JF-17 Thunder Multirole Fighter [Thread 4]

[gambit]

In your opinion what is the least achievable RCS for a fighter like JFT. Just a wise guess would help.

Do you mean the lowest RCS average?

An aircraft's shape is very much like the simple plate. View edge on, the plate have the lowest RCS. View on either side, the plate will have the highest RCS values.

The aircraft departs from this simple shape by its accessories, such as engines, cockpit and so on. Each accessory contribute in varying degrees to each aspect angle: front, top, bottom, rear and the sides. For example, to the front aspect, the cockpit as a contributor is higher than when view from the rear aspect and none at all when view from the bottom (underside) aspect.

So when we are dealing with as complex a body like an aircraft, the goal is to achieve the highest measure of RCS control PER aspect at the absolute views, meaning directly front, directly top, directly bottom, directly side, and directly rear. Then we begin to increase the deflection angles for each aspect, meaning instead of direct front, add a few degrees off-angle and see how the signals deflects then interact with other structures nearby. We do this over and over again until we can no longer influence how the signals behave in terms of deflections and interactions.

If the customer deems the results unacceptable, we starts all over with a new design. Not a new shape because of the current technology, the overall shape is still the plate. It is the dirigible that have a different shape -- cylinder. With 'stealth' the overall shape is a blend of the plate and the ogive. The F-117 is the exception because it was pretty much an 'exploratory' venture into this realm with its triangular angled faceting method. Some have called the F-117's shaping closer to the pyramid than the plate.

Note I say: 'highest RCS control'. Not 'highest RCS'. The greater the ability to influence the behaviors of deflections, the higher the measure of control, which equals to the lowering (hopefully continually) of the final RCS value.

I know people would like to see simple answers but the unfortunate truth is that there are very few in this area.

If possible for you to answer, may I request to know what makes Russian PAK-FA a stealth if they are not using serpentine or any similar intake system? Does that means PAK-FA will have an extremely high RCS at some angle?

The first VISUAL cue for anyone to conveniently call any of the current design a '5th gen' or 'stealth' or 'stealthy' is the internalization of weapons, or as I call them 'doo-dads'.

In fact, the words 'internalization' or 'internalize' are neither precise nor accurate. But they are reasonable enough that even radar engineers uses them.

Missiles and bombs are complex bodies. They are complex because of the blending of many simple shapes into one complex body. We have the cone for the nose, the cylinder for the fuselage, and the plate for the fins. The more these simple shapes are exposed to radar bombardment, the greater the detectability of these doo-dads, which in turns contribute to the overall detectability of the parent aircraft.

The word 'enclosure' is the more precise and accurate descriptor for the denial of radar detection of these doo-dads. If we enclose them in a pod and hangs the pod off the wing like how some wanted for the 'stealthier' F-18, we removed a lot of deflectors but also created a new one and it is larger to boot. With appropriate shaping measures, the weapons pod will have a lower radar obserability factor than a cluster of weapons, like this EM mess...

But the pod itself still constitute a doo-dad.

So we enclose the weapons into the aircraft's body itself to remove any additional EM radiators completely. Hence the words 'internalization' and 'internalize', which is referencing the aircraft itself. Whether we enclose the doo-dads into a pod or the fuselage, we incur a cost, technical and financial, on how to dispense them -- quickly and safely. But that is another issue.

The second VISUAL cue that anyone can conveniently call a current design as '5th gen' or 'stealth' is the twin canted vertical stabs. The B-2 have none. Am confident that a lot of members here know what that mean for RCS so I will not go into the technical details.

After these two visual cues, anything said about the 'stealthiness' of the aircraft is pure speculation and I have no problems applying that to the American F-22, F-35 and the B-2 as well and no one on this forum is a greater proponent of 'stealth' than I.

The reason that it is problematic and pure speculation is that we, meaning the aviation world at large, have no accepted official standard for what is radar 'stealth'. We have the clean F-16 to serve as an unofficial standard but that is the extent of it and any country that flies the F-16 can conduct its own tests. The public does not know what the F-117 look like on the EM front and it is retired.

So in my opinion, we need two items:

- A reasonable standard for radar 'stealth' that is beyond what the F-16's data can tell us.

