J-20 5th Generation Fighter VII

Overbom said:

Yes, I was also thinking about if it was worth to allocate the much in demand WS-10C engines to older J-20 aircraft (and probably restricting production of new J-20) when they could be used for new J-20 instead

But this could also depend on how much electricity/power future J-20 updates will need and if their AL-31F engines could supply that demand.

Knowing that, my next question would be if we have data on how much electricity is generated by the AL-31F and WS-10C engines

Click to expand...

Anyway, when Al-31f they will reach end of life, it's possible that the WS-15 will be ready. So new ones with WS-15 and old ones updated with WS-10C ?

Waiting for new J-20b pictures...don't know if they are still pumping J-20 or waiting for j-20b testing ? Someone have news on a new batch ?

Atomicfrog said:

Anyway, when Al-31f they will reach end of life, it's possible that the WS-15 will be ready. So new ones with WS-15 and old ones updated with WS-10C ?

Waiting for new J-20b pictures...don't know if they are still pumping J-20 or waiting for j-20b testing ? Someone have news on a new batch ?

Click to expand...

Not sure if the older airframes are compatible with WS-15 without modifications to air inlet.

Atomicfrog said:

Anyway, when Al-31f they will reach end of life, it's possible that the WS-15 will be ready. So new ones with WS-15 and old ones updated with WS-10C ?

Waiting for new J-20b pictures...don't know if they are still pumping J-20 or waiting for j-20b testing ? Someone have news on a new batch ?

Click to expand...

lets suppose, AL-31F complete its service life. and WS-15 already entered in LRIP stage. so no point to equip J-20 with older WS-10C engine coz WS-15 is the final engine of J-20. this is my opinion.

my second question. does older J-20 need some modification in fuselage/air inlet to equip with WS-15 engine ?

siegecrossbow said:

Not sure if the older airframes are compatible with WS-15 without modifications to air inlet.

Click to expand...

Was more about disponibility of WS-10 for older airframe wi AL-31 while WS-15 are in the new airframes.

siegecrossbow said:

Not sure if the older airframes are compatible with WS-15 without modifications to air inlet.

Click to expand...

I’ve only ever seen the “modified air inlet” point brought up as speculation, never factually validated.

minusone said:

omg，CCTV just revealed J20 max velocity = 2.8 mach

Please, Log in or Register to view URLs content!

Click to expand...

Who is this guy being randomly quoted?

J-20 maximum speed is Mach 2.0, which is all you really need. It's the same as Su-57 and F-22 maximum speed. In fact F-22 at Mach 2.0 is only using 36% afterburner (118% throttle, with 100% being full dry thrust and 150% being full afterburner), but it's normally limited to that speed because any faster will just be a maintenance nightmare for the skin. J-20's DSI might only be stable up to that point before you run into conditions like inlet buzz, especially since it doesn't have the bypass louvres like on the F-22 (neither does the Su-57, actually). But again it doesn't matter because being faster than Mach 2 is never used operationally unless you're a MiG-31 and even then it's questionable in a modern environment when the thermal signature will light you up like a Christmas tree.

RadDisconnect said:

Who is this guy being randomly quoted?

J-20 maximum speed is Mach 2.0, which is all you really need. It's the same as Su-57 and F-22 maximum speed. In fact F-22 at Mach 2.0 is only using 36% afterburner (118% throttle, with 100% being full dry thrust and 150% being full afterburner), but it's normally limited to that speed because any faster will just be a maintenance nightmare for the skin. J-20's DSI might only be stable up to that point before you run into conditions like inlet buzz, especially since it doesn't have the bypass louvres like on the F-22 (neither does the Su-57, actually). But again it doesn't matter because being faster than Mach 2 is never used operationally unless you're a MiG-31 and even then it's questionable in a modern environment when the thermal signature will light you up like a Christmas tree.

Click to expand...

It's Xi Yazhou, but what he is saying is that 央视, basically central state/national media of China, stated that the top speed of the J-20 is 2.8 mach.

While there have been cases of incorrect statements and reporting from 央视, cuz people can make mistakes, but it is also often take as an official source including confirmation of stuff.

As for this case, it could very much be true that the top speed is 2.8 mach, but even then it doesn't mean that much, because we really have no idea of how applicable or useful it would be for combat (just because somethings 'top speed, max range' etc. is X number, doesn't mean that it will automatically be really relevant for combat).

RadDisconnect said:

Who is this guy being randomly quoted?

J-20 maximum speed is Mach 2.0, which is all you really need. It's the same as Su-57 and F-22 maximum speed. In fact F-22 at Mach 2.0 is only using 36% afterburner (118% throttle, with 100% being full dry thrust and 150% being full afterburner), but it's normally limited to that speed because any faster will just be a maintenance nightmare for the skin. J-20's DSI might only be stable up to that point before you run into conditions like inlet buzz, especially since it doesn't have the bypass louvres like on the F-22 (neither does the Su-57, actually). But again it doesn't matter because being faster than Mach 2 is never used operationally unless you're a MiG-31 and even then it's questionable in a modern environment when the thermal signature will light you up like a Christmas tree.

Click to expand...

There are actually two questions, one is if 2.8 is legitimate at some specific condition, the other is whether 2.8 is useful in real life. I don't think anyone here is arguing for the usefulness of the second question.

It is like loud speaker of my home cinema is 80W which I would never use but the figure is still very meaningful to determine the setups regular performance. Performance of speaker rated at 80W is much better than one rated at 40W when both are running at 20W.

Mach number changes according to altitude which affects temperature and air density. Same ground speed is mach 2 at near sea level but mach 2.3 at 10000 meter. Some aircraft's speed and altitude are known, but do we know the altitude specification of mach 2.0 of J-20?

J-20 having a higher top speed than F-22 and Su-35 is guaranteed if the engine is in the same class of thrust due to the proportion of the air-frame. This is used often by some people to erroneously call J-20 an interceptor.

RadDisconnect said:

Who is this guy being randomly quoted?

J-20 maximum speed is Mach 2.0, which is all you really need. It's the same as Su-57 and F-22 maximum speed. In fact F-22 at Mach 2.0 is only using 36% afterburner (118% throttle, with 100% being full dry thrust and 150% being full afterburner), but it's normally limited to that speed because any faster will just be a maintenance nightmare for the skin. J-20's DSI might only be stable up to that point before you run into conditions like inlet buzz, especially since it doesn't have the bypass louvres like on the F-22 (neither does the Su-57, actually). But again it doesn't matter because being faster than Mach 2 is never used operationally unless you're a MiG-31 and even then it's questionable in a modern environment when the thermal signature will light you up like a Christmas tree.

Click to expand...

There are other ways to do inlet bypass than the F-22’s dorsal bypass doors, and I’m preferential to the theory that the double hexagonal meshes on the sides of the J-20’s inlet are intake and bleed control features, given that their location makes plumbing for any other kind of function pretty unlikely.

taxiya said:

J-20 having a higher top speed than F-22 and Su-35 is guaranteed if the engine is in the same class of thrust due to the proportion of the air-frame. This is used often by some people to erroneously call J-20 an interceptor.

Click to expand...

Certainly faster than the F-35, but the F-22, not certain. While J-20 is overall longer, most of the additional length is in the fuselage so it has more volume, while proportionally a lot of the F-22's overall length is in the tail surfaces. Without seeing the cross section plot it's hard to know how drag compares. Again, not that it really matters in the grand scheme of things.