A rotor wing is a lifting

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 ...

wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is exp ...

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 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 ...

has become widespread on

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 Inter ...

such as the

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 attribut ...

. Some types provide lift at zero forward airspeed, allowing for vertical takeoff and landing (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, flying machine, such as an airplane, which is capable of flight using wings that generate Lift (force), lift caused by the aircraft's forward airspeed and the wing configuration, shape of ...

, as in the

autogyro An autogyro (from Greek and , "self-turning"), also known as a ''gyroplane'', is a type of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. Forward thrust is provided independently, by an engine-driven propeller. ...

. 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 wi ...

: 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 vertical take off and landing ...

. 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 is driven by its engine for takeoff and landing only, and includes one or more conventional propeller or jet engines to provide forward 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 flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinc ...

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 an observable phenomenon commonly associated with a spinning object moving through a fluid. The path of the spinning object is deflected in a manner not present when the object is not spinning. The deflection can be ex ...

was first demonstrated on a spinning cylinder by Gustav Magnus 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

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 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 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 tail, then tilts horizontally for forward flight. Originating in the 1920s with the inventor Nikola Tesla, the first aircraft to adopt a tail-sitter configur ...

, 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 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 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

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.

External links

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StopRotor video
Experimental aircraft VTOL aircraft Aircraft configurations