Coaxial-rotor aircraft: Difference between revisions

Having two coaxial sets of rotors provides symmetry of forces around the central axis for lifting the vehicle and laterally when flying in any direction. Because of the mechanical complexity, many helicopter designs use alternate configurations to avoid problems that arise when only one axismain rotor is used. Common alternatives are single-rotor helicopters or [[Tandem rotors|tandem rotor]] arrangements.

Coaxial rotors solve the problem of main rotor torque by turning each set of rotors in opposite directions. The opposite torques from the rotors cancel each other out. Rotational maneuvering, [[Yaw (rotation)|yaw]] control, is accomplished by increasing the collective pitch of one rotor and decreasing the collective pitch on the other. This causes a controlled dissymmetry of torque.

Another benefit arising from a coaxial design includes increased payload for the same engine power; a tail rotor typically wastes some of the available engine power that would be fully devoted to lift and thrust with a coaxial design. Reduced noise is the main advantage of the configuration; some of the loud "spanking" sound associated with conventional helicopters arises from interaction between the airflows from the main and tail rotors, which in some designs can be severe. Also, helicopters using coaxial rotors tend to be more compact (with a smaller footprint on the ground), though at the price of increased height, and consequently have uses in areas where space is at a premium; several Kamov designs are used in [[navy|naval]] roles, being capable of operating from confined spaces on the decks of ships, including ships other than [[aircraft carrier]]s (an example being the [[Kara-class cruiser]]s of the Russian navy, which carry a [[Kamov Ka-25|Ka-25]] 'Hormone' helicopter as part of their standard equipment). Another benefit is increased safety on the ground; the absence of a tail rotor eliminates the major source of injuries and fatalities to ground crews and bystanders.{{Citation needed|date=November 2019}}

The U.S. Department of Transportation has published a “Basic Helicopter Handbook”. One of the chapters in it is titled, “Some Hazards of Helicopter Flight'. Ten hazards have been listed to indicate what a typical single rotor helicopter has to deal with. The coaxial rotor design either reduces or completely eliminates many of these hazards. The following list indicates which: