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Wing design reduces wake
turbulence
By Sarah Yang
Adding triangular flaps to the design of aircraft wings dramatically
reduces the turbulence generated in a plane's wake, according
to Berkeley mechanical engineer Ömer Savas, whose recent
research may lead to improvements in both flight safety and airport
capacity.
Wake turbulence, or wake vortices, may have played a role in the
American Airlines Flight 587 crash that killed 265 people last
November 12, according to crash investigators. The tail fin of
the Airbus A300 jet sheared off after the pilots struggled against
the wake turbulence left by a Boeing 747 that had taken off less
than two minutes earlier.
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| Savas conducts wind-tunnel
and water-tank experiments to gather data on wake vortices.
Peg Skorpinski photo |
Savas and former graduate students Jason Ortega and Robert Bristol
have been experimenting with wing designs that would quickly render
wake turbulence harmless after takeoffs and landings. "The
wing we designed could make substantial differences in flight
safety and airport capacity," says Savas. In their bat-like
design, triangular extensions jut out behind each wing, dissipating
wake vortices two to three times faster than traditional wing
designs.
Berkeley recently filed a provisional patent application for the
design using results from Savas' experiments.
Federal regulations require flights to be spaced far enough apart
during takeoff and landing to avoid the potential hazards caused
by wake turbulence. While wake turbulence alone probably couldn't
have caused the crash of Flight 587 in New York, "turbulence
in combination with a possible structural problem in the tail
fin could be devastating," says Savas.
A wake vortex results from the mismatch in speed, direction, and
pressure of air moving above and below a plane's wing. These differences
govern the lift generated during flight. Planes that are large,
heavy, and moving slowly create stronger wake vortices.
Depending upon weather conditions and a plane's speed and size,
the wake vortices can stretch a distance of hundreds of wingspans,
or three to five miles for a commercial aircraft, says Savas.
"In addition to improving safety, cutting the distance that
the wake vortex remains coherent would allow planes to take off
and land closer in time together without compromising safety,"
says Savas. "That leads to more efficient use of runway capacity,
a major problem at congested airports around the country."
Savas is currently working on a pilot program with scientists
at NASA Ames Research Center to incorporate the triangular-flapped
wings in aircraft designs. He notes that commercial jets have
not gone through a significant design change since the Boeing
707 began rolling down the runways in the 1950s. "Maybe it's
time for something new," he says.
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