Tests of a 10-foot-diameter three-blade Curtiss 89301-15 propeller with Clark Y blade sections have been conducted in the Langley 16-foot high-speed tunnel in order to determine the effect of simulated iceon the aerodynamic characteristics of the propeller. The irregular coat of cement and fabric was used on the blades to simulate in outline and thickness a formation of glaze ice that might be formed in flight. The propellers were tested on a new 2000-horsepower dynamometer, a brief description of which is included. All tests were made at a rotational speed of 1800 rpm for blade angles of 20, 25, 35, and 40 degrees at the 42-inch radius and at airspeeds varying from 120 to 420 miles per hour. The results are representative of full-scale constant-speed propeller operation.