The present work is an experimental study of an airfoil flapping and simultaneously moving forward in quiescent water in a tank. The focus here is to study using flow visualizations and PIV how the flexible flap attached at the trailing edge of a rigid airfoil affects the flow generation. The parameters that were varied were the frequency and amplitude of flapping and forward speed. The Strouhal number based on lateral excursion of the trailing edge is kept around 0.3 in all the experiments. We also briefly present the flow in the absence of free-stream velocity or forward speed (Strouhal number = ∞). © 2014: The Royal Institution of Naval Architects and IIT Madras.