Evaluating Longitudinal Unsteady Aerodynamic Effects in Stall for a T-Tail Transport Model

• Published in: Journal of aircraft 2022-07, Vol.59 (4), p.964-976
• Main Authors: Nguyen, Duc H., Goman, Mikhail G., Lowenberg, Mark H., Neild, Simon A.
• Format: Article
• Language: English
• Subjects: Aerodynamic characteristics; Aerodynamic stability; Aerodynamics; Aircraft; Aircraft performance; Bifurcations; Control stability; Delta wings; Flight characteristics; Modelling; Stability analysis; Stalling; State space models; Transport aircraft; Unsteady aerodynamics
• ISSN: 1533-3868; 0021-8669; 1533-3868
• DOI: 10.2514/1.C036622

Although there have been many proposed methods to model unsteady aerodynamic effects in the stall and poststall region, little work has been done to directly assess the impact of unsteady aerodynamic models on stability and control characteristics. In this paper, the state-space method for unsteady aerodynamic modeling is combined with bifurcation analysis to examine the sensitivity of stall and poststall behavior to the choice of aerodynamic modeling method: quasi-steady or unsteady. It is found that quasi-steady modeling can adequately capture the dynamics of the chosen example of a T-tailed transport aircraft with negligible wing–tail coupling. The study is then expanded to investigate a hypothetical situation with highly unsteady aerodynamic characteristics resembling a delta wing configuration—achieved by increasing the time delay constants in the unsteady model. This results in an aircraft with significantly lower flying qualities as indicated by bifurcation analysis. These findings highlight the need to implement unsteady aerodynamic modeling techniques in high-performance aircraft with significant vortex-related unsteady aerodynamics in order to sufficiently capture their stall and poststall dynamics.