- The complete isolated anechoic EM testing data for the target aircraft.

We can dismiss the second item immediately (for now) because no one is going to release that data. So without the second item, the first is irrelevant.

 

[Viper0011.]

Thanks for such a useful post.

In your opinion what is the least achievable RCS for a fighter like JFT. Just a wise guess would help.

If possible for you to answer, may I request to know what makes Russian PAK-FA a stealth if they are not using serpentine or any similar intake system? Does that means PAK-FA will have an extremely high RCS at some angle?

There is NO such thing as an entirely Stealth jet that can carry weapons and fly. Even the makers of F-22 can't claim that. It is 'stealthy' bot not Stealth. Features and attributes are two different things.
The Stealth as we know it isn't JUST the shape, the energy deflection, the angular shapes or the RAM quoting. It is A LOT more than that. It includes a range of other things, including signal diversion, deflection, jamming, mis-guidance / decoy frequencies and the RCS control through internal weapons bay, flight envelop. etc, etc. Every time a plane takes a steep turn or goes subsonic to supersonic its body releases energy due to gravity and drag....BAM...you are visible.
So its a packaged deal. In simple words, minimizing, managing and controlling your visibility to other radars up until a certain point is considered stealth. F-22 is visible on radar. But when that happens, its too late. The operator of that radar may not exist anymore to take advantage of that or before you can press a button, the radar itself might get hit. That's the idea. Competitive advantage. When the enemy seems you, it is TOO late.
If you put a plane under IR imaging, you'll notice that the biggest rcs can be found around the fuselage, wings and intakes to engines. That's where the energy is. If you put these in an internal bay of some sort, that has rcs reduction measure around it like RAM, you can hide the visibility or minimize it exposure.
RCS control also includes Internal electronics, delayed heat release after firing a missile (away from the plane), special equipment to hide fan blade energy from openly getting release and then cooling the exhaust flame (and avoiding after burner) aka, the super cruise, etc. All are features to control the visibility and reduce the radar cross section / rcs etc.
Combine that with sophisticated technology and electronic spectrum control techniques, you've got a plane that will not be visible from a certain distance or will confuse the radar due to smaller rcs (as its now hiding all other aspects from ALL angles that can give out a blip on the screen due to energy release). At some point, the plane will get closer to radar at a range where radar's energy will be significant to detect the minimal release of energy coming from the jet and then the plane might become visible or if it used its weapons, it'll create a blip right away.

But like Gambit said, no one really knows the magic number as to when that happens and what energy levels can be deflected or cheated against.

From the design, PakFa and Chinese J 20 have stealthy features as they employ rcs reduction techniques. By looking at their engine outlets and intakes, the nature of exhaust is such that it'll generate energy. They'll need to replace those before going operational. Similarly, the intakes will need some work inside them too. The PakFa isn't very angular. It's really a SU-30 converted with RAM quoting and smooth edges in certain parts and angular edges in certain parts. So again, it'll have a lower rcs and hard to detect but not Stealth unless the Russians put more work into it.

I think the closest to having real 'Stealth' planes are the unmanned ones that don't carry payload but remain entirely invisible for intelligence purposes (USN, USAF uses them). These planes don't make steep turns, causing no drag and gravity related burn on the surface, etc so very hard to detect. But that's my opinion.

 

[abdulbarijan]

Interesting... So basically the goal is to control the RCS of the biggest reflecting body and start this whole process till it reaches its limit....

But speaking in layman's terms even though amongst the biggest reflective bodies would be the external (missiles & Drop tanks), so is it right to assume that two jets (take Gripen and JFT for example) would have the same FRONTAL RCS if they were loaded with identical configuration ....

I mean to say that even though there are measures in Gripen (RAM / radar blockers) wont it have lesser AVERAGE Frontal RCS even though its configuration (take 4 missiles and 3 droptanks for example) would be the same as JFT (DSI /limited RAM).... If not, than these little thingies such as curved intakes and Y-ducts should have some RCS control effect on the overall Frontal RCS even though there are more reflective surfaces present...

