The objective of this research was to study the effects of spanwise-step-ice accretions (resulting from large droplet icing conditions) on subsonic aircraft aerodynamics. The airfoil investigated was a modified NACA 23012 with a simple flap. An experimental and computational program was conducted using simulated ice accretions to determine the sensitivity of ice shape size and location on airfoil performance and control as a function of angle of attack and flap deflection. Focus is paid on the critical conditions where the aerodynamic performance, and the hinge moment in particular, changes rapidly and non-linearly. The experimental program included wake surveys, surface pressure taps, and force-balance measurements to obtain lift, drag, pitching moment, and hinge-moment coefficients for a large variety of geometry and flow conditions. The accompanying computational investigation was performed with a high-resolution full Navier-Stokes solution using a solution-adaptive unstructured grid for both non-iced and iced configurations. Results are presented for experiments and predictions of sectional aerodynamic characteristics where the quarter-round ice shape heights of 0.0083 and 0.0139 chords resulted in a dramatic decrease in maximum lift coefficients as well as significant reductions in hinge moments for positive angles of attack.