Wind Tunnel Investigation of the Aerodynamic Effects of Aircraft Ground Deicing/Anti-Icing Fluids and Criteria for Aerodynamic Acceptance

A follow-on wind tunnel investigation of the aerodynamic effects of aircraft ground deicing/anti-icing fluids was performed to supplement earlier reported flight and wind tunnel tests and support the development of aerodynamic acceptance criteria for aircraft ground deicing/anti-icing fluids. The test was conducted at the NASA Lewis Research Center Icing Research Tunnel using both a 2D model and a 3D half model of the 737-200ADV airplane. The fluids that were tested included the following: three Type I Newtonian fluids, which use ethylene, diethylene, and propylene glycol as the freezing point depressant; four Type II non-Newtonian fluids, which are currently in production; eight developmental fluids; and a Mil Spec fluid to be used as a reference fluid in the aerodynamic acceptance test. The Type I and current Type II fluids were tested neat and diluted to determine basic aerodynamic effects. Dilution of the Type II fluids did not significantly alter the aerodynamic effects of the fluids. Diluting the Type I fluids did result in a significant reduction in the adverse aerodynamic effects of these fluids, especially at temperatures of -10 C and colder. Boundary layer displacement thickness, delta*, measurements made with the fluids on the 2D model show excellent correlation with lift loss due to the fluids at maximum lift and at operating angles of attack and with the boundary layer displacement thickness measured on a flat plate in the small von Karman Institute wind tunnel. This correlation validated the future use of flat plate boundary layer displacement thickness measurement as the criterion for the aerodynamic acceptability of a fluid. The limiting boundary layer displacement thickness, which identifies a fluid as being aerodynamically acceptable, is correlated with a loss in maximum lift that results in an allowed specific reduction in aerodynamic performance margins.