|The blended wing X-48B on the ground.|
A prototype blended wing body (BWB) research aircraft—the X-48B—developed by Boeing, NASA’s Fundamental Aeronautics Program, and the Air Force Research Laboratory at Wright Patterson Air Force Base, recently made its first flight.
The Boeing BWB design resembles a flying wing, but differs in that the wing blends smoothly into a wide, flat, tailless fuselage. This fuselage blending helps to get additional lift with less drag compared to a circular fuselage.
This translates to reduced fuel use at cruise conditions. A study by Boeing (Liebeck, 2004) concluded that an 800-passenger BWB aircraft sized for a 7000-n mile range could deliver a 27% reduction in fuel burn per seat mile compared to a conventional design with comparable specs.
Also, because the engines mount high on the back of the aircraft, there is less noise inside and on the ground when it is in flight.
|The X-48B in the air.|
Three 50lb each thrust JetCat P200 turbojet engines enable the composite-skinned, 8.5% scale research vehicle to fly up to 10,000 feet and 120 knots in its low-speed configuration. Modifications would need to be made to the vehicle to enable it to fly at higher speeds.
The unmanned aircraft is remotely piloted from a ground control station in which the pilot uses conventional aircraft controls and instrumentation while looking at a monitor fed by a forward-looking camera on the aircraft.
The 21-foot wingspan, 500-pound, remotely piloted X-48B test vehicle took off for the first time on 20 July and climbed to an altitude of 7,500 feet before landing 31 minutes later.
The X-48B flight test vehicle was developed by Boeing Phantom Works in cooperation with NASA and the US Air Force Research Laboratory to gather detailed information about the stability and flight-control characteristics of the BWB design, especially during takeoffs and landings. The two X-48B research vehicles were built by Cranfield Aerospace Ltd., in the United Kingdom, in accordance with Boeing requirements.
Up to 25 flights are planned to gather data in these low-speed flight regimes. Following completion of low-speed flight testing, the X-48B likely will be used to test the BWB’s low-noise characteristics, as well as BWB handling characteristics at transonic speeds.
Two X-48B research vehicles have been built. The vehicle that flew on 20 July is Ship 2, which also was used for ground and taxi testing. Ship 1, a duplicate of Ship 2, completed extensive wind tunnel testing in 2006 at the Old Dominion University NASA Langley Full-Scale Tunnel in Virginia. Ship 1 will be available for use as a backup during the flight test program.
NASA’s Subsonic Fixed Wing Project team under the Fundamental Aeronautics Program has long supported the development of the blended wing body concept. It has participated in numerous collaborations with Boeing, as well as several wind tunnel tests for different speed regimes. The team is focused on researching the low-speed characteristics of the design and expanding its flight envelope beyond the limits of current capabilities.
NASA is interested in the potential benefits of the aircraft: increased volume for carrying capacity, efficient aerodynamics for reduced fuel burn, and, possibly, significant reductions in noise due to propulsion integration options. In these initial flights, the principal focus is to validate prior research on the aerodynamic performance and controllability of the shape, including comparisons of the flight data with the extensive wind-tunnel database.
Contingent upon further testing and program funding, a military cargo version of the BWB could be operational in the 2015-2020 timeframe, according to Boeing.
Boeing Advanced Systems (2007 Paris Air Show presentation)
R. H. Liebeck, “Design of the Blended Wing Body Subsonic Transport”, Journal of Aircraft, Vol. 41, No. 1, January.February 2004