EASA has undertaken a major two-year research project designed to provide a better understanding of vortex ring state (VRS) in various types of helicopters, determine related analytical and simulation prediction methods, and indicate alternative recovery maneuvers including the Vuichard recovery. The project is being funded by the European Union’s “Horizon Europe” research program.
According to the FAA Helicopter Handbook, VRS or “settling with power” occurs when the rotor disk is using some of the available engine power, horizontal velocity is slower than the effective translational lift, or the helicopter is in a steep descent and applied engine power results in little or no climb performance. Traditional recovery teaches increasing forward airspeed while lowering the collective to escape VRS, but this has limited effectiveness at lower altitudes. The Vuichard method stresses the application of lateral cyclic and anti-torque thrust with increased power.
EASA notes that current helicopter certification standards do not require addressing VRS or require discussion in the rotorcraft flight manual. While VRS is incorporated into helicopter pilot training, the most prevalent recovery method taught is the traditional one.
The research will include experimental flight testing in at least two different helicopter types having different kinds of main rotor systems. The aircraft will be instrumented with sensors capable of measuring and recording real-time flight and system parameters appropriate for the scope and objectives of the flight test program.