The flight performance of a helicopter is significantly influenced by its aerodynamic interference characteristics. In this work, the numerical simulation technique utilizing the improved Delayed Detached Eddy Simulation (IDDES) method is applied to study the development of aerodynamic interactions under varied flight conditions and to systematically analyze the effects of flight velocity (magnitude and direction) on the aerodynamic interactions among the rotor blades, airframe, and tail rotor. Findings reveal that as the forward ratio increases, the rotor wake propagates rearward along the airframe and shifts toward the tail rotor area. The backward extension of the wake concurrently causes a steady reduction in surface load on the fuselage, particularly pronounced at elevated forward ratios. Changes in the helicopter’s velocity direction significantly affect the disturbance flow field distribution. During lateral deflections, the vorticity on the deflection side enhances and biases toward the tail rotor region, resulting in the tail rotor operating into a stronger wake. Additionally, variations in longitudinal angles markedly influence the vortex distribution across the rotor disk. As the oblique downward angle intensifies, the vortex on the upper surface of the rotor disk enhances and extends to the airframe’s tail and the tail rotor. Conversely, an increased oblique upward angle amplifies the vortex beneath the rotor’s airflow, expanding its impact zone on the airframe and significantly influencing the dynamics of both the airframe and tail rotor. The research provides an important basis for further optimizing helicopter aerodynamic design and improving flight performance.