helicopter (redirected from Helicoptor)

helicopter, type of aircraft in which lift is obtained by means of one or more power-driven horizontal propellers called rotors. When the rotor of a helicopter turns it produces reaction torque which tends to make the craft spin also. On most helicopters a small rotor near the tail compensates for this torque. On twin-rotor craft the rotors spin in opposite directions, so their reactions cancel each other. The helicopter is propelled in a given direction by inclining the axis of the main rotor in that direction. The helicopter's speed is limited by the fact that if the blades rotate too fast they will produce compressibility effects on the blade moving forward and stall effects on the rearward–moving blade, at the same time. This method of flight was considered by Leonardo da Vinci, in the 16th cent., who described its possibilities but could not provide a propulsion system. Best known among its developers are the French inventor Louis Breguet and the engineers Igor Sikorsky of the United States and Juan de la Cierva of Spain. The helicopter has become very popular for short-distance transportation, because of its maneuverability and ability to land and take off in small areas; it has been adopted for a wide range of services, including air-sea rescue, fire fighting, traffic control, oil platform resupply, and business transportation. Helicopters have been widely adopted by the military since their first appearance during the Korean War. During the Vietnam War, they became the preferred platforms for transporting troops and evacuating wounded; in the Persian Gulf conflict helicopter gunships provided air cover for advancing tanks.

Bibliography

See A. Gessow and G. C. Myers, Aerodynamics of the Helicopter (1967); W. Johnson, Helicopter Theory (1984).

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helicopter

Aircraft with one or more power-driven horizontal rotors that enable it to take off and land vertically, move in any direction, or remain stationary in the air. Since a rotor is essentially a rotating airfoil, a helicopter is often described as a rotary-wing aircraft, in contrast to a conventional fixed-wing airplane. One of the earliest ideas for flying, it appeared in China and Renaissance Europe as a toy and in Leonardo da Vinci's designs. The Frenchman Paul Cornu made the first manned flight in 1907. Igor Sikorsky produced the first successful prototype in 1939, which was followed by rapid development in the U.S. and Europe. It is widely used for civilian transport, rescue work, and various commercial purposes. It has been used by military forces since the Korean War (1950–53) for transporting material, moving assault troops, and directly attacking other forces.

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helicopter

an aircraft capable of hover, vertical flight, and horizontal flight in any direction. Most get all of their lift and propulsion from the rotation of overhead blades
www.helicoptermuseum.org/museum/links.htm
www.helikopter.li

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helicopter [′hel·ə‚käp·tər]

(aerospace engineering)

An aircraft fitted to sustain itself by motor-driven horizontal rotating blades (rotors) that accelerate the air downward, providing a reactive lift force, or accelerate the air at an angle to the vertical, providing lift and thrust.

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Helicopter

An aircraft characterized by its large-diameter, powered, rotating blades. The helicopter can lift itself vertically by the reactive force generated as the rotating blades accelerate air downward. It can both lift and propel itself by accelerating air downward at an angle to the vertical. The helicopter is the most successful vertical takeoff and landing (VTOL) aircraft developed, by virtue of its relatively high efficiency in performing hovering and low-speed flight missions.

The key to understanding the operation and control of a helicopter lies in a knowledge of the forces and resultant motion of each rotor blade as momentum is imparted to the air. Unlike a fixed-wing aircraft, which derives its lift from the translational motion of the fuselage and airfoil-shaped wing relative to the air, the helicopter rotates its wings (or rotor blades) about a vertical shaft and thus is able to generate lift when the fuselage remains stationary.

Many different rotor arrangements have been used, and most of the early attempts at vertical flight were made with machines having multiple or coaxial counterrotating rotors. Most modern helicopters employ the single rotor or the tandem rotor configurations.

In addition to the selection of the number and location of the lifting rotors, designers have developed varied methods for attaching the blades to the rotor hub. Very early experiments conducted with the blades rigidly attached to the hub were unsatisfactory because of the excessive moments applied to the rotor mast. Based on the success achieved by the introduction of hinged attachments for the rotor blades, several configurations have been successfully manufactured. The teetering rotor used on two-bladed configurations has one central hinge which allows the blades to move in unison (one up, one down) like a seesaw. The gimbaled rotor is essentially equivalent to the teetering rotor and has been used on rotors with three or more blades. The articulated rotor has each blade attached to the hub by its own flapping hinge.

The growth of the helicopter industry in the United States is founded in the uses made by the armed forces. The technology which evolved to meet the needs of the military provided the base for an impressive growth in commercial applications. With such diverse operations as crop spraying, logging, construction, police and ambulance service, and passenger and corporate transportation, the industry has responded with a variety of commercial helicopters. See Vertical takeoff and landing (VTOL)