J-20 5th Gen Fighter Thread VI

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Richard Santos

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This isn't credible. How can the test pilot test a simulator for a plane that hasn't been built? Shouldn't the simulator require real test information, when no TVC-capable J-20 prototype has flown?

Before the prototype flies, the simulator relies on calculations to reflect what the TVC hopes to achieve. After prototype has flown and been tested extensively, the simulator would also capture where calculation diverges from reality.
 

Richard Santos

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If the Chinese do put axialsymmetric TVC on the J-20, it would be interesting to see if they adapt the thrust paddle solution or a truly axial symmetric distortable nozzle.
 

Inst

Captain
Projections aren't the same as actual performance, and moreover, actual performance will involve quirks. Hence a simulator cannot accurately simulate the aerodynamics of the J-20, especially since aerodynamic flow is computationally difficult to predict.
 

Richard Santos

Captain
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Projections aren't the same as actual performance, and moreover, actual performance will involve quirks. Hence a simulator cannot accurately simulate the aerodynamics of the J-20, especially since aerodynamic flow is computationally difficult to predict.

Obviously the Chinese has a specific performance/maneuverability improvement target in mind when deciding to do the work to develop and integrate TVC. they also has to have some fairly specific ideas of what they can achieve once they’ve laid out the basic design of the flight control system and TVC. I would say Given current state of computational aerodynamics and computer simulation, their predictions at this point would likely be 90% accurate over 90% of the flight and maneuvering envelope. Yes, there could be substantial deviations from predictions at this or that edge or corner of the envelop. But the flight simulator can account for that later. Being 90% accurate 90% of the time about the eventual aircraft’s performance and maneuverability should be more than enough to begin exploring how those performances and maneuverabilities can be exploited in battle.
 

Deino

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The retired testing pilot Xu said he tested J20's all directional vector thrust, with integrated flight control. He mentioned how different it is to drive J10. I am assuming he is talking about he tested the simulator, not the actual jet. It is a sign of things to come.

There's just a similar discussion at the PDF and again the usual suspects are again hyping it as proof for their theory, the J-20 uses a TVC-engine from day one ...

Anyway he posted this sentence:

At the very end of the video:

"Our J-20, in the area of TVC and Engine and Digital Flight Control System Integration into one unit, after I have flown it, in a simulator, my experience with it , is totally different from third generation aircraft."

徐勇凌 experienced the "completed version" of J-20: Thrust Vector Control (TVC) has passed the test.
徐勇凌体验“完整版”歼20:矢量推力已过关

 

vesicles

Colonel
Projections aren't the same as actual performance, and moreover, actual performance will involve quirks. Hence a simulator cannot accurately simulate the aerodynamics of the J-20, especially since aerodynamic flow is computationally difficult to predict.

What you have in mind is a training simulator, which is mainly used to train pilots to operate an existing plane. In this case, a simulator is simply a replica of an existing equipment and is only used by operators (pilots, in this case) of the equipment.

However, during research and development, simulations are mainly used to predict various parameters that cannot be or too expensive to or too difficult to be experimentally obtained. The main purpose of simulations at this stage is NOT simply to replicate the actual performance, but to explore what we don't know and to see how much we can push the envelope without actually physically doing the testing, which can be dangerous and expensive.

In this case when the Chinese are testing thrust vectoring using their simulators, the first and the foremost thing that they must do is to establish ALL the parameters to completely replicate the fly performance of their existing J-20. They will not do anything else until they can tweak their simulators to fully replicate 100% of their existing J-20.

Once they have done that, they will move forward and add the thrust vectoring based on their goals and initial plans. They will use this new sets of thrust vectoring parameters to test their imagined J-20 on the simulator. With a highly experienced test pilot, they can get a good idea of what they need to actually physically do to modify their J-20. With the help of the test pilot, they continue to tweak their parameters until they are satisfied. Then they move on to manufacturing the actual parts based on the parameters they get from simulations. Then they move on to testing these parts on an actual J-20. Of course, the actual performance of the new J-20 won't be exactly as simulated. No one expects it to be. But that's not what the simulators are for.

No simulator is perfect. So once they actually test the new parts, they will get actual experimental data. they will then use these experimental data to further modify their mathematical models and conduct more simulations to further push the envelope. So experimental testing and simulations always go hand-in-hand.

And this kind of simulation is very different from the training simulators used by pilots.
 
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kurutoga

Junior Member
Registered Member
Keep in mind our guy Xu is retired. He is now running a TV talk show, probably on behalf of PLAAF. So what he said has high credibility but it is not anything super secrete/classified. He is like Tony Romo in the broadcast booth, predicting next play with high accuracy based on experience. Even though Xu will not send misinformation intentionally. He does not have access to the most crucial data.

Xu's entire talk runs 16:00 and can be found here:
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Inst

Captain
Is that the real reason the Chinese picked up the Su-35s? So they could use it to establish a higher-accuracy simulator craft?

That said, for all the talk of the J-20's supersonic maneuverability, once you breach the Mach barrier, you light up the IRST or the EODAS pretty well. The one question is whether the J-20 can successfully use supercruise when subsonic F-35s are sitting and watching.
 
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