J-20... The New Generation Fighter III
- Thread starter siegecrossbow
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Pull up Dr Song's paper again (I hate digging for it). The quote I was thinking off was something to the effect of the J-20 being able to recover from stall without TVC or something to the effect. With regards to showing expectation for a design incorporating TVC it was a semantic interpretation.
"Post stall maneuvers require the aircraft to have good controllability and stability. After the plane enters the post stall region, however, the decrease in stability and control efficiency of conventional rudder surfaces become irrecoverable. One must carefully design an aircraft to enable sustained controllability at high AOA. Although it is possible to solve the problem of post-stall controllability through the use of thrust vectoring nozzles, the aerodynamic configuration itself must provide enough pitch down control capability to guarantee the aircraft to safely recover from post-stall AOA should the thrust vectoring mechanism malfunction. As a result, it is vitally important to study unconventional aerodynamic control mechanisms for high AOA flights."
I'm going to take your point to mean that we're either reading into what's not there, or we mis-remembered.
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Vini_Vidi_Vici
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This only exists in Russian designs. Usually TVC only requires the nozzles to move, so the engine itself is not effected. I don't know how the Russian ones are designed, but they do have short lifespan. However, the US designs, such as the ones power F22 and F35, they're all expected to last beyond 10,000 flight hours.
I would expect aluminum rather than steel in nose cones because aircraft manufacturing plants have plenty of experience forming parts from Al sheet and little from steel sheet and because Al sheet will be in stock. Also steel sheet in contact with Al would cause nasty electro-chemical effects.
My take on this is that for the use of any TVC you pay a price in reduced thrust and range and increased weight and maintenance. J-20 is able to maintain controllability post-stall without TVC. I don't know how far that is true for F-22. AFB? In other respects the advantages of TVC might well be much smaller for a canard design than for a tail aft one. Dr Song was thinking about the need to use TVC when he wrote this paper but he might well have concluded that the price was too high before the design of J-20 was decided. Don't forget J-20 has a much better configuration than that described in the paper.
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Yes, what he said was that he wanted the J-20 to be able to recover from the deep post stall aerodynamically in the event of the TVC engines failure, [I would suppose that meant in the event of a flame out etc], this from Pugachev-divers translation of April 2011. In this translation, he was very complimentary to the F-22 and its "inhumanely powerfull F-119", is how it was phrased. Great paper by the way and very honest, he did also express his concern that suitable powerplants might not be available on IOC-and in that case the J-20 would have to get by aerodynamically and that he hoped the J-20 would be up to the task by virtue of its aerodynamic prowess, hence the distant coupled canards in order to ensure pitch authority, I might add that Eng personally referred me to this post when I was having difficulty understanding that whole concept. Now while we are talking about the Master of the Aerodynamics of the JXX, how come we never hear anything from him these days?
You are quite right my friend, without TVC, the F-22 would likely perform in a similar vein as the Flanker family as their weight/planform are quite similar. And while I agree with your analysis of the J-20s post stall projections, I would add that to my knowledge we have no flight test data to confirm how or even if the J-20 handles post stall, hopefully when General Ma Xiaotian takes command of the PLAAF he might be more inclined to share some of these test points with us, however, 2001 has been away from the public eye for some time. I have on the basis of Dr. Songs paper and the apparently outstanding flight characteristics of 2001, the aileron rolls and very tight turns, stated for the record that the J-20 appears to be a very smart aeroplane, and I do agree with Eng that the J-20 may perform quite well without TVC, and that any post-stall manuevering may not be tactically necessary. I also agree with latenlazy that Dr. Song was hoping to employ a similar powerplant as the F-119 in the J-20, but that he made sure that his aeroplane would be a success irregardless.
In regard to Gen Ma, does anyone have any observations about his approach to being commander of the PLAAF, it did seem that Gen Xu may have been more "old school", although they are both former fighter pilots.
Actually boss man, the F-35 does not employ TVC in the conventional aircraft, the A and C, but only in the B STOVL variant, but you are quite correct about the F-22, and the TVC is indeed aft of the engine proper!
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