Both were/are interceptors with little agility compared to the standard of the 70s.
Big enough to carry a usefull radar for that task and the bigger AAMs related to that. The Su-15 was unable to cope with the growing weight demands of that and the performance specifications were lowered accordingly. The missions of the Su-15 could have been fullfilled by the later MiG-23s with ease as the MiG-23P did show. 😉

I would not say the J-8II can not beat an F-4E or even MiG-23ML, in my opinion if the J-8II would had been deployed in 1968 would had been an equal of the F-4 and MiG-23, but definitively when it was deployed the Japanese F-15 and Taiwanese F-16s were more than a match for it.
I think the J-8II in 1990 was as capable as the MiG-23M and F-4E of the early 1970s

The aft body design of the MiG-23 looks solid and state-of-the-art, while that of the J-8 looks like a big piece of disaster. If the copied, they obviously missed the mark.
Aft body design has very noticeable effect on transonic and supersonic drag.

Well the original Ye-150 and also the T-5 had empennages similar to the J-8I

and this was a 1960s early design trend copied by the chinese

The Su-15 was also similar in that sense

Which is quite a lot.

MiG-23 and Suchoi 15 were not designed on two different worlds. Both MiG and Sukhoi benefited from research done at TsAGI and other. MiG-23 and Sukhoi 15 are very comparable in used technology and overall performance criteria, apart from the swing wing for better take-off performance for the MiG. The differences grew when the MiG-23 became more like a fighter. The PVO finally operated MiG-23P and Su-15M alongside.

They have some relation but it is not direct.

You have to see the following designs to understand it, first let us see MiG

The Russians started doing what China did with the MiG-21, a twin engined MiG-21 AkA Ye-152A

later they thought a MiG-21 with nose radome and side inlets

Sukhoi was different

they started with the T-3

this was a solution for a bigger radar station

however they needed another design to house a bigger radar
so enters the T-49

at the same time like MiG they were studing a twin engined version of the Su-9 which became the T-5

the sukhoi T-58 married and refined both designs

See that both the T-5 and Ye-152 had R-11s

China did the same but blended the J-8I with the MiG-23MS and used the R-13s obtained from Egypt

source of the pictureshttp://www.airwar.ru/enc/xplane/t3.html

basicly the J-8II is a MiG-23PD with the side inlets and ventral fin of an operational and series MiG-23, using basicly a Ye-152A concept as base for it and without lift engines of course.

see

WP-13 is reverse engineered from the R-13. Not licensed. There is a difference. The WP-7 is licensed from the R-11. The Russians actually provided plans and a sample of the R-11 before the Sino-Soviet split. The WP-13 was developed a decade after the split, when the Chinese obtained MiG-21MF examples from Egypt after 1973. The planes had the R-13 engines.

The original J-8I flew with WP-7 engines, not WP-13.

the R-13 is basicly an upgraded R-11, so basicly the engines have common parts, the engines are not so much different from each other, so what the chinese copied was an upgraded R-11.
Главной его работой стал двигатель Р-13, являвшийся дальнейшим развитием турбореактивного двигателя Р-11.

The R-13-300 compared to the R-11 has a completely new afterburner chamber, five new high-pressure compressors and a new combustion chamber with a modified system start up launches at high altitudes without the use of additional fuel tank
В Р-13-300 по сравнению с Р-11 был установлена полностью новая форсажная камера, новый пятиступенчатый компрессор высокого давления и новая камера сгорания с модифицированной системой запуска обеспечивающей запуск на больших высотах без применения дополнительного топливного бака
http://www.airwar.ru/enc/engines/r13-300.html

The Original J-8I has R-11s

So as the Su-15 both aircraft have R-13s

climb rate: 　
（H=1KM，M=0.9）： 224m/s
（H=5KM，M=0.9）： 160m/s
sustained turn: 　
（H=1KM，M=0.9）： 6.9g
（H=5KM，M=0.9）： 4.7g
accelleration　
（H=1KM，M=0.7~1.00）： 21s
（H=5KM，M=0.6~1.25）： 55s

Who will post F-4 and Su-15?

According to what i know, the F-4E has a turn rate of around 13.7 deg/s at 1000 meters, but at sea level is 14.6 deg /s and at around 3000 meters or 10000 feet is 11 deg/s
It is said its rate of climb is 200 m/s and it will take it 22 sec to reach 1000 km/h from 600 km/h

The MiG-23ML will do a sustained turn of 14.1 deg/s at 1km of altitude, a max rate of climb of around 218 m/s and it will take to the MiG-23MLD 19.8 seconds to reach 1000km/h from 600km/h, for the MiG-23ML it will take 22 seconds to reach from 600km/h the speed of 1100km/h.

