ANTON FLETTNER Inventor of the intermeshing-rotors design.
Library of Congress, Prints & Photographs Division, LC-DIG-ggbain- 37770
Born in Germany in 1885, Anton Flettner was a prolific inventor who contributed to armored- vehicle, automotive, aviation, and marine technology. While working for the German military during World War I, his efforts on remotely controlled air, land, and marine vehicles led to the servo tab, or trim tab, which is
used on many airplanes to this day. In the 1920s, he developed the Flettner
rotor, a vertical cylinder that harnesses wind to create horizontal lift to propel and steer a ship. (Tese types of ships are still sailing today.) Tis spurred development of the Flettner ventilator. Today, that ventilator aerates hundreds of thousands of boats, buildings, buses, delivery trucks, fire engines, and trains. Royalties from trim tabs and ventilators
built a fortune that funded Flettner’s pursuit of his vision: a vertical lift aircraft with an extended service life. A drawback of the helicopter’s design was
gearboxes that required overhauling after a few hundred hours. Flettner, however, believed that service intervals could be increased to thousands of hours by reducing the gearbox load. His solution: intermeshing rotors, offset from the vertical mast and driven by a single gearbox to lessen gear loading, without tail-rotor torque control. Te Fl 184, an autogyro with cyclic pitch control
that Flettner designed, first flew in 1935, and the intermeshing Fl 265 took to the air in 1939, months before Sikorsky’s VS-300 took flight.
Mountain Bladerunner Kaman K-Max | Mark Bennett Photo Flettner came to the United States in 1947 as part of
Operation Paperclip, a postwar program that brought German scientists, engineers, and technicians to the United States to consult for the US military. In 1949, he set up Flettner Aircraft Corp. in Queens, New York, where he conducted research for the US military. He died on Dec. 29, 1961.
SPECIAL COMMEMORATIVE ISSUE ROTOR 139 Flettner kept improving on his designs and two
years later the Fl 265 transitioned from autorotation back to helicopter flight—a significant achievement at the time. In 1955, Flettner told Aviation Week that that functionality “established the helicopter as a practical aircraft.” Flettner’s Fl 282 Kolibri (Hummingbird), an
improved version of the Fl 265, had its first flight in 1941 and was flown by the German Navy and Air Force, marking the first military use of a helicopter. Flettner’s intermeshing-rotors design is still in use
today, as it is the foundation for several of Kaman’s products, including the HH-43 Huskie and the K-Max.
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