 

[gambit]

Interesting... So basically the goal is to control the RCS of the biggest reflecting body and start this whole process till it reaches its limit....

Until you can no longer reduce its RCS contributorship, which may very well be your first attempt, or the second, or the tenth.

But speaking in layman's terms even though amongst the biggest reflective bodies would be the external (missiles & Drop tanks), so is it right to assume that two jets (take Gripen and JFT for example) would have the same FRONTAL RCS if they were loaded with identical configuration ....

This is tricky and I do not want to jump to conclusions without hard data but I would guess both would fall within a percentage range of each other.

I mean to say that even though there are measures in Gripen (RAM / radar blockers) wont it have lesser AVERAGE Frontal RCS even though its configuration (take 4 missiles and 3 droptanks for example) would be the same as JFT (DSI /limited RAM).... If not, than these little thingies such as curved intakes and Y-ducts should have some RCS control effect on the overall Frontal RCS even though there are more reflective surfaces present...

Most fighters carry two external fuel tanks and two wing tip missiles. Other hard points including centerline may vary. With or without them the best way to say one frontal RCS is better (lower) than the other is still measurement. Sorry to disappoint any expectations you may have based upon any preferences you may harbor but measurement is still the final arbiter.

 

[abdulbarijan]

Until you can no longer reduce its RCS contributorship, which may very well be your first attempt, or the second, or the tenth.


This is tricky and I do not want to jump to conclusions without hard data but I would guess both would fall within a percentage range of each other.


Most fighters carry two external fuel tanks and two wing tip missiles. Other hard points including centerline may vary. With or without them the best way to say one frontal RCS is better (lower) than the other is still measurement. Sorry to disappoint any expectations you may have based upon any preferences you may harbor but measurement is still the final arbiter.

The reason I asked these questions was a thread by storm force in which he considered the frontal RCS's of different BVR capable platforms in South Asia and then speculated an increased RCS with air-air load on board after which he compared the ranges at which they would start detecting each other with the consideration of the formula

((RCS1/RCS2)^0.25 * radar range) (RCS2=5m2 and radar ranges were for 5m2)

Now connecting here with what the likes of an insider think tank Nabil-05 reported sometime ago that JF-17 has the lowest RCS in PAF's fleet (including the blk-52 at 1.2m2) and the fact that it has been reported that JF-17 does have RAM usage, Y-ducts, curved intakes, limited composite usage and small size did point to such a possibility....

When I spoke of RCS reduction measures I never spoke of F-22/Pak-FA/J-20 class reductions/control or even SU-35 BM/EF-2000/Rafale class ... My entire focus was Gripen~F-16 C class (0.05-1.2m2)... now even though these are simply speculations but unlike lucky ones like you we dont have hard data to play with

Secondly what do you say about the aerodynamics configuration of JF-17 with LERX and a Mirage 2000 class wing-loading, not necessarily a T/W ratio to boost about but above 0.96 for sure with speculations about increased thrust for better ratio (and the fact that it was reported by a chinese expert that it was able to defeat F-16 A's Blk-15 in WVR ...As i remember there were 5 different videos with one of em talking about the close combat b/w the falcon and thunder..

 

[SQ8]

The reason I asked these questions was a thread by storm force in which he considered the frontal RCS's of different BVR capable platforms in South Asia and then speculated an increased RCS with air-air load on board after which he compared the ranges at which they would start detecting each other with the consideration of the formula

((RCS1/RCS2)^0.25 * radar range) (RCS2=5m2 and radar ranges were for 5m2)

Now connecting here with what the likes of an insider think tank Nabil-05 reported sometime ago that JF-17 has the lowest RCS in PAF's fleet (including the blk-52 at 1.2m2) and the fact that it has been reported that JF-17 does have RAM usage, Y-ducts, curved intakes, limited composite usage and small size did point to such a possibility....

