Turbine blade erosion sensor

A system for monitoring erosion of a coating on a turbine blade, comprising:

• a plurality of conductive sensors disposed in the coating of the turbine blade, the conductive elements comprising a first element of corrosion resistant material having similar erosion properties to the coating of the turbine blade and a second element of a corroding material having similar erosion and corrosion properties to the coating of the turbine blade;
• and
• an electrical property monitoring device configured to monitor an electrical property associated with each of said plurality of conductive elements, said electrical property monitoring device providing a signal when one of said plurality of conductive elements has been modified due to erosion;
• wherein the system provides an erosion depth indicator based at least in part on the number of said plurality of conductive elements that have been modified due to erosion.