Studies of High Speed Airplanes

Abstract

The authors have devised a series of high speed design studies in which several advanced ideas and innovations are proposed. The factors having an important influence on high speed are considered and the airplane design arrangements are so proportioned as to minimize adverse effects, to the lowest values which are believed attainable without fundamental changes involving the invention of new principles of flight now unknown or undeveloped. Data are presented showing the lowest values of the drag of the component parts of a modern airplane, which represent current practices. Further data are given to show possible improvement in these values and the ones that may be entirely eliminated. An analysis of the factors influencing propeller design for high speed aircraft is made, together with a prediction of the propulsive efficiencies which may be obtained, based on recent research. The maximum attainable efficiency becomes less as the speed and altitude are increased. Possibilities of increasing the indicated optimum propulsive efficiencies and the desirability of a variable gear drive device, are discussed briefly. The paper concludes with the familiar presentation of a chart showing the advance in high speed by years, which is extrapolated on the basis of the authors ' studies to show a prediction of the maximum speed attainable with aircraft designed according to conventional practices. This maximum speed is considered attainable within two years. T authors have prepared this paper and present it from the point of view of the practicing designer and aerodynamicist. The contents represent studies of airplanes made in the manner employed in design offices, making use of the results of the authors' work with wind tunnel and flight tests. Rather than approach the subject in general terms or by a mathematical development it was decided to explore the high speed possibilities of the future by a study of an airplane design, with some systematic variations of gross weight, wing loading, and power. The prerequisites for maximum speed are well established and most of the factors have been discussed by other authors.' The factors used as a basis for the present design studies are (1) high wing loading; (2) entirely enclosed power plant; (3) selection of optimum propeller, arranged as a pusher; (4) mid-wing and tail arrangement with elimination of unfavorable interference; (5) a cabin and windshield enclosed within the normal contour lines of the fuselage; (6) a finely streamlined fuselage shape; (7) smooth body, wing, and tail surfaces with the suppression of all excrescences, wrinkles, rivet heads and skin laps; (8) Presented at the Aerodynamics Session, Eighth Annual Meeting, I.Ae.S., New York, January 26, 1940. Speed Airplanes