One Saturday morning, at around 8 a.m., a blade broke off from a wind turbine at a wind farm. The operator received a warning of a nacelle positioning problem stopping the machine at around 11 a.m. At around 12 p.m., an emergency response team noted that fibreglass had been torn from the trailing edge of one of the turbine’s 3 blades. Technicians feathered the blades and placed the defective blade facing downward. The rotor was mechanically blocked. The operator secured the area, in particular by signage and elimination of the risk of falling parts. It stopped the other wind-farm turbines.

Fibreglass blades were found 30m from the machine and fragments as far as 150m away. The operator grouped all the debris in a dedicated container before the appraiser’s visit and until they were taken charge of by a company capable of recycling the components and not incinerating them.

Following an analysis of the condition of the blade, a third-party expert noted a bonding defect, due either to the glue’s distribution or the glue’s quality. He recommended a physical inspection of the blades within six months. The precursory signs of weakening were not detected during inspection maintenance. This would apparently be slow failure kinetics. The operator noted that the machine was equipped with an insufficient number of detectors, notably for unbalance and slope. In particular, no wind-turbine remote supervision system was able to confirm the blade’s fall. The event was detected on the site after several hours.

The operator initiated repair operations on the defects visible on the surface of the other blades and performed thermal imaging of all the blades. The Classified Facilities Inspectorate made restarting of the wind turbine involved conditional on determination of the causes of the incident and restarting of the other wind turbines conditional on a very stringent inspection of the blades’ condition. The wind turbine was restored to operation 4 months later after replacing the blade and performing safety tests. The operator agreed to install additional detectors capable of identifying this type of damage within six months and performed closer inspections by drone in the meantime.