Intermeshing rotors
Encyclopedia
Intermeshing rotors on a helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

 are a set of two rotors turning in opposite directions, with each rotor mast mounted on the helicopter with a slight angle to the other, in a transversely symmetrical manner, so that the blades intermesh without colliding. The arrangement allows the helicopter to function without the need for a tail rotor
Tail rotor
The tail rotor, or anti-torque rotor, is a smaller rotor mounted so that it rotates vertically or near-vertically at the end of the tail of a traditional single-rotor helicopter. The tail rotor's position and distance from the center of gravity allow it to develop thrust in the same direction as...

. This configuration is sometimes referred to as a synchropter.

The arrangement was developed in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 by Anton Flettner
Anton Flettner
Anton Flettner was a German aviation engineer and inventor. He made important contributions to airplane and helicopter design...

 for a small anti-submarine warfare
Anti-submarine warfare
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

 helicopter, the Flettner Fl 265
Flettner Fl 265
-References: Nowarra, Heinz J.: Die Deutsche Luftrüstung 1933-1945, Bernard & Graeffe Verlag, Koblenz 1993, ISBN 3-7637-5464-4-External links:*...

 and later the Flettner Fl 282 Kolibri
Flettner Fl 282
|- References :NotesBibliography* Coates, Steve and Jean-Christophe Carbonel. Helicopters of the Third Reich. Crowborough, UK: Classic Publications Ltd., 2002. ISBN 1-903223-24-5....

. During the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

 the American Kaman Aircraft
Kaman Aircraft
Kaman Aircraft is a U.S. aerospace company, with headquarters in Bloomfield, Connecticut. It was founded in 1945 by Charles Kaman. During the first ten years the company operated exclusively as a designer and manufacturer of several helicopters that set world records and achieved many aviation...

 company produced the HH-43 Huskie, for USAF firefighting purposes. One example of the Kaman K-225
Kaman K-225
-External links:* 1949 Popular Science article on Kaman K-190 and the blade intermesh technology developed by Kaman — ie rare photos* * *...

 experimental synchropter was fitted with a small turboshaft engine in late 1951, becoming the world's first gas turbine powered helicopter of any type. Intermeshing rotored helicopters have high stability and powerful lifting capability. The latest Kaman K-MAX model is a dedicated sky crane design used for construction work.
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