The FAA's Helicopter Flying Handbook is the go-to reference source for helicopter pilots in the U.S. and worldwide. The FAA rarely updates the handbook, but just last October, it published a new edition for the first time since 2012. This 2019 edition includes a short section about a revolutionary technique called the Vuichard Recovery, developed to make recovering from the insidious and dangerous “vortex ring state” quicker and safer.
The newly FAA-blessed Vuichard Recovery is named after Captain Claude Vuichard, a former senior flight examiner for the Swiss Federal Office of Civil Aviation, who developed and teaches the technique. He is also known for developing numerous other safety techniques in helicopter operations and is the founder and president of the Vuichard Recovery Aviation Safety Foundation.
Vuichard is now best known in the helicopter community for developing, testing, and teaching his vortex ring state recovery. He continues to advocate for zero vortex ring state accidents and to spread his message regarding increased safety in the helicopter industry. HAI selected Vuichard to receive its 2018 Safety Award. Chapter 11 of the 2019 Helicopter Flying Handbook states: “Vortex ring state (formerly referenced as settling-with-power) describes an aerodynamic condition in which a helicopter may be in a vertical descent with 20 percent up to maximum power applied, and little or no climb performance. The previously used term settling-with-power came from the fact that the helicopter keeps settling even though full engine power is applied.”
Furthermore, “A vortex ring state may be entered during any maneuver that places the main rotor in a condition of descending in a column of disturbed air and low forward airspeed. Airspeeds that are below translational lift airspeeds are within this region of susceptibility to vortex ring state aerodynamics. This condition is sometimes seen during quick-stop type maneuvers or during recovery from autorotation.”
A combination of conditions is likely to lead a vortex ring state in any helicopter: 1) The rotor disk is using some of the available engine power (20 to 100 percent). 2) The horizontal velocity is slower than the effective translational lift. 3) The condition typically occurs when a helicopter is in a steep, “vertical descent with 20 percent of power up to maximum power applied, and little or no climb performance,” according to the FAA handbook.
When caught in a vortex ring state, a helicopter will continue to descend unless the pilot takes corrective action. Avoidance of a vortex ring state should be a pilot’s primary strategy. Recognizing that one is entering into a vortex ring state is the next step, and knowing how to get out of it is the crucial life-saving step.
The traditional recovery from vortex ring state is based on increasing forward airspeed, and/or partially lowering the collective to exit the vortex. The resulting nose-down attitude will, at least initially, cause the aircraft to descend even faster while the rotor blades grab for smooth air, so this maneuver can be dicey at low altitude. Nevertheless, this maneuver does work well when there’s enough height above the ground; and therefore, for decades, it has been the FAA’s standard procedure for exiting from a settling-with-power condition. Common errors during the traditional recovery from vortex ring state include too much lateral speed for entry into vortex ring state and excessive decrease of collective.
The Vuichard Recovery works by eliminating the helicopter’s descent rate as opposed to dropping the nose to increase airspeed. In most helicopters, using lateral (left or right) cyclic thrust combined with an increase in power and lateral anti-torque thrust will produce the quickest exit from the hazard. If the vortex ring state and the corresponding descent rate are allowed to progress to what is called the “windmill brake state” (the point where the airflow is completely up through the rotor), the only recovery may be an autorotation. Tandem rotor helicopters should maneuver laterally to achieve clean air in both rotors at the same time. Common errors during the Vuichard recovery from vortex ring state include excessive lateral cyclic and failure to maintain heading.