You got a point there. But the plane was orginally designed in the late 60's early seventies when the manuvrability wasen't the to priority to long range interceptors.
China miliary plane design
- Thread starter wmdco
- Start date
Dear Crob:
The need for length in the J-8 fuselage comes from a desire to reduce drag, by keeping the cross-sectional and frontal area to a minimum and a desire to incorporate enough useful volume within that low-drag airframe. The controlling factors for China during the J-8's design was the unavailability of more powerful aircraft engines.
The solution was therefore to use two of the J-7's engines in a closely-coupled, side-by-side arrangement, along with careful attention paid to the area rule. As the J-8 was to be a heavyweight interceptor (at least for the PLAAF of that time), to obtain useful range and operating radius one had to lengthen the airframe to accomodate the neccesary tankage (and other stuff).
The requirement for high supersonic speeds (Mach 2+) also meant that the wings would have to have a high degree of sweep and a relatively thin cross-section. Such a wing has many limitations - basically its' low lift at low and medium speeds.
Low lift means smaller payloads and higher wing loading, thus limiting the manueverability in those portions of the flight envelope. But as you note, high wing loading does not seem to be a problem for the J-8.
Much of the low and medium speed handling problems presumably were minimized by the addition of wing fences - thereby reducing the turbulent, drag-inducing span-wise flow.
Overall the configuration chosen by the designers was a very conservative one, it did not depart from the tailled-delta design. Basically the planform of the J-81 resembles a stretched-out MiG-21.
The long fuselage imposes other limitations, such as high induced-drag during maneuvering, and higher stresses than a short fuselage would. The greater momoents of inertia of a long fuselage also requre greater control forces for manuevering.
It has it's advantages however, that greater length contributes to stability in high-Mach supersonic flight.
After a very long developement period (much of which you have recorded admirably). The J-8 finally matured as the J-8II, the solid nose incorporating a radar powerful enough for BVR interceptions.
Still although the PLAAF (and especially AVIC 1) would like to pretend otherwise, the J-8 remains basically an interceptor, not a multi-role aircraft.
With the developement of the J-10 and J-11, the remaining J-8's in the PLAAF's and PLAN's inventory will probably be retired. Given the reluctance of the PLA in general to scrap equipment before it actually breaks down, that will be a long time coming.
Best Regards,
Dusky Lim
The need for length in the J-8 fuselage comes from a desire to reduce drag, by keeping the cross-sectional and frontal area to a minimum and a desire to incorporate enough useful volume within that low-drag airframe. The controlling factors for China during the J-8's design was the unavailability of more powerful aircraft engines.
The solution was therefore to use two of the J-7's engines in a closely-coupled, side-by-side arrangement, along with careful attention paid to the area rule. As the J-8 was to be a heavyweight interceptor (at least for the PLAAF of that time), to obtain useful range and operating radius one had to lengthen the airframe to accomodate the neccesary tankage (and other stuff).
The requirement for high supersonic speeds (Mach 2+) also meant that the wings would have to have a high degree of sweep and a relatively thin cross-section. Such a wing has many limitations - basically its' low lift at low and medium speeds.
Low lift means smaller payloads and higher wing loading, thus limiting the manueverability in those portions of the flight envelope. But as you note, high wing loading does not seem to be a problem for the J-8.
Much of the low and medium speed handling problems presumably were minimized by the addition of wing fences - thereby reducing the turbulent, drag-inducing span-wise flow.
Overall the configuration chosen by the designers was a very conservative one, it did not depart from the tailled-delta design. Basically the planform of the J-81 resembles a stretched-out MiG-21.
The long fuselage imposes other limitations, such as high induced-drag during maneuvering, and higher stresses than a short fuselage would. The greater momoents of inertia of a long fuselage also requre greater control forces for manuevering.
It has it's advantages however, that greater length contributes to stability in high-Mach supersonic flight.
After a very long developement period (much of which you have recorded admirably). The J-8 finally matured as the J-8II, the solid nose incorporating a radar powerful enough for BVR interceptions.
Still although the PLAAF (and especially AVIC 1) would like to pretend otherwise, the J-8 remains basically an interceptor, not a multi-role aircraft.
With the developement of the J-10 and J-11, the remaining J-8's in the PLAAF's and PLAN's inventory will probably be retired. Given the reluctance of the PLA in general to scrap equipment before it actually breaks down, that will be a long time coming.
