Design of a STOL Ultralight aircraft in composite material

The class of ULM (Ultra Light Machines) and light aircraft in general has attracted growing interest through Europe in recent years. Only in Italy, in the last 5-6 years, at least 10 companies have started production of ULM aircraft. There is a very active market for this class, used to promote flight at all levels and for sports aircraft. The maximum flight speed for ULM aircraft has been increased in recent years through the use of more powerful engines (100 hp instead of 64 or 80) and better aerodynamics. It is not surprising that a maximum level speed of about 280 km/h has been reached. Since the weight constraints are very strict (maximum take-off weight must be 450 kg), it is important to investigate different solutions to improve structural design, safety, flight qualities, aeroelastic behaviour and systems reliability, without raising costs. Following the experience acquired in our department in designing light and ultra light aircraft, the design of a new composite ULM is being carried out at DPA. The paper deals with the design of a STOL (Short Take-Off and Landing) ultra light aircraft, starting from a market survey, the conceptual design loop and the preliminary choice of dimensions, and leading to the detailed design of efficient high-lift systems and a low-drag fuselage shape. Technological challenges regarding the design of low-cost systems for flap/slat retraction and a simple wing folding system are highlighted.