A rotor wing is a lifting

rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...

wing A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...

which spins to provide aerodynamic lift. In general, a rotor may spin about an axis which is aligned substantially either vertically or side-to-side (spanwise). All three classes have been studied for use as lifting rotors and several variations have been flown on full-size aircraft, although only the vertical-axis

rotary wing A rotary-wing aircraft, rotorwing aircraft or rotorcraft is a heavier-than-air aircraft with rotary wings that spin around a vertical mast to generate lift. Part 1 (Definitions and Abbreviations) of Subchapter A of Chapter I of Title 14 of the U ...

has become widespread on

rotorcraft A rotary-wing aircraft, rotorwing aircraft or rotorcraft is a heavier-than-air aircraft with rotor wing, rotary wings that spin around a vertical mast to generate lift (force), lift. Part 1 (Definitions and Abbreviations) of Subchapter A of Chapt ...

such as the

helicopter A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and ...

. Some types provide lift at zero forward airspeed, allowing for

vertical takeoff and landing A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-wing ...

(VTOL), as in the

. Others, especially unpowered free-spinning types, require forward airspeed in the same manner as a

fixed-wing aircraft A fixed-wing aircraft is a heavier-than-air aircraft, such as an airplane, which is capable of flight using aerodynamic lift. Fixed-wing aircraft are distinct from rotary-wing aircraft (in which a rotor mounted on a spinning shaft generate ...

, as in the

autogyro An autogyro (from Greek and , "self-turning"), gyroscope, gyrocopter or gyroplane, is a class of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. A gyroplane "means a rotorcraft whose rotors are not engine-d ...

. Many can also provide forward thrust if required.

Types

Many ingenious ways have been devised to convert the spinning of a rotor into aerodynamic

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 ...

. The various types of such rotor wings may be classified according to the axis of the rotor. Types include:Foshag & Boehler (1969)Seifert (2012) ;Vertical-axis *Conventional rotary wings as used by modern

. ;Spanwise horizontal-axis *Wing rotor: an airfoil-section horizontal-axis rotor which creates the primary lift. *Magnus rotor: a rotor which creates lift via the Magnus effect. ** Flettner rotor: a smooth cylindrical Magnus rotor with disc end plates. **Thom rotor: a smooth spinning cylinder with multiple discs along the span. *Cycloidal rotor or

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 w ...

: a set of horizontal lifting aerofoils rotating around the rim of a supporting horizontal-axis rotor. (May be powered or unpowered.) An aircraft with a cycloidal rotor wing is called a

cyclogyro The cyclogyro, or cyclocopter, is an aircraft configuration that uses a horizontal-axis cyclorotor as a rotor wing to provide lift and, sometimes, also propulsion and control. In principle, the cyclogyro is capable of VTOL, vertical take off and ...

. Some examples are hybrids comprising a cycloidal rotor around a central Magnus cylinder. *Cross-flow fan: a slatted cylindrical fan in a shaped duct. ;Longitudinal horizontal-axis *Radial-lift rotor: a substantially fore-aft axis rotor which creates lift through cyclic pitch variation. **Self-propelling wing or Radial-lift rotor: a propeller or rotor with the rotation axis angled to the airflow to create a cyclic variation in pitch and hence a radial lift component. **Radial-lift propeller with cyclic pitch control: a propeller capable of generating a sideways lift component.

Conventional rotary wings

Conventional rotorcraft have vertical-axis rotors. The main types include the

with powered rotors providing both lift and thrust, and the

with unpowered rotors providing lift only. There are also various hybrid types, especially the

gyrodyne A gyrodyne is a type of VTOL aircraft with a helicopter rotor-like system that needs to be driven by its engine only for takeoff and landing, and includes one or more conventional propeller or jet engines to provide thrust during cruising flig ...

which has both a powered rotor and independent forward propulsion, and the stopped rotor in which the rotor stops spinning to act as a

fixed wing A fixed-wing aircraft is a heavier-than-air aircraft, such as an airplane, which is capable of flight using aerodynamic lift. Fixed-wing aircraft are distinct from rotary-wing aircraft (in which a rotor mounted on a spinning shaft generates ...

in forward flight.

