Jian vs. Jian

J-7C/D vs. J-7E

For me, one of the most interesting events in the history of the PLAAF is the way they trashed the J-7C/D development after spending more than a decade developing it.

As you know, the project started when China acquired a few MiG-21MF from the Egyptians as part of a barter that also included MiG-23s. The Egyptians got some J-6s in return. The bonanza was the more powerful R-11-300 Tumansky engines.

The J-7C was developed from the third generation airframe the MiG-21MF exemplified. Basically, the history of the Fishbed can be summed into four generations:

1st --- MiG-21F and variants, the original
2nd --- MiG-21PF and variants (-PFM)
3rd --- MiG-21MF and variants
4th --- MiG-21bis

In theory, the J-7C, with the more advanced airframe from the 3rd generation is supposedly better than the J-7A and -B, which is based on the 1st generation. Right? Yet the J-7E which came quickly afterwards, reverted to the first generation airframe, and quickly enough, the J-7C and its "fixed" variant, the J-7D, only had two regiments and faded into obscurity.

In theory, supposedly, the later generation designs are better right? In practice, successful fighter designs tend to evolve with adding requirements. The result from that evolution is a heavier and beefier design, which can do better bombing a target. But the weight gains also made a fighter less agile, faced with increasing wing loads. The ME-109 faced this factor as it evolved from the Friedrichs to the Gustavs and Kurst versions.

As the Fishbed evolved and got beefed up, it also started packing more pork and weight while wing area remained the same. A more powerful engine helps lift the aircraft from the ground and maintain its speed on turns, but it does not make the plane more agile, or helped its low speed handling. A more powerful engine is no substitute for wing loading. The plane would have higher take off and landing speeds. In turns, it would reach a stall point from a higher speed. Overall, not only is the plane less agile, it is a bit more dangerous to fly.

While the rest of the world seemed okay with the 3rd and 4th Fishbed generation, it wasn't okay with the PLAAF pilots. Did the PLAAF make a better choice?

The reason for the 3rd and 4th generation Fishbeds is that one of the rationales for their entire design is based on accomodating a bigger radar. You could probably live with the handling penalties of the type if the advantages of having a better radar would offset this. But my guess is that the problems and capabilities of the J-7C/D radar didn't offset this well enough, combined with the PLAAF pilots have become accustomed to a culture where radar use is ignored and not trusted. Back to the dogfight only culture, they return.

I would probably regard as the first and second generation Fishbeds as the ones best to fly, with the least 'pork' on them. The first generation, after all, is the original vision of the plane. Sometimes, losing that vision may not be good, and it is often good to go return to one's roots.

Thus I think that is why the next variant of the J-7 went back to its roots.

But there was more to that too---a brand new wing design---which marks the first fundamental new addition to the Fishbed design since the -bis.

What makes this new double delta wing design a leap compared to the classic delta wing?

The break in the wing from a sharp inclination to a lesser sweep, would cause the air from leaking spanwise at the front edge of the wing, and force the flow to go over and under the wing, improving lift. Vortices from the break aid in control at higher angles of attack. In addition, the new wing has about 25% more wing area from the classic wing while retaining the light weight of the -F class, though slightly heavier now to endure 8G turns (the Fishbed is generally a 7 to 7.5G fighter). Add to that is an extra wing span and higher wing aspect ratio, all combining to give a better lift at lower speeds. To top everything off, the wing now has a Fishbed first---adjustable variable wing camber at the front edge of the wings, improving the efficiency of lift. The new wings also allow for more fuel to be stored in the wings.

The J-7E then adds the more powerful engine from the J-7D to the lighter J-7B type airframe, a classic hot rod formula akin to using the engine of the MiG-21MF to their original -21F airframe. Toping all that is the radar developed from the J-7D which enables use of the all aspect PL-8.

