Wind turbine drone inspection: what it shows, what it misses and what it is really for

Drone inspection of wind turbines has become standard practice in the industry: a camera a few metres from the blade sees what nobody sees from the ground, without sending anyone up and with the machine stopped for hours rather than days. But "drone inspection" means different things depending on who sells it, and it pays to be clear about what you are buying.

What a visual drone inspection sees

• On the blades: leading-edge erosion, visible cracks, paint chipping, impacts, lightning damage at the receptors, soiling and its distribution, and the condition of add-ons (vortex generators, serrations).
• On the tower: oil streaks, coating condition, corrosion at externally visible welds and flanges, paint damage.
• On the nacelle: visible leaks at seals and breathers, housing condition, soiling.
• On the hub: grease leaks and the condition of the spinner.

All of it ends up as high-resolution photographs per machine and per component, which are the basis of the report. It is, therefore, an exterior visual inspection.

What it does not see

What is inside the material. Internal delamination, a laminate defect or the electrical continuity of the lightning protection system cannot be seen with a camera. Those need contact testing: active thermography, ultrasound, lightning protection measurement, tap testing. A technician does those on the blade, by rope or platform, and no drone inspection replaces them.

Nor does it see well in poor light, rain or strong wind, exactly like a cleaning. And a very dirty blade hides defects: that is why an inspection gives more when the machine is clean, or when it is done in the same visit as the cleaning.

What it is really for

For deciding where to send people. If a fleet of forty machines is inspected by drone in a few days, the rope team climbs only the four or five that need it, instead of all forty. It is a prioritisation tool, and that is how O&M teams that have adopted it use it.

It also serves as a record: an annual photographic inspection lets you compare the same blade year on year and see whether a defect is progressing. The annual visual check of blades and lightning protection is standard practice in the industry, and a drone is today the cheapest way to do it.

How we do it

At Eolinet the visual inspection is included in every clean: the same flight that cleans photographs each machine before and after. And we offer drone inspection as a stand-alone service, with photographic reporting per machine. What we do not do, and we say so, is contact testing: if the inspection finds something that requires touching the blade, we flag it so that whoever is responsible can do it.