Those choppers Mainers hear overhead may be power line inspectors. Central Maine Power is performing its autumn inspections of its transmission lines by helicopter. The twice-yearly flights help spot potential problems with equipment, as well as signs of unauthorized use. This helps ensure safe, reliable delivery of power. CMP, a subsidiary of Iberdrola USA, does a visual inspection of all of its transmission rights-of-way from the air each spring and fall. In addition to those inspections of its entire transmission system, CMP also flies over more than 600 miles of transmission lines during the summer using a helicopter equipped with infrared thermal imaging equipment to detect “hot spots” that might need attention. CMP owns nearly 2,200 miles of transmission line.