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Sizing and optimization of the horizontal tail of a jet trainer

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2019
Karatoprak, Sinem
The sizing of the horizontal tail has a priority on the design phase. The horizontal tail provides a necessary longitudinal control and the sufficient static stability throughout the defined center-of-gravity (CG) range. The jet trainer of this study is a control-configured vehicle (CCV). The control system has a significant role in shaping the aircraft with the usage of active control technology (ACT). ACT introduces the concept of relaxed static stability (RSS) by providing artificial stability. The horizontal tail provides sufficient longitudinal static stability even at the most aft CG position. In order to determine whether an aircraft is stable, the determination of the static margin (SM) is one of methods. For a conventional aircraft, static margin is approximately 5 % in the subsonic regime. However, a large backward aerodynamic center (AC) shift occurs between subsonic to supersonic. This causes a large increase in static margin at supersonic flight regime which penalize the performance in terms of drag and weight. Therefore, the size of the horizontal tail is reduced by utilizing from RSS concept.Some stability and control derivatives- such as Cmα, Cmδ , CLδ -are needed to obtain during the evaluation of the control authority and stability of the aircraft. The evaluations are based on the defined certain parameters and force and moment equilibrium equations. Therefore, analyses based on Datcom and Computational Fluid Dynamics (CFD) were performed for six horizontal tails. CM, CL, and CD aerodynamic coefficients of each horizontal tail were calculated at different AoAs throughout flight envelope.