Investigation of the Longitudinal Stability of the T-45A withComputational Fluid Dynamics

Wind tunnel and flight tests of the T-45A aircraft have identified a transonic region of reduced longitudinal stability. Wind tunnel results established the phenomenon as a flow interaction between the wing-body and the horizontal tail; however, insufficient data existed to determine the mechanism causing the reduced stability. Computational Fluid Dynamics (CFD) analysis of the T-45A in the transonic region identified the source of the reduced stability to be an increase in downwash on the horizontal tail caused by mid-span vorticity shed from the wing.