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Intermeshing rotors on a helicopter are a set of two rotors turning in opposite directions, with each rotor mast mounted 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 a tail rotor, which saves power. However, neither rotor lifts directly vertically, which reduces efficiency per each rotor.
This configuration is sometimes referred to as a synchropter.
Most intermeshing designs have two blades per mast, although exceptions such as the Kellett XR-10 with three blades per mast do exist.
The arrangement was developed in Germany by Anton Flettner for a small anti-submarine warfare helicopter, the Flettner Fl 265 as the pioneering example, and later the Flettner Fl 282 Kolibri. During the Cold War the American Kaman Aircraft company produced the HH-43 Huskie, for USAF firefighting purposes. One example of the Kaman K-225 experimental synchropter was fitted with a small turboshaft engine in late 1951, becoming the world's first gas turbine-powered helicopter. 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, and has been modified for trials by the USMC as an optionally-unmanned cargo transporter. Unmanned aerial vehicles with intermeshing rotors have also been flown.
List of intermeshing rotor helicopters
- Flettner Fl 265 (1939)
- Flettner Fl 282 (1941)
- Kellett XR-8 (1944)
- Kaman K-225 (1947)
- Kellett XR-10 (1947)
- Praga E-1 (1947)
- SNCAC NC.2001 Abeille (1949)
- Kaman HH-43 Huskie (1953)
- Kaman K-700 (1969) (abandoned)
- Clybouw CW-105F (1973)
- DeGraw RDX1091 Hummingbird (1984)
- Kaman K-MAX (1991)
- Day & McNeil; Lance Day; Ian McNeil (1998). Biographical Dictionary of the History of Technology. Taylor & Francis. p. 261. ISBN 0-415-19399-0. CS1 maint: discouraged parameter (link)
- Mortimer, Gary (13 October 2017). "Swissdrones testing heavy lift helicopter". sUASNews.com. Retrieved 16 October 2017. CS1 maint: discouraged parameter (link)
- Media related to Intermeshing-rotor helicopters at Wikimedia Commons