Freewing Flight Technologies is to fly a demonstrator of its "thrust- vectored pendulum" unmanned air vehicle within the next two months. A full-scale mock-up of the Spirit UAV was unveiled at last week's exhibition.
Freewing head Tom Sash says the approach is "a new method to achieve flight". The propeller boom is driven by two control surface wings attached below the rotor head, which "fly the boom". The boom moves through 90¡ to convert from vertical to horizontal flight. To fly vertically, the boom control surfaces direct the rotor airflow downwards, causing the boom to rise. Unlike traditional tiltrotor concepts, there is no mechanical system directly driving the boom.
Two short wings, optimised for cruise rather than take-off and landing, are pivot-mounted on the fuselage. The wing angle is determined by the propeller airflow, so in vertical flight they rotate to create minimal drag, but in horizontal flight become a lifting surface.
Sash says three Spirit variants are planned, the smallest with a 1.8m (6ft) rotor and 2.4m wingspan. The largest would have a 7.9m rotor disc and a 9.2m wingspan, and a planned 24h endurance. The technology demonstrator has a 2.6m rotor. Sash says seed funding was initially provided by NASA, but most development money has been raised by Freewing.
Source: Flight International
