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30 Oct 06. In cooperation with NASA and the U.S. Air Force Research Laboratory, Boeing Phantom Works soon will begin ground testing of its X-48B Blended Wing Body (BWB) concept in preparation for flight testing early next year. The X-48B ground and flight testing will take place at NASA’s Dryden Flight Research Center at Edwards Air Force Base in California, where two high-fidelity 21-foot wingspan prototypes have been delivered. The prototypes were produced to explore and validate the structural, aerodynamic and operational advantages of the BWB concept. They were designated the “X-48B” by the U.S. Air Force based on its interest in the design’s potential as a future military aircraft. X-48B Ship 1 completed extensive wind tunnel testing at the Old Dominion University NASA Langley Full-Scale Tunnel this summer before being shipped to NASA Dryden as a backup to Ship 2, which will be used for flight testing early next year. In preparation for first flight, the X-48B Ship 2 will undergo ground testing to validate its engine- and fuel-system integrity, battery endurance, telemetry link communication, flight-control software, and low- and high-speed taxiing characteristics.
06 Nov 06. The cause of green aviation will receive a boost when researchers from Cambridge. University and the Massachusetts Institute of Technology unveil their futuristic design for a “silent aircraft” that is also ultra-fuel efficient. The noise that people would hear on the ground has been cut by a factor of 3,000, says Ann Dowling, who headed the Cambridge team – so the aircraft would hardly be audible abovenormal background noise outside the airport perimeter. It would consume 25 per cent less fuel than today’s most efficient airliners. The Cambridge MIT Institute (CMI) has worked for three years with Boeing, Rolls-Royce, Nasa and other aerospace organisations on its Silent Aircraft Initiative, with total funding of more than £4m including industrial contributions. The 40 engineers and scientists on the project released a preliminary design last year but it has changed substantially ahead of its presentation to the Royal Aeronautical Society in London today. The overall shape is a tail-less flying wing or “blended wing body”, so that the whole structure provides lift. This enables it to make a slower, steeper and therefore quieter approach to landing than a traditional “tube and wings” aircraft. Conventional flaps and slats, which are usually a noise source, have been eliminated. Three novel engines are mounted on the top of the aircraft, to screen noise from the ground. Unlike today’s engines, they have variable-size jet nozzles to allow slow jet propulsion for low noise during take-off and climb – and then higher jet speeds optimised for maximum efficiency during cruise. When the project started the emphasis was on silence, with fuel efficiency very
much a secondary objective. But, as the global warming debate has heated up over the past three years, the public has been much more aware of commercial aviation as a fast-growing source of carbon emissions. So the CMI design team has paid more attention to reducing fuel consumption than it originally expected. “On the whole, fortunately, fuel economy and quietness have gone together well,” says Tom Hynes, head of engine design for the project. “We thought at the beginning that there would be more trade-offs between them than has actually been the case. But if we were to design this aircraft purely for fuel economy there would be some differences.” The passenger experience in a flying wing aircraft with a wide delta-shaped cabin would be very different to that in a conventional cigar-shaped body. For a start, there might be no real windows. Instead, “virtual windows” might be displayed around the cabin. But the design team has done no detailed work on internal design. The main project is winding down but Prof Dowling says