Though late, in my opinion, the PLAAF finally got the J-7 it wanted with the J-7E. The plane in my opinion, is probably the best dogfighting Fishbed to date, and its surprising performance, even against Su-27s, probably led to the continued production of the type. The type went on to become popular with the PLAAF, though a tight budget squeezed by Su-27 and J-8II purchases, and production capacity diverted to export the airframe as the F-7PG prevented all the PLAAF regiments that wanted it from getting the plane. At best there are probably just over 300 maybe 400 optimistically, of the J-7E and the improved -G type, not much considering all the Flankers and J-8II out there.

The J-7G is basically the PLAAF version of the F-7MG export variant of the J-7E. The main changes is the one piece windshield, MFDs in the cockpit, and a new slotted array KL-6E radar replacing the old Type 226. How many Chengdu will build, one wonders, as the type came in a bit too late given the J-10 and J-11 company it has to live with.

But in my opinion, the J-7E/G makes a great ACM training fighter. It's not something one should like to go to war with, without proper BVR, it is facing an immense disadvantage. But in peacetime, it can be used to train pilots for WVR air combat without the expense of a J-11 or J-10, especially for units without the most advanced plane types, for adversary units, and for pilots who need to increase their flight hours while their main aircraft is at maintenance.

As for the fate of the J-7C/D, it never got past over two regiments, though both are assigned to the "elite" 29th Division guarding the Nanjing area, where they serve as all weather interceptors. I wonder if they are still there, as one of the 29th Division regiments have upgraded to the Su-30MKK.

It seemed though, while they are newer than the quite similar J-8I, their fate in obscurity seemed even worst than the J-8I which at least populated two divisions.

Ironically, CAC has been looking to "BVR" the J-7 with designs like the J-7FS, why didn't it just take a look at the J-7D once again, given that India did quite well using the same airframe design on the Bison. Give it a decent radar and PL-12 capability. But I guess the proper time for such ideas have long passed.

darth sidious said:

J-6 surived only because the chinese failed to produce effective radar/missile

if you want to talk about short endurance I can assure you the J-6 has to consider where to land literaly withen minutes after take off with after burner

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Same thing happens on the J-7 too.

J-6 is not invincible in dog fight either the view from the cokpit is horrible with the ejection seat placed low

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Not much different from the J-7 or MiG-21MF either, and those planes have a spine that affects their back view. Actually the J-10 even has a low ejection seat relative to the Lavi or F-16.

the poor Rd-9 engine wastes more fuel and lacks the power of the 13 the chinese should have given up on such a design long ago

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But there were two of them for combined thrust. They were also easier to manufacture and replace than the WP-7. WP-31FII might have 66Kn; each WP-6A has a thrust of 39Kn.

mig-21 will not be flying in such a formation as longer as it retine the speed/altiude advantage( not hard for the mig-21 to do) the J-6 will always be on the losing end

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I can't really see the speed and altitude advantage of the MiG-21.

the Q series weere design ed in the late 50s when no J-7/98 knoldge where avilible

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It's actually designed in the sixties, not withstanding conceptual designs which I don't consider real serious work. By the seventies to the eighties, China has all the time to consider other Q platform alternatives, such as using the J-7 or J-8 platforms.

work on the Q-5 begin in 1958 by 1962 the work is mostly finished the production is only delayed becaused of political struggle / stortage of supply
chinese programe to copy the Mig-21 did not work until the mid 60s due to difficulty with the ejection system and r-13 engine.

Plan also dident mass produce the PL-2 until the late 70s

the J-7 has a higher operational ceiling/speed rate Plus good agility this ensure they are atlest equal in dog fight saved for lower altitudes ( problem with r-13 engine)

Most combat takes place well under transonic speed. Thus having Mach 2 is of no advantage for the J-7, which does not have the fuel to reach it either. Unless you are in bomber interception, low altitudes is where many commonly engage in visual air combat because long range radar does not work well at low altitudes, making detection more difficult.

As for the missiles, the MiG-21F type always had a cannon, unlike the -PF type. So it could always fight at gun range. Besides missiles suck in the sixties in general so it does not matter much if you have a missile or not.

