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FanWing

FanWing cross-section showing airflow

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 developed around 1997 by designer Patrick Peebles and is under development by his company FanWing Ltd. As of December 2024, 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. 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 aft of the fan, with the rear section shaped as a wedge-like fairing with sloping flat upper surface, that extends to the trailing edge.

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.

The flow sets up a trapped vortex within the rotor, which can rotate faster than the airspeed and greatly enhances both lift and thrust.[1]

Twisting the fan blades into a slight spiral, in a manner similar to a cylinder mower, helps to reduce rotor noise and make it inherently quieter in operation.[2]

Extending the length of the fixed trailing wedge section reduces drag.[2]

Gliding flight

When unpowered, the rotor will autorotate under forward motion and create lift as a glider. Adding a rounded leading edge improves performance when gliding in auto-rotation mode. However the glideslope is generally poor, at around 1:4.[2]

Aircraft configuration

Addition of an outboard tail recovers energy from the wing tip vortices to significantly increase overall efficiency. This in turn allows an even lower minimum forward speed.[3]

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.[4][5][6]

Limitations

Besides the added weight and complexity of the fan system, it has some limitations compared with a conventional fixed wing:

  • Glide ratio in case of power failure is low (about 1:4) if the rotors are allowed to auto-rotate.

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 Europe, conceived of it as a STOL 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.[7] Work began on a prototype drone, ostensibly aimed at the STOL urban surveillance market.[8][9] The benefits of adding a tail were discovered during continued development.[3] 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.[10]

As of December 2024, only unmanned development prototypes have flown.

See also

References

  1. ^ Du Siliang, Zhao Qijun and Wang Bo. "Research on Distributed Jet Blowing Wing Based on the Principle of Fan-Wing Vortex-Induced Lift and Thrust". International Journal of Aerospace Engineering,Volume 2019, Article ID 7561856. (pdf)
  2. ^ a b c George R Seyfang; "Recent Developments of the FanWing Aircraft", Proc. 3rd European Air & Space Conference (CEAS), 24.-28. Oct. 2011. (pdf).
  3. ^ a b Could FanWing go from LSA to heavy lifter?, Robert Coppinger, Aircraft Owners and Pilots Association, November 22, 2011. Accessed June 2012
  4. ^ "It looks like a lawnmower, was designed in a kitchen - but it could revolutionise aviation" Archived 2007-10-01 at the Wayback Machine The Independent, 11 November 2002
  5. ^ "2004 Year In Ideas: The FanWing" The New York Times Magazine, 12 December 2004
  6. ^ "More-powerful Fanwing set to fly"[dead link‍] Flight International Magazine, November 2004
  7. ^ "Innovate UK is an Executive non-departmental public body, sponsored by the Department for Business, Innovation & Skills". Innovate UK - the UK's innovation agency. GOV. UK. Archived from the original on 3 May 2016. Retrieved 3 May 2016.
  8. ^ FanWing UAV gets airborne after ground roll of only 1m Archived 2007-09-30 at the Wayback Machine Rob Coppinger, Flight International 01/05/07, Accessed August 2007.
  9. ^ FANWING - The Fixed-Wing Contender in the Rotorcraft Segment, Archived 2011-02-06 at the Wayback Machine Frost and Sullivan, 10 January 2011
  10. ^ Warwick, Graham. "Intermodal-container Air Cargo Concepts Attract Interest (Cargo Cult)" Aviation Week & Space Technology page 15, 25 August 2014. Accessed: 26 August 2014.
Wikimedia Commons has media related to FanWings.
  • FanWing Ltd company website
  • Image of research model with early tail configuration, FlightGlobal (Archived copy).
  • Siliang Du, Yi Zha and Qijun Zhao. "Research on Aerodynamic Test Validation and the Vector Force Control Method for an E-STOL Fan Wing Unmanned Aerial Vehicle". Aerospace, Vol 11, No 1. 2024. (online version, with download).
  • Patrick Peebles. "FanWing design notes." FanWing, 2024. (pdf. Retrieved January 2025).
  • "FanWing Demonstration Flight at ParcAberporth International UAV/S Event June 2008" (YouTube Video. Retrieved January 2025.)
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