## 1 Introduction  
### Outline of the Research  
The goal of reducing global fuel consumption and fuel-related emissions has placed tremendous pressure on the aviation industry. In 2018, the aviation industry was responsible for 895 million tons of CO\({}_{2}\) emissions globally emitted into the atmosphere [1]. Reducing fuel consumption will benefit both the world environment and the air transport industry. According to the Aviation Transport Action Group (ATAG), a reduction in fuel burning will have a significant impact on the aviation industry because the largest operating cost of this industry is fuel [1]. Drastic measures are still required even though some steps have already been taken to reduce these emissions. Various solutions have been implemented by the aviation industry, including smart material technology, laminar flow technology, air traffic management technologies, advanced propulsion techniques and sustainable fuels [2, 3, 4]. Morphing wing technology is one of the technologies showing high potential in decreasing aircraft fuel consumption [5, 6, 7, 8]. Even though there is no settled definition for \"morphing\", this term is borrowed in Aviation Technology from avian flight to describe the ability to modify maneuvers at certain flight characteristics in order to obtain the best possible performance. This type of application requires morphing structures capable of adapting to changing flight conditions. Morphing systems include several wing shape modifications, span or sweep changes, changes in twist or dihedral angle [9] and variations of the airfoil camber [7] or of the thickness distribution [4]. In the design phase, both military and civilian aircraft traditionally fly at a single or few optimum flight conditions; morphing, however, is envisioned to increase the number of optimum operational points for a given aircraft [5]. The morphing strategy scope is broad in the sense that an optimal solution can be generated in various ways with respect to a wide spectrum of mission profiles and types, and flight regimes. Novel technologies need to be part of recent efforts to produce environmentally sustainable and efficient aircraft. To meet environmental guidelines, including those of the International Civil Aviation Organization's (ICAO's) Committee on Aviation Environmental Protection (CAEP), innovative technologies such as \"morphing\" are fascinating as they provide advantages over conventional wing configurations [10]. Additionally, \"morphing\" is more practically applied in Unmanned Aerial Vehicles (UAVs) because of their reduced scale and lower complexity in terms of wing design structure and energy consumption expressed in terms of actuation power [6; 11; 12], in addition to the advantages that morphing designs are lighter and less noisy than their conventional designs. Some morphing opportunities with potential benefits for increasing aerodynamic performance of the UAS-S45 are shown in Figure 1.  
Aircraft are designed to achieve optimal aerodynamic performance (maximum lift-to-drag ratio) for a mission specification and for an extended range of flight conditions. Nevertheless, these mission specifications change continuously throughout the different flight phases, and an aircraft often flies at non-optimal flight conditions. Although the conventional hinged high lifting devices and trailing edge surfaces (discrete control surfaces) in aircraft are effective in controlling the airflow for different flight conditions, they create surface discontinuities, which increase the drag [13; 14]. The disadvantages of these hinged surfaces are found in both their deployed and retracted configurations [15]. When deployed, the gaps between the high lifting surface and the wing can cause noise and turbulence, and therefore can produce a turbulent boundary layer and thus increase drag. Even when retracted, the trailing edge hinges still produce a turbulent boundary layer. Numerous researchers believe that the laminar flow technology has the maximum potential to reduce drag and to avoid flow separation [16; 17].