J-7 (Jian-7 Fighter aircraft 7) / F-7
I In the 1960s, the Chinese began development of the J-7, which was based on incomplete technical data of the Soviet MiG-21F. License production of the J-7 was carried out by the Shenyang Aircraft Factory 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.
A successful static test of the J-7's airframe was carried out in November 1965.
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.
Flight tests for the J-7 began in January 1966 and was certified for use by the Chinese military in June 1967.
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.
Variants
Increasing operational needs necessitated the development of J-7 variants, which were developed in Shenyang , Chengdu and Guizhou .
The J-7 I and J-7II
The Chengdu Aircraft Factory modified the J-7 from 1969 to 1975, in which it added a cannon, changed the inlet cone from a 3-stage adjustment process to a continuous adjustment, and modified the inlet lip. As a result, the J-7's short range firepower was improved, supersonic acceleration was increased, takeoff thrust was increased. Overall, the J-7's performance was vastly improved.
Four additional important improvements were carried out after 1977.
First, the ejection escape system was modified. The first ejection escape system had the canopy automatically engaged to the seat at the beginning of ejection and later separated after ejection. This system was replaced by an open ejection escape system, which encompassed a new rocket ejection seat and new features in its maintenance, convenience, safety and reliability. Over 300 ejection tests both on the ground and air demonstrated improved ejection capabilities at zero altitude and low-speed conditions (250-850 km/h IAS). The new rocket ejection system worked successively in six real ejections from 1980 to 1985.
The second improvement involved the replacement of the WP7 with the WP7B. The WP7B improved and the thrust-to-weight ratio of the aircraft and the aircraft's overall performance. The WP7B had 12.8% higher thrust and 70% more afterburner thrust.
The third improvement was a 720 liter auxiliary fuel tank instead of the previous 480 liter for increased fuel capacity and extended range.
The fourth improvement was a raised drag chute bay that deploy the drag chute at a higher landing speed for increased landing performance. The aircraft was able to deploy its drag chute less than one meter above ground a reducing the landing to less than 800 m.
These improvements resulted in the J-7II. which made its maiden flight in December 1978. Its design was certified in September 1979.
The J-7M
Carried out by the Chengdu Aircraft Factory, the J‑7M was an improvement of the J-7II in which seven foreign items were incorporated into the avionics of the J-7. Eight domestic improvements were also made. New advances included a heads‑up display, improved accuracy, and a better firing and attack capabilities. The airborne radar had increased range with anti‑countermeasure capabilities. The communication equipment was improved and . The performance of the ejection escape system was improved at zero‑altitude situations and could be used at lower speeds an (130‑850 km/h IAS). The aircraft could be fitted with short-range air-to-air missiles for improved dogfighting capabilities. Trial tests of the J-7M began in August 1983. and was certified
in November 1984. China began the J-7M’s export 1985.
The J-7III
The J-7III is a medium-to-high altitude, high speed and all‑weather, day and night fighter. The J-7III improved upon the J-7II in that it was equipped with an all‑weather radar, had increased external storage, adopted a fixed windshield and side-hinging canopy, had a rear view mirror, more fuel tanks underneath the dorsal fairing, and an enlarged vertical fin. The J-7III was also equipped with the new WP13 engine.
Design Institute No.611 was redesigned the new J-7 variant. Production responsibilities were shared by the Chengdu Aircraft Company and the Guizhou Aircraft Company. The Chengdu Aircraft Company produced the J-7III’s fuselage and was responsible for its flight testing and adjustment. The Guizhou Aircraft company was responsible for the aircraft’s wings and the landing gear.
The J-7III was developed via a computer aided design system at Design Institute No.611 in 1981. Production of the aircraft began in 1982 by both the Chengdu Aircraft Company and Guizhou Aircraft Company. Static testing of the airframe was completed in April 1984.
Guizhou Engine Company and the Chengdu Engine Company co-developed the WP13 engine. The WP13 engine had good structural integrity. The engine also had a surge margin that was substantially increased after an improved compressor was used. The compressor case’s weight was decreased after replacing its material with titanium. The engine’s operational stability and reliability of was increased. The WP13’s service e life was lengthen after the addition of a metal chip detector to the engine’s oil system. Development of the WP13 was begun in 1978. Ten prototypes were constructed by 1984. The engine passed its certification tests the ext year in 1985. The J-7M’s design was certified and adopted in 1988, giving the J-7 family an aircraft with all-weather capabilities.
The JJ-7
Various versions of the J-7 and the export of the J-7 to foreign customers prompted the Chinese military to develop a trainer version of the J-7.. As a result, the Guizhou Aircraft Design Institute and the Guizhou Aircraft Company jointly began developing the trainer version of the J-7, which was designated as the JJ-7.
Based on the J-7II, the JJ-7 is a supersonic fighter‑trainer and primarily used for the training programs of the J-7 and J-7 II, and the J-7M.
Improvements and additions of JJ-7 consist of an aft cockpit, a new forward view periscope, twin ventral fins, fuel tanks inside the top fuselage, modified intake, improvements in the ejection escape system, air conditioning, a new fuel system, red cockpit lighting, an interphone system, and a failure simulation system. The conceptual design was started in 1979, and was completed in 1983. Trial production also began that same year. Static testing of airframe carried out and finished in May 1985. Fight testing began in 1985 in Guizhou . In the first flight tests, the JJ-7’s cockpit was too high due to problems in the air conditioning system. This problem, however, was eventually solved. In February 1988, the design of the JJ-7 was certified.
The JJ-7 gave the Chinese a Mach 2 trainer and was made available for export.
