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First Vertical Flight:The first manned helicopter to rise vertically completely unrestrained was constructed by Paul Cornu, a French mechanic, in 1907. Cornu's helicopter had two propellers that were rotated at 90 rpm by a 24-hp (18 kW) engine.
Cornu's helicopter, 1907 [from McCormick, 1995]As another first, Cornu was most probably the first helicopter experimenter who was concerned with control. To this end, Cornu had installed sets of vanes just below each rotor to deflect the downwash for maneuvering and forward thrust. While Cornu's helicopter was historically significant, its performance and control was rather marginal, and it was never a practical machine. New Developments:The next influential development in the field of helicopters was brought about by a man who never actually built a helicopter himself. In 1923, Juan de la Cierva successfully flew his C.4 autogiro, an aircraft that has two propellers, a powered one to provide thrust, and an unpowered rotor to provide lift. Cierva's autogiro was noteworthy because it was the first to use an "articulated" rotor that allowed its blades to flap up and down in response to aerodynamic forces on the blades during forward flight. As will be discussed in the next section, the articulated rotor helped to eliminate large blade stresses at the rotor hub. Cierva died in an airliner accident in 1936 at the age of 42, and he never had the opportunity to incorporate an articulated rotor into a helicopter himself. The first recognized helicopter record was set in October 1930 by Italian Corradino D'Ascanio when he flew his helicopter over a distance of one half mile at an altitude of 59 ft (18 m) for 8 minutes and 45 seconds. D'Ascanio's helicopter had two contrarotating coaxial rotors (two rotors on the same shaft) that were controlled by flaps on booms trailing each blade near its tip.
D'Ascanio's helicopter, 1930 [from McCormick, 1995]
First True Helicopters:Just before and during World War II, Germany made several large, significant steps in helicopter development. The FA-61 helicopter, designed by Heinrich Focke, first flew in June 1936, and was later used in publicity stunts by the Nazis. The FL-282 helicopter, designed by Anton Flettner, became operational with the German Navy, and over 1000 of them were produced. This helicopter utilized twin intermeshing rotors, had a forward speed of 90 mph (145 km/h), and could operate at an altitude of 13,000 ft (3,965 m) with a payload of 800 lb (360 kg). The first American helicopter was the VS-300, designed by Igor Sikorsky of the Vought-Sikorsky Company. The VS-300 was the first helicopter to use a tail rotor to counteract the torque produced by the main rotor, and it was this innovation that solved the last major hurdle in making helicopters practical flying vehicles. This design is now the most common in today's helicopters.
Sikorsky's VS-300, 1939 [from McCormick, 1995]The VS-300 made its first tethered flight in September 1939 and its first free flight on 13 May 1940. |
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