Preliminary design of a self launching system for the JS1 glider

Abstract

In this project a preliminary design of a self-launching system for the JS1 sailplane was attempted. The design was done according to CS-22 airworthiness requirements for sailplanes, which governs sailplane design. The basic design process consists of the engine selection for the system, aerodynamic design of a propeller, modeling of a retraction system mechanism with the frame and prediction of the performance of the JS1 with the system. The engine selected was the 39kW SOLO 2625-01 engine, which will give a climb rate of 4.26 m/s at an all up weight of 600 kg. The propeller was designed using the minimum induced loss propeller design technique. A requirement for the self launching was that it should be fully retractable allowing an unaltered aerodynamic shape when retracted. The maximum retract and extract speed is 140 km/h. A spreadsheet model was developed to calculate the retraction forces and to allow parametric optimization of the retract mechanism. There was severe geometrical constrains on the system as there is only limited space available in the fuselage of the glider. When all specifications and constraints were taken into account it was possible to design a self launching system that will fit in the glider and meet the specifications. Further work will allow the preliminary design to be worked into a detailed system suitable for prototype manufacture.