Best Regards,
Dusky Lim
J-8's target was US and Russian bombers and focused on high speed and high altitude. It really sacrifies the performance in low and medium.Gollevainen said:
Although this is not a post for J-8, but may be the photo in the following link is interesting,
it is about Shengyang J-8 III with a shorter length and canard to improve the performance in low and medium. Someone has more info to this?
Deino said:Hu ... can anyone translate that page PLEASE !!!!!!
Very strange that it's not possible to copy anything from that text to translate it in by Babelfish !!
Cheers, Deino
If you want to copy the text, load that page in your browser, then click on view-source, and you can cut & paste the text from there.
However this is really not necessary, since you can put the URL in babelfish directly and translate the entire page:
1) Go to here:
2) Cut and paste this URL into "Translate a Web Page":
3) Use the pull-down menu under the URL field to select Chinese-simp to English, then click on "Translate" button.
IMO the article is mostly speculative.
Indianfighter
Junior Member
The resemblence between the J-8 and MiG-21 is not significant. As mentioned by Gollevainen, the J-8 has been built by observing the features of various aircraft of the 70s and it is a "poor man's aircraft".
It may be mentioned that the Azarakhsh jet of Iran has also been constructed using the same philosophy, although its resemblence is mostly towards the F-5.
The J-8-IIM has a thinner fuselage for the provision of higher speeds and also since instead of the inner perepheral intakes in the fuselage's front, for routing of the air to the engine, 2 external
intakes are provided with air, that is routed by the front of the fuselage. The front has been aerodynamically designed for this purpose.
The inclusion of 2 engines is also a major difference in comparison with the MiG-21.
The similarities between the MiG-21 and the F-8 are the shape of the tailed-delta-wings and the swept stabilator (the stabilizer and the elevators have been combined). This is also a characteristic of the MiG-29.
The tail-fins are also similar in shape and extent.
Schematic of the MiG-21 :
Source:
Schematic of the F-8 :
Source:
Regarding manoueverability of the J-8-IIM, the following may be of importance:
By using the new, powerful WP-13B engines, the Jian-8IIM fighter boasts greatly improved low-altitude maneuverability, which is slightly better than that of the F-18 and Mirage 2000-5, but still inferior to that of the F-16. The Jian-8IIM fighter will probably be equipped with Russia's or China's helmet sight and advanced PL-9 and P-73 missiles, with which it will outperform the F-16C in close-range air combat.
Consequently, although their combat capabilities are similar, the Jian-8IIM is much cheaper than the F-16C.
Source:
Thus, the J-8 is indeed an interesting development by China in the 1970s. This was followed by the J-8-II which was more advanced than the earlier version and has higher manoueverability.
To date I have not been able to comprehend the reasons for the development of the FC-1. It was a project undertaken only by a rival manufacturer.
Like the J-8 IIM, the JF-17 has the same weapons-load capacity, has even lesser speed (Mach 2.2 vs Mach 1.7), very little composites, has minimal Fly-by-wire, has similar range and has equivalent manoueverability.
It may be mentioned that the Azarakhsh jet of Iran has also been constructed using the same philosophy, although its resemblence is mostly towards the F-5.
The J-8-IIM has a thinner fuselage for the provision of higher speeds and also since instead of the inner perepheral intakes in the fuselage's front, for routing of the air to the engine, 2 external
intakes are provided with air, that is routed by the front of the fuselage. The front has been aerodynamically designed for this purpose.
The inclusion of 2 engines is also a major difference in comparison with the MiG-21.
The similarities between the MiG-21 and the F-8 are the shape of the tailed-delta-wings and the swept stabilator (the stabilizer and the elevators have been combined). This is also a characteristic of the MiG-29.
The tail-fins are also similar in shape and extent.
Schematic of the MiG-21 :
Source:
Schematic of the F-8 :
Source:
Regarding manoueverability of the J-8-IIM, the following may be of importance:
By using the new, powerful WP-13B engines, the Jian-8IIM fighter boasts greatly improved low-altitude maneuverability, which is slightly better than that of the F-18 and Mirage 2000-5, but still inferior to that of the F-16. The Jian-8IIM fighter will probably be equipped with Russia's or China's helmet sight and advanced PL-9 and P-73 missiles, with which it will outperform the F-16C in close-range air combat.
