Lifting-Line Estimation for the Contribution of a Conventional Tail to Aircraft Lateral Stability Derivatives

Abstract

* Currently Research Engineer, Lockheed Martin Missile and Fire Control Orlando. Senior Member AIAA. † Professor, Mechanical and Aerospace Engineering Department. Member AIAA. Abstract The low-speed lateral stability derivatives for a conventional airplane are significantly affected by the vortex interaction between the horizontal and vertical stabilizers. A numerical solution to Prandtl’s liftingline theory can be used to account for this interaction. The accuracy of this lifting-line solution is evaluated by comparison to wind tunnel measurements. Section and total force coefficients were obtained by integrating surface pressure measurements on an empennage model over a range of sideslip angles for two vertical stabilizer aspect ratios. All surfaces had rectangular planforms, NACA 0015 airfoil sections, and were tested at a chord Reynolds number of 4.4x10. The measured coefficients were compared with numerical lifting-line predictions for the same geometry. Results are presented that show good agreement between the numerical predictions and the measured values. The effects of aspect ratio and sideslip angle on the section force, total force, and rolling moment coefficients are accurately predicted. The rolling moment generated on the horizontal stabilizer, which results only from its interaction with the vertical stabilizer, is presented. The numerical method is also shown to be accurate in predicting wind tunnel wall effects by utilizing the method of images.