A circulation control wing (CCW) is a form of

high-lift device In aircraft design and aerospace engineering, a high-lift device is a component or mechanism on an aircraft's wing that increases the amount of lift produced by the wing. The device may be a fixed component, or a movable mechanism which is deplo ...

for use on the main wing of an aircraft to increase the maximum

lift coefficient In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...

. CCW technology has been in the research and development phase for over sixty years. Blown flaps were an early example of CCW. The CCW works by increasing the velocity of the airflow over the

leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...

and

trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 199 ...

of a specially designed aircraft

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 e ...

using a series of blowing slots that eject jets of high-pressure air. The wing has a rounded trailing edge to tangentially eject the air through the Coandă effect thus causing lift. The increase in

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

of the airflow over the wing also adds to the lift force through conventional airfoil lift production.

Purpose

The main purpose of the circulation control wing is to increase the lifting force of an aircraft at times when large lifting forces at low speeds are required, such as

takeoff Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a ...

and

landing Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or ...

. Wing flaps and slats are currently used during landing on almost all aircraft and on takeoff by larger jets. While flaps and slats are effective in increasing lift, they do so at a high cost of drag. The benefit of the circulation control wing is that no extra drag is created and the lift coefficient is greatly increased. It is being claimed that such a system could increase the maximum coefficient of lift in the landing configuration of a

Boeing 737 The Boeing 737 is a narrow-body aircraft produced by Boeing at its Boeing Renton Factory, Renton Factory in Washington (state), Washington. Developed to supplement the Boeing 727 on short and thin routes, the twinjet retains the Boeing 707, 7 ...

by 150% to 250%, thus reducing approach speeds by 35% to 45% and landing distances by 55% to 75%; such advances in wing design could allow for a dramatic reduction in the size of the wing of a large jet airplane.

Other uses

Increased maneuverability

At low speeds, an aircraft has reduced airflow over the

and

vertical stabilizer A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, s ...

. This causes the control surfaces (

ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

elevator An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They a ...

s and

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...

) to be less effective. The CCW system increases the airflow over these surfaces and consequently can allow much higher maneuverability at low speeds.{{cite web, url=http://www.airspacemag.com/issues/2007/april-may/custer_channel_wing.php?page=2, archive-url=https://archive.today/20120716165638/http://www.airspacemag.com/issues/2007/april-may/custer_channel_wing.php?page=2, url-status=dead, archive-date=2012-07-16, title=Circulation Control Technology, accessdate=2007-12-15 However, if one of the CCW systems should fail at low speed, the affected wing is likely to stall which could result in an inescapable spin. Finally, the CCW system could be used on multi-engine aircraft in the result of an engine failure to cancel the asymmetric forces from the loss of power on one wing.

Noise reduction

The use of a CCW system eliminates the need for large complex components in the free stream such as flaps and slats, greatly reducing the

noise pollution Noise pollution, also known as environmental noise or sound pollution, is the propagation of noise with ranging impacts on the activity of human or animal life, most of them are harmful to a degree. The source of outdoor noise worldwide is ma ...

of modern aircraft. Additionally, a much shorter ground roll coupled with steeper climb outs and approaches reduces the ground noise footprint. The blowing slots themselves will contribute very little to the noise of the aircraft as each slot is just a fraction of an inch wide.

Powering the wing

The main problem with the circulation control wing is the need for high energy air to be blown over the wing's surface. Such air is often bled from the engine; however, this drastically reduces engine power production and consequently counteracts the purpose of the wing. Other options are taking the exhaust gases (which must first be cooled) or using multiple, lightweight gas generators, which are separate from the main aircraft engines.

Purpose

Other uses

Increased maneuverability

Noise reduction

Powering the wing

References

See also