By the end of 1962, the operator asked CAE to modify the WP6 engine into a turbofan engine (after-fan type). At that time the turbofan was one of the development targets in the world for aircraft powerplant. It was an active and thoughtful arrangement to use WP6 engine as the basis. The Shenyang Aero-engine Research Institute (SARI) was assigned to undertake the task, which was headed by Yu Guangyu, Zhou Gao and Wang Guodong. The development proposal was presented in January 1963 and it was named the WS5 engine.
Compared with the WP6 engine, the WS5 featured a rear fan, no afterburner, variable inlet guide vanes and stator vanes of the 1st, 2nd and 3rd compressor stages instead of a bleed valve. There were also other related changes. The modified engine achieved a gain in performance. The take-off power reached 35 kN (3,600 kgf) with a 35% increase; and s.f.c. at take-off condition reduced by 30%. The aircraft range had a fairly big increase due to the improvement of the compressor efficiency and lower s.f.c.. It was anticipated that the range of the H-5 aircraft re-engined with WS5 engine was expected to increase by 30%. The engine operating envelope was extended and there were improvements in starting and acceleration characteristics.
After completion of the WS5 engine paper work, SARI invited 7 experts outside of CAE including Professor Wu Zhonghua of CAS to review it. President Tang Yanjie of CAE presided over the review. These experts gave positive opinions on the development of the turbofan engine and the definition of the important parameters of the WS5 engine.
The design, manufacture and testing of the rear fan caused great difficulties. Among them, the manufacture of the "combined turbine - fan bucket" was a critical technology. After solving the problem, the first engine was assembled at the beginning of 1965. During test, cracks were found at the root of the fan blade portion caused by stall flutter. This problem was solved. In 1966, the engine's maximum thrust and s.f.c. reached the design targets.
Then 7 prototype engines in two batches were built and after test and modification, some other problems were solved. In 1970, the engine passed the endurance test. In 1971, the H-5 aircraft with the WS5 engine had several taxings and the engine worked smoothly. Later, the operator decided that they would not re-engine the H-5. The development of WS5 ceased in May 1973. It was a successful try for the development of the turbofan engine. Some techniques such as the design of the supersonic & transonic fan blade, compressor variable vanes and their regulator were applied to many other engines later on.
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