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A multirotor or multicopter is a 
In order to allow more power and stability at reduced weight,
A multirotor or multicopter is a rotorcraft
A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft with rotary wings or rotor blades, which generate lift by rotating around a vertical mast. Several rotor blades mounted on a single mast are referred to as a rotor. The Internati ...
with more than two lift
Lift or LIFT may refer to:
Physical devices
* Elevator, or lift, a device used for raising and lowering people or goods
** Paternoster lift, a type of lift using a continuous chain of cars which do not stop
** Patient lift, or Hoyer lift, mobile ...
-generating rotor
Rotor may refer to:
Science and technology
Engineering
*Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator
* Helicopter rotor, the rotary wing(s) of a rotorcraft ...
s. An advantage of multirotor aircraft is the simpler rotor mechanics required for flight control. Unlike single- and double-rotor helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
s which use complex variable pitch rotor
Blade pitch or simply pitch refers to the angle of a blade in a fluid. The term has applications in aeronautics, shipping, and other fields.
Aeronautics
In aeronautics, blade pitch refers to the angle of the blades of an Propeller (aeronautic ...
s whose pitch varies as the blade rotates for flight stability and control, multirotors often use fixed- pitch blades; control of vehicle motion is achieved by varying the relative speed of each rotor to change the thrust and torque produced by each.
Due to their ease of both construction and control, multirotor aircraft are frequently used in radio control aircraft and unmanned aerial vehicle (UAV) (drone) projects in which the names tricopter, quadcopter
A quadcopter or quadrotor is a type of helicopter with four Helicopter rotor, rotors.
Although quadrotor helicopters and convertiplanes have long been flown experimentally, the configuration remained a curiosity until the arrival of the moder ...
, hexacopter and octocopter are frequently used to refer to 3-, 4-, 6- and 8-rotor rotorcraft, respectively. There is also the X8 (also called ''octo-quad'') configuration that is similar to the quadracopter design, except that it has eight rotors; the lower of which have a reversed rotation direction.
In order to allow more power and stability at reduced weight, coaxial rotor
Coaxial rotors or coax rotors are a pair of helicopter rotors 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 helicop ...
s can be employed, in which each arm has two motors, running in opposite directions which cancels out rotational torque (one facing up and one facing down).
Also possible is the addition of horizontal propellers These types of rotorcraft (which have just 4 vertical propellers) are called quadplanes.
Rotor Configurations
*Coaxial rotors
Coaxial rotors or coax rotors are a pair of helicopter rotors 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 helicopt ...
* Cyclorotor
A cyclorotor, cycloidal rotor, cycloidal propeller or cyclogiro, is a fluid propulsion device that converts shaft power into the acceleration of a fluid using a rotating axis perpendicular to the direction of fluid motion. It uses several blades wi ...
* Intermeshing rotors
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. T ...
* Tail rotor
The tail rotor is a smaller rotor mounted vertically or near-vertically at the tail of a traditional single-rotor helicopter, where it rotates to generate a propeller-like horizontal thrust in the same direction as the main rotor's rotation. The ...
* Tandem rotors
Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction.
The original use of the term in English was in ''tandem harness'', which is used for two ...
* Transverse rotors
Transverse rotor aircraft have two large horizontal rotor assemblies mounted side by side.
Single-rotor helicopters (unicopters) need an additional tail rotor or tail exhaust to neutralize the reactional angular momentum produced by the mai ...
Examples
*de Bothezat helicopter
The de Bothezat helicopter, also known as the Jerome-de Bothezat Flying Octopus, was an experimental quadrotor helicopter built for the United States Army Air Service by George de Bothezat in the early 1920s, and was said at the time to be the ...
- an American four-rotor helicopter that first flew on December 18, 1922.
* Cierva Air Horse
The Cierva W.11 Air Horse was a helicopter developed by the Cierva Autogiro Company in the United Kingdom during the mid-1940s. The largest helicopter in the world at the time of its debut, the Air Horse was unusual for using three rotors mounted ...
- a British three-rotor "heavy lift" helicopter first flying in 1948. Three rotors were used to give a large lift without compromising rotor strength.
* Volocopter
Volocopter GmbH (formerly called E-Volo GmbH) is a German aircraft manufacturer based in Bruchsal (near Karlsruhe) and founded by Alexander Zosel and Stephan Wolf. The company specializes in the design of electric multirotor helicopters in the f ...
designs - a series of German prototype electric multicopters with 18 rotors, the first electric multicopter in the world to achieve crewed flight. The large number of low-cost motors make it economical, quiet and provide redundancy with ability to maintain control with up to four failed motors.
References
Multirotor helicopters {{Component-aircraft-stub