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.

Stability and Control of Airplanes and Helicopters deals with aircraft flying qualities that determine the stability and control of airplanes and helicopters. It includes problems based on real aircraft, selected to represent the gamut from simple to complicated, and from conventional utility designs to futuristic research types. Many of these problems involve comparison of theory and experiment to demonstrate their mutual relationship. Comprised of 25 chapters, this book begins with a discussion on the aerodynamics of the component parts related to the lift and moment characteristics of an airplane, including wings and associated accessories; bodies such as fuselages, nacelles, and tip tanks; and control surfaces. The reader is then introduced to some mathematical techniques for linear differential equations; steady flight at different speeds; and stick force and control-free stability. Subsequent chapters focus on flaps and high-lift devices; power and compressibility effects; and the manner in which the aircraft responds to the application of control. Aeroelasticity and longitudinal equations of motion are also examined. This monograph is intended for undergraduate and graduate students taking modern engineering courses.

A general theory of solid-state diffusion in strained systems is developed on a molecular-kinetic basis. The theory predicts that for simple strains the diffusion coefficient is an exponential function of the lattice parameter and that the rate of change of the diffusion coefficient with strain is linearly related to the interatomic forces. It has also been shown that for plastic flow the diffusion coefficient is a linear function of strain rate. All the conclusions are confirmed by the data available in the literature.

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.