The FanWing is an aircraft configuration 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 2018, only experimental drones have been flown.
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.
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 recovers energy from the wing tip vortices to significantly increase overall efficiency. This in turn allows an even lower minimum forward speed. [1]
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. [2] [3] [4]
Besides the added weight and complexity of the fan system, it has some limitations compared with a conventional fixed wing:
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 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. [6] Work began on a prototype drone, ostensibly aimed at the STOL urban surveillance market. [7] [8] The benefits of adding a tail were discovered during continued development. [1] 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. [9]
As of December 2018, only unmanned development prototypes have flown.
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.
A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-wing aircraft and other hybrid aircraft with powered rotors such as cyclogyros/cyclocopters and gyrodynes.
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 expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift.
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller. When used in vertical takeoff and landing (VTOL) applications it is also known as a shrouded rotor.
Aircraft flight mechanics are relevant to fixed wing and rotary wing (helicopters) aircraft. An aeroplane, is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
A helicopter pilot manipulates the helicopter flight controls to achieve and maintain controlled aerodynamic flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a deliberate way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift (force) at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.
The Avro Canada VZ-9 Avrocar was a VTOL aircraft developed by Avro Canada as part of a secret U.S. military project carried out in the early years of the Cold War. The Avrocar intended to exploit the Coandă effect to provide lift and thrust from a single "turborotor" blowing exhaust out of the rim of the disk-shaped aircraft. In the air, it would have resembled a flying saucer.
The Ryan XV-5 Vertifan was a jet-powered V/STOL experimental aircraft in the 1960s. The United States Army commissioned the Ryan VZ-11-RY in 1961, along with the Lockheed VZ-10 Hummingbird. It successfully proved the concept of ducted lift fans, but the project was cancelled after multiple fatal crashes unrelated to the lift system.
On a helicopter, the main rotor or rotor system is the combination of several rotary wings with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight. Each main rotor is mounted on a vertical mast over the top of the helicopter, as opposed to a helicopter tail rotor, which connects through a combination of drive shaft(s) and gearboxes along the tail boom. The blade pitch is typically controlled by the pilot using the helicopter flight controls. Helicopters are one example of rotary-wing aircraft (rotorcraft). The name is derived from the Greek words helix, helik-, meaning spiral; and pteron meaning 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 International Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".
A convertiplane is defined by the Fédération Aéronautique Internationale as an aircraft which uses rotor power for vertical takeoff and landing (VTOL) and converts to fixed-wing lift in normal flight. In the US it is further classified as a sub-type of powered lift. In popular usage it sometimes includes any aircraft that converts in flight to change its method of obtaining lift.
An aircraft propeller, also called an airscrew, converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.
A powered lift aircraft takes off and lands vertically under engine power but uses a fixed wing for horizontal flight. Like helicopters, these aircraft do not need a long runway to take off and land, but they have a speed and performance similar to standard fixed-wing aircraft in combat or other situations.
Autorotation is a state of flight in which the main rotor system of a helicopter or other rotary-wing aircraft turns by the action of air moving up through the rotor, as with an autogyro, rather than engine power driving the rotor. The term autorotation dates to a period of early helicopter development between 1915 and 1920, and refers to the rotors turning without the engine. It is analogous to the gliding flight of a fixed-wing aircraft. Autorotation has also evolved to be used by certain trees as a means of disseminating their seeds further.
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 and hovering performance like a helicopter, while potentially benefiting from some of the advantages of a fixed-wing aircraft.
In aeronautics, Distributed propulsion is an arrangement in which the propulsive and related air flows are distributed over the aerodynamic surfaces of an aircraft. The purpose is to improve the craft's aerodynamic, propulsive and/or structural efficiency over an equivalent conventional design.
A rotor wing is a lifting rotor or wing 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 has become widespread on rotorcraft such as the helicopter.