UK-based GFS Projects has unveiled initial concepts for man-carrying and unmanned cargo-carrying coanda-effect aircraft, the latter with disc spans reaching up to 30m (100ft).

The initial man-carrying version would be a scout craft with a crew of one to two. It would be capable of dash speeds of 100-150kt (185-277km/h), but also be able to stop in flight to hover above areas of interest.

Scout configurations include a single-seat arrangement with four thrusters integrated into the lower air vehicle disc airframe and a V-tail, and twin seat craft with single tail.

The cargo version would use a large detachable pod suspended beneath the airframe disc. A lead application could be the deployment of mobile medical facilities, says GFS founder and managing director Geoff Hatton.

An adapted configuration could operate as a medical evacuation system: “It would have to be a 30m craft or of that order,” he says.

The company is to lead its shift from research craft to commercially ready vehicles over the next two years through the development of a 1.2m-disc UAV optimised for the civil market.

An internal combustion engine-powered prototype is in preparation and is set to fly in the second half of this year, says Hatton.

The new-generation craft will incorporate forward thrusters, a leading-edge canopy structure, and a tail.

The company has already built and flown one electric-powered demonstrator with dual ducted fan thrusters mounted within the disc.

A second demonstrator with twin suspended ducted fans, each generating 1lb thrust, is currently being rig tested to measure the combined effects of the design modifications in improving flight performance against headwinds.

Coanda scoutcraft

GFS single seat coanda-effect scoutcraft concept

The rig-mounted demonstrator has achieved stable forward flight against headwinds of 15.6kt (29km/h), says Hatton.

 Demonstrations carried out for Flight International on 1 May saw the air vehicle achieve forward flight against winds of 12-13kt.

The canopy structure on the leading edge is designed to reduce drag in forward flight by reducing the effect of wind vortices.

It also has the effect of shifting the downwards airflow over the air vehicle disc from being equal over all surfaces to provide a nullified zone at the front of the craft.

This in turn means the even air pressure on all remaining sides of the disc translates into forward motion in zero to light wind conditions.

Hatton says he is also experimenting with re-introducing airflow between the disc and the canopy to allow for manoeuvre benefits of the original coanda design to be recaptured, particularly in hover modes.

However, he also says that the firm’s research has shown that coanda lift can be sustained even with significant changes to the overall air vehicle design.

The introduction of the tail structure is intended to provide a weathercock effect for combating sudden wind shifts. Hatton says the addition is expected to be particularly important for small UAV versions operated by military and paramilitary forces in urban environments.

Wind has been a major obstacle to coanda-aircraft development, limiting most experiments to indoor flight.

Hatton says the combined features “do overcome the wind problem. But more importantly with the thrusters we do not have to pitch over for forward flight as does a helicopter”.

The existing wind test rig demonstrator will be fitted with alternate thrusters, each generating 2.2lb, as part of current research. It will also be used to explore optimal tail configurations.

The test rig is an open frame environment with a commercial blower unit at one end and a twin rail arrangement supporting a moveable dolly.

The UAV demonstrator is mounted above the dolly on one of three different pylons that allow the aircraft to remain fixed, rotate in a horizontal plane, or move both horizontally and vertically to test various motion characteristics.

Hatton says that the configuration changes have opened up the potential for either the reduction in size or removal of flap and movable vane control surfaces as used on existing demonstrators.

This is expected to result in a more streamlined airframe.

Development of a commercially ready UAV version will be an important stepping stone in transition of the technology from research and experimentation activities towards market readiness, says GFS marketing and business development director David Steel.

Near-term applications being assessed by the firm include agricultural support and civil authority support.

Large cargo-carrying versions would have particular application in environments where the human population lacks establishment infrastructure, says Steel.

This could make the air vehicle type particularly appropriate to countries such as Africa, he argues.

The internal combustion engine-powered prototype will have a payload capacity of around 6kg (13lb), says Hatton.

Flight endurance is estimated at between 30min and 1h.

The air vehicle will be the first internal combustion engine powered craft flown by GFS, with all 30-plus experimental craft built to date being electrically powered.

The company is continuing to work on mini air vehicle designs with a variety of demonstrators being progressively developed to explore more sophisticated indoor flight requirements.

A commercial product optimised for the inspection of large indoor roof areas could be one such application, says Steel.

A civil authority version could fly through underground railway tunnels or mines as part of an emergency response operation, Hatton says.

“Imagine flying one of these down the underground after the 7 July [2005 terrorist] bombings [in London] to find out what was going on.”

The coanda design has a high degree of resilience to impacts against structures, says Hatton, meaning a UAV could be remotely flown considerable distances in completely unknown environments.

GFS plan to mount pilots-view cameras on an existing demonstrator in short weeks to begin to explore the implications of this change in perspective for the operator and the requirements for an operational craft.

That research will also flow into studies GFS is conducting for the US Defence Advanced Research Projects Agency under a contract placed earlier this year to examine indoor flight characteristics of coanda-configuration craft.

That study is due to be completed in the third quarter of this year, with the deliverables comprising data rather than air vehicles, says Hatton.

The indoor designs are also unlikely to see a shift toward a more highly autonomous configuration for the smaller craft as the company works towards market-ready products.

Hatton says the primary interest of potential operators is in an air vehicle that can respond rapidly and in real time to unknown environmental challenges while providing data.

A fully autonomous system capable of performing that same task is unlikely to be able to provide the reaction speeds, he argues.

In contrast, the 1.2m internal combustion-powered prototype will incorporate a waypoint-based navigation system. GFS is working with autopilots sourced from the UK-based Blue Bear Systems Research.

Development of the air vehicle concepts over the past six years has cost £0.5 million ($1 million), including a UK government business research grant of £43,500 in 2002-3.

Hatton says the company’s main challenge is now to successfully make the transition from research and development into full-scale production readiness, including securing of funding.

The class of air vehicles also needs to be better understood to allow for its market acceptance. He says “this is not just a flying saucer. This is a sixth and new way of flying.”