Aerodynamic Performance Effects due to Small Leading-Edge Ice (Roughness) on Wings and Tails

Systematic experimental studies have been carried out to establish the aerodynamic impact of very small leading-edge simulated ice (roughness) formations on lifting surfaces. The geometries studied include singleelement configurations (airfoil and three-dimensional tail) as well as multielement high-lift airfoil geometries. Emphasis in these studies was placed on obtaining results at high Reynolds numbers to insure the applicability of the findings to full-scale situations. It has been found that the well-known Brumby correlation for the adverse lift impact of discrete roughness elements at the leading edge is not appropriate for cases representative of initial frost formation (i.e., distributed roughness). It has further been found that allowing initial ice formations, of a size required for removal by presently proposed de-icing systems, could lead to maximum lift losses of approximately 40% for single-element airfoils. Losses in angle-of-attack margin-to-stall are equally substantial— as high as 6 deg. Percentage losses for multielement airfoils are not as severe as for single-element configurations, but degradations of the angle of attack-to-sta ll margin are the same for both.