Exit From Vortex Ring State - A Comparative Study Of Different Recovery Techniques

Abstract

In this study, different recovery methods for exiting from different phases of vortex ring state are compared with respect to loss of altitude and piloting complexity. The investigation is based on maneuver simulations carried out by a coupled flight mechanics - free-wake-code simulation environment, including an autopilot for a detailed model of the BK117 D-3 in comparison to flight test data. The maneuver simulations comprise the phase of entering the vortex ring state from hover over incipient vortex ring state, up to deep vortex ring state with a high, but constant rate of descent. This is followed by the application and comparison of four different recovery techniques: Traditional, Power-assisted, Vuichard, and Pulling collective only, each with equivalent input strokes. The methods are compared with respect to effective altitude loss and piloting complexity. Within all successful recovery maneuvers, the Traditional method always led to the highest loss of altitude until re- covery.