When I spoke of RCS reduction measures I never spoke of F-22/Pak-FA/J-20 class reductions/control or even SU-35 BM/EF-2000/Rafale class ... My entire focus was Gripen~F-16 C class (0.05-1.2m2)... now even though these are simply speculations but unlike lucky ones like you we dont have hard data to play with

Secondly what do you say about the aerodynamics configuration of JF-17 with LERX and a Mirage 2000 class wing-loading, not necessarily a T/W ratio to boost about but above 0.96 for sure with speculations about increased thrust for better ratio (and the fact that it was reported by a chinese expert that it was able to defeat F-16 A's Blk-15 in WVR ...As i remember there were 5 different videos with one of em talking about the close combat b/w the falcon and thunder..

Incorrect, the JF-17 does not use RAM at any section.

A clean Jf-17 turns better than a clean F-16 (both at best corner airspeed for altitudes).
However the F-16 has a clear advantage in the vertical due to a more powerful powerplant.

 

[abdulbarijan]

Incorrect, the JF-17 does not use RAM at any section.

A clean Jf-17 turns better than a clean F-16 (both at best corner airspeed for altitudes).
However the F-16 has a clear advantage in the vertical due to a more powerful powerplant.

For RAM issue

From Najam Khan's book ...

 

[Manticore]

did you go through the info pool?
this post
http://www.defence.pk/forums/jf-17-thunder/71435-jf-17-thunder-information-pool-24.html#post2908592

 

[SQ8]

For RAM issue

From Najam Khan's book ...

Najam's book is a wonderful piece of knowledge. But I disagree on the use of RAM based on authoritative sources.
It was considered, never applied in production...YET!.

 

[Viper0011.]

The reason I asked these questions was a thread by storm force in which he considered the frontal RCS's of different BVR capable platforms in South Asia and then speculated an increased RCS with air-air load on board after which he compared the ranges at which they would start detecting each other with the consideration of the formula

((RCS1/RCS2)^0.25 * radar range) (RCS2=5m2 and radar ranges were for 5m2)

The formula above may be a text book version of basic rcs calculation. This isn't how the real life works. People thought G = 9.8 ms2. Sit in a jet doing mach 2 or in a space shuttle and the G changes. Similarly, a plane is like a plate and can be detected from angles during movement. Hypothetical ranges may give a basic understanding, but they are never accurate. Plus it depends on many things I've outlined above.

Remember, stealthy planes are against physics. Similarly, planes with unstable aerodynamic capability are too. If you stick to the laws of physics, a lot of the things the 4 gen jets can do, may not be considered possible in the early years of aviation. Technology and computing has made that happen.

Secondly what do you say about the aerodynamics configuration of JF-17 with LERX and a Mirage 2000 class wing-loading, not necessarily a T/W ratio to boost about but above 0.96 for sure with speculations about increased thrust for better ratio (and the fact that it was reported by a chinese expert that it was able to defeat F-16 A's Blk-15 in WVR ...As i remember there were 5 different videos with one of em talking about the close combat b/w the falcon and thunder..

Again, if the stealthiness isn't in the design (like F-22, J20, etc), then you are trying to do basic RCS reduction which will be limited. Thrust and RCS control are two different things. If you review the design of F-22 and J 20, you'll notice that these planes aren't just jets. These are powerful electronic warehouses storing plenty of electronics that otherwise may not be used in normal 4.5 gen planes. To me, the better designs (personal opinion) are F-22, J-20, etc. T-50 is a modified SU-30. It's designed from where it stands right now, doesn't look as stealthy. While if you review F-22, JSF and J-20...you can see the dimensions and know that these designs are stealth optimized from the getgo.

Can you post the link to those five videos where Thunder simulated wins against the F-16?

 

[IceCold]

So even if we did manage to reduce RCS of JF-17 what exactly did we gain? What i understood(please correct me on this) from Gambit post was that the seeking radar will have other areas which are higher contributor to the radar it self.
So my question is all this hype about RCS control in 4.5th generation fighters (not 5th generation) is mere nonsense and a marketing strategy to keep them in business?
Because if the jet is not a stealth fighter from the get go like the F22, technically you cant lower the RCS from one angle like DSI or RAM because there are other areas that will contribute equally more.

 

[ababeel22]

if they can use ram ttype paint on babur y cant they use it on jf17? now dont tell me that stealthly feature of babur is due to terrain hugging ability only, i have clearly heard that it uses special paint also?

