Multirotors make use of three or more rotors.Aircraft utilizing this is known as a synchropter. Intermeshing rotors are two counter-rotating rotors mounted close to each other at a sufficient angle to let the rotors intermesh over the top of the aircraft without colliding.Coaxial rotors are two counter-rotating rotors mounted one above the other with the same axis.Now used on tiltrotors, some early model helicopters had used them. Transverse rotors are pair of counter-rotating rotors transversely mounted at the ends of fixed wings or outrigger structures.Tandem rotors are two counter-rotating rotors with one mounted behind the other.There are several common configurations that use the counter-rotating effect to benefit the rotorcraft: This allows the power normally required to be diverted for the tail rotor to be applied fully to the main rotors, increasing the aircraft's power efficiency and lifting capacity. The use of two or more horizontal rotors turning in opposite directions is another configuration used to counteract the effects of torque on the aircraft without relying on an anti-torque tail rotor. NOTAR provides anti-torque similar to the way a wing develops lift through the use of the Coandă effect on the tail boom. Some helicopters use other anti-torque controls instead of the tail rotor, such as the ducted fan (called Fenestron or FANTAIL) and NOTAR. The tail rotor pushes or pulls against the tail to counter the torque effect, and this has become the most common configuration for helicopter design, usually at the end of a tail boom. The design that Igor Sikorsky settled on for his VS-300 was a smaller tail rotor. Most helicopters have a single main rotor, but torque created by its aerodynamic drag must be countered by an opposed torque. There are three basic types: hingeless, fully articulated, and teetering although some modern rotor systems use a combination of these. Main rotor systems are classified according to how the rotor blades are attached and move relative to the hub. At the top of the mast is the attachment point for the rotor blades called the hub. The mast is a cylindrical metal shaft that extends upwards from the transmission. The rotor consists of a mast, hub and rotor blades. A rotor system may be mounted horizontally, as main rotors are, providing lift vertically, or it may be mounted vertically, such as a tail rotor, to provide horizontal thrust to counteract torque from the main rotors. The rotor system, or more simply rotor, is the rotating part of a helicopter that generates lift. In the United States military, the common slang is "helo" pronounced with a long "e". English language nicknames for "helicopter" include "chopper", "copter", "heli", and "whirlybird". For various reasons, the word is often erroneously, from an etymological point of view, analysed by English speakers into heli- and copter, leading to words like helipad and quadcopter. The English word helicopter is adapted from the French word hélicoptère, coined by Gustave Ponton d'Amécourt in 1861, which originates from the Greek helix ( ἕλιξ) "helix, spiral, whirl, convolution" and pteron ( πτερόν) "wing". Quadrotor helicopters ( quadcopters) were pioneered as early as 1907 in France, and along with other types of multicopters, have been developed mainly for specialized applications such as drones. However, twin-main rotor helicopters (bicopters), in either tandem or transverse rotors configurations, are sometimes in use due to their greater payload capacity than the monorotor design, and coaxial-rotor, tiltrotor, and compound helicopters are also all flying today. unicopter, not to be confused with the single-blade monocopter) has become the most common helicopter configuration. Īlthough most earlier designs used more than one main rotor, the configuration of a single main rotor accompanied by a vertical anti-torque tail rotor (i.e. In 1942, the Sikorsky R-4 became the first helicopter to reach full-scale production. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing ( STOL) or short take-off and vertical landing ( STOVL) aircraft cannot perform without a runway. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. A Bell 206 helicopter operated by the Los Angeles Police Department Air Support DivisionĪ helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors.
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