J-20 5th Gen Fighter Thread VI

[manqiangrexue]

The issue is, the AL-31s are Russian, not Chinese, and it's questionable as to which AL-31 the Russians would provide to the Chinese for testing and development purposes.

When you're working with prototypes, every "novel" element introduces a new point of failure and it's reasonable for the Chinese to use stock AL-31Fs at least in the earliest versions as the AL-31Fs are best understood given prolonged service in J-10s and J-11s.

First of all, you think China is a beggar? China is Salyut's best customer and Russia's most critical ally; it tells Russia which AL-31 version it wants to buy, and even if some were unavailable, it's be a long fall down before it settled on early 125kN versions.

Then, are you talking about prototype? Cus I'm not talking about prototypes; I'm talking about the production variant, which is a big jet and probably has some things missing on it like a gun in order to save weight. The priority will be engine power, not engines with longer service or overhaul interval.

On Wikipedia, there's a claim that the J-20 is using AL-31F M2s, which are 145 kN thrust engines used also on the Su-34 fighter-bombers. That is questionable, given that Al-31F M2s have never been in Chinese service.

It's not nearly as questionable as a 197kN WS-15. Nobody would have to know if China special ordered some FM2 from Russia for its premier fighter as interims. (As a matter of fact, China's far less likely to tell anyone than it is to keep mum.) Since its China's biggest heaviest jet and it needs to have the highest performance, China can buy a better version of the AL-31 from Russia than before. What part of this doesn't make sense or is hard to believe? The Cyrillic link presumably is the Russians talking about this sale. If you search "J-20 AL-31FM2" you will find many many other sources taking about this pairing; it is the most commonly cited engine for J-20 although none are authoritative sources. It's a very similar situation to what we "know" of WS-15's thrust numbers.

As for the Al-31FN Series 3, the Al-31FN Series 3 is specifically designed for the J-10, which includes a different gearbox location than on the Al-31F. Since we know the J-20's engine compartment is designed for WS-15, the engine compartment might be large enough to incorporate a different gearbox location.

Even if the WS-15's gearbox layout isn't totally permissive of stock AL-31FN3, do you think nobody can be bothered to move a gearbox location for the benefit of 24kN extra thrust on a J-20?

In either case, if you go with the Al-31F M2, and select the 180 kN thrust point, you still get roughly 1.45 T/W at 60% fuel and a bounding range of 22.5% T/W, which is high, but close enough to the range of American re-enginings of their fighter aircraft.

So your point is that with WS-15, J-20 will have a very high TWR? Thanks, everybody knew that coming into this discussion.

As for 197 kN, you know I've bashed those numbers as unrealistic, and others have pushed them as bench test figures, not installed thrust. But given that the F135 has reached 220 kN in bench tests, it's not unreasonable for the WS-15 to bench test 197 kN.

I don't know what you've done; I don't read everything you write. You're not bashing them now; all I see is you citing 197 more often than any other number including 180. Yeah, it's fine that a 180kN engine could possibly reach 197 on bench tests, but in that situation, there would be no reason to talk about that number in some ungraded thrust of 40% over a 140kN engine on a J-20B.

 

[siegecrossbow]

Don't know if it had been posted before.

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[by78]

@Inst, could you please, for God's sake, take your obsessive-compulsive speculations to a different thread? Be considerate of the wider community here.

 

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