A way to face the challenge of moving towards a new greener aviation is to exploit disruptive aircraft architectures; one of the most promising concept is the PrandtlPlane, a box-wing aircraft based on the Prandtl's studies on multiplane lifting systems. A box-wing designed accordingly the Prandtl “best wing system” minimizes the induced drag for given lift and span, and thus it has the potential to reduce fuel consumption and noxious emissions. For disruptive aerodynamic concepts, physic-based aerodynamic design is needed from the very early stages of the design process, because of the lack of available statistical data; this paper describes two different in-house developed aerodynamic design tools for the PrandtlPlane conceptual aerodynamic design: AEROSTATE, for the design of the box-wing lifting system in cruise condition, and THeLMA, aiming to define the layout of control surfaces and high lift devices. These two tools have been extensively used to explore the feasible space for the aerodynamic design of the box-wing architecture, aiming to define preliminary correlations between performance and design variables, and guidelines to properly initialize the design process. As a result, relevant correlations have been identified between the rear-front wing loading ratio and the performance in cruise condition, and for the rear-front flap deflections and the aeromechanic characteristics in low speed condition.

The paper deals with theoretical and experimental studies for the development of a self-powered structural health monitoring (SHM) system using macro-fiber composite (MFC) patches. The basic idea is to integrate the actuation, sensing, and energy harvesting capabilities of the MFC patches in a SHM system operating in different regimes. As an example, during flight, under the effects of normal structural vibrations, the patches can work as energy harvesters by maintaining or restoring the battery charge of the stand-by SHM electronic board; on the other hand, if relevant/abnormal loadings are applied, or if local faults produce a noticeable stiffness variation of the monitored component, the patches can act as sensors for the power-up SHM board. During maintenance, the patches can then work as actuators, to stress the structure with pre-defined load profiles, as well as sensors, to monitor the structural response. In this paper, the investigation, based on the electromechanical impedance technique, is carried out on a system prototype made of a cantilevered composite laminate with six MFC patches. A high-fidelity nonlinear model of the system, including the piezoelectric hysteresis of the patches and three vibration modes of the laminate beam, is presented and validated with experiments. The results support the potential feasibility of the system, pointing out that the energy storage can be used for recharging a 3V-65mAh Li-ion battery, suitable for low-power electronic boards. The model is finally used to characterize a condition-monitoring algorithm in terms of false alarms rejection and vulnerability to dormant faults, by simulating built-in tests to be performed during maintenance.

The development of novel aircraft concepts and propulsion technologies requires up-to-date physics-based methods and tools for conceptual aircraft design. In this context, a simulation model for the take-off manoeuvre is proposed in this article, to be employed in the conceptual design phase for aircraft whether of traditional or innovative configuration. The model is capable of evaluating the longitudinal dynamics, both translational and rotational, of the aircraft considered as a rigid body, and influenced by the aerodynamic effects introduced by the presence of the ground. The ground effect, indeed, induces variations in the aerodynamic forces depending on the distance and the attitude of the lifting surfaces from the ground, which may significantly influence the aeromechanical characteristics of the aircraft during the evolution of the take-off manoeuvre. The simulation model is based on the numerical solution of the equations of the dynamics of the rigid aircraft in the longitudinal plane and integrates a vortex lattice aerodynamic solver to evaluate the aerodynamic and aeromechanical characteristics of the aircraft considering the ground effect in each time-step. The proposed approach is configuration independent, as it can model the geometry, evaluate the aerodynamics, and simulate the dynamics of aircraft with any lifting architecture; furthermore, the simulation model is fast and flexible, making it effective for the conceptual phase of aircraft design. The paper proposes the description of the take-off manoeuvre of two aircraft with different airframes: one with a conventional tube-and-wing architecture and one with a box-wing lifting system. The results proposed highlight the potential of the simulation model to detect aeromechanic and dynamic differences during the development of the manoeuvre for different aircraft configurations, and to assess the significance of considering ground effect aerodynamics.

This paper presents a study on the aeromechanical characteristics of a box-wing aircraft configuration with a focus on stability, controllability, and the impact of aeromechanical constraints on the lifting system conceptual design. In the last decade, the box-wing concept has been the subject of several investigations in the aeronautical scientific community, as it has the potential to improve classic aerodynamic performance, aiming at reducing fuel consumption per unit of payload transported, and thus contributing to a reduction in aviation greenhouse emissions. This study characterises the aeromechanical features of a box-wing aircraft, with a specific focus on the correlations between the aeromechanical constraints and the (main) aircraft design parameters. The proposed approach provides specific insights into the aeromechanical characteristics of the box-wing concept, both in the longitudinal and lateral plane, which are useful to define some overall design criteria generally applicable when dealing with the conceptual design of such an unconventional aircraft configuration.