SAC FC-31 Stealth Fighter: News & Discussions

[gambit]

Gambit, if I am just hoping that this aircraft is superior to the F-35, then you are just hoping that it's not.

Wrong. I have always maintain the same position: Wait.

If you wish it to be superior to the F-35, it would have to be in the same category as the F-35, which is a multi-role jack-of-all-trades fighter. It would have to be V/STOL capable, which is unlikely.

The problem for you is that you will find one or two things that this new aircraft is alleged to be 'superior' to the F-35 and you will blow it all out of proportions.

My theory: Aerodynamic differences were intelligently made to improve aerodynamic performance (although some had to be made for the obvious change from 1 to 2 engines). Your theory: Differences were made to compensate for poor engine performance.

Yours is no 'theory' but merely a hope. And what I posted about the relationship between airframe and propulsion is established. You cannot dispute it.

I don't know why you posted all those diagrams again of an un-stealthy aircraft. Clearly, the J-31 does not feature a single vertical stabilizer. Stop hiding behind your diagrams. If you say I don't understand something, then explain it. If you don't then it's not that I didn't understand; it's that saying I don't understand is your last ditch effort to confuse people who aren't sure if I'm right in calling your BS.

Because they set the foundation on how to make an aircraft 'stealthy'.

Think about it for a moment. How do you know to avoid something if you do not know how the thing works/behave/looks? The fact that you said that mean my attempt to explain things to you have failed. I presented the same materials to plenty of other people in training, on aircraft and in the classroom, and they get it. Why not you?

You just showed a picture of a civilian jet engine for no reason at all.

Too bad you do not understand. And yet you dare to participate...

Yours is flawed is that YOU can make an assumption about a supposedly 'superior' airframe based upon looks alone. Mine is -- Not.

And here is why...

A turbine jet engine have four major sections:

- Compressor
- Combustion (Burner)
- Turbine
- Exhaust

Turbine Engines

The turbojet engine contains four sections: compressor, combustion chamber, turbine section, and exhaust.

This is a basic application of compressing air (Compressor), igniting the fuel-air mixture (Combustion), producing power to self-sustain the engine operation (Turbine), and exhaust for propulsion (Exhaust).

The first graphic in the above source illustrate all of the four sections in sequence of operations. Words in parentheses mine for clarity.

Refer back to that source...

The compressor types fall into three categories—centrifugal flow, axial flow, and centrifugal-axial flow. Compression of inlet air is achieved in a centrifugal flow engine by accelerating air outward perpendicular to the longitudinal axis of the machine. The axial-flow engine compresses air by a series of rotating and stationary airfoils moving the air parallel to the longitudinal axis. The centrifugalaxial flow design uses both kinds of compressors to achieve the desired compression.

The highlighted last sentence is significant: The centrifugalaxial flow design uses both kinds of compressors to achieve the desired compression.

Why is there a hybrid of the centrifugal and axial compressor types -- unless there are advantages and disadvantages for each? It is the compressor section, the physically foremost and first of four sections, that have a direct influence on airframe design.

Centrifugal compression works by 'flinging' pockets of air outward or perpendicular to the machine's longitudinal axis. We have the same thing on hot rods. The path or channel that these pockets of air travels to the combustion chamber gets increasingly narrower, creating higher pressure by the time the air pocket reached the combustion chamber. Centrifugal compressor is also known as 'radial' type compressor.

Axial compressor works by moving a continuous flow of air thru several stages of fan blades. Each fan stage is slightly different in blade airfoil aerodynamics to achieve compression thru the stages. Axial compressor can also be found in hot rods.

The differences between the two are illustrated here...

Compressors

Centrifugal compressors, which were used in the first jet engines, are still used on small turbojets and turboshaft engines and as pumps on rocket engines. Modern large turbojet and turbofan engines usually use axial compressors.

