The latest X-plane, an 8.5% scaled model of a blended wing body or BWB heavy lift jet the width of an A380, has made its maiden flight at the Edwards Air Force Base in California.
The experimental X-48C is a significant advance on the research program flown by the X-48B in 2007, and Boeing could even be said to be understating the potential of this type of aircraft in its announcement, as the BWB concept has for decades been seen as a long term solution to the needs for very quiet, ultra fuel efficient heavy lift missions, but not passenger flights, as explained later in this report.
There is at this hour a paucity of high quality images of the X-48C’s first flight, but there is a fine but low resolution video compilation at this link, with an image capture shown below.
This is part of a Boeing statement issued after the flight.
Engineers from Boeing Research & Technology, the company’s central research, technology and innovation organization, will be working closely with NASA engineers during flight tests of the X-48C, which are expected to continue throughout 2012. As handling qualities of the X-48C will be different than those of the X-48B, the project team developed flight control software modifications, including flight control limiters to keep the airplane flying within a safe flight envelope.
With a 21-foot wingspan, the 500-pound aircraft is an 8.5 percent scale model of a heavy-lift, subsonic airplane with a 240-foot wingspan that possibly could be developed in the next 15 to 20 years for military applications such as aerial refueling and cargo missions. The X-48C has an estimated top speed of about 140 miles per hour, with a maximum altitude of 10,000 feet. The X-48C project team consists of Boeing, NASA, Cranfield Aeropace, and the U.S. Air Force Research Laboratory.
Boeing and NASA’s Aeronautics Research Mission Directorate are funding X-48 technology demonstration research. The effort supports NASA’s Environmentally Responsible Aviation project, which has goals to reduce fuel burn, emissions and noise of future aircraft.
The lack of reference to passenger carrying capability relates to the awkward reality of exaggerated angular momentum that would be experienced by anyone seated away from the axis of the direction of flight of the aircraft.
Small changes in direction would be magnified into much larger movements the further a passenger is seated away from this axis, corresponding to the location of the fuselage in all airliners ever to enter into service, generating roller coaster effects, including the sometimes revolting consequences of vomit spreading backwards or sideways rather than escaping forwards.
The forces that swing you a few centimes from side to side in a banking 737, with no discomfort whatsoever, would also make you describe an arc of several metres with rapid acceleration and deceleration the further you were seated away the centre of a BWB.
This would not be a problem for suitably restrained inanimate cargo containers, especially within an unpressurized structure since the tendency of pressurised containers to stress their walls by trying to ovalise is another constraint on BWB designs.
Which is a pity in the sense that BWB geometry is incredibly space efficient on the ground as well as lending itself to a variety of monocoque construction techniques in which all of the aerodynamic and most of the traditional internal structural loadings would be taken by the blended outer skin.
All of which has been thoroughly and painstakingly researched by Boeing, which has persevered with co-funded research into BWB craft for a very long time.
A BWB shared by passengers seated in a central section corresponding to the fuselage of a ‘normal’ airliner and cargo stored in the outer reaches of the structure has been considered in some technical analysis.
The X-48C may thus prove to be an important step on the way to such a future.
Below is a Boeing wallpaper of the X-48B, also shot at Edwards but looking more like the surface of Mars, showing the original three engine layout which is the immediately obvious physical difference from the latest X-48C version.