FanWing
A cross-flow fan rotor wing providing lift and thrust.
The FanWing is an aircraft design that combines a horizontal-axis cross-flow fan with a fixed wing. The fan pushes air across the fixed surface, generating both lift and forward thrust. This allows the aircraft to create useful lift at slower forward speeds than a traditional wing would permit.
In operation, the cross-flow fan sits above the leading edge of the wing and runs the full span. The wing’s upper surface is shaped around the fan to form a half-duct, while the rear section of the wing extends aft as a wedge-like fairing with a sloping flat top. When the fan spins—with the upper edge moving backward and the lower edge forward—the half-duct directs a net backward flow of air, producing forward thrust. This airflow over the upper surface also creates a circulation around the rotor-wing combination, generating vertical lift. A trapped vortex forms inside the rotor, which can spin faster than the aircraft’s airspeed, boosting both lift and thrust. Twisting the fan blades into a slight spiral, similar to a cylinder mower, reduces noise. Lengthening the trailing wedge section lowers drag.
When unpowered, the rotor autorotates in forward motion, allowing the FanWing to glide. Adding a rounded leading edge improves gliding performance in autorotation mode, but the glide ratio is poor—roughly 1:4.
An outboard tail can recover energy from wing tip vortices, significantly increasing overall efficiency and allowing an even lower minimum forward speed.
The design has limitations. Besides the added weight and complexity of the fan system, the glide ratio during a power failure is low (about 1:4) if the rotors autorotate.
The concept was first developed around 1997 by designer Patrick Peebles, an American based in Europe, who saw it as a STOL device. He later founded FanWing Ltd. Wind tunnel tests and powered model flights received UK government funding, including SMART grant awards in 2002 and 2003. Work began on a prototype drone for the STOL urban surveillance market. The benefits of adding a tail emerged during continued development. By 2014, EU sources, including €783,000 through the German Aerospace Center, supported wind tunnel tests of a 1.5-meter wing section. As of December 2024, only unmanned development prototypes have flown.
- Concept developed
- 1997
- Designer
- Patrick Peebles
- Company
- FanWing Ltd
- Glide ratio unpowered
- 1:4
- Eu funding 2014
- €783,000 through the German Aerospace Center
- Status as of december 2024
- Only experimental drones have flown
Lore & Background
The concept was initially developed around 1997 by designer Patrick Peebles and is under development by his company FanWing Ltd. 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 aimed at the STOL urban surveillance market. By 2014, support for wind tunnel tests of a 1.5 meter wing section was provided through EU sources including €783,000 through the German Aerospace Center. As of December 2024, only unmanned development prototypes have flown.
The fan is set above the leading section of a fixed wing and extends the full span. The wing upper surface is shaped around the fan to form a half-duct. When the fan spins with the upper edge moving backwards and the lower edge forwards, the fixed half-duct creates 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. A trapped vortex within the rotor can rotate faster than the airspeed and greatly enhances both lift and thrust. Twisting the fan blades into a slight spiral helps reduce rotor noise. Extending the length of the fixed trailing wedge section reduces drag.
When unpowered, the rotor will autorotate under forward motion and create lift as a glider, though the glideslope is generally poor at around 1:4. Adding a rounded leading edge improves performance when gliding in auto-rotation mode. Addition of an outboard tail recovers energy from wing tip vortices to significantly increase overall efficiency, allowing an even lower minimum forward speed.
Reader's Guide
The FanWing represents a novel approach to combining lift and thrust in a single rotor-wing system, distinct from conventional fixed wings or rotary wings. Its significance lies in its ability to generate useful lift at forward speeds lower than the stalling speed of a conventional wing, achieved by the radial fan increasing airflow velocity over the wing's upper surface independently of forward motion. This makes it a candidate for short takeoff and landing (STOL) applications, as initially conceived by Patrick Peebles. The concept has received incremental development support from UK government SMART grants and EU funding, including wind tunnel tests of a 1.5 meter wing section. However, as of December 2024, only experimental drones have flown, indicating the technology remains in a developmental stage. Its legacy is that of an unconventional design that has been studied and tested but not yet matured into a manned or production aircraft. The low glide ratio of about 1:4 in case of power failure, along with added weight and complexity, are noted limitations compared with conventional fixed wings.
Did You Know?
- The FanWing uses a cross-flow fan that sets up a trapped vortex within the rotor, which can rotate faster than the airspeed.
- When unpowered, the FanWing can autorotate as a glider, but its glide ratio is poor at about 1:4.
- As of December 2024, only unmanned development prototypes of the FanWing have flown.
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