NACA-RM-L57F07

Abstract

INTRODUCTION <br>Recent developments have shown that stability derivatives obtained from oscillation tests can be considerably different from those obtained by steady-flow tests for some angle-of-attack and mach number ranges (refs. 1, 2, and 3) and that these differences can be quite important in the calculation of the stability and motions of an airplane (ref.4). It was also found that the magnitude of these measured oscillatory derivatives depended to a large extent upon the frequency and amplitude of the oscillatory motion (ref. 5). <br>A common and widely used oscillation technique is one wherein the model is simply oscillated about a fixed vertical (Z) axis relative to the model. These tests are commonly called oscillation-in-yaw tests, and yield a derivative that is a combination of two terms; for example, the damping term consists of the damping in yaw cnr and an acceleration in sidesip term cn in the combination c_nr-c_n&#946;. However, in the equations used for calculating the airplane motion, these two derivatives are needed separately. Techniques have recently been developed at the Langley stability tunnel which will permit the measurement of the yaw and sideslip terms independently. Oscillatory tests in pure yawing, as described in reference 6, involve a snaking motion in which there is no sideslip, and oscillatory tests in pure sideslip involve a side-to-side motion in which there is no rotation (ref.3) <br>Presented in this paper is a low-speed investigation of pure sideslipping motion on a 600 delta wing along and in combination with a fuselage and vertical tail. The range of reduced frequencies of oscillation varied from 0.066 to 0.218 at a maximum amplitude of sideslip of +20, and the angle of attack varied from 00 to 3320. For comparison with the wing which had an NACA 65A003 airfoil section, a flat-plate 00 delta wing also was tested in sideslipping motion. In addition to the sideslipping tests some results are reported for oscillation-in-yaw tests (e.g., C_nr-c_n&#946; derivative) for both of the winfs. Computations of the period and time to damp to one-half amplitude were made using the measured oscillation sideslip data. These computations were made for a typical delata-wing airplane