Safety assessment for fixed-wing UAVs for remote sensing applications: Turin Case study

Large amounts of greenhouse gas emissions come from residential, industrial and commercial buildings in urban areas. Consequently, decarbonisation plans and design solutions must be implemented to reduce emissions. In this context, the thesis proposes an aerial thermal infrared remote sensing mission concept for detecting building heat losses, inspired by a previous study on energy demand estimation using thermal images regarding the city of Turin. Thermal imaging applications can be carried out by equipping aircraft, drones or satellites, depending on the level of detail required, with cameras capable of collecting emitted infrared radiation. Specifically, the proposed mission is conceived for a fixed-wing unmanned aerial vehicle (UAV), comparable in size to a small general aviation aircraft. The thesis is developed according to a multi-step process that includes two main parts: the case study definition and a preliminary aircraft safety assessment. While the first part recalls methodological aspects of mission design, the second part illustrates an approach to aircraft safety typical of the initial design phases. The process begins by defining the mission statement and continues with a stakeholder analysis. Subsequently, mission objectives and high-level requirements are derived and a trade-off analysis of possible thermal infrared camera options is performed. In addition, a brief market overview of thermal imaging systems and UAVs is presented. The first part of the process ends by characterising the mission and payload in operational terms. In particular, the flight operations are described graphically with a basic concept of operations on which the subsequent calculation of thermal infrared camera performance and image acquisition phase time is based. This calculation, which includes a parametric analysis, is performed using a code created specifically for the case study. The core of the second part of the process is a functional analysis which provides several results. First, the unmanned aircraft system (UAS) functional tree, which includes the UAV functional tree, is developed for the case study. Specifically, only the functions of the UAV are shown in detail in the thesis. Once these functions are determined, they are matched to the products able to perform them, obtaining the functions/products matrices. These products are then grouped to create the UAV product tree, useful for drawing a UAV conceptual design sketch to describe the hypothetical aircraft architecture. After, an aircraft functional hazard assessment is conducted, giving as input the identified functions, to determine the failure conditions associated. Considering that the mission is a civil application, for the classification of failure conditions and the allocation of safety requirements the JARUS AMC RPAS.1309 is applied as the regulatory reference. By combining functional analysis and hazard assessment results, a preliminary aircraft fault tree is finally proposed to study the higher-level causes that could lead to the loss of the UAV. In conclusion, the thesis is a baseline study that lays the groundwork for future missions in different urban environments, achievable with existing or next-generation UAVs. Secondly, the initial safety assessment constitutes a starting point in designing a new mission-oriented UAV concept, compliant with the safety regulations for certification.