This Aerospace Information Report (AIR) identifies and summarizes the various factors that should be considered during design, development, certification, or testing of helicopter rotor blade ice protection. Although various concepts of ice protection are mentioned in this report, the text is limited generally to those factors associated with design and substantiation of cyclic electrothermal ice protection systems as applicable to the protection of helicopter rotor blades. Other systems are described briefly in Appendix A. Applications consider main rotor blades, conventional tail rotor blades, and other types of antitorque devices. The information contained in this report is also limited to the identification of factors that should be considered and why the factor is important. Specific design, analysis and test methodologies are not included. For additional information refer to the references in Section 7.