Sliding Mode Control (SMC) is one of the effective robust control techniques against external disturbances, parameter uncertainties and unmodelled dynamics. However, there is no certain way to design the sliding surface (SS) for nonlinear systems, which has a key role in satisfying the stability and performance criteria. Thus, an optimal method can be useful in the design process of SS to deal with these weaknesses. In this study, State Dependent Riccati Equation (SDRE) based SMC is used to control the motion of a laboratory helicopter in two axes, namely travel and elevation axes. Experimental evaluation is performed using this 3-DOF helicopter platform and results are compared against a SMC with linear time-invariant SS to establish the efficacy of the approach. Therefore, this study presents experimental investigation for establishing the feasibility of the proposed optimal robust control architecture.