It had a pair of hexagonal rudders below the wing on either side of the pilot, a forward mounted hexagonal elevator in front of the pilot and a cruciform tail which, like the boxkite-style canard surfaces on the earlier 14-bis biplane of 1906, pivoted on a universal joint to function both as elevator and rudder mounted at the end of a substantial single boom.

[2] Later, Santos-Dumont made a number of modifications: he repositioned the engine, placing it below the wing in front of the pilot, fitted a different propeller and removed the forward elevator and rudders.

It used wing warping, which had been patented by the Wright Brothers in 1906, for lateral control, operated from a transverse-pivoting joystick that would fit into a long, vertical pocket added to the jacket's back that the pilot would wear to fly the aircraft, "leaning into the turn" as either a bicycle rider would do for higher-velocity turns; or as Glenn Curtiss did with the transverse "rocking-cradle armrest" apparatus on the AEA June Bug in 1908.

A similar system was used by Santos-Dumont in November 1906 to likewise operate the interplane ailerons on the final version of his Quatorze-bis (14 bis) pioneering canard biplane.

The initial #20 Demoiselle's wing-warping arrangement also possessed control cabling that only pulled down alternately on the outer section of the rear wing spar with no "upwards" warp capability.

[6] The French pioneer aviator Roland Garros learned to fly in a Demoiselle at a flight school established by Clement Bayard, and later flew one at Belmont Park, New York in 1910.

The June 1910 edition of Popular Mechanics published drawings of the Demoiselle and wrote "This machine is better than any other which has ever been built, for those who wish to reach results with the least possible expense and with a minimum of experimenting.