Thierry Dubois is a freelance writer specializing in helicopters, business aviation and aerospace technology. He earned a degree in fluid dynamics from an engineering school in Toulouse, France in the mid-1990s. At an unexpected crossroads, he found his first job in journalism. In 1997, he started working for French aerospace weekly Air &amp; Cosmos in Paris. This lasted until 2000, when he moved south to Lyons. He then became a freelancer, working for various aerospace publications and has been part of the AIN team since late 2000. In addition to writing about business aviation, Thierry shares responsibility for the rotorcraft section. He also is a regular on-site writer for AIN’s daily editions at international airshows such as the Paris, Farnborough, Dubai and Singapore shows, as well as at EBACE in Geneva.
In 2007, he won the Honeywell award for “Best systems or technology submission” at the Aerospace journalist of the year awards. In 2013, he won an Aerospace Media Award for the "Best Safety, Training &amp; Simulation Submission."
In other activities, Thierry moderates international conferences on aviation technology topics. Thierry is married and has three children, who seem to begin enjoying the mountains–as their parents do.

Writer

Thierry Dubois

This year marks the 100th birthday of the helicopter, but it is actually difficult to be sure who deserves the title of “first to fly a manned rotorcraft.” Frenchmen Louis Breguet, Paul Cornu and Maurice Léger all achieved some sort of takeoff in 1907, but in reality this branch of aviation began more than a century before. In his book, Hélicoptères–La genèse, de Léonard de Vinci à Louis Breguet, journalist and historian Bernard Bombeau documents a story that started much earlier than many imagine.
When talking about helicopter forefathers, many think of Leonardo da Vinci. One of the Italian genius’s most famous sketches is that of a propeller that looks like a vertical helix and has a diameter measuring close to 65 feet. Da Vinci’s sketch appears closer to a screw than a rotor with blades, and you can see it on the homepage of Agusta Aerospace’s Web site, <a href="http://www.agusta.it" target="_blank">www.agusta.it</a>. Eurocopter is also marking the helicopter’s centenary at its Web site, <a href="http://www.eurocopter.com" target="_blank">www.eurocopter.com</a>. 
In 1754, in Russia, Mikhail Lomonosov tested a machine based on two four-blade contrarotating rotors. It was powered by a clockwork system. Lomonosov used it as a ground testbed that proved the spinning rotors elevated the machine. He even wrote about the lower and higher pressure above and below a blade, respectively. However, his “aerodromicheskaïa” never got off the ground.
Then in 1784, a French naturalist called Launoy and a physicist named Bienvenu presented an object to the Royal Science Academy in Paris–two contrarotating rotors made of two bird feathers each. One is attached to a bow; the other is attached to a stick positioned like an arrow. The bow’s string is elastic and is winched around the vertical stick. When released, this sort of scientific toy literally jumped to the ceiling, Academy members reported. Launoy and Bienvenu performed public demonstrations, but the invention remained largely ignored. At the time, in the science of flight, the focus was definitely on balloons. 
In 1784, Alban and Vallet built a hybrid aircraft composed of a hydrogen balloon and a sort of vertical, four-blade propeller. They reported vertical movements “without using gas or ballast”–the pilot’s muscles powered the propeller.
In 1843, an Englishman also had an idea for a compound helicopter. George Cayley’s “aerial carriage” had a sort of boat hull as a fuselage. Two pairs of contrarotating rotors provided lift. A horizontal-axis propeller, mounted at the rear, supplied thrust. Cayley built a model but could never find a suitable engine to test it.
The first mention of “helicopter” dates back to 1861. A Frenchman who patented his invention in London wrote about it in English. Gustave de Ponton d’Amécourt, a former sailor and a novelist, tested a small spring-powered model of a helicopter, with two contrarotating rotors. Later, in 1863, he tried the first steam-powered version but was able to record minimal elevation.
Imagining the Future Paradoxically, designs that now appear as a possible future for helicopters were conceived before the now-conventional configuration–main rotor plus tail rotor. In 1861, in New York, inventor Mortimer Nelson patented a project dubbed “aerial car.” Two pairs of four-blade contrarotating rotors were mounted on pylons that could tilt and thus provide lift when vertical or thrust when horizontal. This study, however, never made it off the paperboard.