I agreed that J7/J8 may not have clearly advantages over J6, but I still think J7 is better than J6 in many aspects.

The mass production of J6 are more to do with the situations in 60. China needed quantity to fight with quality, and the gad between China and the western were not as much as when J7 were introducted. When J7 were ready to produce, the gad had widen. So it did not made sense for J7 to produce in mass quantity, since J7 did not had much improvement than J6.
But that did not mean J7 were not better than J6.

1. J7 may not acheive full March 2 in the interceptor, but J7 still have speed advantage over J6. When J7 is in the defensive role, J7 will do much better than J6.
2. J7 had better design platform, since they already acknowlege the need of radar and missles. The only problem is they never develop a good radar and missles until eighty, but it really had to do with political situation.
3. J6 had only little modification left, you really could not install any modern radar or missles. So sooner or later J6 will dead out, the only reason J6 continued to produce is early J7 suck.

If China did not had Cultural Revolution, I would whether think J7 modification will move 7/8 years ahead. So J7 will replace all the production of J6.

KYli said:

I agreed that J7/J8 may not have clearly advantages over J6, but I still think J7 is better than J6 in many aspects.

The mass production of J6 are more to do with the situations in 60.

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It had nothing to do with that really, despite the J-6 and J-5 being the only available types to China in the sixties. The bulk of J-6 production occured in the seventies right up to the late eighties and by then the J-7 was already available.

China needed quantity to fight with quality, and the gad between China and the western were not as much as when J7 were introducted. When J7 were ready to produce, the gad had widen. So it did not made sense for J7 to produce in mass quantity, since J7 did not had much improvement than J6.
But that did not mean J7 were not better than J6.

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Which is true. The J-7 is easier to fly and maintain, but the maneuverability advantages is not so apparent. Actually a J-7 or J-6 will also have a hard time fighting a crack pilot on a J-5 (MiG-17).

1. J7 may not acheive full March 2 in the interceptor, but J7 still have speed advantage over J6. When J7 is in the defensive role, J7 will do much better than J6.

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The speed advantages is not so apparent. The J-6 has greater power and it accelerates faster. You can see this when a J-6 manages to shoot down an RF-104, which is a reconnaissasnce Starfighter during the sixties. The Starfighter has a great reputation for speed. In Afghanistan, it has also taken down a MiG-23, which is another fast plane.

2. J7 had better design platform, since they already acknowlege the need of radar and missles. The only problem is they never develop a good radar and missles until eighty, but it really had to do with political situation.
3. J6 had only little modification left, you really could not install any modern radar or missles. So sooner or later J6 will dead out, the only reason J6 continued to produce is early J7 suck.

If China did not had Cultural Revolution, I would whether think J7 modification will move 7/8 years ahead. So J7 will replace all the production of J6.

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crobato said:

It had nothing to do with that really, despite the J-6 and J-5 being the only available types to China in the sixties. The bulk of J-6 production occured in the seventies right up to the late eighties and by then the J-7 was already available.

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Well, I think it had to do with the political situation because the tie between China and Russia deteriate greatly in 60, and China had left with no major allied anymore. Without asistance from Russia, chinese engineers had difficult time to develop their own concept. Since China did not have formal relationship with western countries, no technology asistance was available. China was left alone, and surround by many hostile enemies. So China needed to use quantity against quality to fill up the gad. By the time the J7 come along, J7 did not proved it superior with J6. So China had no choice, but continued to produce J6. If China could solved the radar and missles problem early, J6 will have stop by early eighties or even earlier. If the political situation was not that unstable, China will not produce that many J6 also.

crabato said:

Which is true. The J-7 is easier to fly and maintain, but the maneuverability advantages is not so apparent. Actually a J-7 or J-6 will also have a hard time fighting a crack pilot on a J-5 (MiG-17).

