*2.3. Considered Wiring Configurations*

The partial turboelectric powertrain architecture in this study uses four propellers, two driven by electric motors and two driven by gas turbines. Each electric motor is directly coupled via cables to its related generator, which converts part of the shaft power of the gas turbine, sparing the use of large electric energy storage devices. This configuration enables two wiring options, as suggested by [21]. An "on-wing wiring" approach, where the gas turbine on one wing is coupled to the electric motor on the same wing and a "cross wiring (x-wiring)" approach where the gas turbine is coupled to the electric motor on the opposite wing. Both wiring options can be seen in Figure 1 for the PT2025 and PT2025opt configuration, respectively. The red and green lines symbolize two separate and independent wiring harnesses, each connecting one gas turbine driven generator to one electric motor.

Some parameters of the different configurations are listed in Table 2. All four aircraft are similar to each other and have roughly the same wingspan, differing only 0.1 m. The PT2025opt aircraft are lighter than the PT2025 aircraft with the same wiring option, as the further outboard positioning of the gas turbine engines reduces the structural mass of the wing. The different positions of the gas turbine can also be seen in the conductor mass, where the difference between the "on-wing" and "cross-wing" option is larger for the PT2025opt aircraft due to the increased difference in the necessary cable lengths that can be seen in Figure 1. The increased aerodynamic efficiency of the PT2025opt aircraft, as mentioned in Section 2.2, can be seen in the trip fuel mass. The PT2025opt aircraft with cross wiring (Configuration 4) has a higher OME and MTOM than the PT2025 aircraft with on-wing wiring (Configuration 1), but uses 1.0% less fuel over the same mission.


**Table 2.** Parameters of the investigated concept aircraft.