Similarly, in 1876, Alphonse Pénaud in Paris patented another sort of tiltrotor. Two propellers could tilt. When their shafts were vertical, the lifting propellers were spinning inside a cutout in a wing. Pénaud found someone to manufacture the aircraft, but it was never built.
Enrico Forlanini in Alessandria, Italy, achieved some significant success. His 10-pound model, powered by a simplified steam engine, took off in 1877. It reached 43 feet and the flight lasted 20 seconds. 
In 1893, American Charles Parsons managed to fly a small steam-powered model. It reached a height of 13 feet, but Parsons was too busy with other activities in the U.S. and dropped aeronautics.
A number of European countries have been involved in the early ages of helicopters. For example, between 1895 and 1898, in Austria, Wilhelm Kress built a few small helicopters. One lifted off thanks to an electric powerplant on the ground. Two German researchers, the Achenbach brothers, were the first to come up with the idea of a tailrotor to counter the main rotor’s torque, rather than two contrarotating main rotors. But the 1874 idea stayed on paper.
The short takeoff and vertical landing version of the F-35 Lightning II had a precursor as early as 1895. In Russia, Konovalov’s project featured two main rotors in tandem configuration. The horizontal thrust from the two four-stroke engines’ exhaust pipes was to help the aircraft taking off. However, pioneer Nikolaï Joukovski discouraged the country’s minister of transport from funding the project. Konovalov dropped the idea of building his helicopter.
In France, Charles Renard helped helicopter theory advance when, in 1904, he obtained small liftoffs with his twin-rotor model powered by a three-horsepower Anzani internal combustion (IC) engine. It featured hinged rotor blades, which combined flexibility and stiffness.
Helicopters tried to compete with balloons before airplanes did. Nevertheless, in the early 20th century, the success of airplanes may have deterred promoters of vertical flight. For example, there was no full-scale helicopter at the Paris 1905 aviation competition. 
Wilbur Wright once said that he and his brother Orville had a first glimpse at aviation thanks to small wooden helicopters, built from Cayley’s and Pénaud’s models. “But we quickly understood there was no future in such designs,” he insisted.
In the late 19th and early 20th centuries, IC engines benefited from a sharp increase in power-to-weight ratio. Swiss brothers Henri and Armand Dufaux in 1905 used the 10-pound, three-horsepower engine they had designed for a moped. They succeeded in powering a small helicopter model. 
That same year, Brazilian pioneer Alberto Santos-Dumont realized his helicopter was underpowered. After some rig tests in Paris, he stopped building it. If nothing else, the tests proved that the 24-hp Levavasseur Antoinette engine was too weak.
Léger, one of three 1907 newsmakers, had his first success in 1905. That year, he lifted a 220-pound payload, including a passenger, in Monaco. He based the aircraft on two contrarotating rotors, powered by an electric motor on the ground. 
Cornu was born in a family of inventors. In 1904, with his father, he had built a small car powered by two single-cylinder IC engines that reached 47 mph.
Cornu realized he had been too optimistic about the theory of vertical flight when building a small prototype. This made it hard for him to set some key parameters, including blade pitch and rotation speed. But he succeeded and performed controlled (albeit unmanned) takeoffs in 1906. The aircraft had two seven-foot rotors and one two-horsepower IC engine. It weighed 30.5 pounds.
The French pioneer’s full-scale helicopter was trickier to manufacture. The inventor had a hard time solving problems with skidding transmission belts. Finally, although witness reports somewhat conflict, in November 1907 Cornu took off in his aircraft, reportedly reaching a height of four feet. 
The third 1907 helicopter newsmaker was Louis Breguet. A methodical character, Breguet started testing rotary wings on a testbed. In September 1907, his four-rotor, 50-horsepower “gyroplane” took off. Engineer Maurice Volumard was at the controls and the aircraft reached a reported two feet.&nbsp;&nbsp;

Happy Birthday Helo

This year marks the 100th birthday of the helicopter, but it is actually difficult to be sure who deserves the title of “first to fly a manned rotorcraft.”

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