 

[abdulbarijan]

if they can use ram ttype paint on babur y cant they use it on jf17? now dont tell me that stealthly feature of babur is due to terrain hugging ability only, i have clearly heard that it uses special paint also?

Well its always a matter of "IFs" and "buts" when it comes down to the capability of Pakistani forces because for obvious reasons we need to keep others guessing...however Oscar bro himself is on record telling us about different RAM coating tests in the 1990's ...

Did they make it to JF-17 (Najam bhais book says so), and other think tanks like Nabil and others also have their sources pointing out that the RCS of JFT is the lowest in PAF's service (F-16C class to be safe for now)

 

[gambit]

The reason I asked these questions was a thread by storm force in which he considered the frontal RCS's of different BVR capable platforms in South Asia and then speculated an increased RCS with air-air load on board after which he compared the ranges at which they would start detecting each other with the consideration of the formula

((RCS1/RCS2)^0.25 * radar range) (RCS2=5m2 and radar ranges were for 5m2)

Now connecting here with what the likes of an insider think tank Nabil-05 reported sometime ago that JF-17 has the lowest RCS in PAF's fleet (including the blk-52 at 1.2m2) and the fact that it has been reported that JF-17 does have RAM usage, Y-ducts, curved intakes, limited composite usage and small size did point to such a possibility....

My problem with that is tactical. It seems to speculate that both aircrafts will be in a 'head-on' engagement in order to speculate who is going to detect who first based upon speculative RCS values.

If it assumes that both fighters will have statistically insignificant differences in radar range capability, there is nothing wrong with the initial assumption provided that no fighters will have radar warning receivers. The fighter with the lower RCS will detect his opponent first. But if we inject RWR into the engagement, then even though the fighter with the larger RCS is detected first, he will be warned of that vulnerability. In this scenario, the first one to detect his opponent must make a quick decision to shoot first as well and if this is done at maximum range, the odds of losing the kill increases.

This is why having a lower RCS is not always a decisive advantage unless accompanied by tactics and weapons to deliberately exploit that technical advantage. For the F-22, that is with radar in Low Probability of Interception (LPI) mode, meaning just as the F-22 is difficult to detect, its radar transmissions are difficult to detect by warning receivers as well.

Now...If in a tail chase situation, then having a lower RCS is not any advantage at all because the opposing fighter is not transmitting from his rear quarters.

We can argue that the best exploit for low RCS is to be silent, as in no transmissions of any kind, from radar to communication. But then you need someone to guide you to the fight close enough where you can use your radar to engage.

When I spoke of RCS reduction measures I never spoke of F-22/Pak-FA/J-20 class reductions/control or even SU-35 BM/EF-2000/Rafale class ... My entire focus was Gripen~F-16 C class (0.05-1.2m2)... now even though these are simply speculations but unlike lucky ones like you we dont have hard data to play with

Sorry, buddy. But I do not have any hard data and even if I do, I would not reveal it here. Am sure you understand.

Secondly what do you say about the aerodynamics configuration of JF-17 with LERX and a Mirage 2000 class wing-loading, not necessarily a T/W ratio to boost about but above 0.96 for sure with speculations about increased thrust for better ratio (and the fact that it was reported by a chinese expert that it was able to defeat F-16 A's Blk-15 in WVR ...As i remember there were 5 different videos with one of em talking about the close combat b/w the falcon and thunder..

Increased T/W ratio is never a bad thing.

If we are talking about a WVR engagement, then we are talking about a lot maneuvers, which lead to what everyone want: the Minimum Radius Turn.

To lower the minimum radius turn, the wing loading must be lowered. The air must either be as dense as possible or as forceful on the surfaces as possible which demands a higher T/W ratio. Then bank angle increase to to provide lift during the turn.

Then we have the Maximum Rate Turn which demands the same conditions as the minimum radius turn.

The common denominators are thrust and bank angle. We can give both fighters the the same bank rate. The only variable left is thrust which is the T/W ratio.

 

[Tempest II]

I have extracted these from a report by a student who was at Kamra on placement in 2010. $1.4m for the radar and $3m total for avionics.

The report is here: http://www.scribd.com/doc/61306465/Visit-Report