the former 20-hp engine by a 24-hp Antoniette and carried out some wing reinforcements. This version received the designation number 20.
Due to structural problems and continuing lack of power, Santos-Dumont introduced additional modifications into the Demoiselle’s design: a triangular and shortened fuselage made of bamboo; the engine was moved back to its original position, in front of the wing; and increased wingspan. Thus, number 21 was born. The design of number 22 was basically similar to number 21. Santos-Dumont tested opposed-cylinder (he patented a solution for cooling this kind of engine) and cooled-water engines, with power settings ranging from 20 to 40 hp, in both variants. An interesting feature of the water-cooled variant was the liquid-coolant pipeline that followed the wing lower side lofting to improve the aircraft aerodynamics.
Dumont’s monoplane could be constructed in only 15 days. Possessing outstanding performance, easily covering 200 m of ground during the initial flights and flying at speeds of more than 100 km/h, the Demoiselle was the last aircraft built by Santos-Dumont, He used to perform flights with the airplane in Paris and some small trips to nearby places. Flights were continued at various times through 1909, including the first cross-country one with steps of about 8 km, from Saint Cyr to Bue on September 13, returning the following day, and another on the 17th, of 18 km in 16 minutes. The Demoiselle that was fitted with two-cylinder engine became rather popular. Santos-Dumont was so enthusiastic about Aviation that he released the drawings of Demoiselle for free, believing that aviation would be the mainstream of a new prosperous era for mankind (Fig. 12). Clément Bayard, an automotive and bicycle maker, constructed several units of Demoiselles, which was sold for 50,000 Francs. The design of Demoiselle clearly influenced that of the Blériot 6th airplane, which was used by his friend Louis Blériot for the British Channel crossing, in 1909.
The French World War I ace Roland Garros flew it at the Belmont Park, New York, in 1910. The June 1910 edition of the Popular Mechanics magazine published drawings of the Demoiselle and affirmed that Santos-Dumont’s plane was better than any other that had been built up to that date, for those who wish to reach results with the least possible expenses and with minimum of experimenting. American companies sold drawings and parts of Demoiselle for several years thereafter.
The World War I greatly stepped up Aviation growth. In 1911, Blériot’s company released the first transport aircraft with enclosed cabin, which was christened Aérobus. In November 1909, Igo Etrich made the first flight in Austria in an Austrian designed and built airplane, at Wiener-Neustadt. It was called the Taube (pigeon) and was a monoplane with bird-like wings. Subsequently, it was produced in refined form as single, two or three-seaters. The maiden flight of the so-called Etrich’s Luftlimousine took place on May 7, in 1912, only six days after the Avro Type F (Fig. 13), the latter has been considered as the first aircraft with a fully enclosed cabin to fly (Schmitt, 1990).
The top speed of the Etrich aircraft with three passengers on board was 106 km/h. Shortly after the World War I, the first airlines were founded and started operating with retrofitted bomber planes. German manufacturer, Junkers, designed and produced the world’s first all-metal planes, as some were used in combat in the later stages of the World War I. The Junkers F.13 was the first airplane intended for passenger transportation, and its first flight was in 1919. It was the world’s first all-metal transport airplane.
