The new wind tunnel of the Air Service Engineering Division has for object to afford the service more convenient aerodynamic testing facilities than have hitherto been available. The aircraft designer obtains much of his aerodynamic data using wind tunnels. The method involves small-scale models of any desired design, which are subjected to an artificial air blast, and the resulting air forces measured by a balance. The coefficients of "Lift", "Drag", etc., are thus determined, and may be applied to aircraft when suitably corrected for scale effect. Practically, we have not yet attained a tunnel greater than one-sixth scale. Evaluation of the "scale effect" at high velocities is not yet satisfactorily understood, nor will it be until our fund of knowledge of high-speed phenomena is increased. This document describes the design and construction of the 5-foot wind tunnel constructed at McCook Field.