General Aviation (GA) aircraft crashworthiness of the vehicle when it hits the ground after the parachute deployment is an important issue. The current dynamic emergency landing regulation (CS 23.562) defines the maximum human tolerant accelerations under both vertical and horizontal directions. This article aims to compare two different aircraft configurations: metal low-wing and composite high-wing ones. Both are two-seats and single-engine GA aircraft. The purpose of the analysis is to check whether the seats and restraint systems met human injury tolerance standards and to determine the possible impact on passengers in the cabin space due to shock loads. Finite element analysis of the fuselage sections for both configurations is performed using the commercial LS-Dyna solver. An extensive campaign of experimental tests has been performed on the composite samples for tuning and validating the model and to find the transition from an undamaged up to totally collapsed sample. The material of the composite fuselage has been characterized through experimental tests. The adopted material model has been refined to match with the performed experimental analysis, allowing high-fidelity modeling. A parametric analysis has been performed to determine the optimal impact angle in terms of lumbar injuries and loads transmitted by the seat belt due to aircraft contact with the ground, thereby increasing the level of safety. The investigations carried out may be an important indicator of the design of the parachute system.
Multirotors are gaining great importance in the layout of innovative and more agile mobility. In this framework, a possible solution to developing an aircraft complying with the stringent size requirements characterizing this type of application can be a coaxial rotor configuration. To exploit the several possibilities linked to coaxial rotors, a scaled experimental model is designed to evaluate the performances of the counter-rotating propellers system, concerning the distance between the two propellers. Both thrust and noise are considered as parameters of interest. Two brushless motors are deployed whereas the propellers' angular velocity, in terms of round per minute (rpm), is controlled by an external control system. Tests are conducted on both single isolated propellers as well as on the counter-rotating system: the two propellers and their respective motors have been characterized concerning the thrust. Furthermore, a comparison with a numerical model is performed. Noise evaluation on the single propeller has shown a motor contribution prevalence at a low rpm regime (1140-1500 rpm) and a propeller prevalence for angular velocities higher than 1860 rpm. By varying the distances between the propellers a sensitivity analysis is performed with the aim of identifying the optimum configuration taking into account both noise and thrust performances.
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