Study on the Vortex Ring State of Helicopter and Flight Training Operation

Abstract

Vortex ring state (VRS) is an inherently unsteady aerodynamic phenomenon. For rotor operations in the VRS, an inherent unsteadiness is a characteristic of the flow state, which is reflected by the waves and knots produced on the tip vortex filaments. Operationally, entry into the VRS manifests as rotor thrust fluctuations and also an increase in the average rotor shaft torque, the latter which is necessary to overcome the higher induced aerodynamic losses associated with rotor operations inside its own wake. Arming to the flight safety, the VRS development is discussed, the VRS models are summarized, and the operations for flight out VRS are given at the end of this paper. It is helpful to helicopter flight and training.