HS7 piston-type engine
The HS7 engine was made by Harbin Aeroengine Factory (HEF) using technical documents of Ash-82V engine provided by the Soviet Union. It was a large radial air-cooled piston engine with 14 cylinders in two rows and a two speed supercharger. Its take off power was 1,250 kW (1,700 hp) and its weight 1,070 kg. It was installed in the Z-5, the first helicopter made in China.
HEF was transformed from a weapon factory and in May 1951 also experienced a transition from overhaul to manufacture. Initially, a Russian field repair and maintenance train drove into the factory. The technical officers and soldiers did repair work and also trained the factory people in repair skills. Then the factory invited Soviet experts to help them speedily master the repair skills for Ash-21 and Ash-82FN engines. In five years, the factory totally repaired and overhauled more than 4,000 of the above-mentioned two engines and also made many spare parts to meet the overhaul requirements. Thus, conditions were created for the factory to turn wholly to manufacture. In 1957, the factory successfully made the trial production of Ash-21 engine. It was a single row, radial, 7 cylinders, air-cooled piston engine, with 515 kW (700 hp) take-off power and installed in the Russian Yak-11 medium trainer and UTB-2 bomber trainer. They produced and delivered 21 engines in that year. Then its production ceased as China did not make Yak-11 aeroplanes.
Trial production for the HS7 engine started in 1958 and its approval test finished in 1959. Due to the effect of the "big leap forward", there were quality problems. In 1961 a fresh try for the trial production was carried out and in September 1963, the engine got the approval with good quality. In 1966, design improvement measures were undertaken such as oil ejection lubrication in the main cylinder, to solve the scrapes on the cylinder and the flake off of the crank counter-weight sleeve that occurred during operation. That made the engine work more stable and reliable. By the end of its production in 1980, more than 1,500 engines had been produced. Some 200 engines were also exported to 8 countries.
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