Aviation glossary
Vortex Ring State
A dangerous helicopter aerodynamic condition (VRS). The rotor recirculates its own downwash and loses thrust — adding collective makes it worse.
Vortex Ring State occurs when a helicopter descends fast enough vertically (typically > 300 ft/min) under power with low forward airspeed (< about 20 kt). The rotor downwash curls around the blade tips and the rotor starts operating in its own downwash — thrust drops, the vertical descent rate accelerates and the pilot's instinctive collective input only makes things worse. Recovery: tilt the disc forward to gain undisturbed airflow ("fly out of the ring"). Prevention: avoid rapid powered descents, watch airspeed on final and when entering a hover.
Related terms
- AutorotationA flight condition in which airflow through the rotor keeps it spinning without engine power. Lets a helicopter land safely after a power failure.
- Cyclic controlThe primary helicopter control operated by the right hand. Tilts the rotor disc and sets the direction of flight — forward, back or sideways.
- Mast bumpingA hazardous condition on helicopters with a two-bladed semi-rigid rotor: the rotor hub strikes the mast — usually at low or negative G. Almost always catastrophic.