Can J-8 supercruise?

MIGleader said:

i believe supercruise means to fly at mach1 plus without using afterburners. a subsonic cruse may mean that they canfly below mach 1 without afteburners, which all fighters can.

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There are two basic deffinitions. One is to simply be able to fly above mach 1 without using afterburners. This is not too difficult, and most modern fighters can probably acheive this, at least in a clean configuration. J-8 should deffinately be able to do this.

The other deffinition, which I think is better and more useful, is the ability to cruise in the fully supersonic regime rather than in the transonic regime. Baiscally there are three different speed regimes that fighters fly through: subsonic(<Mach .8), transonic (mach .8-mach 1.3), and supersonic (>mach 1.3).

From wikipedia:

Transonic is an aeronautics term referring to a range of velocities just below and above the speed of sound (about mach 0.8 - 1.3). It is defined as the range of speeds between critical mach, when some parts of the airflow over an aircraft become supersonic, and a higher speed, typically near Mach 1.2, when all of the airflow is supersonic. Between these speeds some of the airflow is supersonic, and some is not.

Most modern jet powered aircraft spend a considerable amount of time in the transonic regime. This is particularly important due to an effect known as wave drag, which is prevalent in these speed ranges. Attempts to combat wave drag can be seen on all high-speed aircraft; most notable is the use of swept wings, but another common form is a wasp-waist fuselage as a side effect of the area rule.

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The drag that the aircraft experiences goes up significantly in the in the transonic regime, but it actually goes down a bit when you enter the fully supersonic regime. An aircraft at mach 1.4 will likely experience less drag than one at mach 1.2, which is why an aircraft can experience a significant fuel savings if it can stay above the transonic speeds. This type of supercruise is harder to achieve than simply goning above mach 1, but it is much more useful. Concorde, F/A-22, Typhoon, and probably Rafale are capable of this, though I think the F/A-22 is the only fighter that can do it with a full weapons load. This the typ of supercruise that I was thinking of when I asked about the J-8.

Here's a great link to look at:


The first jet to supercruise is the BAC Lightning. Great performance - it could climb 50,000 ft per min and intercept U2's at 88,000 ft. Kinda of like a UK-made "Super MiG-21", but suffered poor range and weapons load (just like the MiG).

trkl said:

J-10? I doubt J-10 will ever be able to supercruise. While J-10 has excellent agility and low speed manuverability, it is not meant to be a high speed intercepter like the J-8, and it is difficult to make a fighter that can supercruise while only using a single turbofan. The J-8 and J-10 are very close to the same weight, but the J-8 actually has over 30% more dry thrust than the J-10. This is why the "old fashioned" J-8 has a much better chance of achieving supercruise than the more advanced J-10.

As for the Chinese media bragging about it, mabey they would and mabey they wouldn't. It's hard to tell sometimes what sorts of things the Chinese will play up for propaganda and what sorts of thing they will hide due to secrecy or because they avoid giving ammunition to the "China threat theorists". Or they could just assume that no one would care, since it is more of an academic curiosity than something with actual operational utility. The J-8's turbojets must use up a lot of fuel even while running dry, and the J-8 does not have internal stowage like the F-22 so putting weapons on it would significantly degrade it's performance.

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J-10 actually achieved the fastest speed in plaaf history. For a single engine plane, it has a lot of thrust. Once we get the twin-engined version, I suspect it will have both tvc and supercruise capability.

As for "subsonic supercruise", yeah, pretty much every plane has it.

tphuang said:

J-10 actually achieved the fastest speed in plaaf history. For a single engine plane, it has a lot of thrust. Once we get the twin-engined version, I suspect it will have both tvc and supercruise capability.

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Fastest speed in PLAAF history? All the information that I have seen says that it has a max speed of only Mach 2. AL-31FN is a powerful engine, but it still can't match 2 WP-14b. And it is even further from being able to match 2 AL-31F...

trkl said:

Fastest speed in PLAAF history? All the information that I have seen says that it has a max speed of only Mach 2. AL-31FN is a powerful engine, but it still can't match 2 WP-14b. And it is even further from being able to match 2 AL-31F...

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J-10's real top speed is classified. Let's just say that the fighter frame and engine allows for faster speed than mach 2. Its plane structure with canard and delta wing allows for greater speed. It seems that all the new fighters are just using mach 2 as the top speed, the real top speed is all classified. It's not just about total thrust, but also T/W ratio and stuff like that. Su-27/30 has even greater total thrust, but it hasn't travelled that fast with plaaf.

