Air-flow characteristics behind wings and wing-body combinations are described and are related to the downwash at specific tail locations for unseparated and separated flow conditions. The effects of various parameters and control devices on the air-flow characteristics and tail contribution are analyzed and demonstrated. An attempt has been made to summarize certain data in a form useful for design. The experimental data herein were obtained mostly at Reynolds numbers greater than 4 x 105 and at Mach numbers less than 0.25.

Available wind-tunnel data on the low-speed horizontal-tail contribution to the static longitudinal stability of high-speed airplane configurations incorporating unswept and sweptback wings are reviewed and analyzed. The characteristics of the flow behind wings and wing-body combinations are described and related to the downwash at specific tail locations for unseparated flow conditions. The effects of variations of tail position, variations of wing plan form and airfoil section, trailing-edge flaps, stall-control devices, and ground interference on the air-flow characteristics and tail contribution are analyzed and demonstrated. The more favorable tail arrangements are emphasized and their application to specific configurations is illustrated. The analysis of the factors affecting the horizontal-tail contribution is, for the most part, descriptive; however, an attempt has been made to summarize certain data by empirical correlation or theoretical means in a form useful for design.

Wind-tunnel results are presented to show the effect of changes in horizontal-tail location on the low-speed static longitudinal stability and steady-state rotary damping in pitch for a complete model with wing and tail surfaces having the quarter-chord lines swept back 45 degrees.