Forget the fuselage:
Researchers make progress on flying wing
BY DAVID F. SALISBURY
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.
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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. SR
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