This project specified and designed a wind tunnel tool to investigate the aerodynamic problems induced by the interaction of engine slipstream and airframe at high subsonic to transonic speeds. This tool was a large modular generic wind tunnel model, powered with air turbines for engine simulation.
First of all, the aircraft to be simulated with the GEMINI model were identified and fully defined (specification, shape and general arrangement). A number of alternative parts were included for later use. The wind tunnel operators were also involved in designing all the missing or new interfaces with their facilities (balances, stings, electronics). Then the model design started from both structural and instrumentation sides. Its heart was the skeleton, a primary structure on which the complete set of components (wings, fuselages, tails) was to be fitted in the ad hoc configuration. Its skin was also fully defined on manufacturing drawings. Another important part of the project was the power plant simulator itself. This consisted of an air driven turbine, the propellers and all related instrumentation, such as rotating balances designed to read thrust and torque during the tests. These pieces of hardware were specified and designed by specialists.
All the technical objectives of the project have been met. Even more, a consistent programme for wind tunnel testing has been initiated, including all the procedures necessary for its successful completion. More than 1000 documents (drawings and memorandums) have been produced.