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The FanWing is an aircraft configuration in which a horizontal-axis cross-flow fan is used in close conjunction with 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 ...
. The fan forces airflow over the fixed surface to provide both lift and forward thrust. The concept was initially developed around 1997 by designer Patrick Peebles and is under development by his company FanWing Ltd. As of December 2018, only experimental drones have been flown.


Principles of operation

A cross-flow fan comprises blades radiating from a central axis and aligned with the axis, similar to those of a cylinder mower. It is contained in a duct which is shaped so that when the fan spins, it induces a directional airflow. In the FanWing, the fan is set above the leading section of a fixed wing and extends the full span of the wing. The wing upper surface is shaped around the fan to form a half-duct. The wing chord extends approximately as far again back from the fan, with the rear section shaped as a wedge-like fairing that extends to the
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, 1997. ...
. When the fan spins with the upper edge moving backwards and the lower edge forwards, the fixed half-duct is shaped to create a net backward flow of air, resulting in forward thrust. This backward flow over the upper surfaces also creates a net circulation of air around the rotor-wing combination, resulting in vertical lift. Addition of an
outboard tail An outboard tail is a type of aircraft tail or empennage which is split in two, with each half mounted on a short boom just behind and outboard of each wing tip. It comprises outboard horizontal stabilizers (OHS) and may or may not include addition ...
recovers energy from the wing tip vortices to significantly increase overall efficiency. This in turn allows an even lower minimum forward speed.Could FanWing go from LSA to heavy lifter?
Robert Coppinger, Aircraft Owners and Pilots Association, November 22, 2011. Accessed June 2012


Advantages

In addition to providing forward thrust in its own right, the radial fan increases the velocity of the airflow over the wing's upper surface independently of the forward motion of the aircraft, thereby creating useful lift at forward speeds lower than the stalling speed for a conventional wing.


Limitations

Besides the added weight and complexity of the fan system, it has some limitations compared with a conventional fixed wing: * The fan speed directly affects pitch. This means that, paradoxically, increasing the engine power can decelerate the aircraft. * Glide ratio in case of power failure is low (about 1:3) but if the rotors are allowed to auto-rotate, the aircraft can still glide. * The rotating fan can cause
gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotat ...
effects which can affect manoeuvrability.


History

Although the cross-flow fan has been known since the late nineteenth century, its use as a rotary aircraft wing was not studied until 1997 when Patrick Peebles, an American based in the UK, conceived of it as a
STOL A short takeoff and landing (STOL) aircraft is a conventional fixed-wing aircraft that has short runway requirements for takeoff and landing. Many STOL-designed aircraft also feature various arrangements for use on airstrips with harsh condition ...
device and subsequently formed the FanWing Co. Wind tunnel tests and powered model flights were supported by UK government funding, winning SMART grant awards in 2002 and 2003. Work began on a prototype drone, ostensibly aimed at the STOL urban surveillance market. The benefits of adding a tail were discovered during continued development. By 2014, support for wind tunnel tests of a 1.5 meter wing section was being provided through EU sources including €783,000 through the
German Aerospace Center The German Aerospace Center (german: Deutsches Zentrum für Luft- und Raumfahrt e.V., abbreviated DLR, literally ''German Center for Air- and Space-flight'') is the national center for aerospace, energy and transportation research of Germany ...
.Warwick, Graham.
Intermodal-container Air Cargo Concepts Attract Interest (Cargo Cult)
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Aviation Week & Space Technology ''Aviation Week & Space Technology'', often abbreviated ''Aviation Week'' or ''AW&ST'', is the flagship magazine of the Aviation Week Network. The weekly magazine is available in print and online, reporting on the aerospace, defense and aviati ...
'' page 15, 25 August 2014. Accessed: 26 August 2014.
As of December 2018, only unmanned development prototypes have flown.


See also

*
Flettner airplane A Flettner airplane is a type of rotor airplane which uses a Flettner rotor to provide lift. The rotor comprises a spinning cylinder with circular end plates and, in an aircraft, spins about a spanwise horizontal axis. When the aircraft moves f ...
*
Rotary-wing aircraft 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 Internat ...
*
Ornithopter An ornithopter (from Greek language, Greek ''ornis, ornith-'' "bird" and ''pteron'' "wing") is an aircraft that flight, flies by flapping its wings. Designers sought to imitate the flapping-wing flight of birds, bats, and insects. Though machine ...
*
Gyroplane 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. Whi ...


References & notes


External links

{{Commonscat, FanWings
FanWing Ltd
company website
Image of research model with early tail configuration
''FlightGlobal'' (Archived copy). Aircraft configurations Aircraft wing design