A rotorcraft or rotary wing aircraft is a heavier-than-air flying machine that uses lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

 generated by wings
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....

, called rotor blades, that revolve around a mast. Several rotor blades mounted to a single mast are referred to as a rotor
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...

. The International Civil Aviation Organization
International Civil Aviation Organization
The International Civil Aviation Organization , pronounced , , is a specialized agency of the United Nations. It codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth...

 (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors". Rotorcraft generally include those aircraft where one or more rotors are required to provide lift throughout the entire flight, such as helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

s, cyclocopters
The cyclogyro, or cyclocopter, is an aircraft design that uses Cycloidal Rotors which consist of airfoils rotating around a horizontal axis for both lift and thrust...

, autogyro
An autogyro , also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust...

s, and gyrodynes. Compound rotorcraft may also include additional thrust engines or propellers and static lifting surfaces.


A helicopter is a rotorcraft whose rotors are driven by the engine(s) throughout the flight, to allow the helicopter to take off vertically, hover, fly forwards, backwards and laterally, as well as to land vertically. Helicopters have several different configurations of one or more main rotors.

Helicopters with one driven main rotor require some sort of antitorque device such as a tail rotor
Tail rotor
The tail rotor, or anti-torque 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 the same direction as...

, fantail
A Fenestron is a shrouded tail rotor of a helicopter that is essentially a ducted fan. The housing is integral with the tail skin, and, like the conventional tail rotor it replaces, is intended to counteract the torque of the main rotor...

, or NOTAR
NOTAR is the name of a helicopter anti-torque system which replaces the use of a tail rotor. Developed by McDonnell Douglas Helicopter Systems , the name is an acronym derived from the phrase NO TAil Rotor...

, except some rare examples of helicopters using tip jet propulsion which generates almost no torque.


An autogyro (sometimes called gyrocopter, gyroplane, or rotaplane) utilizes an unpowered rotor driven by aerodynamic forces in a state of autorotation
In aviation, autorotation refers to processes in both fixed-wing and rotary-wing aircraft. The term means significantly different things in each context....

 to develop lift, and an engine-powered propeller
Propeller (aircraft)
Aircraft propellers or airscrews convert rotary motion from piston engines or turboprops to provide propulsive force. They may be fixed or variable pitch. Early aircraft propellers were carved by hand from solid or laminated wood with later propellers being constructed from metal...

, similar to that of a fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

, to provide thrust. While similar to a helicopter rotor in appearance, the autogyro's rotor must have air flowing up and through the rotor disk in order to generate rotation. Early autogyros resembled the fixed-wing aircraft of the day, with wings and a front-mounted engine and propeller in a tractor configuration to pull the aircraft through the air. Late-model autogyros feature a rear-mounted engine and propeller in a pusher configuration.

The autogyro was invented in 1920 by Juan de la Cierva
Juan de la Cierva
Juan de la Cierva y Codorníu, 1st Count of De La Cierva was a Spanish civil engineer, pilot and aeronuatical engineer. His most famous accomplishment was the invention in 1920 of the Autogiro, a single-rotor type of aircraft that came to be called autogyro in the English language...



The rotor of a gyrodyne is normally driven by its engine for takeoff and landing—hovering like a helicopter—with anti-torque and propulsion for forward flight provided by one or more propellers mounted on short or stub wings. As power is increased to the propeller, less power is required by the rotor to provide forward thrust resulting in reduced pitch angles and rotor blade flapping. At cruise speeds with most or all of the thrust being provided by the propellers, the rotor receives power only sufficient to the amount needed to overcome the profile drag and maintain lift. The effect is a rotorcraft operating in a more efficient manner than the freewheeling rotor of an autogyro in autorotation, and minimizing the adverse effects of retreating blade stall of helicopters at higher airspeeds.

Number of blades

A rotary wing is characterised by the number of blades. Typically this is between two and six per driveshaft.

Number of rotors

A rotorcraft may have one or more rotors. Various rotor configurations have been used:
  • One rotor. Powered rotors require compensation for the torque reaction causing yaw, except in the case of tipjet drive.
  • Two rotors. These typically rotate in opposite directions cancelling the torque reaction so that no tail rotor or other yaw stabiliser is needed. These rotors can be laid out as
    • Tandem - One in front of the other.
    • Transverse
      Transverse rotors
      Transverse rotor rotorcraft have two large horizontal rotor assemblies mounted side by side.Single rotor helicopters need a tail rotor to neutralize the twisting moment produced by the single large rotor. Tandem rotor helicopters, however, use counter-rotating rotors, with each canceling out the...

       - Side by side.
    • Coaxial - One rotor disc above the other, with concentric drive shafts.
    • Intermeshing rotors
      Intermeshing rotors
      Intermeshing rotors on a helicopter are a set of two rotors turning in opposite directions, with each rotor mast mounted on the helicopter with a slight angle to the other, in a transversely symmetrical manner, so that the blades intermesh without colliding. The arrangement allows the helicopter to...

       - Twin rotors at an acute angle from each other, whose nearly-vertical driveshafts are geared together to synchronise their rotor blades so that they intermesh, also called a synchropter.
  • Three rotors. An uncommon configuration; the 1948 Cierva Air Horse
    Cierva Air Horse
    -References:NotesReferences* Copies of entries in "The Complete Encyclopedia of World Aircraft", 1997. by D.Donald and "Helicopters and Autogyros of the World", 1958 by P.Lambermont. Hosted at Accessed January 2008...

     had three rotors as it was not believed a single rotor of sufficient strength could be built for its size. All three rotors turned in the same direction and yaw compensation was provided by inclining each rotor axis to generate rotor thrust components that opposed torque.
  • Four rotors. Also referred to as quadrotor
    A quadrotor, also called a quadrotor helicopter or quadrocopter, is an aircraft that is lifted and propelled by four rotors. Quadrotors are classified as rotorcraft, as opposed to fixed-wing aircraft, because their lift is derived from four rotors...

    s, they typically have two rotors turning clockwise and two counter-clockwise.
  • More than four rotors are uncommon. These designs, referred to as multirotor
    A multirotor or multicopter is a rotorcraft with more than two rotors. Multirotors often use fixed-pitch blades, whose rotor pitch does not vary as the blades rotate; control of vehicle motion is achieved by varying the relative speed of each rotor to change the thrust and torque produced by...

    s, have matched sets of rotors turning in opposite directions.

See also

History of rotorcraft:
Types of aircraft:
  • Fixed-wing aircraft
    Fixed-wing aircraft
    A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

  • VTOL
    A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...

  • Powered lift
    Powered lift
    Powered lift or powered-lift refers to a type of aircraft that can take off and land vertically and functions differently from a rotorcraft in horizontal flight....

  • Tiltrotor
    A tiltrotor is an aircraft which uses a pair or more of powered rotors mounted on rotating shafts or nacelles at the end of a fixed wing for lift and propulsion, and combines the vertical lift capability of a helicopter with the speed and range of a conventional fixed-wing aircraft...

  • Tiltwing
    A tiltwing aircraft features a wing that is horizontal for conventional forward flight and rotates up for vertical takeoff and landing. It is similar to the tiltrotor design where only the propeller and engine rotate. Tiltwing aircraft are typically fully capable of VTOL operations.The tiltwing...

  • Fanwing
    FanWing or fan wing is a concept for a type of aircraft. It is distinct from existing types of aircraft like airplanes and helicopters in using a fixed wing with a forced airflow produced by cylindrical fan mounted at the leading edge of the wing....

External links

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