Centrifugal compression method is much more tolerant of inlet airflow distortion/disruption than axial compression method. The disadvantage is that the centrifugal compression engine will have a much larger engine front face, which in turn will determine intake sizing, which in turn will affect fuselage dimension, which in turn will affect drag, which in turn will affect maneuverability and overall performance in all flight conditions.

Axial compression method produces a superior increase and constant rate of increase of pressurized air flow, instead of air pockets, than centrifugal compression method. The axial compression engine have a much smaller engine front face, which in turn will determine a smaller intake sizing, which in turn will affect fuselage dimension, and so on...The disadvantages are the intolerance of airflow distortion/disruption which limits inlet/intake design options to those that will minimize airflow distortion/disruption, and high reliance on precision blade aerodynamics and blade material durability.

ch10-3

Especially in modern fighters that may have thrust-to-weight ratios in the order of 1, the inlet and its integration with the airframe exert a powerful influence on the overall aircraft design. The aim in engine-airframe integration is to minimize airplane drag, weight, and complexity and to maximize propulsion-system efficiency while, at the same time, ensuring that the aircraft mission requirements have not been compromised.

And that explains the highlighted sentence in the NASA source, more so for the military fighter class aircraft where we want high maneuverability and are willing to expend resources to produce high quality engine blades.

The axial turbine engine is smaller in diameter, which give us smaller inlet system regarding geometries of the cowl and boundary layer separation mechanism, which produces less drag because propulsion system induced drag is counted AGAINST installed thrust, or to put it another way, propulsion system induced drag equals to a reduction in installed thrust.

So now we have a conflict...

Uninstalled thrust is when the engine is standalone and have as much air as its diameter will allow. Installed thrust is when the engine is installed into the aircraft with an intake system which inevitably restricts air volume. Installed thrust is always less than uninstalled thrust. The greater we enlarge the intake system to give the axial turbine engine as much air volume as possible, the more complex and higher weight penalty the inlet system must be in order to slow inlet air down to .5 Mach for the engine to use, inevitably this will affect fuselage dimensions and contribute to radar cross section (RCS). If we design the intake system with drag and RCS as primary considerations, then we must reduce the intake system size, which will reduce installed thrust even more.

On the design team, the Propulsion side is going to argue for things that will get the engine to as close to theoretical output as possible. The Airframe and Radar sides, which will include aerodynamicists, are going to argue for things that will give the aircraft maneuverability and low RCS. There will be conflicting demands and with time constraints like any other business ventures, a decision has to be made that will compromise all sides.

Do you still think you can credibly divorce propulsion from airframe design? I do not use the word 'divorce' in jest. A 'marriage' is a union of two individuals, that while each can function alone, together they can accomplish much more. A 'divorce' is the separation that destroys whatever it is that they became that worked and was productive. A jet engine is useless if it not coupled to an airframe and an airframe is worthless if it cannot fly for lack of propulsion.

Ever heard of the term 'rubber engine'? No, it has nothing to do with the material called 'rubber' except in reference to elasticity.

An aircraft manufacturer is usually not an engine manufacturer. So when he design a new aircraft, given how integral is propulsion to airframe, despite your dismissal of this fact, he will contact the engine maker for the performance specs of the most up to date engine on the market. If the physical dimension of the real engine does not logically fit into his new airframe design, he will then logically scale up or down its physical dimensions to fit. But what if his inlet system reduces air flow into this hypothetical engine? Thrust is roughly proportional to intake air flow which is directly related to engine's cross sectional area. Sorry, but generally at the current technology level, reduced engine size naturally reduces thrust. Hence, the term 'rubber engine' because of its hypothetical elasticity before a physical airframe is actually made.

We even have software to help us in that task and is called a 'parametric deck'.

For examples...

