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CJ-6 Primary Trainer Aircraft

Further progress in the pilot training of the Air Force raised a requirement for a primary trainer with tricycle landing gear and better performance than that of the CJ-5. By that time the Yak-18A, a derivative of the Yak-18 with tricycle landing gear had been developed in the Soviet Union and its drawings delivered to China. Xu Shunshou, project chief designer of the Aircraft Design Department in the Shenyang Aircraft Factory, concluded after his analysis that the performance of the Yak-18A was not advanced enough and its structure of steel tube frame was not suitable in China where aluminum material was in mass production. Therefore, he suggested developing a more advanced primary trainer to suit the conditions in China. His suggestion was accepted.

The design work began soon after designers' visits to Air Force bases where they made investigations and interviewed pilots. Lin Jiahua and Cheng Bushi took the responsibility of general layout design. From later part of 1957 to May 1958 the conceptual definition study, general layout design, wind tunnel test, performance analysis and preliminary design of the structure and systems were successively completed. A mockup in 1:1 scale was manufactured in the Shenyang Aircraft Factory. According to the general configuration the CJ-6 was evidently better than the CJ-5 in its performance, especially in flight speed, rate of climb, controllability and pilot's vision.

It was decided by the Aircraft Industry Bureau in May, 1958 to transfer the development of the CJ-6 to the Nanchang Aircraft Factory. An Aircraft Design Department was established in the Nanchang Aircraft Factory and more than 20 designers including Tu Jida and Lin Jiahua were sent to assist the Nanchang factory by the Shenyang Aircraft Design Department. The upper authorities appointed Gao Zhenning project chief engineer and Tu Jida and Lin Jiahua deputy project chief engineers. Due to the joint efforts of the two design departments a complete set of drawings in 5,177 standard pages were released in a short period of time.

Immediately after the release of these drawings, workers, with a sense of pride in manufacturing an aircraft designed by their own people established new records one after another: the sub-assembly by riveting took only two weeks to finish and the final assembly only 7 days and nights.

The static test of a full size CJ-6 airframe and drop test of its landing gear showed its compliance with design criteria. First flight of the CJ-6 by test pilots Lu Maofan and He Yinxi took place on August 27, 1958. In September two CJ-6s were ferried to Beijing and made a flight demonstration there to the leaders of the Military Commission of CCCPC.

A severe technical problem was found during the first flight. The engine and propeller made in Czechoslovakia did not match each other so that the CJ-6 could not fly at high speed. In August 1959 project chief designer Ye Xulun proposed to retrofit the CJ-6 with Soviet A-14P engine and F530D35 propeller. His proposal was accepted and a retrofitted CJ-6 began its flight test by two pilots including Huang Zhaolian on July 18, 1960.

Huang Zhaolian was a test pilot for the CJ-5 national certification programme. He had flown many airplanes made in Germany, Japan, Italy, the United Kingdom, the United States of America, France and the Soviet Union with a total of 5,000 flying hours. During the flight test he undertook the most difficult and dangerous tasks-spin. Spin is a kind of unintentional motion occurring when the angle of attack is beyond the critical angle of attack, in which the center of gravity of the aircraft descends rapidly along a steep helical line while rotating about its three axes. This is an unusual flight condition which will end in a crash if the aircraft can not be recovered from the spin. The primary trainer is required to have good spin characteristics so that a trainee may practice the spin and to learn how to recover.

The answer to the question of whether the CJ-6 could recover from a spin was unknown because the spin test were not conducted in a vertical wind tunnel. Although the technical people had carefully carried out a theoretical analysis and some emergent safeguards against accidents such as the installation of an anti-spin chute had been adopted, the risk involved in the flight test still existed. Huang Zhaolian made a detailed theoretical analysis of the spin and practiced recovery actions repeatedly before actual flight until he was confident of a successful flight. At nine o'clock in the morning on November 16, 1960 he started his spin flight test. He made a check of stall, then tried the spin from half circle to three circles. Every time he recovered successfully and so fulfilled the task of spin flight.

In 1961 the CJ-6 was redesigned in the Nanchang Aircraft Factory and another prototype aircraft was produced for certification in an attempt to overcome the following four major deficiencies found in its flight test: temperature too low at engine cylinder heads, poor heat dissipation of oil system, unwanted right yaw and unbalanced fuel consumption between right and left fuel tanks. The flight test of the new prototype aircraft was completed on October 15. A total of 1,800 takeoff-and-landings and 612 flying hours were accumulated. The Military Products Certification Commission of the State Council certificated the CJ-6 and approved its mass production on January 5, 1962.

In 1963 the HS6 piston engine and the propeller used on the CJ-6 were successfully produced. Since then all aircraft parts, components and accessories have been made in China.

An uprated engine HS6A was certificated in December,1965. A derivative of the CJ-6 with the HS6A engine was designated as CJ-6A.

The development of the CJ-6 took four and a half years, a rather short period for an aircraft developed on our own. The reasons for this short development period were the unsophisticated nature of the CJ-6 itself, its practical and realistic design philosophy and moderate aircraft performance requirements. The CJ-6 had its own distinguishing features in aerodynamic layout, i.e. emphasis on controllability and safety. In performance it was as advanced as similar aircraft in the world. Domestic airborne equipment were chosen as much as possible for use in the aircraft. This maximum use of what was available in China made it possible to concentrate on the improvement of the performance of the new aircraft.

Various difficulties were encountered and many setbacks suffered in the development of the CJ-6. Its development was almost stranded in its early stage of development because of improper selection of the engine. In addition it met strong competition from the Yak-18A. With support from higher authorities, the leading cadres and scientific workers at the Nanchang Aircraft Factory kept on with the development. They overcame all difficulties one after another, worked steadily and made solid and uninterrupted progress. At last they succeeded. From 1964 to 1966, ten CJ-6Bs with armament mounted were retrofitted at the Nanchang Aircraft Factory.

The CJ-6 was awarded a National Gold Medal in 1979. A total of 1,796 CJ-6s in all versions were produced from the beginning of production to 1986. It has not only made great contribution in training tens of thousands of pilots in China, it has also been flown by many countries around the world.

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