After the J-6 was put into mass production and delivered to the military services, another supersonic fighter, the J-7 with M 2.0 maximum speed was manufactured based on the Soviet MiG-21. The Chinese began development of the J-7, based on incomplete technical data of the Soviet MiG-21F, in the 1960s. License production of the J-7 was carried out by the Shenyang Aircraft Factory starting in 1964.
The J-7 design consisted of a delta wing and an all- movable horizontal tail surface. The J-7 could reach Mach 2.05, had a service ceiling 17,500 m, and a maximum range 1,530 km. The J-7 in comparison to the J-7 was comparatively easier to control, had a faster climb-rate, and had performed better in transonic and supersonic situations. The J-7 also had superior armaments and flight characteristics.
The J-7 aircraft was equipped with the WP7 engine. Its maximum thrust was 50% more powerful than the WP6 and was 77% more powerful in its afterburner thrust. The WP7 engine also had twice the service life of the WP6. The WP7 engines twin-spool, axial-flow turbojet engine was more advanced in production, and complicated to manufacture.
The license production of the WP7 engine was carried out by the Shenyang Engine Factory in 1963. Production of the WP7 engine was not without problems, as the turbine blades of the engine suffered a rejection rate of up to 50% due to the poor quality of the its imported ingot material. This technical problem was solved after Ministry of Aviation Industry, Ministry of Metallurgy, and the Chinese Academy of Sciences developed a higher quality alloy for the turbine blades. By October 1965, the first WP7 engine was successfully tested and was certified in December 1966.
A successful static test of the J-7's airframe was carried out in November 1965. Flight tests for the J-7 began in January 1966 and was certified for use by the Chinese military in June 1967. On January 17, 1966 the J-7 piloted by, pilot Ge Wenrong flew for the first time and 12 sorties and 29 takeoffs had been flown by the end of April. The J-7 was good in stability and controllability. All systems operated normally. The maximum speed reached M 2.02. The main tactical and technical performance conformed to the operational requirement. The J-7 was certificated for production in June, 1967. The prototype production of the J-7 took only 2 years and 4 months, one year ahead of the original plan.
A couple of major problems in manufacturing techniques were solved one after another by the engineers during the prototype production of the J-7, such as the forming of titanium alloy parts, the Chemical milling of integral panels, manufacture of an integral radome, assembly of an integral fuel tank and manufacture of non-metallic honeycomb cone.
In 1964 and 1965 the Government decided to transfer J-7 production to the Chengdu Aircraft Factory and the newly-established Guizhou Aircraft Production Base with the support of the Shenyang Aircraft Factory. Therefore, three aircraft factories were constructing the J-7 at the same time.
In 1968 the US Central Intelligence Agency noted that "We have been expecting the Chinese to begin turning out Mig-21s for about two years, but they still have not started production. An airframe plant and an aircraft engine plant in Chengtu in Szechwan Province have been the prime candidates for producing Mig-21s. Although the Chinese are clearly concerned with improving their air defense and the Mig-21 would make a significant contribution to their effort, they may have encountered difficulties. Mig-21 engine technology, for example, is considerably more difficult than that for the Mig-19. Or production may have been delayed for economic or other reasons. It appears to us the Chinese have two options: to try to produce the Mig-21 or to develop a fighter essentially of their own design. Of the two, producing the Mig-21 is probably the less difficult and more rapid route. Thus we believe that there is still an even chance that they will produce the Mig-21. If the Chinese do not intend to produce this aircraft, it would be at least four or five years before a fighter significantly more advanced than the Mig-19 could be available."
In June 1970 the US Central Intelligence Agency stated that " ... we are increasingly uncertain about Chinese plans for producing the Mig-21, but note that the Cbblese have had eight years now to study, copy, or make design modifications to the Mig-2ls given them by the Soviets. It would appear, therefore, that the Chinese either have experienced great difficulties in reproducing this aircraft (which appears to be the most likely case) or that they have decided to bypass the Mig-21 in the hopes of developing a more advanced interceptor of their own design. If the latter is the case, such an aircraft probably would not be available in quantity for at least five years."
The J-7 was superior to the J-6 is overall performance. However, the J-7 was plagued by flaws such as its short search distance, its poor short range firepower, a low fuel capacity, and lengthy acceleration.
Increasing operational needs necessitated the development of J-7 variants, which were developed in Shenyang, Chengdu and Guizhou. The J-7 series aircraft are rather successful among all the derivative fighters. A number of versions with different features and applications have been derived step by step from a single basic aircraft. This achievement is a natural result of the fact that the scientific people have mastered the laws and peculiarity of the modifications to a basic aircraft through their enormous practice and exploration. The laws and peculiarity of the aircraft modification and derivation can be concluded as follows:
The aircraft modification and derivation is different both from the license production in that the partial development is incorporated and the development of a new aircraft in that only partial innovation is incorporated. The peculiarity of the aircraft modification and derivation determine that the designers have to first have a thorough understanding of the basic aircraft design and of aircraft structures and systems then find out the weak points of the basic aircraft by analyzing the operators' inputs while investigating the objectives of the modification and derivation and at last determine the new technology to be used.
The technology to be used for the modification has to be tested and proven by a number of ground tests and flight test. Therefore, the infrastructure and the test team must be expanded and strengthened from time to time to ensure the smooth carrying out of the tests.
The retrofitting of an aircraft must be accompanied by the synchronized development, certification and problem solving in other related areas, e.g. engine and airborne equipment, otherwise any delay or failure in these related areas will adversely affect the whole retrofitting program.
With the renewal of Chinese fighters further modification' and derivation based on an advanced existing fighter were carried out. Other development efforts extended through the F-7M Airguard which received a production go-ahead in December 1984. In 1988 China delivered the first 20 of 60 F-7M Skybolts to Pakistan. As upgrades, Karachi was leaning to a totally indigenous Chinese aircraft over the Grumman-influenced Sabre II, or F-7P. Development of the "Super 7" upgrade was terminated with the end of American technical assistance following the Tienanmen repression of 1989. The J-7FS modification added a radar to a reconfigured air intake, while the "Super 7" upgrade would have completely reworked the front end of the aircraft, adding a much larger radar and ventral air inlets, along with various other less pronounced improvements.
In 1989, the Super-7 fighter project was halted due to United States' dissatisfaction with the China's repression of democratic movements within the country. However, in 1990 and 1991, the Chinese began negotiating to resume work with manufacturers of aircraft engines from Britain and the USSR. Although these discussions failed, the Chinese decided to embark on a radical modernization of the J-7.
The most important difference of the new version that received the designation J-7E is its double-wing swept at the leading edge, inside of which was placed additional fuel tanks. Despite increasing fuel capacity by half, flying characteristics were not affected. The J-7E is equipped with the WP-13F engine with thrust 63.73 kN. The plane has a full suite of avionics, including the pulse-doppler radar, which apparently is a copy of the Super Skyranger Radar. The J-7E prototype flew in May 1990, and the Chinese Air Force mass-produced vehicles began in 1995. According to pilots, the aircraft has capabilities comparable with the first F-16A modifications.
Amazingly, the J-7G Fishbed, the latest derivative of the MiG-21, remains in production, with as many as 96 were in PLAAF service by the end of 2010. In the USSR this aircraft was manufactured between the late 1950s and the middle 1970s. Production of the American F-4 Phantom II, the MiG-21's long-time adversary in Vietnam and the Middle East, ended in 1979, and the last Phantom was withdrawn from service in the United States in 1996.