Consequently, although their combat capabilities are similar, the Jian-8IIM is much cheaper than the F-16C.
Source:
Thus, the J-8 is indeed an interesting development by China in the 1970s. This was followed by the J-8-II which was more advanced than the earlier version and has higher manoueverability.
To date I have not been able to comprehend the reasons for the development of the FC-1. It was a project undertaken only by a rival manufacturer.
Like the J-8 IIM, the JF-17 has the same weapons-load capacity, has even lesser speed (Mach 2.2 vs Mach 1.7), very little composites, has minimal Fly-by-wire, has similar range and has equivalent manoueverability.
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are you sure about the maneuverability part being the same as j-8?? Well, i haven't seen the satistics so i dun know, but give the size and shape, i always thought, it should be close to j-7e in maneuverability.
not questioning your statement (this is the part that i dun get) If j-8 is cheaper that jf-17, would there be a reason for its development,except for pakistan involvement?
not questioning your statement (this is the part that i dun get) If j-8 is cheaper that jf-17, would there be a reason for its development,except for pakistan involvement?
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cabbageman
New Member
Of course China has its own design ability, the question is if it’s any good.
Don’t use FAS to judge fighter maneuverability, it is not reliable on non-US weapons. New engines usually increase thrust, but you have to look at the weight gained and other redesigns that came with engine replacement. F/A-18 also had engines changed from F-404-GE-400 to F404-GE-402 EPE, but that doesn’t tell you anything by itself. FAS offered no evidences and no sources whatsoever for saying J-8II is better than F/A-18 or Mirage-2000. At low-altitude, the speed is much lower. Guess what a naval aircraft like F/A-18 is known for.
Dogfight is also more than HMS and high offboresight AAM. Even if J-8 has HMS/PL-9, I would still choose F-16 or J-10 over it.
Don’t use FAS to judge fighter maneuverability, it is not reliable on non-US weapons. New engines usually increase thrust, but you have to look at the weight gained and other redesigns that came with engine replacement. F/A-18 also had engines changed from F-404-GE-400 to F404-GE-402 EPE, but that doesn’t tell you anything by itself. FAS offered no evidences and no sources whatsoever for saying J-8II is better than F/A-18 or Mirage-2000. At low-altitude, the speed is much lower. Guess what a naval aircraft like F/A-18 is known for.
Dogfight is also more than HMS and high offboresight AAM. Even if J-8 has HMS/PL-9, I would still choose F-16 or J-10 over it.
Indianfighter
Junior Member
The statements about the comparison of the manoueverability of the J-8 with the F-16C and F-18 have been taken from FAS.org, whose link has been provided by me.ahho said:
I agree with the above statement. As mentioned by me earlier, the reasons for developing the FC-1 are not clear to me also, since it has overall inferior parameters as compared to the J-8.
I have also read that the FC-1 project was close to being abandoned by China in 1995, but for Pakistan's insistence on its revival.
The prototype of the J-8IIM first flew in 1996. The following statements are from globalsecurity.org :-
"The high-altitude high-speed performance of the Jian-8IIM is superior to the F-16A/C, F-18, and Mirage 2000; and its radar and electronic equipment are better than those of the F-16A and are similar to those of F-16C, F-18,and Mirage 2000-5. By using the new, powerful WP-13B engines, the Jian-8IIM fighter boasts greatly improved low-altitude maneuverability, which is slightly better than that of the F-18 and Mirage 2000-5, but still inferior to that of the F-16."
The most plausible reason for the development of the FC-1 was the insistence of Pakistan. The agreement for its joint development was reached only in 1999, which is very recent.
Since it was developed from conception to prototype stage in just 4 years, it is likely to have been based upon an existing design (speculated to be Project 33 of Mikoyan).
The following may be another reason for the cancellation of the upgrade of the avionics of the J-8II :-
"The newer J-8 family, an interesting blend of MiG-19 and MiG-21 technology, was to have been fitted with a sophisticated suite of Grumman integrated avionics. This program collapsed after the Chinese government crushed students under tank treads in 1989. The West's withdrawal from an increasingly hostile China has created an opportunity for the Russians, who are reported to have up to 5,000 technical support staff in the country."
