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Aim of this study is the development of an integrated methodology able to support the structural design of an UAV demonstrator, having a joined-wing configuration and a high structural flexibility. HAPD (High Altitude Performance Demonstrator) is an UAV multi-mission, very light vehicle under development at CIRA, the Italian Aerospace Research Centre. HAPD structure is redundant as regards constraints, so the internal forces depend upon the stiffness distribution. In addition the evaluation of flight loads has to be performed without neglecting the flexibility of the structure. Because of the extreme unconventionality of the configuration the design of the primary structures has been widely affected by aeroelastic analyses.

In this paper a method to evaluate ground loads due to the impact of a high aspect-ratio wing of an unmanned aircraft at landing is presented. The aircraft for which the loads are calculated - code named HAPD (High Altitude Performance Demonstrator) - is an unmanned aircraft under development at the Italian Aerospace Research Center. It is a scaled performance demonstrator of an 80m-wing span High-Altitude & Long Endurance Unmanned Aircraft, born as a risk mitigation project of its full scale parent. Its peculiar feature is a Joined-Wing configuration. The joined-wing configuration is a good compromise between high lift, low weight and low global flexibility when compared with a conventional configuration with the same aspect-ratio. HAPD configuration consists of a mainly straight Front Wing and a Rear Wing with negative sweep and dihedral angles. The junction location is at about 70% of the FW semi-span, which was chosen as the best location in the preliminary design phase.

The target of this paper is to describe the SHM project developed at CIRA. In order to achieve the low weigh target in the MALE UAV structures, the SHM project has the target to setup a system that, being able to evaluate the current state of the structure, will enable minus conservative assumption in the composite structural design. A lamb wave based procedure has been developed in order to analyze the presence of a barely visible impact defect (BVID). The techniques for the damage detections of composite and metallic structures have been developed through extensive numerical-experimental analysis based on lambwave investigation by using piezoelectric sense- actuators. The use of SHM technology and methodology has shown the possibility to have a significant reduction in the structural weight. The technology has achieved a TRL level between 4 and 5 and in order to achieve a higher TRL a test on a component in relevant environment is planned at the end of 2014.

In this paper an automatic procedure aimed at preliminary designing an oleo-pneumatic landing gear strut for a light unmanned aircraft is presented. The whole work is motivated by the necessity to design the landing gear of the unmanned aircraft X-MALE, currently in development at the Italian Aerospace Research Center (CIRA SCpA), according to the Airworthiness Requirements NATO STANAG 4671 (USAR). The landing gear preliminary design is usually carried-out by responding to requirements of maximum overall dimensions, maximum weight and maximum attainable load factor. While the oleo-pneumatic mechanism depends essentially on the maximum vertical load factor and on the strut length, thus on the oleo-pneumatic efficiency, the structure is generally sized by combining the design vertical loads with the maximum expected horizontal loads.