Evaluation of Vortex Ring State and Recovery Maneuver from It for TH135 Helicopter

Vortex ring state (VRS) is one of the most dangerous flight conditions for helicopters. This is a phenomenon in which a helicopter descends into its own downwash, creating a circular flow that causes a surge of power to generate sufficient thrust to hover. This paper examines the characteristics of the TH135, a training aircraft of the Maritime Self-Defense Force, when it enters this state and its recovery maneuvers from this state. Two recovery maneuvers, conventional and the recently proposed Vuichard recovery, were tested, and each maneuver is evaluated by altitude loss and pilot rating. As a result of the flight tests, the Vuichard recovery achieved recovery with less altitude loss compared to the conventional method, and no significant adverse characteristics were observed during the recovery maneuver.