other aircraft in the hostile flight. The system uses techniques such as cued tracking: since the track file, updated by the ALR-94, can tell the radar where to look, it can detect and track the target with a very narrow beam, measuring as little as 2[degrees] by 2[degrees] in azimuth and elevation. One engineer calls it "a laser beam, not a searchlight. We want to use our resources on the high-value targets. We don't track targets that are too far away to be a threat."

The system also automatically increases revisit rates according to the threat posed by the targets. Another technique is "closed-loop tracking," in which the radar constantly adjusts the power and number of pulses to retain a lock on its target while using the smallest possible amount of energy.

High-priority emitters -- such as fighter aircraft at close range -- can be tracked in real time by the ALR-94. In this mode, called narrowband interleaved search and track (NBILST), the radar is used only to provide precise range and velocity data to set up a missile attack. If a hostile aircraft is injudicious in its use of radar, the ALR-94 may provide nearly all the information necessary to launch an AIM-120 AMRAAM air-to-air missile (AAM) and guide it to impact, making it virtually an anti-radiation AAM.

Of course, there are some targets that do not emit signals. "We prefer it that way, because he's dumb," remarked one Boeing engineer. In this case, the F-22 can use its LPI features to track the target -- which is not a threat unless another radar is tracking the F-22 and datalinking information to the "quiet" aircraft -- and can, if necessary, identify it.

NCTR is a highly classified area. One of the few known techniques is jet-engine modulation, which involves analyzing the raw radar return for the characteristic beat produced by a combination of the radar-pulse frequency and the rotating blades of the engine. This technique is already used on operational radars (including the APG-70 in the F-15) but is vulnerable to countermeasures and dependent on target aspect.

Other NCTR techniques involve very precise range measurements. If the target's orientation is known, the distribution of the signature over very small range bins can yield a range profile which is characteristic of a certain aircraft type. It is possible that the F-22, which has a great deal of onboard processing power -- as well as a flexible, frequency-agile radar -- is designed to use an NCTR technique of this kind.

Unlike the Eurofighter Typhoon , the F-22 does not have an electro-optical (EO) system for target identification. F-22 program managers have said consistently that they believe that the F-22 pilot will be able to identify any target -- emitting or not -- beyond visual range (BVR). "We are confident that we can demonstrate to our leadership that we know what's out there, and that we will operate with rules of engagement that reflect that fact," USAF program manager Gen Mike Mushala remarked at a conference in 1997.

The ALR-94 drives the F-22's defensive displays. The system determines the bearing, range and type of the threat, and then computes the distance at which the enemy radar can detect the F-22. The pilot is the decision-maker and is provided with timely, graphic information to guide defensive maneuvers. On the main defense display, usually shown on the left-hand screen in the cockpit, threat surface-to-air missile (SAM) and airborne early warning (AEW) radars are surrounded by circles that show their computed effective range. On the right-hand attack display, fighter radars are shown as blue beams extending towards the F-22's
position.
http://www.f-16.net/f-16_forum_viewtopic-t-9268-start-0.html

 

[Martian2]

From fifty miles away, the subtended angle of the LITTLE canard gap approaches zero. That's why the stealth penalty should be only about 2% from about 20 miles away.

The subtending of an angle is easy to understand. The Moon subtends a distance of roughly your thumb, when held at arms distance. The Sun is a gazillion times larger than the Moon and yet, it appears the same size in the sky. The subtended angle of an object is a function of size AND distance.

To use the principle of subtending angle, let's say the J-20 canard gap is a few inches if you stand close to it. Let's just say 3 inches. 3 inches from fifty miles away subtends a fraction of a fraction of a fraction of a degree. It's microscopic.

I stand by my estimate that a little canard gap will yield a stealth penalty in the 2 to 3% range. The angle it subtends is simply too small. The extremely small subtended angle can be expressed as a percentage of the entire subtended angle of the J-20 aircraft to yield the conclusion of a 2% effect.

I just don't feel like spending 30 minutes to calculate a precise number. It wouldn't change the minds of the rabid anti-China crowd.

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Dr. Somnath, you are mixing apples and oranges in this discussion. Why don't you do a reverse post and claim the J-20 can passively detect a F-22 from over 200 miles away? Of course, a modern radar can passively detect an emitting radar from 200 miles away. Everyone knows that. What is your point?

I'm trying to make the point that there are indeed minor flaws present on the J-20 Mighty Dragon. There is indeed a slight advantage for a F-22 pilot. I have shown that the advantage is roughly 3 to 5 seconds from twenty miles away, which I believe is operationally useless. Readers are free to make their own independent judgment.