Spread-Wing Jet

Modern jet airliners have a monstrous hunger for real estate. Their take-offs and landings are so fast that they eat up runways two miles long. But Seattle's Boeing Aircraft Co. is getting ready to put the big birds on a skimpy diet. Boeing's latest passenger plane, the three-jet 727, will be fitted with special wing flaps designed to get in and out of smallish airports with ease.

The use of flaps to aid a plane on take-offs and landings is an old technique, but few wings have ever had as many appendages as are planned for the 727. As the swift airliner slows for landing, its thin, swept-back wings will grow like opening umbrellas. On their leading edges small "Kreuger flaps" will tilt outward, making the wing effectively thicker and giving it extra lift. Simultaneously, a strange structure will slide out of the wing's trailing edge. Segmented flaps will move backward and downward, deflecting the air stream sharply and adding still more lift. Filling the angle between wing and fuselage, the huge flaps will turn the wing into an almost perfect triangle with 25% more area than it has in high-speed flight and three times its normal lift.

The expandable wing has been tested only on the old brown-and-yellow four-jet 707 that Boeing uses as a guinea pig for new devices, but it has worked so well that Boeing engineers are making startling predictions for the 727. It will "come over the fence," say the engineers, at about 130 m.p.h., and will touch down at 115 m.p.h. This is about 20% slower than present jetliners and almost as slow as old-fashioned prop-driven planes. Instead of requiring two-mile runways, says Boeing, the 727, which can cruise for 1,700 miles at speeds up to 600 m.p.h., will spread its expanded wings on small airfields and will not require vast jetports far from the cities they serve.

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