NACA-RM-L8G19

Abstract

INTRODUCTION <br>When an airplane rotates about a lateral axis, as when entering climbing or diving flight, there are, in addition to the initial static forces and moments acting on the airplane, forces and moments resulting form the pitching motion of the airplane. The rotary stability derivatives associated with these additional forces and moments must be known before calculations can be made to determine the longitudinal dynamic stability of the airplane or the longitudinal motions of the airplane after a control displacement. Experimental determinations of these derivatives have been made by oscillating models in wind tunnels and by rotating models on whirling-arm devices. (See references 1 and 2.) Both of these test procedures gave results for the damping in pitch but could not be conveniently used to determine the other pitching derivatives. All the pitching derivatives can be determined rather simply, however, by the use of a test procedure wherein the model remains fixed and the air stream is curved. This method of testing is now being used at the Langley stability tunnel where a comprehensive investigation is being conducted to determine the rotary derivatives of wings of various plan forms. <br>The present paper contains the results of that part of the investigation that involved the testing in pitching flow of ten untapered wings of various aspect ratios and angles of sweep. Also included herein is a comparison between experimental data and available theory.