RPM. While the pitching motions used in hover are not optimized for forward flight, in experimental evaluation they were found to provide efficient flight up to an advance ratio near one. Applications Wind turbines Wind turbines are a potential application of cyclorotors. They are named in this case variable-pitch vertical-axis wind turbines, with large benefits with respect to traditional VAWTs. This kind of turbine is stated to overcome most of the traditional limitations of traditional Darrieus VAWTs. Ship propulsion and control The most widespread application of cyclorotors is for ship propulsion and control. In ships the cyclorotor is mounted with the axis of rotation vertical so that thrust can quickly be vectored in any direction parallel to the plane of the water surface. In 1922, Kurt Kirsten fitted a pair of cyclorotors to a 32 ft boat in Washington, which eliminated the need for a rudder and provided extreme manoeuvrability. While the idea floundered in the United States after the Kirsten-Boeing Propeller Company lost a US Navy research grant, the Voith-Schneider propeller company successfully commercially employed the propeller. This Voith-Schneider propeller was fitted to more than 100 ships prior to the outbreak of the Second World War. Today, the same company sells the same propeller for highly manoeuvrable watercraft. It is applied on offshore drilling ships, tugboats, and ferries. Aircraft Cyclogyros A cyclogyro is a vertical takeoff and landing aircraft using a cyclorotor as a rotor wing for lift and often also for propulsion and control. Advances in cyclorotor aerodynamics made the first untethered model cyclogyro flight possible in 2011 at the Northwestern Polytechnic Institute in China. Since then, universities and companies have successfully flown small-scale cyclogyros in several configurations. The performance of traditional rotors is severely deteriorated at low Reynolds Numbers by low angle-of-attack blade stall. Current hover-capable MAVs can stay aloft for only minutes. Cyclorotor MAVs (very small scale cyclogyros) could utilize unsteady lift to extend endurance. The smallest cyclogyro flown to date weighs only 29 grams and was developed by the advanced vertical flight laboratory at Texas A&M university. Commercial cyclogyro UAVs are being developed by D-Daelus and Pitch Aeronautics. Airship propulsion and control A large exposed area makes airships susceptible to gusts and difficult to takeoff, land, or moor in windy conditions. Propelling airships with cyclorotors could enable flight in more severe atmospheric conditions by compensating for gusts with rapid thrust vectoring. Following this idea, the