This is a teaching companion to the B50EF handout. The animation explains flow topology; it is not CFD, an onset predictor or flight guidance. No quiz answers or personal information are sent to a server.

1. W. Johnson, Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics, NASA/TP-2005-213477, 2005. Momentum-theory limits and mean-inflow modelling.
2. J. G. Leishman, Helicopters, Introduction to Aerospace Flight Vehicles, ERAU. Actuator-disk and blade-element theory.
3. R. B. Green, E. A. Gillies and R. E. Brown, The flow field around a rotor in axial descent, J. Fluid Mech., 534, 237–261, 2005. Experimental wake switching and recirculation.
4. A. Savino et al., Experimental investigation of vortex ring state in an eVTOL propeller, Aerospace Science and Technology, 165, 110475, 2025. Minimum thrust near DR = 0.9; thrust loss slightly over 20% relative to hover in the tested conditions.
5. G. Bucherelli et al., Experimental investigation of the vortex ring state for side-by-side propellers in descent flight, Physics of Fluids, 38, 035136, 2026. Table II supplies the plotted core-radius data. Paired co-rotating cases use D = 0.9; the isolated reference uses D = 1.1.
6. E. Sotiropoulos-Georgiopoulos et al., Evaluation of VRS onset and entry fidelity in helicopter flight simulators, CEAS Aeronautical Journal, 2026. Collective trim, vibration and entry cues require separate validation.
7. L. Binet and P.-M. Basset, EASA D-4.3 Final Report, 2025. Recovery depends on aircraft, flight state and workload.

Scope of the interactive models. Wake sliders blend explanatory flow patterns, with no experimentally calibrated transition boundary. The blade diagram uses α = θ − φ and does not calculate full-rotor thrust. The calculator assumes upright flight, T ≈ mg in hover, g = 9.81 m/s², and negligible drag. The thrust-deficit scenario is an illustrative assumption, not a measured VRS trajectory. Research reviewed for the handout through November 2026.