A rope break immediately following a tow-assisted takeoff creates a critical flight scenario in which the pilot is faced with a decision of performing an off-field landing or attempting a 180-degree turn to land downwind on the runway. The selection of which type of landing the pilot should perform is commonly made based on whether the rope break occurs either above or below a decision altitude. However, the selection of an appropriate decision altitude is typically set based on standard operating procedures, which can vary depending on the airport environment and the pilot experience. In the current study, a simulation of the aerodynamic performance of a sailplane using the quasi steady flight equations of motion was developed and used in a gradient-based optimization algorithm to obtain the flight conditions that will result in the minimum possible rope break altitude for which a return trajectory to the runway is theoretically possible. In addition, the effect of a wind field was also considered in the simulation. Two sailplanes were used in the study, namely the SGS 1-26 and the SGS 2-33, which allowed the sensitivity in the resulting optimal trajectory to be analyzed with respect to the sailplane performance parameters. Lastly, a flight test campaign was performed using both sailplanes to empirically model the turns and to validate the performance simulation.