Experimental investigation of a new concept for operations for the general aviation sector: the case of the full-electric Segull hydroplane

With the increasing concerns about environmental pollution, several international organizations are setting more restricting rules for aircrafts homologation, similarly to what is happening in the Automotive field. The CO2 produced by the global aviation constitutes about the 2% of the total related to humans activity. Even if this percentage seems not much relevant, each year more than 900 million metric tons of carbon dioxide are emitted by the aviation industry, with an increasing trend that raises many concerns about the global warming. At the aircraft level, the only way to reduce as much as possible the CO2 emissions is the adoption of electric solution, based on batteries or hydrogen as main energy source. Nowadays, electric flight is already present for smaller aircrafts and for unmanned aerial systems like UAV, but more and more bigger companies, like Airbus and Boeing, are working on the electrification of their fleet. The Achille’s heel of the diffusion to a global scale of the electric flight is the energy density of battery, which is very low if compared to jet fuels one. This translates in a significant reduction of the range and of the cruise altitude, which are crucial factors for long-range operations. Nevertheless, the electrification of the propulsion systems brings many advantages if compared with a traditional one based on an internal combustion engine: higher efficiencies, lower take-off length thanks to the higher torque at low speed of electric motors, and less maintenance, to name some. All that said, the objective of this work is the definition of the experimental campaign on a powertrain test bench, and the further characterization of the battery pack of the Seagull, a hybrid electric aircraft produced by Novotech. The Seagull is 2-seater seaplane, endowed with an automated wing folding system, which can work both as an airplane and as a boat. Its main characteristic is its hybrid-powertrain, made of an electric motor coupled with an endothermic engine in a parallel configuration. This architecture, which potentially allows a full-electric flight, is needed to add about 25-30 Hp to the maximum power of the internal combustion engine, in order to reduce the take-off length. The first part of this work was focused on the bibliographic research related to electric flight, and on the study of design of experiment (DoE) methodology to understand how to correctly analyse the data produced on the test bench. The following step consisted of defining the first screening tests procedure in agreement with Novotech, performed on a powertrain test bench at Novotech, made of the propeller, the electric motor (Emrax 228 LV), the power electronics, and of a LiFePO4 battery pack, with a capacity of 80 Ahr and energy of 7 kWh. The tests have been performed on a full electric configuration, since the objective was to understand the general behaviour of the battery, with the prospective of a full electric flight. Then, a series of tests have been performed on the same test bench, varying the rotational regime and the initial state of charge. In the following steps, data produced by the tests have been elaborated and analysed, in order to understand the most significant behaviours of the battery pack. In last step, a virtual battery has been designed in order to fulfil the requirements for a regional full electric flight, which has been simulated on Matlab.