## 5 Results and Discussion
### Description of the Structural Test  
To assess the feasibility of the application of AIoT networks in aeronautical structural testing, a real case of fatigue testing of a real aircraft component has been considered. The tested specimen is a moving component that links the aircraft structure with the aerodynamic flap surface, and is in charge of extending the flap over the fuselage for low flight speed regimes and retracting it for high speed regimes. This component plays a very important role in the operation of the aircraft and its correct operation must be guaranteed for a minimum number of flights defined by the aeronautical authorities. Figure 9: Graphical representation of the values measured during the calibration of the edge node sensors: (**a**) values measured by the position sensor, (**b**) values measured by the temperature sensor, (**c**) values measured by the inclination sensor. This component has a rotating mechanism driven by an electric motor, which, through a gearbox, moves a carriage located on a guide (Figure 10a). This carriage is attached to the flap in the final assembly and is the one that places it in its correct position. During flight operations, this component, in addition to supporting the weight of the flap attached to it, must also withstand heavy aerodynamic loads transmitted by the flap as a result of the air flows over it. The test specimen contains only the moving mechanism with the carriage and guide, and the gearbox that produces the carriage movement. The flap to which it is attached in the operation is not available during the test. However, both the static and aerodynamic effects of the flap are taken into account in the test by applying load profiles at different points of the specimen and at different instants. Therefore, the fatigue test consists of repeating the extension-/retraction movement that the component performs in operation while applying combinations of mechanical loads at different points in order to reproduce flight conditions in a simulated manner and a certain number of times. These load profiles are defined by the component manufacturer together with the DOA organization. They are obtained by means of numerical FEM simulations and are representative of the mechanical stresses to which the specimen will be subjected to in flight. In the specific case of the specimen tested, the number of times the load profiles have to be repeated is such that the complete test lasts several months. The transitions between consecutive loading conditions in the profiles are performed at a reduced speed of the same order that will be produced in the operation, with the average time between consecutive loading conditions being approximately 4 s. Upon reaching each load condition, measurements of different magnitudes are taken to evaluate the integrity and correct operation of the specimen. The magnitudes measured in this test are the position of the  
Figure 10: Magnitudes of interest in the test and the sensors used to measure them: (**a**) Schematic representation of the function of the tested component, (**b**) location of the inclination sensor, (**c**) location of the position sensor, (**d**) location of the temperature sensor. carriage, the inclination of a rod attached to the moving part, and the temperature of the gearbox. These measurements are carried out by means of conventional wired sensors, which have been previously calibrated and approved by the component manufacturer. To evaluate the feasibility of the proposed AIoT network, a prototype with the developed measurement modules has been built and placed in areas close to the conventional wired sensors. In this way, data have been recorded with the wireless sensors of the same magnitude as the official sensors, which could be compared with the wired sensor readings without interfering with the official measurements. Module 2 was placed on the side of the specimen, and the inclination and temperature sensors were placed next to the corresponding conventional sensors (Figure 10b,c).