In fact the MiG-23ML has an excellent acceleration the MiG-23ML will only take 12 seconds to reach 900km/h from the starting speed of 600km/h and close to 15 seconds to 1000km/h more or less what an F-16 can do

Must admit when I made the original topic my thought was that the J-8II was largely old technology using semi-active missiles and an indigenous radar set. Looks like I should have done a little more research than none at all.

If you lighten up the load in your 7G turn then you still are exerting the same number of G’s on the airframe in a 7G turn. The overall force on the plane may change with its weight change, but a 7G turn is a 7G turn.

The Su-15 was the one that downed the Korean 747, flight 007. I think it may the one that downed another 747 years before that incident, but the plane was able to land on a frozen lake and the Soviets released the people involved when it was clear that flight was not a hostile intruder. Technically the latter plane was not shot down because the crew picked the landing location. Another incident involved a CL-44 in which the Su-15 clipped the wing and ended up taking himself out.

The J-8II was the plane involved with clipping an American EP-3 spyplane.

mad rat

G is a measure of acceleration and inertia and acceleration is related to force and mass, a lighter mass can be accelerated to higher speeds, a heavier aircraft with the same thrust can not achieve the same G loads.
heavier aircrat tension more the structural strength of the materials in an airframe.

Size and mass matter are important to achieve higher Gs

Example the MiG-23UB since it is heavier is also less capable than the MiG-23ML

Just how much can you strengthen something that is so long and so narrow? I have a feeling the long slender shape isn’t real conducive to high-G maneuvers by default.

Has anyone taken a long hard look at the J-8II and compared it structurally with the Su-15? I’ve just been skimming over pictures and find their resemblance from the intakes on back to the rudders too close to be by chance. Could Sukhoi have sold their flight data on the Flagon design to the Chinese to fast track the J-8II program? I’ve found plenty of examples on airliners.net and its just too coincidental. The tail caps are the same lines. The wing fences are identical placement. The wings themselves are exactly in the same places. The rivet lines look strikingly similar from about mid-wing back to the tail pipes. The tail is damn near identical. Even the access ports are too much alike. The cockpit, except for the extended spine that reaches tail to pit on the J-8II, is also identical. Surely Shenyang copied the later Su-15 design.

Well that is hard to tell, you have to go back to the 1960s when Russia was building the Ye-150A and the T-5, both aircraft are basicly very similar to the original J-8I, independently if you want or not link the Ye-150A to the J-8I, Shenyang followed a very similar design process to the T-5, T-58 and other Russian Su-15 ancestors.

Structurally, both aircraft are very similar, however the main difference may lie in new materials and new construction technics.

Why well the only thing they modified was the frontal part of the J-8I and the ventral fins, same did mikoyan with the MiG-23PD that basicly is a MiG-21.

However the J-8II has been an excellent design experiment by the Chinese, certainly the aircraft is obsolete and was even obsolete by the time it became operational, it was a late 1950s, early 1960s concept operational in 1990.

The reason is more capable than the Su-15 is simply the Russian did not upgrade the Su-15 with new missiles such as the AA-1０ and AA-11 or with new electronics and radars.

In reality the Su-15 is not as lumbering as it seems, but definetively it was not designed as a dogfighter.

The J-8II is not so agile, if you consider the MiG-23 was considered inferior to the F-15 even by the Russians and the F-4 was an easy pray of F-15s too, you can not consider the J-8II even in its current forms will be outstanding in 2008 specially since its numbers are slightly less impressive that those in the MiG-23 and F-4E.

http://www.masdf.com/eagle/f15/anapg63v301.jpg
I guess it has a sustained turn rate in the range of 14 deg/s or less and an instantaneous turn rate in the range of 16 deg/s

In 2008 an F-18E will shot down the J-8II easily and a fighter like the Gripen will certainly play with it before killing it.

The F-22 will simply shoot it down as if it was a fly

http://en.wikipedia.org/wiki/G-force

Start learning first. 😉

I think the one who should learn is you since the following is based upon relativity

Inertial mass and gravitational mass are one and the same phenomenon.
Inertial force and gravitational force are one and the same phenomenon

Each mass has different weight depending in the gravity force it exerts , a person weighs less in the moon than in the earth, in orbit his or her bones become bridle due to the lack of gravity ( in reality weightlessness is an incorrect term in orbit a person still weighs but since the gravity he or she exert is so small it is called close to 0, but in reality is not 0), if you go to a planet with higher mass you need stronger bones to remain standing but in the moon you are able to jump longer distances .

now since inertia equals gravity, higher g forces otherwise known as inertial force that a MiG-23 or any aircraft experiment makes them need also stronger materials as you need stronger bones in a planet with higher mass than the earth.
😉

In jupiter a person of 90kg on earth will weight 240kg but in mercury 34kg

Now remember that