Visual inspection can reveal surface damage, but many serious structural defects develop within the blade. Subsurface inspection using ultrasonics can give operators earlier evidence of disbonds, delamination and other internal defects before repair options become more limited.
Drones and high-resolution cameras have changed how the wind industry inspects rotor blades. But looking at a blade is not the same as looking into one. As blades grow longer and root and spar-cap designs are subjected to greater loads, defects that can turn a repairable blade into a replacement may develop inside the laminate, out of sight and only reach the surface once repair options have become more limited.
The case for subsurface structural inspection is therefore to make it a routine part of blade operations & maintenance (O&M) rather than a step taken only after something has already gone wrong.
What the cameras can’t see
Automated visual inspection is highly effective for surface condition assessment. A drone can image a full blade quickly and flag leading-edge erosion, coating breakdown, surface cracking and lightning damage without requiring a technician on ropes. For failure modes visible at the surface, it remains an important inspection tool.