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I agreed, but J7 do have some maneuverability advantages against j6, everthrough it might be not that obvious.

crabato said:

The speed advantages is not so apparent. The J-6 has greater power and it accelerates faster. You can see this when a J-6 manages to shoot down an RF-104, which is a reconnaissasnce Starfighter during the sixties. The Starfighter has a great reputation for speed. In Afghanistan, it has also taken down a MiG-23, which is another fast plane.

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The J6 manages to shoot down RF-104 and MIG23, but that could only proves J6 could beat planes are consider faster. It does not mean J6 has better speed and accelerates than f-104. If my memory is correct, eventhrough F-104 might has better speed and climbing than J7(J7 do have better agilty advantage and easy to mantain), but Mig21 did managed to shoot down few f-104 also. So it only proves that speed and accelerate is not decisive in battle, but it did not mean J6 has better speed and the accelerates J7 has. F-104 or F7 do not have clearly advantages than J6, but they do have better speed advantage. (J6 may have better accelerates).

The speed advantages is not apparent because every combat takes place well under the sound barrier. It's also true that the MiG-21 is faster than the F-18 Hornet, but the Hornet---like many newer planes---no longer put a premium on speed. Why? Because the lesson is learned---combat is indeed almost always fought well under the sound barrier. Acceleration is more important actually in any dogfight, as you need to regain energy, and the J-6's greater thrust is an advantage here, except on late model J-7s like the J-7E.

There is this story and it seems true because there is a unit and its commander involved. I forgot the name of the person, but he is the commander of the Blue Flag aggressor regiment in the FTTC.

The unit was using J-7Es, and one day, the commander heard that the unit was to be reassigned with J-11s. Naturally, as the Blue Flag unit that is used to test against other regiments, they must have the best planes. The commander objected and insisted he stick with the J-7Es. Asked why, and he laid a bet.

He requested to his superiors to get three pilot and planes from the most experienced Su-27 regiment in the PLAAF. They will decide the altitude of the engagement. If he can "shot" down all three of them, his unit gets to keep their beloved J-7Es. If he loses, he will agree to the conversion to J-11s.

So that day, the day came, there were the three Su-27s and he went up and "shot" all of them down. His unit got to keep their J-7Es.

crobato said:

The speed advantages is not apparent because every combat takes place well under the sound barrier. It's also true that the MiG-21 is faster than the F-18 Hornet, but the Hornet---like many newer planes---no longer put a premium on speed. Why? Because the lesson is learned---combat is indeed almost always fought well under the sound barrier. Acceleration is more important actually in any dogfight, as you need to regain energy, and the J-6's greater thrust is an advantage here, except on late model J-7s like the J-7E.

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I agreed. That why J8 platfrom was outdate before it went into service, high altitude and high speed are not important in dogfight, and could easily brought down by ground fire. what I am saying is that higher speed is still advantage, but about J6 has better acceleration done to their two engines. So J6 is better in dogfight than J7, I will agree with some extend. But I think what make J6 good in dogfight, is J6 has excellent CI and wing loading. Since angle of attack is one of the most important factor of dogfighter.

I still think J7 has some advantages than J6.

J6 is a difficult to mantain fighter. The engines have very short life, and not easy to fly. The pilot will be difficult to master it, so you need more time to train them. Eventhrough J7 do have problems as difficult to land because of the speed, J7 is still easier to fly.

About the speed, when J6 was bounced by J7. The J6 would be hard to outrun the J7. The J7 has more internal fuel(I am not too sure about this one).

The J7 is better interceptor than J6, it is better in transonic and supersonic speed. And that is very important for attacking high speed and high flying targets.

J6 was draggier than the J7, So when you take into thrust/drag consideration, the J7 is better above March .8. Well I would give J6 some advantage in dogfight done to J6 should fare better under March .8 with T/w ratio. I would say acceleration in speed is important, but far for decisive in dogfight.

J7 has radar and missiles advantages, eventhrough they are pretty much useles, but still a plus.