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A coaxial-rotor aircraft is an aircraft whose rotors are mounted one above the other on concentric shafts, with the same axis of rotation, but turning in opposite directions (contra-rotating). This rotor configuration is a feature of helicopters produced by the Russian Kamov helicopter design bureau .
Tandem-rotor helicopters such as the CH-47 Chinook also use a counter-rotating arrangement. The efficiency of a contra-rotating propeller is somewhat offset by its mechanical complexity. Nonetheless, coaxial contra-rotating propellers and rotors are moderately common in military aircraft and naval applications, such as torpedoes, where the ...
Both designs used the principle of counter-rotating side-by-side intermeshing rotors, as the means to solve the problem of torque compensation, normally countered in single–rotor helicopters by a tail rotor, fenestron, NOTAR, or vented blower exhaust.
The tail 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 a direction opposite that of the main rotor's rotation, thereby countering the torque effect ...
Like other Kamov helicopters, it features Kamov's characteristic coaxial contra-rotating rotor system, which removes the need for the entire tail rotor assembly and improves the aircraft's aerobatic qualities—it can perform loops, rolls and "the funnel" (circle-strafing), where the aircraft maintains a line-of-sight to the target while flying ...
His test rig, with two wheels and handlebars, resembled a wheelbarrow with an engine mounted in it, with a tall vertical shaft driving two counter-rotating propellers. [9] In 1922, Henry Berliner developed a helicopter based on a surplus Nieuport 23 fuselage with a 220 hp radial engine driving two wing mounted counter-rotating rotors. The ...
[27] [5] Compared to conventional helicopters, the counter-rotating coaxial main rotors and pusher propeller offer a 185-knot (213 mph; 343 km/h) speed increase, a 60% combat radius extension, and 50% better performance in high-hot hover operations.
Single-rotor helicopters need a mechanism to neutralize the yawing movement produced by the single large rotor. This is commonly accomplished by a tail rotor, coaxial rotors, and the NOTAR systems. Tandem-rotor helicopters, however, use counter-rotating rotors, with each cancelling out the other's torque.