Blended Wing Body, or BWB, designates an alternative airframe design which incorporates design features from both a futuristic fuselage and flying wing design. The purported advantages (see Potential advantages below) of the BWB approach are efficient high-lift wings and a wide airfoil-shaped body. This enables the entire craft to contribute to lift generation with the result of potentially increased fuel economy.
Flying wing designs are defined as having two separate bodies and only a single wing, though there may be structures protruding from the wing. Blended wing/body aircraft have a flattened and airfoil shaped body, which produces most of the lift to keep itself aloft, and distinct and separate wing structures, though the wings are smoothly blended in with the body.
An early aircraft exhibiting BWB design principles was the Stout Batwing. The designer William Bushnell Stout, toured the country promoting aircraft of the future would not have fuselages.
The Junkers G.38, flew in 1929. This "super jumbo" airliner of its day, seated thirty-four passengers, six in each of its two meter thick wings, and the balance in the central fuselage. In comparison, a contemporary passenger aircraft, the Ford Trimotor, carried a total of nine passengers in its more traditional wing and box fuselage design. Another example of similar design is Burnelli CBY-3. It had an airfoil shaped fuselage, producing significant part of the total lift. The CBY-3 had however a fairly conventional twin-boom empennage for added stability.
The Miles M.30 "X Minor" of the early 1940s was an experimental aircraft for research blended wing fuselage designs for an envisaged large airliner. Germany was designing blended wing body jet bombers at the very end of World War II.
In some ways, the B-2 Spirit stealth bomber is a design which falls between classic flying wing concepts and the BWB concept. It is usually classified as a flying wing, however, as the protruding body sections are not much larger than the underlying wing shape structure.
Currently, both NASA and Boeing are exploring BWB designs under the designation X-48. Studies suggest that BWB aircraft, configured for passenger flight, could carry from 450 to 800 passengers and achieve fuel savings of over 20 percent. NASA has been developing, since 2000, a remotely controlled model with a 21 ft (6.4 m) wingspan. This research is focused on establishing the base data concerning the lift, stall and spin characteristics inherent in a Blended Wing Body design.
Boeing Phantom Works is developing the blended wing body aircraft concept in cooperation with the NASA Langley Research Center. In a continuing effort to study the flight characteristics of the BWB design, a remote-controlled propeller-driven blended wing body model with a 17 ft (5.2 m) wingspan was successfully flown in 1997. The next step was to fly the 35 ft (10.7 m) wide X-48A in 2004, but that program was later canceled.
Boeing Phantom Works is focusing current research on a pair of models, called the X-48B, which were built under contract by Cranfield Aerospace in the United Kingdom. Norman Princen, Boeing's chief engineer for the project, said, "Earlier wind-tunnel testing and the upcoming flight testing are focused on learning more about the BWB's low-speed flight-control characteristics, especially during takeoffs and landings. Knowing how accurately our models predict these characteristics is an important step in the further development of this concept."
The X-48B has a 21-foot (6.4 m) wingspan, weighs 392-pound (178 kg), and is built from composite materials. It is powered by three small turbojet engines and is expected to fly at up to 120 kn (220 km/h) and reach an altitude of 10,000 feet (3,000 m). The X-48B is a scaled down from a conceptual 240-foot wide design. Though passenger versions of the X-48B have been proposed, the design will more likely be first used for a military transport.
Wind tunnel testing on a 12 ft wide blended wing body model was completed in September 2005. NASA performed wind tunnel tests on X-48B Ship 1, an 8.5% scale model, at a facility shared by Langley and Old Dominion University during April and May 2006. After the wind tunnel testing, the vehicle was shipped to NASA's Dryden Flight Research Center at Edwards Air Force Base to serve as a backup to X-48B Ship 2 for flight testing. Ground testing at Dryden began in November 2006, to validate the aircraft's systems integrity, telemetry and communications links, flight-control software and taxi and takeoff characteristics.
The X-48B first flew on July 20, 2007. The BWB reached an altitude of 7,500 feet (2,286 m) above MSL and lasted 31 minutes. This began flight testing. The remotely-piloted aircraft was successfully stalled for the first time on September 4, 2008, with fixed leading edge slats, a forward center of gravity, and 23-degree angle of attack (2° beyond the maximum coefficient of lift). Stall testing was repeated on 11 September with a NASA pilot at the console.
NASA and Boeing successfully completed initial flight testing of the Boeing X-48B on March 19, 2010. Fay Collier, manager of the ERA Project in NASA's Aeronautics Research Mission Directorate commented on the completion of the first phase of testing saying, "This project is a huge success. Bottom line: the team has proven the ability to fly tailless aircraft to the edge of the low-speed envelope safely."
Following the installation of a new flight computer later this year, the X-48B will continue a new phase of flights tests that are to focus on additional parameter identification investigations. In addition, the team managing the project is also preparing a second hybrid wing body aircraft: the X-48C for future flight tests, which is intended to have a lower noise profile.
A second phase of flight tests with the X-48B was to begin in September 2010. Afterwards the second X-48B will be modified into the X-48C for flight tests in 2011. The X-48C will have its vertical stabilisers moved inboard on either side of the engines, and its fuselage extended aft, both in an attempt to reduce the aircraft's noise profile, and will be powered by two JetCat turbines, each producing 80 pounds-force (0.36 kN) of thrust.
The initial planned 35 ft (10.7 m) wide version. It was canceled before manufacture.
Two 8.5% scale aircraft that have been used for flight testing.
A modified version of the X-48B.
Wingspan: 20 ft 5 in (6.22 m)
Wing area: 100.5 sq ft (9.34 m2)
Aspect ratio: 4.1
Gross weight: 500 lb (227 kg)
Powerplant: 3 × JetCat P200 turbojet, 52 lbf (0.23 kN) thrust each
Maximum speed: 136 mph; 219 km/h (118 kn)
Endurance: 40 minutes
Service ceiling: 10,000 ft (3,048 m)