The present work provides a method for maintenance cost estimation for a civil aircraft. The model evaluates maintenance costs at a subsystem level in order to quantify the effective impact of each aircraft part on the total maintenance cost. An analysis at the subsystem level can offer a more precise cost estimation because the most influential parameters (that is, the cost drivers) should be different for each aircraft part. Emphasis is given on the updating of a cost-estimating model proposed in 1966 that provided equations for the maintenance cost assessment at a subsystem level using the Air Transport Association nomenclature. The reference method is enhanced with additional cost items, and the choice of cost drivers is accurately considered. The application of the developed model shows good accordance with the reference values provided by the International Air Transport Association, and results are compared with the common state-of-the-art methods.

In this paper, an innovative methodology for the conceptual design of hybrid-powered airplanes is proposed. In particular, this work focuses on parallel hybrid architectures, in which the thermal engine is mechanically coupled to an electric motor, both supplying propulsive power during a limited number of flight phases, e.g. during takeoff and climb. This innovative solution is the subject of several studies being carried out since the current decade. In this paper, a brief overview of the works conducted by other researchers is provided. Then, an overall aircraft design methodology is proposed, which is derived from the most renewed design algorithms. The original contribution of this work is represented by the development of a methodology for the design of hybrid propulsion systems. Moreover, the proposed method is integrated within a global aircraft design methodology. In particular, several effects of the innovative system on the entire aircraft are considered, for instance the variation of the empty mass or the impacts on fuel consumption. The paper ends with some case studies of the proposed design methodology, and a discussion of the obtained results is provided.