One will not believe that helicopters now days could be so manoeuvrable. The one helicopter actually flew upside down in a circle and the last two were doing a face-off which was almost like a ballet.
At the end of the nineteenth century, the internal combustion engine became available, making the development of full-sized vertical-flight craft with adequate power a possibility. However, other problems remained, particularly those relating to torque, dissymmetry of lift, and control. Inventors during the next two decades built many small prototype helicopters that attempted to solve these problems, but progress came only in small steps.
Gaetano A. Crocco of Italy patented an early cyclic pitch design in 1906. Crocco recognized that a way to change the pitch cyclically on the blades was needed if a helicopter was to work properly in forward flight.
During 1906, the brothers Louis and Jacques Bréguet began their helicopter experiments and meticulously tested airfoil shapes under the guidance of Professor Charles Richet. In 1907, they built the Bréguet-Richet Gyroplane No. 1, one of the first mechanical devices to actually hover. The gyroplane flew for one minute on August 24, 1907 (some sources say September 29, 1907) in what is generally accepted as the first vertical flight. A 45-horsepower (33.5-kilowatt) engine provided just enough power to achieve vertical flight. However, there was no means of control or stability, and it needed four men to steady it while it hovered about 2 feet (0.6 meters) off the ground. Without a control system, it was not a practical helicopter.
In June 1909, Igor Sikorsky built his first helicopter, the S-1, in Kiev, Russia. The wooden craft weighed 450 pounds (204 kilograms) and had dual coaxial rotors. But the two blades were inefficient, and the most powerful engine that was available, a 25-horsepower (20 kilowatt) Anzani engine, could not lift its own weight. The next year, he built the S-2, which weighed only 400 pounds (181 kilograms) and had a three-blade rotor system. This model could rise, but the engine was too weak to carry a passenger. The machine also shook and vibrated violently because it needed a stiffer frame. Sikorsky turned to airplane development, returning to helicopters only in the 1930s after he emigrated to the United States.
Professor Zhukovskii and his students at Moscow University may also have constructed a primitive coaxial helicopter in 1910. Zhukovskii was well known for his theoretical contributions to aerodynamics and published several papers on the subject of rotating wings and helicopters.
In 1912, the Russian Boris Yuriev built a 445-pound (202-kilogram) helicopter that had a modern-looking single rotor and smaller tail rotor and large diameter, high aspect ratio blades. The tail rotor was needed to counteract the torque generated by the main rotor but it added weight and like Sikorsky's helicopters, had an undersized engine. The machine never flew properly. But Yuriev was one of the first to use a tail rotor and also one of several pioneers to propose the concept of cyclic pitch for rotor control.
Two Austrians, Stephan Petroczy and Professor Theodore von Karman, built and flew a coaxial rotor helicopter during the closing years of World War I. Intended for observation, this machine included a pilot/observer position above the wooden counter-rotating rotors, inflated bags for landing gear, and a quick-opening parachute. Three 120-horsepower (89-kilowatt) rotary engines provided power. The machine achieved numerous short vertical flights restrained by cables and reached a height of more than 150 feet (46 meters).
In the 1920s, the Marquis Raul Pateras Pescara, an Argentinean working in Europe, achieved one of the first successful applications of cyclic pitch. He was also the first to demonstrate that a helicopter with engine failure could still reach the ground safely by means of autorotation—the phenomenon that caused blades to turn even without power being applied to them that resulted from the flow of air as the craft moved through it. His coaxial helicopter had biplane-type rotors with a total of 20 lifting surfaces. In 1924, Pescara set a new world record by flying his craft almost one-half mile (0.8 kilometer) in 4 minutes and 11 seconds—a speed of about eight miles per hour (13 kilometers per hour)—at a height of six feet (1.8 meters).
Another French pioneer, Etienne Oehmichen, began his experiments in 1920 by suspending a balloon above a twin-rotor helicopter to provide additional lift. A later design had four lifting airscrews and five auxiliary propellers. On April 14, 1924, he flew this type of craft, powered by a 180-horsepower (134-kilowatt) Rhone engine, 1,181 feet (360 meters), establishing the first helicopter distance record officially recognized by the Federation Aeronautique Internationale. On May 4, he was the first to fly a helicopter at least one kilometer (0.6 mile) in a closed circuit in a 5,550-foot (1.692-kilometer) flight that lasted 14 minutes and rose to 50 feet (15 meters).