I spent several months working out of a helicopter in the arctic in 1987. There was a period of a few weeks where we were taking off and landing in clouds of "moose flies" as the locals called them. They WERE huge, but they were not made of steel, and yet there was a lot of concern that the rotor blades were being damaged badly. Every day after finishing our work, the engineer would inspect the leading edges and cringe, telling us that he may have to replace them at some outrageous $ figure.