Here is the link

Well, J-8 has the thrust for supercruise, but lacks the aerodynamics. However, there are engines that can offer even more thrust.

tphuang said:

J-10's real top speed is classified. Let's just say that the fighter frame and engine allows for faster speed than mach 2. Its plane structure with canard and delta wing allows for greater speed. It seems that all the new fighters are just using mach 2 as the top speed, the real top speed is all classified. It's not just about total thrust, but also T/W ratio and stuff like that. Su-27/30 has even greater total thrust, but it hasn't travelled that fast with plaaf.

Here is the link

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If the estimates of its weight are anywhere near accurate, J-10 not only has less total thrust than J-8 and J-11, but it also has a lower T/W ratio.

Do you have a link in English? I can't really read Chinese and the article won't let me cut and paste it into a translating program. I think it says that J-10 flew at mach 2.4, but a souce I can read would be better.

trkl said:

If the estimates of its weight are anywhere near accurate, J-10 not only has less total thrust than J-8 and J-11, but it also has a lower T/W ratio.

Do you have a link in English? I can't really read Chinese and the article won't let me cut and paste it into a translating program. I think it says that J-10 flew at mach 2.4, but a souce I can read would be better.

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T/W ratio of the engine.

Of course it has less thrust than J-11, it has one engine. Once it gets WS-10A, it will no longer have less total thrust than J-8. I'd take 140 kN of turbofan thrust over 140kN of turbojet thrust anyday of the week.

If you just talk about speed, it's dependent on plane structure, material it's made from and engine. J-8 may have good thrust, but it's other areas are just sorely lacking. Let's put it this way, JH-7A has greater total thrust than both J-8 and J-10, but it's max speed is listed at mach1.69 I think?

What the article says is that in January of 2004, J-10 flied the fastest speed in plaaf history. It speculates whether plaaf has flied the claimed mach2.4 with su-27 or not. If that is true, then J-10's fastest flown speed is mach2.4, if not, then J-10's fastest speed is at least mach2.2


more on this:

another article claiming mach2.2 top speed for J-10

tphuang said:

T/W ratio of the engine.

Of course it has less thrust than J-11, it has one engine. Once it gets WS-10A, it will no longer have less total thrust than J-8. I'd take 140 kN of turbofan thrust over 140kN of turbojet thrust anyday of the week.

If you just talk about speed, it's dependent on plane structure, material it's made from and engine. J-8 may have good thrust, but it's other areas are just sorely lacking. Let's put it this way, JH-7A has greater total thrust than both J-8 and J-10, but it's max speed is listed at mach1.69 I think?

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If you don't care about fuel consumption, the 140kn of turbojet thrust should actually be better, since it it should be better at maintaining thrust at high speeds than the turbofan. A new J-8 with 2 WP-18b turbojets should have 108 kn dry thrust and 153 kn total thrust.

I know there are a lot of facters that affect the top speed, including things like aerodynamics. And many fighters have their speed limited by what the materials that they are made of can withstand, rather than by thrust/drag relationships.

The idea that J-10 can go faster than mach 2 makes sense, since the J-10 is in a similar thrust and weight class as the Mach 2 F-16 and the J-10's variable inlet should give it a performance edge over the F-16's fixed inlet at high speeds. Still, it is surprising if J-10 can exceed the speed of aircraft like J-8 and J-11. Mabey J-8 and J-11 are limited by materials and J-10 can go faster due to better materials?

let's put it this way, in an internal plaaf military exercise between the mkk and J-10. People who say this claimed that J-10 was faster and moved much better than mkk despite carrying much heavier payload.

If you read the article, it basically mentions that the engine and plane structure allows for really good manuverability at high speed. I don't know the exact physics behind this, but think about it this way:

f=ma, and F = thrust - drag. Normally, drag increases when speed increases, but decreases when you go higher up (less resistance).

Since J-10 has good aerodynamic configuration, therefore the drag doesn't increase that much at higher speed, so acceleration is still possible, so the speed can still go up.

On the other hand, J-8's configuraiton is nowhere near as good, so even with slightly larger thrust, the force becomes 0 when speed is really fast. Then, acceleration is no longer possible. Even if it's frame might be able to stand for greater speed, the drag will stop it.

As for J-11, it needs a greater difference between thrust and drag, because mass is greater, so acceleration is smaller if thrust and drag difference do not change. J-11 is also larger, so the drag will be much larger than that of J-8/J-10.

I can go on and on about this, but I need to sleep now.