The lack of airworthiness and certification criteria for the employment of UAV vehicles in the civilian field has caused an uncontrolled proliferation of projects and the construction of a number of UAV prototypes which differ in dimension, weight, flight characteristics and payload carriage. This paper is aimed at identifying the most important project criteria which may concur to unifying the main UAV characteristics. in particular, the minimum take-off weight is investigated which is able to guarantee the adherence to the levels of safety required by the airworthiness design requirement (ADR) currently being developed. To this end, the characteristics of mission and the safety requirements currently available in the ADR have been examined. and the safety characteristics and reliability of the UAVs used in the military field have also been considered. After which, an assessment is made of the on-board system and the relative redundancies necessary for adjusting such characteristics to meet the ADR. Taking into account the weight of systems, payload and other UAV components (engine, structure, etc.), a reasonable estimation of the take-off weight as well as the geometrical dimensions of a certifiable UAV are obtained.
