The Santos-Dumont Demoiselle ("Damselfly") was an early aircraft built in France by Brazilian aviation pioneer Alberto Santos-Dumont. It was a light-weight monoplane with a wire-braced wing mounted atop an open-framework fuselage built around a reinforced bamboo boom. The pilot's seat was below the wing, and between the main wheels of the undercarriage. The rear end of the boom carried a tailwheel and a conventional empennage. As originally designed (as the Santos-Dumont No. 19) Santos-Dumont used a liquid-cooled Dutheil & Chalmers flat-twin engine rated at 15 kW (20 hp) mounted on the leading edge of the wing. Later, the inventor repositioned the engine to a lower location, placing it in front of the pilot. The Demoiselle was controlled in flight by a tail unit, pivoting on a form of universal joint that functioned both as elevator and rudder, which the pilot operated with a steering wheel.