## 1 Introduction  
Electrification of conventional powertrain systems in vehicles is a popular topic, because of concerns about global warming, remaining fossil fuel sources and efficiency [1, 2, 3]. Conventional systems are harmful to the environment, because they emit hazardous gases into the air. Also, they are less efficient compared to electric motors. The average efficiency of a conventional propulsion system that uses fossil fuels as a power source is about 40%, while electric motors have an efficiency of over 90% [4, 5, 6]. In addition, it is been known that fossil fuel sources are decreasing year by year and as a result of that alternative power sources are being searched for, to prevent any limitations or disruptions in vehicle operations caused by a limited supply of fossil fuels [7]. In this regard, electric motors are feasible to use instead of conventional ones. The More Electric Aircraft (MEA) and All Electric Aircraft (AEA) concepts were created to convert conventionally powered systems to electrically powered systems. These concepts also include powertrain systems, and this is an expanding area in which to work, for the reasons mentioned above. Unmanned Aerial Vehicles (UAVs) are also among the aircraft that are growing more popular day by day, because of their environmentally friendly, silent and efficient operations [8, 9, 10, 11, 12, 13]. They are classified according to their weights, range and operating altitude. Some UAVs already have electrified propulsion systems. However, some of them use a conventional Internal Combustion Engine (ICE) as a propulsion system. One class is named the Medium-Altitude Long-Endurance (MALE) UAV [14, 15, 16]. Long range and endurance are significant characteristics of this type of UAV. For this reason, it is not easy to implement an electric propulsion system on this platform,because of current battery technology. The topology of an electric propulsion system is shown in Figure 1:  
It can be seen from Figure 1 that an electric motor is powered by a battery and that it is not feasible for long-endurance operation because of its limited power supply, due to current battery technology. Despite this disadvantage, it can still be used, depending on the mission type or duty requirement [17; 18; 19]. To create an electrically powered UAV, a Brushless DC (BLDC) motor was selected as the powertrain and designed anew for this study. It was selected because of BLDC motors' easy and precise control of speed, and their reliability, low cost, easy maintenance, high torque-weight ratio, high efficiency, and low noise operation [20; 21]. On the other hand, reliability is a crucial factor, especially in aviation, and the components used in aviation must be dependable. To provide reliable operation with our designed electric propulsion system, the BLDC motor was created as a five-phase motor. Our aim was an electric motor that could produce the required torque to fly an aircraft even in the failure state of the motor phases [22; 23; 24]. In this study, our multi-phase BLDC motor was designed and implemented in a UAV model, which was selected from currently used UAVs in the industry, with computer-aided programs. After the design and implementation processes, the performance of the designed electric propulsion system was observed with a system-level model of the designed motor. In the Section 2 below, our BLDC motor design, its parameters and the creation and implementation of the UAV model are explained. To run the simulations for a purpose, a flight profile was created, and the simulations were run according to this profile. In Section 3, we show the obtained outcomes of the simulations, with both graphical and tabulated data. Our displayed results are evaluated and criticized in the Section 4. To sum up and finalize our obtained results, we show our final assessments in Section 5.