Effects of Vertical Tail and Inlet/Strake Geometry on Stability of a Diamond-Wing Fighter Configuration

Abstract

th -generation fighter. Models were tested with five different vertical tail configurations and five inlet design variations. The tail configurations differed only in the lateral spacing of the twin vertical stabilizers. The inlet design variations varied with leading edge sweep and inlet length. Water tunnel flow visualization was utilized for both tests to characterize vortex trajectories, relative strengths, and bursting locations, as angle of attack and sideslip are varied. These results revealed that at sideslip angles of 10 degrees or less all configurations were free from chine and leading-edge-generated vortices impacting the vertical tails. Flow visualization of different inlet configurations showed a large degree of variation in the downstream flowfield. At higher angles of attack, extended inlet/strakes provided the longest of sustained vortex structure. Wind tunnel testing yielded lift and drag curves, as well as static stability derivatives for different tail and inlet configurations. Tests revealed that above six degrees angle of attack, the effect of tail configuration on directional stability was negligible. Wind tunnel testing also showed that extended inlets provided for increased lift at higher angles of attack and improved lateral- directional static stability. The stability of the tested aircraft configuration was undesirable and further changes to the configuration are recommended.