J-20... The New Generation Fighter III

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latenlazy

Brigadier
I stand by the notion that the J-20 will need TVC for both stealthier cruise flight and supersonic maneuverability. I COULD be wrong on that, but I haven't heard anything yet that would dissuade me.
 
Engineer

Engineer

Major
latenlazy said:
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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Yes.

Air Force Brat said:
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?
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What Pugachev-diver translated were not the words of Dr. Song. The fact remains that in publicly avaiable materials, Dr. Song never explicitly stated that J-20 will have TVC.
 
Air Force Brat

Air Force Brat

Brigadier
Super Moderator
Engineer said:
Yes.



What Pugachev-diver translated were not the words of Dr. Song. The fact remains that in publicly avaiable materials, Dr. Song never explicitly stated that J-20 will have TVC.
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An honest man perhaps, who was he and where is Dr. Song, I am quite certain that you did point me to that post? I understood that was Dr. Songs paper, my bad, however, it is a great paper, and it is HONEST. apologies all around, so I will read the link that you did just post. AFB

Ok Chief, I did quote from that paper in section 2, and he DOES state that the aircraft must be recoverable in the event of a TVC failure, that does lead me to believe that he envisioned the JXX with TVC, so that is in fact where Latenlazy and I concluded that Dr. Song anticipated TVC. Now to be very honest, you are right in that he does not explicitely say that, but Late and I agree that he does imply that from the last half of the paragraph, but you are indeed right again. So WHO did write the Pugachev-diver translated paper?
 
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Engineer

Engineer

Major
latenlazy said:
I stand by the notion that the J-20 will need TVC for both stealthier cruise flight and supersonic maneuverability. I COULD be wrong on that, but I haven't heard anything yet that would dissuade me.
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The argument that J-20 needs TVC stems from the premise that J-20 is going to fly like an airliner. Obviously, that premise is false hence the argument is also false. Moreover, the deficiencies that proponents of TVC claimed to rectify don't really exist on a canard configuration in the first place. This is especially so with "unconventional aerodynamic control" that Dr. Song purposely designed for the J-20.
 
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latenlazy

Brigadier
Engineer said:
The argument that J-20 needs TVC stems from the premise that J-20 is going to fly like an airliner. Obviously, that premise is false hence the argument is also false. Moreover, the deficiencies that proponents of TVC claimed to rectify don't really exist on a canard configuration in the first place. This is especially so with "unconventional aerodynamic control" that Dr. Song purposely designed for the J-20.
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I don't think that's the only argument for why the J-20 needs TVC. Having TVC can also help minimize deflections during cruise flight for signal management purposes and aid in supersonic maneuverability when using control surfaces induce drag penalties. None of these reasons assume that the J-20 will fly like an airliner without it. The first one assumes that TVC can help preserve stealthy flight because the J-20 is a VLO platform, and the second assumes that TVC can offer some benefits over control surfaces in the supersonic regime because the J-20 is meant to supercruise. I have not yet heard an argument for why these are not valid reasons.
 
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Engineer

Engineer

Major
latenlazy said:
I don't think that's the only argument for why the J-20 needs TVC. Having TVC can also help minimize deflections during cruise flight for signal management purposes and aid in supersonic maneuverability when using control surfaces induce drag penalties. None of these reasons assume that the J-20 will fly like an airliner without it. The first one assumes that TVC can help preserve stealthy flight because the J-20 is a VLO platform, and the second assumes that TVC can offer some benefits over control surfaces in the supersonic regime because the J-20 is meant to supercruise. I have not yet heard an argument for why these are not valid reasons.
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The first reason is already rebutted many times. A large enough deflection that can hurt RCS would mean the aircraft is maneuvering for its life, at which point the aircraft has long been seen and RCS is meaningless. The rebuttal for the second reason was in my very last post. Namely, the deficiencies that proponents of TVC claimed to rectify don't really exist on a canard configuration in the first place.
 
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latenlazy

Brigadier
Engineer said:
The first reason is already rebutted many times. A large enough deflection that can hurt RCS would mean the aircraft is maneuvering for its life, at which point the aircraft has long been seen and RCS is meaningless. The rebuttal for the second reason was in my very last post. Namely, the deficiencies that proponents of TVC claimed to rectify don't really exist on a canard configuration in the first place.
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On the first point, you originally brought up that point to refute that canards were not inherently detrimental to stealth. That is a good point, but canards not being detrimental to stealth does not mean deflections are not detrimental to stealth. Canard deflections are as detrimental to stealth as any other form of control surface deflections.

On the second point, you haven't really refuted the supersonic maneuverability claim. The crutch of that claim is the notion that control surface deflections (canards, tail planes, etc) induce greater drag penalties at supersonic speeds than vectored nozzles. You're either going to have to show me that control surface deflections don't induce so much drag that they make TVC favourable, or else show me that whatever the net benefits/costs of TVC, taking the drag penalties for surface deflections at supersonic speeds is still the better option.
 
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no_name

Colonel
IMO since flattening the nozzles reduces thrust but also suppress IR signature, they should design a circular TVC for J-20 that can be flattened, if such a one is in the works. That way the pilot can have the option of lowering his IR sig on approach or rounding his nozzles to squeeze every juice out of the engines when needed.
 
P

paintgun

Senior Member
no_name said:
IMO since flattening the nozzles reduces thrust but also suppress IR signature, they should design a circular TVC for J-20 that can be flattened, if such a one is in the works. That way the pilot can have the option of lowering his IR sig on approach or rounding his nozzles to squeeze every juice out of the engines when needed.
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i don't think that's a feasible engineering

besides, you need a heavy and thick nozzle shielding like the ones on F-22 for it to act as IR suppressor, the shape of the nozzle just happen to be flat as it only employs 2D TVC

IMO a flat nozzle won't happen on the J-20, the position of engines are way too aft for such modification
 
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