J-20 5th Generation Fighter VII

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latenlazy

Brigadier
gelgoog said:
Higher bypass ratio means larger frontal area of the engine and increased drag. Which makes it harder to have good kinematic performance in the aircraft. But it also means higher thrust with less fuel consumption. Like I said, as long as the bypass ratio is not obscenely large it can be mitigated to a degree with proper airframe design, the Saab Viggen had a bypass ratio close to 1, and it had a top speed over Mach 2.
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Actual performant thrust is flight condition dependent. In fact the larger the fan drag the less work you can extract from the engine, and drag goes up with area polynomially at increasing speeds, so these things don’t work as simple as you think.

Saab Viggen was not getting to Mach 2 with dry thrust man. It’s not super cruising with its 1 BPR engine. AB doesn’t count.
 
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AndrewS

Brigadier
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Blitzo said:
Very simplistically:
Higher bypass ratio in general means better fuel efficiency but means the engine (and thus the aircraft it's attached to) is intended to operate at lower speeds.
Lower bypass ratio (say, 0.25 if WS-15 has that, compared to 0.3 of F119 which is already relatively low) means the fuel efficiency is not as good but the engine (and thus the aircraft it's attached to) is intended to operate at higher speeds.

So what Siege is joking is that J-20 is kind of the ultimate form of a "high speed combat aircraft" of which J-8 was best known for.

But "J-8" is an aircraft with such a complex history and whose role is ultimately still very different to J-20, that I think comparing the two even in a cavalier way just introduces room for misunderstanding and confusion @siegecrossbow
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If the bypass ratio is 0.25, I think this indicates the WS-15 as being optimised for supercruise which makes sense.

Given the doctrinal shift to long range air superiority and strike, the limit of fighter endurance shifts to the pilot and the cruising speed.

That is 4h or 3.75h of flight time as per the Tornado and Flanker designs respectively. Various comments from elsewhere say something similar.

If we use the F-22 supercruise of Mach 1.6 as a guide, that is 2000km per hour.

That means long range missions to Guam (3000km away) are now feasible, assuming some airborne tanker support.

So given 1000 J-20s and 100+ Y-20U tankers by 2030, I can see the Chinese Air Force being able to operate large numbers of air superiority and strike missions on Guam.

This would also mean extended air superiority missions over Japan and the Philippines. Plus occasional missions to Singapore and the Malacca Straits.

In terms of US carriers, my read is that they would currently plan to operate some 2500-3000km from China, with occasional pushes to 1000/1500km. But if J-20s start operating in significant numbers at 3000km, those carriers will be pushed away to 3500km
 
Blitzo

Blitzo

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AndrewS said:
If the bypass ratio is 0.25, I think this indicates the WS-15 as being optimised for supercruise which makes sense.

Given the doctrinal shift to long range air superiority and strike, the limit of fighter endurance shifts to the pilot and the cruising speed.

That is 4h or 3.75h of flight time as per the Tornado and Flanker designs respectively. Various comments from elsewhere say something similar.

If we use the F-22 supercruise of Mach 1.6 as a guide, that is 2000km per hour.

That means long range missions to Guam (3000km away) are now feasible, assuming some airborne tanker support.

So given 1000 J-20s and 100+ Y-20U tankers by 2030, I can see the Chinese Air Force being able to operate large numbers of air superiority and strike missions on Guam.

This would also mean extended air superiority missions over Japan and the Philippines. Plus occasional missions to Singapore and the Malacca Straits.

In terms of US carriers, my read is that they would currently plan to operate some 2500-3000km from China, with occasional pushes to 1000/1500km. But if J-20s start operating in significant numbers at 3000km, those carriers will be pushed away to 3500km
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You've projected way too far ahead in terms of operational infinitives.

It's not that I necessarily disagree with everything you've said, but by posting that you're just opening a whole can of potential discussion surrounding how a western pacific conflict would be waged and something that is not inherently J-20 related.


Try to stay on topic and avoid giving yourself the opportunity to talk about things which deviate too far from a given topic at hand, especially in moments surrounding "big events" such as J-20A with two WS-15s making its maiden flight.
 
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drowingfish

Junior Member
Registered Member
Blitzo said:
You've projected way too far ahead in terms of operational infinitives.

It's not that I necessarily disagree with everything you've said, but by posting that you're just opening a whole can of potential discussion surrounding how a western pacific conflict would be waged and something that is not inherently J-20 related.


Try to stay on topic and avoid giving yourself the opportunity to talk about things which deviate too far from a given topic at hand, especially in moments surrounding "big events" such as J-20A with two WS-15s making its maiden flight.
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in general it is just better to have supercruise over no supercruise. because you will have more options available in terms of which airport to stage your sorties from, thus making it more difficult for the enemy to pick you off.
 
siegecrossbow

siegecrossbow

General
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drowingfish said:
in general it is just better to have supercruise over no supercruise. because you will have more options available in terms of which airport to stage your sorties from, thus making it more difficult for the enemy to pick you off.
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Supercruise has important tactical ramifications. The F-22, even without stealth, can harass 4th generation fighter aircraft with supercruise by both extending the missile's flight envelope, gain advantage in energy and altitude, and making it difficult for the opponents to target. It is more important than supermanueverability.
 
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stannislas

Junior Member
Registered Member
Phead128 said:
Would it be cost effective for WS-15 to be retrofitted on J-20s with WS-10C or AL-31FM2? What are the pros and cons. Would it be a modular replacement or need costly redesign?
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I don't think this would be an issue for chinese, they have J-10 originally designed with WS-10, but due to the delay of engine development, J-10 was tested and send to service with AL-31 for a long time until WS-10 is ready.

J-20 on the other hand was designed with WS-15, a next-gen engine much powerful than WS-10, i see no reason chinese will take any hesitation with reasons like cost once WS-15 is ready
 
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sndef888

Captain
Registered Member
stannislas said:
I don't think this would be an issue for chinese, they have J-10 originally designed with WS-10, but due to the delay of engine development, J-10 was tested and send to service with AL-31 for a long time until WS-10 is ready.

J-20 on the other hand was designed with WS-15, a next-gen engine much powerful than WS-10, i see no reason chinese will take any hesitation with reasons like cost once WS-15 is ready
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Will engine production be a bottleneck? I wonder how long it will take to ramp up production.

Someone said by 2025 so I guess it's another long hard 2 year wait
 
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