To suppress two-dimensional load sway caused by the horizontal boom motion of a rotary crane, both horizontal and vertical boom motions are generally used. However, it would be more energy efficient and safer if a control scheme were developed that only used horizontal boom motion, eliminating the need for any vertical boom motion. In addition, if we can suppress load sway without the need to measure it, reduction in the cost of sensors can be achieved. Furthermore, use of simple velocity trajectory patterns such as an S-curve acceleration/deceleration pattern, which are widely used in industrial automation systems, may provide cost-effective implementation of controllers. This paper presents the analytical conditions for a simple S-curve trajectory of horizontal boom motion to suppress residual load sway without sensing it. Numerical simulation results demonstrate the effectiveness of the proposed conditions.