J-20... The New Generation Fighter III

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Engineer

Engineer

Major
Air Force Brat said:
To answer your last question first----there is really no way that TVC will increase thrust, it merely deflects exhaust gases to enhance aircraft control----the engineer is correct when he asserts that there is a minimal reduction in thrust as the exhaust gases lose energy when they encounter the deflected nozzle. He is also correct when he points out that TVC increases maintenance and complexity- while it enhances control authority of the aircraft.
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That is correct. Thrust of an engine is determined by the internal air flow condition and the turbine temperature. What MiG-29 talked about is related to the function of a variable convergent-divergent nozzle, which he misrepresents as the function of a TVN. However, all a variable convergent-divergent nozzle does is optimize the engine's performance at different flight conditions. The nozzle does not create what's isn't there the first place -- thrust.
 
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NikeX

Banned Idiot
Engineer said:
That is correct. Thrust of an engine is determined by the internal air flow condition and the turbine temperature. What MiG-29 talked about is related to the function of a variable convergent-divergent nozzle, which he misrepresents as the function of a TVN. However, all a variable convergent-divergent nozzle does is optimize the engine's performance at different flight conditions. The nozzle does not create what's isn't there the first place -- thrust.
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I think you misunderstand how certain thrust vectoring systems work. The pictures below show that there is more to Thrust vectoring than "internal air flow and turbine temperature" In these pictures pay close attention to the nozzle shape and direction. The variable convergent-divergent nozzle is vectoring the thrust

Hope this helps

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NikeX

Banned Idiot
Engineer said:
Wrong. F-22 is the benchmark for the simple reason that it is the first 5-th generation aircraft and the only such aircraft in operation.

The J-20's designers anticipated potential problems in the development of F-119 class engine, thus chose to compensate with very sophisticated and advanced aerodynamics. J-20 features the most numerous vortex generators on any aircraft seen so far, with a total of four pairs from the chine, strake, canard, and LERX. Such design intends to provide large amount of lift especially at high AoA situation. This lift along with thrust are what enable an aircraft to turn and out maneuver another fighter, not TVC.

If WS-15 delivers the requirements, then the combination of advanced aerodynamics and powerful engines will enable J-20 to out maneuver the F-22. If not, the aerodynamics will enable the J-20 to handle itself visa-versus an F-22.
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All this is nice talk but until the J-20 flies with its advanced engines all it is, is talk and conjecture.
 
Engineer

Engineer

Major
NikeX said:
I think you misunderstand how certain thrust vectoring systems work. The pictures below show that there is more to Thrust vectoring than "internal air flow and turbine temperature" In these pictures pay close attention to the nozzle shape and direction. The variable convergent-divergent nozzle is vectoring the thrust

Hope this helps
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I have already replied to this. See reply #3912 or reply #9 in the TVC thread.

NikeX said:
All this is nice talk but until the J-20 flies with its advanced engines all it is, is talk and conjecture.
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On the contrary, the advanced aerodynamics on the J-20 is very real. The vortex generators I have mentioned and the resulting vortexes can clearly be identified in pictures of the J-20. Dr. Song's paper also talks extensively about how these features are employed to enhance the lift thus maneuverability of the aircraft. What is a conjecture is the opinion that J-20 is not maneuverable.
 
N

NikeX

Banned Idiot
=Engineer
On the contrary, the advanced aerodynamics on the J-20 is very real. The vortex generators I have mentioned and the resulting vortexes can clearly be identified in pictures of the J-20. Dr. Song's paper also talks extensively about how these features are employed to enhance the lift thus maneuverability of the aircraft. What is a conjecture is the opinion that J-20 is not maneuverable.
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But until you begin to explore the fight envelope at supersonic speeds how can anyone say how advanced the aerodynamics really are? Maneuvering at supersonic speeds during supercruise is where a 5th gen fighter makes its living and as we all realize the J-20 is waiting on the engines to test out its ability to supercruise.

