fenestron

thumb|A view of a Fenestron tail rotor on a Eurocopter EC120B

A Fenestron (sometimes alternatively referred to as a fantail or a "fan-in-fin" arrangement) is an enclosed helicopter tail rotor that operates like a ducted fan. The term Fenestron is a trademark of multinational helicopter manufacturing consortium Airbus Helicopters (formerly known as Eurocopter). The word itself comes from the Occitan term for a small window, and is ultimately derived from the Latin word fenestra for window.