The objective of this research was to numerically study the effects of simulated spanwise-step-ice accretions (resulting from supercooled-large-droplet icing conditions) on subsonic aircraft aerodynamics. The investigations were performed with a high-resolution full Navier-Stokes code using a solution-adaptive unstructured grid for both non-iced and iced configurations. The airfoil investigated was a modified NACA 23012 with a simple flap. Simulated ice shapes were tested on the airfoil to determine the sensitivity of ice shape size on airfoil performance and control. Predictions of sectional aerodynamic characteristics for a quarter-round ice-shape heights of 0.0083 and 0.0139 chords are presented and compared with experimental data. Significant reductions in lift were noted for these relatively small protuberances, which was consistent with experimental findings. The results also indicate good predictive performance for drag, pitching moment, and hinge moment variations.