luni, 26 mai 2008


NASA's Dryden Flight Research Center and Boeing have expanded flight testing for the X-48B blended wing body (BWB) research aircraft into the second of six planned phases.

The second phase of flight tests with the 500-pound, remotely piloted test vehicle involves higher speed regimes. The 21-foot-wingspan test aircraft is flying without its slats deployed. Slats are flight control surfaces on the leading edges of wings which, when extended, allow an aircraft to take off, fly and land at slower speeds.

X-48B flight testing is taking place at NASA's Dryden Flight Research Center on Edwards Air Force Base, Calif. NASA Dryden is providing critical support to a Boeing-led project team that also includes the U.S. Air Force Research Laboratory in Dayton, Ohio, and Cranfield Aerospace Ltd., of Bedford, England.

“The first flight in the slats-retracted configuration marked another milestone in aviation history and the performance of the X-48 aircraft continues to exceed our expectations,” said Tim Risch, X-48B project manager for NASA.

“We want to fully understand the aerodynamics of the blended wing body design all the way up to and beyond stall, so that we can learn how to fly a blended wing body aircraft as safely as any other large transport aircraft with a conventional tail,” said Norm Princen, Boeing's X-48B chief engineer. “This latest phase of the flight testing is one more step in the process and we are looking forward to progressing on to more risky flight maneuvers in the months ahead.”

Initial X-48B flight tests, known as the Block 1 phase, consisted of 11 flights and incorporated slow-speed testing with bolt-on leading-edge slats in the extended position. Block 2 flights began on April 4. The X-48B made its first flight on July 20, 2007.

BWB test aircraft dubbed 'Skyray'

Dubbed 'Skyray' by the partners, the sub-scale BWB aircraft now sports a clean leading edge and takes off and lands at speeds of about 75 knots, compared with 60 knots in the Block 1 flight tests. In Block 2 flight tests, NASA Dryden and Boeing will gather data from the aircraft at speeds up to 118 knots.

At least eight flights are scheduled for the Block 2 phase. In all, the project calls for a total of six flight-test phases, each progressively increasing the level of flight-envelope risk. The final phase, Block 6, is designed to push the aircraft's flight parameters by testing the departure limiter, a critical part of the flight control software that is designed as a safety feature to prevent the aircraft from going into uncontrolled flight.

NASA's participation in the blended wing body research effort is focused on advanced flight dynamics and structural design concepts within the Subsonic Fixed Wing Project. This project is part of the Fundamental Aeronautics Program managed by NASA's Aeronautics Research Mission Directorate.

BWB design's potential benefits

Potential benefits of the blended wing body design include increased volume and thus greater carrying capacity, efficient aerodynamics for reduced fuel burn and, possibly, significant noise reductions allowed by propulsion integration. In initial flight testing, NASA's and Boeing's principal focus is to validate research on the aerodynamics and controllability of the shape, including comparisons of flight data with the extensive database of aerodynamic data collected in wind-tunnel tests.

In addition to hosting the X-48B flight-test and research activities, NASA Dryden provides engineering and technical expertise garnered from years of operating cutting-edge aircraft. Dryden assists with the hardware and software validation and verification process, the integration and testing of the aircraft's systems and the pilot's ground control station. Its range group provides critical telemetry and command and control communications during X-48B flights, while Dryden Flight Operations provides a chase aircraft and flight scheduling. Photo and video support complement the effort.

Members of the Boeing Phantom Works research and technology organization, based in Huntington Beach, Calif., designed the X-48B flight test aircraft in cooperation with NASA and the U.S. Air Force Research Laboratory to gather detailed information about the stability and flight-control characteristics of the blended wing body design, especially during takeoffs and landings.

Three small jet engines enable the composite-skinned, 8.5-percent-scale vehicle to fly up to an altitude of 10,000 feet. A pilot flies the aircraft remotely from a ground control station, using conventional aircraft controls and instrumentation while viewing a monitor fed by a forward-looking camera on the aircraft.

Two X-48B research vehicles were built by Cranfield Aerospace Ltd. Ship 1, a duplicate of the Ship 2 flight test aircraft, completed extensive wind tunnel testing in 2006 in the full-scale wind tunnel at the NASA Langley Research Center in Hampton, Va. Ship 1 remains available for use as a back-up aircraft during the flight test program.

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