Computer Deck - The GasTurb Program

The data describing the engine are created with GasTurb as an Engine Model File which is loaded during the deck initialization process. The Engine Model File contains all data necessary for doing off-design simulations, both for steady state and transient operation. Transient simulations can employ the control system as defined in the GasTurb model or run to a specified fuel flow or spool speed.

www.dtic.mil/dtic/tr/fulltext/u2/680013.pdf

The CARPET Deck is a computer program that simulates a basic parametric turbojet or turbofan. It can also be used to analyze the performance of a specific engine at discrete operating points if the total airflow is input along with the component characteristics of the engine.

Better parametric decking software can logically alter the engine's physical dimensions on the fly depending on the operator's inputs to alter things like airflow quantity or fuselage dimensions or even engine accessories relocation on the engine itself.

The airframe-propulsion integration is so important that we want to do it as early into the design phase as possible and with today's CAD/CAM technology, we can have a reasonably accurate forecast on what we must do for the new aircraft even before the first piece of metal is struck.

SAC can copy the F-22 down to the exact millimeter but if there is not a PW-F119 equivalent in China and SAC installs something inferior, then this F-22 copy will fly like sh1t. So if SAC altered this copy or 'hybridized' it from something else in any way, it does not automatically mean the alterations are for improvements as you baselessly assumed. WE DO NOT KNOW. But the relationship between propulsion and airframe design is indisputably established and not just merely another 'theory' on equal footing to your baseless assumptions.

I do not expect you to understand anything I presented above. I do not even expect you to read them. The logical arguments and their sources are more to prove to the readers why you are wrong in your convenient assumptions than to change your mind that you are wrong. In your need to save face in front of fellow Chinese on this forum, you MUST dismiss NASA and other sources whereas I am committed to the truth: That you cannot divorce propulsion from airframe design and that you cannot simply look at this new Chinese fighter and make baseless assumptions alleging superiority of its design without considering its engine sources. Yours is the typical behavior of the Chinese members here: Proven wrong but refuses to admit it out of childish pride.

Looks like this 'Gramps' has better research skills and more credibility than you, young ignorant pup.

 

[DARKY]

If the western speculation of this jet using the Russian RD-93 is correct, then what you see is probably just heat distortion since the RD-93 is not TVC.

Anyways, I just glad to see that 601 is catching up with their own stealth jet. Even if the PLA doesn't buy it, this jet may find users in South America, Africa, Central and Southeast Asia, Middle East, and who knows maybe eastern European countries. It certainly looks like a very versatile and affordable fighter.

Although its another thing that the Russians won't sell such things to Chinese... as they have been stealing most of their technologies right through.

 

[conworldus]

Although its another thing that the Russians won't sell such things to Chinese... as they have been stealing most of their technologies right through.

Don't blame China for being more advanced than your backwater hole. Keep accusing us for "stealing" is just sour grapes for your inability to learn and advance. Your mig-21++ LCA is still not in service.

For your feeble knowledge, RD-93 is the designation of RD-33s designed for JF-17. They have no vector thrust. The RD-33 does have a vector thrust nozzle but we don't have it.

 

[manqiangrexue]

No gramps, it only looks that way to you because your drugs aren't working. Lots of info about engines. Very nice. Point? None. We already established that there was a big difference between civilian engines and military, the fact that it's true doesn't pertain to any part of the conversation.

J-31 made some changes to go from original 1 big engine to 2 small engines. Of course, but how do you assume that that's were the changes stopped? Many more changes very well can be improvements.

Oh, you put that diagram up to demonstrate how to determine if an aircraft looks stealthy? I don't see anyone asking you how to determine that. And even if the conversation went there no one ever claimed that a single vertical tail was stealthy. Or maybe they did... in your mind, gramps.

Propulsion has a lot to do with how the aircraft will perform? Sure, but now is just too early to make any assumptions about what engines are gonna be like and how they will perform on the final. If we go strictly by your saying that you can't talk about air frame without talking about propulsion then nobody can say anything.

