7/29/97
CONTACT: David F. Salisbury, News Service (415) 725-1944;
e-mail: david.salisbury@stanford.edu
Flying wings are an old idea whose time may be fast approaching.
The idea of forgetting about the fuselage and simply making a wing large enough to carry crew and passengers was experimented with for military purposes during World War II. But no one ever tried to make one into a passenger aircraft.
But that is what McDonnell Douglas, the National Aeronautics and Space Administration and a group of researchers in Stanford's aeronautics and astronautics department have in mind with a design called the blended wing body. The wedge-shaped super jumbo jet has a wingspan 67 feet wider than the Boeing 747-400 and could carry as many as 800 passengers on long-distance flights more cheaply and efficiently than the current generation of jumbo jets. Rather than being a separate cylinder, the aircraft's passenger section is blended smoothly into the aircraft's swept-back wings.
The concept came a step closer to reality on Tuesday, July 29, when a 17-foot remotely piloted model of the blended wing body, designed and built at Stanford's Flight Research Laboratory, successfully negotiated its maiden flight at El Mirage Dry Lake in California's Mojave Desert. Stanford researchers included postdoctoral research affiliate Ben Tigner; graduate students Mark Meyer and Michael Holden; and Associate Professor Ilan Kroo.
The blended wing body concept has the potential to be a very low-drag, high-lift, low-weight commercial transport. But flying wing designs tend to be difficult to stabilize and control without using techniques that substantially increase the aircraft's drag and fuel consumption.
Exploring the new design's flying characteristics and testing flight control concepts that will allow such an aircraft to fly safely and efficiently is the primary purpose of the 6 percent scale model aircraft tests. The heavily instrumented model also will be used to test the design's low-speed capabilities, as well how it performs when flying with its nose pitched up or down at steep angles.
The model, with a 17-foot wingspan, weighs 120 pounds and is powered by two 4.5 horsepower engines that can propel it at speeds up to 65 miles per hour. It carries a flight computer that operates the controls and beams back 10 data channels that record various aspects of the aircraft's performance. It also carries a video camera as a pilot aid.
The test flight is the latest phase in research into the blended wing body concept that has been conducted since 1991 as part of NASA's Advanced Concepts for Aeronautics Program. Extensive computer simulations have been made of the unconventional wing shape, which is extremely thick compared to that required for current jetliners. In addition, a high-speed model with a wing span of nearly 5 feet has been tested in NASA Langley Research Center's transonic wind tunnel. Researchers at the University of Southern California and the University of Florida are studying other aspects of the design.
In addition to the blended wing body's flight characteristics, some other technical problems must be resolved before it is ready for commercialization, according to NASA. Pressurization of the arrowhead-shaped passenger area requires the use of advanced composite materials and new techniques that must be tested. The design buries three advanced jet engines at the back of the central section of the wing where it is thickest. This configuration reduces drag over the conventional approach that hangs the engines below the wing where they take in freely streaming air, but tests are required to ensure that the level of turbulence in the engine inlets can be kept to acceptably low levels.
"With many applications for [blended wing body] technology envisioned from commercial transports to cargo aircraft, to very-long-range military airlifters the technology required for the [blended wing body] may be the key to realizing continued increases in aircraft size and efficiency," says a recent NASA fact sheet.
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By David F. Salisbury