The Adverse Aerodynamic Impact of Very Small Leading-Edge Ice (Roughness) Buildups on Wings and Tails

Systematic experimental studies were performed to establish the aerodynamic impact of very small leading-edge simulated ice (roughness) formations on lifting surfaces. The geometries studied include single element configurations (airfoil and 3-D tail) as well as multi-element 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 was 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 ice build up (i.e., distributed roughness). It was also found that allowing initial ice formations of a size required for removal by presently proposed deicing systems could lead to maximum lift losses of approximately 40 percent for single-element airfoils. Losses in angle-of-attack margin to stall are equally substantial - as high as 6 degrees. Percentage losses for multi-element airfoils are not as severe as for single-element configurations, but degradations of the angle-of-attack-to-stall margin are the same for both.