EXPERIMENTAL DETERMINATION OF THE EFFECTS OF FREQUENCY AND AMPLITUDE ON THE LATERAL STABILITY DERIVATIVES FOR A DELTA, A SWEPT, AND AN UNSWEPT WING OSCILLATING IN YAW

Three wing models were oscillated in yaw about their vertical axes to determine the effects of systematic variations of frequency and amplitude of oscillation on the in-phase and out-of-phase combination lateral stability derivatives resulting from this motion. The tests were made at low speeds for a 60 deg delta wing, a 45 deg swept wing, and an unswept wing; the latter two had an aspect ratio of 4. The results indicate that large changes in the magnitude of the stability derivatives due to the variation of frequency occur at high angles of attack, particularly for the delta wing. The greatest variations of the derivatives with frequency take place for the lowest frequencies of oscillation; at the higher frequencies, the effects of frequency are smaller and the derivatives become more linear with angle of attack. Effects of amplitude of oscillation on the stability derivatives for the delta wing were evident for certain high angles of attack and for the lowest frequencies of oscillation. As the frequency became high, the amplitude effects tended to disappear. The algebraic addition of the component derivatives determined in separate investigations were generally in good agreement with the combination derivatives obtained herein. The major contributions to the out-of-phase derivatives are made by the sideslipping acceleration derivatives, whereas the in-phase derivatives are determined chiefly by the sideslipping velocity derivatives.