The vortex ring state, also known as settling with power, is a dangerous condition that may arise in helicopter flight. Essentially, the helicopter descends into its own downwash. When the condition arises, increasing the rotor power merely feeds the vortex motion without generating additional lift.
Vortex Ring State can occur as a result of attempting to descend at an excessively low airspeed in a downwind condition, or by attempting to hover OGE at a weight and density altitude greater than the helicopter’s performance allows.
Vortex Ring State always requires three conditions to occur:
1. Rate of descent greater than 300 fpm
2. Airspeed less than ETL
3. Engine power applied
By taking away any one of the three conditions, settling with power should not occur.
The noticeable effects are vibration, reduced control effectiveness, and a high rate of descent. Other indications to confirm the vortex ring state include a further loss of altitude with up collective or fallen trim strings.
Traditionally pilots have been taught to lower the nose (forward cyclic), reduce power and, essentially, “fly out” of the condition.
Vuichard Technique-Rather than forward cyclic and reduced collective, actually increase the collective to climb power, add the appropriate left pedal to keep the nose straight and apply right cyclic. The combination of tail rotor thrust and right bank moves the aircraft to the right and almost immediately out of the vortex ring. Recoveries from a fully developed vortex ring state can be completed with only 20 to 30 ft of altitude loss as opposed to hundreds of feet with traditional techniques.