(i.e. between the hub and the innermost edges of the airfoils), the induced flow (air pulled or "induced" downwards through the rotor system) of the inner blade sections is overcome. This causes the innermost portions of the blades to begin to stall. As the inner blade sections stall, a second set of vortices, similar to the rotor-tip vortices, begins to form in and around the center of the rotor system. This, combined with the outer set of vortices, results in severe loss of lift. The failure of a helicopter pilot to recognize and react to the condition can lead to high descent rates and catastrophic ground impact. Occurrence A helicopter normally encounters this condition when attempting to hover out-of-ground-effect (OGE) without maintaining precise altitude control, and while making downwind or steep, powered approaches when the airspeed is below Effective Translational Lift (ETL). Detection and correction The signs of VRS are a vibration in the main rotor system followed by an increasing sink rate and possibly a decrease of cyclic authority. In single rotor helicopters, the vortex ring state is traditionally corrected by slightly lowering the collective to regain cyclic authority and using the cyclic control to apply lateral motion, often pitching the nose down to establish forward flight. In tandem-rotor helicopters, recovery is accomplished through lateral cyclic or pedal input or both. The aircraft will fly out of the vortex ring into "clean air", and will be able to regain lift. Another correction now widely known as the Vuichard Recovery Technique after gaining recent popularity, was taught by Claude Vuichard, a Federal Office for Civil Aviation (FOCA) inspector in Switzerland. This technique uses a combination of all three controls together to reduce altitude loss and recover more quickly: apply cyclic in the direction of tail rotor thrust, increase the collective to climb power, and coordinate with the power pedal to maintain heading (cross controls). Recovery is complete when the rotor disc reaches the upwind part of the vortex. Powering out of vortex ring state It is possible to power out of vortex ring state, but this requires having about twice the power it takes to hover. Only one full-scale helicopter, the Sikorsky S-64 Skycrane, is documented as being able to do this, when unladen. Pilot or operator reaction Helicopter pilots are most commonly taught to avoid VRS by monitoring their rates of descent at lower airspeeds. When encountering VRS, pilots