Blended wing body design shows environmental promise as NASA completes flight testing of Boeing prototype
The Boeing X-48C subscale prototype (photo: NASA)
Tue 16 Apr 2013 – NASA has concluded an eight-month programme of 30 test flights using Boeing’s X-48C subscale prototype. The ‘C’ version of the aircraft was specifically intended to assess the low-speed performance and stability of a noise-reducing configuration of the Blended Wing Body (BWB) design. The BWB concept has been developed by Boeing in support of NASA’s Environmentally Responsible Aviation (ERA) programme, which aims to progress technologies that will contribute to cleaner and quieter commercial aircraft in the future. During the test flights, the remote controlled X-48C, which weighs 500 pounds (227kg) and has a wingspan of about 20ft (6m), flew at speeds of up to 140mph (225kph) and altitudes reaching 10,000 feet (3048m).
The particular focus of this phase of the research using the X-48 required some changes to be made from the ‘B’ version, which had previously carried out 92 flights between 2007 and 2010. “Our goal was to define the low-speed envelope and explore the low-speed handling qualities of the BWB class of tail-less aircraft,” explained Mike Kisska, Boeing X-48 Project Manager, about the aims of the ‘C’ version.
As a result, the X-48C airframe displays a number of noticeable differences to its earlier counterpart. The ‘B’ version’s winglets were moved inboard, effectively becoming twin tails and the rear deck of the aircraft was extended by about 2 feet (0.6m). Additionally, the three 50 pound (23kg) thrust jet engines from the ‘B’ version were replaced with two more powerful 89 pound (40kg) thrust jet engines on the X-48C.
These modifications were accompanied by changes to the flight control systems software, including the addition of flight control limiters that kept the aircraft flying in a safe flight envelope.
The NASA-Boeing project team believes the data from the test flights, which have been running since August 2012 and typically lasting 30 minutes each, will contribute significantly towards the stated goals of the ERA project. These are to develop technologies that reduce fuel burn and harmful emissions from aviation by 50% and that shrink the geographical areas affected by objectionable airport noise by 83%.
“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,” said Fay Collier, NASA’s ERA Project Manager. “Both very quiet and efficient, the hybrid wing body has shown promise for meeting all of NASA's environmental goals for future aircraft designs.”
Bob Libeck, Boeing’s BWB Program Manager, was equally positive about the outcomes of the X-48 tests. “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,” he said.
The X-48 research was jointly funded by NASA and Boeing and the flight testing was performed at NASA’s Dryden Flight Research Centre, based at Edwards Air Force Base, California. The subscale aircraft was built by Cranfield Aerospace in the UK.