Abstract: The unsteady aerodynamic interaction between the helicopter rotor and horizontal tail is particularly pronounced during low-speed flight, which can induce strongly nonlinear loads and significantly affect longitudinal stability and handling qualities. Existing ap-proaches struggle to balance accuracy with efficiency and often rely on closed-source foreign tools, limiting their application in full-envelope flight dynamics and control. This paper proposes an efficient reduced-order modeling method that integrates an inde-pendently developed Viscous Vortex Particle Method (VPM) with system identification techniques. Based on high-fidelity VPM wake data, a unified workflow—"VPM simulation–frequency response analysis–system identification"—is employed to construct a rotor/horizontal tail interaction model. This model uses wake skew angle as a unified independent variable and is expressed in trans-fer function form, incorporating three-dimensional sampling point synthesis and a time-delay mechanism to explicitly capture the non-uniform dynamic disturbances acting on the horizontal tail. Validation results show that within the core frequency range of flight dynamics (<10 rad/s), the maximum discrepancy between the model and wind tunnel tests is 8.7%. The computational cost for a single rotor revolution is approximately 0.224 milliseconds, representing an improvement of over four orders of magnitude com-pared to the full VPM simulation, thereby meeting real-time simulation requirements. The proposed method exhibits strong generali-zation capability in theory and engineering applicability, providing efficient and reliable aerodynamic interaction modeling support for high-fidelity digital flight dynamics modeling and intelligent flight control of helicopters.

Key words: Helicopter, Rotor/horizontal tail Aerodynamic interference, Viscous vortex particle method, Dynamic inflow model, System identification, Real-time simulation