Now, Irish inventor Pat Peebles has developed a working prototype for such a vehicle, which he claims is quiet, light, slow (33mph) and stable enough to make it ideal for a number of civilian and military applications.
Peebles’ FanWing has a cross-flow fan at the leading edge that pulls air in at the front and accelerates it over the trailing edge of the wing. By transferring the work of the engine to the rotor which spans the whole wing, a high lift-efficiency is achieved .
A small flap at the leading edge controls the thrust and lift of the wing. By increasing the thrust & lift on one wing and reducing it on the other the FanWing will go into a perfect turn with no yaw.
Two flying models have been made and successful wind tunnel tests at the University of Rome and Imperial College have indicated that 100Hp will be sufficient to lift 1.5 tons of weight. Peebles claims that this efficiency will improve as size increases and blade/wing shape are enhanced.
In flight, Fanwing will be quiet and stable because it’s not sensitive to the angle of the incoming air. Each wing will have two sections of rotor with a bearing halfway along, and vibration is not expected to be a problem with the rotor turning at less than 1000 Rpm.
Tests have also indicated that the wing will cope very well with turbulence. This is because it is not very sensitive to changes in the angle of attack. To illustrate, a traditional airfoil can double the lift with only a couple of degrees of change. The FanWing needs almost ten times that amount to double the lift. Thus, if a FanWing flies into a rising current of air, the bump that you would feel in a traditional aeroplane will not happen.
Because the axis of the FanWing’s rotor is parallel to the spanwise axis of the aircraft, it is easily combined with a very deep (hence stiff and light) and continuous wing structure without aerodynamic or propulsive penalty.
Peebles and his team are currently trying to ensure that the plane will glide with the engines off. If the motor goes off it will have to be disconnected from the rotor and the tail plane lifted to maintain a high angle of attack. This will get the rotor up to speed. The Glide angle is expected to be very steep.
While a lot of progress has been made on a limited budget, there is still a long way to go. Peebles wants to build a large wing that will be tested on a boom. This will be used to test for stress failures, simulate bird strikes and gauge behaviour in other difficult situations.
The safety systems of the plane also need work. As Fanwing does not glide well, work must be done on the airfoil to enhance the autorotation. Peebles is also interested in ballistic parachutes and the ability of the plane to fly on just one engine.
While there are no solid contracts for development, La Mouette, a French manufacturer of ultralights and hang gliders, is interested in participating in an EU funded project.
Obvious applications for the technology will be in unmanned surveillance, short-haul freight, fire-fighting, crop-dusting, rescue operations, and taxi flights. Researchers also see an interesting area for development in Wing In Ground effect (WIG) vehicles.
While development is stunted by lack of funding, Peebles remains optimistic and, if the funds can be found, anticipates manufacturing the first ultralight craft in around 2 years time