Our conversation goes in circles. I say something, you say it's wrong, then dump a bunch of random information to look like you know what you are talking about. I point out that that's a lot of true information that you googled, but it's completely devoid of meaning as it pertains to the conversation. Your response, another 2 pages of irrelevant information, this time, engine development info copied from wikipedia or something like that. Then I point out that that is also extremely pointless, and surely, your next post will copiously use google and wiki to demonstrate Viet logic again. We will not escape this cycle because you're too old to do logic, only able to post dry info.

I came to this site cus of the appearance of pictures of the J-31 and now, I'm not seeing anymore pics, but wasting time babysitting a fraudulent old man who claims to have served in the air force that destroyed his native country. All the Chinese members that have spent lots of time here already knew to ignore you because you're broken; you can't argue with someone who's mind is broken cus it's like arguing with the wall. So I'm gonna stop wasting my time here and do productive things. Good bye, up the dosage on your pills, good bye again.

 

[gambit]

No gramps, it only looks that way to you because your drugs aren't working. Lots of info about engines. Very nice. Point? None. We already established that there was a big difference between civilian engines and military, the fact that it's true doesn't pertain to any part of the conversation.

We established more than that. We established that propulsion, civilian or military, is so integrated into designing a new aircraft that its consideration made it as early as the conceptual stage. Bet you did not know that.

J-31 made some changes to go from original 1 big engine to 2 small engines. Of course, but how do you assume that that's were the changes stopped? Many more changes very well can be improvements.

I made no assumptions. So far, YOU did. I advocate: Wait.

Oh, you put that diagram up to demonstrate how to determine if an aircraft looks stealthy? I don't see anyone asking you how to determine that.

No one need to ask. Making wrong assumptions compel corrections. Like how you made your wrong assumptions.

And even if the conversation went there no one ever claimed that a single vertical tail was stealthy. Or maybe they did... in your mind, gramps.

No, many did a long time ago. Before I came on here. Now no one does. Not even the Chinese who learned so much from me. Including you.

Propulsion has a lot to do with how the aircraft will perform? Sure, but now is just too early to make any assumptions about what engines are gonna be like and how they will perform on the final. If we go strictly by your saying that you can't talk about air frame without talking about propulsion then nobody can say anything.

And that is what I have been advocating all this time. Were you asleep in class?

Our conversation goes in circles. I say something, you say it's wrong, then dump a bunch of random information to look like you know what you are talking about. I point out that that's a lot of true information that you googled, but it's completely devoid of meaning as it pertains to the conversation. Your response, another 2 pages of irrelevant information, this time, engine development info copied from wikipedia or something like that. Then I point out that that is also extremely pointless, and surely, your next post will copiously use google and wiki to demonstrate Viet logic again. We will not escape this cycle because you're too old to do logic, only able to post dry info.

But I do know what I am talking about. Unlike you Chinese boys.

I came to this site cus of the appearance of pictures of the J-31 and now, I'm not seeing anymore pics, but wasting time babysitting a fraudulent old man who claims to have served in the air force that destroyed his native country. All the Chinese members that have spent lots of time here already knew to ignore you because you're broken; you can't argue with someone who's mind is broken cus it's like arguing with the wall. So I'm gonna stop wasting my time here and do productive things. Good bye, up the dosage on your pills, good bye again.

Go to that intellectually dead playground where everyone is a member of a mutual admiration society. You will fit in there perfectly with your cluelessness and stubbornness. So far, this place proved to have many genuinely interested in the technical side of things. If you were in my class way back then, I would have sent you back to your superior after the first day.

 

[SuperFieryDragon]

J31 maybe not equip PLA . but J31 can first equip to PAF.

 

[SuperFieryDragon]

Although its another thing that the Russians won't sell such things to Chinese... as they have been stealing most of their technologies right through.

lol... look at you HAL LCA... even the america help LCA . the LCA can no completed on schedule . you think you have qualifications to ridicule our ？ we complete JF7 J8 J10 FC1 J20 J31 .and what about your HAL？just MIG21 or Su30MKI？ say our stealing . yes we stealing！ but your HAL can ？ can stealing and then manufacture a Military aircraft ？i don‘t know . but i know . we can ！and now we making progress . Start Independent research and development . we will don’t need stealing . just by virtue of its own technology manufacture a Military aircraft . J20 Is the best example .