Source:
It is my speculation that the FC-1 will be inducted in small numbers in the PLAAF, since its main purpose would be as an export commodity.
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MiG-21 was also designed as a high speed interceptor. When the MiG-21 was being designed, there was already a fundamental shift in airpower from the basic concept of air superiority through fighter vs. fighter engagment to the priority of intercepting high altitude nuke armed bombers. The MiG-21 just didn't let go of its dogfighter roots as quick as other interceptor designs did. One can say that the sixties was the golden age of interceptors---every design one way or another had to intercept bombers.
When you have an acute sweep delta like the MiG-21 or J-8 has, the moment these wings start getting into a turn and gaining more alpha, drag becomes higher than a sweep wing, and plane quickly bleeds speed. In a way its actually regressed in maneuverability compared to the MiG-19, which not only has a higher TWR than the Fishbed, but keeps more of its energy better in a turn. And so, an entire generation of aircraft was developed (F-4 Phantom, Mirage III, MiG-21) that turned out wasn't any better than its predecessors in WVR combat, but even inferior in some aspect.
What turned this around was the F-16. It wasn't just the Boyd theory, or the high thrust to weight ratio, or the FBW. Its main aerodynamic feature was the LERXes that force vortex generation across the wings at angle of attack. These vortices renenergize the air stream over the wings, which goes on to stabilize the wing at high alpha and reduce energy bleed. The FBW goes further to make sure no matter how much the stick is pulled back, the angle of attack would never reach to the point where the wings would generate more drag than lift, and the plane bleeds both speed and altitude.
The MiG-29 has LERXes so the Russians understood the first part of this lesson. But it would take the Su-27 before the Russians complete the second part. The Chinese certainly understood this concept of vortice generation but went about it in another way. This was how the double delta wing for the J-7E was developed. But to take it beyond double delta and LERXes, you would need a variable and controllable surface that would serve as the vortice generator. And this led to the canard, and to the J-10.
Among the high speed interceptors, I would put the J-8II fitting in the niche between a super heavy weight like the MiG-25, and the light and lithe like the F-104 Starfighter.
I don't see the point between the FC-1 being compared to the J-8II. The FC-1 was designed as a much more maneuverable plane, better in low altitudes, while the J-8II was a strictly high speed, high sky fighter. I believe the J-8II using the WP-13B or WP-14 Kunlun engines will have a higher thrust to weight ratio, but it will only be like 10% or so.
When you have an acute sweep delta like the MiG-21 or J-8 has, the moment these wings start getting into a turn and gaining more alpha, drag becomes higher than a sweep wing, and plane quickly bleeds speed. In a way its actually regressed in maneuverability compared to the MiG-19, which not only has a higher TWR than the Fishbed, but keeps more of its energy better in a turn. And so, an entire generation of aircraft was developed (F-4 Phantom, Mirage III, MiG-21) that turned out wasn't any better than its predecessors in WVR combat, but even inferior in some aspect.
What turned this around was the F-16. It wasn't just the Boyd theory, or the high thrust to weight ratio, or the FBW. Its main aerodynamic feature was the LERXes that force vortex generation across the wings at angle of attack. These vortices renenergize the air stream over the wings, which goes on to stabilize the wing at high alpha and reduce energy bleed. The FBW goes further to make sure no matter how much the stick is pulled back, the angle of attack would never reach to the point where the wings would generate more drag than lift, and the plane bleeds both speed and altitude.
The MiG-29 has LERXes so the Russians understood the first part of this lesson. But it would take the Su-27 before the Russians complete the second part. The Chinese certainly understood this concept of vortice generation but went about it in another way. This was how the double delta wing for the J-7E was developed. But to take it beyond double delta and LERXes, you would need a variable and controllable surface that would serve as the vortice generator. And this led to the canard, and to the J-10.
Among the high speed interceptors, I would put the J-8II fitting in the niche between a super heavy weight like the MiG-25, and the light and lithe like the F-104 Starfighter.
I don't see the point between the FC-1 being compared to the J-8II. The FC-1 was designed as a much more maneuverable plane, better in low altitudes, while the J-8II was a strictly high speed, high sky fighter. I believe the J-8II using the WP-13B or WP-14 Kunlun engines will have a higher thrust to weight ratio, but it will only be like 10% or so.