A multirotor seen from the side, in three steps. Step 1, normal descent: the aircraft descends while moving forward, so its rotor downwash goes down and is left behind, and the rotors keep meeting clean air. Step 2, vortex ring: the aircraft descends steeply with little horizontal movement and sinks into its own downwash. The air around the rotor tips recirculates in rings (down through the rotors, out, up and back in), a red column of disturbed air forms, and the aircraft wobbles. Step 3, recovery: the vertical descent is reduced and the aircraft moves laterally out of the disturbed column, which is left behind and fades, and clean downwash returns. The airflow is schematic. Use the manufacturer's recovery guidance and operator procedures for the aircraft in use. The still frame shows step 2.
