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Birth of an industry

Heinrich Focke at Focke-Wulf had purchased a license from Cierva Autogiro Company, which according to Frank Kingston Smith Sr., included "the fully controllable cyclic/collective pitch hub system". In return, Cierva Autogiro received a cross-license to build the Focke-Achgelis helicopters. Focke designed the world's first practical helicopter, the transverse twin-rotor Focke-Wulf Fw 61, which first flew in June 1936. It was demonstrated by Hanna Reitsch in February 1938 inside the Deutschlandhalle in Berlin. The Fw 61 set a number of FAI records from 1937 to 1939, including: maximum altitude of 3,427 metres (11,243 ft), maximum distance of 230 kilometres (140 mi), and maximum speed of 124 kilometres per hour (77 mph). Autogiro development was now being bypassed by a focus on helicopters.

During World War II, Nazi Germany used helicopters in small numbers for observation, transport, and medical evacuation. The Flettner Fl 282 Kolibri synchropter —using the same basic configuration as Anton Flettner 's own pioneering Fl 265 —was used in the Baltic, Mediterranean, and Aegean Seas. The Focke-Achgelis Fa 223 Drache, like the Fw 61, used two transverse rotors, and was the largest rotorcraft of the war. Extensive bombing by the Allied forces prevented Germany from producing helicopters in large quantities during the war.

In the United States, Russian-born engineer Igor Sikorsky and Wynn Laurence LePage competed to produce the U.S. military's first helicopter. LePage received the patent rights to develop helicopters patterned after the Fw 61, and built the XR-1 in 1941. Meanwhile, Sikorsky settled on a simpler, single-rotor design, the VS-300 of 1939, which turned out to be the first practical single lifting-rotor helicopter design. After experimenting with configurations to counteract the torque produced by the single main rotor, Sikorsky settled on a single, smaller rotor mounted on the tail boom.

Developed from the VS-300, Sikorsky's R-4 of 1942 was the first large-scale mass-produced helicopter, with a production order for 100 aircraft. The R-4 was the only Allied helicopter to serve in World War II, used primarily for search and rescue (by the USAAF 1st Air Commando Group) in the Burma campaign; in Alaska; and in other areas with harsh terrain. Total production reached 131 helicopters before the R-4 was replaced by other Sikorsky helicopters such as the R-5 and the R-6. In all, Sikorsky produced over 400 helicopters before the end of World War II.

While LePage and Sikorsky built their helicopters for the military, Bell Aircraft hired Arthur Young to help build a helicopter using Young's two-blade teetering rotor design, which used a weighted stabilizer bar placed at a 90° angle to the rotor blades. The subsequent Model 30 helicopter of 1943 showed the design's simplicity and ease of use. The Model 30 was developed into the Bell 47 of 1945, which became the first helicopter certified for civilian use in the United States (March 1946). Produced in several countries, the Bell 47 was the most popular helicopter model for nearly 30 years.