Z-5 [Mi-4]

In 1956 the Mi-4 helicopter production technique was introduced into China from the Soviet Union and it was decided that the license production of the Mi-4 with the Chinese designation of Z-5 would be undertaken by the Harbin Aircraft Factory. The Mi-4 was a single rotor medium helicopter of the world's first generation helicopters (essentially an enlarged Mi-2). Its design began in 1951 in the Soviet Union and its development work successfully completed in 1953. The Harbin Aircraft Factory, after a large scale updating and expansion during the First Five—year Plan and the overhauls to a number of aircraft, had the basic conditions for the aircraft production.

The technical drawings and documents of the Mi-4 helicopter arrived at the factory in early 1958 and the prototype production of the Z-5 was begun while a part of drawings were still being released. The prototype production proceeded very fast. The static test was completed in December of the same year. The first indigenous Z-5 helicopter, piloted by test pilots Qian Guangyou and Liu Xingxiang, flew into the air on 14 December, 4 months ahead of the schedule. In December 1959, the Z-5 was certificated for production.

But the prototype production of the Z-5 was adversely affected by the ideological trend of the "Great Leap Forward" . The tendency to concentrate on quantity production and production speed only and the insufficient selected production tooling caused serious problems in quality. These problems had to be solved and the process of prototype production had to be restarted from scratch in 1960. The updated drawings were released in March 1961 and the construction of 8,000 pieces of production tooling were completed in March 1962. On August 20, 1963 first high quality Z-5 made its first flight and on September 21 the Z-5 "passed the evaluation with excellent quality" and was formally accepted and put into mass production by the government.

The rotor is the critical component of the helicopter. The Soviet technical document specified that the blades of the rotor was made of wood and the criteria for the timber selection was very difficult. Soviet technical documents specified that the blades were to be made of high-quality wood of a specific type, not found in abundance in China. To find out qualified domestic timbers equivalent to the Soviet ones in characteristics a lot of work was done by the Harbin Aircraft Factory with the help from the Forestry Science Academy of the Forestry Ministry. The tests showed that it would waste astonishingly a lot of pine trees whose skin look like the fish scale to make the blades. Therefore, another timber, dragon spruce, was used instead, and the waste was reduced, but a considerable amount, approximately 20,000--30,000 cubic meters, of this precious timber had to be cut down each year. To find suitable dragon spruce, workers had to climb a height of 3,700 m above the sea level and three comrades from the Forest Department of Sichuan province died in this connection. The costly price of the three lives and enormous natural resource impelled the technical people to march towards another direction—the metal blades.

The advancement in technology is frequently combined with the complexity and difficulty. The metal blade was a major progress in the helicopter technology and it had been invented only for a short time in the world. The development of the metal blade at the Harbin Aircraft Factory began in May 1963. Hu Xichuan, chief engineer, organized the technical people to work on the project. With the help from the factories and institutes concerned they solved a number of technical problems one after another, such as the machining of blade spar, the fabrication and assembly of aluminum honeycomb structure and the making up of special adhesive, designed and produced 84 sets of assembly cramps and some special equipment such as a large autoclave which was 1.7 m in diameter and 11 m in length, and constructed the first metal honeycomb production line in the aviation industry. They completed the spar fatigue test whithin 16 months, in which a total of 570 million vibration cycles was recorded, and obtained very precious test data. A Z-5 equipped with indigenous metal rotor began its 8 days flight test on June 22, 1966 and it was showed by the flight test that the behavior of the metal rotor was better than that of the wooden rotor in all aspects. The metal rotor passed technical evaluation in July 1966 and since then wooden rotors have been completely substituted by metal ones.

The Harbin Aircraft Factory continuously improved its own manufacturing skills in the Z-5 prototype production. The qualified key components, i.e. swashplate, rotor hub and engine exhaust pipe, were manufactured and some critical tests, e.g. landing gear drop test, swashplate life test and thermal stress measurement of exhaust pipe at high temperature, were carried out so that the prototype production of the Z-5 was put on a reliable basis.

The Z-5 was a single four blades rotor helicopter powered by a domestic HS7 piston engine. A two—man flight deck was inside the nose of the fuselage. It could fly in the day and night and under complicated weather conditions. The helicopter was equipped for transportation, airborne landing and rescue. It can carry 11-15 paratroopers, or 1,200-1,550 kg cargos, or 8 noneffectives and 1 attendant. It can carry 1,300 kg sling load in hoisting work.

Premier Zhou Enlai showed his deep concern to the helicopter development. He issued a number of instructions to the development of the domestic helicopters and for 7 times he was flown in a Z-5 helicopter to carry out his tours in the country, to accompany foreign guests in their visits to China, and to express sympathy and solicitude to the people of disaster areas. A great numbers of staff and workers of the helicopter industry were greatly encouraged and inspired by him.

During the counter-attack wars at Zhenbao Island in northern China, on the south-west border and at the Xisha Islands the Z-5s carried out military transportation missions for the PLA. The Z-5s took part in rescues and disaster reliefs in Henan, Inner Mongolia grass land fires and Xingtai and Tangshan earthquakes. On 10 January 1983, the pilots of the PLAAF flew Z-5s to the Yellow River, and whilst hovering on the icy-surface on one wheel, rescued 58 passengers in distress. In addition Z-5s also took part in the survey of the Halobios and the explosion test of China’s first atomic bomb. In a large-scale military exercise in North China 35 Z-5s took part. Z-5s were also sent to some countries as foreign aid.

A total of 545 Z-5s were produced by 1979. Among them 437 were of basic version, 86 of passenger version, 7 of agriculture and forestry version, 13 of rescue version and 2 of aerial survey version. These helicopters played their roles in various fields such as in the national defence and national economy. During the counterattack wars at Zhenbao Island in northeast China, on the southwest border and at the Xisha Islands the Z-5s carried out military transportation missions very well. The Z-5s participated in rescues and disaster reliefs in Henan, Inner Mongolia grass land fires and Xingtai and Tangshan earthquakes. On January 10, 1983 the pilots of the People's Air Force flew the Z-5s to the Yellow River, and used the hovering technique to land on ice surface with single wheel and rescued 58 passengers in distress. In addition the Z-5s also took part in the survey of the halobios and the explosion test of the Chinese first atomic bomb. In a large scale military exercise in North China 35 Z-5s performed their missions. The Z-5s have been also sent to some countries as foreign aid.