The effect of simulated icing on propeller performance

Abstract : Teats 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 ice on the aerodynamic characteristics of the propeller. An 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 teats were made at a rotational speed of 1800 rpm for blade angles of 20, 25, 30 35, and 40 deg 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. The simulated icing condition caused a decrease in peak efficiency of 2.5 to 3.0 percent; this decrease was a result of a loss of blade section lift and increase of blade section drag. The characteristics of a propeller similar to the one tested were calculated from airfoil data obtained on a wing with and without simulated ice. The calculations indicate a probable loss of peak efficiency of 5.0 percent, which is in fair agreement with the test results. Inasmuch as operation of the entire airplane is affected adversely by ice formation, the airplane when iced may be forced to attempt to climb at relatively low speed and at a high value of thrust coefficient. For this condition the calculations indicate that the propeller efficiency may be about 15 percent less than for an un-iced propeller.