A high-speed icing wind tunnel test program was conducted to measure the ice growth and performance degradation on 10 rotorcraft airfoil models for ranges of liquid-water content, temperature, and Mach number at several steady and unsteady angles of attack. Prior to these tests, airfoil icing data had been acquired only in low-speed tunnels or during flight testing, but high-speed data are necessary for the prediction of icing on rotors. The test explored the boundaries for the onset of icing and between glaze and rime ice. Ice shapes were documented and lift, drag, and pitching moment were measured. Airfoil lift was reduced slightly at low angles of attack and about 20% at high angles. Drag increased in moderate icing at low angles of attack by a factor of three to four, increasing for higher liquid-water contents and angles above 6 deg. The effect of Mach number varied. Airfoil oscillation did not change the lift loss, but did reduce the drag penalty. Two-dimensional airfoil icing relationships for ice thickness and for changes in lift, drag, and pitching moment coefficients were formulated, with improved accuracy over prior relationships. These relationships have been used to predict aircraft power changes during icing. 7A Pi T Nomenclature = air foil chord, m = drag coefficient = lift coefficient = pitching moment coefficient = droplet diameter, /mi = total airfoil collection efficiency = roughness height-to-chord ratio = modified inertia parameter = empirical constants = ice height, m = ice adhesion width (interior ice thickness), m = freestream Mach number = airfoil leading-edge radius-to-chord ratio = ice thickness, m = airfoil thickness-to-chord ratio = corrected temperature, °C = glaze ice boundary static temperature (r glaze ), °C = onset of ice static temperature, °C = rime ice boundary static temperature, °C = static temperature, °C = local velocity, m/s (ft/s) = helicopter forward flight speed, km/h (knots) = liquid water content, g/m 3 = airfoil angle of attack, deg = ratio of specific heats = incremental quantity = ice density, kg/m = icing time, s = corrected icing time, s Presented as Paper 85-0337 at

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Items that disturb the otherwise smooth flow of the air over the surface of an airplane create excrescence drag. For general aviation airplanes, the relative scale of the disturbance to the overall size of the airplane is much larger than for a commercial transport. This makes the effect of excrescence items much larger than for commercial transports. Handbook methods exist to estimate basic parasite drag and excrescence drag created by airframe and equipment items.