## 3 Results
### Detection of Structural Damages  
In general, the temperature of the components heats up before the failure. The component's temperature is determined according to crisp images without direct contact with the component's surface. Data could be displayed in real time; also, they could be transferred and subjected to analysis to a digital storage device. Hot spots and excessive heat caused by insufficient insulation are clearly recognized in images before these defects could lead to failure [36]. The thermal infrared technology has been widely used for rescue, surveillance, and automatic target recognition. Tracking based on this technology is not subject to illumination variations; thus, it can track the target in total darkness [38]. The heat signatures of electrical components captured by the FLIR camera are not affected by the surroundings such as the sky or clouds because the camera is capable of their recognition. The ability to recognize these differences is one of the main features of the FLIR camera. The temperatures of the monitored targets can be compared with predefined values set by the user thanks to integrated logic, memory, and data communication. Data are transmitted to a central monitoring station for trend analysis, generating exception reports, and in case the temperatures exceed threshold values or if another abnormal condition is monitored, it can trigger an alarm or send an email message to facility managers in remote offices [36]. According to [PERSON] et al. [39], we distinguish two forms of infrared thermography--passive (stationary) and active (non-stationary). Active is one of the precise evaluation techniques of non-destructive testing, especially in the case of the aerospace industry for the inspection of aircraft and helicopters' primary and secondary structures, engine parts, composite materials, and subsystems. Passive infrared thermography is used to inspect a variety of materials, including aluminum and composites, which make up 50% of aircraft constructions. The most common aircraft failures are cracks, fatigue cracks, barely visible impact damage (BVDI), delaminations, disbonding matrix/fiber cracks, voids, water ingress, and core crushing. The passive form is usually used for materials that have a different temperature from the environment temperature in which they are operated; thus, this temperature can be captured by an IR camera [39]. [PERSON] et al. [40] claims that passive thermography can be used for the detection of water ingress just after aircraft landing when the temperature difference between the aircraft and water is significant. According to InfraTec [41], measurement tasks of the aerospace industry often require infrared cameras with very high thermal resolutions of 20 mk and/or a high frame rate of 100 Hz and more. The thermal cameras with such high sensitivity are also much bigger and heavier. Both weight and size are the major limitations that affect the usability of the camera for installation on UAV. The Mavic 2 Enterprise Advanced features a FLIR longwave infrared camera and a visual camera, providing both infrared and visible light imaging simultaneously. The FLIR camera provides high-sensitivity (<50 mK). Cameras with 50 mK are about 4 times as sensitive as a camera with 200 mK. The more sensitive cameras provide a wider temperature difference, resulting in more colors on the thermal display.