NASA (Edwards, Calif., USA) reported on April 9 that its remotely piloted X-48C hybrid-wing-body subscale aircraft, which demonstrates technology concepts for cleaner and quieter commercial air travel, completed an eight-month flight research campaign on April 9.
The C model of the X-48 aircraft flew its first flight at Edwards Aug. 7 and its 30th flight brought the productive research project to a close.
"We have accomplished our goals of establishing a ground-to-flight database, and proving the low speed controllability of the concept throughout the flight envelope," says Fay Collier, manager of NASA's Environmentally Responsible Aviation project. "Very quiet and efficient, the hybrid wing body has shown promise for meeting all of NASA's environmental goals for future aircraft designs."
The scale-model aircraft, shaped like a manta ray, was designed by The Boeing Co. (Chicago, Ill., USA), built by Cranfield Aerospace Ltd. (Bedford, U.K.) and flown in partnership with NASA. The X-48C is a version of NASA's X-48B blended wing body aircraft modified to evaluate the low-speed stability and control of a low-noise version of a notional hybrid-wing-body design. This design features a flattened fuselage with no tail, and engines mounted on top of the fuselage at the rear of the plane. The design stems from concept studies for commercial aircraft that could be flying within 20 years. The studies are under way in NASA's Environmentally Responsible Aviation Project.
"Our team has done what we do best: flight-test a unique aircraft and repeatedly collect data that will be used to design future 'green' airliners," says Heather Maliska, X-48C project manager at NASA's Dryden Flight Research Center in California. "It is bittersweet to see the program come to an end, but we are proud of the safe and extremely successful joint Boeing and NASA flight test program that we have conducted."
The X-48C retained most dimensions of the B model, with a wingspan slightly longer than 20 ft/6.1m and a weight of about 500 lb/227 kg.
Primary changes to the X-48C model from the B model, which flew 92 flights at Dryden between 2007 and 2010, were geared to transforming it to an airframe noise-shielding configuration. External modifications included relocating the wingtip winglets inboard next to the engines, effectively turning them into twin tails. The rear deck of the aircraft was extended about 2 ft/0.6m. Finally, the project team replaced the X-48B's three 50-lb thrust jet engines with two 89-lb thrust engines. The aircraft had an estimated top speed of about 140 mph/225 kphg and a maximum altitude of 10,000 ft/3,048m.
"Working closely with NASA, we have been privileged throughout X-48 flight-testing to explore and validate what we believe is a significant breakthrough in the science of flight and this has been a tremendous success for Boeing," says Bob Liebeck, a Boeing senior technical fellow and the company's Blended Wing Body (BWB) Program manager. "We have shown a BWB aircraft, which offers the tremendous promise of significantly greater fuel efficiency and reduced noise,
can be controlled as effectively as a conventional tube-and-wing aircraft during takeoffs, landings and other low-speed segments of the flight regime."
"Our goal was to define the low-speed envelope and explore the low-speed handling qualities of the blended wing body class of tailless aircraft, and we have accomplished that," adds Mike Kisska, Boeing X-48 project manager.
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