 

[marshall]

Prior to my participation here, no one knows of the phrase 'corner reflector' and understand why it is detrimental to 'stealth'...
.
.
Prior to my participation here, no one know of something called 'EM isolation anechoic chamber' testing for low radar observable bodies...

You have quite the ego considering the plethora of military forums and Wikipedia. LOL

fighters, the aircraft MUST have twin canted vertical stabilators that does not produce the 90 deg corner reflector. Now all the talks about making every existing fighters 'stealthy' pretty much stopped.

I think stealth-IER is the keyword. Almost every fighter nowadays, whether it has single or twin vertical stabilizers, is given some design effort with LO in mind even though they are not...aka the J-10B, Eurofighter, Rafale, F-15SE and even the J-11B.

 

[gambit]

You have quite the ego considering the plethora of military forums and Wikipedia. LOL

That has nothing to do with my ego. That is the truth. Am not talking about other forums but this one.

 

[veekysingh]

lol... look at you HAL LCA... even the america help LCA . the LCA can no completed on schedule . you think you have qualifications to ridicule our ？ we complete JF7 J8 J10 FC1 J20 J31 .and what about your HAL？just MIG21 or Su30MKI？ say our stealing . yes we stealing！ but your HAL can ？ can stealing and then manufacture a Military aircraft ？i don‘t know . but i know . we can ！and now we making progress . Start Independent research and development . we will don’t need stealing . just by virtue of its own technology manufacture a Military aircraft . J20 Is the best example .

so u agree that china does steal tech from others right?

 

[rcrmj]

so u agree that china does steal tech from others right?

he is not going to waste his time on educating low IQ indians about what is reverse engineering..every high tech powers like Germany, Japan, Ex-Soviet and even U.S in its early days doing that```but again you need the basic to learn others tech``

and the said reality about India is that its economy is at primitive factor driven stage``so its probably gonna take 50 years for your primitive country to actually start to reverse engineer modern techs



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gagaga thats disturbing```you need to delete those pictures

 

[DARKY]

Don't blame China for being more advanced than your backwater hole. Keep accusing us for "stealing" is just sour grapes for your inability to learn and advance. Your mig-21++ LCA is still not in service.

For your feeble knowledge, RD-93 is the designation of RD-33s designed for JF-17. They have no vector thrust. The RD-33 does have a vector thrust nozzle but we don't have it.

Who needs to blame China for making cheap copies... infact its good for rest of the world.... there should be cheap 3rd class products as one always realizes the value of the real product.

Our Not in service Mig21++ is still better in terms of electronics when compared to your in service plane... has a better engine... composite air frame... etc... we don't teach our boys to steal.

RD-93 is for a single engine fighter... while RD-33 is for twin engine ones... but that's accepted form you.. you're a chinese after all.

lol... look at you HAL LCA... even the america help LCA . the LCA can no completed on schedule . you think you have qualifications to ridicule our ？ we complete JF7 J8 J10 FC1 J20 J31 .and what about your HAL？just MIG21 or Su30MKI？ say our stealing . yes we stealing！ but your HAL can ？ can stealing and then manufacture a Military aircraft ？i don‘t know . but i know . we can ！and now we making progress . Start Independent research and development . we will don’t need stealing . just by virtue of its own technology manufacture a Military aircraft . J20 Is the best example .

No our HAL cannot steal... since they they are not Chinese.
Why not... according to you since China has been stealing.. Its has already made cheap ripoffs.

 

[Beast]

so u agree that china does steal tech from others right?