This is what I meant by conjecture. They need to open up J-20 and let her go. That is what I am interested in seeing.
 
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latenlazy

Brigadier
NikeX said:
All this is nice talk but until the J-20 flies with its advanced engines all it is, is talk and conjecture.
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Sure, but your skepticism is also conjecture. You insist that an engine in development is not proof enough that thing will happen. We trust that they will because they haven't failed to Everything hinges on circumstantial evidence. If there is no burden of proof which will satisfy that skepticism, then there really is no point discussing and debating the matter.

NikeX said:
But until you begin to explore the fight envelope at supersonic speeds how can anyone say how advanced the aerodynamics really are? Maneuvering at supersonic speeds during supercruise is where a 5th gen fighter makes its living and as we all realize the J-20 is waiting on the engines to test out its ability to supercruise.

This is what I meant by conjecture. They need to open up J-20 and let her go. That is what I am interested in seeing.
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Given that they did a paper which describes the exact aerodynamic arrangement we see on the J-20, one can surmise that their intention is to verify their own small scale tests. Since building a full sized prototype is about the last step to verifying all the aerodynamic elements of a design, it would be reasonable to think they are testing this prototype with at least some confidence that the air frame performs the way they intend it to.

In addition to that, we also know that the PLA isn't so headstrong that it will sabotage its own military capabilities for the sake of indigenous development. If they can't get their own engine program working, I'm pretty confident they will just buy Russian.
 
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Engineer

Engineer

Major
NikeX said:
But until you begin to explore the fight envelope at supersonic speeds how can anyone say how advanced the aerodynamics really are? Maneuvering at supersonic speeds during supercruise is where a 5th gen fighter makes its living and as we all realize the J-20 is waiting on the engines to test out its ability to supercruise.

This is what I meant by conjecture. They need to open up J-20 and let her go. That is what I am interested in seeing.
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In that case, I think you misunderstood the meaning of conjecture. Conjecture refers to opinion that has no basis in facts. J-20's aerodynamics are very much real, described by Dr. Song himself in his paper on J-20's preliminary configuration. Furthermore, aerodynamics pretty much have to be proven before the prototype is built, and is done through a combination of computer fluid dynamics and extensive wind tunnel testings. Aerodynamics are not conjectures. This procedure is the same as on any other aircraft.

It is true that J-20 is waiting on WS-15. The difference that will make is whether J-20 will only be able to hold itself visa-versus a F-22, or to enjoy advantages over the F-22.
 
N

NikeX

Banned Idiot
latenlazy said:
Sure, but your skepticism is also conjecture. You insist that an engine in development is not proof enough that thing will happen. We trust that they will because they haven't failed to Everything hinges on circumstantial evidence. If there is no burden of proof which will satisfy that skepticism, then there really is no point discussing and debating the matter.
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Right now there are several factors that are hampering the development of advanced engines for Chinese fighters. The time window needed to overcome these challenges are unknown for Chinese aerospace. The time discussed for these advanced engines is in the early 2020's. To be realistic that sounds about right


Given that they did a paper which describes the exact aerodynamic arrangement we see on the J-20, one can surmise that their intention is to verify their own small scale tests. Since building a full sized prototype is about the last step to verifying all the aerodynamic elements of a design, it would be reasonable to think they are testing this prototype with at least some confidence that the air frame performs the way they intend it to.
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Paper airplanes are just that...paper airplanes. Get back to me when Chinese aerospace takes the next step in the development of the J-20

There are no magic steps or shortcuts you can take to bring J-20 to fruition any faster than the rest of the world's aerospace companies needed to create their advanced 5th gen fighters

In addition to that, we also know that the PLA isn't so headstrong that it will sabotage its own military capabilities for the sake of indigenous development. If they can't get their own engine program working, I'm pretty confident they will just buy Russian.
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That remains to be seen. These are exciting times
 
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