As per the last video taken down, the chief implied they had installed TVC on J-20 long ago and decided the trade off made no sense to have J-20 TVC.
J-20 5th Gen Fighter Thread VIII
- Thread starter Blitzo
- Start date
An F-22 (and indeed J-20) can be detected by UHF-band volume search radar anyway.
TVC making micro-pitch adjustments shouldn't make any difference in this scenario.
Without TVC, you have very slight movements of the control surfaces. But they're designed to be stealthy across an arc, so again, it shouldn't make a difference?
And if a stealth fighter is actively manoeuvring, it's control surfaces are going to be making large movements anyway. And by all accounts, short range AAMs are tremendously effective and all-aspect, so there shouldn't be any need for dogfighting.
So TVC just doesn't seem worth the cost and loss of thrust
Flat nozzles without thrust vectoring would still be better for infrared, like the YF-23 for example, however I'm unsure what drawbacks they have.
We had a Chinese paper on it.
Was indeed better for infrared but it loses trust (think it might was like 10%?).
The main reason of 2D TVC loosing thrust is the 2D flow of exhaust. 2D nozzle forces the 3D circular flow into a flat flow, essentially chocking the expulsion of the gas. It is the same principle as any TVC looses thrust when diverting the flow, the more degrees change the higher the lose, 2D's effect is more severe than simply diverting the direction for a few degrees.
It is nice to see they still have some space for the gun. It is not some type of design oversight.
Regarding TVC, at 20:20 he said:
- we have no intention of installing TVC on J-20.
- "maneuverability is the king" is not the way of fight.
- Something is a good bragging (得瑟) in exhibition, but we need real value.
His first point means that even if WS-15 has TVC developed or tested, even if J-20 has been tested and studied with TVC, we should not expect to see operational J-20 with TVC.
TVC is not just for bragging. It allows the fighter to quickly point its nose at an off boresight direction. Which means IR missile sensors on the fighter can lock onto a target that would have otherwise not been able to be engaged. It also enables an aircraft to quickly change its trajectory in a hard to predict fashion, which helps with avoiding incoming enemy missiles. Also important is that it enables the creation of aircraft with smaller tail control surfaces which is then more stealthy.
The main disadvantage with TVC is cost. Cost of acquisition, and cost of maintenance. At least Russian TVC systems are supposed to have like a tenth the MTBO compared to the rest of the engine. Which is why the Russians don't use TVC on fighter bombers like the Su-34, or on aircraft which are supposed to have low maintenance and acquisition cost like the MiG-35. The TVC is used just on the high end heavy fighters for aerial combat.
The main disadvantage with TVC is cost. Cost of acquisition, and cost of maintenance. At least Russian TVC systems are supposed to have like a tenth the MTBO compared to the rest of the engine. Which is why the Russians don't use TVC on fighter bombers like the Su-34, or on aircraft which are supposed to have low maintenance and acquisition cost like the MiG-35. The TVC is used just on the high end heavy fighters for aerial combat.
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It isn’t so much that it has no value as that it won’t add enough to justify the additional complexity for the time being. It will certainly be featured on J-35 and Sixth gen. But for J-20 it may not be ready in time to meet a certain deadline set by CMC.