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vortex ring state
- Sinônimos - Inglês
- settling with power
- Definição1
- A transient condition of downward flight (descending through air after just previously being accelerated downward by the rotor) during which an appreciable portion of the main rotor system is being forced to operate at angles of attack above maximum. Blade stall starts near the hub and progresses outward as the rate of descent increases.
- Fonte1
- FEDERAL AVIATION ADMINISTRATION. Rotorcraft flying handbook (FAA-H-8083-21). Washington, DC: FAA, 2000. Disponível em: http://www.faa.gov/library/manuals/aircraft/media/faa-h-8083-21.pdf. Acesso em: 10 fev. 2012.
- Fonte2
- FEDERAL AVIATION ADMINISTRATION. Helicopter flying handbook (FAA-H8083-21A). Washington, DC: FAA, 2012.
- Nota Adicional1
- The vortex ring state causes tail rotor thrust variations, which result in yaw deviations. The net effect of the unsteady flow is an oscillation of tail rotor thrust. Rapid and continuous pedal movements are necessary to compensate for the rapid changes in tail rotor thrust when hovering in a left crosswind.
- Nota Adicional2
- If the descent rate continues to increase and the rotor blades come ever closer to the preceding tip vortex spirals, the tip vortices begin to enlarge. The helicopter reaches a point at which most of the power developed by the engine is wasted accelerating the air in a doughnut pattern. In effect, the helicopter is flying in its own downwash of disturbed air. The main rotor is stalled only at the inner sections near the hub. The characteristic symptoms of this condition are an increased low frequency airframe vibration level, pitch and roll motions, and an increase of the rate of descent with an increased application of collective pitch. Increasing collective pitch strengthens the blade tip vortex action and decreases the angle of attack, and lift generated, at the outer sections of the blade. The stall area increases at the inner sections of the blade. The inner and outer sections of the blades produce less thrust thus increasing the rate of descent. Subsequent lowering of the collective causes the inner sections of the blade to go deeper into a stall and the blade tip section to further reduce its lift coefficient. The helicopter has entered the vortex ring state.
- Contexto
- A vortex ring state may be entered during any maneu- ver that places the main rotor in a condition of high upflow and low forward airspeed. This condition is sometimes seen during quick-stop type maneuvers or during recoveries from autorotations.
- Subárea
- Piloting
- Related Term
- settling with power
- tail rotor vortex ring state
- Français
- état de vortex