J-20 5th Gen Fighter Thread VI

[siegecrossbow]

Are there any videos of the flight demos at the open day? I can't find any on YouTube.

Not on YouTube but available on Chinese streaming website.

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Pretty conservative display.

 

[Xizor]

We probably should start talking about the WS-15's purported 197 kN thrust.

First of all, I want to point out the insanity of it. 197 kN on a 18,000 kg empty weight fighter gets you to roughly 1.6 T/W at 60% fuel.

I/e, at this type of T/W, ITR could be entirely replaced by STR in terms of the 9G limit at many flight regimes.

Which calls into question how credible such claims are. For instance, the WS-15's primary problem is currently reliability, i.e, the potential of the J-20 airframe is being limited by WS-10-type engines right now, and the sooner reliable WS-15 come online, the sooner the J-20 stops being limited by such. If the achieved thrust has been rising from 160 kN to 170 kN to 180kN, all of these thrust ratings are sufficient for the J-20 to be competitive as a fighter. Wouldn't the target of development NOT be getting the WS-15 to higher max thrust, but rather getting the WS-15 engine to be reliable enough to be installed?

Second, we should discuss what you actually do with 1.6 T/W.

Two options immediately spring to mind. First, you can switch to 2D TVC for greater rear stealth, but poorer maneuverability. That bleeds off about 17% of the thrust due to the shifting geometries of the exhaust. That is one option with the J-20; that you go back to about 1.3 T/W at dogfight weights but further increase stealth.

Second, you can just keep the thrust; i.e, by replacing ITR with STR, rippled missile fires are now a lot less dangerous because normally, the point of such ripple-firing is that the first missile forces you to bleed energy, and the second missile actually does the hit. By replacing ITR with STR, the ripple fire technique stops working and ripple fire stops increasing the effective range of air-to-air missiles.

Wouldn't it be better if we wait for some time before discussing the engines? Do we have enough material (read leaks, rumors, reveals) to engage in productive speculations and conclusions? Also we ought to consider and reconsider the discussion of WS-15 taking place under the J-20 thread. It would be better since we don't have a steady stream of information for WS-15. Much of the discussion will be populated with "would", "should", "ought to" etc.
I haven't seen even WS-10 being equipped in numbers in the J-20. Of course, there is credible images of WS-10 on J-20.But has it replaced AL-31 completely?
WS-15 is a big deal for China as well as China's potential adversaries. It is up there along with SSBNs, SSNs and ICBMs. We have to be patient.

 

[Inst]

Wouldn't it be better if we wait for some time before discussing the engines? Do we have enough material (read leaks, rumors, reveals) to engage in productive speculations and conclusions? Also we ought to consider and reconsider the discussion of WS-15 taking place under the J-20 thread. It would be better since we don't have a steady stream of information for WS-15. Much of the discussion will be populated with "would", "should", "ought to" etc.
I haven't seen even WS-10 being equipped in numbers in the J-20. Of course, there is credible images of WS-10 on J-20.But has it replaced AL-31 completely?
WS-15 is a big deal for China as well as China's potential adversaries. It is up there along with SSBNs, SSNs and ICBMs. We have to be patient.

I think some effort has to be made to discuss the incredible thrust shift between a J-20A and a J-20B. If we assume the WS-10s on the J-20A are roughly 130kN max thrust, the WS-15s on the J-20B range from a 40 (180kN) to 50% (197kN) increase in thrust.

This kind of re-engining is incredible. In the F-14D's case, thrust rose by 20% compared to the F-14A. In the F-16's case, thrust rose by about 25%. In the F-16's case, also, the increased thrust was partially absorbed by improved electronics and structural reinforcement for strike roles.

 

[by78]

I think some effort has to be made to discuss the incredible thrust shift between a J-20A and a J-20B. If we assume the WS-10s on the J-20A are roughly 130kN max thrust, the WS-15s on the J-20B range from a 40 (180kN) to 50% (197kN) increase in thrust.

This kind of re-engining is incredible. In the F-14D's case, thrust rose by 20% compared to the F-14A. In the F-16's case, thrust rose by about 25%. In the F-16's case, also, the increased thrust was partially absorbed by improved electronics and structural reinforcement for strike roles.

