The Voith Cycloidal Rudder is based on the Voith-Schneider Propulsor. It has a rotor casing that can rotate about a vertical axis, with two axially parallel rudder blades or hydrofoils projecting from it. Fundamentally, there are two different operating modes: passive and active. In the passive mode, the VCR acts as a conventional rudder and is used for this purpose when the ship is cruising. The active mode is used at low speed, e.g. in port. The VCR is then a high-precision source of propulsion when manoeuvring.