25/06/2014 by Paul Fiddian - Armed Forces International's Lead Reporter

Boeing's Phantom Works division believes its entry into DARPA's VTOL X-Plane competition could shape the next generation of vertical takeoff and landing-capable aircraft designs.

In February 2013, DARPA (the US Defense Advanced Research Projects Agency) reached out to industry for future VTOL aircraft concepts. Its VTOL X-Plane search involves types with a high payload capacity that can reach and maintain high flight speeds but also hover very efficiently. "We are looking for true cross-pollinations of designs and technologies from the fixed-wing and rotary-wing worlds", DARPA's Ashish Bagai commented at the time.

Boeing's Phantom Swift concept is essentially an aircraft-helicopter hybrid of the type required. So far, Phantom Works has developed, built and test-flown a scaled-down technology testbed and, in March this year, the Phantom Swift officially joined the VTOL X-Plane programme as a competing design.

Boeing Phantom Swift

Boeing's Phantom Swift is equipped with a pair of large fans, fitted internally, which supply vertical lift. When the aircraft moves between vertical and forward flight, these fans stop supplying power and wingtip-placed fans take over. The same fans on the wingtips are used to enhance stability when the Phantom Swift is in hover mode.

Boeing says that, with this fan arrangement, the Phantom Swift is at least 50 per cent more efficient in the hover than a typical helicopter. It's expected to have a top speed of 740 kilometres per hour and, according to the US defence/aerospace firm, the Phantom Swift's configuration template could be replicated in other designs, ultimately creating a whole developmental series.

Phantom Swift: VTOL X-Plane

The full-sized Phantom Swift will have a wing span of 50 feet (15.2 metres) and a fuselage length of 44 feet (13.4 metres), weighing in at 12,000 lb (5,450 kilograms).

"The combination of body-fans and tilt-wing fans for improved controllability is the unique feature of the Phantom Swift", Boeing's Brian Ritter told media representatives today. "In the challenge of efficient hover and high-speed flight the answer is in ducted-fan technology, and this is something that Boeing is now investing heavily in."

Four competing designs are involved in the DARPA VTOL X-Plane competition, which is currently in its Phase 1 stage. Phase 3, the final stage, will see the winning design selected.