The realization of a wind turbine as a source of clean, non-polluting and renewable energy may depend on the optimum design of turbine blades that can operate efficiently under extreme variations in wind conditions. In this paper we provide results of an experimental investigation to examine the effectiveness of a highly loaded theory for the design of a horizontal axis wind turbine for optimum power production over a wide range of advance ratios. We find the theory, which can be used to set up design curves easily and requires only hand held calculator for calculation, offers a rational basis for the design of propeller wind turbines for peak performance.