J-8 (Jian-8 Fighter aircraft 8) Design
After several years of careful preparation and deliberation the development of a new high altitude and high speed fighter was unveiled in the aircraft industry. In May 1964 the CAE proposed at a meeting to develop a fighter with better performance on the basis of Soviet MiG-21 fighter.
The work on the conceptual definition was commenced in October 1964. At a meeting on investigation of the conceptual definition the Shenyang Aircraft Design Institute put forward two design options. One was a single engine design which required an all new high thrust engine to be developed. The other was a twin engine design which required a new derivative of a proven engine to be developed. The latter was finally accepted at a meeting convened by Tang Yanjie, President of the CAE. This was a right selection because there existed already certain technical bases. This design selection became the prerequisite of the success in the development of the J-8. Luo Ruiqing, chief of General Staff approved the development program and its operational requirement on May 17, 1965. The fighter was designated as J-8 and the major tasks of the development were undertaken by the Shenyang Aircraft Design Institute and the Shenyang Aircraft Factory.
The State leaders showed their deep concern for the development of the J-8. On August 14, 1965 when vice premier He Long was hearing a report on the development status of the J-8, he pointed out: "The J-8 must be successfully developed at an early date." Marshal Nie Rongzhen expounded several issues which had to be taken into consideration in the design of the new fighter in his letter dated August 18 to vice chief of General Staff Zhang Aiping, and these issues played an important role in the development of the J-8.
In the design concept of the J-8 the stresses were put on the service ceiling, speed, range, rate of climb, and fire power, etc. The deficiencies of the J-7 were made up one by one on the J-8, therefore the performance of the J-8 was improved as follows:
- Maximum flight speed M 2.2;
- Absolute ceiling > 20,000 m;
- Maximum rate of climb 200 m / sec;
- Basic range Maximum range 1,500 km; 2,000 km;
- Duration of combat at 19,000 m altitude was specified;
- An improved aerial gun and air-to-air missiles were installed; and
- A radar with longer search distance was installed.
The aerodynamic configuration of the J-8 featured a nose intake, a high sweptback, low aspect ratio and thin delta wing, a low set tailplane and two ventral fins. Two WP7A engines were chosen as its power plant. The aircraft thrust to weight ratio reached 0.89, which was better than that of the J-7.
The design of the J-8 was in full swing in September 1965. Its technical work was led by Ye Zhenda and coordinated by a Chief Designer Office headed by Wang Nanshou after the chief designer Huang Zhiqian unfortunately died in an airliner crash abroad in May of the year. In December a wooden mockup of the J-8 was reviewed. In March 1966 the designers went to the factory and started their on site design with the assistance of workers and manufacture engineers. A complete set of drawings was released for the production at the end of 1966 and the production documents in early 1967. The factory began the prototype production immediately after they had received these drawings and documents.
Vice chief designer Gu Songfen and his design staff investigated several alternative aerodynamic layouts and conducted a great number of wind tunnel tests. One layout was finally selected and many major technical problems, e.g. the supersonic direction stability, the choices of the locations for the tailplane and the vertical fin and the pressure center of the aircraft, were successively solved.
During the on site design a way of three-in-one combination was adopted, by which 570 and more designers including Wang Nanshou and more experienced workers including Chen Ayu and Wang Ahui and more manufacture engineers were combined into a single team for investigation to the designs and drawings. In this phase the manufacture engineers from the factory made 2,330 and more suggestions. Out of them 1,660 were accepted and 40 significantly improved the workability of the design in the manufacturing. One example was an innovative proposal to delete the pads underneath the wing main spar, which was realized by the designers after they tested a wing main spar of the MiG-21 fighter with the help from the manufacture engineers and workers. This innovation changed the traditional structure of the MiG aircraft and saved 4 kg in weight on the J-8.
One difficulty in J-8 development was the design of the bullet feed and ejection system of the aerial gun. The system should ensure the continuous firing in flight. Soviet experts took the design of the system as their patent and, therefore, they kept it secret. In tackling technical problems of the bullet feed and ejection system, the designers worked together with workers. They run the tests and modified a gun to simulate the firing in flight. 10,000 rounds of dummy bullets in total were fired. They had at last found the laws of the system and succeeded in its design.
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