Investigation at Low Speeds of the Effect of Aspect Ratio and Sweep on Static and Yawing Stability Derivatives of Untapered Wings

摘要

A low-scale wind-tunnel investigation was conducted in both straight and yawing flow to determine the effects of aspect ratio and sweep (when varied independently) on the static and yawing stability derivatives for a series of untapered wings. The curved-flow equipment of the Langley stability tunnel was used for the tests. The effects of sweep on the static stability characteristics, namely, lift-curve slope, drag, and the effective-dihedral parameter, generally became smaller as the aspect ratio decreased. For constant sweep angle, the magnitude of the damping in yaw decreased with an increase in aspect ratio for the low lift-coefficient range. At some moderate lift coefficient, this derivative changed sign (became positive) for the 45 degrees and 60 degrees swept wings. For unswept wings, the experimental data indicated that the rolling moment due to yawing is very nearly proportional to the lift coefficient until maximum lift is attained. For the sweptback wings, linear variations of rolling moment due to yawing were obtained over only a limited lift range; at high lift coefficients, the values of the rolling moment due to yawing decreased and in some instances became negative near maximum lift. The rate of change of rolling moment due to yawing with lift coefficient usually increased with both sweep and aspect ratio for the low lift-coefficient range. In general, the data at low and moderate lift coefficients were in fair agreement with a simple sweep theory.