On May 4, 2018, about 1155 central daylight time, a Robinson R44, N444VH, experienced a loss of engine power during taxi at East Troy Municipal Airport (57C), East Troy, Wisconsin. The helicopter sustained substantial damage to the main rotor. The student pilot and instructor were not injured. The helicopter was registered to and operated by a corporation under the provisions of Title 14 Code of Federal Regulations Part 91 as a training flight for Part 137 agricultural operations. Visual meteorological conditions prevailed for the flight, and no flight plan was filed.