BBC NEWS | Business | Kalashnikov upset by Indian 'copy'

he Russian company behind the world's most infamous rifle, the Kalashnikov AK-47, is up in arms over an alleged copy made by India's state weapons maker.
Representatives from Izhmash, the gun's original manufacturer, discovered what they see as an Indian rip-off of the AK-47 at an arms fair in Delhi.

But India's Ordnance Factory Board says the weapon is different enough to count as a distinct design.

AK-47 copies are produced in dozens of countries, but only a handful have formally licensed it.

The row blew up, Izhmash representatives told Agence France Presse news agency, when the man who invented the AK-47 in World War II visited OFB's pavilion at the arms fair and saw what he thought was a copy of his brainchild.

"I don't see any permission being given to India to manufacture the rifle" and sell it for export, said Izhmash's Andrei Vishnyakov.

Russia is India's largest supplier of weapons - although not of AK-47s.

'Threat'

The new weapon has yet to appear on OFB's website, which advertises products ranging from pistols to main battle tanks.

Still, OFB staff were keen to deny the accusation.

"The cocking mechanism is different, the lever has been changed and the barrel is chrome-plated," OFB gun designer Mohammad Ali told AFP.

For general manager MK Garg, Izhmash's complaint rests on a false premise.

"The Russian Kalashnikov was made in 1947 and no patent in the armament industry is valid beyond 30 years," he said.

"It seems they are threatened by our product."

Who owns what?

Izhmash has run into copyright problems before.

Russian companies spent two years disputing who controlled rights to the AK-47 before Izhmash finally won sole control in 2002.

But the millions of copies sold in arms bazaars over the world - and appearing on at least one national flag (Mozambique's) as well - have yet to produce much in the way of royalties.

If we agree! India is equally guilty. But the worst is India has learn nothing out of it. And is the ultimate loser. Look at your pathetic Kaveri Engine. Never even make it prototype and has killed by DRDO.
While our WS-10A engine has power many of our jets to skies... Look carefully, those engine install are not AL-31F but our WS-10A engine.. THis is just few of our indigenuous project. Our Type 052D and J-31 are also going hot.

 

[marshall]

It is no surprising, supercomputer aid design of 5th gen stealth fighter. Super computer also helps in making nuclear weapon. Surprising, nulcear weapon and stealth fighter are the 2 thing gaining headline in the last few years about PLA military capabilites.

Accurate data is needed to simulate your models. This is why nuclear weapons testing and wind tunnels are absolutely essential. China is far behind in these aspects despite it's impressive strides.

As for the technology, I bet you do not know. China now possess the most powerful hydraulic press in the world. Hydraulic press is critical in making huge aircraft component and parts for aeronautic engine. It is the continue dumping of R&D fund by the state that China able to achieve such feat.

You're mistaken concerning aircraft engine parts. These sorts of hydraulic presses are used to forge large single piece items in shipbuilding, nuclear plant construction, certain commercial aircraft wing parts, etc. Basically where welding is not desired. China's biggest weakness when it comes to aeronautic engines has always been in material science. However, this is turning around because China has lead materials science research for years now which has allowed critical bottlenecks to be overcome.

Su-27 design is great , no doubt about that. A great product of Soviet Era times..
P-51 Mustang is also great for its time... Shall we move on??

They have the SU-30s, SU-34s, SU-35s, PAK-FA, etc, etc. You know, they can say the same about the J-8F and J-10A which entered service in the last 10 years.

 

[gambit]

China's biggest weakness when it comes to aeronautic engines has always been in material science.

Technically speaking, a turbine jet engine is an internal combustion engine. But the difference between this internal combustion engine and the one in our cars is that for the automobile version, metals are subjected to only brief periods of peak operating temperatures and far lower temperatures than the turbine version. That is why we can get away of using ordinary forged steel. For the turbine jet engine, the core blades are under constant peak or very near peak operating temperature throughout flight that could last for one hr or several (intercontinental) hrs.