Start a separate thread please.

 

[Inst]

This kind of shift between interim engines and final engines has to factor into aircraft design, i.e, the .67m^2 inlets of the Su-27 and the J-20 (if DSI is treated as a blocker) only make sense when we consider the Al-31F / WS-10. Once you get to WS-15, the inlets are now choking the engines due to insufficient size. Increasing their size either requires a DSI redesign or modifying the entire fuselage to support larger intakes.

 

[by78]

More high-resolution images.

 

[manqiangrexue]

I think some effort has to be made to discuss the incredible thrust shift between a J-20A and a J-20B. If we assume the WS-10s on the J-20A are roughly 130kN max thrust, the WS-15s on the J-20B range from a 40 (180kN) to 50% (197kN) increase in thrust.

This kind of re-engining is incredible. In the F-14D's case, thrust rose by 20% compared to the F-14A. In the F-16's case, thrust rose by about 25%. In the F-16's case, also, the increased thrust was partially absorbed by improved electronics and structural reinforcement for strike roles.

I think the reason you are getting these numbers is because you are selecting the lowest fathomable, not even realistic, numbers for the WS-10X and taking the highest imaginable for the WS-15. Most sources, although none with absolute authority, say that the J-20A uses AL-31FM2, which is a Russian engine with 145kN thrust. If this is replaced by a WS-10 variant, I think it's safe to assume that at the very least, it won't be much worse in wet thrust, but possibly better. So 145kN is more realistic for the J-20A, perhaps higher. Then, the most commonly cited number for WS-15 is 180kN and that is already monstrous; there is absolutely no need to go to 197kN. And this is assuming that the engineers reached their target thrust; if they don't or it's taking too long, it's totally possible to release the engine for use at some 170kN or so (assuming other parameters are acceptable). If the engineers got it up to 180 with acceptable performance factors in other areas, it's ready to go as WS-15A. There is no time to keep tweaking it up further at the expense of holding up J-20B production. So, I'm looking at an increase to 180kN from at least 145kN which is at most a 24% increase. And all these numbers are totally haywire because we don't really know how much thrust WS-10X J-20A has and we really really don't know how much thrust WS-15 J-20B will have. I don't know why we're having this discussion really.

 

[Biscuits]

WS-15s initial problems sound almost exactly the same as F-35 engine initial problems, except F-35 started being built earlier, and China didn’t stick the fire hazard engines into planes.

It’s too early to say whether it would be sustainable at 197kN or whether that is some sort of overclocking output that can’t be maintained consistently.

But given that a large part of the J-20s mission would be to hunt and kill enemy stealth fighters as an interceptor, it will need every tool to outturn enemy planes. The near future and existing 5th gen today all possess high levels of maneuverability. An interceptor in this era must have truly exceptional fighting capability, and that sort of capability can be granted by having twin 190kN+ 3D thrust vectoring powerplants.

 

[azesus]

J-20 main role is to bypass escort fighters and being the stealth spoting eye forward penetrating scout for the J-16 carrying extra long range PL-21 hunt force multipliers like oil tanker and early warning command control once those are gone remaining escort fighters will have no eyes no leg range turning on radar will make it much easier target turning on flashlight in absolute dark night in the vast Pacific ocean no where for emergency landing once the fuel is empty war is not knight joust if you're fighting fair then you are not trying, missiles will always have way more kinematic performance than platforms so over chasing fighter engine performance is a fruitless pursuit

 

[weig2000]

J-20 main role is to bypass escort fighters and being the stealth spoting eye forward penetrating scout for the J-16 carrying extra long range PL-21 hunt force multipliers like oil tanker and early warning command control once those are gone remaining escort fighters will have no eyes no leg range turning on radar will make it much easier target turning on flashlight in absolute dark night in the vast Pacific ocean no where for emergency landing once the fuel is empty war is not knight joust if you're fighting fair then you are not trying, missiles will always have way more kinematic performance than platforms so over chasing fighter engine performance is a fruitless pursuit

I just realized that you wrote the above long sentence without a single punctuation mark! I was trying to finish reading and understanding it in one breath, but couldn't hold it in the end. LOL.