APPLICATION OF ROTOR ICING ANALYSES TO THE DESIGN OF A ROTORCRAFT DEICING SYSTEM

Icing correlations developed from airfoil artificial ice accretion test data can aid in the prediction of rotorcraft and propeller performance for operation in icing conditions. The airfoil tests provided ice shape information and incremental force and moment coefficients for a variety of profiles, representing airfoils now used on production helicopters and planned for future rotorcraft. This paper summarizes the results of these tests and the formulation of relationships needed for the evaluation of aircraft performance for flight in icing conditions, and for the design of optimum electro-thermal and advanced deice systems. Increasing dependence on analysis will ultimately lead to a reduction in deice system development and qualification costs. This paper presents information that augments prior correlation efforts and shows how analysis can be applied to the prediction of natural ice shedding time and icing torque rise. The analysis was also used to predict climb capability with icing and the effect of an optimized deice system on payload-range characteristics. This paper also reports on experiments that show the effect of grit on a simulated rime ice shape and the effect of horn corner radius on a simulated glaze ice shape. A grit size to airfoil chord ratio of at least .0028 is needed to increase the drag coefficient to represent an airfoil with the natural roughness of real rime ice. Adding roughness on the airfoil leading edge behind the simulated ice can increase the drag coefficient further. A simulated glaze ice shape should have a horn corner radius to chord ratio of approximately .0063 to represent the drag of real glaze ice.