Magnus rotors

When a spinning body passes through air at right angles to its axis of spin, it experiences a sideways force in the third dimension. This

Magnus effect The Magnus effect is a phenomenon that occurs when a spin (geometry), spinning Object (physics), object is moving through a fluid. A lift (force), lift force acts on the spinning object and its path may be deflected in a manner not present when ...

was first demonstrated on a spinning cylinder by

Gustav Magnus Heinrich Gustav Magnus (; 2 May 1802 – 4 April 1870) was a German experimental scientist. His training was mostly in chemistry but his later research was mostly in physics. He spent the great bulk of his career at the University of Berlin, wher ...

in 1872. If the cylinder axis is aligned spanwise (side to side) then forward movement through the air generates lift. The rotating body does not need to be a cylinder and many related shapes have been studied.

Flettner rotor

The Flettner rotor comprises a Magnus cylinder with a disc endplate at each end. The American

Plymouth A-A-2004 The Plymouth A-A-2004 is a rotor aircraft inspired by the Flettner rotor, a type of rotor that uses the Magnus effect The Magnus effect is a phenomenon that occurs when a spin (geometry), spinning Object (physics), object is moving through a ...

floatplane A floatplane is a type of seaplane with one or more slender floats mounted under the fuselage to provide buoyancy. By contrast, a flying boat uses its fuselage for buoyancy. Either type of seaplane may also have landing gear suitable for land, ...

had Flettner rotors in place of the main wings and achieved short flights in 1924.

Cross-flow fan

The

cross-flow fan A fan is a powered machine that creates airflow. A fan consists of rotating vanes or blades, generally made of wood, plastic, or metal, which act on the air. The rotating assembly of blades and hub is known as an ''impeller'', ''rotor'', or ''ru ...

comprises an arrangement of blades running parallel to a central axis and aligned radially, with the fan partially or fully enclosed in a shaped duct. Due to the specific shaping, rotating the fan causes air to be drawn in at one end of the duct, passed across the fan and expelled at the other end. The

FanWing The FanWing is a type of aircraft rotor wing in which a horizontal-axis cross-flow fan is used in close conjunction with a fixed wing. The fan forces airflow over the fixed surface to provide both lift and forward thrust. The concept was initially ...

is a lifting rotor which uses this principle. It can both provide forward thrust by expelling air backwards and augment lift, even at very low airspeeds, by also drawing the air downwards. A prototype UAV was flown in 2007.

Radial-lift rotors

During World War II

Focke-Wulf Focke-Wulf Flugzeugbau AG () was a German manufacturer of civil and military aircraft before and during World War II. Many of the company's successful fighter aircraft designs were slight modifications of the Focke-Wulf Fw 190. It is one of the ...

proposed the Triebflügel, in which a tipjet-driven rotor wing is located around the fuselage waist. The proposed mode of operation was to land and take off as a

tail-sitter A tail-sitter, or tailsitter, is a type of VTOL aircraft that takes off and lands on its empennage, tail, then tilts horizontally for forward flight. Originating in the 1920s with the inventor Nikola Tesla, the first aircraft to adopt a tail-sit ...

, using the wing as a conventional rotor. The craft would then tilt over to horizontal flight and lift would be provided by cyclic pitch variation of the rotor wings, with the wing tip

ramjets A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around and can operate up to . Ramjets can be particularly appropriat ...

now angled to provide forward thrust.Sharp, D.; ''Luftwaffe: Secret Jets of the Third Reich'', Mortons, 2015, Pages 98-101. A few years later the American

Vought XF5U The Vought XF5U "Flying Flapjack" was an experimental U.S. Navy fighter aircraft designed by Charles H. Zimmerman for Vought during World War II. This unorthodox design consisted of a flat, somewhat disc-shaped body (resembling a flying flapj ...

circular-winged fighter prototype was designed with large radial-lift propellers. These were angled upwards when the craft was on the ground, creating a cyclic variation in the blades' angle of attack or pitch when the craft was moving forwards. This cyclic variation induced a radial lifting component to the blades, when in the horizontal segment of rotation, which was intended to augment the wing lift. A prototype aircraft was completed but the project was closed before the prototype had flown.

References

Citations

{{reflist, 1

Bibliography

*Foshag, W.F. and Boehler, G.D.;
Review and Preliminary Evaluation of Lifting Horizontal-Axis Rotating-Wing Aeronautical Systems (HARWAS)
', Aerophysics Co., 1969. *Seifert, Jost; "A Review of the Magnus Effect in Aeronautics", ''Progress in Aerospace Sciences'' Vol. 55, Elsevier, 2012, pages 17–45. Experimental aircraft VTOL aircraft Aircraft configurations