Hypersonic Transport Propulsion System Research (HYPR) Project was started in 1989 to develop the technologies for the propulsion system of a Mach 5 HST airplane, which could be environmentally acceptable and economically viable. The engine being studied is the combined cycle engine composed of a turbo engine which can operate from take-off to Mach 3 and a ramjet engine which can operate over Mach 2.5 to Mach 5. The variable cycle engine (VCE) concept is applied to the turbo engine to satisfy the requirements for low noise level at take-off and high specific thrust at high altitude and speed. The design and manufacture of demonstrator engines have been performed. The first turbo engine test and the first heated inlet test of the core engine was carried out successfully in December 1994 and March 1995 respectively. This paper describes the turbo engine design and those test results.