The Blended Wing Body
A Revolutionary Concept in Aircraft Design

At left: Concept painting of BWB aircraft by Bill Kluge, NASA LaRC. Originally painted for cover Aviation Week, 2/7/2000.

NASA is planning to fly one of the most revolutionary aircraft concepts of recent decades to explore its potential as a future configuration for passenger and airfreight transportation.

The design is called the Blended Wing Body (BWB). The BWB is a hybrid shape that mainly resembles a flying wing, but also incorporates some features of a conventional airliner. The futuristic airframe is a unique merger of efficient high-lift wings and a wide airfoil-shaped body, causing the entire aircraft to generate lift and minimize drag, thereby increasing fuel economy. Passenger and cargo areas are located within the center body portion of the aircraft.

NASA and industry studies suggest that a large commercial BWB aircraft could be developed to carry 800 or more passengers; however, recent studies have focused on vehicles in the 450-passenger class. Because of its efficient configuration, the BWB would consume 20 percent less fuel than jetliners of today, while cruising at high subsonic speeds on flights of up to 7,000 nautical miles. An aircraft of this type would have a wing span slightly wider than a Boeing 747 and could operate from existing airport terminals.

NASA is developing a 35-foot wing span, remotely-piloted research aircraft based on the BWB design. The vehicle is called the Blended Wing Body-Low-Speed Vehicle (BWB-LSV). The primary goals of the test and research project are to study the flight and handling characteristics of the BWB design, match the vehicle's performance with engineering predictions based on computer and wind tunnel studies, develop and evaluate digital flight control algorithms, and assess the integration of the propulsion system to the airframe.

The Blended Wing Body research project is a partnership between NASA's Aerospace Vehicle Systems Technology Program and the Boeing Company. Funding and workforce for the project comes from both sources. In addition, the Flight Research Base Program at Dryden Flight Research Center, Edwards, Calif., and Old Dominion University, Norfolk, Va., are partners in the testing phase of this project.

Over the past several years, wind tunnel and free-flight tests have been conducted to study certain aerodynamic characteristics of the BWB design. At the NASA Langley Research Center in Hampton, Va., researchers tested three wind tunnel models of the BWB-LSV to evaluate the design's stability and control and spin/tumble characteristics. Data obtained during these tests were used to develop flight control laws and helped to define the flight research program. The researchers will incorporate all of the wind-tunnel (and later flight) data into simulations of the BWB-LSV and a full-scale BWB to evaluate the plane's flying characteristics.

The BWB-LSV is a 14%-scale version of the 450-passenger study aircraft. Built primarily of composite materials and weighing about 2,500 lb., the platform features a wide arrowhead-like body that blends into tapered wings swept aft. Flight control surfaces, or elevons, span the trailing edges of the wings while the rudders are located in winglets on each wing tip.

Three 240-lb thrust turbojet engines, from Williams International Corporation, Walled Lake, Mich., will be mounted on low aerodynamic pylons across the rear portion of the center body. All three engines will operate from a single fuel tank located near the vehicle's center of gravity. The maximum speed of the BWB-LSV will be about 165 mph.

Electric actuators in the flight control system link the exterior control surfaces with a central digital fly-by-wire flight control computer carried in the center body of the aircraft. The aircraft will be flown by a NASA research pilot sitting at a cockpit station in the remotely piloted vehicle (RPV) facility at the NASA Dryden Flight Research Center. Instruments and displays in the RPV cockpit will provide the pilot with the same systems and performance data commonly displayed in conventional research aircraft cockpits.

Two small video cameras will be installed on the BWB-LSV. One, behind the mock cockpit windscreen, presents a forward-looking view on a large video screen in the RPV cockpit station. The NASA project pilot will use this view, along with the cockpit instrument array, to fly the vehicle. The second camera will be mounted atop the rearward portion of the center body, to view external areas of the vehicle during flight.

Numerous sensors installed throughout the vehicle will measure aerodynamic loads, air pressures, temperatures, engine performance, and other important test and research parameters during each flight. Data will be automatically transmitted to the Dryden mission control center and monitored during flight by project engineers and other members of the test team.

A spin recovery system built into the test aircraft will allow the vehicle to be flown to its maximum angle of attack and as slow as its stall speed. The system will be used to deploy a parachute if the vehicle begins an uncontrollable descent, such as an unrecoverable spin. The parachute attach line would be cut, separating the vehicle from the canopy as soon as stabilized flight could be resumed.

Construction of the BWB-LSV began in early 2000 and is scheduled for completion in late 2002. Integration and ground testing of the vehicle will continue through 2003, followed by the test flight program. When assembly of the BWB-LSV is completed at the Langley Research Center, it will undergo three months of wind tunnel testing at the Old Dominion University (ODU) Full-Scale Wind Tunnel Facility in Hampton, Va.

Research in ODU's massive 30 by 60-foot wind tunnel will include operating the engines and the external flight control surfaces at various air speeds. Data from this research will give engineers and designers a better understanding of the aerodynamics associated with the BWB's unique design prior to flight, as well as a unique opportunity to test the same vehicle on the ground and in flight.

At the conclusion of the wind tunnel research the Low-Speed Vehicle will be transferred to Dryden where it will be readied for its first flight, scheduled to take place in 2004.

Preflight work at Dryden will include final systems integration, ground vibration tests to investigate the design's structural modes, and electromagnetic tests to assure that it can be remotely operated without causing electronic interference to aircraft systems. The aircraft will undergo a final combined systems test and taxi testing prior to the actual flight research.

The current flight schedule calls for approximately 30 to 50 one-hour flights over a period of a year. Like most flight test and research programs, the schedule begins with benign operations and increases in complexity as flight experience is gained.

All flying of the remotely piloted vehicle will be in restricted airspace over the Dryden complex at altitudes up to 10,000 ft.

The flight tests will use two sets of flight control laws. One is a basic set that will be used for most of the research flying, developed jointly by Langley and Dryden. The other set of flight control laws will help investigate specific research and high-risk test points. If the reaction of the vehicle is unacceptable during a high-risk flight, control of the vehicle will revert to the basic set of control laws. These procedures are designed to ensure safe flight operations.

The NASA BWB Project is managed by Langley Research Center, where the BWB-LSV is being designed and built. Langley also leads project research.

The BWB-LSV shape, called the outer mold line, was developed by The Boeing Phantom Works, Long Beach, Calif., which is also developing the research flight control laws that will be used for specific research test points.

Old Dominion University will be responsible for performing the planned wind tunnel research of the BWB-LSV aircraft.

The Dryden Flight Research Center is currently responsible for the BWB-LSV flight tests and operations.

Caption: 3%-Scale BWB-LSV Langley 14x22 Wind Tunnel Model.