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`SMART WINGS’ MAY CUT THE COST OF AIR TRAVEL

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Peering out a jetliner window, a passenger gazing at the massive, motionless wings that easily slice the air sees a marvel of grace and efficiency.

Sleek as airplane wings are, however, they are not aerodynamic enough. The invisible swirling pressure of their 400-mile-an-hour charge through the wind burns up fuel, a major factor in ticket prices.Now, in a breakthrough in micromachining, which takes big machine actions for manipulating light, fluids and air and shrinks them to minuscule levels, research engineers have demonstrated that thousands of pinhead-size silicon flaps can help redirect air flows around the wings of big jets, offering huge gains in efficiency and maneuverability.

Within two years, the "micro-flaps" will be tested on big military jets. Several years after that, industry experts say, "smart wing" systems using the flaps may be employed for the first time to reduce the gas-guzzling drag on airliner wings, to back up steering controls that may break, or to help keep dangerous ice from forming on wings.

"I'm surprised by it myself," says Chih-Ming Ho, a lead research engineer overseeing two government-backed projects at the University of California at Los Angeles, as he toggles a switch on an electromagnet hooked to a two-inch-long strip of silicon micromachines. They look like a row of computer chips. But as the magnetic forces pulse into them, dozens of millimeter-wide flaps, on the top layer of the strip, start popping up and down, just as they would along the leading edge of aircraft wings.

Aircraft engineers have known for years that the whirling columns of air breaking over aircraft wings originate from tiny points on the wings' leading edge. It is those bursts of air, or "vortexes," that help determine the pressures on a wing and affect its movement. But there has been no practical way to control those forces until recent strides were made in micro-machine technology.

"Small things usually control other small things," Prof. Ho says, but his research shows that micromachines can affect large, high-energy forces.

In a special chamber inside a huge funnel-shaped wind tunnel in UCLA's Engineering Lab One, Prof. Ho's team affixes the microflaps to small, triangular plastic "planes," then buffets them with winds moving 150 feet a second, or about Mach 1.5. Nearby, research aides have nearly assembled a five-foot-long fiberglass plane that in about a month will test the flaps in flight at 140 miles an hour - the first in a series of ever-larger models planned for flight tests during the next year.

Already, the wind-tunnel tests have shown that the movement of air, and thus the wing, can be controlled by altering the spin of the twists of wind at their minuscule points of origin.

For military engineers, the microflaps mean wedge-shaped "delta-wing" fighter planes can be designed without so many moving parts, eliminating wing flaps and even vertical tail sections, while making the jets much lighter and more maneuverable.

On passenger airliners, the little flaps eventually may be used in much the same way, altering and smoothing the thousands of wormlike, random whirlwinds of air that create turbulence over the wings and cause engines to work harder. As the air moves more evenly over the wing, Dr. Ho suggests, even a 1 percent reduction in the "drag" of air ultimately could yield a 20 percent increase in airline profits. The tremendous fuel savings would be a boon for airlines' slim profits and could result in lower fares.

Aircraft designers are intrigued. "This is pretty revolutionary," says Jan Tulinius, chief scientist for aircraft research at Rockwell International Corp., one of U.S. industry's principal designers of military and commercial aircraft wings, and a major supplier to big commercial jetmakers such as Boeing Co.

The delta-shaped design of some military aircraft and of next-generation supersonic passenger jets now in development lends itself most naturally to the use of smart wings, Tulinius says. The spirals of air from wings of that shape are large, fewer in number and more predictable. Carefully placed groups of the tiny flaps can be controlled by an onboard computer. As they alter the forces pressing on one wing, they cause it to rise or fall and turn or roll the plane.

Using microflaps to get greater efficiency from the kinds of "swept-wing" designs on commercial airplanes in use today is "farther downstream," Tulinius says, partly because of the complexity of controlling the random, smaller air spirals and turbulence flowing over those types of wings.

Sensors needed to detect all the little twisters already are being designed into the UCLA microflaps, which were produced by a separate team at California Institute of Technology led by Yu-Chong Tai. To enable the flaps to respond quickly to the barrage of small air disturbances, they will be linked by "neural networks" that allow the processing to take place on the wing.