Aeroelastic Rotor-Empennage Interactions and Design Sensitivities for T-tail Architectures

T-tail architectures show potential for enhancing vertical tail-efficiency and lowering fuselage download and hub load cycles during low-speed transition. However, a horizontal stabilizer is principally susceptible to rotor wake impingement during cruise flight, which, in unfavorable conditions, could induce dynamic loads along with associated vibrations and structural fatigue. Predicting this phenomenon is challenging due to the complex aerodynamics and sensitive structural dynamics involved. This paper demonstrates the capabilities of a mid-fidelity simulation methodology for predicting empennage structural loads and vibrations. The approach utilizes mid-fidelity interactional aerodynamics modeling, building upon previously published Vortex-Lattice Model (VLM) results and extending them to include a Viscous Vortex Particle Wake (VVPM) analysis, coupled with a modal structural dynamics model of the fuselage. The study extends the simulation model's validation against experimental data across various flight states and sensors, incorporating a sensitivity analysis of the aerodynamic modeling. Additionally, the work presents flight state sensitivities, as well as design sensitivity studies examining the influence of main rotor blade number and T-tail planform. The results indicate that the mid-fidelity tool chain is a valuable industrial asset supporting the aeroelastic and aeromechanical design of airframe tailplanes affected by interactional effects. It allows efficient analyses with adequate numerical accuracy over a large range of operating conditions on the one hand and covering a variety of architectural choices on the other hand in view of vibratory loads and tailplane vibrations. The sensitivity study demonstrates the advantages of a high number of main rotor blades and a swept T-tail planform design for reducing vibratory loads, considering both, aerodynamic excitation and structural response.